weird dyno results

[firebird_1995]

ive got some graphs for you guys to look at and give me your opinion on. first, you'll notice only one graph that shows rpm in the lower scale, all others were in mph. when i asked why, this was the response...
"They didn't print in rpm since we were not able to capture an rpm signal. Some cars with high energy ignitions systems, ( some MSD ,Vipers, etc) put out a large RF/EMF cloud which runs the dyno nuts and we can't provide torque numbers which are computed with the delta velocity of the HP numbers taken from the drum. If you drive the car in the gear it was tested and have someone record the rpms at the speeds shown, particularly the peaks and valleys, you will have numbers for the trans guy to work from."
there were some issues getting a tach signal to the dyno computer, but i have some datalogs that im going to try and overlay on the dyno graphs to see if there is an issue with the trans, whether in the converter (blowing through?), unlocking and locking, or just clutches slipping, maybe just a tire issue on the dyno??? i dunno. on the #6 run i set the converter to lock as soon as it went into 3rd gear and stay locked which netted my highest hp (torque is not correct because of no rpm signal)

ill be posting the graphs in a second, i have to screen shot each one...

[firebird_1995]

Well I'm pretty sure I figured out why things don't make sense, car kicked down into 2nd gear.... anyway here's the logs
26" tire, 3.50 gears, and an 80e which has a 1.48 second gear and 1:1 3rd. At these mphs I was either in 2nd gear or slipping like hell.



1st run

Peak power at 85mph which shakes out to roughly 5700 rpms in 2nd. Data log shows around 6100

2nd

Short run. I remember this one winding up really quickly peaking here at around 5700 on my datalog.

3rd run


Winds up to 6300 then drops to 5700 which, when locked up equals 85mph. (I'm sure the fbody gears graph shows the mph values at 100% transfer, no slip).

4th run and the only one that picks up a rpm signal. I rolled into this one reeeeealy slow to prevent the converter flashing, wheelspin, whatever was taking place. ..



Runs up to 6100, drops 500 rpms climbs steadily briefly then jumps back up. At this point I pulled it off the dyno to try locking up the torque converter as soon as it goes into 3rd. I know that's considered a no no under power but at this point I felt that the converter was giving me problems, not the fact the trans was in 2nd...


5th and best run



Peak hp at around 86 on the graph, log shows this is my peak boost at 14# around 6300rpms. Not locked up

6th run


Basiclly the same thing but I come out of the throttle around 6100


So it really just looks like a bunch of worthless 2nd gear pulls at this point...

[MoeHorsePower]

Why are you making wot pulls in 2nd gear, you should keep it in the 1 : 1 gear. If you cant physically hear any engine sounds raising or lowering then it is either tire slippage or a bad converter.

[firebird_1995]

I was in third gear. I made sure to feel it shift into each gear as I brought up the rpms. I'll post up one of the videos Chris took that makes sense now. You can see the front end come up, settle down then come up again. Not sure if he would remember which run it was but it's not like I was intentionally running it in second.

[firebird_1995]

[SSlowBoat]

I was in third gear. I made sure to feel it shift into each gear as I brought up the rpms. I'll post up one of the videos Chris took that makes sense now. You can see the front end come up, settle down then come up again. Not sure if he would remember which run it was but it's not like I was intentionally running it in second.

I had that happen to me back when I had the 94. It kicked so hard into second it broke a dyno strap on on a dynocom dyno. What we had to do at dyno day was rip thru 2nd and let the car shift into 3rd gear. I was holding the mph at 95 on the data log (2.73 rear) and I forced the tune to keep it in 3rd, but it still would kick in to second.

I think because you were kicking down, you were having traction issues as well

[sweet-94z28]

Those graphs look like you are hazing the tires on the dyno. No guarantees, but I've seen that stuff before on nitrous cars.

[firebird_1995]

What we had to do at dyno day was rip thru 2nd and let the car shift into 3rd gear. I was holding the mph at 95 on the data log (2.73 rear) and I forced the tune to keep it in 3rd, but it still would kick in to second.

I think because you were kicking down, you were having traction issues as well

I think that's what was happening. Now that I look at the graph, datalog and video I can see where it's probably shifting back into 2nd, winding up, then going into 3rd then I'm letting out of it again. Damn...

[BLK WS6]

I agree the same thing happened to me once when I dynoed at a local car show...they wouldn't let me change the tune to lock in 3rd and it keep downshifting into 2nd.

[firebird_1995]

These guys were really easy to deal with. They allowed me to make some changes on the rollers. But with other people waiting I just limited those changes to the DFI (engine) PCM changes which can be made in real time. I saved the transmission changes for last after everyone else was done so if I bricked the PCM I wasn't holding someone up behind me. What problems were you having last year brad? It was similar to this in the sense that we thought you weren't getting traction on the rollers or something. Do you recall if you check to see if it was in 3rd gear or not?