Head studs on 2.4 mag case

[neilca]

I have been reading a lot about head studs and sealing of heads since I had my problem with my race engine. 3 out of 6 cylinders do not like 12.5:1 compression Most of the talk is about the later big bore aluminum case issues. Does anyone have information for a mag case 86mm bore with birals? I do not think this has the expansion problem of the Nikasil cylinders.

I am thinking of using case savers in the block and some 125ksi studs. I am also going to increase my torque to 35 ft-lbs.

Will this work?

[Steve@Rennsport]

Case Savers are a MUST for any & all magnesium engine cases. No exceptions.

OEM steel studs are plenty strong for these engines and increasing head nut torque simply band-aids a bigger issue. Further, it simply adds more stress to a case that cannot really tolerate much at all.

[neilca]

Steve,

Is the "bigger issue" the high compression?

Thanks,

neilca

[Steve@Rennsport]

Originally Posted by neilca

Steve,

Is the "bigger issue" the high compression?

Thanks,

neilca

The bigger issues is the lack of sufficient rigidity and general weakness of these cases. Frankly, these are now all very old and the physical properties have changed due to age & heat. I would not use one of these for any race engine, anymore.

I find them particularly unsuited for both high RPM and very high compression engines. I've even had early, sand-cast aluminum cases crack across the main webs after sustained high RPM usage.

[HawgRyder]

Steve...just a question that popped into my head.
Is anyone making a replacement case for the older engines?
The old ones are not getting any younger...and I thought there might be a market for new replacement cases...or do we run into property problems with Porsche?
Bob

[Steve@Rennsport]

Porsche has not made any mag cases for several years and I fear the cost would be prohibitive if they did. I've heard that the tooling is all gone (high-pressure casting molds) so the current costs would be quite high to replace them. I inquired about buying some new 7R aluminum racing cases like they used to make and was told it was not possible.

Since these are patented parts, Porsche would not likely grant/sell permission to make them, given their history on things like that.

We are simply stuck with trying to rehabilitate these old things for purposes of restoration and street use, however I'd never use one for a serious race engine now.

[hightuned]

Originally Posted by Steve@Rennsport

Since these are patented parts, Porsche would not likely grant/sell permission to make them, given their history on things like that.

You dont have intrude on the patent, why not make a 6 cyl version on the Pauter bolt-toghether block ive read it can handle 1000hp builds? Its a smart design that isnt expensive to manifacture well atleast compared to making a preasurecast mold.

[chris_seven]

I would agree that the increased torque that you plan to apply would increase the preload in the stud and this will increase the possibility of pulling out the stud.

The likelihood of the head lifting would be due to the increase in peak cylinder pressure and the increase in area due to the bore size (only 5%) and I don't think this is too much of a risk so I would not be too inclined to increase torque.

The potential thermal and fatigue damage that Mr. Weiner says may have accumulated in the cases is a serious cause for concern and unless cracks have formed is almost impossible to assess and is a worry.

Re-manufacturing cases is an interesting challenge.

I don't think patents would be an issue as they would have expired long ago and even in Europe design registration only lasts for 25 years.

The cost of Pressure Die Cast tooling to make Mag cases would be extremely high and I am not sure that there would be enough market to justify the exercise.

Sand casting either Mag or Aluminium would be much easier and may eventually become a realistic proposition but again not cheap.

[hightuned]

Sand casting is ofc an option, or just wait for 3d printing to get there as that technology is taking leaps forward. You can print cinterd titanium today so ida say being able to print a engineblock isnt far away, in the futur we might even see plasic material strong enough to cope the the heat and stress?

[chris_seven]

As an old fashioned metallurgist I have never been keen on plastics for components that need a significant degree of thermal stability and the modulus variation with temperature is always likely to be an issue.

Titanium would be a bit heavy and difficult to machine but would probably be relatively strong.

AlSi10Mg is a Powdered Aluminium Alloy that can be laser sintered and it should have enough tensile strength but fatigue strength could be an issue.

The figures I have seen published seem to show a reasonable fatigue strength at 95 MPa but they stopped the test after 5 Million cycles which is a bit less than the accepted norm of 10^8 for a reasonable endurance limit for an Aluminium Alloy.

For prototypes this fatigue life would be OK but I would like to see some longer duration results to be really confident.

You can also buy 6061in a DMLS form but this alloy would have much higher expansion than the Al10SiMg which is much more like a typical casting alloy.

Developing the 3-D Model would be a trick and it would be quite difficult to scan as the internal galleries wouldn't show up.

We have just laser printed some prototype beer tap markers using a Zinc Powder and they worked out quite well but were expensive.



The cost of these parts was around $3k but I can discuss feasibility of printing cases when we next meet the printers.

[neilca]

Originally Posted by Steve@Rennsport

Porsche has not made any mag cases for several years and I fear the cost would be prohibitive if they did. I've heard that the tooling is all gone (high-pressure casting molds) so the current costs would be quite high to replace them. I inquired about buying some new 7R aluminum racing cases like they used to make and was told it was not possible.

Since these are patented parts, Porsche would not likely grant/sell permission to make them, given their history on things like that.

We are simply stuck with trying to rehabilitate these old things for purposes of restoration and street use, however I'd never use one for a serious race engine now.

Looks like I am caught between a rock and a hard place.

[hightuned]

Ive go no experience with metal printing we only use platic at work but i guess the metal printing uses a laser to melt together power material so perhaps a support material doesnt even have to be used? The model inst the prob we export cad files and convert all the geometry to a .stl format and then remove the the support material on internals passages with a ultra sonic cleaner.
Looks like we got a bit of topic here so i got a question about the 7R mag blocks. How fragile are they realy, the way ppl talk about the mag cases it sound like they are made of glass? Do i dare subject it to 15psi and 400hp, or should i just sell the superchager and go for a rs spec 2,7 build instead? You will find my dangling from the roof in the garage if i blow a engine after spending that much $ and time rebuilding it!!!

[Lapkritis]

Billet aluminum. Like edelbrock heads for v8 domestic...

[HawgRyder]

I like the idea of the Pauter case.
It should be fairly easy to produce the parts for a 6 cylinder Porsche case using bar stock.
You could choose the alloy and back cut or thin ribs into both the inside and outside of the case for cooling/heat transfer.
You could also embed oil passages into the system...and seal it with perimeter O-ring material.
While you were at it...how about incorporating gear driven cams?
Using the proper alloy would allow you to use slightly different cylinders as well...ones that bolted to the case...and then the heads bolt to the top of the cylinder....to allow for heat expansion but no stud pulling.
Ahh ... the possibilities....LOL.
Bob

[hightuned]

Originally Posted by HawgRyder

I like the idea of the Pauter case.
It should be fairly easy to produce the parts for a 6 cylinder Porsche case using bar stock.
You could choose the alloy and back cut or thin ribs into both the inside and outside of the case for cooling/heat transfer.
You could also embed oil passages into the system...and seal it with perimeter O-ring material.
While you were at it...how about incorporating gear driven cams?
Using the proper alloy would allow you to use slightly different cylinders as well...ones that bolted to the case...and then the heads bolt to the top of the cylinder....to allow for heat expansion but no stud pulling.
Ahh ... the possibilities....LOL.
Bob

I know they are endless. When i was in school getting my degree in machine design i started drawing on a 8 cyl boxer engine for use in a Porsche, the idea was to use heads and cyllingers from a early oil cooled gxr1100 engines mated in just that type of bolted billet block. Also gave using dual gsxr cranks with a 1,5:1 reduction gear some though as it would better suit the final drive of a car transmission. But a better choise would be a single crank with a bit more stroke to get a 2,5L engine with delivering around 320hp at 10000rpm just imagine the sound such a engine would make!

[Walt Fricke]

Hightuned

Bruce Anderson took to referring to the magnesium alloy cases as being made of sand. Porsche never ran turbochargers (superchargers would be the same in terms of stress) with them, did it? Maybe the 2.1L Baby? But those only needed to last for one weekend or so. Maybe just one race. No production cars, anyway.

Mag is not most guy's choice for boosted motors, nor for 12.5/1.

But an equally important consideration for compression is gasoline cost. You need race fuel, and not just premium with no alcohol, for that high a compression ratio. At 10.5 with twin plug you can get away with pump premium at 91 ron+mon/2 octane. I've done it with no problems. Not so higher with air cooled 911 motors. Steve says so, and I believe him. The water cooled motors, with the central spark plug and better head cooling, can run 11 through Porsche engineering magic, but 12.5 aircooled? I'm thinking about reducing the CR on my short stroke 2.8 because of track purchased race fuel price sticker shock.

[hightuned]

The boost inst the problem as ive done the calculations based on running it on E85 (which is actually cheaper then the low octane ron 95 gas we have in europe) with a 8:5 comp ratio. As this is my first Porsche engine build im starting with 0 experiance, ive read Wanes "how to modify.." which was a great insight into the components used in the engine and tells you what you need to upgrade. The case is getting savers for the studs and ill use arp's for the rods and head, but that is no insuranse if the cases tend to crack from stress. Ive seen a few 400hp 2,7 turbo engines around but i want a bullet proof engine so perhas i should leave the supercharger out? Perhaps im damaged from playing around to much from v8s in heavy cars, a fly weight 911 dont realy need that much power to be fun. The stock 2,7 was way to sluggish for my taste, but s-cams, 9,5 JE's, some port work for the heads and a race exhaus could perhaps push it the right side of 200hp? If that isnt enough i can always sell the drivetrain and build a new engine based on a 3,2 instead.....sry im rambling its sat and ive hade a few beers.

[Lapkritis]

Interesting to see if the increased heat as a byproduct of HP is the real problem rather than the HP itself. How much HP is safe if you keep the thermal expansion and materials temperatures down?

I'd love to try HP and temperature control experiment on a few mag case engines.

What case material did the rsr turbo have? Was above 500hp race from the literature that's out there. Must have been some tricks.

[hightuned]

No idea what alloy they used, but did the 210hp rs use the same block as the later 2,7 engines?

[Steve@Rennsport]

The 2.1 litre RSR turbo used an aluminum case, I believe it was one of the ultra-rare 7R ones.

The 2.7 RS (210HP) used a magnesium 7R case, just like all of the '74-on 2.7's.