Blipping on acceleration
 

Hey Guys,

I have a 1988 FC rx-7 with haltech Sprint. Bnr stage 4 turbo, 550/1000cc injectors, etc etc. Car was tuned by steve kan at 340rwhp a couple of years back

Sometimes it runs great and pulls smoothly. However sometimes under acceleration it cuts out or just blips a little bit under boost. This morning i took it out and first few pulls was super smooth tons of power. Then towards the end of my cruise i did a few pulls and its breaking up. Any ideas on where to start hunting down this problem? Thanks

- Erick

i am no expert, but check the compression. sometimes when things get hot and expand, problems in that regard start to show up. so it would run well when cold. also in a situation like that it might be hard to start hot but start well cold.

This is pretty common on cars that get primarily tuned on a Dynojet instead of an extensive street tuning or tuning on a brake loading dyno (as opposed to Dynojet inertial loading).

It is usually too big of gaps between one cell and a neighboring cell so you are running into a rich or lean area.

If it is from being too lean it is often masked by throttle pump setting fuel addition when you stab the gas, but power momentarily drops out when you gently accelerate through that load range.

If its too rich it is usually exacerbated by stabbing the gas and the additional fuel of the throttle pump setting causes the engine to feel loaded up and sluggish.
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This could also be ignition dropping out for some reason, a fuel delivery problem, a fuel quality problem or detonation feels the same. If this just started out of the blue I would suspect one of these.

But, if your car has always done this intermittently since the tune I would suspect the mapping as I first suggested.

The engine has great compression so i dont think thats it.

Thanks Blue TII some of that was a little over my head but i think i got the jist. Ill check on the fuel issue. The A/F ratio stays about right the whole time. I have a pretty high powered e-fan running is it possible the injectors arent getting the voltage they need?

It is really hard to tune out a transient drive-ability problem by watching an consumer grade aftermarket AFR display or even data logging AFRs with consumer ECUs.

We are basically looking at an average of AFRs from many exhaust cycles over a given period of time that does not necessarily correspond directly to where the engine is currently operating.

I have a pretty high powered e-fan running is it possible the injectors arent getting the voltage they need?

The ECU adjusts injector duty cycle based on electrical system voltage so there is usually no problem with the injectors and voltage drop.