740cc injectors with stock turbo?

[Destructodc74]

so i got a good deal on some tomei 740cc injectors and wanted to know what peoples input/personal experiences were. ive got a basically stock s14 sr with stock t28 and wanted to know if these were way too big to run on this. i was hoping to peak boost at liek 20psi or would that be bad on the stock turbo as well? ive got a fmic and everything and ive seen people run 20psi on these t28s, so basically can i run these 740ccs with a tune or should i sell them and get some 550s?

[Monooxide]

so i got a good deal on some tomei 740cc injectors and wanted to know what peoples input/personal experiences were. ive got a basically stock s14 sr with stock t28 and wanted to know if these were way too big to run on this. i was hoping to peak boost at liek 20psi or would that be bad on the stock turbo as well? ive got a fmic and everything and ive seen people run 20psi on these t28s, so basically can i run these 740ccs with a tune or should i sell them and get some 550s?

The 740s would be nice to have if you plan on going over 350WHP later.

20 PSI is too much for the S14 T28. I would put it at ~14-15 PSI as that is about the most HP you're going to see out of it. Anything more is going to give you more peak boost torque but the same horsepower as it will fall off to redline. Also the extra heat from 20 PSI won't be good for the engine.

However running 740cc injectors isn't bad if you have the engine management such to control them.

[S13 curtis]

The 740s would be nice to have if you plan on going over 350WHP later.

20 PSI is too much for the S14 T28. I would put it at ~14-15 PSI as that is about the most HP you're going to see out of it. Anything more is going to give you more peak boost torque but the same horsepower as it will fall off to redline. Also the extra heat from 20 PSI won't be good for the engine.

However running 740cc injectors isn't bad if you have the engine management such to control them.

keep 740's


I ran 20psi with a s15 T28 definately made more power then at 15psi i was on E-85. If im right e-85 burns cooler (keep the temps down a bit) and cleaner, I had E-manage blue, DW 740cc injectors apex 1.1, ARP, built head. I wouldnt go any higher than 19-20psi on race fuel with that turbo.

[Destructodc74]

The 740s would be nice to have if you plan on going over 350WHP later.

20 PSI is too much for the S14 T28. I would put it at ~14-15 PSI as that is about the most HP you're going to see out of it. Anything more is going to give you more peak boost torque but the same horsepower as it will fall off to redline. Also the extra heat from 20 PSI won't be good for the engine.

However running 740cc injectors isn't bad if you have the engine management such to control them.


you think the t28 would be just a heat pump at that psi? ive seen plenty of people do it and if im not mistaken s14 and s15 t28s are pretty similiar right? also can i fine tune injectors that big with a SAFC? or reccommend getting some other kind of tune?

[Destructodc74]

keep 740's


I ran 20psi with a s15 T28 definately made more power then at 15psi i was on E-85. If im right e-85 burns cooler (keep the temps down a bit) and cleaner, I had E-manage blue, DW 740cc injectors apex 1.1, ARP, built head. I wouldnt go any higher than 19-20psi on race fuel with that turbo.


i probably wont be running anything other than pump gas. but if i just drop them in will the tune be way too rich and out of wack to even run right? ive got arp headstuds/ cometic metal HG/ acl race bearings/ rocker arm stoppers. its pretty much a rebuilt failsafe motor for reliability. should i just bring the injectors to a tuning shop if i want to run higher psi. i was running 10lbs with stock 370s and everything on my s13 sr and it was fine but i dont want to lean out my s14 sr by pushing it.

[Monooxide]

i probably wont be running anything other than pump gas. but if i just drop them in will the tune be way too rich and out of wack to even run right? ive got arp headstuds/ cometic metal HG/ acl race bearings/ rocker arm stoppers. its pretty much a rebuilt failsafe motor for reliability. should i just bring the injectors to a tuning shop if i want to run higher psi. i was running 10lbs with stock 370s and everything on my s13 sr and it was fine but i dont want to lean out my s14 sr by pushing it.

I don't have any first hand experience however a friend of mine with an S14 SR went from ~14 to ~19 PSI and made maybe 12 more WHP. He made like 290 WTQ and 280WHP. If 5 more PSI only makes ~10 more HP than your turbo is working way too hard and is way out of it's efficiency range. The S15 turbo is different than the S14 unit on the compressor side.

I personally made 273 WHP and 280 WTQ on ~14 PSI. Honestly that's a pretty damned fun car on stock turbo.

[Destructodc74]

I don't have any first hand experience however a friend of mine with an S14 SR went from ~14 to ~19 PSI and made maybe 12 more WHP. He made like 290 WTQ and 280WHP. If 5 more PSI only makes ~10 more HP than your turbo is working way too hard and is way out of it's efficiency range. The S15 turbo is different than the S14 unit on the compressor side.

I personally made 273 WHP and 280 WTQ on ~14 PSI. Honestly that's a pretty damned fun car on stock turbo.


what was your setup like? stock injectors? stock tune?

[4x4le]

safc=no even if you get the air fuel correct you just messed up the most important part of the tune (the timing) which your stock ecu isnt even tuned for boost levels that high in the first place. Take the advice from everyone and dont argue it. They are right. With the s14 turbo you dont want to run more boost than 15psi. Even if you had the s15 turbo you dont want to turn it up past 17psi. I run over 20psi on my t28, but its much different than your t28...... there are several t28s out there. You dont want to run much over 17psi on pump gas either or your tuner will really need to know his stuff and you better hope nothing ever goes wrong and that you never get bad fuel.

[Monooxide]

what was your setup like? stock injectors? stock tune?

Stock everything minus FMIC and Full Exhaust(including manifold).

The friend who made 280WHP was same mods minus exhaust manifold and he had SAFC NEO and 440cc injectors.

[Destructodc74]

Stock everything minus FMIC and Full Exhaust(including manifold).

The friend who made 280WHP was same mods minus exhaust manifold and he had SAFC NEO and 440cc injectors.


thanks that helps alot to put me in the guessing range for my numbers. on a tune hopefully i can make a good 275 right there also. i have the supporting mods for more boost just not positive what i need. i have the injectors. so possibly just a bigger turbo and a tune i guess. now i just have to find a place that tunes....

[Destructodc74]

safc=no even if you get the air fuel correct you just messed up the most important part of the tune (the timing) which your stock ecu isnt even tuned for boost levels that high in the first place. Take the advice from everyone and dont argue it. They are right. With the s14 turbo you dont want to run more boost than 15psi. Even if you had the s15 turbo you dont want to turn it up past 17psi. I run over 20psi on my t28, but its much different than your t28...... there are several t28s out there. You dont want to run much over 17psi on pump gas either or your tuner will really need to know his stuff and you better hope nothing ever goes wrong and that you never get bad fuel.

honestly i dont understand how a safc messes with your timing. i thought it just adjusted your maf to read higher or lower voltage. like... your timing has a chain how could it mess with it. can anyone explain this to me?

[90drftsx]

CAS messes with your timing...look it up. And to monooxide, what dyno were you using? I call bs without dyno sheet.

[Monooxide]

honestly i dont understand how a safc messes with your timing. i thought it just adjusted your maf to read higher or lower voltage. like... your timing has a chain how could it mess with it. can anyone explain this to me?

You have mechanical timing and then you have electronic advance and retard. However I don't know a lot about SAFC. I am sure it can adjust the electronic timing.

[Monooxide]

CAS messes with your timing...look it up. And to monooxide, what dyno were you using? I call bs without dyno sheet.

Ugh...

http://coupedup.net/gallery/mods/Dyno273WHP.jpg

It was a Dynapack 4000. The owners of the dyno who I lived with and know very well have dyno'd their personal test car on the same day within hours of one another on a Dynapack and local Dynojet and the Dynojet measured ~7 more WHP than the Dynapack so don't just blindly say that Dynapacks inflate numbers. This was on a ~230WHP car.

Here is the post on a local forum for the gentlemans car I mentioned about 280WHP. The graph was on the forum but the link has become broken.

"the first pull (274) was in third gear and the second (280) was in fourth gear, and as you can see they didnt get size it right to get all of the fourth gear pull, but the first one in third shows the powerband quite well. Vang's dyno performance in tulsa had their grand opening last night...."

[4x4le]

The more air you flow the more fuel the maf tells the ecu to use, aswell as how much timing to pull.

Now slap on new injectors and a safc. You are tricking the ecu making it think less air is flowing to make it use less fuel. Probably not that big of a deal at idle... now start running more boost than stock with a bigger turbo and your reallu screwing up the timing. It. may make good runs on the dyno, it may last a year, but you can bet that somewhere within your rev range youll have detenation, and that will be the reason for your engines short life.