Just tried to run the numbers on what size injectors i wanted to get and came up with 850's. well, sent the 550's off to RC and few weeks later i got them back and put them in.

well, did a test run and turns out that in second gear, it breaks up at about 6k or so and does it earlier as i go through the gears. so, figured i was dumping too much gas in and flooding everything out.

well, put my stock intake back on and my boost dropped from 18-20psi to 10-11psi and it bogged out much sooner, which was expected.

i got the larger injectors because i was running out of fuel with my stock ones with the SP, intake, exhaust, and 18psi. prolly should've gone with 720's like everyone else. i'll save the 850's for when i get the front mount. i'm hoping they won't be too large after that. i know, i need a fuel controller.

 

i put the stock injectors back in and left the stock intake on. my boost goes up to about 10-11psi and starts falling off at about 5500. and ends up at 7 or so before i shift. kinda sucks now, but i don't feel like running 18psi with insufficient fuel delivery.

 

Well..... get one?!

You need a fuel controller with any differently sized injectors than what the car came stock with.

 

ya, i know, i was hoping to get the math right and size the injectors to exactly what i have and save the money in the S-AFC

 

Dude, runnin 18psi on (presumably) the stock turbo is silly enough even with the correct fuel, buy a fuel controller AND new injectors if you want to run much above 10psi.

 

there's been stories floating around about the turbo failing by boosting so much but mine is still working fine. i had high boost for a couple weeks and didn't hurt a thing (as far as i know)

i was just excited that it pulled so hard. i imagine it would have pulled much better if i had a better IC. i'm pretty sure that the air was hardly being cooled by the top mount at those pressures.

 

Yes well our eyes can't exactly see the internal bushings and seals in the turbo can they...
But hey it's your turbo not mine

And no, at 18psi on the stock top mount IC you would've been getting about two-poofteenths of **** all cooling ability.

A fuel controller now + new injectors + new pump + new IC = Much cheaper than a new engine not too far down the road... And will be faster to boot.

Just my opinion.. thats all.

 

and to think, i just spent 2500 for the motor that's in it now only 7k miles ago.

if this turbo goes, i'll just put my spare one on, turn the boost down and wait till i get a FMIC.

oh, i have a 255lph already.

 

yeah thats a lot of boost, it would suck if that turbo catastrophically failed and took out your motor/car

 

OOHHHH, you're talking shaft speeds. hmmm, didn't think about that. i wonder how fast it is going??

 

Man, EFI just doesn't work like that. The ECU is measuring the airflow and adding more fuel as required. If you change the size of the injectors you screw that calibration up completely.

You don't need to change the injectors until they exceed 80-85% duty cycle. If you have problems with lean mixtures before then, you need a better fuel pump to maintain fuel pressure or a fuel controller to adjust the fuel map. The injectors are the last thing that needs to be upgraded, not the first.

 

already have a 255lph pump. i would like to run the parallel fuel rail set up but haven't taken the time to look farther into it. maybe i'll do that and up the pressure some to get rid of the stumble at high rpms.

oh, with the stock injectors, there was a stumble at hight boost (18) at high rpms (6k+). was told by a supra guy (http://gscmotorsports.com) that it was running too lean. i guess upping the pressure would help but don't know if higher pressure would be enough to make it run the proper A/F.

 

Before you go blaming **** that might be totally wrong, why don't you get a wide-band or an EGT and confirm if it's true?

Running too rich can also cause high RPM hesitations.
Try and pull your plugs out to see if they are white or black!



-Ted

 

Well call me mad but he has a Streep port full exhaust/intake and was running 'high boost' (18psi) on the stock injectors and presumably stock ECU..

I think lean would be right....

 

850s with no fuel control?....

 

well, there was quite a bit of difference between the rich stumble and the lean stumble. besides, my A/F guage was showing way rich when it stumbled with the 850's. when doing this, it ceased to make more boost or accelerate.
the *lean* stumble felt more like an intermittent miss. boost remained high and was still pulling hard. and i believe it neared the 100% duty cycle.

agreed. i'd also like to check my compression. but, i'm short on cash right now and figured i'd just leave my stock intake on for a while till i can afford to straighten things out. my car is in dire need of dent removal and a paint job. after that, suspension. then back to the motor.

thanks for your help everyone.

Craig

 

ahh, figured too much fuel is safer than not enough.

besides, 850's with no fuel control is nothing compared to 18psi at 5k+ rpms with low fuel delivery.

 

what does it mean when the plugs are white or black? and when should i check the plugs warm? cold?


thanx for the info

 

Black plugs=running rich
White plugs=running lean

Doesnt matter when you check them. Cold is probably better so you dont burn yourself.

 

Those injectors are fire-hosing 27% more fuel into the engine than they should. The difference between a safe 12:1 AFR and a dangerous 13:1 is only 8% more fuel. Do you see your massive overkill here? It's no wonder it's running like ****.

Like I said before, fuel pump, then fuel control, then fuel injectors.