Just throwing this out there for discussion. The restrictive intake comes up alot. Most everyone is familiar with the enlarged intake that Dawg came up with that has been replicated by others. My question is whether that modification opens up the neck as far as practical or is there a benefit to open it up even further as shown on the blue line on the attached picture? I'll admit i haven't taken the time to look on the top of the engine what would get in the way of this modification. at this point wondering if opening it up further might improve on an idea that is already an improvement to stock. Thoughts?

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1986 Fiero GT Fastback
1979 Naked Honda Goldwing

I'm no air flow expert but I don't think there is much more to gain from opening that up more. From what I understand the intake system as a whole is restrictive. I would suggest eliminating the entire upper and mid section like the Truleo does, although that will be a lot of work. I been researching it and I really like this one, it doesn't look that bad to make from scratch either, uses a lot of stock parts.

quote Originally posted by DaytonTD: I'm no air flow expert but I don't think there is much more to gain from opening that up more. From what I understand the intake system as a whole is restrictive. I would suggest eliminating the entire upper and mid section like the Truleo does, although that will be a lot of work. I been researching it and I really like this one, it doesn't look that bad to make from scratch either, uses a lot of stock parts.

This looks like the one TLG sold...

I think that is the same one, however I couldn't seem to find it online anywhere if they are still selling them. If they are please post a link I would love to buy one, making one was plan B

I don't think TLG are selling them anymore as it's no longer on their website. The only thing you can find about it is the video they have in their tech support section. Maybe they only make them special order now?

Another really big issue that you cannot correct with the stock Fiero V6 plenum is that where it meets the upper intake is a super retriction. It's a near 90 degree turn down connected by sandwich gaskets - not ideal by any means. It's designed this way primarily for space constraints. Doing the Dawg modification will help with flow, but you will still be hindered by the plenum turn down which cannot as easily be rectified.

Bruce did a bunch of flowbench testing and found adding the stock middle to the upper actually increased airflow, so it kind of argues against that theory. Fluids don't act like you would expect always. I think the modification shown on top would work but it might just feed that one runner a lot more so maybe it could go on the other side, there is some space between the distributor and the intake that could be taken up, especially close to where the neck and intake meet where the biggest restriction is.

this is a major topic for talk here...

the stock stuff is restrictive, and alot of people would rather just mod the stock setup rather than delve into a swap.

there is a thread on here where someone is trying to re-invent the plenum to remove the restrictions.

and I remember seeing someone who uses a larger throttlebody (off a 3.4 camaro?) mounted to the top of a modified stock plenum for thier fiero track car
which they dyno tested and it seems to keep making horsepower the higher the rpms go.

i have a copy of the 60* v6 performance guide and the potential of it being naturally aspirated with a carb setup is about 230hp. for racing.

Air doesn't always do what you think it does

Just cause it looks like ~90 turn is a restriction does mean it's a restriction . . .

https://www.fiero.nl/forum/Forum2/HTML/118417.html

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"There is no more formidable adversary than one who perceives he has nothing to lose." - Gen. George S. Patton
http://www.flowbenchtech.com

quote Originally posted by Brucepts: Air doesn't always do what you think it does Just cause it looks like ~90 turn is a restriction does mean it's a restriction . . . https://www.fiero.nl/forum/Forum2/HTML/118417.html

I eliminated that short straight section where the upper and middle meet on both of them creating a single 135 degree bend rather than a 90 followed by .6" of straight path followed by another 45 degree direction change and that didn't seem to hurt me either.

It enabled better porting and polishing.

AL87,
That modified intake with the Camaro TB is mine.
The issue there is it not a stock location and the deck lid needs to be chopped up a bit.
The restriction does indeed look like the neck based on my experiment in eliminating it.
The upper/mid manifold mating area probably is OK. Velocity, I believe, is the key.
I'm not an egineer but love to play one.

Bob

quote Originally posted by mcguiver3: I'm not an egineer but love to play one. Bob

dont we all? lol.

but I can see from your work that the neck is the big deal, and maybe also the throttle body.
and I'm sure porting the upper and lower plenums, as well as the intake manifold will help with flow.
same can be said about porting the heads and exhaust.

[This message has been edited by AL87 (edited 03-12-2013).]

Here is a pic of the ppg pace car intake.



These engines with this modified upper intake plenum and other internal engine mods were rumored to make somewhere around 200 hp if I remember correctly. It appears this mod significantly shortens the intake runners. Combine these ppg intake mods with dawg's mods to the throat area along with a larger throttle body and I think you would have all the intake you would need for most 2.8-3.4 v6 aps trying to maintain a somewhat factory look and still get a decent amount of power out of the engine.

[This message has been edited by av8fiero (edited 03-12-2013).]

I do notice on the ppg motor they did enlarge the area i marked in blue in addition to the area between the runners. any of those manifolds still around to see pictures of everything they did to the manifolds?

the ppg intake also eliminates the upper runners though, where doing that modification to a stock intake would feed one runner a lot more. I think it would cause the airflow in the intake to be really funky and maybe a little detrimental unbalancing the engine.

quote Originally posted by zkhennings: the ppg intake also eliminates the upper runners though, where doing that modification to a stock intake would feed one runner a lot more. I think it would cause the airflow in the intake to be really funky and maybe a little detrimental unbalancing the engine.

All runners would be shortened similarly and all would be feeding off the same now larger plenum, why do you think one runner would be fed more?

While I would think doing these mods would move the manifolds peak power band around, I don't think it would unbalance the engine, as long as all runners are shortened by the same length. All that is flowing through this part of the intake tract is air, as long as all the runners are fairly equal in length the airflow balance shouldn't be negatively effected

No I said if you look at the original posters picture, that modification on an intake that has had no modifications to the runners, just the neck extended how he drew it, it would feed cylinder 6 more than the others. If runners were eliminated like in the ppg manifold it would not be an issue

quote Originally posted by Grantman: Just throwing this out there for discussion. The restrictive intake comes up alot. Most everyone is familiar with the enlarged intake that Dawg came up with that has been replicated by others. My question is whether that modification opens up the neck as far as practical or is there a benefit to open it up even further as shown on the blue line on the attached picture? I'll admit i haven't taken the time to look on the top of the engine what would get in the way of this modification. at this point wondering if opening it up further might improve on an idea that is already an improvement to stock. Thoughts?

Instead of making the neck wider (which I think will have issues with the runner air flow bias), you might consider adding a 1/2 circle tube down the center of the manifold and connecting to the modified neck. This would increase the volume within the center of the plenum and might help increase runner flow. I remember seeing this done before, but can't remember where or how much room there is underneath the upper plenum for this additional tube.

quote Originally posted by FieroDan86: I don't think TLG are selling them anymore as it's no longer on their website. The only thing you can find about it is the video they have in their tech support section. Maybe they only make them special order now?

They quit I believe it was because it cost twice as much to make them as what they could sell them for.

quote Originally posted by fieroguru: Instead of making the neck wider (which I think will have issues with the runner air flow bias), you might consider adding a 1/2 circle tube down the center of the manifold and connecting to the modified neck. This would increase the volume within the center of the plenum and might help increase runner flow. I remember seeing this done before, but can't remember where or how much room there is underneath the upper plenum for this additional tube.

WCF used to offer one like that...

quote Originally posted by 2.5: I think these engines were also enlarged to 3.0 cubic inches.

A whole 3.0 cubic inch engine?