RPM inaccuracy?

[robz]

It's been over a year and I still haven't figured out how to get my data logged rpm's accurate. They seem to read about 300rpms higher than the actual flywheel rpms. One way I know for sure is that my limiter is set to 7150 and I get readings over 7400 with the data logger and there is no evidence of hitting the limiter. Can anyone help me get this accurate? It would really help me dial in my car at the strip!!
Thanks

[Dirk Diggler]

it takes a little bit of time to hit the limiter i think i recall 25 ms . my revlimiter is set to 7k going thru the shifts @ 6800 (M6) i see 7100+ at times

[robz]

it takes a little bit of time to hit the limiter i think i recall 25 ms . my revlimiter is set to 7k going thru the shifts @ 6800 (M6) i see 7100+ at times

Not sure I understand your reasoning. I also have 4.10 gears.

[minytrker]

There is basically a little delay or lag time before the rev limiter kicks in. Its not instant. I see it more on higher hp cars that rev alot faster than stock. I have seen it happen many times while tuning, but not as big of rpm differnce as your having. What kind of car do you have and how is your rev limiter setup?

[robz]

There is basically a little delay or lag time before the rev limiter kicks in. Its not instant. I see it more on higher hp cars that rev alot faster than stock. I have seen it happen many times while tuning, but not as big of rpm differnce as your having. What kind of car do you have and how is your rev limiter setup?

I have an 03 Zo6 with 4.10 gears making about 475rwhp. My limiter was setup by my tuner using efi live. Can I assume that the lower rpms readings are correct?
What about when I don't hit the limiter? Why does my tach read above the limiter setting? Do you feel my car is actually revving to 7400 plus?

[minytrker]

I would think your factory tach cant keep up. In my 02 Z06 it was off a little at higher rpms the same way. Do you have a way to log the actual data vs using the tach? I think the tach is just being slung passed the correct reading from the fast reving of the motor. I know my z06 with just 450rwhp reved fast as hell.

[Dirk Diggler]

All stocks tach tend to lag at around 200-300 rpm this is why most got and aftermarket tach

[robz]

All stocks tach tend to lag at around 200-300 rpm this is why most got and aftermarket tach

I understand this. My tach with my launch and 4.10's lags about 600 rpms on the 1-2 BUT I'm not talking about the tach. I'm assuming the datalogger measures the engine rpms. No? This error should have nothing to do with the tach. I can't believe no one has had this issue. It's critical to know your shift rpm's exactly and that the main reason I bought the data logging system.
If I shift before my rpm's hit the limiter then the reading should be lower than the limiter. Anyone else drag race and log?

[minytrker]

How is your limiter set up?

[johnsZ06]

Very good question.

I've never noticed this on mine but I'll be paying attention to it next time I log.