Well
10-15 hp is alot.

Did dyno day a few months back. That day I tested my 944-spec prepared car with another 944-spec prepared car.

My car came 16 hp higher than the other car. Same dyno same day.

Here are my conclusions as to why.

The "other" car.
100% Stock motor... Stock air box, exhaust, chip, everything. Motor had about 100k miles and never opened. 1987 Vin number

My car
100% stock except for... Chip (Steve R) and Cat Deleted.
I had just finished rebuilding my motor and had done the following. (All stock, but still work)

1987 Head... completely cleaned and stock head job. The cleaning was from this rebuild and the head had been restored to stock specs about 30 races prior. I was also using newish (from rebuild 30 races ago lifters)

1984 Block... Cleaned with zero machine work. Original piston rings. New rod and main bearings. Block has some 140k+ miles on it.

Fuel injection and Intake.
Stock paper filter with stock air box. Cleaned throttle body to remove all dirt and grime other wise stock. Injectors clean back to factory flow specs. New copper plugs, Wires were old. Chip per Steve R. This was a left over from a friends 944-spec and I am pretty sure it standard upgrade with not special race updates. Car uses 91 oct pump gas.

Exhaust.
1987 Tube header, stock muffer, custom test pipe.

So
other than being cleaned, chip and test pipe it is of the same spec as the other motor and mine made 16 more hp at the rear wheels.

My feeling is tha about 10 hp came from the test pipe, 3 hp from the chip and 3 hp from the cleaned head, intake, injectors and engine block.

At one time earlier I ran with out the chip. The difference in power I noticed was quite small (back to back track day test). When I removed the cat I did notice a large speed increase, but this occured when the cat broke and I removed it and the muffler. So some of that feeling extra power could have come from the reduce weight. A dyno test by another driver reported no power change with or with out muffler if no cat was use.

I know other on this fourm disagree with my assesment of the power gain from a test pipe, but other 944 racer also feel cat removal gains hp. Chips, intake and even headers don't seem to gain much however. The owner of the other car was goning to just pull the cat and re-test, but I don't think that happend.

 

are the Steve R chips legal in 944-spec? I assume they are, but what gains are made by running it (asside from the 3 hp)?

 

944 spec allows any chip you want. You can replace the chip with custom burned on just for your car if you want. Gains are merely the 2-3 hp and no or raised rev limit.

Down sides are more money spent, potential reliability issues depening on the details of the chip and slightly more fuel consumption.

In my mind a chip is "nice to have" in 944-spec, but not a requirement. I personally like no or raised rev limit as much or more than than 2-3 hp. Reason is that while I shift at 6000 rpm 99% of the time there are always cases were in traffic you can "forget to shift" starts especially. Well if you don't hit the rev limter it better than the studder you get from banging into it. It sucks to drop back on the start because you hit the limter by accident.

 

Understood about stiffer springs as quicker transferers of weight, but they sure do a nice job keeping the nose of the car from dipping Had a real problem at first with the "one tire pinwheel effect" on the outside front. After we added the stiffer front springs (still mild at 200#) and lowered and stiffened the rear sway bar in one wholesale adjustment, the car stayed more level under heavy braking, allowed for a little trail braking without rolling over as much on the outside front and really hooked up better on exit, even if the tail was hanging out a little in the middle of turns.

I'll be first to admit I don't know exactly which part of our mod was the magic bullet but it has handled like a dream ever since.

And thanks Joe for the run down. Makes total sense to me. Again 10 - 15 hp from where I am now just on the intake and engine management side is becoming to sound like a very impractical target...but I will certainly enjoy whatever gains I can squeeze out.

 

I'm not sure about your mods, but what about removing power steering and AC, then underdriving your other accesories. Go to a lighter weight crank pully and flywheel. I'd be willing to bet that you can free up at least 10 hp just from reducing the engines parcitic and inertial losses.

 

Did the AC delete, it helped. Good call on the underdrive and lightweight pulleys!

 

If you have deleted the A/C the only accessories you have left are powersteering pump and alternator.

You can ditch the pump and put in manual rack and get less drag and also better feed back.

Not realy sure you will gain anything from an alternator pully change.

 

You'd see small gains underdriving the alternater, but more on the waterpump, and just lightening the pulleys. I've seen 10hp gains on Ford V8s with a kit from March pulleys (which are not that light).

 

M758.
how much HP does your spec car have?

 

134 rwhp (This was at the dyno day I spoke of above)

More charts are at

http://members.rennlist.com/m758/944SpecDynoCharts.htm

Unfortunatly I don't have my latest dyno chart posted.

 

Good info all around, guys. Hoping that the tranny swap will gain some of the time I'm searching for. As the attached pic shows, our autoX venue is wide open compared to most (Cumberland Regional Airport) and I've been getting caught on the rev limiter...too close to the gate to upshift to third...going both out and back. That dilemma alone could be a second of ET.

 

Do you have a stock rev limit? Can you install a chip? Maybe the better solution is to rev to 7k rather than swap boxes. Swapping boxes may hurt you in the slow corners more than it help at top end.

The other help could be 225/45 and 225/50 rear tires. Swap them to the 50's if you max 2nd. Use the 45's other wise.

If you only need 200 rpm more there are better ways than a complete gearbox swap.

 

Good stuff. Joe. Good price NA chip sources? Tire swap deal is a good idea, too. Need to find a friend with 50's This makes good sense in that I probably am only 200 rpm over at the top of second gear.

 

Sorry, I forgot to mention FR Wilk makes his PP2 chips with 6500 or 7000 rpm rev limits. If you have an "early car" he sells an adapter to allow the chipping of the early DMEs which others don't. If you go to his web site it will answer your questions.

http://www.frwilk.com/944dme/

 

The pulleys really dont weigh that much on the 944/951 IMO.

Dumping 18lbs off the flywheel/clutch (possible with KEP PP and fidanza flywheel) should have a HUGE difference if you can notice anything at all from taking 1/4lbs off an accesory pulley. Though in reality, I dont think the 18lbs off the PP and flywheel has much of a noticable effect in acceleration.