When should you upgrade your injectors?
Thread Starter
Former Vendor
Joined: Nov 2005
Posts: 8,995
Likes: 2
From: Spring Texas
St. Jude Donor '08
When should you upgrade your injectors?
Big cubes, Forced induction, and NO2 aside, when is is a good idea to upgrde your injectors to support your engine's power mods?
Racer
Joined: Jul 2008
Posts: 264
Likes: 0
From: Spring Tx
You live right around the corner from me if i remember right. EG tuned my car recently.
at 426 RWHP, my stock injectors hit 110% duty cycle at around 6k RPMs on a dynojet.
I upgraded to 42# and now am around 50% DC
EDIT: If I had it to do over I would have bought 60# so i would never have to upgrade again. When I go FI, i will put in 60 and sell the 42s since I have to pay for a new tune anyways. Also, with a 110% DC on a dyno, it may be higher on the street when under heavier loads.
at 426 RWHP, my stock injectors hit 110% duty cycle at around 6k RPMs on a dynojet.
I upgraded to 42# and now am around 50% DC
EDIT: If I had it to do over I would have bought 60# so i would never have to upgrade again. When I go FI, i will put in 60 and sell the 42s since I have to pay for a new tune anyways. Also, with a 110% DC on a dyno, it may be higher on the street when under heavier loads.
Last edited by ttribe; Jul 27, 2009 at 06:03 PM.
Thread Starter
Former Vendor
Joined: Nov 2005
Posts: 8,995
Likes: 2
From: Spring Texas
St. Jude Donor '08
Stubner Airline betwen Louetta and Spring cypress?
Racer
Joined: Jul 2008
Posts: 264
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From: Spring Tx
I live off Kuykendahl between 2920 and Woodlands Parkway 
Have too hook up some time, I'd like to see the corvette that can be seen from outer space
Unless you already upgraded injectors, I am pretty sure the c5z comes with 26 or 28#, not 32s.
Have too hook up some time, I'd like to see the corvette that can be seen from outer space
Unless you already upgraded injectors, I am pretty sure the c5z comes with 26 or 28#, not 32s.
Thread Starter
Former Vendor
Joined: Nov 2005
Posts: 8,995
Likes: 2
From: Spring Texas
St. Jude Donor '08
I upgraded to the 32s when my origionals started failing.
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From: Gone
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St. Jude Donor '03
Some tuning should be done before deciding if larger injectors are really needed.
If the car is running rich at WOT (and adding headers, heads, cam etc w/o tuning will cause exactly that)...the reported injector duty cycle will reflect that and read higher than what it needs to be, for those given modifications, simply because the PCM (mis)calibration is adding more fuel than necessary.
If the measured AFR is tuned in and acceptable, and duty cycle is still much over 80%, then an upsize is in order.
Generally speaking, the stock 28# injectors should be good to at least 410-420 rwhp. They will handle all bolt-on mods with ease, and many cam-only cars.
For most heads/cam cars, the red top SVO 30s will work nicely and support over 450rwhp no problem.
Above that...there are some 36-38# options out there for the 470-520rwhp range, and 42s should work good in the 550rwhp ballpark.
Larger injectors don't make more power, they only feed the power the engine is capable of making. Size them correctly (bigger is not always better), and enjoy a good running car.
If the car is running rich at WOT (and adding headers, heads, cam etc w/o tuning will cause exactly that)...the reported injector duty cycle will reflect that and read higher than what it needs to be, for those given modifications, simply because the PCM (mis)calibration is adding more fuel than necessary.
If the measured AFR is tuned in and acceptable, and duty cycle is still much over 80%, then an upsize is in order.
Generally speaking, the stock 28# injectors should be good to at least 410-420 rwhp. They will handle all bolt-on mods with ease, and many cam-only cars.
For most heads/cam cars, the red top SVO 30s will work nicely and support over 450rwhp no problem.
Above that...there are some 36-38# options out there for the 470-520rwhp range, and 42s should work good in the 550rwhp ballpark.
Larger injectors don't make more power, they only feed the power the engine is capable of making. Size them correctly (bigger is not always better), and enjoy a good running car.
