Will the TBI system in my 89 camaro run a 383 stroker, i cant understand why it wouldnt but a frined says it wont, also, ive read an article where a guy has scrapped a tbi unit out of a truck and stuck it on a HO350, is this something i might have to do. BTY cant go to carb, emmisions police say nono

 

sorry didnt put before but its a rs with a tbi 305

 

tbi can be tuned to handle anything, jsut like any other electronically controlled engine. as long as you put an effort into getting enough air adn fuel into teh engine, the computer will be able to control it for you.


later
tim

 

The Holley 670cfm unit should be able to handle it. Don't plan on using the stock TBI unit.

 

ok, but the stock ecu wont run a higher output engine, so what do i do?

 

the computer doesn't care how much hp your car has. all teh same perameters can be adjusted on a 170hp stock engine as on a 400hp street/strip motor. as long as you have enough air and fuel getting into teh motor, the ecm can be tuned to handle it jsut teh same.
there is no problem with our computers, they can even be improved upon for cheap to sample quicker and use wide band O2 sensor, it is only like a 50 or 60 buck upgrade.

later
tim

 

what upgrade to the computer are you talking about and how can i do it

 

go to teh diy prom board and and search for the lockers system

later
tim

 

tim, you said:

"the computer doesn't care how much hp your car has. all teh same perameters can be adjusted on a 170hp stock engine as on a 400hp street/strip motor. as long as you have enough air and fuel getting into teh motor, the ecm can be tuned to handle it jsut teh same."

i get that, but there are still the limits of how much air and fuel tbi can flow, aren't there? i've been going nuts trying to find that out.

first, there's figuring out how many cubic inches tbi can support with airflow. the formula i have for it is:

Volume in ci / 2, X rpm, / 1728, X %VE = airflow

using that formula, for example, a 400 that i wanted to redline at 5,600 rpm would need 644 cfm of airflow (assuming 95% volumetric efficiency). Holley says dual plane intakes like 10-20% more. 10% more airflow would mean 708 cfm; 20% would mean 772 cfm!

the first thought that comes to mind is that a 670 cfm holley bored out to use 53mm throttle blades might do it, but apparently there's something different in the way cfm for 2bbl carb and tbi units and 4 bbl units are calculated, and the above formula is based upon the 4 bbl method.

i desperately want to calculate the maximum cubic inches supportable by tbi, but need answers to be able to do it.
does anyone know what the heck i'm talking about? help!

(applying the above formula, by the way, a 305 at 5,000 rom would need 423 cfm, yet the factory units are only rated at 400, right? a 454 would want 623 cfm @5,000 rpm)

the second thing i'm tring to figure out is how many horsepower can a tbi unit support with fuel?

Holley's website has a tech article on calculating injector size:

http://www.holley.com/HiOctn/TechSer...l/Artcl07.html

the formula is: injector size = (engine hp (flywheel) X bsfc) / (# of injectors X duty cycle).

using that formula, a 400 hp tbi engine would need 2 111 pph injectors.

a) 90 pph is as big as they come, right?

b) i know increasing fuel pressure increases lbs per hour, but how much? how high can you safely increase fuel pressure?

(using that formula, a 170 hp 305 would need 2 47 pph injectors. they came stock with 40 pph injectors, right?

can someone help me with this? the most important question for me is the difference in calculating cfm between 2 bbl and 4 bbl induction systems.

 

what are the most hp, which u get from a stock tbi?
and how much, if you do a little work on the stock one?
greetz

S!MON

 

This topic has been brought up a few times before. Here are some links:

here
here
and here

If I remember correctly, the 670 TBI when measured the same way as a 4bbl flows 485cfm. But don't quote me on that.

 

wow, that helps a lot. i'm not far away from a headache, but that's worth it!!!

thx

S!MON

 

fuel is teh greater limit, look into big block injectors and you shoudl be ok. even if you have to turn up teh pressure slightly.
those total air formulas were started back in teh day of carbs and points. with fuel injection they tend to be over estimates of teh needs. a 670 cfm tb can support a moto rlike you are talking about very nicely, more cfm woudl make more peak hp, but teh 670 will make a better torque curve that comes on lower and lasts longer.

later
tim