Courtshark

I think my 928 took Veteran's Day off. I took it out to get dyno'd today, mainly to check on whatever gains I may have picked up by installing the Devek headers and free flow exhaust. Other than making my car ridiculously loud, it seems I've not gained much if any power. Seat of the pants dyno says otherwise, but the numbers don't lie. I don't have ther graphs yet (waiting for the shop to email them to me) but my peak numbers were around 272 hp and 280 ft. lbs. Stock was 262/271 and that was letting off at 6k rpms. These runs were out to 6800 rpms.

Any ideas on possible causes? Perhaps the gas stations here are already supplying winter gas? The car doesn't seem to drive any differently than before; it was the exact same dyno & operators (dynapack chassis dyno). A/F ratios looked good. A little lean at the peak hp, but nothing to get bent out of shape about.

To top it off, on the way home, I came across an Evo 8 and a new Hemi Charger at the exact same traffic light, all of us in the front row, and with a nice wide open road in front of us. The Evo starts to rev, and I can hear his blow off valve wooshing. The Hemi revs, too... light's green, time to go... and I got totally smoked off the line (I didn't rev at all, just mashed on it after a brief slow roll so as to not smoke the tires). I caught up to the Hemi, but the Evo pulled away hard until I hit 3rd gear and 100 mph. He didn't get further away, but I didn't much close the gap either. We both backed off at about 130 mph. The Evo guy was nice; TG it's not stock. Running 22 psi, with some exhaust work done, too. Wow was that thing fast. Handled well, too. The Hemi was all over the road. I'm sure both of them are posting right now about their Shark dinner.

Time for a Supercharger... or turbo... and definitely a new set of fuel chips here soon.

Rant over.

ErnestSw

Every exhaust set up is a compromise. Your wide open exhaust is optimized for top end. You MAY find some significant HP with a Sharktuner.

pmotts

What is the exhaust set up after the headers?

Richard S

Devek level 1 or level 2 headers? With level 2 common rwhp is low to mid 290's. Dennis and I have level 2, into single 3.5inch pipe with Borla mufflers....similar rwhp mid 290's.

Rich

Courtshark

I have exactly that set up. Devek Level IIs, single 3.5" pipe, and only 1 Borla.

John Speake

Mike's car is an auto...... this might explain the lower rwhp ?

Rick Carter

Check the cam timing and WOT switch.

AO

Dyno rule #1: Always post what brand dyno the test was run on and the correction factor. These two seemingly uninportant things can make a 20% difference!

Secondly, 272RWHP (assuming 18% loss) gives 331 at the crank which is 11HP higher than stock. I'd say you're doing okay. Your car can obviously exhale... now you need to help it inhale!

Lastly, S4 redline is 6600, so double check your graph (whe you get it) to make sure your dyno operator didn't make a mistake in calibrating your RPMs.

Courtshark

#1: It was a Dynapack Chassis Dyno. (that's mentioned in the original post) using SAE correction. It's a great dyno set up, actually, where the dyno is bolted to the rear wheel hubs with the wheels removed. No giant rollers to mess with, and no strap downs, etc. I did my baseline 262/271 runs on the same dyno at the same shop with the same operators.

#2: headers and a 3.5" single pipe should give me more than a 15hp bump, don'tchya think? Others with similar setups (see above) are seeing closer to 290 at the wheels.

#3: drive ratio was calibrated twice during testing.

Bill Ball

And add in the Hall sender and knock sensors! Time for a Spanner and a Proken cam timing check tool.

Courtshark

Sounds like I need a "fix my shark" party on this one... willing to travel....

drnick

i bet you will find a lot more if you shark tune with those exhaust mods.