What injectors to use

[URSIMPO]

What injectors should I use for a GT3071R 0.63? My car (s6) has a 3" turbo back exhaust, rs2 manifold, fmic, oil catch can, uprated fuel pump, cold air intake, 3 bar map.

Should I use the Siemens 55ilb jobs that 034 sell, as I think that 440cc's would be too small. Am I right?

[urquattro-island]

well

depends on the hp you are going for, i would say.

[URSIMPO]

what ever the limit of the turbo is. my internals -the cars internals- have been uprated so I can give it an extreme map if need be!

[Jamo]

Depends on who is mapping the car?

[A80Avant]

i use the 44lbs and they are more than enough.Those are good for 500+hp with the 3.8bar FPR.If you use 4bar or adjustable then you can get more.
my guy who remapped the car(i have the same turbo as you) actually questioned why i wanted to change the RS2 injectors in the first place.But i did so that i can have them for future upgrades as well.

55lbs are too big IMO

[URSIMPO]

i dont know. whoever pete berry -white cottage quattro- uses. should i find out first and go from there?

[Jamo]

Can't have to big injectors below 750cc to be honest a good mapper can cater for the size.

you want the injectors to be lower than 85 % injector cycle which is why I wouldn't use Rs2 although you could.

[EspenW]

i use the 44lbs and they are more than enough.Those are good for 500+hp with the 3.8bar FPR.If you use 4bar or adjustable then you can get more.
my guy who remapped the car(i have the same turbo as you) actually questioned why i wanted to change the RS2 injectors in the first place.But i did so that i can have them for future upgrades as well.

55lbs are too big IMO

If your tuner likes the idea of lean-burn type AFR at boost, he has a point...
The RS2 injectors are approx 370cc (at the standard 3bar)
With the Turbonetics E50, and fuelpressure at 5 bar, I measure AFRs at 15+ under boost at high rpms. I need to crank fuelpressure to 6 bar in order to get AFR into the 12s. I don't dare thinking of the AFR I would see at stock 3.8bar fuelpressure.
I have 630cc injectors on the way, but I'm about to start running E85.
Bigger injectors means you can lower fuel pressure, and that means that you gain headroom with a given fuel pump.

[A80Avant]

what do you mean standard 3bar?rs2 is 3.8bar,isnt it?

Besides i have afr somewhere 12 if i remember correctly and my injectors are not working overtime either.My remap is pretty rich due to backpressure on this configuration and using the 044bosch fuel pump there is still much more room.

What i said is that for the 3071R turbo,44lbs are more than enough.Im even thinking of using them for the 3076 if i ever go that way.People in the past have used the orange injectors which from what i have been told are about the same,and a bit smaller than the 44lbs and reached succesfully the 500hp crank barrier.

by the way,when i flow tested my 44lbs they turned out to be 471cc rather than 440cc!

[GazzaG60]

55 are not too big.

you need to work out the hp potential of the injector at the given fuel pressure and then take off 20%. 80% duty is about as high as you want to go to get an optimum spray.

ecu is a major factor on how it can control big injectors. its to do with the number of times it samples. in megasquirt for example hi-res code was released to combat the issue of poor cruise on big injectors.

the vems handles them great. as does SDS. LinkECU is a varied. the G3's are ok but take a lot of mapping the older variants struggle.

a mapper can only use the control set supplied so its as much down to ECU. the main reason that people go away from the standard ECU's in cars is big squirter control.

id take 65lbs seimmens, as i did. from what i could gather they have the best spray pattern also.

i doubt 44lbs will do 500hp papvas. they will be well static by then. rather they be in control than just watching for the fuel tailing off.

[Jamo]

what do you mean standard 3bar?rs2 is 3.8bar,isnt it?

Besides i have afr somewhere 12 if i remember correctly and my injectors are not working overtime either.My remap is pretty rich due to backpressure on this configuration and using the 044bosch fuel pump there is still much more room.

What i said is that for the 3071R turbo,44lbs are more than enough.Im even thinking of using them for the 3076 if i ever go that way.People in the past have used the orange injectors which from what i have been told are about the same,and a bit smaller than the 44lbs and reached succesfully the 500hp crank barrier.

by the way,when i flow tested my 44lbs they turned out to be 471cc rather than 440cc!

I have porsche orange injectors on my car and they are 510cc much bigger than RS2 ones!

For ref http://www.s2forum.com/forum/showpos...1&postcount=21

Yes you can use the 44lbs one for the 3071 lb IIRC thats what Ross had

Better to buy big now rather than have to do it again IMO get some around 600cc and you don't have to worry about upgrading.

I could use the 510cc Orange tops for my new engine but decided to upgrade to 750cc RC injectors.

[A80Avant]

guys,im only repeating what erdal told me.I havent gone into it all that much as you have.

Impotant question is : what injectors to use for the GT3071! that is what the man asked,not what injectors to use in general!

As to if the 44lbs will be enough or not,i will let everybody know if that ever happens.To tell you the truth,Aron made 470hp crank on his car with the GT3076(i dont remember what injectors he used,im using this example for different reasons),so if im already making 400hp with this setup and my injectors are not working overtime,then im pretty sure they can cope with 50-70hp more.

Also initially Ross was using the RS2 injectors,wasnt he? didnt he make 428hp with Gt3071R,7Acam and 3inch turbo back? Thats when Mihnea said that the injectors ran out and could have produced more,but EGTs where ok according to him.So im thinking if 370cc injectors can get you to 428crank hp,wont the 440cc be more than enough for that amount of power?maybe even for the 3076?

If we are talking for injectors in general,then yes,everybody is right,the next question should be: how much power are you going for?
For me it is wrong to use injectors that could be used for a 800hp application and only use them with a 400hp turbo.That way you are going to be getting a bit rougher start ups and idle (even with motronic) while you could have a perfectly nice working car with smaller injectors.WHEN and IF you decide to go for 800hp,sell the setup and go for monster lbs...

[GazzaG60]

with a chip tune the 440cc may be optimal as id expect it gets tough to tune motronic above that size.

[terrybullwon]

with a chip tune the 440cc may be optimal as id expect it gets tough to tune motronic above that size.

Doug runs 1000cc injectors on the motronic iirc and Audi man used 620cc with no problems

[Jamo]

with a chip tune the 440cc may be optimal as id expect it gets tough to tune motronic above that size.

Not at all you can even run 8 injectors of Motronic's Doug use 1000cc IIRC

@ Papvas Aron used to have RC 750cc Injectors I know because he sold me them