After looking at my exhaust manifold soe a few minutes it appeared to me that the rear cilynders intake port may not be getting the proper amount of air flow(or maybe it just looks that way) And this got me wondering....... Why don't intake manifolds have 4-1 collectors like headers or other exhaust manifolds.....

Does anyone make an equal lenth intake manifold?


I'll be looking around for a picture of what i am talking about...It's early in the morning right now and I know my head isn't working @ nearly 100% yet so bare with me..

 

Something like this:

with the TB on the single pipe side then then equal lenth runners to the intake ports..

 

There are no collectors on intake ports because for optimum power there has to be a plenum--the volume of which is dependent on the number of cylinders and expected rpm range. For example: 4 cyl, 6000 rpm the volume should be @ 50-60% of total cyl. displacement for optimum power. For higher rpm you reduce plenum volume for lower rpm, you increase it. "The purpose of a plenum is to permit the charge gases to slow down and gain density, and to help isolate the resonant pulses of the individual runners from a desirable overall smooth flow of air through the throttle...........the tradeoffs involve supplying sufficient plenum volume to deliver plenty of airflow versus keeping the volume low enough to keep throttle response from becoming sluggish" (taken from "How To Tune and Modify Engine Management Systems)

 

So how come you can't have a plenum and then have the collector, that way all of the runners are the same distance from the TB... Does that make sense?

We need some of the header guys in here to design one

 

Collectors are designed to flow the other direction. For a general analogy, look at a wing on an aircraft. Smooth rounded leading edge that tapers to a relatively sharp trailing edge where flow from the top and bottom of the wing merges. A wing would not work very well backwards. Performance engine intakes are rounded (look at velocity stacks on some ITBs) to prevent separation, and exhausts have sharp edges where flow merges. This is simplified, but it should help get you thinking the right way...

 

now that makes more sense to me...

So why not 4 velocity stacks in a square plenum with equal lengh runners and each runner begining the same distance from the TB?

 

Full race is designing one right now. Here's the link:

https://honda-tech.com/zerothread?id=979697

Edit: Here's the link the the pics of the inside of the manifold

https://honda-tech.com/zerothread?id=979697&page=7

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Stock@$$GSR &raquo;</TD></TR><TR><TD CLASS="quote">Full race is designing one right now. Here's the link:

https://honda-tech.com/zerothread?id=979697

Edit: Here's the link the the pics of the inside of the manifold

https://honda-tech.com/zerothread?id=979697&page=7 </TD></TR></TABLE> That's not what i am talking about...That manifold is pretty much like every other manifold by design...

each intake runner is a differant distance from the Throttle body... Imgaine an intake manifold that looked like an equal length turbo manifold, but where the collector is on the turbo manifold that is where the plenum would be for the intake manifold and the throttle body would be at the end of the plenum, making the distands to each one of the runners be the exact same, and the runners would be the exact same length....

That way the last to runners wouldn't be getting starved..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 92 civic VX B18c &raquo;</TD></TR><TR><TD CLASS="quote"> That's not what i am talking about...That manifold is pretty much like every other manifold by design...

each intake runner is a differant distance from the Throttle body... Imgaine an intake manifold that looked like an equal length turbo manifold, but where the collector is on the turbo manifold that is where the plenum would be for the intake manifold and the throttle body would be at the end of the plenum, making the distands to each one of the runners be the exact same, and the runners would be the exact same length....

That way the last to runners wouldn't be getting starved..</TD></TR></TABLE>

There is really no need to do this. The only thing this would accomplish is making it harder to get equal length tubes going to each cylinder. If you look at the normal log style intake manifolds, you can see that all of the runners are equal length. If you tried to make them all come into the plenum in a square shape, you would have to put bends in the runners, making them not flow as well. The distance from the throttle body to each cylinder is different in a log style manifold, but, for resonably sized plenums, this does not matter at all. The purpose of the plenum is to act as a buffer of air, with essentially zero velocity inside of it. Therefore the only thing that really matters is the length of each of the individual runners.

 

ITB's.