Cool intake manifold project pictures...

[Cross]

Originally Posted by KING6

with a manifold like that who needs a hood.

Hell yeah! Or just cut a hole and keep that baby really cool lol.

Hey I got an idea, I think it should look like King's cover he has over his IM. Build it with that look in mind and possibly if need be functional. It will be tight right there, my idea's always started with cutting them off before the bend I just never thought to use too fronts... dumb me lol.

Either way I am pretty sure he will work it out. I want to see the TB mounting he has in mind compared to my idea lol.

[reuben_johnston]

guys,

there is about 3" of height, maybe 3.5" from the top of the injectors to the hood. thus the height i picked @ 3".

Below are pictures of the throttle body, flange, and an estimate of the placement viewed from above. The throttle body will be down a little lower than the manifold.

[Cross]

Ahh the mustangniss is killing me. lol

I like it as I said I can't wait to see it done.

[Car-InsanE]

this is going to be so freaking cool

[KING6]

so your using 2 of the fpr side of the rails that require the adapter fitting?...

Couldnt you use the other 2, to eliminate that fitting.

Also, are you able to flip the runners around so that they are facing out instead of in.
possibly could do a dual manifold type deal with dual tbs?...
id like to see a pic of that just to see the clearnces..

I have an IM i have half chopped already.. still trying to think of the best setup, I was going to do something like micis new manifold...

[mx_masta]

I know that this is not my forum section but.
A good rule of thumb with intake plenums is that you want at least as much internal volume as engine displacment. Which means that most OEM plenums are way too small.

The reason you want plenty of internal volume as it acts as a reserve of air so that on each intake stroke there is a full charge in the plenum for the cylinder to draw from.
Having too small of a plenum hurts top end power as there is less time to fill that plenum no matter what the size of it. This causes the manifold preasure to drop higher in the rev range costing you power.

I know that this may seem accedemic with a forced induction vehicle. But it will still cost you power at higher revs just not as noticable as a N/A car.

I guestimated that your plenum at about 16 inches long would be about 1.25 litres in volume which would be about the standard plenum volume on a 1.5 litre car.

Ever driven a 1.5 litre car with a vacuum gauge and noticed the needle move off of 0 VAC at WOT me too. It costs the engine power. Now imagine that on a 2.5 or 3 litre engine.

I would keep maximising internal volume in mind if I were you. Though I realise there are of lot of other deign considerations too.

[reuben_johnston]

Originally Posted by KING6

so your using 2 of the fpr side of the rails that require the adapter fitting?...

Couldnt you use the other 2, to eliminate that fitting.

Also, are you able to flip the runners around so that they are facing out instead of in.
possibly could do a dual manifold type deal with dual tbs?...
id like to see a pic of that just to see the clearnces..

I have an IM i have half chopped already.. still trying to think of the best setup, I was going to do something like micis new manifold...

hey king,

i tried that, the fuel rail mounts are not compatible with the other two. i had hoped they would be. that is correct, will need two of the adaptor fittings.

i don't think we can flip the runners to face out.

reuben

[reuben_johnston]

Originally Posted by mx_masta

I know that this is not my forum section but.
A good rule of thumb with intake plenums is that you want at least as much internal volume as engine displacment. Which means that most OEM plenums are way too small.

The reason you want plenty of internal volume as it acts as a reserve of air so that on each intake stroke there is a full charge in the plenum for the cylinder to draw from.
Having too small of a plenum hurts top end power as there is less time to fill that plenum no matter what the size of it. This causes the manifold preasure to drop higher in the rev range costing you power.

I know that this may seem accedemic with a forced induction vehicle. But it will still cost you power at higher revs just not as noticable as a N/A car.

I guestimated that your plenum at about 16 inches long would be about 1.25 litres in volume which would be about the standard plenum volume on a 1.5 litre car.

Ever driven a 1.5 litre car with a vacuum gauge and noticed the needle move off of 0 VAC at WOT me too. It costs the engine power. Now imagine that on a 2.5 or 3 litre engine.

I would keep maximising internal volume in mind if I were you. Though I realise there are of lot of other deign considerations too.

mx_masta,

here are my thoughts on that comment. assuming the throttle body is large enough the plenum fills in time, don't we need only need enough in the plenum for one cylinder firing? for a 4 cyl, you would need enough to fill two cylinders, but we're only firing one at a time. corky bell states 50-70% of the engine displacement for the plenum volume, as a rule of thumb. this design is about 47%. may need to grow it some, that just makes fabrication quite more difficult.

reuben

[mx_masta]

Yeah the throttle body size does help but you definitely want as much plenum volume as you can.
Think of it this way the plenum has 2 jobs:-
1. to distribute the a/f charge to the cylinders.
2. to act as an air spring of sorts to ensure that the charge in the plenum is even along its length and each cylinder get a fair share.
Remember any engine is limited by it's worst cylinder.
The point is you dont want to be drawing that charge from the intake it should already be there in the plenum.
Example - 3 litre v10 Ferrari engine, one of the best developed production engines in the world has like a 6 litre plenum.

[Nealio]

Originally Posted by reuben_johnston

mx_masta,

here are my thoughts on that comment. assuming the throttle body is large enough the plenum fills in time, don't we need only need enough in the plenum for one cylinder firing? for a 4 cyl, you would need enough to fill two cylinders, but we're only firing one at a time. corky bell states 50-70% of the engine displacement for the plenum volume, as a rule of thumb. this design is about 47%. may need to grow it some, that just makes fabrication quite more difficult.

reuben

Well if volume is the only issue, won't it be easy enough to just make the entire plenum wider? You should have enough space to expand in those directions.

[easyBob]

I like what you did with the IM runners (using two fronts). I don't think, however, that the 'box' design you drew up will bring you any gains over the stock IM, even when boosting. There is a lot more to IM design than just the volume, as Nealio stated.

God, I wish I could remember, but I know there are some more in-depth books/sources on manifold design.

I'll post them if I can find them,
-Chris

[mx_masta]

Plenum volume definitely isn't the only issue.
Runner length and volume are very important in determining where in the rpm range the engine will make peak torque.
Worst case senario would be to make the runners so short that the manifold resonant frequency is outside of the engines rpm limit.

[mx_masta]

Just so I'm not being picky for the sake of it.
Here is a quick sketch of how I see your best option with the current runner length.



You would of course have to cut the runners off square to the runner rather than the plenum centreline as you have now.
But that shouldn't change the inlet characteristics too much from where you are now. It would be a very minimal change to effective length (measured at the centre of the port.)

And would get you a lot more plenum volume.
Sure it would be harded to make 'cos you would need to use plate instead of tube.
But your'e going to all of this effort, may as well do it the better rather than the easy way.

[reuben_johnston]

Originally Posted by mx_masta

Just so I'm not being picky for the sake of it.
Here is a quick sketch of how I see your best option with the current runner length.


You would of course have to cut the runners off square to the runner rather than the plenum centreline as you have now.
But that shouldn't change the inlet characteristics too much from where you are now. It would be a very minimal change to effective length (measured at the centre of the port.)

And would get you a lot more plenum volume.
Sure it would be harded to make 'cos you would need to use plate instead of tube.
But your'e going to all of this effort, may as well do it the better rather than the easy way.

i agree, here are some rough calcs (my trig is rusty):

isosceles trapezoid in shape: a=2", b=4", h=3" (50.8mm^2, 101.6mm^2, 76.2mm^2)
A=((a+b)*h)/2=5806.44 mm^2
length is 12" (304.8mm^2)
V=A*L=1769802mm^3=1770cm^3=1.77L
plenum volume vs. displacement %=1.77L/2.5L=70.8%
calculations for angle to cut runners:
tan(x)=3/1:x=71.56 degrees (measured counterclockwise from base of firewall side flanges, viewing from driver side perspective)

machine shop will love me with these cut specs

reuben

[mx_masta]

I wouldn't bother with the machine shop for the moment.
Much better to mock something up first with whatever. To make sure the hood will close, etc.

I assume you will be making this out of alli so that it can be welded to the cut runners.
Why not do the cutting yourself? Even 5mm alluminium sheet cuts like butter.
Once you have the mock up done you should be able to cut the pieces out yourself without too much wastage.

Don't know if you can tig weld but if not you could tack it together with alli brazing rod.
And them get it tigged by someone else.
Motorbike wreckers / repairers are a good bet for small jobs as the bike frames are often made of alluminium.

Or if your lucky like me you could get it done for a six pack at work.