Tuning issue or Mechanical issue?
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10 Second Club
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From: Manteca, CA
Tuning issue or Mechanical issue? Our car (Cammed/stalled A4) was on a Mustang Dyno today and would stop pulling in third at around ~5k rpm. Needless to say we did not get any completed dyno runs.
Hypothetically the car was tested on a lonely stretch of road in 3rd gear late at night and would easily reach the limiter in 3rd gear (around ~143-145 mph based on the speedo only)... The car could reach the limiter every time in the open on the road, but we tried like 4 times on the dyno and it would not get above ~5k rpm. What is up? Any ideas?
Someone thought it could be valve float, but the car has less than 4,000 miles on PRC duals. Also the car would easily reach redline in 1st and 2nd, we even experimented with a 2nd gear run on the dyno and it easily held and maintained power all the way to the top ~6200 rpm.
I have had some issues with the current tune, and to me this seems to be a tuning issue... Although I am uncertain and was told by many to post on here to see if I could help diagnose the problem on the dyno.
The car runs strong on the street, and hypothetically will reach the limiter in 3rd on a fictional road.
Could it have been an airflow problem with the enclosed space of the garage/dyno?
I need help....
Hypothetically the car was tested on a lonely stretch of road in 3rd gear late at night and would easily reach the limiter in 3rd gear (around ~143-145 mph based on the speedo only)... The car could reach the limiter every time in the open on the road, but we tried like 4 times on the dyno and it would not get above ~5k rpm. What is up? Any ideas?
Someone thought it could be valve float, but the car has less than 4,000 miles on PRC duals. Also the car would easily reach redline in 1st and 2nd, we even experimented with a 2nd gear run on the dyno and it easily held and maintained power all the way to the top ~6200 rpm.
I have had some issues with the current tune, and to me this seems to be a tuning issue... Although I am uncertain and was told by many to post on here to see if I could help diagnose the problem on the dyno.
The car runs strong on the street, and hypothetically will reach the limiter in 3rd on a fictional road.
Could it have been an airflow problem with the enclosed space of the garage/dyno?
I need help....
Double check the dyno settings. If the overspeed limit is reached, the brake kicks in on the dyno. MD 250's are usually set for 150mph, but the setting is operator adjustable. I'm not sure what other mustang models are usually set at.
What is your speed limiter actually set at? You need to check that first. Generally the mph on dyno's (not sure about Mustang dyno's) is artificially high because the load is much different compared to real world driving conditions. You should also try it on a Dynojet to see if you can duplicate the problem.
Staging Lane
Joined: Mar 2006
Posts: 50
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I'm fairly sure it's the overspeed protection on the dyno, or some other problem with the dyno. Overspeed usually stops the run, and forces the dyno to a complete stop, though (maybe that was just on the older software that we used). Our limit was at something just above 100, maybe 120. Of course I dug through the config (or database file, or whatever it was) and raised it, though.
