in an application where there is no fuel going through the intake (just air) would a sheet metal intake give the kind of problems that it does in a fuel/air setup?

I was thinking about building one for my GN... what ya think?

 

What kind of problems do you mean?

 

I think he means will the sheet metal surface beable to mix the A&F but with out the Fuel.
Can you tell us more, you got me a little confused.

 

Not sure what kind of proplems a sheet metal intake would cause. ProStock cars use a sheet metal intake with 2 dominator carbs sitting on top. There's A/F going through those runners and they have no problems.

 

A sheetmetal intake on a boosted application doesnt do a whole lot IMO, GN guys are running deep in the 9's with modded stockers.

David

 

I wouldn't be so much concerned with the materials/method-of-fabrication as I would with the design. Being "sheetmetal" doesn't guarantee you a better intake, just a cost effective way to build a custom.

Surface finish is extremely smooth in the PS intakes I've seen. They have gradual taper and CNC toolmarks that run perpendicular to airflow, just like the good CNC porting you see in some cylinder heads.

-Mindgame

 

Wouldn't mind seeing inside a Pro Stock intake one of these days. It would be interesting with a set of calipers and some expanders to get measurements.

Bret

 

sheetmetal is great if you know what you are doing. packaging restictions barred, you can get any size runner you want!

 

I guess I didn't mean problems so much as design concerns. I know there won't be puddling issues (no fuel in the intake), but how important is runner length when there is no fuel mixed with the air? Additionally, how important is runner length with forced induction?

 

Runner length is always important in a NA motor and u can just about throw it out the window in a blown motor.

Bret

 

How important is runner length? its the pretty much the POINT of a sheetmetal intake.

Just because you have boost doesn't mean you can put together a ****ty engine.

 

Here is little some thing on intake runner length .
A lot of new N/A cars use upper (4th most of the time) harmonic ranges to make a lot of power.

 

hmm, ok... so one guy says it doesn't matter on a boosted application, the other says it does...

I have seen that intake runner length chart, but it was made by a guy running N/A. So that's why my question evolved int he first place... does the chart even apply to forced induction applications?

 

that chart varries from engine to engine.


you cant just say "i have an engine, i want this intake runner length, this header primary, this cylinder head cross section and this header primary length." or at least there is to my limited understanding.

Wouldn't the waves and such varry based on firint order, location of ports, angles, camshaft events, engine config etc?


Not to say they cant be a rough estimate though

 

My chart
is based on every recipercating engine that uses 720 degree crank rotations.
I made this chart
on microsoft paint.
I made it to use to make a plenum.
If I can find a factor to correct the harmonic ranges at a given boost level I will make more harmonic charts at a given psi. It will be cool to say the least.
Like one for 4-5 psi 10psi and 15 and so on. That is if there is a big difference in harmonic ranges in these pressure differences.
The bigger the cam the better it will work.
The harmonics will change with pressure some.
I don't think it will be as much as people think.
It is based on the speed of sound, when the speed of sound changes so do harmonics but that can only hapen when the density changes.
I have started looking for an air density vs M1.0 relation ship. At this point I don't know if it is liner or exponential. I haven't found crap on it.
Lets say the speed of sound is "a".
Dencity goes up "a" goes down.
So if any thing the turbo intake runners would have to be shorter to time the pressure waves bouncing around at the (new slower) speed of sound so they can be at the vave when it opens.
The speed of sound will be slower, so the intake runners will have to be shorter to make the waves take less time to go up and down the runners.
As you speed up (and build boost) your harmonics pluses will slow down having the effect of making your runners longer, but not realy.
But I don't know by how much.
If you timed your boost right you could stay in the harmonic range for a long time when your at low boost and as you go high boost with more rpms the valve will be opening faster then the boost comes on and changes your "a" so now your in a harmonic range that you could never get to before.
You could maybe do some time in the 4th range and the boost comes on and your in the 2nd range before you know it.
It will get you to a higher harmonic range with a shorter runner.
What you would have is a shorter runner that gives you a harmonic range in a higher rpm and as the boost comes on it will work in a little lower rpm range that it would not n/a. If you can get it to do that.
It would be like haveing a turbo and a super chager that requires no crank power to drive.
It would be a narrow range I think but if you were the other car you would lose.
If some one puts that much thought in there set up do you think you will have a chance?
A lot of people don't think about this becasue they have a mind set of boost owns all.
Like air at sea level some thing moving around 1116 fps will break a.
I didn't go to school and about learn fluidic dynamics so I am left figuring stuff out.
A commeners Ex of fluid dynamics: a compressor map for a turbo.
I have dug up files on the internet about advanced flow dynamics and I have no clue about what I'm looking at. But 3-4 years ago I had no idea what a compressor map was or how to read it.
Just trying to make a car intake with a little jet engine science.
There are people out there that can do this. You don't see it for 2 reasons it's not realy production car applicable and if it's on a (turbo) import pro stock car they will cover up there intake.
If I figure it out I will post it for all to use and read. hahahahaha
You don't find it becasue the same reason you couldn't find any thing about nitrous oxide use on cars in the 60-70's.
It was top ultra secret art of the trade.