I started construction on a dual throttle body intake, and wanted to keep the EGR. I had thought about plumbing it in to the drilling on where the cold start injector used to reside, but was worried that I would get an uneven distribution, throwing the mixture balance off, and wasn't sure how I would really be able to tell, so I came up with this solution.

Bear in mind that my skills (and available tools) are geared toward cutting metal, not gluing it together, so whatever welding I need I will have to pay to have done, so I kept it to a minimum. Also, everything was the scrap I already had, so there are some changes I would make if I were buying materials.

I started wanting to bolt the new intake to the stock middle manifold, so I drilled out the holes and counterbored for the bolt heads.



I then cut out a couple of plates from 3/8" stock, using the gasket as a template, drilled and tapped them



Plates bolted to the manifold, port matched, and port entrys radiused.




Tubes were made from some schedule 40 3" Pipe. I decided to bolt on the ends, using three long through-studs each. I cut to length, bored each end to true them up, cut a 45 to hold O-rings at each end, and made end caps. The front of the engine caps are drilled and tapped 3/4 pipe, to take a balance tube, and drilled for the thru-studs; the other ends are pilot-bored for the throttle bodies, drilled for retaining bolts, and drilled/tapped for the thru-studs. The tubes were then milled out to fit the plates on the manifold.




OK, the EGR part. The stock upper intake injects the exhaust right behind the throttle body, figured I could do the same, just injecting on both sides. I took a couple of pieces of 1/2 x 4 bar stock, indexed them together, measured the center to centr distance on the middle manifold, and bored the two holes for the throttle bodies. I took the bare bodies, aligned them with a single shaft, and drilled/tapped the mount holes. The EGR was located and mounted in the center, holes drilled in one plate for the ports. I then milled slots to connect the EGR to the TB bores, drilled and tapped to hold it together, and cut away all the excess material.



Plates bolted together, with TB end caps, and EGR valve



Trial assembly





So, its off to the welders with this on Monday, to get the plates welded to the bottom of the tubes. In the meantime, I can start on the TB's

Mike

Beautiful work. Finally someone is doing it right. Looking forward to the finished product.

quote Originally posted by fast40driver:

Nice work, Mike!

Will the assembly you built for the EGR also work as a "balance tube" to any significant degree between the two banks?

all i can say is....I WANT ONE!!!!!

That is a creative approach and looks pretty good. Before the welding, I would suggest mocking it up with the fuel rails and injectors and on the engine just to make sure everything clears, if you haven't done it yet.

Edit... don't know what happened with the red angry smiley... must have hit that thing by mistake.

[This message has been edited by fieroguru (edited 03-19-2011).]

That is a nice looking piece you are making, great work

quote Originally posted by fast40driver: So, its off to the welders with this on Monday, to get the plates welded to the bottom of the tubes. In the meantime, I can start on the TB's Mike

Did you get rid of the EGR mount on the Y-pipe (or even the Y-pipe itself?)
Personally, I would have left the EGR valve on the Y-pipe and plumbed a flex line similar to the stock piece to your "EGR Manifold"...

That's a lot of nice looking machine work, though

[This message has been edited by Will (edited 03-19-2011).]

Nice fabrication !

Thanks for the kind words. Yes, it does clear the fuel rail and injectors - I did check that. Figured I was going to have to make an adapter block for the EGR anyway, so it was just as easy to incorporate it into the manifold parts as to mount it on the Y pipe. I did see somewhere that the Valves did not like to get to hot, and certainly the car I got that one from had it remote mounted with a tube supplying exhaust to it. Figured I would use a stainless gas connector tube to bring the exhaust to the valve, also figured that with the amount of airflow through there, and the cooling of the exhaust in the tube going up to the valve, I would not add too much heat to the manifold assembly.

As regards the balance pipe, I really am not sure. I would think the area of this connection would be suitable t idle, but with the airflow past the entry point it would not do much off idle. I have always assummed that the twin manifolds built without balance pipes got away with it as there is somewhat of a balance pipe in the lower manifold - the idle air passages connect all of the ports. I thought I would add a reasonable sized one off of the front end caps, mainly for part throttle, and mainly because I don't know how you would tell if there was a differece, besides running the engine under load with a manometer hooked to the two manifolds. Easier to just add the balance pipe and be done with it.

Mike

If you wanted to make a similar EGR manifold plate setup instead of the rear caps, and make the passage larger to act like the balance tube between the two plenums w/o it being obvious

quote Originally posted by fieroguru: If you wanted to make a similar EGR manifold plate setup instead of the rear caps...

From a symmetrical point of view, that would look real sweet.

So I have a couple of questions.....first, how much to make me one?

Second, I am no good with engines at all so what I am wondering from those who understand the dual plenum intakes, is the 2nd Holley throttlebody just a dummy to let an equal amount of air in and the sensors are connected to the other throttle body only or do both throttle bodies use the sensors?

[This message has been edited by IMSA GT (edited 03-19-2011).]

The engine mainly runs off of the MAP sensor, which I will probably run off of the balance tube. BTW, good idea on the manifold at the other end. I was actually planning on using some rectangular bar stock, boring it, and turning hose connections on the ends, then installing with real short pre-formed 90 degree hoses - Wasn't sure yet on clearance to the thermostat neck. But you now have me thinking.

The throttle cable will hook to the throttle body on the front side. It will also carry the IAC motor - only one is needed, and it is easier to plumb from the front, closer to the stock location. The TPS sensor will run off of the rear TB - it drives off of the end of the throttle shaft. Coolant passeges are deleted from both, I am going to use a 7730, so I don't need the evap signal, or the EGR signal, so some of the TB's was trimmed away. I will get some pictures up on the TB's when I get a little closer on them.

I did pick up a cover off of a Quad 4 to cover the injectors - I saw someone on here had done that - nice idea and it looked good. It is "finned" like the valve covers, so I will probably mill some grooves in the tubes to match.

We'll see how it works out, and how much time I have in it total.

Mike

Very cool! I wish I had this kind of ingenuity!

Where will you connect the break booster vaccum line?

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Bernard
Fiero V6 GT 1987 (Manual)

Man, that looks awesome... I can't wait to see it finished.

What do you expect to get from it in terms of performance? Is this going on a 3.4? What is your target goal? High RPMs? 200hp? etc?

WOW!!!

Any updates on this project?

Gary

Awesome sauce! I would like to propose a name for it. How about "The Pipe Bomb"?

quote Originally posted by 86FieroSEv6: Awesome sauce! I would like to propose a name for it. How about "The Pipe Bomb"?

LOL!! well if it was named that then that would give people another reason to fear our cars catching on fire but only this time more "violently" good name tho id buy it!!! but when i searched "Pipe Bomb" on the internet i dont think this would be the first one to pop up, and i think the FBI would show up at my door

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1987 Black GT Custom interior with Mr. Mikes seats soon

That looks amazing! I cannot wait to see it all set up. If you need any help with the 7730 swap Id love to help get that all working. I actually have a 7730 ECU with pigtails and the proper 87 4cyl ecu holder to mount it.

With everything you've helped me with its the least I can do. Ill be done with school in a couple weeks and back in your neck of the woods. Ill look you up then and see this creation for myself!

Great Job! This looks like it was done by GM itself ! it will be interesting to see how much better it performs over the stock intake.

bump, any updates on the setup?

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1986 Fiero SE 2.8 Auto - Blackie
1985 Fiero GT 2.8 4-spd - Goldie II - To be driveable this season
1985 Fiero SE Targa - 3.8SC - long term project
1987 Cavalier Z24 2.8 5-spd - daily beaten driver
1993 Bonneville SSEi - 3800SC donor for 85 Targa