I currently have 440cc injectors. I went the euro shop by me a little while back . they said i could go to 660cc injectors if i want to max out my turbo and not limited by injectors. I been reading around and seen that some ppl are running 660cc with like some improved version ko4 (Frankenturbo MetalMan) i think. BUt i have gt28 which is little larger right, wouldnt i use bigger injector than a ko4 or does it just depends on the tune?

Thanks in advance

 

440's should be fine for a gt28. unless your running meth or race gas, id stick with those. generally, people, like me, run seimens 630cc injectors which seem to work fairly well with our cars. the only reason you need bigger injectors is to match the added amounts of air your allowing into your enigne. for so much air, you need so much fuel. i dont see a gt28 necessitated 630's, but it could allow you run different programs. personally, i am running a gt2871r with 630cc injectors and i believe i am no where near maxing the injectors.

 

i got this audi with the turbo upgrade( i seen the stock one 1st hand) but not sure extacly which one it is but it has 4 bolt flange exhuast side, I had it out and look on it for anything number or letters there wasnt much i googled found nothing , so i dont know what i got. I have a boost gauge installed too. And boost builds around 2800rpm and i hit full boost around 3350rpm (21psi it spikes idk why somtimes up to 25psi, i seen it do once). Are these characteristics of a normal gt28??

 

Generally speaking, you should never be limited by your injectors. It's almost always best to leave some headroom to keep your injector duty cycle from reaching too high of a value. I think I've heard you should try to keep it under something like 70%.

I run 630cc on a turbo that probably wouldn't ever need more than 380cc. It runs just fine. Just make sure you have a tune that is supposed to be able to support the chosen injectors, and if you can, hopefully the tune will also be somewhat compatible with your turbo.

 

How your A/f ratio ? if you have larger injectors than you need ?

 

A/F is mostly fine. Since the tune is designed to use 630cc injectors, the ECU pulses the injectors only as much as needed. It determines how often to pulse them (duty cycle) based on things like mass air flow readings, intake air temperature, engine load, RPM, etc. Having larger injectors than necessary simply means that their duty cycle won't ever be very high.

My car used to have the opposite problem... injector duty cycle was at the maximum and the engine still wasn't getting enough fuel.

 

more or less, injectors have nothing to do with a/f ratios. its how the ecu uses the available cc's of fuel to determine a/f. if your tuning isnt correct, you could run way lean on 1000cc injectors on a gt28. on the other end, its possible to flood the cylinders with fuel on 1000cc injectors and a gt28. its really in the tune and how it uses the capabilities of the injectors.

we could get into raising fuel pressure, but ill only do that if asked. you could essentially turn you 440cc injectors into much larger ones, but at the risk of overloading the pump