Read this: Info on 4-tec motors, injectors,rrfpr's, etc.

[planiack]

Great thread. I have not had a chance to go over all the math but at a quick look, it looks good. On point on injectors. I recommend having you injectors taken to a flow bench and have them tested. Even have your new injectors tested. I cannot vouch for the PWC world but in the automotive world you can take a set of 8 new injectors out of the boxes and flow test them and have a 25% difference between injectors. Fortunately for me I had a veery good relationship with my supplier and they knew what I was doing so I could order 16 injectors, flow test them all and get a good set of 8 and they would take back the other 8. I cannot believe that in the PWC world that the tolerances ar tighter than in the auto world. Someday when I get a chance and I have a few injectors kicking around, I will do my own tests and find out for myself, unless of course anyone has allready done this, I would enjoy hearing the results.

[DooSPX]

I am from the car world also, and I never like to run the injectors past 80% on modified motors for the fear that if for some reason it goes lean, the injectors have a little wiggle room. plus, on the dyno you can tell when the injectors are maxed out. sometimes we have even pickup up power from larger injectors after the tune. this is on LS1 based cars/trucks

[gOt BoOsT]

another basic fuel pressure rule of thumb is for every psi of boost, you need twice the fuel pressure. for 30psi boost i run 65psi fuel pressure. the problem is you cant run that high of a base pressure so my secondary fuel pump is boost activated with a hobbs switch. i would NOT advise anyone to run past 85~90% duty cycle because you will melt a piston. Fuel Injector Clinic (FIC) does injector cleaning and bench flow testing for pretty cheap. the only way to really know idc would be through a data log tho.

[JBA]

Hello Gents,

These 4-techs have separate injectors for each cylinder right. I can't understand how a 100% (or near 100%) duty cycle is maintained on each injector during the "four cycles" of a cylinder at WOT. Why would they inject fuel during intake stroke, compression stroke, power stroke, and exhaust stroke continuously at WOT? Would it not be 100% (or near 100%) of a set time of the intake stroke and/or compression stroke? Can someone please help me with this one?

Electronics background... Check
Four-stroke... Nope
Two-stroke background ... Rusty

Cheers!

[JBA]

I think this answers my question: http://en.wikipedia.org/wiki/Fuel_in...uous_injection under "Multi-point fuel injection"

The fuel is injected into the port before the intake valve: I assumed fuel might be applied during the intake cycle for mixing purposes. I also assumed the fuel might have been directly injected into the cylinder.. Apparently this is called "Direct Injection" Haha! This is also explained in the link above..
Hope this helps someone else just like me.

Cheers!

[beerdart]

Bump