hacker-pschorr

One of these trips to the dyno I'm going to try doing a run in reverse.

Might come in handy knowing how fast I can get out of trouble............

Lizard928

the losses in reverse will be higher.

Iwanna928

Don't forget your video camera!

James Bailey

Correct due to the reverse idler power must flow through another set of gears which means more losses to heat. I however see little difference in using 3rd or 4th gear, power must flow off the input shaft and then back to the pinion shaft so two sets of gears in each. Only 5th has a direct shot no gears at all and less power loss!

RKD in OKC

Well, here is the chart from the two runs...



Discuss on how after 5.25K it matches the power of a stock 91 GT?

SeanR

Damn Richard, my auto S4 will walk all over ya

I'm jokin of course.

Speedtoys

My AutoS4 put down more HP, you got 15 more torques however.


???

Lizard928

wow, that falls off pretty quick in the upper RPM.

Your AFR looks pretty leak in the top, but the tail sensors normally read a little leaner. It is possible it is going too rich and dropping power.
Or it could just be the GTS camshafts. I havent seen enough GTS dyno charts to compare to.

RKD in OKC

Here is a comparison to a 91 GT with and without flappy...



Maybe my flappy is only flapping part way?

Speedtoys

Looked like it opened slowly too. Here is my 88S4 Automatic after a top end refresh.

Bill Ball

Not enough dyno tweaking.

IcemanG17

By far the most powerful $4k 928 ever!!!

SeanR

Richard, have you had the Hammer on it to check that everything is working. I'm wondering if you are getting timing pulled back from a bad knock sensor or hall sensor.

RKD in OKC

Honestly, I was expecting 300 rwhp with the x-pipe, race cats, and RMB. Sure explains why I am getting beat at the autocross.

Oh yeah, the PSD light was on while it was on the dyno and rolling. Operator asked me if I could turn the traction control off because of the light. Was okay with it when I told him it was just the locking differential.

Flappy was working and got a good hammer last summer when I did the intake refresh and checked the tune (I thought it was running rich, but is was running lean). My wrench suggested a new MAF then, but the A/F doesn't look bad enough to me to cause that much power loss. Guess something could have died over the winter.

I am not going to do the cam upgrade I was planning on until I am positive everything is running as it should. That was one of the reasons why I did the pulls today, to make sure it was good to go. Another reason I am a little disappointed, pause on the cams.

Got some wrench time scheduled for next week to plug in the hammer and check everything out.

Rob Edwards

Just as a(nother) data point, here are William Anast's stock '93 GTS 5-speed dyno curve, back in May 2010. So Richard's '94 is right in the ballpark:



William's car is in excellent shape, maintained by Greg, etc. so I think it's safe to say that the engine was running as it should. I bet Richard's is as well.

Then swapped on Greg's then-new headers and exhaust. The difference, to my uninformed eyes, says that GTS cams do not play well with the factory S4+ exhaust. I'd be interested to hear why people think there's such a difference? Restrictive manifolds? No crossover? ??? But Richard's got the X.. Hmm.