RPM Inaccuracy?

[robz]

I datalogged some runs and noticed my logged MPH is higher than the rev limiter set on the car? What causes this inaccuracy? Can I correct or calibrate this so it is more accurate.
Thanks

[emarkay]

What is the limiter set to and what RPM did you get - was it one "spike" point or a consistent amount of readings above the limit?
What did the car's tach indicate?

[robz]

It is a consistent thing. I took 8 drag passes and on all shifts the rpm reading on efi live exceeded the limiter setting for the car.
I have a shift light and have it set to 6800. My limiter is set to 7200. I did not hit the limiter on any shifts. So, the rpm reading should be all below 7200. I got rpm reading on the efi live up to 7500, all over 7200 which is not possible. Any ideas? How can I correct?

[emarkay]

Strange - I take it your car is not stock then?
Tell us what mods, and all the important info, and if possible attach a logfile.

Maybe also do a log at idle, then at 1000, 2000, 3000, 4000, (and 5 & 6K if you want) for a few secs each using your tach and the realtime logging of EFI - use just the RPM pid - and see if they jive.

MRK

[robz]

Strange - I take it your car is not stock then?
Tell us what mods, and all the important info, and if possible attach a logfile.

Maybe also do a log at idle, then at 1000, 2000, 3000, 4000, (and 5 & 6K if you want) for a few secs each using your tach and the realtime logging of EFI - use just the RPM pid - and see if they jive.

MRK
I don't know why I put this in the diesel section? :D Maybe a mod can move it.
I have on 03 Zo6 with H/C plus boltons.(manual) At idle the efi rpm is accurate with the tach on the car. It's not jiving on the track up near the limiter at wot.
I'm using the Engine rpm pid. Does this record actual rpm or calculated?

[joecar]

I'll move it to Scanning->General.

Edit: ok, it is now moved.

[emarkay]

The heading at the top of THIS page doesn't show Deisel, but yes, it is in the Deisel category as shown on the main page.

What about midway up the RPM band - Need to know if it's a glitch above a certain RPM or a progressive error, but then again, the RPM should be what the PCM is seeing....

If you can get and post that info and maybe also PM GMPX to see if he's got any more ideas.
MRK

[joecar]

Rob,

Also, check the following:
a. logging in Stream Fast 10 fps mode
b. no more than 24 channels worth of pids
c. status line (bottom of scan tool window) shows your correct vin/os/trans (File->Enter VIN).

:)

[robz]

Rob,

Also, check the following:
a. logging in Stream Fast 10 fps mode
b. no more than 24 channels worth of pids
c. status line (bottom of scan tool window) shows your correct vin/os/trans (File->Enter VIN).

:)
I check all those things. Could the rpm's be surging past the limiter and not trigger the rev limiter??

[robz]

It would be extremely benenficial to me if I was able to have the rpm's of the car match the rpm on the efi live gauges. If anyone has any suggestions, please let me know. Thanks.

[joecar]

Rob,

I don't know the answer to this yet.

Can you email me some logs showing this and your tune file, my email address is in my profile.

Thanks
Joe

[GMPX]

Also asked Rob via Email to send some logs.

Cheers,
Ross

[robz]

sent log to joe and gmpx!

[joecar]

Rob, what does your B3301 "Engine Overspeed Time Allowed" say...?