Intake manifold design considerations.....

XR7 Dave

Registered User
As we work on a new cylinder head design we are also faced with intake manifold questions that need to be addressed in an orderly manner so lets take that discussion here so that we can do the topic justice and the other threads can stay on track.

Before stating that the stock intake is crap, you have to look at the design considerations that influence what you can do with it. We all know that hood clearance is a major issue. How do you package something under the hood of the SC without making radical changes to the rest of the engine bay and the car in general? We already know that a 3/4" raised top comes real close to the hood on an 89-93 model SC. Since logic dictates that people are going to use M90's and 3/4" raised tops on their SC's, then we have to ask, do we want to design an intake manifold that is less than 1/4" taller than the stock unit? Is it worth the time and $$? What can we do to the existing design that will make it better without raising the lid?

People talk about runners, diffusers, etc, but where do we put these devices and what added restriction are they going to cause in an area where space is too small already? Putting any kind of a runner in the stock lower intake will be extremely restrictive. There are reasons why most blower cars use open plenums.

Gut reaction tells me that only through testing can one expect to make real progress on something like this. As you can see from our lovely exhaust manifold discussion there are many theories and ideas, some of which are very dearly held, and which vary greatly among the group of us.

Intake manifold design is an art. The fact remains that we do not have the resources among us to follow through with a lot of testing on a manifold that is really intended only for people with stock hoods and M90's on their cars. Does that market really need a new intake?

I don't want to sell anyone or anything short, but we all need to look at what we are asking and what it means. If we spend our money on an intake that fits the stock SC, then how does that benefit those who really want to go fast and are ready to ditch (or already have) the stock hood and try something really new?

These are questions that need to be answered. If you have opinions on this you need to speak up now. Keep also in mind that opinions are one thing, but if you/we don't have or cannot find answers then we are not going to entertain ideas that we can't act on.

A package deal seems like a great idea, but what do we really want? Do we want a new manifold that simply bolts in place of the old one with symetrical ports sized to match the new heads? Should it accept the old return adapter or do we need a new one of those also?

Speak. :)
 
I won't get into a low reply, but I don't think designing a new intake to fit under the stock hood would be beneficial. I know there is something nice to be said about fitting under the stock hood and being a sleeper, but I think it will limit the potential performance gains. Anyway, I say don't worry about the stock hood.
 
I agree with Kurt. If you're going to all the trouble/expense of improving the intake, optimize it and don't be limited by the hood.
 
I think simplicity of installation and being able to do all the work tyourself is very important to most people who work on SCs. Obviously the new intake manifold should be port matched to the new head design to take full advantage of the new heads. As far as hood clearance issues; I would definitely be willing to buy a raised hood if it's going to mean I get a significant power gain from the new intake/head package. I personally would like to be able to reuse all of the stock hardware that is already attached to the stock manifold such as fuel rails, etc. I'm thinking the return plenum at the rear should be an option but not really necessary to run the new head/intake package. It would however be a nice option to be able to get a 3" return plenum for use with a front mount with larger than stock tubing. As all of these things are considered we may get too carried away and put the price out of reach of most people thus defeating the purpose of having affordable bolt-on horse power. I'm sure people with more knowledge than me will chime in and this will get the same attention that the heads did, ensuring a high quality, affordable alternative to the stock parts.
 
In my humble opinion any way you look at it, restricting the design of a new intake to fit a stock hood would be a mistake. It can be as easy as getting a new hood or cutting a hole in ur stock one:rolleyes: . I'm sure this would be an excuse for many people to get an aftermarket hood. I agree with what has been stated above, i'd take the height restrictions out of the list of considerations and focus more in the performance aspect of things and flexibility of use (not sure if this would be an m90-specific manifold or also to be used for the other power adders like the AR). Even the 'ease of installation' would be irrelevant....either way, you have to take whatever blower you have out...just doign that takes teh 'easy' out of the job:p .
 
This is what I was preaching awhile back. Ford probably but alot of effort into designing that POS lower intake we have in such a small confine...I mean even if we redid the lower intake and raised the blower to a point where it was barely touching the hood..Would it be worth it for a stock m90??? Then where is the point the stock SC top becomes a restriction? Maybe make a design for a raised cowl type hood..But still how much can you do?

Now lets say we work on a lower intake within factory confines to an extent...What can we expect..Probably something very close to what we have out there now but a nice casting with proper diffusion going on..And a difused return adapter of larger size may or may not be warrented as well.

If the heads being created have room for larger intake ports then that would warrent a lower/return adapter setup on that merrit alone.

Some of us may not care about having a hole in the hood and a raised up blower..Those same people would also have FMIC's and probbably all out racecars..They also may not be using an m90 at this point...Or shouldnt if they are going through all this

What I see being produced? A modular lower intake with liquid to air IC's that can accept a majority of blower combos..m90, AR, perhaps a cobra m112???

Or a factory replacement lower/return adapter acombo rased/diffused with more material around the intake ports to allow for porting of the new heads. We can use that extra plenum volume..

Just my thoughts
 
I just read two more posts finished before mine....taking height restriction out to clear lets say a raised cowl is an idea..However how much can you get in there even with that...WOuld it be worth it for an m90 or a larger blower in which the clearences would be different. Then again when would that non raised top become a restriction?...New IC pipes would be a definite or new IC setup..List goes on...
 
How much can you lower your engine? How much can you lower your cradle? If height is the biggest problem here than we are very limited. I am not going to say that we NEED the taller one, but lets face it, I think the bend from the "dip" in the runner seriously cuts down on flow. That is why the raised ones do better initally. Just my .02

Chris
 
I think the height restriction should be a Mach I/Cervini style hood. There are many of these hoods out there and it gives an inch and a half or so to raise the manifold up.

I haven't done any flow testing yet of the intake plenum/manifold. However, it would be pointless to make a new manifold if we simply move our choke point from the manifold to the intake plenum. That plenum is less than optimal in stock form. If we are looking at getting performance out of the manifold, the plenum needs to be considered as well. And I will say it for those who don't really know...The intake plenum chokes where it mates to the manifold. That point there is too small to get performance out of an newly designed manifold.

I think if people are going to the effort of buying a new manifold for the sake of performance, they won't have a problem buying a raised hood. I do think that we need to keep the design so that any raised hood would fit the bill...although I'm all for the Cobra R hood, since I have one...
 
Since the whole purpose of the new heads is for performance a new raised intake manifold should be designed as well.

What I would like to see is the height of the manifold to be limited so that a Cervinis hood could be used (there should be enough room to get great gains)so people who do not like the look of the Corba R hood have a choice.

Like Tim said it would also be nice to be able to use the factory fuel rail to keep cost down.

Most owners who are going this route will have a FMIC so the need for a larger intake plenum is mandatory (why have a bottle neck). Would it be cost effective to have the intake plenum cast as a part of the manifold so it is a 1 piece design OR to have it as 2 seperate pieces?

Let's face it right now you can get a whole lot of power out of "factory type" heads and be able to fit everything under a stock hood...If you want a LOT more power buy a raised hood OR get the sazall out and cut a hole in the factory hood.

(I love the look of a factory hood but will go to a raised one for this type of performance.)
 
I say what you do is work on a design that is as compact as practical without hindering performance significantly. Then build a prototype and figure out what hood will fit over it.
 
It would make way more sense if people were to ditch their FMIC setup's and just go with the inverted blower setup. You have a nice water-to-air intercooler and the air only has to travel a matter of inches and not yards. By doing this you take away the height of any top, since it will not be used, and add that length to an intake runner and/or plenum. Other miscellaneous advantages will go along with it as well such as, less weight, you can see your motor, spark plugs will be easier to get to, headers would be an easy access, and you could even see the new valve covers that are considering being made.

Diffusion isn't really a big deal if you have a runner type intake. All of the diffusion is ONLY supposed to happen at the length of the runner. Runners create the diffusion. Everything else is the volume of the plenum in the intake manifold.
 
Casey that was one of my options..Inverted liquid to air. But I am unsure how much runner you can get in there without really raising that blower up...It is ideal though because you could then make it a modular peice to fit a multitude of blowers with only a spacer plate difference
 
inlet

I would like to see a 3" inlet on the plenum if the plenum is utilized. I would think most who actually buy the manifold set up already are going to have an aftermarket intercooler set up with 2.5" to 3" tubing. I don't really care about the height as I would buy a new hood.
 
It would make way more sense if people were to ditch their FMIC setup's and just go with the inverted blower setup. You have a nice water-to-air intercooler and the air only has to travel a matter of inches and not yards. By doing this you take away the height of any top, since it will not be used, and add that length to an intake runner and/or plenum. Other miscellaneous advantages will go along with it as well such as, less weight, you can see your motor, spark plugs will be easier to get to, headers would be an easy access, and you could even see the new valve covers that are considering being made.

I agree that it does make sense to go that route however I feel that it would add signifigant cost for the entire package thus limiting the amount of units that will be bought.
 
Casey that was one of my options..Inverted liquid to air. But I am unsure how much runner you can get in there without really raising that blower up...It is ideal though because you could then make it a modular peice to fit a multitude of blowers with only a spacer plate difference

If we go inverted, wouldn't we have about 2 more inches to work with? Exactly how tall is a raised top?

How tall is the intake on this GTO setup?
 

Attachments

  • thumbBuilder.aspx.jpg
    thumbBuilder.aspx.jpg
    37 KB · Views: 378
It would make way more sense if people were to ditch their FMIC setup's and just go with the inverted blower setup. You have a nice water-to-air intercooler and the air only has to travel a matter of inches and not yards. By doing this you take away the height of any top, since it will not be used, and add that length to an intake runner and/or plenum. Other miscellaneous advantages will go along with it as well such as, less weight, you can see your motor, spark plugs will be easier to get to, headers would be an easy access, and you could even see the new valve covers that are considering being made.

Diffusion isn't really a big deal if you have a runner type intake. All of the diffusion is ONLY supposed to happen at the length of the runner. Runners create the diffusion. Everything else is the volume of the plenum in the intake manifold.

All of this DAYS after I get a new IC for the front:rolleyes:. Oh well, if it DOES go with the inverted blower, what kind of heat transfer cooler will go with our cars? Is this like a mustang unit to keep the cost down? I can see some benefits from this too.

Chris
 
I was researching what the GTP guys do and found this. A plate style IC that only takes up 2.25 inches.

http://www.zzperformance.com/grand_prix/products1.php?id=420&PHPSESSID=7591cd07d56545106d67fe56f1c31864

420_1.jpg
 
I cant imagine that working all that great...Probably a mini tranny cooler or something..Remeber they dont run nearly as high boost or ACT as we do

And yes the fact we are inverting it gives us more room..Room to put an IC underneath..Not nec runners of any signifigance

And Chris...You can still use teh heads with a factory lower..SO that groovy front mount can still be used
 
Back
Top