LT1 fuel injector size?

StockerRook · 09-09-2011, 11:15 AM

Got my motor all buttoned up and put in the car. The only thing i have left is figure out is which injectors i need to run.

Will the stock injectors work (24 lb. I think ?) or do i need to upgrade to a slightly larger injector (Around 30 lb.)

The car has a BS3 management system.

I apologize in advance for my lack of knowledge. Any help would be appreciated.

Chris

Just a couple pics of the painted engine bay.

Dan Fahey · 09-09-2011, 12:05 PM

Quote:

Originally Posted by StockerRook

Got my motor all buttoned up and put in the car. The only thing i have left is figure out is which injectors i need to run.

Will the stock injectors work (24 lb. I think ?) or do i need to upgrade to a slightly larger injector (Around 30 lb.)

The car has a BS3 management system.

I apologize in advance for my lack of knowledge. Any help would be appreciated.

Chris

Just a couple pics of the painted engine bay.

WOW big issue discussed a lot on LT1/LS1 and impalassforum.com.

The 24# injector seems to work well with 350's with just about any cam.
Fuel Pressure can be cranked to 55psi to meet demand.
I use a PCM and tune with LT1 Edit or TunerCat.

Some move up to 26# Injectors but most stick with the 24#er's.

30lb Injectors are used when our www.ECIRS.org racers move up to 383/396/409 LT1 engines and or power adders.

If you have a PCM and Laptop,
FreeScan is available to help tune the engine by recording a run.

I use a Walbro High Capacity Fuel Pump, far more than the car needs.
Infact may go back to the stock pump.

D

MOTORSPORTS Innovations · 09-09-2011, 01:12 PM

Chris - more info needed:

Are you running Speed Density or Alpha N?

What injector size is specified in BS3?

What fuel pressure are you using?

What injector size was used previously?

Rich Biebel · 09-09-2011, 01:26 PM

I used 24 lb Accel injectors in my LT-1 Stocker.

I think the present owner upped them to 30lb'ers probably because the 24's were just about wide open at some parts of a run....

The 30's did not make any difference from what I can see performance wise....

StockerRook · 09-09-2011, 02:56 PM

Quote:

Originally Posted by MOTORSPORTS Innovations

Chris - more info needed:

Are you running Speed Density or Alpha N?

What injector size is specified in BS3?

What fuel pressure are you using?

What injector size was used previously?

Motorsports Innovations,

The motor has never been started but I believe the Big Stuff Unit can operate in Speed Density OR Alpha N mode. Im not really sure of the difference between the two but initially I will prob use the mode which is easier to operate and tune. (I have zero experience with tuning a car and have much to learn). I dont believe a specific size injector is specified and I plan on running about 55 p.s.i of fuel pressure. Im using an A-1000 Aeromotive fuel pump with AN-10 lines so Im sure fuel delivery will not be an issue. I believe the stock injector size for this motor is 24 lb.

Thanks for the help to those have replied.

Ed Wright · 09-09-2011, 08:58 PM

There are fast LT1 Stockers running 24 lbs and 30 lb injectors. Personally I would use the 24lbs at 60 psi. Higher pressure atomizes the fuel better.
As far as Alpha N or Speed Density, that has no influence on required injector size. And, you can select any size you want with FAST XFI or BS3. Just type in the size you have. Remember to correct that value if you up the fuel pressure as that increases the injector flow rate.

magnumv8 · 09-09-2011, 09:07 PM

Here is the formula for selecting the proper injector for your application.....

injector size = HP x BSFC (.5 avg) over number of injectors X duty cycle (80%)

in a normal V8 with 400 HP when you plug in the numbers you end up with 32 lb. injectors....

You want to be a little large rather than too small or even close so that the injector doesn't reach a saturation point where it literally doesn't close but stays open, that is why the duty cycle is at 80% in the formula to give you a little "head room"....

Normal fuel injection flow rates are @ 43 lbs......by pushing the fuel pressure up you can fool the system into "thinking" the injectors are bigger than they actually are, fuel atomization may be a little better with more pressure, but it is best to start conservative and slowly push things until you see if there is any increase in performance AFTER you get a good tune in the vehicle.....

D L Rambo.....

Ed Wright · 09-09-2011, 09:24 PM

45 to 60 psi was worth 5 rwhp on my car after leaning it back to the same WOT air/fuel ratio. GM has been running many engines at 60 psi since at least 1996. Higher pressure doesn't make the computer "think" anything. Injector flow rate actually goes up. Many EFI racers have learned their cars repeat better when run closer to 100% duty cycle. I can't tell you why that is, but if you ask around that is a common story. High duty cycles won't cause failures at much less than ten second per run. 80% limit on duty cycles have not proven to mean much drag racing in the real world. Does sell injectors though.

09-09-2011, 11:15 AM	#1
StockerRook Junior Member Join Date: Jan 2009 Posts: 36 Likes: 0 Liked 0 Times in 0 Posts	LT1 fuel injector size? Got my motor all buttoned up and put in the car. The only thing i have left is figure out is which injectors i need to run. Will the stock injectors work (24 lb. I think ?) or do i need to upgrade to a slightly larger injector (Around 30 lb.) The car has a BS3 management system. I apologize in advance for my lack of knowledge. Any help would be appreciated. Chris Just a couple pics of the painted engine bay. Attached Thumbnails

09-09-2011, 01:12 PM	#3
MOTORSPORTS Innovations Member Join Date: Dec 2009 Location: Hainesport, NJ Posts: 123 Likes: 0 Liked 15 Times in 2 Posts	Re: LT1 fuel injector size? Chris - more info needed: Are you running Speed Density or Alpha N? What injector size is specified in BS3? What fuel pressure are you using? What injector size was used previously? __________________ MOTORSPORTS Innovations www.motorsportsinnovations.com

09-09-2011, 01:26 PM	#4
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,275 Likes: 25 Liked 510 Times in 200 Posts	Re: LT1 fuel injector size? I used 24 lb Accel injectors in my LT-1 Stocker. I think the present owner upped them to 30lb'ers probably because the 24's were just about wide open at some parts of a run.... The 30's did not make any difference from what I can see performance wise.... __________________ Rich Biebel S/C 1479

09-09-2011, 08:58 PM	#6
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 389 Times in 168 Posts	Re: LT1 fuel injector size? There are fast LT1 Stockers running 24 lbs and 30 lb injectors. Personally I would use the 24lbs at 60 psi. Higher pressure atomizes the fuel better. As far as Alpha N or Speed Density, that has no influence on required injector size. And, you can select any size you want with FAST XFI or BS3. Just type in the size you have. Remember to correct that value if you up the fuel pressure as that increases the injector flow rate. __________________ Ed Wright 4156 SS/JA Last edited by Ed Wright; 09-09-2011 at 09:05 PM.

09-09-2011, 09:07 PM	#7
magnumv8 Member Join Date: Feb 2009 Location: Coraopolis, Pa. Posts: 172 Likes: 0 Liked 0 Times in 0 Posts	Re: LT1 fuel injector size? Here is the formula for selecting the proper injector for your application..... injector size = HP x BSFC (.5 avg) over number of injectors X duty cycle (80%) in a normal V8 with 400 HP when you plug in the numbers you end up with 32 lb. injectors.... You want to be a little large rather than too small or even close so that the injector doesn't reach a saturation point where it literally doesn't close but stays open, that is why the duty cycle is at 80% in the formula to give you a little "head room".... Normal fuel injection flow rates are @ 43 lbs......by pushing the fuel pressure up you can fool the system into "thinking" the injectors are bigger than they actually are, fuel atomization may be a little better with more pressure, but it is best to start conservative and slowly push things until you see if there is any increase in performance AFTER you get a good tune in the vehicle..... D L Rambo.....

09-09-2011, 09:24 PM	#8
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 389 Times in 168 Posts	Re: LT1 fuel injector size? 45 to 60 psi was worth 5 rwhp on my car after leaning it back to the same WOT air/fuel ratio. GM has been running many engines at 60 psi since at least 1996. Higher pressure doesn't make the computer "think" anything. Injector flow rate actually goes up. Many EFI racers have learned their cars repeat better when run closer to 100% duty cycle. I can't tell you why that is, but if you ask around that is a common story. High duty cycles won't cause failures at much less than ten second per run. 80% limit on duty cycles have not proven to mean much drag racing in the real world. Does sell injectors though. __________________ Ed Wright 4156 SS/JA