924Board.org

Sharky · Joined: 29 Jun 2012 Posts: 14 Location: Australia

Hi guys,

I have a few quick questions for the gurus regarding the aforementioned parts....

Does anyone know where I might find main bearings for a 1981 924 Turbo engine? They seem to be very hard to locate. Everything on ebay is for 82 and onwards. Can I pillage them from a different model or something??

Also wondering.... If I get a set of JE pistons from EBS racing... is there a supplier of new con rods to suit their wrist pins?? (I think they said they use 22mm pins, and they supply bushings as well)

And the final question....
I have sent my turbocharger away for some upgrades, (compressor wheel, bearings, machining etc)
... If the unit is going to push more than the factory spec of .8Bar, How much higher can it go above .8Bar before I have to pull the compression ratio back on the Pistons???
Or is there a calculator somewhere to help me calculate the right compression ratio to suit turbocharger output??
I've been told that I can expect a bit more than 1.0Bar from the upgrade

Many thanks in advance to anyone who can shed some light here for me.
And... If these seem like stupid questions... I apologize. I am an IT & T technician... but man I love my Porsche enough to ask a stupid question rather than make a stupid mistake.

Big fan of the forum

Carrera RSR · Joined: 08 Jan 2010 Posts: 2312 Location: Somerset, UK

Mittelmotor in Germany can do all these parts for you and advise specs. Their GTS spec race car is using mostly stock/re manufactured GTS parts and is now achieving 400bhp with CIS and K26 turbo. So plenty of headroom for modifying your turbo. They supply Pistons (8.0 to 8.2:1 CR), rods, bearings, modified K26 turbos (1.0 bar++), MLS HG etc. etc. Going to one specialist gives you some confidence all the ingredients will work together as its all tried and tested in other race and road cars
_________________
1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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Raceboy · Joined: 01 Mar 2004 Posts: 2327 Location: Estonia, Europe

It's just the matter of money....

Mittelmotor is good but their prices are expensive to say the least...
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold

'84 924, turbocharged, sold.
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Carrera RSR · Joined: 08 Jan 2010 Posts: 2312 Location: Somerset, UK

Very true. But there is some comfort, and of course cost, that the parts supplied compliment each other and are proven to work. If you are a seasoned parts sourcing kind of guy and you are confident in buying from various vendors and ensuring they are work together, then money can be saved. I have done both and won and lost time and money on a few transactions. Its best to go to Mittelmotor for a direct quote on parts rather than use their ebay prices. These inflated and include ebay and paypal fees.

I didn't follow up the JE piston sourcing route, but I heard about this wrist pin issue. However I was also told by one JE reseller that the pins can be spec'd to stock dimensions. I don't know if true or not.
_________________
1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252

Fasteddie313 · Joined: 29 Sep 2013 Posts: 2595 Location: MI

Are you having your compressor housing machined to fit a larger compressor in there? If so what compressor wheel?

A compressor change in itself should not change max boost, it may be capable of much more boost but thats up to the waste gate and/or boost controller to set the max boost before it dumps the excess exhaust..

Dutchpug is getting 352 rwhp @ 1.6 bar of boost pressure (around 400 engine hp) on stock NA (higher) compression ratio, but that is with proper tuning with a proper stand alone management system, and he seems to really know what heys doing, so I would think you would have plenty of headroom anywhere around turbo spec compression as long as your tuning can keep up with it without going lean.

If you're running 931 CIS I think you'll hit its limits of maximum fuel delivery a long time before you'll run into limits due to compression ratio..

Also any boost increase almost mandates the addition of an intercooler to keep intake temps down, without one you'd be living very dangerously indeed...

Good luck..
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80 Turbo - Slightly Modified

Sharky · Joined: 29 Jun 2012 Posts: 14 Location: Australia

Hi Guys,
Thanks for the replies.

Carrera RSR, I will have a look at Mittelmotor and see what I can source. I do like the idea of having parts that are designed to go together. Having to do so much research on each individual purchase makes it very time consuming and creates an air of doubt that I'm not totally comfortable with.

Fasteddie, I am not totally sure of the specs of the new compressor, I was told that the unit will be machined and a new Billet compressor was being made up in-house by the Turbo mob. Just got the unit back today and they have put their company stamp on it instead of the original KKK stamp.

Numbers read 5326 970 7007HF (I'm guessing the HF is "Hi Flow")
Apart from the "HF" the number is the same as the original, but I asked for an upgrade.... soo I don't really know the specs of the compressor wheel.

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Sharky · Joined: 29 Jun 2012 Posts: 14 Location: Australia