I'll just let the pictures speak for themselves. In the second picture, you're looking at a 57 mm TB gasket. The stock gasket is almost as bad.

(I hope to resurrect the manifold later)

Can you spell "restriction"?

I've made two of these but they are WAY too much work and I have to have someone else do the welding. I have plans for the cut manifold above that I hope will be a lot simpler, though not quite as stock looking. If it works out (counting a lot on my aluminum welding skills as I plan on doing the next one myself), I'll post the result.

Yikes!

If you are going to all that trouble, why not put the L98 or LT1 (forget which) throttle body on there that is 2 48mm openings. Since that throat is rectangular, put in an oval tube as well. Although if you build me one of those, I won't complain.

Damn nice looking weld though. Looks like a stack of dimes!

-Rick

Looks Awesome! Are you planing on dyno testing that intake??

Jason

Hope to dyno it in the next couple of weeks. I'll post the numbers then.

Sweet! Can't wait to see the results. How did you form the new bigger round intake runner??

Jaosn

quote Originally posted by ThatRickGuy: Looks like a stack of dimes! -Rick

That was cold.

No Raydar, "looks like a stack of dimes" is a compliment to any tig welder. Brewcheese, what I used to open it up is just a piece of 2" i.d. 3/16 wall tubing.

[This message has been edited by triker (edited 10-04-2005).]

The intake looks good so far, I can't wait to see dyno results.

Like Triker said, stock o' dimes = good welding. Not the MTA dimes and JB Weld crap.

If you look at the pic, it looks like someone pushed a stack of dimes over so just a bit of the face of each dime was showing. Me personally, I can't weld to save my life. My weld on that wouuld look significantly more like someone blew their nose on it. Err, I guess it's actually brazing, being alluminum and what not, but still, nice work!

-Rick

My apologies.
I've never heard the term before. I thought you were kidding triker and taking a poke at MTA at the same time.
Of course, the welds do look good. (I'd compare them to welds I've seen on show cars and stuff.)
Of course, my uneducated self couldn't weld if my life depended on it.

It's all good.

[This message has been edited by Raydar (edited 10-05-2005).]

The other problem is getting the air into the engine. On the IMSA cars they cut the bottom out and used a flat sheet of aluminum and filled in between the 'fingers'. I've thought of using two intakes and just increasing the size but keeping the look.

and people never believed me when I said just porting it wasn't worth the money - the plenum needs major reconstruction like what you've done to open up the neck

Here are some other views of the inners of the Fiero intake.

This is that thin neck area;

Here are the runner intakes;

GOOD WORK!

The neck issue is just as obscure as the Y pipe issue was. The runners look ok to a point and could easily be ported, but that neck.. ..... So fabricating a new neck and entry to the plenum is something alot of guys can get done at their local machine shop for not alot of money. You could actually use heavy walled aluminum channel and fab from there.

Way to go.

Arn

Better yet, why not just close off that inlet and mount a TB on top of the manifold in the cut out area, I bet that would flow better by eliminating the need for the air to slam on the brakes and make a sharp turn into the four ports closest to the inlet, the last two should get the best air feed because of the air velocity carrying it to the end of the manifold and the wall directing it into cylinders 1 and 2, that's why add on fuel spray at the throttle body for extra fuel needs doesn't work well, it tends to separate from the air rather than make a sharp turn,. Entering top down makes it a more even distribution flow

[This message has been edited by Joseph Upson (edited 10-05-2005).]

I did pretty much what you show on the manifold and alexformula put that manifold on the dyno. It's in the tech archives and showed very little hp gain on the dyno, certainly not enough to warrant the work.

John Stricker

John, that old thread is very educating. My thoughts are that increasing the overall volume of the upper plenum was an opportunity for more air and a larger plenum volume which aided top end but not bottom end. I think your dyno confirmed this. The idea of simply providing more air (just a bigger opening) for the stock plenum with same length runners will have a different effect.

I noticed that you were talking about needing bigger injectors to take advantage of the extra air. Either mod probably would require more fuel mixture. Did you ever test further with larger injectors? Did anybody just mod the intake of the upper plenum and dyno that? History is good to know and thanks for your info.

Joseph, you hit upon the real issue. When the carb guys increase the intake to 410 cfm they add a carb or TBI that pumps properly metered fuel mixture to take advantage of the increased cfm. (390 cfm carb) So rather than mod the existing Fiero plenum for a TBI, you just need to plop the Edelbrock on it which is already metered to accept a TBI.

Modding the stock plenum brings in complexities in metering the MPFI system to handle more air.

Arn

[This message has been edited by Arns85GT (edited 10-05-2005).]

Runner size and length are critical in getting the most out of an engine. The idea of having runners, instead of just a big air box over the head intake ports, is to create velocity into the heads. Too large of runners, or too short, means no residual velocity when the valves open to take in the next "gulp" of air. This will work "okay" at low rpms but will kill higher rpm engines. Too small of runners and you lose volume because of restriction. Too long, and you lose volume from friction. Ideally, the runners will be of a size and length to provide enough air, with as much residual velocity as possible, for the engine size and rpm range. I'm sure Francis understands this as he offers both a short runner and long runner Truelo intake. I think the Fiero intake was probably designed with the correct perimeters to work on the 2.8 v6 and then someone "squished" it down for a lower profile without considering what they had done to it's performance.

quote Originally posted by triker: Too large of runners, or too short, means no residual velocity when the valves open to take in the next "gulp" of air. This will work "okay" at low rpms but will kill higher rpm engines.

Actually, just the opposite is true. High RPM motors thrive under short, large runners.

------------------

My Web page | The Turbo Super Duty Build.
You know that little voice that says it can't be done? I duct-taped mine's mouth shut and pushed it down a flight of stairs.

quote Originally posted by FastIndyFiero: Actually, just the opposite is true. High RPM motors thrive under short, large runners.

Yup. Contrast the L98 (TPI) and LT1 intakes. L98 = long runners = great torque, but out of breath at 5500 RPMs. LT1 = short runners (a few inches) = decent torque, and doesn't have a high RPM problem (spun mine to 6500 frequently).

That's why guys go to sheet metal intakes on their high RPM race motors. You can make short short runners. At the expense of low end torque. It's pretty common knowledge that sheet metal intakes will show a ~+15 hp increase on an LS1 motor, but at the expense of about 40 ft-lbs of torque down low.

------------------
85 GT 2.8/Auto (daily driver)
2 x 86SE 2.8/Auto (parts cars)
79Z28 / 94Z28 / 98Z28 / 93 Suburban
1 wife who thinks I'm nuts...

[This message has been edited by AKM (edited 10-06-2005).]

quote Originally posted by triker: Runner size and length are critical in getting the most out of an engine. The idea of having runners, instead of just a big air box over the head intake ports, is to create velocity into the heads. Too large of runners, or too short, means no residual velocity when the valves open to take in the next "gulp" of air. This will work "okay" at low rpms but will kill higher rpm engines. Too small of runners and you lose volume because of restriction. Too long, and you lose volume from friction. Ideally, the runners will be of a size and length to provide enough air, with as much residual velocity as possible, for the engine size and rpm range. I'm sure Francis understands this as he offers both a short runner and long runner Truelo intake. I think the Fiero intake was probably designed with the correct perimeters to work on the 2.8 v6 and then someone "squished" it down for a lower profile without considering what they had done to it's performance.

compare the fieros 2 peice top end to the camaro 3.4's 1 peice top end... the fieros plenum could be opened up completely with a fatter neck and the runners removed completely leaving the runners only in the middle and lower intakes and would pretty much match the flow of the stock 3.4 intake..

Okay, maybe I got it backwards but, my point is "bigger isn't always better". There has to be a balance between the length and the size of the runners if you want a streetable machine.

This is why I'm shortening my Fiero intake height as well.

In theory, if the runners where short enough, you could have a throttle body as big as the diameter of the runner and provide enough air. Ofcourse that's with a runner length of 0", lol. Hence if you shorten the runner length enough, even the stock TB could provide enough air. I plan on shortening my stock ported intake about 1.3".

And that's much cheaper than a custom intake.

Edit:
Remember, the only reason we have one big throttle body is because that's more economical than an individual throttle body per cylinder...and the reason we have runners is to build velocity.

[This message has been edited by lou_dias (edited 10-07-2005).]

there have been some wild thing done with the stock intakes.
one of the more impressive things was to remove the upper plenum completely, slap a tube on each side, and put a throttle body on each tube.
I would love to see someone put a thottle body on each runner of the lower plenum
one dude here even really did put a 2nd throttle on the top of the plenum - tho I dont think that worked out very well....

There's a pic somewhere on this forum with a link to a company that makes a 6 velocity stack intake.

quote Originally posted by lou_dias: There's a pic somewhere on this forum with a link to a company that makes a 6 velocity stack intake.

yes, the mightly kinsler mmmmmmmmmm
and to what you were saying earlier - runners are just velocity stacks bent to meet a common tube - and is what TPI (Tuned Port Injection) is all about - tuning the runners/velocity stacks size & length to certain RPM

and fuel injected too!

Been there done that. Although yours come out better than mine did. I have been driving mine for a year now like this. Unfortunately I haven't been able to to a dyno either. I'm also interested in what it will run on the dyno. My intake also has the Darrel Morse TB on it. Mark

------------------

NIFE
silver 88GT - bone stock
blue 87GT - 3.4 roller cam, coilovers, 88 cradle swap, many other mods
www.comcast.net/~mark3340/default.htm

[This message has been edited by Dough19 (edited 10-07-2005).]

quote Originally posted by Alex4mula:

That is freakin sweet....

If anyone has driven an X-11 with the carb'd LH7 HO engine, the short runners of the intake allows that thing to wind out 6500+ but the low end isn't as strong as the Fiero MPFI intake. In fact, the 81's had a higher redline than the 82-84 (they switched to MPFI when the Fiero verison of the engine came out in 85). The X-11 engine didn't wheeze out like the Fiero at 5500-ish.

Having owned several of both the X-11 and Fiero, you can feel the difference in the torque and RPM range between the carb's short runners and the Fiero FI long runners.

One check I do when I suspect a restriction is to hook up a map to the intake and read the voltage at key on engine off and again at WOT. If they match, the intake isn't a restriction since the pressure in the manifold is the same as atmospheric pressure.

If there is a difference, then the engine is drawing a vacuum in the intake since something up stream is a restriction. Since the Fiero has a map, scan it and read the MAP at key on/engine off and again at WOT.

When you open the throttle, that is a major air leak. If the intake can supply all of the air the engine needs it should be close to atmospheric pressure.

If you log it, you will see the MAP go to max pressure and then as the RPM comes up the pressure will start to drop as the vacuum builds in the intake. On a DOHC, when we changed to a bigger filter, the dip went away.

TK

[This message has been edited by TK (edited 10-07-2005).]

quote Originally posted by Gokart Mozart: The other problem is getting the air into the engine. On the IMSA cars they cut the bottom out and used a flat sheet of aluminum and filled in between the 'fingers'. I've thought of using two intakes and just increasing the size but keeping the look.

OK, what is the source for these pictures??? That engine bay is identical to my PPG Pace Car.

Fred

quote Originally posted by Alex4mula:

Is that an Independent Throttle Body setup?!
I want one, where do I get it?

-Mulholland GT

Yes it is. The Independent throttle body intake is the best intake possible, whether it be for boost, NA, high RPM, or low RPM. You will never get a more efficient design, and its full of potential either on or off boost. Also, it allows for relocating the injectors farther away from the head, which will benefit torque and horsepower, but will make for a slightly rough idle.

Here is mine, pretty much the same thing, but mine will have much shorter runners and be verticle, and be on a DOHC. Mock up pics:

These are TWM Induction's 3003-48a and b series.

------------------

"What would you do if I came over to your bedroom every morning, stuch a vacuum hose on your wife's nipple, and turned the Hoover on? Huh? Huh?"

Man, I need that hardcore. I need ITB's.

-Mulholland

quote Originally posted by RAREW66: OK, what is the source for these pictures??? That engine bay is identical to my PPG Pace Car. Fred

From the yellow PPG pace car taken at the Michigan Fiero show.

quote Originally posted by Mulholland_GT_Racer: Is that an Independent Throttle Body setup?! I want one, where do I get it? -Mulholland GT

That is (was) Kris Munson's 3.4 with a Ryan Falconer intake. Six individual runners and TBs.
He said it was "a b!tch to tune". (I could imagine...)

He has since replaced that engine with a 3.4 DOHC