I went to the track Saturday, after getting my car dyno tuned with custom chips a couple weeks ago. I had the injector pulse widths down in the low 9ms range. At the track, they were up in the 10ms range! What gives? It was cooler at the dyno than the track.

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West Coast GM Shootout 2001!
1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

what were your times last weekend with your hotcam?


James

 

It may have been cooler at the dyno, but what were your MAT temps? I find just sitting in one spot also causes my relocated MAT temp to rise. Also, elevation has an effect too.

Lastly, what was your coolant temp at both?

 

James, last weekend at Carlsbad I got a new best time, in my sig.
This weekend at Famoso I couldnt get better than 13.4 @ 105.50, but I only got four runs, 2 practice and 2 eliminations.

Glenn, at the dyno the MAT temp was 22* C, and the coolant temp was 76-78* C.
At the track the coolant was 84-88* C, and the MAT was 32-34* C.

I have the runs if you want to look at them.

 

Glenn covered everything that I can think of ...
1) IAT Temp
2) Coolant Temp
3) Altitude

All the evidence suggests that you should have seen the opposite. As IAT goes UP the Multiplier goes down in order to use less fuel. As coolant temp goes UP, the PE table value goes down in order to use less fuel. I guess the remaining question is altitude. However, along with this question I would pose the following: Plot a graph of RPM vs Pulse Width for each diacom run. Compare the pulse width to each RPM reading. To the graphs look similar except for amplitude?? The highest pulse width for each run was at what RPM?

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

I uploaded the Diacom runs to my webpage, they're at http://24.1.139.249/dyno/

They're the ones that start with F. I was using the Dyno24.bin PROM.

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

Ok, lets try this out. If it makes sense, I know Tim and Glenn will say "I told you so"

I still have my chip with the WOT mods made to the 100 KPa region only. At the dyno I was seeing 100-101 KPa on Diacom, but at the track I was seeing 98-99 KPa. Since I made the changes to the 100KPa region only, the 95 KPa region is still higher values. So if the computer averages them, the high values at 95 KPa with the lower values at 100 KPa would make the pulse widths higher than what I saw on the dyno, right?