I was reading this taiwan issue OPTION magazine. and it did a very short introduction on this rx7 with 4 , 750cc injector. on the magazine it says that it used a 4 cylinder fuel system to tune the car.

my question will be,
1. how did the rx7 rotor housing stand that kind of power?
2. what else is needed to tune a rotary car with 4 x 750 injector?

 

I have a friend with an 88 TT motor that pushes 650HP to the wheels on a Ist Gen chassis...running very low 9's....about 25lbs of boost They are adding a 150 shot to try and get it down in the 8's

 

I guess I'm missing somethng... you can put HUGE injectors in but without the AIR to mix with the gas, it won't do anything.

So was it SC'ed? Turboed? If so, what was the duty cycle of the injectors?

As many probably know, you can get an almost exact horsepower calculation by simply using the amount of fuel being used, which can be figured out by knowing the size of the injectors and what % of the capacity of the injectors is being used.

 

but big injector is the fomula to no-blow turbo charged 4AT.

i am not good in tech. can someone explain more thanks.

 

Injectors only provide for power gain when combined with a higher Partial Pressure of Oxygen (Turbo, Supercharger, or Nitrous).

As long as the injectors are not too big for idle and low load, you can get the biggest injectors you want, as long as tune for them. Jeremy is right, fuel is half, the air is the other half. Stock fuel system is good for at least 38 lb/min of air... that is WAY more than any NA engine is going to need. But FI @ 9 lb of boost @ 9000 RPM is going to need bigger injectors.

FYI Fuel Pump also needs to be able to keep up with the injectors too.

 

Thanks Kane & jeremy, this really helps.

ok. now where were we.... ok how do we put in the extra 2 injector? presume we have the air

 

The 6 port has 3 injectors per rotor, the 4 port has 2 I believe.

If you had a standalone Engine Management, or maybe even a piggyback, you could run the normal primary injector so low speed driving works; and swap the Secondary to a large size (they are 600cc now for 6 port). SO if you took out the 2 600 cc injectors and added 2 750 cc injectors, you would have 300cc more fuel delivery. Otherwise you would have to look at Add an Injector Kits, which I don't know if any are made for the RX8 right now. With a 4 port, maybe you could swap fuel rails with a 6 port... be creative.

 

https://www.rx8club.com/australia-new-zealand-forum-37/rx8-fuel-injectors-pump-problem-when-supercharging-40472/

 

mysql101, thanks for more info. so if our 650cc injector is working 85% all the time, 750cc injector will run on 98% for the engine. most likely to get jam one day.

 

^^ bigger injectors will have lower duty cycles for the same amount of fuel delivered.......so about 74% duty cycle