TBI performance

[Batman]

Hi guys, well I am back to plan #1 sort of for the WTM. Back to a TBI engine (since I got a free engine to use for my build) so Myself and the owner of Visions of Speed (who has a TBI truck) are going to see how far you can push a stock cubed TBI engine. We've been putting in alot of book time and I have been corresponding with Turbo City (One of the leaders in TBI performance) and we think we may be able to surprise you with some results.
Here is the new goal:
Build a 12.xx second street car using a stock block and factory heads (they will be ported) and keep the price reasonable.

The block is going to be .030 over but otherwise it will be stock except for valve reliefs in the pistons and obviously a cam change.

What do you guys think? can it be done? I am VERY optimistic, especially with the Formula only weighing in at 3200 pound curb weight.
Also if anyone is interested I can start writing up how to install this stuff, what it costs and what gains/losses it makes since I have all the free dyno time I want it should be easy. Don't know how many of you besides myself but there is probably alot of tricks that are similar to Carb's. So let me know and I can start writing it out

[Tru2Chevy]

Should be pretty easy, IMO.

Tim (NJSPEEDER) went a 14.0 on a stock cam LO3 (had aluminum heads though).

With a nice cam, free mods, good intake, custom tuning, and well-preped car - I would be surprised if you didn't get into the 12's. Have fun shutting up all the 305 TBI haters :D

- Justin

[foff667]

Should be pretty easy, IMO.

Tim (NJSPEEDER) went a 14.0 on a stock cam LO3 (had aluminum heads though).

With a nice cam, free mods, good intake, custom tuning, and well-preped car - I would be surprised if you didn't get into the 12's. Â* Have fun shutting up all the 305 TBI haters Â*:D

- Justin

:stupid: it would be nice to see someone take it all the way for once :)

[Untamed]

I have an LO3 with TBI but don't plan to mod anything yet - just get it running.

What might help, but be more tedious for you, is an explanation of your mods that are "dummied down" for us newbies who have never even removed the throttle body. ie. Step by step explanation of what you did, removed, changed, and what else it affects. It's more work for you, but would be GREATLY appreciated by me, and maybe others, who need to work on a TBI.

If it's too much, I certainly understand.

Thanks for the offer. :)

[Fasterthanyou]

http://www.thirdgen.org/techbb2/showthread.php?s=&threadid=290728
12's with TBI and a "normal" carb engine :) . Told you it wasn't the TBI nore air flow that was the problem... it's all about having only 2 injectors and fuel starvation. From just seeing these small GN motors idle at less than 1000rpm with 60lb injectors I've come to the conclusion that you should always overshoot on injector size!

[Batman]

I have an LO3 with TBI but don't plan to mod anything yet - just get it running.

What might help, but be more tedious for you, is an explanation of your mods that are "dummied down" for us newbies who have never even removed the throttle body. Â*ie. Step by step explanation of what you did, removed, changed, and what else it affects. Â*It's more work for you, but would be GREATLY appreciated by me, and maybe others, who need to work on a TBI.

If it's too much, I certainly understand.

Thanks for the offer. Â* :)

I can do that for you guys, I'll even add pictures for you all if you want, although I have nowhere to host them but could E-mail them to anyone interested.

[Batman]

http://www.thirdgen.org/techbb2/showthread.php?s=&threadid=290728
12's with TBI and a "normal" carb engine :) . Told you it wasn't the TBI nore air flow that was the problem... it's all about having only 2 injectors and fuel starvation. From just seeing these small GN motors idle at less than 1000rpm with 60lb injectors I've come to the conclusion that you should always overshoot on injector size!

Still in the planning stage but I will probably go with 61# or maybe even 68# injectors and a higher pressure fuel pump with regulator setup. I agree, that will be the limitng factor, but I think it will still be doable. To hit 12's I am looking at about 320RWH, so I don't think it should be that bad.

[Fasterthanyou]

http://www.thirdgen.org/techbb2/showthread.php?s=&threadid=290728
12's with TBI and a "normal" carb engine :) . Told you it wasn't the TBI nore air flow that was the problem... it's all about having only 2 injectors and fuel starvation. From just seeing these small GN motors idle at less than 1000rpm with 60lb injectors I've come to the conclusion that you should always overshoot on injector size!

Still in the planning stage but I will probably go with 61# or maybe even 68# injectors and a higher pressure fuel pump with regulator setup. I agree, that will be the limitng factor, but I think it will still be doable. To hit 12's I am looking at about 320RWH, so I don't think it should be that bad.
An easy way to look at TBI injector size is to do some simple math and use the port injection guy's flow rate calculators. Example; let's say you want 350fwhp, with port injection and 90% dc you'd want at least 22# if you've got good heads, 24# if you don't. So now multiply that by 8 injectors and you've got 192 now divide by 2 and you're left with 96# injectors needed with the TBI. Hence my reasoning for running 65# injectors rated at 12psi running at 28psi gives me 99# injector flow rates.

[Batman]

yeah I figured the regulator/fuel pump would be key....which regulator you running?

[Fasterthanyou]

yeah I figured the regulator/fuel pump would be key....which regulator you running?
I've got a holley 670 (same as the 454 TBI) but it has it's own designed fuel pod and regulator. The regulator isn't upside down which makes adjusting the pressure EASY but I'm limited to smaller injectors. I had to install a beefy spring to get my fuel pressure up to 28 because the spring that came with the assembly was bottoming out at 18psi (bottoming out because it would go from 18 to 40 with less than a 1/16th of a turn).
The TBI fuel pumps are low pressure pumps which really sucks. My old pump couldn't even wet the return line when I had the fuel pressure at 16psi. That was a POS pump and the walbro made all the difference.

[NJSPEEDER]

ahh, the 12's from tbi topic again.
easy.
step 1: posi and 4.10 gears. you have overdrive, teh car will love them, and they won't ruin your mileage.
step 2: a nothing crazy cam. think about a comp cams extreme energy or a stock LT4 or LT4 hot cam.
step 3: intake, i suggest the holley over teh edelbrock. it comes already bored for the 454/holley tb and it has a little more volume to support more top end power.
step 4: exhaust. "iroc" shorty style pipes will do nicely. look for 1 3/4 primaries and 3inch collectors. also make sure a good y-pipe is included. teh good pipes tend to be a little pricey, think about SLP or Edelbrock. both have very good fit and finish.
go for a 3inch mandrel bent cat back. don't worry about brand, find one that you think sounds nice. they all flow similarly and no one brand is worth a major power gain over another. cat delete pipe is very very strongly suggested as well.
step 5: tuning is actually something that you will want to handle every step of the way. real custom tuning, no off the shelf or mail away junk, is the only way to get teh full potential of any combo. talk to fasterthanyou about that.

for the stock heads, don't bother going too nuts on them. clean up the casting, do a simple gasket match and a 3/5 angle valve job will be plenty.

since you goal is ET based you shoudl look into traction aids. some stuff liek relocating teh battery to the spare tire well is cheap. other things like after market torque arms are a bit more pricey. et is about traction and gearing, not who has the most hp.
a small set of drag radials woudl be nice too. 235 or 255 section tire is all you will need if you take care of your chassis properly.
if you have an auto look around for something in a 2600-3000 stall TC for it. stick car, get a short shifter and a dual friction clutch.

later
tim

[Batman]

The suspension is already done and I have a good plan of action very similar to the one you described but budget is a consideration. I know I could throw $8,000 at it and make it go 12's, I want to try and sneak in a relatively cheap setup that is easy enough for Joe-Schmo to do and still use alot of stock parts and stay away from trick things like $400 throttlebodies. I'm gonna give it my best shot and we'll see where it falls in. If I go 13.2 so be it. I'm gonna also leave in the stock weight for the whole thing (roughly 3450 race weight I would guess). I went over my rough draft with my engine builder and he said it shouldn't be to hard to get 12's, even with a stock T/B with what I got. He only runs 305's in his race cars and he has gone as fast as 10.2 on a 4 BBl. I appreciate the input though, any other suggestions will be greatly appreciated also, depending on how the money goes I may even go with the Holley stuff. We'll see :wink: