If I have 550cc primaries, what size secondaries would I need to support...250 HP? 300HP? 350HP? 400HP? (SAE net)

Let's assume 15% parasitic drivetrain loss, for those who think in terms of power to the wheels.

 

I have 750's... that doesn't help... but i haven't posted in a while

 

720?

 

http://www.rx7.com/calculators.html

 

I use 1600cc on a 400-450hp engine

 

If you work on 7.5cc/min per hp, you'll be safe.

 

so that means the stock fuel system can support up to 293 HP?

 

Technically no. The 550's could flow enough fuel for over 300 hp, but that maxes out the duty cycle and they'll overheat. You'd also need an aftermarket ems and fuel pump. There's more to a fuel system than just injectors.
-John

 

No, they are not at 100% duty cycle. Those numbers are based on ~85% duty cycle, and assume fuel pressure is sufficient. The stock fuel pump won't support that much power and needs to be upgraded.

 

NZ, your numbers and RP's fuel calculator don't agree. From them I only get 269 fwhp running all 4 550's at 85% duty cycle. Who should we believe? I'm confused.
-John

 

Most people run 720 secondarys on a T2 unless they have like an upgraded turbo. I don't trust those calculators. My friend put down 217whp on his T2 with original motor and stock turbo & injectors. I wouldn't try to get more than that.

 

Obviously you shouldn't swear by the calculator as there are many other variables that will affect how much power you can put down, but a 24 hp difference is substantial. How did NZ come up with his numbers? How did RP figure out their calculator? I'm starting to lean more towards NZ, but I'm still curious.
-John

 

IMO that RP fuel calculator is conservative. I'm just working on numbers I've read in various places over the years. I notice that practically nobody bothers to measure injector duty cycle when they do dyno runs, so hard data for the stock injectos and ECU is hard to find.

Personally I would bother upgrading the injectors if you have a stock turbo at sensible boost levels (<12psi).