Courtshark

Dyno day was kind of a dyno bust. The weird weather was a harbinger. Awoke to fog, which gave way to bright sun and temps in the 60s, and then while DonT was on the dyno, the sky opened up with cold temps and showers that persisted throughout the rest of the afternoon.

DonT, Glenn, tomcat and myself all had 928s present (Glenn, that Strosek body is gorgeous!), and DonT and I dyno'd our rides. My father (93 C2 cabrio) and brother (brought his 91 Saab 900 turbo convertible) also attended, and dyno'd their rides. Dad's C2 is pretty much stock, and I think it put down around 217. My bro's Saab is mildly tuned (16 psi of boost, RRFPR, Stage II APC engine management system; it's a plug-and-play box) and put down around 175 hp.

I'll let DonT post about his results, but let's just say it was lower than expected.

As was mine... somehow my torque figures rose (277 ft. lbs., up from 271) but my hp went down (from 269 to 264 hp). That explains the small seat of the pants increase I noticed from doing the chip work, but I definitely expected better numbers based on the car's different driveability with the chips. Very odd. I did 5 runs in all, and they were all very consistent. Air/Fuel looked good. A little rich on the top end but nothing to get upset about.

So... is it possible that my exhaust (Devek Level II headers, Y pipe, 3.5" straight flow, no cat, 1 borla muffler with 3.5" in and out) is just too wide open? My car is certainly louder than all get out, which is so friggin' obnoxious now that it's not really for any reason! (No power gains come from it, apparently) Right now, I'm thinking either I go back to stock, or I try putting a high flow cat in line. Suggestions welcome! Man, this is frustrating.

And please see my other post re: rear turbo-ing

IcemanG17

Mike
Of course I just posted to your other thread about the dyno #'s......264 or 269 whp is within the normal range...keep in mind with the standard .8 automatic loss thats 330 to 336whp....or quite a bit better than stock......BUT since you are running headers and full 3.5" exhaust.....but you should be closer to 290whp with that setup.....most S4's with the same exhaust setup dyno around 290-300whp....

Something must be off a little bit......how is your cam timing? Darien gained TONS of hp getting it just right?

FlyingDog

Cam timing? Something forcing ignition retard? Bad MAF or O2 sensor?

Courtshark

If the MAF or o2 was bad, wouldn't my idle stink? The cam timing issue sounds like a winner... I'll have to do some digging there.

FlyingDog

MAF or O2 could just be a little off and cause a huge drop in power.

Louie928

I don't know how many times I've said this, and few listen. One more time. First make sure the engine is performing as it should and dynos in the normal range. Your best performing exhaust on a 32v 928 is a Dave Lomas X pipe and no more than 2.5" dual pipes. If you use stock rear pipes the GT style with the small mid resonators and the rear muffler works well, otherwise the larger S4 style mid mufflers and a RMB. Use any straight through (not Flowmaster) muffler. Forget chips. Do a Sharktune. A 5 spd S4 will do very near 300 rwhp. A GT about 315+. Automatics a bit lower.

marton

Did you try the dyno with your old chips on the same day for comparison?

Marton

Courtshark

The chips were the only change I'd made to the car since the last dyno runs in November. I'd only driven the car about 500 miles since then, too.

Courtshark

Hmm... duly noted. Sounds like there's a need for a fix-my-shark day.

DonT

My HP & torque numbers were definitely less than I anticipated. I talked to Tim Murphy today, and we discussed my dyno results. There were some car issues, NOT supercharger problems (i.e. vacuum line to FMU - disconnected, loose clamp connecting SC to air tube).

The concensus - time to replace the MAF. I have a NEW one in my Shark spare parts room.

Courtshark

I wish I had a shark spare parts room. And definitely one with a new MAF in it. I think I might be needing one, too. (see above)

Glad you got it figured out (I/we hope). SSI would love to have us back whenever we want.

mark kibort

someone better start doing some coast down runs. im thinking a lot of variation is how the cars are being strapped down. easy to prove and could be a big variable.

mk

mark kibort

mike,

tell me the difference of the car before and after this dyno. exhaust, headers, what did you change?

generally, always a hp gain to go to more open exhaust, but sometimes the peak torque can go down with cams or open exhaust.

Mk

FlyingDog

Mike, I just sent my spare MAF out to be rebuilt. If we have a chance to meet up before I install it, you are welcome to test it in your car.

Courtshark

Thanks Matt! I'll see if I can hold out. Keep me posted on when it comes in.

Mark, no need for coast-downs on this dyno; actually, not even sure if it's possible. The cars aren't "strapped down" but rather bolted to the dyno. The wheels come off, special hubs go on, and then the hubs fit into the dyno pods.

My runs (from memory; I could be off by a nuymber or two here or there): Dyno 1 was stock, last April, 262hp/269 tq; Dyno 2 was November, post headers/3.5" exhaust: 269 hp/271 tq; Dyno 3 was yesterday, post AA chips, 265 hp/277 tq.

I think Matt may be right that one or more of either the MAF, cam timing, or o2 could be off/bad. What do you think? I'll try to get the charts up soon. The shop is a little slow to email them to me sometimes.