Fingers

OK... it's time for this myth to be proven or dispelled. I'm sure by now everyone has heard of the possible 58% maximum duty cycle that the injectors can be driven by the stock ECU. Simple question: True or not?

I'll be blunt, and I hope nobody takes offense, but please only reply if you have had personal experience with this (reverse engineering the ECU, monitoring the duty cycle by an external device, etc etc).

Thanks!

Scott 89t2

I think this myth comes from the rx7.com fuel thing. which says the stock one runs at 58% to 63%

now type those in. 58% gives you 183hp (stock S4!) and 63% gives you 199.xx (stock S5!!)

therefor when stock the max the ecu will hit is those numbers, because that is how much fuel you need.

now how many people are running more then stock HP here while keeping the stock ecu? like everyone??....

I have no idea how to measure the duty cycle but I call BS. it'll probably run to 80+ I'm sure.

gsracer

Henrik on team fc3s reverse engineered the stock ecu to a certain point he has discovered that
the primary injectors will not go over a 66 percent duty cycle before the secondaries come online. As for after the secondaries come online....I would guess mid 80's?

Madrx7racer

83.2% duty cycle according to my Apex-i S-AFC.

Scott 89t2

you mean acvr ?? or how did you get the afc to read?

NZConvertible

I haven't measured the injector duty cycle myself, but I've gone through the same thought process as Scott, and I've said as much a few times here. If the 58% limit was true, then there's no way any of us would be able to exceed stock power.

The testing gsracer mentioned doesn't necessarily mean the primaries have a duty cycle limit, just that the particular load that the secondaries operate at corresponded to that duty cycle.

I've read many articles about tuning cars that mentioned measuring injector duty cycle. Most of the time it was mentioned because they'd hit 100%! It seems illogical that Mazda would have a duty cycle limit when nobody else does.

BTW, monitoring the duty cyle of injectors is easy. Any mid-range DMM can do it. Unfortunately mine doesn't.