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Injector size?

Joined
8 November 2003
Messages
2,412
Location
Portland OR
All this talk of high boost CTSC makes me wonder if there would be a down side to running bigger injectors for the standard boost set up? Will the basic FMU just back off the pulses to compensate and does the stock fuel pump run out of volume when one goes to a larger volume injectors?

I feel a bit like if there is not a problem don't fix it, but it seems like A/F plots for stock injectors seem to lean out at 7K RPM. Is it good insurance to have the bigger injectors for track work where I have long runs at high RPM? Will I lose idle quality or milage? With the stock injectors and std. boost set up idle is solid and the car will get 27 MPG on the highway @ 70 MPH. Pretty cool for a car that is still fast enough to scare me now and then.
:)

Dave
 
Well, the FMU does not alter the injector pulse. The CTSC utilizes strictly stock injector control, but increases pressure so the same pulse width delivers more fuel. Larger injectors (as used in their high-boost kit) won't make up for a pump that can't deliver the intended volume at any pressure, but could compensate for a pump with enough capacity but not able to make the pressure expected by the FMU. However, if you run larger than stock injectors then the ECU will just trim them back to get the right mixture at idle anyway so I'm not sure what you gain. Go too big and the ECU can't compensate, which will leave you way rich off-boost. I suppose that if your pump can deliver on the volume you could increase injector size, decrease base pressure, and then fiddle with the pressure rise slope. (Bell still sells an adjustable FMU/RRFPR)

Overall this may be a lot of work and not prove beneficial.
 
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