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Bridgeported 13b drivability

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Hey guys I was wondering if there is anything or anyway I can go about improving the drivability at the lower RPM and load zones of a bridge ported Mazda 13b. as many probably already knows how jerky the power delivery can be at the lower RPM and load zones especially for cruising and driving normally at a lower RPM range.

Depends completely on the fuel delivery/manifolding setup. Sub 4000ish rpms on an IDA is always going to be garbage in my experience. Longer runners and fuel injection can generally be made to drive around town with ease.

The link below should help anyone else in a similar situation


This is a complete hack much akin to Adaptronic's entire approach to software :P. There are so many other approaches that should be made before neutering an engines power output such as injection timing etc. Bleh.

Keep it coming Mr guy, I'm sure anyone else reading this post would love to hear more

I don't want to sidetrack this post too much, but I've got a mostly-stock FD RX7 and the transition from zero-throttle (decel fuel cut) to part-throttle has never felt quite as smooth as most other piston cars I've worked on. First thing I tried was disabling decel fuel cut and getting it to run smooth at medium/high RPM and zero throttle, but the engine always ran pretty rough in those conditions, it sounded like combustion wasn't very stable. I've tried a few different things (lambda target between 12 AFR - 17 AFR, ignition timing between 10-40 degrees, and ignition split probably between 0-20 degrees) but it's still not quite nice. I just assumed it's a rotary thing, but if the resident rotary gurus have suggestions I'd be very interested to try them. I think I may have made minor adjustments to fuel injection timing, but it's been a while and I don't remember anymore. I don't think I've tried adjusting the IAC position or idle air bypass screw, in case the engine has too much or too little air. I can dig up logs and maybe take video to show how it sounds, if that would be helpful.

In case this helps the original topic of drivability, I think it helps to make sure the engine goes slightly rich (never lean) if engine load increases from fans kicking on or slowly dragging the clutch at idle. That's not really rotary-specific, but especially important on any low-displacement / low torque engine.



I'm thinking the OEM double throttle which is activated via a solenoid , vacuum box and actuator was designed to help avoid these studded changes in VE at lower RPM and load zones. Hope this helps you out Mr. Borg

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