BReif61

In September, I bought a 944 (impulsively, I should add) that is already supercharged. I do not know if it is a "kit" or something that someone pieced together, but it is a centrifugal blower parked where the AC compressor should (?) be located.

Here are the high-points of the set-up.

**EDIT**
Supercharger appears to be the SFR "stage 2" kit. By rights I should be seeing 8psi by their website. That might need to be increased pending the results of my internals investigation.
-Unknown centrifugal supercharger (I can double check when I get home, looks like a Vortech)

-Vitesse MAF
-Vitesse SMT6
-55lb injectors
-"turbo spec" rebuild
-Zietronix WB02

Now, this is where the questions come.

1.) The PO says it has been rebuilt with OEM Turbo pistons. Is there any way to check this, short of tearing the head off? Are the domes significantly different, ie enough to tell the difference through the plug hole?

2.) Tuning this thing has been a nightmare. I get that the "analog" table adjust the MAF signal that the DME sees, and that I have to pull signal (neg. value) to reduce the injector duty cycle and not flood the engine.

However, the analog chart is all negatives as expected, but the global fuel compensation is +20. This is completely against any logic in my head.

I drove the car for 5hrs without any catastrophic issues, but noticed a few things. First off, it runs stupidly rich. Secondly, it bucks with partial throttle. Adjusting the fuel mapping will improve the AFRs and help with the bucking, but with how counter-intuitive the SMT is, I want to get some advice before I start playing. Can anyone help with this? All the searches are dead-ends.

3.) If I decide to scrap the SMT6, what is the Tuner duJour right now? I like the adjustability of the MegaSquirt, but then I know there are various Rogue kits as well as other options. Based on a price/performance view, what is best for a mild street car?

83 944

actually you can check the pistons with a bright light in the spark plug hole. and you will notice if it is more domed it will a little hard to tell but you can. that will be the 951 or turbo pistons for the lower compression. if they are flat topped then they are the n/a pistons.

and as far as the tunint i have no idea hopfully someone will chim in soon. have you tried a local speed shop that tunes, dynos, etc? maybe is worth paying for it. also LR has a computer software free on their site to help with tuning yourself.

good luck and sounds like a sweet car.

odurandina

do you have AAA towing services ?

V2Rocket

the rogue kit will help you tremendously - no more fooling with signals to make things seem right. reasonable pricing and a very helpful guy.

JohnKoaWood

Change the compensation value to +3, and try again...

0 would be perfect, but +3 is a basic starting point...

N/A piston


Turbo Pistons


you should be able to sdiscern the dome pocket shape looking through the plug hole... cheap borescope camera will help!
http://www.harborfreight.com/digital...era-67979.html

V2Rocket

looking at those pistons brought a weird idea to mind - i wonder if you could drop CR anything noticeable by taking some sandpaper to the domes/flat faces

odurandina

shorter rods.

V2Rocket

that can create problems in itself - that would for one open the quench area around the piston edges up a more significant amount (ideal is about 0.040"). not to mention part of the vibration problem of 4-cyl inline engines is related to the rod length; the longer the rod the more manageable the vibration.

that's why when guys do 2.8L strokers they have custom pistons made with the pin heights raised rather than using short rods.

odurandina

Cunningham used to make a set of slightly shorter rods for our cars that worked great for supercharging and turbocharging between 8~10 psi..... if only supercharging worked.....

Olli Snellman

Junior checking his 951 engine

BReif61

I'll give that a shot. I still don't see why it shouldn't be negative? That would improve the idle (below the altered fuel map) and the cold performance by allowing the DME to think the injectors are stock?

See attachment for current (PO) tune.

BReif61

Oh, and here's something for you guys to ogle.

m73m95

Really bro?


Go over to Pelican and check out Sid's "Lil'Mule", and see what supercharging a 944 can do.

V2Rocket

ever heard of a P-51?

blown 944

Personally I'd move the throttle body to before the blower. Having instant pressure in the boost tubes requires using a bov at lo low spring pressure.

In regards to tuning, things have come a little ways in sure since this was put together.

I'd contact rogue or vittesse, either way you want to have a map sensor in the system to adjust timing. These two things should get you running pretty good. Josh (rogue) did a custom maf setup for me that idled perfect and had great afrs throught the rpms and boost.

I've since decided to focus on one car do the sc car is gone. But I do miss the way it took off