.....do they do much? I have heard pluses and minuses on this topic but nothing clear one way or the other. If you swap the TB for a larger one (i.e. 58mm) and dont do much else at the moment to the engine, is there any benefit to doing that? What would the future benefits and necessary upgrades be?

Using a big bore throttle body without porting the plenum will probably do little to improve horsepower.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
87GT - 3.4L Turbocharged engine, modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

The TBI by it self will add little to performance ,, the main reason is the exhaust manifolds are choking the engine,,untill the exhaust is opened by porting the stock manifold or replacement with headers..
A big bore throttle body is available from the fiero store at a reasonable price ..
You only have to look inside the stock exhaust manifold to see the problem !1/3 of the port is blocked..
Exhaust modification is the single most important modification you can do to a Fiero V 6 those who disagree with this have forgotten what a stranglehold this manifold has on the V6..
I have read reports on this forum that porting made no difference in performance ,,to me this is unbeleavable just removing the tubing that protrudes into the port like a DAMN..will cause cooler running,, better performance,,better gas milage ,increased efficiency..
Unfortunately this is not as easy a task as it looks removal in the pipes may result in broken bolts that are a 8/10 in difficulty of removal,,and the porting is very labor intensive
the more open exhaust makes the TBI and intake manifold porting worth it

Interesting. So I am putting the Sprint manifolds on in a couple days, if I were to slap a big bore TB on there, it should make a marked difference. Then have someone port the plenum or no?

As bad as they are, the headers are not the main problem nor is the TB size, it's the intake manifold, it just wont flow much air above 4.5K. The stock TB is fine and works good with a better intake. You need to go with a carb setup or one of our intakes.

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[IMG]



Trueleo.com/fiero.htm
RSpiderII@aol.com

So just to be clear on a couple of things: manifolds = headers, not the plenum. "porting the heads" we are talking about the cylinder heads, not the headers, right?

Okay so a good method would be:

New headers (going with the Sprints on my project) ----> Big bore TBI ---> Ported plenum ---->Upgraded exhaust (i miss having the option of buying the SS Borla exhaust...btw i cannot remove the cat as i live in NJ and it wont pass inspection) --->and port the Y pipe

quote Originally posted by Francis T: As bad as they are, the headers are not the main problem nor is the TB size, it's the intake manifold, it just wont flow much air above 4.5K. The stock TB is fine and works good with a better intake. You need to go with a carb setup or one of our intakes.

I will partially agree with you. The stock Fiero plenum doesn't flow all that well-agreed! However, if you look down into the piping from the port area in the stock Fiero exhaust manifolds you will see slots instad of a circular opening to the port size. This area is restrictive as was cofirmed by the Herb Adams dyno tests years back. It was found that by porting the exhaust manifolds they picked up something like 5 HP.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
87GT - 3.4L Turbocharged engine, modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

quote Originally posted by Dennis LaGrua: I will partially agree with you. The stock Fiero plenum doesn't flow all that well-agreed! However, if you look down into the piping from the port area in the stock Fiero exhaust manifolds you will see slots instad of a circular opening to the port size. This area is restrictive as was cofirmed by the Herb Adams dyno tests years back. It was found that by porting the exhaust manifolds they picked up something like 5 HP.

Closer to 8, I think. Biggest and stupidest GM screw up on the breathing on these engines.

What most people don't mention is that the exhaust intermediate pipe als has restrictions and needs redoing.

quote Originally posted by BillS: Closer to 8, I think. Biggest and stupidest GM screw up on the breathing on these engines. What most people don't mention is that the exhaust intermediate pipe als has restrictions and needs redoing.

Indeed, thats why we use 2" and 2.5" on our Y pipes. Too bad GM made these intakes and headers to fit near any car they may build. The real bummer is; the intake to an untrained eye looks like a nice design, thus people spend money on other things like cams seeking more power only to have the intake negate most of what they thought they would get. Sans, the 4.5 K wall.

Francis, does the Intake manifold come with a slight over bore? I left a message with Troy that I want to order the combo package with the 2 1/2 inch headers. I am building a 3.1 with 20 over, cam, modified heads with intake and exhaust ported. I am unsure on the throttle body or what size TB to use.

While we had our TB flanges made to fit a stock TB, I ship the intakes with 60mm TB bore so you go bigger.

quote Originally posted by BillS: Closer to 8, I think. Biggest and stupidest GM screw up on the breathing on these engines. What most people don't mention is that the exhaust intermediate pipe als has restrictions and needs redoing.

Bill I agree and that crossover pipe really necks down to a tiny area. If you've ever cut one apart you'll see about a 1" area near the Y. Very restrictive. I do think that with ported exhaust manifolds and a new crossover pipe most of the breathing problems would be solved. Of course Francis headers seem better so it depends on what one wishes to spend.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
87GT - 3.4L Turbocharged engine, modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

quote Originally posted by Francis T: Does the 3.1 with allmunium heads use the smae stock intake manifold as an iron head 3.4 - 2.8?

Nope, completely different intake port spacing. I can probably snap a few pics if you're interested in seeing the difference

Cheers

quote Originally posted by TiredGXP: Nope, completely different intake port spacing. I can probably snap a few pics if you're interested in seeing the difference Cheers

Please do put the photos up or email em to me. I have a customer that wants to order our intake for use with the aluminium heads. I dont want to send him something that wont work!

The trueleo set up,, intake manifold and headers are the top horsepower gainers for the 2,8 V6 and the stock intake is very restrictive ,but the easiest,bestest(tech term) mod for the V6 is to open up the exhaust !! porting the stock exhaust manifold can not compare with the trueleo header,, Trueleo proven by dyno and fiero owners..The sprint headers are about the same as a good ported stock manifold ,, the sprints are better with a modified engine or one that has the modifications to let the rpm,s climb above 5000rpm..
The stock intake is very difficult to modify and alternatives are expensive and destroy the engine appearence of the V 6 which is neato jet in stock form....
Porting the stock manifold can be done for under $100.oo including tools & welding and is the best option for the average owner,,taking into concideration you might do this when you have one of the Fiero,s tick,leaks ect.from the ex.manifold
Francis T. I salute you for the time and effort you put into the developement of a superior product for fiero owners you are aces with me and many others ,a fiero baron of the realm & I hope gold and vast sums of money decend upon you,,But it is my windbag overinflated OPINION that the best mod to make to a V6 is to port the stock manifold..
If money falls from the sky and does not injure me seriously ..I will own a set of trueleo headers ..

[This message has been edited by uhlanstan (edited 01-20-2009).]

Francis T - here you go - these pics are from a GEN II 3.1 out of a 1990 Chev Lumina. The last owner didn't appear to believe in changing oil !

Top side of the lower intake manifold (there's only an upper and a lower on the Gen II engine. Notice the assymetrical layout. I believe that the fuel injectors are also mounted further outboard than on the 2.8. The Trueleo intake isn't going to fit this lower.)


Bottom side of the lower intake


Just for the heck of it, here's the intake ports on the head:


hmm, looks like someone reset dates on the camera

Cheers

year 2025!!! where have i been all theses years!!! YIKES!!!

quote Originally posted by TiredGXP: Francis T - here you go - these pics are from a GEN II 3.1 out of a 1990 Chev Lumina. The last owner didn't appear to believe in changing oil ! Top side of the lower intake manifold (there's only an upper and a lower on the Gen II engine. Notice the assymetrical layout. I believe that the fuel injectors are also mounted further outboard than on the 2.8. The Trueleo intake isn't going to fit this lower.) Bottom side of the lower intake Just for the heck of it, here's the intake ports on the head: hmm, looks like someone reset dates on the camera Cheers

Thanks a lot for the photos. No way you can use our intake with those heads. The guy is putting the 3.1 heads on a 2.8 hemay be better off just sticking with the 2.8 heads and 5 angle valvue job etc and use our headers and intake. The stock heads with our intake flowed enough CFM on the flow-bench to support well over 300HP anyway.

just thinking of what is considered "big bore" for a 2.8 makes me giggle.

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First LX9 Fiero GT, 1987
If you can't fix it with a hammer, you've got an electrical problem
Fiero's are people too. We pay just as much attention to them, if not more than our loved ones
My Fiero Fuel Economy
Videos of My GT
Google Videos of My GT

[This message has been edited by americasfuture2k (edited 01-21-2009).]

Hey guys these works are all really impressive and dont get me wrong, very cool! But we're not working a Mopar 383 like I had in my brusier 67 Plymouth, or a Chevy 350 or Ford 351C, all of which I have had. This is a Fiero, and yeah it gets mistaken for a Lotus, or an M2, and sure I can fool some girls into thinking its a junior Ferarri, and I have gotten passed by a minivan before. But that's kind of the point: i like the fact that it is not a 67 Plymouth or a Mustang or Vette. I like that it is what it is, and dont really want my Formula to be a F1 car. I like how the stock engine looks. Having said that, I do want to fix an obviously flawed design with the restrictive air flow. Dont get me wrong, I am very impressed with the North* swaps, the 3.1s, the turbo kits, and so on. But I do have a kid who's college fund needs...well...funding. So for me, slapping on the Sprint headers, boring out the plenum and Y pipe, and upgrading the exhaust to Ocelot or Borla SS, is probably about as far as I'm going to go in that area. I like the fact that a "big bore" on a 2.8L is nothing compared to a big bore on a 351C. Listen, you can modify a VW Bug all you want, it'll still never be an M5 and shouldn't try to be or be compared to one.
By the way, my Fiero is now in the shop to have the Sprint headers put on, as well as all new suspension, front end, rotors brakes, hoses, etc and I should have it back Friday. After having it for 2 months I'll actually get to drive it =)

quote Originally posted by sleebbie: ...I do have a kid who's college fund needs...well...funding. So for me, slapping on the Sprint headers, boring out the plenum and Y pipe, and upgrading the exhaust to Ocelot or Borla SS, is probably about as far as I'm going to go.... By the way, my Fiero is now in the shop to have the Sprint headers put on....

I think you'll like the Sprints. Unlike the stock exhaust manifolds, they seem to last forever, and are ceramic-coated, providing under-the-decklid heat reduction, not a bad thing within the Fiero's hot engine compartment.

As for your child's college fund which, as you say, "needs funding," I unfortunately can't help you there.

However, some classic "Before" versus "After" pictures of an otherwise stock, but cut-up Fiero Y-pipe provided us elsewhere by fellow PFF member, Dodgerunner, should provide you a very good idea of the inefficiency of the Fiero V6's factory-original, exhaust Y-pipe:

quote Originally posted by Dodgerunner: Well here is the before and after pic. While there is some restriction don't know how bad it really is but took it out like others have.

Y-pipes, IMO, are just about anything except "glamorous," but I think you can see from the photos by Dodgerunner which I've posted above why you'd do well not to ignore the Y-pipes in your child's Fiero.

Good luck with your project!

Wow talk about restricted! I dont understand why GM did this (other than maybe for emissions?) but yes assuming i get the manifold bolts out (which are currently broken off) then I will open up that Y-Pipe. Like yo usaid, not a glamourous upgrade, but looks like a needed one. Thanks!

What would be a better than stock y-pipe to get? Would the truleo ypipe work with sprints? I see the fiero store sells a ypipe; is this any better than the stock pipe. thx jay

also depends on the state you live in......from my understanding here in NJ I cannot use that downpipe from TFS or eliminate the cat cos the car wont pass emissions

quote Originally posted by Francis T: Even a ported stock intake falls way short CFM-wise. It's beter than stock but not all that much. As for the look of the engine with our intake, It's kind of a love hete deal, you either love the tube intake race-like look or hate it. I like it a lot more because when I look at the stock intake I see a really bad design and not a nice looking intake. My eyes go strait to those insane tight corners between the upper and mid sections. Then again, I like the look of tube intakes and headers, reminds me of older F1 cars and lots of other awsume race cars. But thats just me.

Yeah, that's my thing. I look at your intake / plenum, and I can see clearly it is a superior design, with respect to efficiency and performance. But i'm so anal about making things look stock with this Fiero I have, that I just can't justify it.

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Todd,
2006 Pontiac Solstice
2004 Volkswagen Beetle Convt. (Wife's)
2002 Ford Crown Victoria LX
1987 Pontiac Fiero SE / V6
1981 EZ-GO Xi875-A "Miami Dolphins" Medical Cart
1973 Volkswagen Type-2 Transporter
1973 Oldsmobile Cutlass Supreme 350

quote Originally posted by achbaby: What would be a better than stock y-pipe to get? Would the truleo ypipe work with sprints? I see the fiero store sells a ypipe; is this any better than the stock pipe. thx jay

In answer to your three questions:

1. You've apparently at least two alternatives: one from http://www.trueleo.com , or one from The Fiero Store.
   
   
2. The advertised Trueleo Y-pipe does not; it's designed to fit Trueleo headers, not Sprint headers. An unadvertised Trueleo Y-pipe built in early 2007 for my `86 Fiero GT by fellow PFF member, Francis T, is designed to work with Sprint headers. The big honkin' exhaust pipes comprising that Y-pipe are a work of art, IMHO, and have no crimps in them whatsoever. However, I don't know if Francis T still has the jigs to make another set for a Fiero equipped with Sprint headers.
   
   
3. I believe so, but I'm not certain of that.

Taken from another thread, here is more information and a couple of pix on the unadvertised Trueleo Y-pipe for Sprint-header-equipped, pushrod 60^o V6 engines, be they the Fiero 2.8L, or something like my 3.4L swap:

quote Originally posted by Francis T on 03-06-2007: We may offer this Y pipe ae a replacemnt for the stock an Sprint Y pipes. It has 2"dia thoughout and if we do offer it, you can special order it with a 2.5" 3-bolt flage down leg and with/or wihtout EGR. Here's 2 pictures of the first one. Note that the left runner only looks strait where goes into the Y, it is curved nicely. There is NO D section left and right sit atop each other in a full figure 8. This one still needs to be cleaned up and pressure tested.

guess i will have to contact Francis T on that one. Is the fierostore ypipe any better than the stock ypipe?

Im with 82-T/A [At Work] I like the stock look of the 2.8L, though I have to say that a Y-Pipe boring is in my future. Yeah i have heard that the "lower end" Porsche's have a lot of restrictions on their breathing. So I'm understanding that if you keep the stock 2.8L the best ways to go are the manifolds, ported heads, big bore TB, and better exhaust. i have found that my mechanic is having to pull the heads to get the headbolts out, so I guess I might as well have him port the heads while they are off.