What exactly limits the TBI? is it the Injectors because i dont think its the flow.670 cfm is enough to suppply 400 hp, then why is there a limit at 330 HP?

 

Who said there was a limit at 330 hp? Also, the stock tbi doesnt flow 670, thats the holley. They are flowed at 3 hg compared to a carbs 1.5 hg. So effectively a 670 holley tbi flows about 475 cfm.

 

the pratical limit is that you would make more power for less money with pretty much any other form of fuel injection...



so if you plan on making anywhere near that amount of power, its much simpler, cheaper and easier to obtain by using some other induction method...


but there are people that just like to do things the hard, expencive way....

 

so what is the limit on a TBI?

 

You need to clarify your question. Are you talking about the stock system? If so, are you including chip tuning? What injectors? What throttle body? Your question is WAY too broad.

 

I'd say the limit of TBI in general is kind of a gray area. Not many people have really pushed TBI to its limits to find out what the absolute limit is. I think the fastest TBI N/A was JPrevost with like a 13.9 or 13.8 in the 1/4. I know he was supporting good power. Also, there's now someone on the boards with a 383 TBI and I'm sure he's pulling in some big power numbers but I think he may be having some difficulty with fuel.

 

I ran a 13.42 last fall. Truck should be in the 12's if it ever quits raining!

 

Well there ya go, those are really good times for TBI; I personally don't think TBI is the limiting factor as much as people say it is usually.

va454ss, what's your setup in that truck are you running the stock 454 size throttle body or a 4-barrel? I'm curious what the specifics are on your fuel delivery?

 

I am talking about the stock equipment. Whats the most HP i can get out of using stock pieces(including big block TBI and injectors) I am not worried so mcuh about times as i am HP. What will i need to do to make it handle between 400-450 HP?

 

400-450hp, you're going to need a whole lot. I don't think its possible to produce that kind of power with any of the 2-barrel TBI units out there, you'll need a Commander 950 setup or something. You'll need a Holley 4-barrel system to get those kind of numbers.

 

I think it could be done, but you will need some seriously huge injectors and turn the fuel pressure way up to supply enough fuel. It would be interesting to see someone make that kind of hp on the 2 barrel tbi.

 

It is indeed a GM 454 TB, but the bores have been increased to 2.2 inches, versus 2.0 for stock. I am using flow matched injectors from Turbo City along with the vac ref FPR.

The ET mentioned was using an ExtrudeHoned Edel TBI manifold. Even at that, the ports in the manifold were much smaller than the ports in the heads. I had switched from the original peanut port heads to 781 castings, which are the normal large oval port size. I am also using a mild CC 264 HR cam; the rest of the bottom end is stock and the CR is 8.0. Also, when this pass was made, I was using single exhaust with the Edel shorty headers, and a stock torque converter.

Since that time, I have installed an Edel RPM Air Gap manifold, true 3 inch dual exhaust, Hughes short shaft TH400, Vigilante 2700 stall converter, alum driveshaft, Performance Distributors big cap HEI, and ram air setup. Oh yeah, and rear disc brake conversion to save some wt and slow me down faster.

BTW, all this with an off the shelf Jet chip and a truck that weighs almost 4400 lbs empty.

I have Y trim Vortec awaiting installation once I get the N/A combo ironed out. Additional fuel will be supplied by a custom auxiliary fueler that will go between the TB and the intake manifold. It will have a stand alone controller and a BTM will be used.