I have a Turbo ll motor, that's almost done being rebuilt. Here is the mods I'll be running;

89-91 Street port motor, 91 stock turbo (new), racing beat 3" downpipe, 3" exhaust all the way back, front mount spearco intercooler (33"x8"x3.5" core), cone K&N filter, Blitz blow-off valve, underdrive pulleys, lightweight flywheel, HKS FCD, Jet re-mapped ecu, walbro 255 fuel pump, greddy pro-fec B boost controller.

Okay, I looked hard for the answer to this, but cant really find anyone running a stock turbo. WHAT size injectors would be good for this setup? I have looked at many injector calulators, and its a little confusing to me, but it looks like they all say in the 720-750cc range @ 50psi, but 550cc @ 95 psi, is that the right way to do it? It says the stock ecu is running a 65% duty cycle, is that right? . I want to run as much boost without getting out of the stock turbo eff. and have too much hot air. Can I keep the stock injectors with a higher fuel psi? Do I need a boost variable fuel pressure regulator? Would the GSL-SE injectors with resistors provide enough fuel? I'm confused more now than I used to be, as I thought a all-stock second gen would take a full exhaust with defenser, and be fine. PLEASE HELP!!

 

Before any one else tells me I'm off my rocker, can I even run a stock turbo with those mods? Blue Tll stated that the boost creep would be insane, and destroy the motor. If you guys have any info, I dont mind being told I'm going to f**ck something up, I want to know before I do!!! thanks

 

GSL-SE or 720s in the secondaries should be sufficient.

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You have a s5 turbo, creep should be minimal. However, once you throw it all together and if you are creeping port the wastegate holes bigger. Kind of a trial and error thing. Of course you could always port it now and avoid any possible complications down the road.

 

you will run outa boost by 6000 rpm with a good port job. stock turbo is too small.

it probably wouldn't creep past 12psi or so. which would be fine with some bigger secondarys. like 720.

if the turbo is still off. port the wastegate

 

Thanks for the replys!!! I was planning on having the wastegate ported, since it is all new and the bolts wont be seized up. So with it ported, and 720cc's I should be fine?

 

You should be fine with the 720s.....i have in the 680s and my motor is not ported....(yet.. ) and running just a tad on the rich side.....

 

Stock injectorscan flow enough fuel for ~300hp if fuel pressure is maintained (which the Walbro will do). No, ECU's vary the duty cycle according to load, from 1-2% at idle to a max ~60% at full load on a stock car. But if you increase the aiflow through mods, the ECU will just keep increasing duty cycle to add more fuel as needed, until it reaches 100% and can't add any more. You shouldn't exceed 80-85% duty cycle, and that 300hp figure above is calculated at 80%. The stock compressor starts to rapidly loose efficiency past 10-11psi. The result is lots more heat. A FMIC helps with this, but only so much. Boost higher than that also spins the turbo faster that it's designed for, so the bearings won't last long. Yes. You already have one. All stock FPR's increase fuel pressure in line with boost pressure, keeping the two at a set difference. The FC's FPR keeps fuel pressure ~38psi higher than manifold pressure. You might be thinking of a rising rate FPR, which works the same way, except the difference between the pressures also rises as boost rises. These can help if you're running lean at high boost, but they're a pretty crude method of tuning. Unless you have a fuel controller to tune them down a bit you'll probably have too much fuel. Overly-rich mixtures result in less power, not more. The biggest problem is overboost, resulting in lots of heat and probable detonation. Adding buckets of fuel to kill the detonation is hardly smart tuning. Port the wastegate to keep boost down and you should be OK.

 

That is alot of very helpful information !! Thanks for steering me in the right direction. I was starting to think I needed a external wastegate to be welded onto my custom turbo manifold, just to control the boost. Thanks again