now im a tbi guy!

[steveo]

i'll be honest, i've never liked tbi, but i guess i will now since i'll be daily driving one.

has a gm 305 crate longblock of some description with the original tbi stuff stuck on it.

have tons of crap in the engine bay i'll be stripping out (ac, air, whatever) just 'cause a cluttered engine bay pisses me off, then i'll start tuning.

[dave w]

Seems to me like there would be room in the engine bay to convert to a LT1 engine?

BTW, the '7427 TBI PCM is an excellent upgrade for the $$!

dave w

[brian617]

Let me know if you need larger injectors, I have a clean set of 350 injectors i'd swap for a good pair of 305 injectors.

[buddrow]

Welcome to the world of TBI Steveo lol. After all the work you've put into the LT1 and you're having to "slum it" with a tbi, such a shame. :)

Buddrow

[steveo]

Seems to me like there would be room in the engine bay to convert to a LT1 engine?

sure would be, but i dont think i'll do that...one lt1 is enough lt1

[RobertISaar]

TRAITOR!

at least it's not a carb..... or e-carb.

i would probably start collecting TPI parts in your situation(or the LT1 top end if it bolts onto the existing heads?), i just can't stand the thought of anything that doesn't have one injector(or more) per cylinder.

[steveo]

im with ya robert, if i ever see a cheap tpi setup ill be all over it. im actually a big lb9 fan too, i've had several. but i've never actually played with a tbi unit, so i kinda want to do it for the experience.

i havent even had a chance to dig back in my memory and remember what mask it's running, and i'll have to hit moates for some kit.

i think one problem with this car is that the stock lo3 tbi & computer was plunked on SOME sort of '305 ho' crate longblock, which i figure has a different VE

i have no bloody idea, but i can tell without it even being on a scanner, it's trimming a hell of a lot (the transition into closed loop is very obvious, and once it catches up, part throttle goes from odd to PERFECT)

it's catless right now, but the engine bay is cluttered with AIR junk, i think removing that will be my first order of business so i can actually work on the thing. then i'll hack myself up an open air cleaner.

[Fast355]

im with ya robert, if i ever see a cheap tpi setup ill be all over it. im actually a big lb9 fan too, i've had several. but i've never actually played with a tbi unit, so i kinda want to do it for the experience.

i havent even had a chance to dig back in my memory and remember what mask it's running, and i'll have to hit moates for some kit.

i think one problem with this car is that the stock lo3 tbi & computer was plunked on SOME sort of '305 ho' crate longblock, which i figure has a different VE

i have no bloody idea, but i can tell without it even being on a scanner, it's trimming a hell of a lot (the transition into closed loop is very obvious, and once it catches up, part throttle goes from odd to PERFECT)

it's catless right now, but the engine bay is cluttered with AIR junk, i think removing that will be my first order of business so i can actually work on the thing. then i'll hack myself up an open air cleaner.

First thing those cars need is headers and full exhaust, followed by a decent fuel pump and afpr. Then followed up with a great tune. I had a LT4 cammed TBI 305 put down 181 rwhp/282 tq on a Mustang dyno through a fullsize G-Van drivetrain. On a dynojet it would have been ~200 hp, in a car I could have thrown more timing and a leaner afr at it and combined with that and the removal of a engine driven fan and the extra u-joint, 9.5" corporate 14 bolt, and carrier bearing would have put down 220+ all day long.

[steveo]

really? even just full exhaust requires a fuel pump upgrade and a bump in pressure

were they really built so close to the limit?

[Fast355]

really? even just full exhaust requires a fuel pump upgrade and a bump in pressure

were they really built so close to the limit?

Yes they were! Most stock TBI engines are out of fuel at 3,600 rpm.

[steveo]

i don't get it, how would an engine with a 6k redline make it out of the factory if they leaned out at 3600 rpm?

[Fast355]

i don't get it, how would an engine with a 6k redline make it out of the factory if they leaned out at 3600 rpm?

Factory fuel shut off on most TBI engines is 4,800. I think the redband on my brothers factory 91 bird was 4,500.

That being said the math is fairly simple. The TBI F-car regulators only put out 9-10 psi most of the time. Injectors are rated 55 lb/hr @ 11 psi. At 10 psi they only flow 52 lb/r. Good for 185 hp at .45 bsfc and 80% dc. The L03 is net rated 170 hp, fuel requirements should be off a gross hp number. Most stock calibrations hit 100% dc by 4,500 rpm.

We had a worn out old L03 in that 91, nothing done but a magnaflow high flow cat and single 3" exhaust and an open element. At 3,500 the injectors went static and at 4,000 the o2 voltage would drop into the double digits range....17 mv...etc

[steveo]

i see my error, my head is still in multiport territory. i guess 8 cylinders with ~50lb/hr injection is pretty pathetic.

so the stock pump takes a shit on flow if you get an adjustable regulator and bump it up a couple pounds, and retune?

my plans for modifying this junker are exhaust and an open element air filter, that's about it for the next while (except i really have to paint it...)

[steveo]

... or would the stock pump be ok if i threw bigger injectors in there?

[tamperedchevy]

a stock tbi pump is only good for around 14 psi, but not sure how it would hold up with bigger injectors if you kept the pressure down. should work i would think.

I went with a gta trans am tpi pump from Oreillyauto $80. it holds my 18-19 psi flawlessly.(figured if it could power 8 injectors at 42lbs or whatever that it could hold up to two injectors @18 psi)