RPMs spike during up shifts
 

I've been chasing this issue for a little while. The car is running good and idles well but when I am up shifting, once I put my foot on the clutch the RPMs will jump a few 100 RPM. Doesn't really make shifting smooth. I've been trying to sort it myself but can't seem to resolve it. Anyone have any suggestions? Short log and tune below.

Details of the car. 1997 Miata. MS3 Pro pnp. BRP MP62 supercharger, 75mm throttle body, over the radiator fed intercooler. 640cc Flow Force injectors, DW200 fuel pump. Also the IACV is from an NB mounted to the dummy throttle body.

Tune
Log

Anyone? :sadwavey:

Throttled volume. Basically when you close the throttle, there is still a large volume of air in the piping/intake manifold that the MAP sensor reads so the ECU will inject fuel for it, so when you press the clutch in, there's no load and the RPMs rise. The only way to solve it is to enable fuel cut whenever you press the clutch in above 1600rpm or do the dual throttle body mod.

So I did have a dual TB setup and didn't like it. The charger was whining constantly even at low throttle inputs off boost and it was just annoying to drive so I went back to a single. When I did go back I mounted the IACV to the dummy TB. Previously it was on the SC TB mount. Maybe the IACV location could be causing this issue? I don't remember it doing this before and that was the only thing different that I did (since moving it to the dummy gave me more room for the intake pipe which sits right above where the IACV mounts). Appreciate the feedback. I'll play around with the fuel cut and if that doesn't improve things I may try moving the IACV back to the SC TB and see what happens.

If you understand how the IAC valve works, then you will realize that it simply does nothing when mounted on the dummy TB unless the dummy TB has an inlet port for the IAC (unlikely as it has to work with the stock MAF for those with the stock ECU). This is not the source of your problem however it may fix idle issues.

The dummy does have an inlet port and I have a hose running to my intake from it (similar to the stock OE setup). Thanks again. I will focus my efforts on the fuel cut.