Racepac graph

[1972ho]

I’m not sure if this is a problem but my drive shaft graph (in green)(red is rpm)for every run no matter what engine combo I have run in this car has always shown this peak after every shift. Does this mean that the tires are spinning on the shift are something else.

[fastblackracing]

Very interesting breaking the graphs down....
What trans and converter, Tire and air pressure, shocks and spring setup?

Also what is the third trace, and do you have a g-meter? How many magnets on the shaft?

There is a slight drop at first which can be clutch slip or a shift timing issue in the trans,
and then the increase which can be shock loading into the tire causing it to compress and or
some real tire spin.....

Then the second drop in shaft happens which can be the tire coming back into normal
and the converter could be loading up and bringing the engine down just a bit.

The 2-3 looks a bit different in just after the shift there could be some bounce going on for
just a bit causing several small spikes from the chassis unloading?

How fast and how do the time/mph increments line up? (60, 1/8, 1/4)

Very cool set-up, I need to work my into one some day.

[1972ho]

This is ford 72 mustang coupe with a stocker cleveland engine with a ATI 8 inch 5800-6000 stall converter with a set of Calvert shock rear with leaf springs and QA fronts double adjustable,Hoosier 29.5 x9 slicks with 18-22 psi air pressure,and this has been happening for years I just thought I would post it here to see if anyone else has seen this on there racepac.Thanks

[CamKing]

What RPM is the engine dropping down to, on the shifts ?

[1972ho]

The above graph is not the cleveland engine but a V-6 But I get the same spike on the shift with either engine,the v-6 converter is looser than the Cleveland So the rpm drop is a higher rpm 6300 plus,and I shift it higher than the Cleveland.8000 plus for the v-6 and 7500 for the Cleveland but the gear ratio I’ve run is 5.29,5.43 and 5.57 and it spikes the same.

[MadBill]

Wheelspin should spike up the revs, then quickly trend back to the base curve. Since the RPM spikes up, then down below average, I'd guess it's registering momentary wind-up/unwind in the driveshaft and/or axles.

[Amilcar]

It appears to be the axle rotation(pinion going upwards), as you described not be a four-link/ladder bars suspension.

MadBill beated me on that..

[1972ho]

If that’s the case is there anything that can be done to stop this from happening,and I wonder if I’m leaving any et on the table.Plus I’ve never seen this on anyone else’s driveshaft graph.Thanks

[In-Tech]

Is it the tire winding up or slipping?

[MadBill]

If that’s the case is there anything that can be done to stop this from happening,and I wonder if I’m leaving any et on the table.Plus I’ve never seen this on anyone else’s driveshaft graph.Thanks

From the trace it looks like most of the +/- energy spikes cancel out, so the main effect might be just less shift-induced shock loads on the rear end.

[Kevin Johnson]

Racepak has a collection of graphs with explanations of what they represent. Just a wild guess (?) but they might post yours with an explanation as well.

[krisr]

That looks like signal noise to me - if it was a traction issue you'd see the RPM trace spike too. What sensor are you running? Is it a magnetic or hall? Have you twisted the wires all the way from the ECU to the sensor to help with shielding or is it a shielded wire?

[Kevin Johnson]

I am guessing you are running a C6. Look at methods to remedy a slight amount of flare. Just a thought.

https://www.bobistheoilguy.com/forums/u ... er=3071742

https://en.wikipedia.org/wiki/Hysteresis

You can see the lag from the engine rpm waveform to the driveshaft rpm -- hysteresis?

[matt69nova]

Racepak has a collection of graphs with explanations of what they represent. Just a wild guess (?) but they might post yours with an explanation as well.

Kevin, where would one find these graphs? I poked around on Racepak's website, but couldn't locate them.

[Kevin Johnson]

http://www.motorsportsinnovations.com/R ... p-tips.htm Look at 23.


http://www.motorsportsinnovations.com/L ... 20Logs.htm

I am just assuming that the two businesses are related.