What is the biggest problem with making power with a TBI system? Is it air flow, fuel flow, what just wondering.
Thanks
Casey

 

From what I understand, in high HP applications, fuel delivery is the main problem.

 

actually, i don't think that's correct.

you can go to a 454 tbi, run 90 lb/hr injectors and raise the fuel pressure significantly to increase fuel flow.

it's airflow that chokes tbi down. the biggest tbi i know of is a 454 tbi sleeved and bored out to 2.2 inches.

http://www.454ss.com/gallery/JimD/JimD_TBI.htm

at the very best, you're looking at maybe 700 cfm@ 1.5"hg. va454ss has one on his ss454 pickup and it's boomin'.

 

yea, its definitly air flow and not fuel flow.

thats why people spend all the time and money making/buying bigger tb's, porting out heads, new intakes, headers, stuff like that. The poor lo3 is just really choked up and if you want any kind of real power you're going to have to open her up a lot....or spray it.

-chuck

 

It's funny but I'm starting to think that it's both.
The fuel is introduced before the throttle blades, this fuel takes up air space. This is why most wet flow intakes require larger runner volumes but length is decreased to ensure fuel suspension. It's a catch 22, really gets on my nerves just thinking about it.
I've shown in air flow that the 2" TB stock from holley is good for nearly 330hp without taking more than a couple peak hp. I'd give the larger 2.2" bore TBI up to 375hp before it's probably slowing the vehicle down noticably vs a larger carb in the 1/4 mile.
With that being said, go 4 barrel TBI . Lots of air, lots of fuel. Now you only have to worry about idle since the injectors are large and fire frequently! Probably require usage of a VAFPR.
Dry flow, the 2" bore would be plenty of air for 375hp or more without taking much from peak. A good way to get back your peak HP is to enlarge your plenum volume. A good spacer can do this. Also, if you run a large plenum it's probably a good idea to run a coolant crossover to keep the manifold warm enough to aid in keeping the fuel in suspension for even cylinder distribution and less pooling of the fuel when you go WOT.

 

I dont know but I have been told that the TBI has poor high RPM ability because the injectors cant open and close fast enough, thus limiting HP by allowing proper fuel timing only in the lower to mid RPM range