Sup guys,

I've been dreaming of going 20B for a while and now the time for me to order parts has finally come. However, some questions I cannot answer myself still remain.

So back on topic, I'm currently shopping for injectors and stopped my choice on Injector Dynamics.

Initially, I planned on running 3x1000 (primary) and 3x2000 (secondary). Although, I just found out about the 6 ports LIM offered by Xcessive. So now, I'm wondering what would be my best option. Currently thinking of going 9x1000.

This is going on a BP engine with an HKS T51R kai. Fuel will most likely be fed by CJ dual bosch 044 surge tank setup (unless someone points me toward a better solution).

Thanks in advance for your help and opinion guys!

 

Can your ECU run that many injectors?

Are you planning on running them in 3 stages? If not is there some geometric reason why you think 6x 1000cc secondaries are better than 3x 2000?

What is your power goal and what fuel? 9000cc/min is a huge amount of fuel, are you sure you need this much?

If it were me, I would go with smaller primaries and the 3x2000cc secondaries.

 

Seems like a **** ton of fuel.

 

Atm my ECU choice is set on Motec M84 which has 8 outputs. Staging is the only way this could work.

Power goal... hmm no number in mind tbh, but I'd be happy between 600 - 700whp on pump gas. I plan on having the car tuned around 15 PSI.

anyhow, I'm here asking cuz this is beyond my actual knowledge and I want to do it right the first time around. In fact, I have absolutely no idea how much fuel I need or how to calculate that amount.

 

I did a writeup on this a while back, but I can't find it, maybe it was on a different forum. In any case, for 700whp:
Assuming 15% drivertrain loss, that is 805bhp.
Assuming a BSFC of .7 lb/hp-hr (decent starting point for turbo rotary at full power), you then need 805x.7=564lb/hr of fuel at full power.
Injectors should be sized for 80% duty cycle, so 564/.8=704 lb/hr.

704 lb/hr total is approximately 7400 cc/min (total)

so if you run 3x2000 cc/min secondaries, then anything bigger than 500cc primaries would be fine. You can run the stock 550cc primaries, or if you want to use a different rail, any 580 or 750 injector will be fine.

The only advantage to running 9 injectors is if your ECU could run them in 3 stages, as in Primary, Secondary, and Crazy Power. That way you could activate each stage at a separate RPM/Boost level and have less transition issues when the large injectors come online. In reality, 2 stages is enough, and hardly anyone uses more than that unless they are injecting a different fuel on the 3rd stage (such as methanol)


On a side note, depending how much else you want to modify on the car, and not knowing your experience, I would plan on 600whp or less as a starting point. You will break less stuff, and that is already more power than an RX7 can really handle unless you get crazy with structural mods and traction improvements. Don't forget all that extra torque you will have as well. A 600WHP 20B rx7 is pretty much guaranteed to make at least one of your friends wet their pants.