Or get a PMS or PFC

I watch mine while I drive.. or should I say when I drove

 

Just slap some 1300's in there and let it rip

 

I would also upgrade the fuel pump at this time

 

thx i know how much injectors run but how much am i looking at for a fuekl pump. and what should i be looking for

 

the walbro pump works REALLY good

 

Yep get the walbro pump, cheap and excellent...

 

Two things:



Is there such a thing as to run too low a duty cycle? Perhaps you have some gigantic injectors on a stock motor. Would there be any drawbacks besides a little rougher idle?



Is there anything else that should be taken into account when upgrading the fuel system? Injectors, Fuel pump, etc. How about fuel rail, wiring, etc.?



Thanks.



Kyle

 

In most applications it would be best to keep the stock primaries. This way you can have a good idle. When you really need more fuel than the 550's can supply will be in the higher rev ranges so you get the 1300 or 1600 secondaries and can reduce the duty cycle for them. This gives you small enough primary injectors that you can pass emissions at idle and large enough secondaries to get all the power you want at higher rpm.

 

Duty cycle = (on time/(on time + off time) x 100

Therefore 100% duty cycle means the injector is turned on all the time. Obviously the injectors cannot supply any more fuel past this point unless the fuel pressure is bumped up which is a lousy way of trying to fix the problem. As already stated big injectors are useless if the pump cannot keep up.

No offense to Dragon cause he has taught me a bit about turbo stuff and his FD makes mine look like a piece of ****, but I disagree with his statement abount injector flow decreasing at high duty cycles. I have heard this argument before, but from my experience it just doesn't happen.



Yes there are problems with having very large injectors and running very low duty cycles at idle. The resolution is dereased dramatically. i.e. a 1% change in duty cycle gives a large change in the amount of fuel being delivered, so it is harder to get a good tune at idle/cruise. Thankfully us EFI rotary owners have staged injection so we can have smallish primarys and big secondaries and get the best of both worlds.

 

I did 1200's with a high flow fuel pump. even at 13 PSI I'm only at 49 pct. Pretty sweet. (315.8 rwhp @ 12 psi).