HP Tuners Accuracy

[Nimrod_R]

I know on older cars the stock tach's are generally off in the upper rpm's. Is it still the same on alot of newer ones as well. I have an 06 GTO 6 speed (no motor mods) and figured the tach would read kinda close.

But when I log runs at the track, there is anywhere between a 300 to 500 rpm difference in what I think I am shifting the car at and what the logs show I shifted at.

Even trying to bring the rpms up at the line to launch consistantly, what I thought was 3000 showed on the log to be more.

Just wondering what others have noticed.........

[12secSS]

The dash tach has a damper in the signal it recieves, so it will show lower rpms then actual. It is like a fial safe system to prevent the driver/owner from over revving the engine (supposedly). The ECM uses the crank signal for instantaneous rpm, so the scanner will report that value. I would trust the scanner over the dash tach. It is standard across the board for all GM makes.

[boomer]

The dash tach has a damper in the signal it recieves, so it will show lower rpms then actual. It is like a fial safe system to prevent the driver/owner from over revving the engine (supposedly).

that makes sense, but wouldn't it have to be the other way around? make the driver think they are reving higher than they actually are.

[Nimrod_R]

that makes sense, but wouldn't it have to be the other way around? make the driver think they are reving higher than they actually are.

Thats what i was thinking, would make a better fail safe the other way around.


Thanks, I figured the scanner was accurate.

[12secSS]

I have seen it both ways, mainly the first, so it is not set in stone. The point is that the dash rpm is not accurate at all.

[boomer]

I have seen it both ways, mainly the first, so it is not set in stone. The point is that the dash rpm is not accurate at all.

i'll have to pay closer attention next time i'm logging. id like to see how my tach compares.

[GTPprix]

If there is a 500RPM discrepency on LAUNCH IE brake stalling it there is something wrong there. The GTO cluster is actually one of the more accurate clusters out there. I'd be suprised to see that much at such a steady state.

[Nimrod_R]

If there is a 500RPM discrepency on LAUNCH IE brake stalling it there is something wrong there. The GTO cluster is actually one of the more accurate clusters out there. I'd be suprised to see that much at such a steady state.

I have a 6 speed, no brake stalling for me. Also its not like I have time to sit there with the revs up. Once the second staging light is lit the tree is coming down, they dont mess around at our track. So as soon as I pull in I have to get the revs up and dump it. I dont like getting the revs up first and slipping the clutch to move into the second bulb. Had clutch trouble slipping it before. Anyway, my point is the tach shoots up real quick just like it does on shifts. If it had time to stay at the rpm maybe it would be accurate.