what size fuel injectors

[mattspyder]

alright guys whats up, quick question and i expect a quick answer. i got a t04b v-trim turbo, fmic, 190lph fuel pump, dual stage mbc. Now what size injectors should i get? im thinking 660's. what you guys think/

 

[Staytuned]

I am using 650's with my 3052 turbo which flows almost exactly the same amount of air as the V-trim. I am planning on running 20 psi of boost for now. But I am using the AFC for fuel control, if I had DSM link I would use no smaller than a 750 for peace of mind.

 

[oldman]

Yes, it all depends on what you will tune with. The 650cc is at about the limit of the afc.

 

[94EclipseGST]

I agree with oldman. If your using the AFC or MAFT, it's going to be hard to tune anything bigger than 660's. But I think 660's will be enough for you.

 

[Game Over]

SAFC will be good for almost 700cc if you do it right. You will be good with 660's though.

 

[mattspyder]

alright so 660's will probably be it! anyone know of a good place to get em for cheap. any web sites..??

 

[oldman]

alright so 660's will probably be it! anyone know of a good place to get em for cheap. any web sites..??

Besides the regular vendors you can easily find on this site, you should also consider picking up a set of decent used ones, if you find a good deal, and send them out to be clean and flow tested. Every injectors flows at different rates even when there're brand new so it's good to know 1) they all flow farely evenly. 2) Exactly what they're flowing in case if decide to go with dsmlink/eprom setup. I almost sent out my brand new Denso 720s out for a flow test but had to pull back due to "way over my inital budget" issues.

BTW Check out ebay as well, I was lucky to find my Denso 720s on ebay for $300, I don't think the guy knew how much they were worth.

 

[Clipse7]

Where could one have their injectors tested? Doesn't sound like a bad idea at all, but could a guy get it done locally?

 

[oldman]

Where could one have their injectors tested? Doesn't sound like a bad idea at all, but could a guy get it done locally?

I sent my RC550 to RC Engineering, FIC does it as well, just to name a few.

 

[whitegst97]

I also need some help with injector choosing. Im running the t04b v-trim as well and right now i only have a 255 fuel pump with MAFT, im running 16 psi and im running rich, the timing keeps increasing as i lean out the Translator, the 02 volts show 1.01v, pretty rich. I know 02 volts is not the best thing to tune by, but timing is good and signs of richness are there. Wouldn't 550's be enough? If i have to lean out the maft, i know my stock injectors are probably high in duty cycle but on stock injector and with the 255 i have to lean out a lot, i think getting 660's or higher would be way too over kill. Now it could be that i have a boost leak or something but the car runs perfectly fine. What do you guys think

 

[oldman]

Definitely AFPR and and possibly boost leaks.

 

[whitegst97]

What would the AFPR do in this case? Thanks

 

[RamenPride]

What would the AFPR do in this case? Thanks

if you have the high pressure 255 then you're overrunning the stock regulator. the AFPR will allow you to turn down the fuel pressure.

 

[whitegst97]

So i have a higher than normal fuel pressure and that is not letting me tune properly, but at WOT, what i was saying is that if with these fuel mods im running 16 psi and running rich, then i really wouldn't need 660's or higher to run 20 psi. Considering i would get an AFPR and bring the pressure to stock, or raise it then 550's would be ok? This turbo i think is rated at like 450 HP? Thanks for your help guys, i'm a bit confused with all these things.

 

[loweperf]

So i have a higher than normal fuel pressure and that is not letting me tune properly, but at WOT, what i was saying is that if with these fuel mods im running 16 psi and running rich, then i really wouldn't need 660's or higher to run 20 psi. Considering i would get an AFPR and bring the pressure to stock, or raise it then 550's would be ok? This turbo i think is rated at like 450 HP? Thanks for your help guys, i'm a bit confused with all these things.

If your running the turbo to maximum 450Hp the you can calculate the required injector size by the B.S.F.C.(brake specific fuel consumption)if you don't know what this is don't worry just use .60 for a turbo engine.Divide this number by the number of injectors times the duty cycle(use.80 for 80% duty cycle)then convert to cc.

450(hp) x .60bsfc)=270
4(no. of injectors) x .8(duty cycle)=3.2
=84lb/hr injectors
to convert to cc multiply by 10.5 =882 cc injectors
this is the correct way injector size should be calculated and alot of people get away with doing it differently but if you talk to a engine builder or dyno man they will tell you about the B.S.F.C. numbers they see.This is the only way to get enough fuel for the airflow your putting into the engine.