C (the small fitting) is ported vacuum for EGR. B is ported vacuum to the evap canister.
The coolant lines are generally considered a throwaway, especially on an aftermarket installation. (Mine have been gone for years with no ill effects,) It is not necessary to cap them but they can be, for appearance. I believe I even removed the brass fittings shown in the pic.
Edit - Great diagram, Blacktree!
[This message has been edited by Raydar (edited 09-07-2007).]
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06:43 PM
Gokart Mozart Member
Posts: 12143 From: Metro Detroit Registered: Mar 2003
Is there any specific reason for it to be two separate plenums? Some of the concerns of EGR and vacuum hookups have been brought up already. Now, I'm not suggesting a design change - just musing a bit. And possible thinking about mods to this product or add-ons.
The Camaro 3.4 SFI used a similar intake, with a plenum over each side but they were Y-ed together with one throttle body. You could possibly make up an add-on y-pipe to do the same and run one larger throttlebody. That still gives the other benefits of the dual system - fuel rail access, looks, etc.
Another thought is a large bridge between the two plenums. In effect making a large H shaped plenum with the EGR and vacuum connections going to the balance bridge. This would need to be larger than a hose - maybe half the diameter of each plenum?
Any ideas or thoughts?
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10:21 PM
Raydar Member
Posts: 40747 From: Carrollton GA. Out in the... country. Registered: Oct 1999
Originally posted by Formula88: ...Any ideas or thoughts?
Every argument that I've ever heard pretty much concluded that a common plenum (or even a balance tube) is not necessary. If both halves of the engine are the same, there's no reason for the balance to be off. Aside from that, there is still a common chamber to the intake system. It's the center of the lower intake, where the CS injector and Idle Air tube are located. Granted, it's not much of a connection, but it's probably enough.
Of course, I'm willing to listen to any arguments. It's not like I actually have any experience with this.
Edit - It would probably be easy enough to test. All it would take would be two identical vacuum gauges.
[This message has been edited by Raydar (edited 09-07-2007).]
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10:35 PM
Sep 8th, 2007
Formula88 Member
Posts: 53788 From: Raleigh NC Registered: Jan 2001
I'm thinking not so much for balance, but the bridge gives an easy way to hook up vacuum lines and EGR, and a Y gives the advantage of only 1 throttle body and makes the cabling, etc. easier.
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01:41 AM
PFF
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toddshotrods Member
Posts: 1177 From: Columbus, OH, USA Registered: Aug 2004
Maybe in subsequent versions (if this one sells well enough), but this plan is pretty much set. It is intended for owners who want the exotic car look of dual plenums and dual throttle bodys; and a less restrictive upper intake setup. That person has to be willing to deal with some minor inconveniences; e.g. working out the details of the vacuum system and EGR. As I indicated, I plan to release a complimentary vacuum setup later. My goal is to include a linkage bar for the throttle with the intakes.
I thought the vacuum and EGR requirements were more complicated.
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02:52 AM
craigsfiero2007 Member
Posts: 3979 From: Livermore, ME Registered: Aug 2007
Originally posted by toddshotrods: I thought the vacuum and EGR requirements were more complicated.
I think the vacuum can be taken from either side, with no issues.
The EGR is another story. The Fiero upper plenum has a ~1/2 inch hole in the underside, just behind the TB, where the EGR tube attaches. This EGR *must* be fed to both banks of the engine if it is used at all.
My fix for this (if I even keep the EGR for this application, which I doubt) will be to run it to the lower intake, where the (unused) cold start injector now resides.
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11:52 AM
Blacktree Member
Posts: 20770 From: Central Florida Registered: Dec 2001
I agree with Raydar. The idle air / cold start passage in the lower intake should be more than enough to equalize pressure between cylinder banks. The idle air tube and cold start injector hole are also convenient places to plumb in the vacuum / EGR / PCV lines.
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12:20 PM
p8ntman442 Member
Posts: 1747 From: portsmouth RI Registered: Sep 2003
Todd, as a sugestion, not a demand. If you incorporated a couple mounting tabs on the inside of each log, you could use a peive of sheet metal bolted to the tabs to cover the valley. This sheet metal could be custom engraved, or painted. It would be at an aditional cost to the customer, But I think it would look very nice. If I buy a DTBI I will buy one like that, or modify the one I buy to work like that.
.02
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02:08 PM
toddshotrods Member
Posts: 1177 From: Columbus, OH, USA Registered: Aug 2004
Todd, as a sugestion, not a demand. If you incorporated a couple mounting tabs on the inside of each log, you could use a peive of sheet metal bolted to the tabs to cover the valley. This sheet metal could be custom engraved, or painted. It would be at an aditional cost to the customer, But I think it would look very nice. If I buy a DTBI I will buy one like that, or modify the one I buy to work like that.
.02
I like it. I have a couple ideas for it that wouldn't stick people who don't want it with tabs on their otherwise clean plenums. More on this later...
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02:24 PM
Blacktree Member
Posts: 20770 From: Central Florida Registered: Dec 2001
Originally posted by p8ntman442: If you incorporated a couple mounting tabs on the inside of each log, you could use a peive of sheet metal bolted to the tabs to cover the valley. This sheet metal could be custom engraved, or painted.
It wouldn't necessarily need to be sheet metal, either. You could mold the cover plate from fiberglass, or... dare I say... carbon fiber.
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04:34 PM
toddshotrods Member
Posts: 1177 From: Columbus, OH, USA Registered: Aug 2004
Aluminum and carbon fiber would be offered. I feel better about carbon fiber on top of the engine (heat). I don't want to produce them but carbon fiber valve covers would finish that off nicely
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06:05 PM
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System Bot
Sep 9th, 2007
mtownfiero Member
Posts: 1779 From: Mansfield, Mass Registered: Mar 2007
you can mimic carbon fiber with paint pretty easily. I saw it on tv i think you just paint the part in silver then lay a mesh fabric over it and then paint over the sillver with black and when you remove the mesh it looks like carbon fiber.
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10:38 PM
Sep 10th, 2007
Chris Hodson Member
Posts: 3066 From: Carpentersville Registered: Aug 2006
Not really, the thermostat cover already has the connections for the TB coolant lines on it. Just bypass to the intake. But that would just heat up the intake like it heated the TB. Unless your boosting, cooling the intake isnt necessary. You would be better off using Phenolic spacers on the 2 tubes to prevent heat soak.
mmmm you need to do one for the 3.4 dohc id buy one in a heartbeat.
I need to see a 3.4 DOHC with the uper intake off. Doesn't seem like it would be that hard to accomodate. Also, I need to know if the TB flange is the same of different. Anyone have pics and info???
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06:07 PM
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Sep 13th, 2007
p8ntman442 Member
Posts: 1747 From: portsmouth RI Registered: Sep 2003
Every argument that I've ever heard pretty much concluded that a common plenum (or even a balance tube) is not necessary. If both halves of the engine are the same, there's no reason for the balance to be off. Aside from that, there is still a common chamber to the intake system. It's the center of the lower intake, where the CS injector and Idle Air tube are located. Granted, it's not much of a connection, but it's probably enough.
Of course, I'm willing to listen to any arguments. It's not like I actually have any experience with this.
Edit - It would probably be easy enough to test. All it would take would be two identical vacuum gauges.
You can get away with two totally seperate pleniums, however; unless you balance them with a vacuum setup like they do with 4 carb cycle engines they will NOT be blanced, close, maybe but not balanced. Those throttle plates have to open at the same time and they should continue to open at the same rate 9somethign some dont check for) . Some may say it dont mater. If didnt mater then CC heads, keeping runner lenghts the same etc dont mater either.
And one note on Y-ing the two pleniums to one big TB, has its merits. But doing such, would also likely add to plenium volume which most dual plemium designs already have too much of, and that makes for slugesh throttle response.
