A few years ago Howard recommended 325 cc/m WI for 400 whp but gave no % of water to fuel. My calculation for my stock port GT35R at 16 psi based fuel mass came to 322 cc/m WI at 20% of fuel.

I am in the process of bumping my pressure to 18 psi. My estimate is that this will give about 425 whp. Thus is 345 cc/m WI good?

 

When i was going Single last year Howard recommended me 400/500cc water for 450-500whp.

I think for 425whp you should at least up it to 400cc/m to be on the safe side.

 

http://www.howertonengineering.com

 

Their calculation is not valid for my setup.
(1) Their calculation determines the maximum water flow you need if you max out the fuel injectors based on a fixed % of water vs. fuel flow.
(2) Then you would need a system that flows water at that % based on injector duty cycle change as you boost.
(3) I have a AEM system, not Aquamist.

But it might help someone.

 

I just estimated what the new fuel would be and calculated from there.
I just wanted another educated reply.

Someone put this thread to bed.