off I go to the PFC section

Crispy

 

I was running high inj duty cycles @ 13 - 14psi (95%) with the stock fuel pump just like you, the tuning on the PFC was a bit rich 10:1 a/f.

I replaced the stock fuel pump with the 500hp denso pump sold @ the RX7store, changed nothing in the PFC.

I was then running ALOT rich 9's:1 a/f. While on a dyno with wideband I was able to pull about 10% fuel out of the PIM Voltage Maps and reduce my inj duty cycle from 95% to 85%. ie 10% less fuel == approx 10% less duty cycle, hence I solved my high duty cycle problem by replacing only the fuel pump and doing a bit of tuning with the PFC on wideband.

I assume the better flow and higher fuel pressure provided by the upgrade denso fuel pump provided the extra fuel allowing me to pull out a bit of fuel and reduce inj duty cycles.

I plan to bore out my 850cc to 1300cc in the near future, probably add RRFPR as well, then re-tune, but at this point I feel pretty safe.

Back to the original question, "running 96%, do I need to upgrade fuel pump". The answer depends on your ability to tune the car afterwards. Just adding the fuel pump won't reduce the inj duty cycle which has clearly been explained above, but adding the fuel pump and trimming the excess fuel will help, in my case about 10% inj duty cycle, enough to get below my 90% threshold of comfort.

K

 

It's all in the math my friend, increase the pressure across the injectors and you increase the amount of fuel being injected. For people running on stock turbos, 12psi is about the limit for the stock fuel system safely.. now if I plan to keep the stock turbos and only want that extra push for 14psi runs once in a while a rrfpr can get you there. To each his own.

Matt

 

ERRRR
I need to find a place with a
Dyno and Wideband 02, that
knows how to tune a PFC. errr..

OK so I am running real rich.
With 90+ % duty cycle..
Anyone have a clue of how much
Horsepower I may be losing??

 

Probably 10 - 30 hp depending on how rich. I only say that because that is how much hp I tuned in as a brought my a/f up from 9:1 to 11:1.

Could have gotten a bit more, but I would rather be safe than have the additional few hp.

K

 

I wasn't flaming you Matt. I was agreeing with you! I have quite a few friends who have used this method to get as much fuel out of their injectors as possible. TD-06/25G single turbo conversion can use this method.

 

Cool, I misunderstood your post then.. glad to see we agree. If any of you choose this method though make sure you have an excellent fuel pump.. when you start raising the pressure a 2:1 and 3:1 on boost your fuel pressure gets sky high, if your pump is not up to the task your pressures will drop like a rock and there goes your motor.

Matt