3.4 vs. 3.5

[jdm61]

What are the inherent advantages and disadvantages of the 3.5 liter big bore kit as compared to the 3.4? I am eventually looking to do a pretty high powered NA motor, possibly using the 9Meister heads when they get around to building a set for pre-964 cars w/ Carillo rods and knife edged crank, etc.. i would also be using a twin plug Motec, Electromotive, etc. setup, possibly with ITB's. looking for 350hp or so, which is supposedly pretty easy to reach with the aforementioned parts while maintaining good every day driveability. I understand the the case machining required for the 3.5l kit is a realtively cheap fix, but are there things I need to watch out for? One cosideration would be that 9Meister sells their own 3.4l 10.2:1 P % C set.

[Jeff Alton]

Well. It depends. I don't think (though maybe I am wrong) that ninemeister makes anything on their own. Those heads look suspiciously like the ones from CMW (CWM?)

The 3.4 kit is slip in and the 3.5 requires minor machining of the case. Want big power, how about a 3.7 with 102mm barrels and a 964 crank.
Some say, not me, that the 3.5 has a cylinder that is too thin to last very long. (make up your own mind on this one).

I am 95% done building the 3.4 engine in your description. I skipped the Carillo rods and instead balanced mine to zero and used ARP bolts. I also am using 3.2 heads with the valve guide bosses cleaned up and the ports midly re-shaped instead of billet heads!! I am using Jenvey ITB's on it with port matched manifolds and a microtech efi twin plug set up. Big cams (well sort of, they are modded S cams from John ground for my motor combo) and I am a little small on the exhaust at 1 5/8s to keep the bottom end torque there.

If I were doing it again, I would use the LNEngineering Nickies from Charles and the same 10.5 JE's that I have now. I don't know who makes the cylinders for 9meister, but they do not get any better that the stuff Charles has. I would also try a set of the rods he offers if I was changing rods.

I would go 3.5 and get the machining done (cheap in the big scheme of things) or 3.7 and buy a 984 crank.

You will probably get your 350hp out of a 3.5 with good heads, high CR, ITB's, twin plug, motor but you need to get the right cam and exhuast to go with it. It all depends if you want it peaky or if you want a nice wide power band. I gave up a little on the top for a wider power band (I hope )

Also, I see you are in FL, USA. I am not an American, but I would spend my dead presidents on as much stuff made in the US as I could!

Cheers

[jdm61]

The 9Meister heads are made by 4Tech, who, from what i have read in the Brit mags, do a fair bit of work in F1, WRC and WSB. I'm thinking either Jenvey or WRM (?) with Motec or Electromotive. If I don't have to spring for the Carillo's, i wouldn't mind that. I'm not looking for 450hp+ GT3 numbers and i am willing to sacrifice a bit of absolute power for a nice powerband. Left to my own devices, I would probably go with the 3.4 Mahle 9.8's. My biggest di,emna is going to be what to do with the transmission. They make upgraded hydraulic clutch setups for 915's and burlier gears and bearing plates. Not sure whether to go that route or a short housing G50. I have no desire to chop up the torsion bar tube and plan to stick with the old torsion bar setup.

[Jeff Alton]

Hmmm, I run coil overs and a 915. Someday I may stuff a G50 in there but I like my 915. I had to put a WEVO side cover (with the 930 bearing) on mine from just the previous mods. I don't think the gears are the problem per se, but if stuff starts to move around then they seem to let go. There are plenty of good HP clutches (cable operated) available for the 915.

The Jenveys are absolutely a peice of art. If you search my name on this board you will see some good pics of them. I went with the JE's and bored and plated 98's for a couple of reasons. One, I wanted an actual 10.5 CR and new I could get it with the JE's. ( I measured it all and it came out to 10.5.000xx when I was done). Second, I don't need a 60K mile motor and if the JE's don't last I will build a 3.5 or 3.7. This one is a learning curve for me so if I have to experiment a little with cams and such I will.

If the wallet allows it I would go Motec, just me though. All that said, it was a real tough descion for me to go EFI. I like carbs. I like tunning with screwdrivers and wrenches. It is a comfort level thing for me. I have never tuned with my laptop, but am willing to learn. Everyday I wonder about selling the Jenveys and buying a set of PMO's and going "ole skool". I still may do that yet.....

Thanks for the info about the heads. I read those british mags and see all the companies claiming to have " our own new this or that" only to see it is rebadged US stuff. I also find them to be optomistic with their HP claims. I perhaps put 9meister in that group without doing my research! Not the fist time for me

If you need cams, give camgrider (John) a shout. He is great. He has done a few sets for me. If you have considered Haltech, try TimT or GTU935 as they know there stuff and have been very forthcomming with info to me, great guys. Ralph (carrera35.l) has built a nice street 3.5 and has a couple of very detail threads on its build up. He know of what he speaks and thinks the 100's should be fine for the long haul (3.5).

The rods should be fine. There is a recent thread where their is talk of modding SC rods to work (and the reasons why) a quick search should turn it up as well. I can't remember the thead title off the top of my head.

Cheers

[jdm61]

Total 911 has apparently done two articles in the last few months about the 9Meister heads. The recent one that I read had a testof several 993's with the heads. The upshot was that the claims of 350hp+ using stock P & C's and 993 intake and engine management are accurate. Supposedly, they are building a "GT3" setup where they swap out the REST of the engine parts and are looking for somewhere in the range of 450 "streetable" horsepower. That would be a bit much for me, I think, but it will be interesting to see how it turns out. Their next head project is for the 993tt/GT2. After that, they are supposedly going to bring out heads for the Carrera and SC. By best guestimate on the Jenvey/Motec system is that it will cost some where north of $10k plus duty. Kinda pricey. The highest prices I have seen for a complete Electromotive ITB system is in the low $8k range. I would definately beef up the 915 if i could get away with if for no other reason other than weight savings over the G50 box. the old M491 carries enough extra fat around the middle as it is, but i want to leave the interior "livable" for the foreseeable future.

[JeremyD]

Something wrong with your engine?

[Carrera3.5L]

Originally posted by jdm61
What are the inherent advantages and disadvantages of the 3.5 liter big bore kit as compared to the 3.4?

My opinion only:

Advantages

1. Maximizes displacement without extra expense of crank & rods. 3.4L motor is actually well under 3.4L and is "rounded up". 3.5L is a true 3.5L (3506 cc). Almost as large an increase from 3.4L to 3.5L as it is from 3.2L to 3.4L.

2. Maximize potential horsepower with better low & mid-range

Disadvantages

1. Cylinder walls thinner. My opinion is this is more a relevant concern for a turbocharged application than a normally aspirated one. I think for a street/light track motor it is a complete non-issue...

2. Extra cost. Twin-plugging for street use on pump gas is more or less a requirement while on a 3.4L motor it is considered optional by many. Case spigots also need to be enlarged, although the machining cost for this is minimal.

3. Case commitment. What I mean by this is once you have enlarged your engine case spigots, you are committed to 100mm pistons/cylinders. With 98mm versions, since they are "slip fit", you can always go back to stock 95mm diameter if the need ever arises.

4. More rare. Just from a Mahle point of view, 100mm pistons/cylinders are not a hot item and thus when supply runs out, there is a good chance you would be out of luck in the event of needing to ever replace pistons/cylinders. Fortunately, other manufacturers seem to be making products to fill any vacuum...

My belief is the 98mm conversion was initially popular with Carrera owners because it could be done when the car was new or had low mileage without having to do a complete rebuild. This conversion was popular when doing top end head work (valve guides, head studs, etc). The 3.5L conversions were most often considered when the motor had to come completely apart for some reason or if the owner had to have that last little oomph to outrun his doctor friends or have the best engine story to tell at cocktail parties...

Am I right about 100mm being okay for a street motor? I don't know, only time will tell I guess...

Jeff, 3.7L from 3.0L or 3.2L is done by using 102mm pistons/cylinders with a stock 3.2L 74.4mm crank and aftermarket rods such as Carillo. Extensive machine work is also required. See you can save money by not having to buy the 964 crank...

Ralph

[Jeff Alton]

Hmm that is good info, never bothered to check the math!

Cheers

[jdm61]

Originally posted by JeremyD
Something wrong with your engine?

Well, not anymore, but is that a requirement? lol Just looking down the road. I know that things can be done for the same money or maybe cheaper with a 993, but i am QUITE fond of the M491 chassis. One of the best looking cars Porsche bult IMHO. I'm working with something like Euro-Carrera power right now and that will suffice for the time being. So Jeremy.....are you going to make it to Fontana in November? And just for the record, why did you put 3.4's on your car? Did you need a total rebuild at the time anyway?

[JeremyD]

Originally posted by jdm61
So Jeremy.....are you going to make it to Fontana in November?

What happens in Fontana and where is it?

Originally posted by jdm61
And just for the record, why did you put 3.4's on your car? Did you need a total rebuild at the time anyway?

Well It started as a 3.2 and bad valve guides. after I got 400 miles to the quart after a few sessions at Sebring, I decided a top end was in my future. The top end then turned into a well, while I was in there = bump to 3.4, change rod bolts - damn 993 ss cam sounds good, extrude hone, headers - oh crap that's getting expensive.

Actually it was all Ralph's fault.

[jdm61]

Originally posted by JeremyD
What happens in Fontana and where is it?




Well It started as a 3.2 and bad valve guides. after I got 400 miles to the quart after a few sessions at Sebring, I decided a top end was in my future. The top end then turned into a well, while I was in there = bump to 3.4, change rod bolts - damn 993 ss cam sounds good, extrude hone, headers - oh crap that's getting expensive.

Actually it was all Ralph's fault.

Fontana Village.......the Dragon, Cherohala Skyway, the BLue Ridge Parway,New River Ord, the Hump, Nov. 3, 4 and 5.....be there....aloha!!! lol

[Carrera3.5L]

Originally posted by JeremyD
Actually it was all Ralph's fault.

Jeremy,

You did a fantastic job all on your own (both aesthetically and power output), you just needed a little prodding...

Ralph

[cnavarro]

There's no problem with 3.5's normally aspirated. Hell, I think I've made as many 102s (think 3.7 with 3.2 crank) for the 930 bolt spacing and they're fine too for normally aspirated. Twin plugging is almost a must for the larger bores IMHO, but I have done some lower compression <9.5:1 pistons for the 102mm bores for hotter climates for single plug. I've even toyed with the idea of slip-fit 100s considering the great results we've had with the alloy we started using in '04.

[davidppp]

Hello, Charles.

That' alloy is 3618, right?

Same as Je pistons, same expansion?

And IIRC its stronger than mahle's 4 series high silicon alloy?

Any issue with bore taper with the higher expansion?

I have never seen any actaul data for the temeperature of the bores, or the gradient from top to bottom.

I wonder if anyone has instrumented an engine to check this?

On the face of it, the Mahle-stylee ally could have less taper due to less thermal expansion...and in the later motors even using this alloy, mahle determined there was an advantage in compensating by pre-tapering the bores so they became closer to a true cylinder shape when hot.

What alloy is Henry using in his new Supertech cylinders I wonder?

Kind regards
david

[cnavarro]

David,

Our alloy is a 6 series, but a custom concoction whipped up by Alcoa for us. There are adhesion issues surrounding many alloys when it comes to the nikasil to take into consideration when choosing an aluminum.

Now here's the technical mumbo jumbo... and I'm going from memory here, since I don't have all my research in front of me since I'm in CA for GAF...

And I apologize in advance for being long-winded - there just isn't a short way to answer this one...

Just to compare known figures - I tested various Mahle/KS cylinders and the strongest was 32,500psi tensile with a W/m-K (thermal conductivity) of 120. From Perfect Bore's own advertising their alloy is 15% stronger than stock (and has roughly the same silicon content and expansion rates as a factory alloy per JE's own admission).

Now 2618, what JE makes the pistons out of, has a tensile of 54,000psi and thermal conductivity of 146 W/m-K. The alloy we use also has a tensile of 50,000-54,000 psi (varies by batch sometimes) with a thermal conductivity of 240 W/m-K. Another figure to look at is the % elongation of a particular alloy - this will determine how ductile and resiliant a particular cylinder would be under deformation before that deformation becomes permanent (i.e. failure).

The factory alloy had a very low % elongation min 1.5 to 4% (depending on whose database for material properties you are using), due to it's 11-12% silicon. 2618 has a % elongation of 10%, with a silicon content of .1-.25%. Our alloy has a % elongation min. of 10%, but usually comes in around 12% and has a silicon content max of .4-.8%, usually lower.

Lastly the Modulus of elasticity for a given alloy is also another factory of many I considered. 2618 tops the chart at 74.5 GPa and the alloy we use comes in at 69 GPa. I can't for the life of me find on google right now the Modulus of elasticity for the factory alloy which is closest (if not the same as from having them tested) to 339-0, which is also a common casting alloy for aluminum high-silicon pistons, but it's fairly high too, like the others, since hypereutectic alloys are known for their ductility but piss poor % elongation (go figure).

As far as exansion rates, we've checked our cylinders from below freezing to well over 500F to see how clearances grow (or shrink) with temperatures vs. a JE piston. This is how we know that the cylinder outpaces the piston just ever so slightly, allowing clearances tighter than what the factory used with our cylinders and a JE piston. And there is now issue we've seen with taper other than when a cylinder has been honed improperly by allowing it to get too hot (remember how high the thermal conductivity is compared to the factory cylinders). For this reason, the thermal gradient from top to bottom is much less, since the cylinders (and heads), tend to balance out temperature wise very closely. (I have had one builder I work with measure cylinder temperatures at various points to determine this years ago, even before we started making 911 cylinders).

And no, I don't know what alloy the QSC branded cylinders that Henry (and others) are selling, since you asked.

[davidppp]

That's great information, thanks, Charles.

Is the termperature gradient data proprietary or can it be shared please?

This is one of the hidden power-sapping elements in the 911 IMHO>...one which the Factory seems tio have lately compensated for..

Kind regards
david

[sladey]

Before you assume you can get the 98mm P&B's from Ninemeister, I'd check they are still doing them at all.

I looked into this around Easter this year and wanted to get them but when I followed it through they said they'd stopped doing them due to lack of demand. They are still on teh website though....

I went with the stock displacement as I couldn't justify the extra expense (this time......)

Now the engine's run in properly it's going like a dream

Cheers

Mark

[Rich76_911s]

Originally posted by cnavarro
. I've even toyed with the idea of slip-fit 100s considering the great results we've had with the alloy we started using in '04.

I volunteer to be a guinea pig.

Pick me, pick me, pick me

[cnavarro]

Seriously, I do think it can be done and made to live with a slip-fit 100. It really wouldn't be that much thinner than one of our 105mm type 4 nickies, which have proven themselves reliable for the long haul. What I would do differently is just not half moon the skirts for a tad more rigidity. One could also cryogenically treat the cylinder, but i'm not sure it does anything other than marginally improve the fatigue life. It would still be proportionally thicker than the slip fit 89s i've done for the 2.2/2.4!

[gumba]

Can someone expand on the 3.5 in a turbo application.
My turbo is being rebuilt as a 3.5, which is how it came. The shop said they could resleeve it to a 3.4 or leave it 3.5. It had Mahle cylinders w/J&E pistons. They are being replaced w/Mahle 3.5, 7.1 P&C's. Since no down side was mentioned I decided to leave a 3.5. This is a street car. The other specs are, SC cams, twin plug, 12 plug distributor, adjustable WUR, SSI heat exchangers, DP muffler, stock fuel head (shimmed as needed), tial 46mm w/g w/.8 bar spring. I'm guessing the w.h.p. will be around 350.
Thanks,
Harold