After 50+ runs, I have noticed where exactly to shift in 3rd to yield a best trap speed.

But I'm pretty damn sure our tach meters are off by a significant amount.

For reference, lets use ~7000 RPM's (stock redline in revup) as a baseline.

Remember, this pertains to revups only!

For both 1st and 2nd gear, I usually do not pay attention at the exact RPM I shift at; everything goes by so quickly I hardly remember. But from most of the times I do remember, its just at redline (6900-7100 RPM's).

For 3rd gear, I have tried shifting at many different revs to see how much it impacts my trap speed.

What I have found is, using 7000 RPM's as a reference point for baseline:

-If I shift at 6800 RPM's, I trap about 1 to 2 LESS than shifting at 7000 RPM.

-If I shift at 7400 RPM, I usually trap 1 to 2 MORE than shifting at 7000 RPM.

I'm not really going to state my trap speeds because at a hot summer day in LACR, its really not that important.

When I shift at 7400 RPM's, if I shift a tad too late, I notice the ECU cuts power just as I cross the finish line. (So the ECU cutting power doesnt really affect my times at all, since it cuts it after I finish). It doesnt bounce off the limiter at all, it just seems to cut power. Therefore, I usually try shifting at 7300 RPM's to avoid this, but this makes me have to shift into 4th, which slightly lowers my trap speed.

LACR is a track with high evelation, which means that shifting into 4th can be avoided in certain conditions (revup, hotter days than usual, etc).

Now my question is, how off is the rev tach-meter in our cars?

From what I have heard, at redline, 1st gear seems dead on; 2nd gear is off by +100; 3rd is off by +200; & 4th, which doesnt matter in my case, is off by 300+.

If this is true, then that means that my redline/rev-limiter in 3rd gear is actually at 7400 according to the tach-meter. (When in reality, the 7300 read by the tach meter is actually 7100).

So, can anyone confirm this? It seems to be correct from my track "experiments" & tests.

Just to avoid any confusion, I am talking about revups here only. I can't infer that the same applies for non revups since they have a lower redline.

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It is confirmed. I have seen dynos with revups and non revups (my car) where the tach usually shows 200-400rpm higher than it actually is.

 

Confirmed. I've observed this as well. The easiest way to tell is just run out a gear on the interstate, at least up to 3rd gear of course