I have recently acquired a TIG welder and all the cool things that I can do with it are starting to coming to mind. I have decided to make a dual plenum intake. I know it's been done before but i've never seen anyone discuss how they actually perform and the possible risks involved. Also, how do you get the IAC to work right? Can you use 2 IAC valves wired in a series?

All you need is one. Probably the one nearest the firewall.
You'll have to extend the tube down to the fitting on the lower intake.

At least that's what it looks like to me.

If I remember right when I talked to the owner of this one he used only one set of sensors like the IAC and TPS.

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That intake is very cool and makes the engine look more classy IMHO

Arn

If you look at the Truleo design, it is very nonrestrictive. Its a single plenum but that's really all that you really need.

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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.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

Yes, but dual plenum's can be built CHEAP and have at least as much power potential as the Truleo

Same one as above, but with a nice cover over the center area.

I was trying to visualize what a dual plenum with a cover in the middle would look like. Now I know!

Does anyone know who built this one? And if he is interested in explaining how he made it? I'm very interested in making one like it I love the way they look! Imo they look cooler than the trulo one that I can't afford! Haha nothin agaist the trulo one I really like it to! Actualy I kinda wish they made a duel runner style intake plenum

This guy on 60degreev6 did one. I expect you can contact him for info.

http://60degreev6.com/forum...enum-part-two-t39024

Arn

I've got one of those laying around The tubes are a bit small to run the Fiero tb's and feed 1.4 litres each. I need to make them just a bit bigger, which means I need to learn how to weld aluminium. Bugger.

quote Originally posted by Will: Yes, but dual plenum's can be built CHEAP and have at least as much power potential as the Truleo

You need two throttle bodies, a modified ( and accurate) cross linkage, two air hoses and probably more metal to build a dual plenum manifold. I dont see how it can be done cheaply. I will admit that it does look nice though.
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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.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 03-17-2009).]

Any chance you want to let it go? Haha I can weld aluminum and thats pretty much exactly what i want! Haha

quote Originally posted by Dennis LaGrua: You need two throttle bodies, a modified ( and accurate) cross linkage, two air hoses and probably more metal to build a dual plenum manifold. I dont see how it can be done cheaply. I will admit that it does look nice though.

Two pieces of tubing and two flanges are the materials required. Fiero throttle bodies are CHEAP. The first DPM built used a modified throttle cable installed on the TV cable boss on the first throttle to work the second throttle.

This is not a big deal.

I only see one TPS and one IAC in the dual plenum setup above. I was wondering if one IAC serving one bank is good for the motor. Wouldn't it be off balance if one bank gets air and the other doesn't?

I made some pics to show the product of me thinkin' real hard for a couple days:
EDIT: sorry, these pics were WAAAY smaller in MS Paint
This one is from the front, it shows how it keeps the intake length tuning in order with a supply of air still available in the tubes.
This isn't supposed to be precise mechanical drawing, some dimensions will be larger to promote flow.


This one has a few mock ups of air filters and cold air intakes, i like the 2nd one the best.
The gray blocks are throttles and the orange parts are filters


This will be easy to build with some steel circular tubes, square tubes, and some plates.

[This message has been edited by MordacP (edited 03-17-2009).]

I like the third one if you have the stock airbox mods and a k&n drop in filter you would be good to go!

The third one would work well with the cavalier air box (uses stock fiero air filter):
Topic: Improving the stock V-6 cold air intake can
https://www.fiero.nl/forum/Forum2/HTML/096287.html







Since the hole is of-set you could add another one beside it from the same can to get the second feed like the third picture above

quote Originally posted by MordacP: I only see one TPS and one IAC in the dual plenum setup above. I was wondering if one IAC serving one bank is good for the motor. Wouldn't it be off balance if one bank gets air and the other doesn't?

The IAC fed idle air circuit is fed into a chamber in the lower intake manifold feeding all the cylinders. This is a moot issue. You are only pulling air from one throttle body, that's all that's needed. You do need a balance tube on the dual tb set up though.
And no I will not sell the one I have, I just bought it
The difference between the dual tb set up and the Trueleo is the Trueleo has a larger plenum volume for higher rpms with the right sized tb. THe dual tb set up improves low end, but if teh tubes are too small, like mine, they actually hurt the top end, especially with larger tb's. There is a lot of boring math and theories involved. I'm just going with what I've experienced on the dyno.

quote Originally posted by topher_time: The IAC fed idle air circuit is fed into a chamber in the lower intake manifold feeding all the cylinders. This is a moot issue. You are only pulling air from one throttle body, that's all that's needed.

Oh yeah... I knew that!!!!!

As for hurting the top end with a small volume intake, that's exactly why I have the tubes offset from the runners with the extra chamber on the side. Hopefully that's enough.

quote Originally posted by TopNotch: Same one as above, but with a nice cover over the center area.

That's beautiful ..

Amusing that it's a Quad 4 cover on a V6.

I'll never understand the desire to cover up an engine. With the time spent improving it and building it up, why on earth would anyone cover it up?

[This message has been edited by Will (edited 03-18-2009).]

quote Originally posted by Will: I'll never understand the desire to cover up an engine. With the time spent improving it and building it up, why on earth would anyone cover it up?

De gustibus non est disputandum.

In a thread from The Mall here, titled, "Introduction: Top Line Group Automotive" ( https://www.fiero.nl/forum/Forum4/HTML/045660.html ), fellow PFF member, Oslo, who started TLG Automotive, stated:

quote Originally posted by Oslo: We have plans in the future to offer a custom dual throttle body intake manifold....

I'm curious to see what, if anything, arises either from the dual plenum intake manifold efforts mentioned immediately above or previously in the current thread because IMHO, the dual plenum pictures posted above look great, so hopefully, somebody will manufacture one of those for sale!

quote Originally posted by Will: Amusing that it's a Quad 4 cover on a V6. I'll never understand the desire to cover up an engine. With the time spent improving it and building it up, why on earth would anyone cover it up?

I actually like the look of the Q4 cover. Matches the valve covers pretty well, IMHO. What doesn't make sense to me is why go to the trouble of installing a fuel pressure gauge, then cover it. That cover needs a hole machined into it now.

Maybe you can see it from the other side.

So i was hoping that somebody who actually has a dual plenum could tell us how it works for them.

quote Originally posted by MordacP: So i was hoping that somebody who actually has a dual plenum could tell us how it works for them.

Not as good as a full itb set up. Throttle response is only slightly changed. Helps a bit in the upper rpm's but not as much as it should. I need to do something with the exhaust. Sound is off, needs a balance tube. Worth it? for performance, no; well maybe if I were to really open up the 2.8 and do some supporting computer tuning to maximize its potential, it might then be more noticeable. Need to do more math to match the tubes to the engine. But for looks, yes. Everyone notices it and asks where I got it. No one tells me a V8 will fit in there anymore

quote Originally posted by Will: Amusing that it's a Quad 4 cover on a V6. I'll never understand the desire to cover up an engine. With the time spent improving it and building it up, why on earth would anyone cover it up?

The valley is ugly

quote Originally posted by Erik: The valley is ugly

Yeah, but if you plug your nose, then it is approachable.

quote Originally posted by topher_time: Not as good as a full itb set up. Throttle response is only slightly changed. Helps a bit in the upper rpm's but not as much as it should. I need to do something with the exhaust. Sound is off, needs a balance tube. Worth it? for performance, no; well maybe if I were to really open up the 2.8 and do some supporting computer tuning to maximize its potential, it might then be more noticeable. Need to do more math to match the tubes to the engine. But for looks, yes. Everyone notices it and asks where I got it. No one tells me a V8 will fit in there anymore

Performance improvement measured on a butt dyno?

quote Originally posted by Will: Performance improvement measured on a butt dyno?

Sorta. Once I get this rod knock taken care of and a few more miles on it, I'll confirm my suspicions on the dyno.

The DPM shouldn't give an increase in torque. It should only allow the engine to carry its torque to a higher RPM. This is exceedingly difficult to detect with a butt dyno. Significant improvements that show up with real dyno results and in 1/4 mile timeslips can be very hard to feel.

the "Butt Dyno" may not be a valid scientific instrument - BUTT I must say - must of us drive our cars for "satisfaction" - which is also unquanitifable on a dyno. and, I do belive the Butt Dyno DOES in fact measure satisfaction.

so, while I agree with the fact the Butt Dyno will not help much on 1/4 mile estimations - it DOES provide a guess towards "satisfaction", which to many of us - is equally important.

The gentleman that has the setup that Topnotch posted, was from Columbus, Ga. I may be wrong, but I believe he said everything was custom built by himself, including the (quad4) cover. Don't remember his name. He came to a couple of Ga. Fiero meetings. Topnotch may have his info in the club records, somewhere.

If anyone is interested the above engine and the car that it is in will be at Daytona this year.

I almost bought this manifold when it was being advertised here in the Mall, but I decided in the end it was probably going to be more trouble than it was worth (performance wise).

I take it you reviewed this thread, which has many versions and some working ones, and the links to articles that tell you how to size each bank's volume properly, but I think those links may be dead now.
https://www.fiero.nl/forum/Forum2/HTML/077346.html

Yes I did, and alot of other informational sources, but in the end it is just as they say, everything is a trade-off. What you try to design for on one end you have to give up on the other. One thing I have to say about this set-up is the top end flat spot is gone. Mine used to come in around 45-50K RPM. It will pull hard all the way up through 6000 RPM now.

Good Luck.

quote Originally posted by Patrick: I almost bought this manifold when it was being advertised here in the Mall, but I decided in the end it was probably going to be more trouble than it was worth (performance wise).

actually looks like a good design. even has EGR - which most wont.
center balanceing tube, with all the vacuum ports.
yes, it is UGLY tho, eh? and, I do question how well that thing seals to the Lower Plenum