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Hey, I want to ask you guys some questions about my TBI. I'm close to switching to carb, but I love the TBI system and would love to keep it. My motor is a 350 with Vortec Heads and a LT4 Hotcam.
1. Does TBI limit power? I've heard people say that it limits power to around 375hp. Is this true? Would a 454 TBI help? I have one.
2. Where can I get my TBI tuned? My TBI runs rich. At idle and even at WOT. I've heard about EBL flash and sounds like a great system. But I just don't have the time to learn it. I have electrical school coming this fall.
4. Does dyno tuning work with TBI? And how would I prep the car for it? Would I put the 454 TBI on? Or just leave the stock TBI with the 350 injectors in? Would I need an adjustable fuel pressure regulator?
Sorry for bombarding you guys with questions. I just really want to keep my TBI.. It would be awesome if you would reply!
i had and tried tuning with a tbi with out any ecu upgrades 347 at the wheel with a 350 and 454 injectors was as far as i could go...mpfi was the next upgrade with dynamic efi and a procharger...all tbi motors were obd1 so a modification to the ecu is recommended for tuning
Oh it’s been a long time since I’ve messed with this stuff but I’ll give it a go. Seems like if you get the throttle body y bored out, it goes a long way. My 383 that I built would run out of fuel at 5900 rpm at 42 psi on 454 injectors and my AFR was around 10:1. There is a lot of room but there is a limit
Oh it’s been a long time since I’ve messed with this stuff but I’ll give it a go. Seems like if you get the throttle body y bored out, it goes a long way. My 383 that I built would run out of fuel at 5900 rpm at 42 psi on 454 injectors and my AFR was around 10:1. There is a lot of room but there is a limit
You do know that you would be over driving those injectors at 42psi no matter what. They are only rated for a max pressure of 33psi. I can't believe that they did not go static and burn up at that setting. My 383 is running 454 injectors at 30psi and I can run it to 6,300 rpm with no issues and my DC is around 85/90% for a short time. Your AFR being 10 is way to rich at WOT also. An AFR of around 12.6 is a much better range to be at when WOT. An EBL is the only way to go with a modded CFI motor no matter what mods you are running to include spray.
Last edited by Buccaneer; Oct 24, 2022 at 09:03 PM.
You do know that you would be over driving those injectors at 42psi no matter what. They are only rated for a max pressure of 33psi. I can't believe that they did not go static and burn up at that setting. My 383 is running 454 injectors at 30psi and I can run it to 6,300 rpm with no issues and my DC is around 85/90% for a short time. Your AFR being 10 is way to rich at WOT also. An AFR of around 12.6 is a much better range to be at when WOT. An EBL is the only way to go with a modded CFI motor no matter what mods you are running to include spray.
They will run 50-70 no problem for short duration (rising rate FMU). Been there and done that. The high pressure version of the 61s used on the Big Block TBI Marine applications reliably work at 58 psi. I have done that on a returnless TBI setup using a vette fuel filter. Two of those marine TBIs used on the 575SCI will support over 800 crank HP without raising the pressure over the supplied 32 psi. The 61# high pressure injectors running at 32 psi injectors are 104 lb/hr each. Then you have the huge Brazilian I6 injectors that fit in the medium duty truck/GM industrial injector pod. Alot of 4.3L powered forklifts used those pods.
Do you have part numbers? I've never heard of high pressure 61# injectors or I would have maybe tried them. Sounds odd though that they could possibly support 800hp. Hey Bob, have you heard of these and being able to support that much power?
The 61# high pressure injectors running at 32 psi injectors are 104 lb/hr each...
Not sure where you are getting that info from, but that's not correct. A 61# injector @ 32psi is only 95.7#phr and 191.4#phr for two and will only support up to 362hp. Mine are 80# @ 13psi and 90# @15psi So, @30psi they are running 121.5#phr and 243.1#phr total with a support of 460hp. I feel my motor is very close if not more to that now with the current tune, but we shall see this Jan/Feb at the track if my tire comes in that I have been waiting for since Aug.
Last edited by Buccaneer; Oct 26, 2022 at 03:55 PM.
Do you have part numbers? I've never heard of high pressure 61# injectors or I would have maybe tried them. Sounds odd though that they could possibly support 800hp. Hey Bob, have you heard of these and being able to support that much power?
Not sure where you are getting that info from, but that's not correct. A 61# injector @ 32psi is only 95.7#phr and 191.4#phr for two and will only support up to 362hp. Mine are 80# @ 13psi and 90# @15psi So, @30psi they are running 121.5#phr and 243.1#phr total with a support of 460hp. I feel my motor is very close if not more to that now with the current tune, but we shall see this Jan/Feb at the track if my tire comes in that I have been waiting for since Aug.
61 lb/hr @ 11 psi works out to 104.04 lb/hr at 32 psi.
As I said above the 575 SCI that I tuned that had a blower upgrade made a little over 800 hp at the crankshaft or 400 hp per TBI unit. With the tiny stock blower and the pathetically weak amount of boost it made that engine was 575 hp to start with.
0.50 bsfc might suit a low output stock engine. As the engine starts becoming more efficient because it has inreased compression, higher flowing aluminum heads and a decent roller cam the BSFC will decrease noticeably. My aluminum head 11:1 383 is about 0.42 BSFC. The stock Vortec spider running it was 19 lb/hr @ 43.5 psi and a resulting 24.1 lb/hr @ 70 psi. The engine makes ~500 hp @ 5,700 rpm on top-end charge. I was able to make ~450 hp @ 5,000 rpm from the 24.1 lb/hr spider. I ran it for 6 months on the stock spider with the shift points and fuel kill set to keep the injectors under 95% duty cycle.
Well here is the info right from the EBL Utility for injector BPC calculation and you are way off on your findings...jus sayin'.
As I said before 4 of those 61# high pressure had zero issues fueling at 800 hp at the crank. I also ran a pair of those on the 350 in my G20. I made 370 hp at the tires and was not over 85% duty cycle.
