The 2700 spike is from the chipset. I am almost certain that is is mixture of science and marketing - this is how they make sure you feel a seat of the pants improvement so you will be satisfied with the product. Maybe risk of the effects of detonation is lower at lower RPMS? I am not much of a science guy, but have an abundance of curiosity. Anybody know the scoop on this?

It would be interesting to see the Air/Fuel measurements along with the torque curve.

My dyno chart and another chipped '85 had the same early peak. Strangely enough, though, my real peak torque was right there at 2700 and it never got even close to that except in the 4200-4600 range. I wonder if it is your exhaust mod that is helping to carry higher torque numbers at the mid to high RPMS.

We all did 3rd gear runs at Chris' 928 Dyno Day last month. I do not fully know what the rationale was on this. If you go 1st or 2nd gear you may have to cinch the car down pretty hard to avoid potential wheelspin??? 1st or 2nd gear runs would be of rather short duration to get through the RPMS and less data could be recorded.

 

Not being a science guy, I am not a quotable resource, however it stands to reason that Mark is correct. Crank to measured rear wheel losses must include everything including the clutch, transmission, etc. Your 25hp is only part of the magic loss number.

 

James,
Actually I got an e-mail from a very knowlegeable Rennlister with the following quotes - very cool I thought.
"The torque curve now has a nice, fat hump at a very usable 2800 rpm, and
it's both flatter (overall) and higher on the scale than the 4.7-liter
engine's output curve." -Car & Driver 2/1985
"Although the 302-pound-foot peak occurs at a relatively low 2700 rpm, more
than 250 pounds-feet is on hand from 1300 to over 6000 rpm. Most 5.0-liter
V-8s do well to exceed that level at any engine speed." - Car & Driver
-5/1985

 

Warren,

I would find a place that has a dyno jet and reads A/F and give it another shot before being too down. I have heard many times the Mustang dyno's read low.

 

Warren,

The owners manual has a graph of factory HP and torque curves. Our stock torque curve is pretty generous in that early range to start off with. It would appear that the chips's enhancement turned the early hump into an early "volcano" (slight exaggeration on size, but very descriptive of the shape with steep slope up and down).

Whether the Dynojet reads high or the Mustang reads low - I don't really want to know. But a consistent difference seems to exist between the two. Don't quote me as my memory is not perfect, but I seem to recall Marc Thomas (Devek) some years ago mention something about higher HP measurement accuracy issues on the old Mustang dynos and that Dynojets tend to be calibrated fairly consistently so each unit will provide similar readings. Not sure if we qualify as "higher HP applications" or if Mustangs dynos have improved over the years (they probably have).

 

i think i ran315- 318hp to the wheels on a mustang (tom's) and a season earlier, ran 320 on a dynojet.
on a dynojet, there really is no calibration. you run the drums as fast as you can, and that acceleration rate baced on their weight and diameter tells you HP (rate of acceleration )
mustang dynos are a little different and I think there are more factors in priciple to calabrate, but dont really know.
SAE calabration and adjustment is different as you know

mk

 

Thanks Jim. Unfortunately, we only have the one Dyno in town - this one being brand new.
Re, the A/F, I am now looking for a A/F meter to purchase and install. I have been looking at the ARM-1 but wonder if there is one out there that actually accurately gives a number for the ratio.
The owner of the Dyno said that nearly every one of the vehicles that came to his Dyno (about 10 I am guessing) showed quite a bit lower than spec and anticipated. Obviously, in many cases this will be related to people being overly optimistic but he seemed concerned about his Dyno's accuracy and low readings. He was a great guy and said that if he finds something wrong, he will call me and give me another go - no cost.
I am going to try a few things and then give it another go in a month or so. I am going to try it with the old chips as well for comparison.
As always, I really appreciate all of the comments, suggestions and support given here.

 

if you are getting 240hp at the wheels dyno jet or mustang dyno, thats in the neighborhood of 282hp at the wheels. sound about right, minus the missing rolling friction. if you did a coast down, minus what i measured of 10hp from 80mph and 20hp at 130mph from your coast down numbers. (should be less) net could be 5hp. so, still in the 280 flywheel range. not too far off.

mk