catamax944

Hey guys,

I was thinking of doing some mods to my 2.5 n/a.It's a 86' euro.Since it's kinda hard to get some real power with simple mods i'm contemplating a stroker setup.
My question to you is apart from an S2 crank what other things have to be changed/mods to do,to turn it into a 2.8?I'm thinking rods and fuel system at least.How about the head,would it be ok as it is,maybe just a port and polish.I don't really want to mess with the electronics too much,just a custom chip to accommodate the new mods,would that be enough?
Its going to remain just a street car so driveability is important.I'm not looking to get ultimate power from the setup but just to make it work to start with.

white924s

all that would be critical would be changing rods and tweaking the fuel tuning (eg you would need roughly 10-20% more fuel). A chip might be able to get you enough fuel at the stock pressure, but I imagine that you will probably need to increase the pressure on the fuel rail to supply enough fuel. An adjustable fuel pressure regulator should do the trick and Lindsey Racing sells one that should bolt right into the factory spot. You would need the chip reprogrammed to provide proper fuel and spark timing for the larger displacement engine, but I would imagine that that would be all you'd need

You could get away with leaving the head and intake alone, but you would definitely see benefits to porting/polishing the head.

If you do this, please post some dyno numbers - it's something I've been kicking around in my head for a while, but S2 cranks are expensive around here so I've never gotten around to it

V2Rocket

custom, shorter rods will be needed. several 944 tuning companies sell them. the stock rods are too long by 4.5mm, also the lower end of the stock rod would hit the crank girdle with that stroke.

fast951

The 2.8L will make more power than the 2.5L. However, unless you just want a 2.8L stroker, going to a 3L will yield much more power. We have tuned many 2.5, 2.6, 2.7 and 2.8L NA race engines. The 3L made more torque and more power. The money you will spend on building a 2.8L and tuning it properly, will cost more than finding a clean 3L engine.

If you decide to go the 2.8L stroker route, you will need 2.8L pistons, stock length rods (the 951 rods will work just fine in this application). Of course, you will need the engine management to handle the 2.8L. Fuel is just one part of the equation, ignition timing is very critical. The stroker engines love to detonate! We can supply you with the pistons to work in the Alusil block as well as the tuning. However, consider the 3L engines!

Tom M'Guinn

Really? Do tell...

BTW, I was thinking the same thing -- go with a good used 968 motor if appearance is not an issue, or with an 89 2.7 if you need to keep it looking stock.

white924s

Out of curiousity, is there any reason why you couldn't use the factory 9.5:1 pistons with a stroker crank and pauter rods? I know that compression ratio would increase, but my back-of-napkin guesstimate was that the CR wouldn't go much above 11, which should be well within the range of what a street motor can tolerate right?

Also, do you have any hp/tq numbers that you could share about some of those larger race engines? any info about how to get those numbers?

I realize that with race engines, there's a fair amount of confidential information, so I don't mean to pry, but I'd be interested in hearing anything more that you can share. Thanks!

V2Rocket

stock pistons and rods on a 3L crank would make the top of the piston protrude about 4.5mm from the top of the deck. the 4.5mm can be made up in either shorter rods or custom pistons with the wristpin moved 4.5mm

Tom M'Guinn

The Andial 2.8 stroker turbo pistons would work, but without the turbo, the low compression would produce lower power -- although you could use cheap gas probably without pinging.

JohnKoaWood

Taken from a 928 Stroker buildup I was looking at last night...

http://www.928sg.com/

not a 944, but a 5L 928 goint to 6.4L(394 Ci) He even grafted in 968 Variocam heads...

Might be worth reading for the 2.5 to 3.0+ thinkers in the group of what can go right vs what can go wrong (the main discussion engine in the website is his second engine as the first was destroyed after 5000 miles...)

Good on ya, maybe one day in the future I will pick up a second engine to build on, but for now I will enjoy driving my cars close to stock as will allow for daily driving....

white924s

Stock pistons and rods definitely wouldn't work - that's why I was asking about stock pistons and the Pauter rods that LR sells for 2.8l turbo motors. Those rods are shorter to work with the factory 951 pistons, so I think that they should also work with factory 944 pistons right?

John, thanks for the link - I'll look into that

333pg333

Any ballpark guesses or hard info (John) on what sort of power / tq increases could be expected by just increasing 2.5L out to 2.8L leaving other mods out of the equation? I have a friend that we are trying to convince to do this to his n/a car. Putting a 3L 16v motor into a 944 is not just a straight swap and would cost a bit to do this conversion I'm thinking?

Tom M'Guinn

Well, when Porsche made a 2.7 in 89, it made 162 I believe, which very closely matches the percentage increase in displacement from the 150hp 2.5. I know that was a bore motor, rather than stroke, but still... So, my guess, all other things equaly, would be about 168 for a 2.8 n/a 8v motor. The factory 2.5 944S motor made 188, so that may be a better route -- with factory parts available to boot!

white924s

If it were possible to use factory pistons, I would imagine that you could get better performance out of a stroker motor than the bored out motor because, all else being equal, the stroker engine would have a higher compression ratio. Then again, for comparable cost, you might be able to get high compression 104.5mm diameter pistons...

catamax944

To sum things up i guess the stroker is out of the question,too much cost for nothing.
To clear things up my car is Row so the compresion ratio is 10.6:1 and the power rating is 163hp/205Nm.The 2.7 engine has 10.9 compression and 165hp/225Nm.
I wanted to keep the car 100% standard looking(sleeper) and get around 180hp from the stroker setup alone but it seems impossible so...
Anyway,i think the shorter rods is the better solution for a stroker instead of the special 2.8 pistons+turbo rods,it's more cost effective.
Another problem i think would be compression ratio for the stroker,if it's 10.6:1 standard what would it be after,i would not want more than 11:1.

FRporscheman

Without expensive race tuning, race parts, and race prepping/machining, just how much power do you think a 2.8L 8v can make? I bet less than 180 crank hp. Seems like a giant waste of money to me; for a 2.8 just the pistons and crank alone will cost you about $2k. An S2 engine is less than $2500 and makes 208 crank hp. I've seen 968 engines for $3000 not selling, and they make 236 hp.