Lemming

I alluded to my most recent dyno runs in another thread. This winter I did a complete reseal on my number one engine ('95). When I got the engine it had around 60K miles and was used for one track season before it developed numerous leaks. On doing the reseal, I pulled the oil pan to inspect the bottom end, and found a cracked oil pick up tube. Glad I didn't run the engine in season two or I might just have lost it. I welded the tube, hopefully it will last!

So, I'm going W2W racing in the GTS challenge this year (first race in less than 2 weeks). Had to get my official dyno which is shown below. I'm running the RS barn chip (II) and header, with an open 2.5 pipe going into a Supertrapp muffler. The red line is with the open muffler (no discs) and the blue line is with 16 discs (which is the most suggested before just going with an open pipe). I'm pretty happy with 226 rwhp

I know, I know, numbers very for numerous reasons. My last dynos in 2006 were in the 218 range and that was running the same chip and header but with the muffler suggest by RSbarn.

FRporscheman

Wow, that's a nice lump of power. Also, the torque is not far behind, while in a stock motor the gap is a bit bigger.

Remind us how much your car weighs?

H2

Tim,

It's good to see honest to goodness dyno sheets. Beats my seat-o-meter. Thanks for posting.

Harvey

A.Wayne

Tim what engine are you running ?

Lemming

Arash - the car weighs in at 2,500 lbs with me, all gear, and a 1/4 tank of gas.

A.Wayne - '95 968 engine.

Harvey - not sure why folks on this board will not post their dyno sheets.

I did some crappy body work on the car to repair the crinkles from hitting the wall at Road Atlanta a while back. I then had to repaint to cover the bondo My stepdaughter loves the movie "Cars" and she convinced me to put a big lightning bolt of the side. I'm not feeling the new paint job but if it makes her happy and she comes out to the track to see me, then it's well worth it.

RajDatta

Thanks Tim for sharing your dyno. What muffler are you currently using.
Raj

Lemming

Supertrapp http://www.supertrapp.com/product_se...temID=549-2519

I bought this style so that I could play with backpressure by the addition or subtraction of end plates. Turns out that the best power comes from 0 plates (wide open). The addition of 16 plates (which the company says is essentially an open pipe) cuts power by 10 hp. Go to 10 plates (more back pressure) and the drop is another 10 hp.

Without the end plates the car is loud, basically an open test pipe. I'm planning on running that way unless I'm black flagged. In that case, I'll put 16 discs on and run with 216 hp, but less noise.

I think the car will be competitive in GTS 3 which is based on wt/hp; the limit being 11 for my class. At 2500 lbs and 227 hp, I'm at 11.01. I might add some weight for a slight bigger safety margin. GTS 3 seems to be dominated by the E36 M3s.

RajDatta

I think you meant that adding 16 plates acts as a very restrictive muffler, not an open pipe, correct?
Its seemed contradictory to your above statement. Let me know if I misunderstood.
Thanks for sharing.
Raj

Lemming

Adding plates increases the area for gas to escape. 1 plate is very restrictive, 16 is what the company considers to be nearly an open pipe. 0 plates is an open pipe. Hope that helps.

Lemming

Forgot to mention that I also installed a Spec lightweight alum flywheel and new Stage III clutch

RajDatta

I get the concept on plates now, makes sense.
Was this through Lindsey? I know they have carried Spec flywheels over the yrs. How do you like it?
Raj

Lemming

I bought my first spec stage III through Lindsey and then found out that Spec is based in B'ham This time I just stopped by the shop and bs'ed with the guys for a few hours. 24 hours later, I had the new flywheel, clutch, and lightweight pressure plate for about 60% of list Of course, the discount is costing me a number of test rides the next time I'm instructing at Barber (but's that's ok). It didn't hurt that one of the guys at the shop has an S2 with LS1 engine tucked in it.

I really like the clutch. Turns out that I had a flywheel failure earlier this year (snapped all nine bolts going to the crank) and the flywheel than damaged the clutch and pp. They measued the clutch and over two seasons I only used 5 thousandths; which blew the spec guys away.

I had to increase the idle to keep the car from stalling. And yes, I do have the S2 harmonic balancer.

300guy

The PDF tuning guide for your muffler suggets that 20-24 disks are required from an "open" type muffler.

Would you recommend this muffler for an application for both street and track as the disks could be subtracted/added accordingly?

There is some muffling effect when running no disks correct? (the muffler has internal packing)

What is your next step? or are you going to concentrate on tuning in other areas?

Lemming

I have not seen the PDF tuning guide, will look for it. I spoke with Supertrapp and they suggested that over 16 discs it was best to just run it open.

Street and track; possibly, however, I would not want to be running more than 10 discs or so on the street because of the noise.

Yes, I'm sure that there is some (but very little) muffling when running with no discs as there is packing, but without back pressure, I don't see it having much of an effect.

I don't really need to go any further with HP, otherwise I will get bumped up to GTS4 and I don't want to be there. Still working on optimal wheel and tire size that will keep me in my budget. Also looking into some downforce as well.

300guy

Do you have a dyno graph with 10 plates installed?

What is the sound like with the 10 plates? Nice resonance or choppy?