TBIThrottle Body Injection discussion and questions. L03/CFI tech and other performance enhancements.
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I see a bigger TBI bore than 2", what is that? Also I see the Holley TBI adaptor, did you have to hog it out to get the larger TBI to fit?
Why the external FPR and what fuel pressure/injectors are you running?
Those are nifty wiring covers, lol.
A friend of mine has a 454ss with edelbrock TBI intake, increased fuel pressure, headers, and sticky tires. He's in the 13's now that I tuned him a new chip. We're looking for 13.7's with some more tuning (it's too rich low and mid, tad lean above 4000rpm). We also haven't optimized the timing tables at ALL. I don't think we'll find an amazing amount of power but I think there's enough to gain 3 more mph and get it to go over 100mph in the 1/4. I love working with these BBC TBI's, it's the 2nd one I've gotten to play with. If I didn't have to worry about gas milage I'd be all over that motor, dual TBI, cam, heads, turbo, hehe.
That's a lot of fuel pressure. I bet you could get away with only 30psi WOT. I dont' know where your redline is but in general the bbc doesn't rev as high and this is good for the injectors. More avail time to flow fuel . We're only running 18psi right now and he's trapping at almost 98mph . We'll be turning the pressure up to 24 and leaving it there, believe this or not but he's still got the stock cam in it. I'm rather impressed with our results so far but if we do a cam swap I'd want it in the 12's with a stock 2" TBI .
What I didn't list he hasn't touched. It's a 90' and everything (heads and cam also) are stock. Trans is stock, interior, no frills just exhaust work and an intake manifold . Is stock compression really only 7.8? I would have thought 8.5 at the least, 7.8 is like late 70's compression.
Originally posted by JPrevost What I didn't list he hasn't touched. It's a 90' and everything (heads and cam also) are stock. Trans is stock, interior, no frills just exhaust work and an intake manifold . Is stock compression really only 7.8? I would have thought 8.5 at the least, 7.8 is like late 70's compression.
I take it back, just remembered how hard it shifted... it has a shift kit.
Are you still using the 8747 or have you moved to the 7747, I forget if you told me already, lol. Don't take offence, I get a LOT of people asking me questions that I loose track with anything older than a week.
He's looking to get a cover for the back. Right now gas milage is like BLAH, he doesn't even want to tell me, haha.
Originally posted by JPrevost I take it back, just remembered how hard it shifted... it has a shift kit.
Are you still using the 8747 or have you moved to the 7747, I forget if you told me already, lol. Don't take offence, I get a LOT of people asking me questions that I loose track with anything older than a week.
He's looking to get a cover for the back. Right now gas milage is like BLAH, he doesn't even want to tell me, haha.
Originally posted by heavychevy454ss :nono: I haven't made it to the track yet, but I've turned mine to 6000+. It felt like it pulls strong to abour 5500.
If I can ever get my tranny fixed I'll let you know.
The buttometer isn't accurate. Mine was faster shifting at 4700 instead of 5000 or above at the track.
Sure, I could wind it tighter, but it made it slower
The buttometer isn't accurate? damnit.. that's disappointing, <grin>...
Seriously, hey to the 454ss guys. I came over here to learn about hacking the crap outta the fi on my truck.
Originally posted by JPrevost That's a lot of fuel pressure. I bet you could get away with only 30psi WOT. I dont' know where your redline is but in general the bbc doesn't rev as high and this is good for the injectors. More avail time to flow fuel . We're only running 18psi right now and he's trapping at almost 98mph . We'll be turning the pressure up to 24 and leaving it there, believe this or not but he's still got the stock cam in it. I'm rather impressed with our results so far but if we do a cam swap I'd want it in the 12's with a stock 2" TBI .
Jon,
I ran the 1/4 at 13.65@101.9 using 10.5psi on my 80# injectors.
I ran the 1/4 at 13.65@101.9 using 10.5psi on my 80# injectors.
If my calculations are correct that's a sure sign of fuel starvation. The fuel you had to make power was limited and you can only extract so much power out of so much fuel... definatly needed more fuel pressure if that's the best trap speed for your setup. I'd like to hear what she runs with the new fuel pressure setting. It's amazing how hard it is to tune TBI well. No wonder so many people go port injection.
Originally posted by JPrevost If my calculations are correct that's a sure sign of fuel starvation. The fuel you had to make power was limited and you can only extract so much power out of so much fuel... definatly needed more fuel pressure if that's the best trap speed for your setup. I'd like to hear what she runs with the new fuel pressure setting. It's amazing how hard it is to tune TBI well. No wonder so many people go port injection.
Jon,
Np question of that. You could see the AFR climb to 14:1 on dyno runs I did. Fortunately, no loud BOOOMMM! That ET and Trap were with my old cam too. I just tuned my motor for 19psi and it really seems pretty happy there. With the WB O2, AFR is pretty steady at 12.4-12.6 from 3200rpm up to about 5400rpm.
Np question of that. You could see the AFR climb to 14:1 on dyno runs I did. Fortunately, no loud BOOOMMM! That ET and Trap were with my old cam too. I just tuned my motor for 19psi and it really seems pretty happy there. With the WB O2, AFR is pretty steady at 12.4-12.6 from 3200rpm up to about 5400rpm.
I want to see some dyno numbers now that the fueling is fixed. Was there a noticable difference in the exhaust tone?
Originally posted by JPrevost I want to see some dyno numbers now that the fueling is fixed. Was there a noticable difference in the exhaust tone?
I'd like to do that in the next few months, possibly in preparation for an early spring visit to the drag strip. That 13.65 was with the 4+3 trans, street tires at 35psi, and a D36 3.07 rear.
As for the exhaust note, at part throttle cruise the motor is quiet with a very steady drumming of the exhaust seeming to come from several feet behind the car. I took it out last night and I couldn't perceive any difference in the engine note from 3000rpm up to 5600rpm. Frequency obviously changed but not the pitch or amplitude. The buildup of revs sounded very consistent throughout. The acceleration didn't seem to change very much or peak out. I remember thinking how damn good the motor sounded both going up the gears and at full rev. It has a bit of a "raspiness" to it that it didn't seem to have before. Sort of a rrrrraaaaaaaaapppppp.
Last edited by Dominic Sorresso; 12-22-2004 at 09:28 PM.
That two stud air cleaner assembly... will that work on my Rochester TBI or is that strictly a truck thing. My air cleaner stud running through my K&N is getting stripped. GM doesn't distribute these anymore and junk yard runs are fewer and farther between these days.
Originally posted by Cadillac That two stud air cleaner assembly... will that work on my Rochester TBI or is that strictly a truck thing. My air cleaner stud running through my K&N is getting stripped. GM doesn't distribute these anymore and junk yard runs are fewer and farther between these days.
Curious,
C
I think you can use the dual stud set-up on our cars if you want. If you look closely, you'll notice that the studs just attach to the two rear-ward bolts that attach the TBI unit to the intake manifold. I haven't seen it done on our cars, yet, though.
Have you tried running a die on the air cleaner stud, just to see if that will help?
Originally posted by Cadillac That two stud air cleaner assembly... will that work on my Rochester TBI or is that strictly a truck thing. My air cleaner stud running through my K&N is getting stripped. GM doesn't distribute these anymore and junk yard runs are fewer and farther between these days.
Curious,
C
The trucks used both the single and dual studs. Mine originally had the single stud, but I converted it to get the stud out of the airstream.
Also, I needed to convert it over to the 2 studs to mount the Vortech hat that will eventually be installed.
__________________ 90 454SS; TBI 496. Best to date: 12.42 @107, 1.63 60 ft.