blitz928

Yesterday's Dyno runs.

www.smithmotorworks.com Mustang Dyno, Outside temp 89, 87 S4 Auto, 142k miles Stock , except no air pump, no cats, new Bosch #556 4 hole 19lb injectors and RMB. I did 6 runs total all were +/- 2hp. Pulls in 3rd gear

Average was 268hp 289tq

and a video...

IcemanG17

Nice....strong #'s for a auto!!! That equals about 335 crank HP!!!! You have a well running 928!!! My only "concern" is the slight flame on decel....your idle switch may not be working...but its easy to check

blitz928

Dyno operator mentioned that A/F was rich in the high RPM. Could do better, I was wondering what caused it. I don't have the chart in front of me. I've read that many 87+ get rich on the top end, it's "safer" that way. He mentioned it was strong S4. Especially the torque curve.

Is there a procedure to check the idle switch? I'll check the WSM.

pcar928fan

My S4 is stock (RMB and old AutoThority chips...but decent ones...vs. the ones in the car when I bought it which SUCKED!) we make almost identical HP but you have probably 20 Tq more than me! That is VERY SOLID! My S4 is also auto and has 90k miles on it (10k track miles).

IcemanG17

very normal....most S4's with higher flow exhausts tend to "dump fuel" as the rpms increase...however my stock 88 automatic (only RMB) had a nice slowly dropping AFR...from 13.5 @ 2500 to 12.2 @ 6300....

If you look at the stock fuel maps in sharktuner you can see how the fuel really ramps up at higher load levels (MAF reading)...

Sure you could gain a few HP by leaning it out....but I wouldn't....the difference between 12.0 to an ideal say 13.1 isn't much for the increased risk of detonation....

IcemanG17

almost forgot....typically the idle switch itself doesn't fail, the throttle cable tightens up to the point it won't engage....the easiest test is to turn off the enigne in a quiet space (garage) and slowly move the throttle off the stop...you should hear an audible "click" from the TPS (throttle position sensor)....if there is not click try loosening the throttle cable....that should fix it

blitz928

Dave at Smithmotorwoks agreed, You could tweak it and gain on a few HP on the upper end, but It's safer to be rich at high Rpm, off idle was normal 13.9/1 . 2500 13.4/1 by redline it was about 12.1/1, My torque band was very very good and I don't think I'll mess with it. The car runs great and am happy with the results.

I'll check the idle switch contact. Thanks for the tip.

IcemanG17

I'd leave it

In general there is little to be gained by "tuning" a stock car....they are pretty well setup by the factory (with some exceptions like 85-6 conservative tune)

Iwanna928

Congrats on your dyno run! I think its a fun way to spend some time!

Thanks for the video!

blitz928

Tim Murphy

Nice video, can't ever get enough of those!

Looks like a strong car for sure and good advice all around given above.

I noticed right at 57 seconds you might have shed a wheel weight off the left rear. Something you might want to check.

Great looking car!

Tony

looked like 1/4 or 5/8 oz from the opposite side of the valve stem.

damn near killed the mosquito flying by!




Love the little flame pop at the end. This one thing i love wth the Sharktuner...i disable the fuel cut of under deaccleration and it creates a wonderful muffled poping..through the exhasut (x pipe and RMB)

blitz928

You guys have good eyes.

c_span

I was told one way to check was to set the digital display to instant MPG readout, when you lift off should go to 90MPG.

mark kibort

the idle switch doesnt come into effect unless your foot is totally off the gas. on a dyno run, you might have had your foot resting on the switch. if it is still popping as you get to the lower RPM on decel, the switch is not working. I have mine selectable to be turned off and on. on the track, you dont want that switch engaged. (i.e. no idle switch). all it does is cut off fuel when you are off throttle, until you get to idle speeds where fuel is then added to idle.
great numbers for an auto!

I did like the little flame pop! cool. fuel looks ideal, I wouldnt worry about it.