Tony

We got Dariens car on the dyno today for the first time. We never did a baseline run before the install so for comparison you can use a run of the mill 86.5 for a baseline.

The chart is below.
156K miles as driven daily
4spd AUTO
appx 9-10psi
All runs in 3rd gear...pump gas..H pipe with glass packs(my old one that made 400rwhp)...RMB

Obvious issue in the midrange with somehthing??? .
Plenty left on the table..im guessing he has 375 in there somewhere.
The chart is so nice and smooth then it goes to crap!

The differnce betwen run 1 and run 2 was 1 turn inwards of the BEGI bleed screw, thus raising the final fuel pressure and some HP/TQ.

The AFR was measured at the tail pipe and tends to read on the lean side when compared to my LM-1 wide band during my runs.

From the sound and what i saw as the car was running, it ran fine. (video to come i think) No smoke, no misfires, no belt dust, that obvious stuff. Nothing outward that would cause the drastic drop offs in the chart.

Anyone have any ideas.

We are thinking along the lines of tranny slip in 3rd gear.
As i say this we perhaps should have done a pull in 2nd gear for a comparison. Darien said he could feel a "lag" in power at the top end.
Any input is welcome as always

Fabio421

Any psi numbers during the dyno?

Darien

Nothing accurate today, we checked it when we installed the new pulley, it was showing 10psi.

Jim_H

Tony,

If the clutch was slipping you would probably here it rev up a bit and I doubt Darien would notice a drop in power at all.

Jim_H

More on the clutch. I have had motorcycles and cars with slipping clutches and I would expect it to wind up if it was slipping. It should have felt like it was winding easier instead of a loss of power. At those R's you probably should have smelled clutch also.

Darien

Jim, good point. It didn't feel like it was spinning easier. Sitting in the car, it almost felt like the dyno rollers were getting stiffer

The leveling off on the print out has me concerned. I've kinda noticed it on the road as well. 1st and 2nd are very torquey and very quick, if I'm crusing at 60 mph and drop her into 3rd, it's noticeably slower to gain speed.

Tony

If i would have thought we should have tried it in 2nd gear. I know the guy would have let you do a free be to try and sort it out a bit.
The inner workings of the tranny are a mystery to me, hopefully Steve C will chime in.... I assume there is a seperate engagement band for each gear?
..is there only 1 clutch pack in an auto or one for each gear?
I really dont know?

Bill Ball

Darien: My road feel in 3rd gear is like that too, but my dyno chart certainly doesn't look like yours. That is a very pecuiliar looking curve. Something is dying at 4700 RPM. It sure looks like some kind of wheel slip at the same point, as the curve come together after that.

Shane

Looks like it is getting starved for air at the upper end. The only other thing I can think of is the vacuum signal to the brain.

Darien

We actually had to adjust the begi a little richer. Hadn't thought about vacuum..

AO

Fun chart... I can't wait to have a "problem" going from 350 to 375!

Jim_H

This is an auto??!! Throw out everything I said, I was talking in terms of a manual. Don't know why I thought it was a manual
Sorry

I have to say that I noticed a big difference after I changed the fluid and filter in my old S4 tranny

Bill Ball

Sure, the drum feels stiffer - Your torque is dropping off the map and your HP has leveled off.

You have new #30 injectors and extra fuel pressure and the boost held, right?

No pinging? It looks like the timing went retard, but you don't have knock sensors, right?

Eh, when did you last change the fuel filter? I would expect it to go lean, but....

Darien

Bill,

I'm running motor sport 24lb injectors, we set the fuel pressure at the stock idle setting.

Timing is what the guy at the dyno thought as well, but I guess that's not adjustable.

I changed the filter within the last 10 months.

I sure hope we can figure this one out

Jim_H

You will.

Points & cap are fresh

Could a weak coil be the cause?