Do I need bigger injectors yet?

adisont

Registered User
I have a 93 sc, late model blower w/ 10%, c&l 73mm maf, no cats, magnaflow res, dynomax catback, k&n, ebay cai without the bend into the fender. everything else is stock. Everything else is stock. it is making some where around 15 psi as it pegs the stock gauge at wot. Didn't know if i need to step up to a larger injector or not. also, i've got a engine analyzer that will show the pw of the injectors in ms. what is concidered 100% duty cycle for the 30lb units.
 
Yes, you do.

I made 270rwhp and 388rwtq with an MP inlet, unported late model blower with 5%OD, catless exhaust, and a 3" intake tube as my only mods and ran out of injector. I had 30's, by the way. I never went below 12.5:1 AFR so I would say that 250rwhp is the highest possible HP that you can have with 30's. Maybe not even that.

If you ran larger injectors it makes room for you to modify the car further. If I were you, I would get a set of 50# high impedance injectors from www.racetronix.com You will be modifying for a while before you need to upgrade again from those. If not, then 42's will be fine as well.

If you get injectors you have to get the correct sampling tube for the MAF, a chip (SCT $250), and of course a tune.
 
Injector duty cycle is only part of the equation. You'll need to monitor AFR and injector duty cycle at the same time to determine if you need bigger injectors. The stock programming calls for 11.0 AFR but best power is generally obtained around 11.8 AFR. So if the EEC is commanding 11.0 AFR it may run out of injector at a low rpm in it's attempt to maintain 11.0 but if it were targeting the desired 11.8 AFR then you'd be able to get more out of them.

Many people run their injectors at 100% duty cycle to achieve 11.8 AFR on the top end and don't consider themselves to be out of injectors. This is common if not entirely desireable.

To answer your other question, 90% duty cycle @ 11.8-12.0 AFR after tuning would be considered max tunable range for any injector. Beyond 90% duty cycle the car won't necessarily go lean and self destruct but it will no longer be tuneable and would be considered "out of injector".
 
a late model blower and a 10% pulley is actually being overdriven 13% and is heating up the air charge tremendously, you need at least an intercooler fan or even better to get a double intercooler and fan to cool down the air going into the motor.
 
i've got a 12" fan on the front side of the intercooler. i've been getting a check engine light. it will come on and go off with in a few seconds. I really don't have plans to go with any futher mods. I know the act's will be high with the 10% (13%) on the blower. i've got a stock early pulley i have been thinking about putting on, i just have to give up the low end. thanks for your help guys. i'll be on the look out for some 42's and a sample tube. i also have a 190lph fuel pump in the car.
 
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