Performance TBI 3.4

[Blue89rs]

I know it sounds like a dumb idea, but wouldn't the iron head RWD 3.4's with the crappy intake design flow far better with a TBI setup?

I've been trying to figure out how to make my camaro's intake flow better so I can pull at 6000RPM, and it seems like running the 4.3L throttle body with a stock'ish intake would outflow a MPFI intake system. I did a quick search to see what has been done, but I didn't see anything. It has been my assumption that the restriction in the gen I MPFI 60v6 is the intake runners are too long and too small. Not to mention the plenum and the tb is too small. So wouldn't going with a short runner TBI intake with 4.3L throttle body flow better, resulting in higher HP numbers? I know that the low end torque would suffer some, but all for the sake of HP. Why wouldn't you want to do this?

Feel free to smack me around if I'm just being dumb.

[FieroRush]

3 terms that dont go together. hell, they don't even go by themselves.

"Performance TBI 3.4"

[Canyonero]

This article is talking about the stock 2.8L, but this guy actually has a 3.4L with the 4.3L TBI installed... along with the bored intake, and all the other mods he describes.

http://www.4x4wire.com/tech/60degreeV6/

I'm doing a 3.4L conversion in my Trooper too, but I'm keeping the MPFI for my own reasons. I'm partly hoping for same or better fuel economy yet greatly increased power (can't be too hard on either count).

[Ed_Mc.]

My old 2.8 Trooper with a Holley Big-Bore, bored-to-match stock intake, modified air cleaner, 2" free-flowing exhaust, and Comp Cams Magnum 1.6:1 roller-tipped rockers would bang 6 Grand in 1st and 2nd and hit the hiway onramp in 3rd just screaming, easily up to 75mph. All this with 4:56 rear end gears and almost 4000 lbs.

I thought it was pretty Bad A$$ until I put the 3.4 in my other Troop. Lots of torque but it doesn't rev up as well. I need to get the <horribly> restrictive stock 1-7/8" exhaust outta there, plans to tie a 2.5" system into an upgraded 'wye' are in the works. I expect that should make it breathe a bit better!

This 3.4 with the same Holley Big-Bore and also bored-to-match intake doesn't seem to lack for air, I'd bet that if you did a bit of port-matching between the cast-iron heads and the TBI intake you'd reap even more gains.

The TBI setup is plenty tractable and it's easy to tune and troubleshoot.

The nice thing for the Trooper Dudes is that you can retain all the stock emissions equipment for those areas which must deal with Smog Nazi's.

And there's been some very impressive HP figures developed from basic bolt-on mods to a TBI'd 3.4. 187 RWHP out of a 3.4 S-10 is not too shabby!

P.S. I'd imagine that the Camaro 3.4 SFI intake is much improved in breathing over the RS's MPFI unit.

[Canyonero]

Off topic, but I'm shady on the differences between MPFI and SFI. I thought they were the same, or that one implied the other. I have been saying MPFI, but my Firebird has "3.4 SFI" cast on the intake so I may have been misleading.

[Blue89rs]

Sequencial Fuel Injection, Multi-Port Fuel Injection.
MPFI is bank fired (3 at a time)
SFI is independent.
Really aren't any gains by going to SFI (5hp maybe?). Manifolds are damn near the same.


Back to my post....

The "3.25" is in my camaro and I'm tired of it falling on its face after 4500 RPM. It has a .430" 206 duration cam, balanced crank, .060" overbore, 3 angle valve job, LS1 springs, and the heads have been completely unshrowded, gasket matched, and opened up. All of my efforts are to focused on breathing. This is why I think that the open short runner design of the TBI system is the way to go. The stock 2.8MPFI stuff is just not working out for me. The car is my Autocross car so I need some HP desperately! I think that the MPFI motor would be better suited for the S10, where low end grunt is needed.

Thanks for your positive feedback Ed_Mc.! That is exactly what I wanted to hear! I also have a 2.8 S10 and I've noticed that the power band (if you want to call it that) never falls and the engine pretty much has power everywhere. To hear that someone will wind it up to 6000 is great!

And if it didn't get any better, I have an Edelbrock Performer intake sitting at home waiting for a good motor! I think that this intake may be the kicker. The runners are all the same length.

http://www.edelbrock.com/automotive_new/mc/manifolds/chevy_v6_perf.shtml

If the 4.3L TBI proves to be too small, is it possible to go to the 5.0L TBI?

PS. I grew up in Poulsbo! Class of '97! Woot woot!

[Fiero Brick]

If you didn't have the Edlebrock Performer, I would probably have brought up the Trueleo intake designed for iron head 60*v6s. Oh, wait, I did anyway. :P

Anyone that wants to stay FI and needs more air flow over 4500 RPM or so should definitely look into the Trueleo. It's designed for F-bodies and Fieros, I'm not sure if it can be squeezed into other iron head cars.

[Blue89rs]

The truelo might be better than stock, but i want more than that. Has anyone run flow numbers on that intake? I'm not hatin', but the runners are still really long, and the plenum looks like it needs to be bigger than what it is.

Has anyone tried to use the SFI 4.3L TB? That thing is HUGE!

[Fiero Brick]

Francis has recently been producing a short-runner version that loses an inch or two of runner length over his previous design, you might want to take a look at Trueleo.com and see if it piques your interest.

There hasn't been indipendant testing, but Francis (Trueleo seller guy, his son makes them, I believe) tested both the long and short runner intakes against the fiero's 2.8 MPFI intake and no intake (bare heads) on a flowbench, from .100" lift to .500" lift. The newest, short-runner version had at its "worst," less than a 3 cfm disparity between itself and the bare heads, and that was only at .200" lift. Below that, it flowed about 2 cfm worse than bare heads, and above that it flowed just as well as the bare heads he tested. The long-runner intake was still way better than the stock MPFI intake. The MPFI intake flowed at least 7 cfm worse than his short-runner design at all lifts. Oh, and if you don't know, he'll make 'em to fit any throttle body you want to stick on there, too. Just costs a bit extra and he needs the throttle body and gasket to make the flange from.

It might start to become more of a restriction again if the heads were hogged out and given a good valve job, though. I have to agree that the plenum volume might be smaller than ideal. I kinda wish I'd taken a better look at the one I saw in person at Ed Parks' get-together this spring. I did spend a long time gawking at the dual throttle body, dual plenum set-up someone there fabricated, though. Very impressive look, and I'll bet it performed pretty dang well, too.

He's selling headers for the Fiero, now, too, but I'm kinda saddened by the looks of the prototype. My eyes are immediately drawn to the lack of real collectors. Maybe the production versions will have them. I'm keeping my fingers crossed.

Anyway, good luck with your pursuit of mo' powah.

[Blue89rs]

$600 for 14hp? I guess thats pretty good. The torque still falls off at 4000 tho. I'm going to find a dyno result for a TBI motor, but is there any way to level that torque curve out? What is the MAJOR restriction? I came up with roughly 400cfm for a 3.4L at 7000RPM, so 70cfm per runner. Sure doesn't seem like a lot, so is it still the "tuned" intake that's the problem? I'll keep pushing the TBI intake until I see a dyno sheet for one.

[Fiero Brick]

Remember, that's 14 horsepower on an otherwise unmodified 3.4 in a Fiero. Stock cam, stock valvetrain, stock manifolds. That drop off is probably due to the limitations of the cam... which while made for making -some- power at least until 5k in a 2.8, in a larger displacement engine it becomes more of a stump-puller. Cam it, get the valvetrain dialed in for making power at higher RPM, have some headwork done, get rid of the tube manifolds and bolt on some headers (not perfect specimens unless you're making your own... stupid Fiero space conciderations) and you can put out 200+ hp. On a car with that much work done elsewhere to support the intake, I'm pretty sure you could see gains in the realm of 30-40 wheel horsepower from getting rid of the craptastic MPFI stuff.

Maybe now would be an appropriate moment to say that Orief, a guy on the Fiero forums who has built both a 3.4 with an Edlebrock Performer and Trueleo intake (not sure which version) to over 200 horsepower (I want to say ~210... don't recall perfectly, though) with almost identical modifications. Hm... or maybe one was his friend's? Either way, two wild 3.4s got virtually the same performance from the Trueleo and Edlebrock Performer. That should say something.

Anyway, done plugging the Trueleo. Oreif later put a small block crate engine in the back of his fiero and ran low 12's or something like that. Traitor.

I'm not sure I've ever even seen pictures of the TBI intake for a 60*. Oh well.

You could always make a dual tb intake. Did I mention how wicked those look? Sorry, sorry...