944T Engine Rebuild

[barks944]

Good explanation! I stand corrected.

 

[u63af]

The worry I have about more low down torque is that I live in Scotland and it rains a lot. I already have problems with wheel spin when the turbo boosts in and was concerned. However, I do always want more power.

What mods do you need to do to go to a 2.8? (i.e ecu remap, maf etc). Also what parts would I need for the engine?
Cheers

 

[barks944]

ECU remap etc plus S2 crankshaft, rods (or some block modification for clearance) and a set of pistons afaik. Maybe you could use the stock pistons and a shorter rods instead, not sure..

 

[Diver944]

ORIGINAL: u63af

What mods do you need to do to go to a 2.8? (i.e ecu remap, maf etc). Also what parts would I need for the engine?

The bare minimum would just be a remap and larger injectors to allow your AFM and ECU to deliver the correct fueling for the extra air required by the engine. My own 3.2L initially ran on just a modified chip with the original AFM and had safe fueling up to 1 bar of boost. Higher than that and the AFM couldn't cope so was replaced with a freer flowing MAF setup

The parts needed for a 2.8L are an S2 (or 968) crankshaft and 4.55mm shorter con rods (Lindsey sell a Carillo version of these)

I initially had the 'Cup' clutch and it was fine up to 450lbft, after that it started slipping.

 

[Lowtimer]

Whatever power level you want, the car will be smoother, more predictable and more responsive to the throttle if you get there with a 2.8 and lower boost compared to the same power via a 2.5 with higher boost. It will be easier to maintain traction using your right foot because the power curve will be smoother rather than everything arriving suddenly in a rush. That was another factor borne out by Barry's 3.0.

 

[GPF]

ORIGINAL: Diver944

I initially had the 'Cup' clutch and it was fine up to 450lbft, after that it started slipping.

[][][][][]

 

[TTM]

Yes, more capacity translates into better traction, at least when using a turbo sized for mid-range performance like a chipped K26/8.
I have read that building a 2.8 by reusing shorter rods with original pistons wasn't a good thing - check Chris Cervelli's old posts on Rennlist.

 

[sawood12]

It is torque, not power, that turns things, the more torque you have at low RPM the quicker you'll accelerate. However that longer stroke will hurt you at higher RPM. The gases in the combustion chamber start to expand once they are ignited and the expansion happens at a constant pressure - pressure rises to its maximum very quickly as the fuel starts to burn, then is maintained as the piston descends and the cylinder volume increases and fuel is still burning. Once all the fuel is burned then no more heat can be pumped into the gases and they start to cool as the cylinder volume continues to increase and the expansion rate starts to decay and hence the pressure inside the cylinder. This provides a nice constant force on the piston as it descends which then decays as the fuel is burned and the expansion rate starts to decay. For high RPM engines you want to get to BDC before this point to avoid it because you are trying to achieve power through high revs rather than high torque and don't want anything to be working against you, but for long stroke/lower RPM engines this has less of a detrimental affect as you spend less time at high RPM.

It works something like this anyway as far as my understanding goes!

So a long stroke engine is particularly good for street and twisty tracks where you spend most of your time accelerating out of slow bends. So in short - for a road car more torque is good even if at the expense of power at higher RPM's.

 

[barks944]

i remember reading there was a right way to do a stroker engine. Can't remember why now but it wasn't just changing the rods and crank.

 

[barks944]

Help me people I'm thinking LS V8!

 

[Lowtimer]

Do it if you want: you will have an interesting car but it won't be a Porsche 944.

You can buy quite a nice Corvette for the cost of doing a good LS conversion.

 

[barks944]

I could probably buy one for the cost of a stroker conversion!

 

[chrisg]

Having recently rebuilt a Turbo engine, a couple of points to throw in :

1. You'll struggle to find a clutch fork in Europe, the only place I found one recently (this year) was LR in the US.
2. If you're going to all this hassle to rebuild the engine, is it worth going down the 104mm bore cylinder inserts as provided by either Hartech or Perfect bore in Hampshire ?
3. Whatever you do, spend a little extra and have all the moving parts (flywheel, clutch, crank) balanced and the Pistons and rods blueprinted = accurately set to the same weight by a good engine builder.
4. Wouldn't a cometic head gasket be a better option ?
5. Did you list uprated injectors ? - probably worth replacing the fuel pump and installing a fuel rail pressure gauge as well.

Good luck with your project and keep us posted !

 

[barks944]

Thanks for those suggestions chris. On the topic of Bores, mine look pretty good to my eyes so I wasn't going to do anything with them. I've uploaded a load pictures of them to this picasa album, they are all in similar condition.

http://picasaweb.google.com/tombarker1804/944TBores?authkey=Gv1sRgCPKWzsCex4ak2AE&feat=directlink

Heres an example:

 

[944 turbo cabrio]

Hi,
trying not to high jack the thread I will just mention I find it very interesting as I am also thinking about a 2,8 stroker in my cabrio.

I have over the last 1½ year been collecting bargains and now I have the following ready: CUP headgasket, new PPM H-shape rods in standard length (weight 575 grams!) S2 crank and also a 340 RWHP set from Lindsey with a bigger turbo, 55 injectors, 3bar regulator, MAF kit, full 3" exhaust and DP, WB02 meter and MBC. The latter I bought as I guessed it would be suiting the build quite well (except for the chips supplied). I have also bought a stage 3 clutch and lightweight flywheel and pressure plate to manage it all

As I am still missing the associated pistons I was thinking maybe there is a possibility of buying together if you want to go the stroker route???
It may make things a little cheaper?

Do anybody else have experience with these stroker engines? I am not a very technical guy so I am very happy to hear any experiences - though happiest to hear good stories[]

Cheers

Niels

 

[barks944]

I've contacted Andial over in the states. Lindsey Racing also sell various pistons we could use.

On a side note I've been looking at replacing the turbo on my car with a Rotrex Centrifugal supercharger. Thoughts?

 

[GPF]

ORIGINAL: barks944

I've contacted Andial over in the states. Lindsey Racing also sell various pistons we could use.

On a side note I've been looking at replacing the turbo on my car with a Rotrex Centrifugal supercharger. Thoughts?

Jeeze, I only tossed the 2.8 in as an idea......[8|]

I think you should stick with a nice turbo! []

 

[DivineE]

A note with the 2.8 stroker kit if you are going to go that way, make sure you get the correct pistons. The height of the pin is different from standard pistons and this caused me trouble when I had to move to .5 oversize and the pistons came out the top of the bores! []

 

[barks944]

Did you use S2 crank, stock rods and aftermarket pistons DivinE?

 

[JarmoL]

Hi there

My 2.8 stroker engine was built in Germany by previous owner in 2004. (Now done about 45000 km) . It's built with modified 951 pistons, shorter Pauter rods and S2 crank. This is supposed to be the wrong way to do it. It has been reliable though.. I just changed the head gasket first time last summer. Car has seen quite a bit of track action so I consider the 40000km head gasket change interval quite acceptable. (I am running only 1 bar boost though)