Specific Question - ARP Head Studs on 2.7 Magnesium case - Insane?

[Lapkritis]

Good Morning Walt,

Thanks for the response here. I guess the discoloration of the area threw me off given the aesthetic treatment the rest of the case was given. Perhaps there is an explanation for why the same was not done for this machined area such as the machining step coming after the aesthetic treatment.

I am aware of the early 7R cases and the attributed strength being partially due to the proximity of the head stud as much further from the smaller diameter 92mm spigot...

Looking at the information Bruce provided to us in his manual I also see there were model years without external oil coolers and without case squirters from this range of magnesium cases that are relatively trouble free as you mention. The case squirters were not introduced into production until 1971. The first mag cases were 1968. The first external oil cooler was in the s in 1969.

Seems pretty safe to say if those original cases with steel are fine without savers then the later such as mine would benefit from an iron cylinder retrofit as well especially given the cooling tricks we've since learned. I'm curious if Henry has tried this on the 2.7 and await his response.



-Andrew

[Henry Schmidt]

No Andrew, I didn't use 90 mm cast iron cylinders because I learned from earlier experiences with cast iron cylinders (2.2 & 2.4) just like the factory did.
The earlier cast iron cylinders were never used to produce an engine that generated real horse power. More horse power always means more heat.
All of the early engines with cast iron cylinders were limited in horse power to less than or around 140.
What we discovered (I assume the factory as well) was that most of the cylinder heat is concentrated 20 to 30 mm from the head and with cast iron incapable of dissipating the heat efficiently, cylinder head temps went up. Since the heads are primarily cooled by air, the addition of the external cooler had little effect.
JB racing cast cylinders (a nice product BTW) uses aluminum fins to cool the cast liner thus limiting the heat build up.
Considering the Porsche is a performance automobile designed for an exhilarating driving experience, we always felt 140 horse power in the flat six was droll and undeserving of a place in the rear of one of these gems.
So thank you but you can keep your million mile motor and I'll keep helping people build the heart pounding performance the "real" Porsche enthusiast seeks on a budget they can afford.

[Lapkritis]

So I take it as a "no" that you have no idea what the true temperatures are. The irony of your conjecture statements earlier in the thread aren't lost on me here. You don't have data and you don't know what you're talking about. You will learn something here if you stay tuned. You haven't done this before and you do not know what will happen; neither do I but the data predicts a certain result.

Tell me the answer to these rhetorical questions. Did the early 2.2l / 2.4l engines have case squirters? What about external oil coolers? What about the fan design? What about turbo valve covers? What about deflector tins?

You keep building those 2yr warranty engines on 40yr old cars. I wouldn't consider the warranty of significant value unless I were planning to deliver pizzas or run a 24hr taxi service for those 2yrs. I want confidence beyond 2yrs. I will dyno the cast iron cylinder result here.

[Henry Schmidt]

Originally Posted by Lapkritis

So I take it as a "no" that you have no idea what the true temperatures are. The irony of your conjecture statements earlier in the thread aren't lost on me here. You don't have data and you don't know what you're talking about. You will learn something here if you stay tuned. You haven't done this before and you do not know what will happen; neither do I but the data predicts a certain result.

Tell me the answer to these rhetorical questions. Did the early 2.2l / 2.4l engines have case squirters? What about external oil coolers? What about the fan design? What about turbo valve covers? What about deflector tins?

You keep building those 2yr warranty engines on 40yr old cars. I wouldn't consider the warranty of significant value unless I were planning to deliver pizzas or run a 24hr taxi service for those 2yrs. I want confidence beyond 2yrs. I will dyno the cast iron cylinder result here.

Your responses are bordering on tedious. You've dug you heel in and determined to prove history wrong and at this point, you're looking kind of silly.

There is no reason to believe that the results from an engine with 90/92 mm cylinders would be significantly difference than an 84 mm cylinder given the same material other than to predict that the negative effects would be more pronounced. The larger bore diameter results in even less area for cooling fins.

The answers to the questions you ask are well known to most Porsche engine builders.

Did the early 2.2l / 2.4l engines have case squirters? Yes. Porsche built engines with cast iron cylinders incorporating piston sqirters as did I.

What about external oil coolers? external cooler were available on early cars plus we added then to rally and race cars. Porsche regularly installed coolers on production cars with engines producing more than 160hp back then.


What about the fan design? Fan design has remained basically the same.
Pulley diameters have changed but fan speeds are a compromise. Too fast at low engine speeds means cavitation (super sonic tips) at higher engine rpm. These high tip speeds mean poor blade function and excessive noise. If you search this forum you will find a thread where I post all the fan and pulley diameters and their effect on CFM and noise related to ducted fans.

What about turbo valve covers? Turbo valve covers offer no significant cooling advantage. The ribs on the cover are for reinforcement not cooling.

What about deflector tins? Cooling tin has been discussed since the 906 days.
Full sized (not trimmed) actually offer better cooling on the cast iron cylinder.
We actually reproduce the 906 cooling tin so that the original full finned 906 style cylinders (which we also reproduce) can be cooled properly.

Despite your "you don't know what you're talking about" comment we have probably done as much real world development work on these engine as anyone else on the planet.
I would ask you: how many professional or DIY engine builders are calling and emailing you for advise / brain-stroming on unusual and often obscure technical problems? I receive some 200 a day from people who have confidence in my opinion as well as confidence in the engines I build. I don't get these requests because I have all the answers or even the best answers but because I offer honest answers backed by years of dedication to Porsche excellence.

As for your obnoxious comment about my warranty: I believe it's the best in the business and shows my confidence in our product. I put my reputation and money behind every product I build. Because we warranty our work, we seek the best solution for every problem. Best being a compromise between performance and cost.

[Lapkritis]

Originally Posted by Henry Schmidt

Your responses are bordering on tedious. You've dug you heel in and determined to prove history wrong and at this point, you're looking kind of silly.

Pardon me, I was under the impression we were finally getting somewhere to a point that you would converse rather than lecture. Apparently you're not ready to accept a learning opportunity yet and seek to discredit others still. That's fine, you can continue to do things the way you want and ignore progress. Best of luck to your magnesium case customers. I definitely will not be of those eventual victims I mean customers.

There is no reason to believe that the results from an engine with 90/92 mm cylinders would be significantly difference than an 84 mm cylinder given the same material other than to predict that the negative effects would be more pronounced.

Yes, there is. It's okay that you disagree, you aren't open to learning anything so you really believe this. There are plenty of applied cooling methods and some you have no idea about. You have certain building habits and a confidence that what you produce is the best. Good for you. I think you leave meat on the bone for improvement that the community could further benefit from. That's my belief. I'm entitled to it.

The larger bore diameter results in even less area for cooling fins.


The answers to the questions you ask are well known to most Porsche engine builders.

Did the early 2.2l / 2.4l engines have case squirters? Yes. Porsche built engines with cast iron cylinders incorporating piston sqirters as did I.

Duh. We just gave the dates but thanks for playing. There were several years without these squirters was my point.

What about external oil coolers? external cooler were available on early cars plus we added then to rally and race cars. Porsche regularly installed coolers on production cars with engines producing more than 160hp back then.

Again, we gave dates. Are you aware of the definition of rhetorical? My questions might seem less tedious of you did. 160hp is approaching stock 2.7L area... I can't tell if you're still really arguing against the cast iron cylinders with this data point.

What about the fan design?

Fan design has remained basically the same.

Wrong. So many fan types ...and you even state so below.

Pulley diameters have changed but fan speeds are a compromise. Too fast at low engine speeds means cavitation (super sonic tips) at higher engine rpm. These high tip speeds mean poor blade function and excessive noise. If you search this forum you will find a thread where I post all the fan and pulley diameters and their effect on CFM and noise related to ducted fans.

What about turbo valve covers? Turbo valve covers offer no significant cooling advantage. The ribs on the cover are for reinforcement not cooling.

Significant... I suppose it was significant enough to have them made. Otherwise just continue with the same as normally aspirated.

What about deflector tins? Cooling tin has been discussed since the 906 days.
Full sized (not trimmed) actually offer better cooling on the cast iron cylinder.
We actually reproduce the 906 cooling tin so that the original full finned 906 style cylinders (which we also reproduce) can be cooled properly.

Any more product plugs you want to squeeze in? Maybe include pricing each time you mention one. Would save time for people that read these long responses from emailing you.

Despite your "you don't know what you're talking about" comment we have probably done as much real world development work on these engine as anyone else on the planet.

All that experience doing the same thing. That's more practice, don't kid yourself or others. Experience means you have tried and failed and learned. You haven't tried and failed at what I propose as a solution. Therefore you still do not know what you're talking about. Do you really think cast iron won't make power or be able to cool with simple or existing modifications? Time for a wager?

I would ask you: how many professional or DIY engine builders are calling and emailing you for advise / brain-stroming on unusual and often obscure technical problems?

This is completely irrelevant. The topic isn't how many cronies you have. You could be the head of development at Porsche and we could be having the same discussion. I don't expect they would be as condescending as you demonstrate here.

I

receive some 200 a day from people who have confidence in my opinion as well as confidence in the engines I build.

As for your obnoxious comment about my warranty: I believe it's the best in the business and shows my confidence in our product. I put my reputation and money behind every product I build. Because we warranty our work, we seek the best solution for every problem. Best being a compromise between performance and cost.

Obnoxious? I'm quite serious. Do you not recommend your engines for such service? 2yrs is virtually inconsequential for cars that are driven rarely as many are. The previous owner of my car traveled 500 miles in 8 years.

[911 tweaks]

andrerw...cut the s^it here & interact w/ henry & others to discuss your questions...
You are soon to have many folks skip this thread & let you figure this out on your own...
Sure appears that you have a drum to beat and are not wanting to discuss your q here...
It is ok to disagree with a point(s) someone makes...just move on from that point and continue to discuss the subject w/o creating friction to hopefully fully discuss your q......
So many threads on pelican start out well & go to s^it w/o the topic coming to a full discussion of it...

[Lapkritis]

I'm sorry for feeding the troll.

-Andrew

[Walt Fricke]

Andrew

The essence of making a forum useful is great restraint when it comes to opinions, and even greater restraint when it comes to getting personal. All of us vary somewhat in our ability to adhere to these goals, but it is worth keeping them in mind.

If Henry says he does such and such because he's done it successfully on many motors, I believe him. That may not satisfy my desire for quantification or some other tie to a form of engineering logic, but at least I know that X is most likely going to work. The fact that Henry (or anyone else) doesn't like Y is more of a datum point where there are countervailing views. For instance, Steve Weiner likes the 993 RS or whatnot full threaded Dilivar head studs. Steve has built some pretty potent and strong race motors for customers. Henry believes they are not good to use. Two different forum personalities, two different opinions from guys who get paid to build good motors for other people.

Guys building race motors (or wanting to pull well more than stock power out of a street motor) use Nikasil cylinders, or they use something like the JR iron sleeved cylinders - which are pretty much like what Porsche did with the Birals. Few are likely to be interested in seeing how well or poorly all iron cylinders will work outside of the realm of the T motors, perhaps because they simply cannot work as well as the other options in dealing with the heat. Yes, they might deal with differential thermal expansion coefficients between jug and stud, but there are plenty of ways to deal effectively with stud/case issues.

Now you are interested, which is fine as an abstract matter, but in this case Henry actually did quantify his views - he had measured temperatures on the smaller bore iron cylinders, and didn't like what he found if the intention was to raise the HP and so create more heat. And his logic in extrapolating this to larger bores seems pretty convincing.

And head cooling is pretty important. Porsche found that it couldn't keep the head temps viable with 4 valves per cylinder without water cooling. The change from air and 2 valves to water and 4 has led to an increase in attainable race motor power per liter from 110 hp to 170 with the current DFI motors.

Now none of this should discourage you from trying iron cylinders, and measuring things, and so on. Maybe conventional wisdom and weight of authority have it wrong, and there will be a boom in finding junkyard T iron cylinders. I once had a 2.5 race motor built (originally) by none other than Grady Clay. It had 88mm iron cylinders with a 66mm crank. Pretty peppy motor, and the rather small valved/ported heads didn't seem to be in distress. But it got sacrificed for its sand cast case for a 2.7, which was a lot peppier yet. I've still got the Ps, Cs, and heads, which I suppose I ought to try to sell as I'm not going to use them.

[Lapkritis]

Originally Posted by 911 tweaks

andrerw...cut the s^it here & interact w/ henry & others to discuss your questions...
You are soon to have many folks skip this thread & let you figure this out on your own...
Sure appears that you have a drum to beat and are not wanting to discuss your q here...
It is ok to disagree with a point(s) someone makes...just move on from that point and continue to discuss the subject w/o creating friction to hopefully fully discuss your q......
So many threads on pelican start out well & go to s^it w/o the topic coming to a full discussion of it...

Tweaks, the above conversation between Henry and I is interaction. The original question of running ARP hardware on a magnesium case has been answered and new questions have been raised. It would be very unwise to run a non-dilavar fastener especially ARP with an aluminum jug on a magnesium case. Failure is practically guaranteed. You could run casesavers and hope for the best but the data shows extreme pressures will be applied to the case threads. Consider this fair warning to magnesium case owners out there with science to back it up.

[Lapkritis]

Originally Posted by Walt Fricke

Andrew

The essence of making a forum useful is great restraint when it comes to opinions, and even greater restraint when it comes to getting personal. All of us vary somewhat in our ability to adhere to these goals, but it is worth keeping them in mind.

Walt, I appreciate your composed response. Considering I may be moving into your neck of the woods again soon for work may mean we have an opportunity to meet in person and share a couple pints. I understand restraint on the internet is wise but there also comes a point where vailed insults such as those paid to me by Henry should be met head-on and discussed openly. I've let them slide to this point and he continues to bait and press. The nail that stands up shall be hammered down and so it is with words here dealing with Henry and his unprofessional conduct. Suggesting I'm cheap, not a "real" Porsche enthusiast etc... enough is enough. I understand he's sensitive to people suggesting alternative methods but that is his problem to deal with privately with himself and not by going after those suggesting those alternative methods. The proper response from him would have bee something along the lines of: "My experience tells me that probably won't work out but good luck to you. I'm interested to hear how it works out for you." What he has posted thus far in response is nowhere near that... it's all about what he's done, how long he's been doing it, what he sells for services, how popular he is, how successful he is etc etc etc. Seriously. This has started to turn into a Supertec advertisement thread not a discussion of ARP and magnesium cases.

If Henry says he does such and such because he's done it successfully on many motors, I believe him. That may not satisfy my desire for quantification or some other tie to a form of engineering logic, but at least I know that X is most likely going to work. The fact that Henry (or anyone else) doesn't like Y is more of a datum point where there are countervailing views. For instance, Steve Weiner likes the 993 RS or whatnot full threaded Dilivar head studs. Steve has built some pretty potent and strong race motors for customers. Henry believes they are not good to use. Two different forum personalities, two different opinions from guys who get paid to build good motors for other people.

I believe this is where we see who is a consumate professional and who lacks restraint to conduct themselves in a manner representative of a great company. If you're truly great at what you do then your body of work speaks for itself. You don't need to jump in and hold the pen for everyone else. To attack a DIY enthusiast unprovoked is not behavior I've seen at any point in my 16yrs of enjoying the automotive hobby. I don't believe it is representative of the whole of the Porsche community but to accept it as normal and justified is indicative of perversion of thought. If you don't like what I'm drawing on my pad then who cares? It's my project. If you don't have something nice to say then don't say anything at all. (these are words for Henry, not you so much Walt).

Guys building race motors (or wanting to pull well more than stock power out of a street motor) use Nikasil cylinders, or they use something like the JR iron sleeved cylinders - which are pretty much like what Porsche did with the Birals.

The original recipe isn't the topic of discussion here. I have the nikasil rs bits in perfect condition; I know they're what people normally do and is the most popular way to go especially with the aftermarket cams of higher lift. I'm personally done with them - I'm opting out based upon the magnesium case and the thermal expansion of the aluminum jug. I trust math and published data on the materials more than hoping a case saver might or probably should hold... no data just hope. If fatigue of the case material weren't an issue then we probably wouldn't be having this discussion now... the material around the casesavers will fatigue eventually. I would only consider running the rs pistons with a custom matched set of JB type steel/billet nikasil coated with proper wall clearance. I would not use the rs jugs at all with the magnesium case because to do so would mean using Dilaver fastener to match the expansion rate... and I don't trust the Dilaver give the embrittlement failures.

Few are likely to be interested in seeing how well or poorly all iron cylinders will work outside of the realm of the T motors, perhaps because they simply cannot work as well as the other options in dealing with the heat.

As grown men we may discuss pedigree without blushing. The fact that the jugs I'm testing are Chinese is the elephant in the room. I'm personally not thrilled about that fact either but reasonable alternatives do not exist. $3k jugs on a $3k engine to begin with doesn't add up. It won't matter that I have the bores trued and honed and the critical dimensions confirmed/matched by my rural American machinist who builds hundreds of engines each winter for the local circle track teams. The fact is they're not as elite as a German domestic product or specifically Porsche genuine parts. I don't expect them to sell and I don't care if they do; I don't have any skin in the game as a hobbyist as my meals are paid for by a day job. Anyone with a brain and who understands the thermal expansion forces we've laid out here in basic calculations may feel inclined to follow my example if things work out. Blissfully ignorant with aluminum cylinders and steel studs on a magnesium case is a recipe for far fewer happy enthusiasts.

[Lapkritis]

Yes, they might deal with differential thermal expansion coefficients between jug and stud, but there are plenty of ways to deal effectively with stud/case issues.

Other than case savers, simply never driving the car or thermal loading the entire engine when stored such as Formula 1 teams do, what are these other ways? Praying and crossing fingers doesn't count. Neither do rabbits foot key chains. Or Horse shoes.

Now you are interested, which is fine as an abstract matter, but in this case Henry actually did quantify his views - he had measured temperatures on the smaller bore iron cylinders,

Show me the data. Simply saying 20-30% near the top of the cylinder is hotter than the rest is like saying that the fridge is colder in the freezer half. Of course it is hotter up there as that is where the flame is. Such a statement is not a measurement. I'm sure there's plenty of folks with running cars at the track. Put an infrared thermometer on an aluminum jug and aluminum head at a specific point and report back with the temperatures. Ideally, take pictures or video to increase credibility. I will do the same with my project as I think that everyone will learn something rather than trusting "once upon a time" stories.

and didn't like what he found if the intention was to raise the HP and so create more heat. And his logic in extrapolating this to larger bores seems pretty convincing.

Logic is a tricky thing as is extrapolating. Consider for a moment what happens when you run high hp on aluminum cylinders. The same flame temperature is present and the same EGT flows through the ports of the head. The difference is the aluminum cylinders warp before iron or steel would. They had to add a liner to increase strength. In HP terms, Nikasil is not a significant power adder... a turbo charger is a power adder. More on this later... essentially what I want to open your mind to is outside the restrictive box of what you've been advised by engine builders and folks for years. Sure, lots of builders including Henry have done a great job to this point. If Steve Jobs worked on Porsche engines... do you think he would have stopped with the fastener/case saver? Of course not. If he did we would still be talking on bag phones.

And head cooling is pretty important. Porsche found that it couldn't keep the head temps viable with 4 valves per cylinder without water cooling. The change from air and 2 valves to water and 4 has led to an increase in attainable race motor power per liter from 110 hp to 170 with the current DFI motors.

I'm afraid that is a different topic. We don't know the cylinder head temps for this application yet but we will this summer and that I promise you. I don't have anything to hide; I plan to run the car essentially in stock form with the billet upper valve covers and turbo lowers to start; it has SSI headers already. If my monitoring shows head temperatures that exceed comparable stock 911 numbers with aluminum cylinders then I will be milling all 4 valve covers flat and welding on 2" tall heat sink blade over the entire cover before retesting. If tests still show unsatisfactory CHT then I will add CO2 burst circuits to both banks of cylinder heads for WOT operation. I'm not adding neon under glow, big rims or a booming stereo. I understand this may not be to taste for the pedigree folks but what's the point of having a pure bred looking dog if it's dead.

Now none of this should discourage you from trying iron cylinders, and measuring things, and so on. Maybe conventional wisdom and weight of authority have it wrong,

Don't worry about me being discouraged... the exact opposite happens each time someone tells me "new guy thinks he knows something we don't". That game I like to play is NIGYYSOB. I look forward to proving folks wrong; it's how we make progress. Someone always has to be wrong... normally they're smart enough to keep it to themselves to avoid any public embarassment.

It's not that conventional wisdom is wrong. I'm not here to cure cancer or to win the 24hrs of Lemans. I've been around long enough to hear people who've been working in high performance shops for the same amount of time as Henry tell everyone they meet that you can't safely run a long-duration, high lift cam with a turbo charger. It'll blow up they said. It'll flame out from blow-through they said. You'll have high EGT they said. Someone finally had the balls to put one in and it made 150hp more at the same exact boost pressure. It only took 15 years to shatter that myth in the VR6 Turbo community. Retailers were suddenly scrambling to rebrand their high-lift, high-duration all motor cams as turbo cams... Techtonics 288 cams sold out and were commanding a premium of MSRP. That cam set then went 208mph in a street car at the Texas mile. Go figure.

and there will be a boom in finding junkyard T iron cylinders. I once had a 2.5 race motor built (originally) by none other than Grady Clay. It had 88mm iron cylinders with a 66mm crank. Pretty peppy motor, and the rather small valved/ported heads didn't seem to be in distress. But it got sacrificed for its sand cast case for a 2.7, which was a lot peppier yet. I've still got the Ps, Cs, and heads, which I suppose I ought to try to sell as I'm not going to use them.

I don't see any Porsche folks serious about longevity (myself included) buying junkyard cylinders. I'd rather have brand new Chinese and then get my local pal to run them through the shop for a few bucks. They all have Saudi Arabia corsing through their veins anyway... who cares if it works.

[YTNUKLR]

Andrew
I personally am interested in seeing your data.

A few things - where to begin?

on a personal level - I am also a huge VR6 & vintage Porsche fan and interested in a lot of the same engineering stuff you are. I also think that you could be just as much a "straight shooter" and factual/scientific in your analyses as you currently are, while having a more measured tone. I also think you would have a greater positive impact on everyone, and everyone would learn more. You made me debate whether to even address you...but I am too enthusiastic about the technical stuff that I decided to anwyay. I felt it should be mentioned..

to the meat:
you say about engines lasting a long time "when there aren't ridiculous forces yanking the engines apart". That is what is happening. Primarily as a result of revs. I think it's going to be hard to design a sports car engine that lasts a million miles, because although it could be done, it would be an extremely heavy design, and/or, it wouldn't rev very high. These are obviously undesirable sports car attributes.

-regarding studs pulling out of mag cases: I'd love to test this in a lab setting: hypothesis being that steel studs pull out of Mg due to excessive expansion of the aluminum cylinder. I would hypothesize that to an equal or even greater degree, the stud pulls out of the Mg due to the loss of strength of Mg at the temperatures in question (not just the expansion characteristics of the Alu cyl vs. the steel stud). In my mind it seems it would be a compound problem, and in general adequate cooling (of the cylinder and the case) seems to address the issues. Anecdotally, other things (valve guides, rings, etc.) seem to fail before the studs rip out on a properly cooled 2.7 type motor (Mag/Nikasil/Steel studs).

You are demanding data and a scientific approach but you say things like, "It would be very unwise to run a non-dilavar fastener especially ARP with an aluminum jug on a magnesium case. Failure is practically guaranteed. " Where is this data?

Another thought: this is a hobby, for fun, ... there may not be data for every conceivable thing. Maybe there was data but it's in some file drawer or shredder in Zuffenhausen. Maybe it's hard to obtain data. That doesn't mean anecdotal/experiential/qualitative information is irrelevant. People have been messing about with these things for 50 + years or even 100+ years if you consider air-cooled internal combustion engines in general...

-Logic and extrapolation are perfectly valid for a given domain. Ie. if you are making 20hp per cylinder and the cylinder is getting too hot, if you make 30hp in the same volume, it is definitely going to be too hot. The domain is the same, so logic and extrapolation seems perfectly valid. Or did I miss some finer point of philosophy, a hypothetical alternative universe where H2O is called XYZ , and Logic doesn't apply..?

-everything will fatigue "eventually". Just as "we are all dead in the long-term". The trick is in making this work long enough that it accomplishes what we want it to (whatever it is that is going to fatigue).

-I would like to hear more about the rural machinist that builds hundreds of circle track motors.

-Aluminum, whether cast or forged and with regards to alloy selection, can have quite different thermal properties. I would venture to guess that the QSC are at the ****ty end of the stick. But I am still interested to learn what you find.

-"The difference is the aluminum cylinders warp before iron or steel would. They had to add a liner to increase strength." What do you mean here? Aluminum cylinders can be just as strong as iron ones, they just have to be thicker. Depending on the required strength, the additional thickness could prevent the aluminum cylinder from being viable. But due to light weight and excellent thermal conductivity, imho it is preferred. By liner do you mean the iron of the biral , or Nikasil? Both were done not to make the cylinder stronger , but to surface finish the bore so that an aluminum piston could ride inside the cylinder without galling/destroying it.

-Original Biral cylinders were iron cylinders with Al fins cast onto them. The JB Racing "Biral" cylinders have an iron sleeve pressed into an aluminum fin part. The result is vastly superior to the originals - which IMHO are worse from a reliability perspective than solid iron cylinders - assuming temps are under control. The aluminum fins have a tendency to delaminate or "expand off" the iron cylinder center under hot conditions.

-finally. Heat is energy. We want heat (to do mechanical work)! You know the racing GT3 motors are running searingly hot inside, on the verge of detonation? Porsche tuned their fuel injection and ignition maps by running these motors ultra-lean with tons of advance to generate failure, just so they could back up a couple notches so it would stay alive right on the ragged edge. That ragged edge is MUCH further with a water-cooled engine vs. an air-cooled one due to the thermal dispersion capabilities of the medium, but the idea is the same. We want the combustion to be as hot as possible, while we want the outside of the cylinder cool! A "perfect" engine would run huge combustion temperatures- enough to perfectly vaporize incoming fuel - and yet wouldn't even require a radiator...

[chris_seven]

I have been trying to suggest for what seems to be years that the reasons studs pull out of Mag Cases is qualitatively quite staightforward.

There is clealry a realtionship between time, temperature and force. and is any one of the treee can be reduced then the result will probably mean that the engine survives.


The Tensile Strength of most Mag Alloys does reduce with temperature. The loss of strength would be linear with temperature to about 200degC when it would start to drop steelpy.

At 150degC the loss of strength would be typically around 15%. Some of the more recently developed alloys used for Military Helicopter Gearbox casings are much better but they wereen't around in the Sixtires/Seventies.

The more significant impact on pull out behaviour would be due to stress relaxation - which is a form of creep behaviour.

When a material is subjected to a continuous force and even moderate temperatures crystal defects can mecome mobile and due to diffusion effets a loss of strength occurs.

The influence of time/temperature/force can be plotted as a 3 Dimensional surface and changes in any one parameter can have a big impact on success or failure of a set of components.


Over long periods of time strengths of materials can be very seriously affected but the 'damage' to the structure would be restricted to those areas being subjected to the highest level of stress.

Clearly managing temperature is significant as there will be a critical temperature below which the thermally activated mechanisms that cause this damage will not operate.

Reducing stress also gives a beneficial result and should allow the engine to survive.

The arguments centre around the best way to achieve the result.

It is quite clear that engines with well managed temperatures and case savers seem to survive even with Aluminium Cylinders,

Early Magnesium engines with Biral or Cast Iron Cylinders also seem to survive even without case savers and with steel studs

The biggest problems seem to occur with Mag Engines, Thermal Reactors, Aluminium Cylinders and Steel Studs.

These engine are the hottest running, have high stresses due to expansion and stud tyoes.

The argument then seems to take on a almost religious aspect.

If we consider the solutions one by one then we should be able to draw some simple conclusions.

1. Case Savers

These parts certainly will reduce the local stresses in the engine case and this will reduce any stress relaxation effects and assist with the case retaining its basic properties.

This seems to me to be a major influence.

2. Cylinders

The lower the expansion of the cylinder the lower the stresses on the the threads the less likely the incidence of failure.

I am sure there are many arguments about cylinders but they cloud the issue of thread failure.

3. Studs

As I have tried to say before the only influence that the stud has to pulling out threads is its coefficient of expansion.

A Dilavar Stud must reduce the stress developed in the threads even when used with a case saver and regardless of the type of cylinder.

If the primary concern is to preserve a Mag Case then a Cast Iron Cylinder, A Case Saver and a Dilavar Stud along with as much cooling as you can bolt on must be the safest bet.

If there are other more important objectives that mean cylinders need to change, for example, then there may be other solutions that are better.

The real trick is, as has been said, to try to use logic and a basic understanding on the engineering and to try to eliminate the contradictions.

It is interesting that we often use 'Porsche's Design Office' to justify some arguments but contradict some of their decisions when they don't suit our case.

Dilavar and its like/dislike is, of course, the classic example.

[Lapkritis]

Originally Posted by YTNUKLR

Andrew
I personally am interested in seeing your data.

A few things - where to begin?

on a personal level - I am also a huge VR6 & vintage Porsche fan and interested in a lot of the same engineering stuff you are. I also think that you could be just as much a "straight shooter" and factual/scientific in your analyses as you currently are, while having a more measured tone. I also think you would have a greater positive impact on everyone, and everyone would learn more. You made me debate whether to even address you...but I am too enthusiastic about the technical stuff that I decided to anwyay. I felt it should be mentioned..

Welcome to the thread Scott. Tone on the internet is an impossible skill to master; I've seen CEO's mess it up royally. It's an imperfect communication medium so we have to deal with the side effects. Nearly everyone who has visited and weighed in has contributed to the topic as you have below which is great. I hope we can keep the thread producing fresh thought; if nothing else comes from the friction perhaps we can stimulate thought. If you want to know more about the vr6 turbo then feel free to PM me to help try to keep this thread on track.

to the meat:
you say about engines lasting a long time "when there aren't ridiculous forces yanking the engines apart". That is what is happening. Primarily as a result of revs.

Interesting take here. I have to conclude that you're trying to say the compression of gases prior to and during ignition are what causes the case to fail? I'm thinking out loud but those forces here are what drive the piston down rotating the crankshaft and cause the engine to run into the next cycle. Only if you had detonation or preignition (misfire of air to fuel mixture in the combustion chamber) while the piston was rising before optimal would the force/energy of the ignition event be transmitted into the piston and/or cylinder head. The fuse in these events tends to be the weakest material present which is the super heated aluminum piston. If you're thinking in terms of normal operating forces then that would be a different brain exercise.

I think it's going to be hard to design a sports car engine that lasts a million miles, because although it could be done, it would be an extremely heavy design, and/or, it wouldn't rev very high. These are obviously undesirable sports car attributes.

I'm restraining from conferring with my colleague, Google. I know there are some extremely high mile examples of air cooled VW and Porsche out there. This weight topic is interesting when you consider relative weight. Sure the cast iron cylinder is heavier than the aluminum. I'll post the exact weight difference when the jugs return from the machine shop. If you're Porsche and you're looking to win a serious race and reduce tire wear/fuel consumption down to the liter then you're not going to use an engine made entirely of cast iron. However, if you're a top fuel racer then a cast iron block filled with cement pumping out 7000HP is fine. Taking it a step further - the magnesium case is remarkably lighter than the aluminum case as learned from Bruce Anderson's book. Want cold AC on that aluminum engine sports car? Guess how much an AC system weighs. Want to retain heaters, CIS injection (laughable system on the Porsche) or put on wider rims and tires?; this is all weight hanging on the rear axle. Many of us have considered trade-offs for comfort and performance. I like my windows to go up and down rather than having fixed lexan. I like heat. I hate racing seats and harnesses. I don't need air conditioning up here. There are a lot of variables for every car. Cast iron cylinders for my specific application won't make a noticable difference. More has been taken out of the car by removing CIS and air conditioning. Now I will have the added insurance of matching the materials on the engine properly. A few extra pounds going back in is by my opinion a small price to pay for keeping that case together and the throbbing aluminum cylinders on the shelf.

-regarding studs pulling out of mag cases: I'd love to test this in a lab setting: hypothesis being that steel studs pull out of Mg due to excessive expansion of the aluminum cylinder. I would hypothesize that to an equal or even greater degree, the stud pulls out of the Mg due to the loss of strength of Mg at the temperatures in question (not just the expansion characteristics of the Alu cyl vs. the steel stud). In my mind it seems it would be a compound problem, and in general adequate cooling (of the cylinder and the case) seems to address the issues. Anecdotally, other things (valve guides, rings, etc.) seem to fail before the studs rip out on a properly cooled 2.7 type motor (Mag/Nikasil/Steel studs).

This would be a good time and I'm sure Porsche ran quite a few similar back in the day. Run them both with salt bath; fiddle with temperature extremes from arctic to Mojave. Sand, dirt, dust, pollen/seeds clogging the cooling fins, heat cycles on each... if I hit the powerball I would fund such a lab.

You are demanding data and a scientific approach but you say things like, "It would be very unwise to run a non-dilavar fastener especially ARP with an aluminum jug on a magnesium case. Failure is practically guaranteed. " Where is this data?

We ran the numbers on the materials in a hypothetical scenario on the first pages here and drew a logical conclusion. We discussed pressures and expansion rates of jug and stud material combinations. It would be interesting to look at historical Porsche data from the dealerships as these failures occured. War stories from the pits aren't the same as a grid of failures v survivors to determine true rates across the US. This would tell us if the warmer climates had a higher failure rate due to more heat than the colder climates. Where the cars were operated primarily would tell a story as well... if you're coastal California then the temperatures are much more mild than the Inland Empire. 50F ambient difference over several years would likely be found to make a difference but the data would confirm it.

Another thought: this is a hobby, for fun, ... there may not be data for every conceivable thing. Maybe there was data but it's in some file drawer or shredder in Zuffenhausen. Maybe it's hard to obtain data. That doesn't mean anecdotal/experiential/qualitative information is irrelevant. People have been messing about with these things for 50 + years or even 100+ years if you consider air-cooled internal combustion engines in general...

Agreed - the goal here is enjoyment. Much of the fun is discovery and using our brains and talking between brains. It becomes less fun when someone says stop using your brains and do it my way because I was here first and everyone listens to me. It goes without saying that there weren't infrared laser thermometers 50yrs ago nore were extruded aluminum heat sinks readily available or compressed gas halo coolers. These infrared thermometers are cheap to obtain and make taking a measurement a non-intrusive 5 second chore now instead of a finding a consenting owner, taking a few hours to fit a sensor and wire it to a gauge. We're in the 21st century with some amazing technologies available to us that allow very quick and precise study of areas that were previously off limits.

[Lapkritis]

-Logic and extrapolation are perfectly valid for a given domain. Ie. if you are making 20hp per cylinder and the cylinder is getting too hot, if you make 30hp in the same volume, it is definitely going to be too hot. The domain is the same, so logic and extrapolation seems perfectly valid. Or did I miss some finer point of philosophy, a hypothetical alternative universe where H2O is called XYZ , and Logic doesn't apply..?

I didn't say it's not valid. It's all fine and good to extrapolate but not blindly. Ignoring variables and not giving any credit to those improved efficiencies over an original iron cylinder application blows extrapolation exercises to smitherines. "Iron cylinders once ran hot. Therefore all iron cylinders run hot." Laughable. Logical Fallacy. Beware.

-everything will fatigue "eventually". Just as "we are all dead in the long-term". The trick is in making this work long enough that it accomplishes what we want it to (whatever it is that is going to fatigue).

Exactly. Reducing pressure will maybe keep us alive longer just like our engines. Ignoring pressures... early dirt nap.

-I would like to hear more about the rural machinist that builds hundreds of circle track motors.

The shop has done engines primarily for Thunder Road in Barre, VT for the last few decades and has worked through a few for my family and friends over the years for various applications. Knows his machines and how to use them... no BS or smoke blowing out of this shop and just delivers honest results with no secrets. Doesn't talk to you like you're dumb and he's an all knowing professional. Those are the folks I like to do business with.

-Aluminum, whether cast or forged and with regards to alloy selection, can have quite different thermal properties. I would venture to guess that the QSC are at the ****ty end of the stick. But I am still interested to learn what you find.

What makes you say that other than country of origin? Just remember the Chinese didn't make these magnesium cases that are so prone to failure. The FatherLand did. Guess where your Iphone came from... We could go back and forth with examples all day. Quality and national borders don't guarantee a certain result. If I had complete confidence in the cylinders I would have orderd the JE pistons to match when I spoke with Jeremy over there last week. I trust my machinist to confirm spec and to test before I put them to use. I would do the same if these came from Germany or our host even. I've had plenty of name brand failures with German parts over the years... blind faith will get you burned.

-"The difference is the aluminum cylinders warp before iron or steel would. They had to add a liner to increase strength." What do you mean here?

Not sure your question. It means exactly what it says. How strong do you think the cylinder would be with respect to withstanding the forces of operation without the Nikasil liner? I've seen plenty of uncoated aluminum jugs. They are all very heavily worn.

As for warping...the topic would be deformation. Not sure how far you want to dig in here. Commonly understood that aluminum deforms under far less pressure than cast iron when everything else remains equal. Chris covered this earlier in the thread. Fact not opinion. Basic example: Go out to your average chevy and whack the side of the aluminum head with a hammer and look at the dent. Now whack the cast iron block and notice nothing. Add heat and it only gets worse for aluminum...

Aluminum cylinders can be just as strong as iron ones, they just have to be thicker.

Unfortunately not as an absolute rule anyway and I'll avoid covering the deformation from above again... the galling properties of aluminum at the surface level is where this statement starts to fall apart. The Nikasil coating addressed the galling issue for aluminum at a molecular level. As for plastic deformation strength of the cylinder, cast iron and aluminum aren't in the same league. Plenty of heavy reading if you really want more about aluminum on aluminum wear:

https://www.forging.org/system/files/field_document/FIERF-AISIFinalExecutiveSummarySept04.pdf

Depending on the required strength, the additional thickness could prevent the aluminum cylinder from being viable. But due to light weight and excellent thermal conductivity, imho it is preferred. By liner do you mean the iron of the biral , or Nikasil? Both were done not to make the cylinder stronger , but to surface finish the bore so that an aluminum piston could ride inside the cylinder without galling/destroying it.

Sounds like you already understand what I wrote above. I think we're side tracking into aluminum vs iron...both have been shown to work in production and performance automobiles. The question here remains what works with the magnesium case... apparently cast iron with matching fastener has an excellent record of undetroyed cases while the aluminum does not.

-Original Biral cylinders were iron cylinders with Al fins cast onto them. The JB Racing "Biral" cylinders have an iron sleeve pressed into an aluminum fin part. The result is vastly superior to the originals - which IMHO are worse from a reliability perspective than solid iron cylinders - assuming temps are under control. The aluminum fins have a tendency to delaminate or "expand off" the iron cylinder center under hot conditions.

Would not consider biral viable here. Press fit billet aluminum to steel only or cast iron experiment.

-finally. Heat is energy. We want heat (to do mechanical work)! You know the racing GT3 motors are running searingly hot inside, on the verge of detonation? Porsche tuned their fuel injection and ignition maps by running these motors ultra-lean with tons of advance to generate failure, just so they could back up a couple notches so it would stay alive right on the ragged edge. That ragged edge is MUCH further with a water-cooled engine vs. an air-cooled one due to the thermal dispersion capabilities of the medium, but the idea is the same. We want the combustion to be as hot as possible, while we want the outside of the cylinder cool! A "perfect" engine would run huge combustion temperatures- enough to perfectly vaporize incoming fuel - and yet wouldn't even require a radiator...

I think you've stepped out of your comfort zone with this statement. I've been tuning for awhile, not just on my own car and I don't mean bolting parts on as tuning. Heat is a byproduct of the work we're doing not the primary; power output at the wheels is where you want the energy to go ideally not into heat as a waste product or out of the tail pipe. I see you mention the fuel and ignition curves in tuning. There are two schools of thought on which is better - slightly rich and advanced or slightly retarted lean. Both will impact fuel consumption and output in the form of waste heat and force. Most street tuners go slightly rich and average or slightly retarded ignition with knock protection so the meatball behind the wheel doesn't blow it up quickly. You can go another level of safety for Captain Meatball and talk him into water-methanol injection to futher disapate heat in the combustion chamber and to safegard against detonation. If you're a race team then you're possibly tuning differently and measuring consumptions more closely for pit stops to remain competitive.

The fact that race teams (not just Porsche) tune to the balance between lean and power and material capabilities is because of competition and sanctioning rules. They too are often trading off all-out performance for fuel economy on certain tracks.

Sorry about that last tangent - seems we're down a bit of a rabbit hole getting into tuning theory even though it does relate to the temperature discussion. The test will be with PMO carbs so tuning options will be somewhat limited.

[Lapkritis]

Are there any examples of direct port water methanol injection used on normally aspirated 911 for detonation suppression? Huge cooling benefits on the non-Porsche turbo cars I've used it on. Have a system here on the shelf that may also find its way in.

Good introduction for those unfamiliar; this is on a difference engine design but covers the basics:



http://www.youtube.com/watch?v=skuIkE93TR8

[Lapkritis]

Originally Posted by chris_seven

When a material is subjected to a continuous force and even moderate temperatures crystal defects can mecome mobile and due to diffusion effets a loss of strength occurs.

The influence of time/temperature/force can be plotted as a 3 Dimensional surface and changes in any one parameter can have a big impact on success or failure of a set of components.


Over long periods of time strengths of materials can be very seriously affected but the 'damage' to the structure would be restricted to those areas being subjected to the highest level of stress.

Clearly managing temperature is significant as there will be a critical temperature below which the thermally activated mechanisms that cause this damage will not operate.

Chris, I'm curious to know more about the diffusion and mobility of the crystal defects. I won't be able to use proper terms so I'll have to ask in the form of a story/hypothetical. Say we have a magnesium case engine and are studying two cylinders side by side on this single engine. One cylinder has the case saver of maximum size and the other has simple early timecert. The case saver has larger thread and from what I understand different pitch so the profile of the single thread is taller and the overall thread is more coarse relative to the timecert. Given the same pressures that would initiate the mechanism for crystal defects to become mobile, should we conclude the finer thread will always fail first because the physical distance is actually somewhat shorter for that failure to travel? Rate * Speed = Distance... the train going further at the same speed shall arrive later. All other factors being equal for the simplicity of this exercise. I believe this might be the case but am interested in how that actually works.

Thanks for the reply,

[porterdog]

Originally Posted by Lapkritis

I definitely will not be of those eventual victims I mean customers.

And you're worried about my dignity? I'm not, particularly, so I'll call a spade a spade and tell you you're an ass.

[Lapkritis]

If you have something tough to say to me then PM me. Putting in a show for your pals isn't going to end well for you.

Edit: And by not ending well I mean with respect to forum rules/moderation and nothing more. Just so we're clear for those with wild imaginations.

[blue72s]

Originally Posted by Henry Schmidt

If you were paying attention, you would have noticed that temperature control is one of the necessities when it comes to 2.7 longevity.
Porsche did away with cast iron cylinders because they (cast iron cylinders) are detrimental to cooling.
Even as early as the 356, Porsche realized that cooling the cast iron cylinder was difficult.
The reason no one has played with 90mm cast iron cylinders was because they don't work well.

I agree with you but apparently Paul Frere made no mention of that in his book - Porsche 911 Story. He stated the following:-

The Carrera RS 2.7 engine differed from the then current 911S 2.4 litre only by its cylinders of 90mm bore. But to achieve that bore size, the cylinders had to be changed from Biral to Nikasil (alloy cylinder and fins with an electrolytically deposited layer of nickel and silicon carbide forming the working surface) because only the thinner walls of the Nikasil cylinders made it possible to get a 90mm bore within the maximum possible lower flange diameter [spigot].

Originally Posted by Henry Schmidt

We played with 90mm Biral barrels years ago with no positive effects on head stud clamping.

What 90mm Biral barrels?

Originally Posted by Lapkritis

We are designing the sleeve/billet cylinder now. I am also going to test out the QSC 92mm set

If Weissach determined that it's not possible to build 90mm cast iron cylinders to fit within the existing head stud spacing, why are the aftermarket people making them, that is the question?