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Underbored cyclinders are legal. The only stipulation in the class is that the displacement is lower than the required. They do not care how it gets there.

Charles. Great information.

Can you explain a little better on the heat soak issue. What that means and what that causes. How the early sleeved cylinders vary from the steel sleeved that Steve at Rennsport used for the 2.8L that they built and had good success with at 350Hp.

Were the cylinders different to begin with. I know that most of the sport bikes that are out there along with atv's and so on use sleeved cylinders making big hp per liter.

Thanks

Ed
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Old 09-15-2005, 04:50 AM
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Quote:
Originally posted by edbaus
I have spoken with Walt several times on this subject including in person at Watkins Glen. I do understand the costs involved as with any race motor. Walt's concern was more with ongoing costs rather than initial investment. He is suprised and glad for those who have the motors and how they have held up well.
...
The rule changes do not concern me. I think that gt3 will still be competitve if the current turbo cars are moved up as well. This proposed change has been on the books for a while.
...
As far as development, I expect that the work I have done with my 'street' 79 turbo will lend itself nicely to the racer. Yes the motor is larger and the cylinders are different, but my street car has been converted to twin turbos, has a custom made intercooler feeding a carrera intake and being controled by an electromotive twin plug system. All of this done by yours truly.
...
ed, thank you for the detailed response. I had only seen an offhand comment by Walt, I didn't realize you had talked to him in detail and thought about all of these angles. I think you are well prepared to build an engine like this.

To me an early turbo case with 66mm crank and underbored 92 or 93mm 930 nickies sounds the strongest, but probably also the most expensive
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Old 09-15-2005, 09:42 AM
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I do not know about well prepared.

I am the kind of guy that likes to jump into the deep end though. I usually find the best solution after I am done. If only I could start over.

I can not use the 930 cylinders (3.3 anyway) underbored with the early case that I am using. I am using the early case because it supports the 66mm crank and the head stud spacing is smaller on the early case than the 3.3 cylinder. The 3.0L turbo (early) will work, but they are hard to find and are 95mm, I think. The 2.7 are 90mm, so they are closer to my target size.

What I am wondering now is if I can underbore a 2.7L cylinder and replate. This is only a difference of 90mm down to the 83mm (1/4" per side extra material)

Does anyone alluminum sleeve and replace cylinders.

Does anyone have a source for steel sleeves that have worked in this application.

Thanks

Ed
Old 09-15-2005, 11:14 AM
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I have not heard of sleeving with aluminum.

These guys sell cylinders with steel sleeves:

http://www.jbracing.com/eng_porsche.php

don't think they are cheaper than nickies though.

I know RLJ's "Iris" rgruppe style car has sleeved cylinders, you might contact RLJ on this board.

the 3.0 turbo would take 95mm cylinders but cnavarro from ln engineering (That makes the nickies) was saying that he can make the same cylinders that would normally be used for a 930 in 92 or 93mm.

I can see where you would want to use your early alu case, though. If I were you I would either use full iron 2.0 cylinders as cnavarro recommended, or pony up for 92 or 93 nickies. Charles has a lot of experience with cylinders and I think his advice is good.

Cheers,
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Old 09-15-2005, 12:50 PM
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Charles, canīt you do custom heads?
A 935 style water (hurts my soul to type) cooled head maybe
That would take care of the heat problem in the cylinders.
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Old 09-15-2005, 01:30 PM
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Big difference between the factory "biral" cylinders and what are now made like the jbracing sets. The factory ones were for less of a better definition twice cast, meaning that the fins were cast on to the liner. I leave it best expained by the old 356 racers who saw porsche come out with birals that allowed them to make more horsepower but the extra power was a double edged sword in that under high loads, the aluminum would actually physically separate and loss of thermal conductivity would occur, making the cylinder run even hotter. This problem isn't unique to the Porsche design. Every company has had it's own solution from hourglass shaped liners to liners that have teeth into which the cast aluminum cooling fins can grab and index. The ultimate solution for a biral or bi-metal cylinder is a pressed sleeve into a billet "housing" like jbracing does. I have seen stock cylinders sleeved with liners, but the castings seem to crack like the ones that have passed through my hands. Obviously a billet version would resolve that issue with better alloys and processes.

There is a market for the steel sleeved cylinder. I made aluminum finned cylinders that resembled finned oil lines in the way we used a stacked plate design fin/spacer structure to cool the cylinder. Material costs were very low in the 50+ sets we produced for each run, but labor costs were outrageous. You do the math on how long it takes to stack by hand 30+ fins and spacers for a given cylinder then we had a jig that transfered the fins onto the actual liner with a .006" interference fit (if memory serves me right). That prevented the fins from loosing contact with the liner (we used an intermediary copper thermal paste with a thermal conductivity far above the ductile iron) under high thermal loads. Aside from man-hours and countless steps to make the birals as we had done, the benefits of a 100% aluminum cylinder led us to stop making our version of a biral cylinder and leave that to companies like JB Racing. There is always a place for a sleeved cylinder in cases with huge levels of boost where the rigidity of steel just can't be matched when using liner materials like 150-190k psi chromoly when compared to the factory aluminum cylinder @ 30-32k psi and even ours at 54k psi. Our only solution is to engineer a cylinder thicker than what the factory had to boost rigidity in that fashion, like with the 92mm versions of a 930 cylinder.

Water cooled heads are a solution, but even with flame ringing, you would have issues with "lift-off" and loss of sealing at high levels of boost. That's why Porsche made a mono-head/cylinder. It's the last step in the evolution of the aircooled engine. The only thing that cost is prohibitive, so our next best thing are the flame-rings, ni-rest, and inconel sealing rings and to manufacture the cylinder from the strongest and most thermal conductive alloys we can find.
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Old 09-15-2005, 03:07 PM
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Here was our dream for a cheap cylinder that cooled better than cast iron ones- they worked well, but we lost our a**es on them due to a clarical error during pre-sales. We ended up breaking even in the end though. One note- like the JB Racing, I like that the entire sealing surface is one single alloy (steel in the case of JB and ductile iron in our version of the biral from years back). The other imposters I have seen have two alloys on a sealing surface (like the face of the cylinder that sits in the heads). Having two different alloys that expand at different rates can't be good for sealing. I don't and won't make these anymore :-)
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Old 09-15-2005, 03:13 PM
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Charles Navarro
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Old 09-15-2005, 03:15 PM
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I also managed to find a picture of a 92mm 930 cylinder on my computer. Skirt thickness is ~ 7.5mm; Top thickness is ~10.5mm.



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Old 09-15-2005, 03:28 PM
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Very nice! thanks for sharing some of your experience, Charles.
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Old 09-15-2005, 04:32 PM
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Custom cyls

Ed, take a look at our cyls. that we make in house along with many other goodies.
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Old 09-21-2005, 04:25 PM
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Another point to consider with the sleeved cylinders is the greater choice of rings vs the nakasil. This was very important to me in my rebuild project for my turbo.

As a side note, since I've installed the JB Racing cylinders, I no longer have a coating of oil in my intake from the cylinder blow-by, effectively charging the oil tank from the case breather.

I'll have dyno numbers in the next two weeks for a before and after comparison.
Old 09-22-2005, 07:28 PM
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One other observation with my JB sleeved cylinders - I no longer have the blue puff of smoke on start up.
Old 09-23-2005, 04:51 PM
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