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calaway turbo project pistons?

I was looking at the calaway turbo project and they used new pistons and rings with lower compression and different shape and more of a carved out top on the piston. Does anybody know where you can find lower compression pistons like these that will fit in a 86 n/a? Can i get only rings for n/a pistons to lower my compression, or is pistons and rings needed, i would like forged but if rings will work in lowering the compression, that might be the best option for me. Thanks
Old 11-12-2002, 03:28 PM
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Try Mahle. find the addy yerself. Or you could email Dr. Holyoak and ask where they got theirs at.
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Old 11-12-2002, 05:43 PM
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Standard turbo pistons are dished.
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Old 11-12-2002, 05:44 PM
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Will standard turbo pistons fit directly in my engine and lower the compression to turbo specs? Will it run right with lower compression on my dme? Thanks

John
Old 11-12-2002, 05:46 PM
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Roastin:

Since you have an 86' you are in luck.

You have forged rods. You need to get 86 turbo pistons/rings.

If you find a complete 86' turbo piston/rod set you are in luck. If your block does not need to be rebored then you should be able to use the standard turbo pistons, but if you have to go to oversized pistons ..............OUCH! that will cost you.

Running at the lower compression your dme will run it, but I am assuming you are wanting to add forced induction to this vehicle.
And if that is the case you will need to add some form of knock sensing and timing retarding to it.

You will drop your compression to about 8:1 which is a nice number..........if you are planning on adding forced induction

You should be able to find a set of standard size turbo pistons fairly cheap....... or at least 3 out of 4. What normally happens is that a Turbo owner spins a rod or the #2 rod bearings goes and VOILA you have 3 good pistons that need to find a good home.

Also if you are going to mix and match pistons.....TWO BIG TIPS.

1. FOR PORSCHE OEM ONLY.

If you have 3 standard size pistons and need to use 1 oversize it can be done! The porsche pistons all weigh the same! And you can use one piston that is a different size.

2. IF YOU GET STANDARD SIZE PISTONS FROM DIFFERENT ENGINES

These pistons and rods should be balanced. Most machine shops will balance and match the pistons and the rods.

Have fun with your project.
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Old 11-12-2002, 06:32 PM
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I don't think you're on the right track with the whole project. If cost is an issue at all, then you should forget openning the engine. The 944 NA engine doesn't run too high a compression, 5psi will be fine as long as you get the air/fuel mixture and the timing under control (this I think would prove to be by far the hardest part of the project). Openning the engine is a lot of work, a set of pistons is a whole lot more money. No question, if you're looking for power with relative reliability at a reasonable cost, you can not beat a 944 turbo by adding un-natural aspiration to your 944. Again, don't forget everything else the 944 turbo comes with. That's just my opinion, don't be offended.

PS: I'd love to turbo or supercharge something that wasn't originally designed that way. Almost went through with it with my old 944 but decided against it after picking out several components. Over 8k miles of 19psi with my 951, I think that was the better way to go. I'm still thinking about picking up an old bmw or vw and turbo/supercharging that. May happen if I can convince my parents that it's a good idea for me to work on my car in their garage...
Ahmet
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Old 11-13-2002, 02:35 AM
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Ahmet,
How much power do you think you're getting at 19 psi boost? What other mods do you have now?
Old 11-13-2002, 03:38 AM
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To answer your questions on the Callaway, they machined the stock pistons to the depth of the valve reliefs. This was done since at the time there was no such thing as a factory turbo piston. If you were going to do it today Alex is correct simply use a set of factory pistons.

Here is the pic of a stock vs callaway modified piston. If anyone wants to make their own I have the specs from Callaway



Just to correct Alex on one point, the '86 NA 944 doesn't have forged rods, the cars with forged rods were the early 944 (the change was made in the '84 model year I believe), and the '86 turbo.

I have an extra set if anyone is interested in building up a motor.

Todd
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Old 11-13-2002, 06:49 AM
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Actually to correct Todd.

The forged rods are actually a 944 part number until 1986. The 87 and above (including the turbos use a cast rod)

The 86 NA' makes a great project car for a couple reasons.

1. The 86 has the aluminum control arms which bolt on to the 951 struts, hubs and calipers... so you can easily do a full conversion.

2. The 86 does have the forged rods, which may or may not be a benefit.


But don't let me fool you............it is still waaaaaaaaayyyyyyyy cheaper to buy a 951.

To create a different animal (supercharged or turbocharged) from a 944 is more or less a project "to see if it can be done"

It may not end up as reliable as a stock 951.

But then again a 951 running 20-25 psi, or with 400rwhp is never going to be a reliable daily driver either.

These are all expensive projects or conversions or whatever you want to call it.....
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Old 11-13-2002, 11:15 AM
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Alex

Sorry to be argumentative but the early 944s had forged rods. They switched to cast (check the factory manual) which also neccessitated a change in the rod nuts. The remainder of the normal 944 were all cast. The same forged rod was brought back only for the '86 turbo, and then replaced with a cast rod. Forged rods were brought back again for the 968 but these were a different part. If you don't believe me check out

http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic&f=15&t=012596&p=

If you look in the PET only the one part number is listed since all the forged rods were superceded with the cast replacement.

Not a big deal but in this case I know I'm correct.
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Old 11-13-2002, 11:31 AM
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Now we have an interesting dilemna.

I have a set of 86 Turbo Pistons and rods that I bought with the same part number stamped on them as my 86 NA? The piston is obviously different but the rod is identical.

Either I was extremely lucky and they had a set of old stock forged ones lying around.

It makes sense that porsche went to the cheaper cast ones.....but at the time of production of the 86 turbo they probably had a number of runs of forged ones to lower costs of production....... I can totally see Porsche sharing rods within that same year......... I mean they did ...at least in my car.

Very interesting stuff............

Now I wish they would of accidently slipped in a 951 transmission into my NA to go with the rest of my project....that would of realllllllllllllllllly made my day.
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Old 11-13-2002, 12:43 PM
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ae, todd is correct. Forged (sintered) rod changeover happened in 84, (later models getting non-forged), only used in the early 86 944 turbo again, until the 968.
Ahmet
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Old 11-13-2002, 02:50 PM
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Lawrance, I have a 3 inch turbo back open exaust, chips, intake, wires, and a 5angle valve job, port/polish and port matched on the intake side with a new valvetrain. The stock wastegate was "rebuilt" and "modified" by me. Now there's no signal line going to it, just sitting with a whole lot of preload on the spring.

I think I'm making very close to 300ft-lbs @flywheel. I will have the car dynoed after I do a couple more small things to it.
Ahmet
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Old 11-13-2002, 02:56 PM
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Ahmet,
I don't know what mine puts out. Here is what I have.

MAF
K27DR turbo
Ported/polished head (exchange program with Powerhaus)
Extrude honed intake
Oversized pre/post intercooler tubes
Reamed throttle body
Higher fuel pressure
Straight exhaust
Head gasket
1.1 bar boost

It keeps up with most cars in a straight line. But not with a GT2 that was at Road Atlanta two weeks ago. Also will not keep up with Supercup 911's.
Old 11-14-2002, 03:26 AM
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Not to belabour a point but here is the page from the workshop manual. The parts manual also shows the '86 turbo using the 944 103 001 00 forged rods that are superceded by the cast part.


You will notice that the forged and cast rods are physically different, since the forging creates a lighter part than casting the forged pieces are beefier and more squared off ( like an I-beam rod similar to Pauter rods) while the cast pieces are tapered and thinner (weaker) since the two end up being the same weight.

If I had a digital camera I'd take a picture of the ones in the basement to better show the differences.

The numbers stamped on the rods aren't true part numbers these are raw casting numbers.

Todd
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Old 11-14-2002, 05:24 AM
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u know.... this is getting interesting...

My NA rod that I have sitting in front of me says the following along the inside of the connecting rod shaft which is the same? as this used 86' turbo set (which I received from MikeB)?

the partnumber reads... 944.103.001.0rarst

Both rods look like the fatter ones in the manual (by the way I have the manual as well) so I am assuming they are forged.

What is interesting is my friend Marksports sent me a set of rods and I believe they came of his 86' as well and they look like the thinner ones with the numbers on the rod base and cap??? So I assume those are the cast ones?

Uhmmmmm weird indeed.
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Old 11-14-2002, 07:14 AM
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