injector size calculator

[chris davey]

Found this on another site.

http://mkiv.supras.org.nz/injectors.htm

Will work for any 6 cylinder car.

Pretty sweet if you ask me

[Draven]

so... anyone hav some top feed 800cc injectors lying around?

[Robbman]

Something sems a bit off... he's saying you'd need a minimum of ~800cc injectors to do 630rwhp at 33psi base, 12.0 AFR, 25 psi boost, 1:1 rising rate, 80% duty...

We've got 680cc injectors doing 630rwhp on a 7M...

[chris davey]

Did you tick dynojet? That is the only thing I could think of.

Use http://to4r.com/calcs/pwtq.php to calculate diff between dynos.

[chris davey]

Just tested it and you are right.

I have gone off the rule that on a 6 cylinder the cc of the injector is flywheel hp so 550’s can make 550hp. This is about the limit. 550fwhp = 412.5rwhp (auto appox.) and that = 309rwkw.

When I put my figures into the calc it says I need 558cc injectors at 90% duty cycle to make 300rwkw (dyno dynamics) so it seems to be spot on for me.

If you think something needs improving, email him though as he was after people to test it and get some feedback.

[kingmick]

so... anyone hav some top feed 800cc injectors lying around?

no but got 6, 1800cc ones

[Draven]

as cool as always running below 40% duty cycle would be, I might have to pass

[chris davey]

perfect for a methanol setup Actually might need a bit bigger

[kingmick]

i use them with avgas or pulp!

[30psi 4agte]

so... anyone hav some top feed 800cc injectors lying around?

Its not what you want to hear but i have some but you cant have them.

just bought some for my 4a they are simens 870cc and cost me $190 each

[Billzilla]

The easy way is to use the Motec way - Just use 5cc per hp per injector.
So (for example) if you have 250cc injectors in a 1UZ then that's 50hp per cylinder and a total of 400hp possible from them.
That's at a standard fuel pressure of about 38psi and a maximum of 80% duty cycle.

[Shifty]

5cc per hp

550cc x 6 injectors = 3300cc
3300cc / 5cc = 660hp

[o_man_ra23]

Hmm, by making some adjustments to calculations between 4 and 6 cyl, for me to get 320fwhp out of a 3sgte, i would be looking around the 400cc injector size mark at 80% duty, 1.0 rising rate, and 38psi base fuel pressure. I am of course assuming that the JZ and the 3S make their power in the same rev range (as the rpm affects duty cycle)

Anybody got any practical experience with sizing injectors for a 3SGTE?? Im looking at using a 320hp garret ball bearing turbo and dont want undersized injectors. Also, anybody know what the stock Gen2 3SGTE injectors are (as fare as cc size is concerned)??

Cheers, Owen

[Robbman]

They should be the black 440cc injectors...

[o_man_ra23]

sounds good to me, means i dont need to worry about injector sizes for my application then.

Cheers, Owen

[30psi 4agte]

just for ref

i made 352 rwhp with 550cc injectors and a static ( non rising rate) pressure reg with the fue;l pressure at 55 psi and they were maxed out !!!!!!


I cranked the pressure up to 70 odd psi and managed 380 rwhp out of em but they were still maxed out at this power / pressure level!

[Robbman]

just for ref

i made 352 rwhp with 550cc injectors and a static ( non rising rate) pressure reg with the fue;l pressure at 55 psi and they were maxed out !!!!!!


I cranked the pressure up to 70 odd psi and managed 380 rwhp out of em but they were still maxed out at this power / pressure level!

70+psi... static regulator...

What are you using for engine management?