2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

FC turbo injector sizing

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Old Mar 9, 2013 | 09:11 AM
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FC turbo injector sizing

Hey,
I'm trying to put a butcher'd FC back together. The car is a 1990 jdm stock turbo. Someone put a megasquirt in it and did a BAD job. I have gotten a harness and all that was missing, minus the injectors. I want to go to a Rtek 1.8 chip upgrade with 720cc or 750cc injectors all around. I also have a turbo setup from another car I was hoping to add. I'll post specs below

My Questions:

How do you choose the size of injectors to use? I was hopiong to use 720 or 750 so I could stay with the 1.8 chip.

Would a Rtek 1.8 work ok with a upgraded turbo or do i have to go to a 2.0 or 2.1?

I will be running 7psi, will the stock s5 motor handle this?

Specs:
Car is stock 1990 jdm Turbo II
60mm turbo with 0.62AR cold side and 0.82AR hot side
Turbonetics evolution wastegate with 7 psi spring
front mount intercooler
stock motor (no porting or upgraded apex seals)
have not bought injectors yet.
N374 ECU

I have a stock s5 turbo but it is questionable.

Thanks for any help.
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Old Mar 9, 2013 | 09:31 AM
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Also the leading coil has 3 wires coming from it, 2 go into a connector and the other one (black) is cut. Is the cut one a ground?
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Old Mar 9, 2013 | 10:06 AM
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I think I have heard the stock motor can handle 12psi could be more not for sure but can't go over 9 if u still have fuel cut but with the rteck has built in fcd
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Old Mar 9, 2013 | 01:26 PM
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The black single wire on the leading coil doesn't need to be hooked up to anything. You could use that for a tachometer signal if needed.
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Old Mar 9, 2013 | 01:53 PM
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My engine runs with up to 14psi with 4 750cc injectors and they aren't maxed out. The engine internals are still stock.
I don't think you would get problems if you use a 1.8 chip with only 7psi.
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Old Mar 10, 2013 | 06:34 PM
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Cool, thanks for the info guys. That put my nerves to rest.
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Old Mar 11, 2013 | 05:43 AM
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Originally Posted by rotaryguy481
I think I have heard the stock motor can handle 12psi could be more not for sure but can't go over 9 if u still have fuel cut but with the rteck has built in fcd
Past about 12psi to the TMIC can no longer cool efficiently.
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Old Mar 11, 2013 | 12:31 PM
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Originally Posted by 87Adam
60mm turbo with 0.62AR cold side and 0.82AR hot side
Turbonetics evolution wastegate with 7 psi spring
More info on this turbo is needed before anyone can give you a real idea if a simple non-programmable rtek chip & 4x720cc injectors will work alright as a temporary solution. What compressor wheel is in it? By 60mm do you mean it has a 60-1 wheel? For any aftermarket turbo, a programmable computer is strongly advised. If it is a 60-1 compressor, running only 7 psi is going to make for a slow, laggy setup. A stock turbo would make for a faster car.
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Old Mar 11, 2013 | 09:49 PM
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Thanks, I'm not to conserned about the lagginess of the turbo. It was in another car that I had the chance to drive and it pulled good with a large range. That setup only ran 7 psi. My main issue is the fuel and fuel management. They had a megasquirt and they didn't tell me what injectors they ran. So I'm trying to decide what to use myself. I think I have decided on 750cc injectors and think I'm going to spend the extra $$ on the rtek stage 2 upgrade.

I'm pretty new to the turbo scene and probably made a mistake by not getting more info on the turbo but thats all the info I was given. The guy I bought it from was the one who butchered the car and hooped me big time for it, so him and I are not exactly on speaking terms to ask for more info.
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