Injector size
Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
Re: Injector size (POLOVETTE 94)
It really depends on the state of tune and the amount of boost available. Even in a mild state of tune say 6 psi of boost for a 383 one can run 42lb/hr injectors easily. I am running 42's myself in a 396. Some may say its too small but so far I have not had any problems. I don't race the car as its more of daily driver than anything else but even an occasional burst of WOT I don't see any fuel problems at all and that is verified with a couple different scan tools.
Some stock kits that produce 6 PSI of boost will most often use the stock injectors. On say a 94/95 Vette vortec does not change out the injectors. Instead they use a FMU for fuel enrichment under boost. Of course the correct way is to size up to a correct size injector and program the PCM or ECM for the proper fuel curves.
If I decide to build a intercooler and upsize to a T trim blower I may go to some low impedance 75lb injectors. But that is long in the planning stages for now. Contrary to beleif large injectors can be made to run right at idle speeds. When using a low impedance adapter there is three to five times the available current to yank the injectors open for good tight control when the pw is runing in idle regions.
Some stock kits that produce 6 PSI of boost will most often use the stock injectors. On say a 94/95 Vette vortec does not change out the injectors. Instead they use a FMU for fuel enrichment under boost. Of course the correct way is to size up to a correct size injector and program the PCM or ECM for the proper fuel curves.
If I decide to build a intercooler and upsize to a T trim blower I may go to some low impedance 75lb injectors. But that is long in the planning stages for now. Contrary to beleif large injectors can be made to run right at idle speeds. When using a low impedance adapter there is three to five times the available current to yank the injectors open for good tight control when the pw is runing in idle regions.
Safety Car
Joined: May 2003
Posts: 4,283
Likes: 0
From: Houston Texas
Re: Injector size (tjwong)
I have a 383 coming in on Friday for my Vortech and after talking with fellow members, esp. Black Bart, I will be running 42lb injectors. Also if you look up a question I posted not to long ago ( injector size ) will also help add to what Tjwong has said.
[Modified by BAM92, 12:49 AM 8/28/2003]
[Modified by BAM92, 12:49 AM 8/28/2003]
Drifting
Joined: Jul 2001
Posts: 1,897
Likes: 0
From: La Fontaine Indiana
Re: Injector size (BAM92)
This is one of the most misunderstood things about engines. I have read post where people would say you don't need 30 lb. injectors use 24lb. Well if you want to leave the ecm stock that would be good advice because big injectors require reprograming the ecm. But if you are going with a supercharger and plan on making any real power you can't do it with a stock tuned ecm. So if you are going to reprogram anyway why would you use small injectors. You will read that they will reduce fuel mileage and the engine will not idle smooth as long as you don't exceed 50lb. injectors all of that is just flat WRONG.
No good reason to install small injectors with a blower I would not even consider anything smaller than 42lbs. You can run a small injector and turn the fuel pressure real high and make them flow more but they were not built to open against that kind of pressure and at high rpm the windings in the coil will overheat and fail . Above 80% duty cylce you run the risk that the injector will not flow right. Bottom line is their is no good argument to be made for small injectors on a forced induction engine.
No good reason to install small injectors with a blower I would not even consider anything smaller than 42lbs. You can run a small injector and turn the fuel pressure real high and make them flow more but they were not built to open against that kind of pressure and at high rpm the windings in the coil will overheat and fail . Above 80% duty cylce you run the risk that the injector will not flow right. Bottom line is their is no good argument to be made for small injectors on a forced induction engine.
