I'm wondering if anybody has experienced this before. I recently installed a pro 10 on an integra. If I take the car on a longer drive (1 hour plus) or really beat on the car for an extended time, the tach will start bouncing a few hundred rpm's. When the bouncing starts to happen, around 4k rpm, If let off or give it more gas the issue disappears from anywhere between 20 seconds to 5 min. I've never seen it bounce at idle or while the tach is sweeping upwards. Its always when its in a sustained positioned for x amount of time. The car itself feels absolutely fine, no loss of power etc.

Details on the install:
Its mounted in front of the passenger shock tower. There are three separate harnesses that come out of the unit (Each harness is routed separately away from the others). Battery, Coil and everything else (this routes to the dizzy: tach signal, ignition power, ecu trigger).

To me it seems to something of heat/noise related but thats just a guess.

Thanks

 

Just to rule it out - Have to datalogged the Ecu to make sure this rpm flux doesn't show up there too?

 

A bad wiring connection or ground can cause all sorts of issues. Check all of the wiring first

And do like muck said. It could be something as simple as the tach in the cluster going bad

 

I have an autometer shift light with digital tach, and it does a similar thing. The idle RPM works fine, but when I'm on a pull, the shift light randomly blinks even if i'm not near redline or spinning.

The datalog is good, and the C.E.L. shift light works fine. Been like this for years, I just turned down the brightness, lol.

 

had the same issue in my car , i checked the connections inside the dizzy and found the female connector a little loose so i squeezed them to make em fit tighter and problem whent away

 

This was a good idea, I ran a log and the ecu sees everything as normal.

I did reroute the harness to the dizzy thinking maybe I was getting some noise. Before it ran right next to the main engine harness. Moving it showed no change.

Something very interesting. I drove the car 4 hours to gingerman over the weekend and really got to test some things out. The bouncing only happens at 3900-4000 rpm. If the car is as 4100 it doesn't bounce, if its at 3800 it doesn't bounce. If the tach is sweeping upwards or downwards at a moderate pace it doesn't bounce. For example I can go create the problem and drive 70mph in 5th (which is around 4k). I can make the tach bounce for as long as I want; step the speed up a little and raise the rpm to 4100, tach bounce is completely gone.

There has to be something going around this rpm that is causing noise. On the track I noticed zero issues. I'm wondering if the alternator is doing something funky at this specific rpm?

 

And what specifically is driving the tach?

 

The m&w pro 10 is going straight to an ITR cluster. The stock ICM has been removed.