Divided Plenum Manifold HOW-TO

Ok here we go,

First of all this manifold is a bit/alot of a compromise, I would much rather have a split manifold with looong 10 15 or even 20 inch runners hanging out over each rocker cover with a throttle body on each plenum, then My VN would be straight in the 14 second bracket with no other modifications but that's a big job.

So since a proper tuned manifold like that is hard to come by, I thought might as well try a simple divider first, worst case is I'll gain some low speed torque and loose a bit on the top end and if It doesn't make alot of difference I'll cut the whole top off the manifold and start making that proper tuned design I talked about at first : ).

Ok here's how to make a divided manifold

Picture 1.

This is the aftermath of me going sick with a common angle grinder with a thin cutoff wheel attached, I cut straight along the top of the manifold and down the front as far as I could go without cutting into the base of the manifold. (be careful and use your glasses) also use a can of spray on canola cooking oil to help cut alloy : ) helps with die grinding the stuff anyway.

Picture 2.

Same thing from the back.

Picture 3.

This is the bit of cardboard I used for a template, bit of scissor work to get it just right but this goes with the manifold to the engineers (today) so he can cut a sheet of aluminium the same size and weld the manifold back together for me

Picture 4.

Template installed.

Picture 5.

Again from the front.


Also I will be making a divider for the bend so it's divided all the way up the the throttle body just to see what effect that has. With and without it. (I saw an aftermarket mustang manifold like that and it made lots more power)

That's it : ) now I just need to get it welded up and some gaskets, I hope to have it on the car on the weekend or if not then sometime next week. I've also done some porting in the runners around where the injector plugs in because there was some nasty over engineering there so I got rid of some of the casting. The saga will continue later : )

 

It's only along one side I just got bored and need a break while smooth the ports and I happened to have the die grinder in my hand allready so... FOAM it was. I'll be painting the manifold black and the fuel rails and alloy water hose may well be polished. FOAM will be lime green, it'll look fast even if it's not

 

It's all a bit complicated how this is supposed to work but I've done a million simulations and depending on the software it can gain huge torque everywhere or a little on the bottom end or a decent amount on the bottom and loose on the top. I'm thinking I'll gain 15nm on the bottom end and loose 7 or so through the top end but that's worst case : ) it could suprise me. It's such an easy thing to try I couldn't resist. If you stare at the firing order long enough you can imagine the pulses with the divider in there helping quite a bit but then again I could just have a good imagination. I'm placing alot of trust in David Vizard master engine building because he keeps saying how well V6's respond to being split in half and run as two seperate engines. I probably should also have this dudes book but I don't :/

http://www.themotorbookstore.com/scdeofexinsy.html

The long runner manifold yes that would be 100% certain to make huge torque and power increases right across the rev range but yeah, very complicated to weld up

 

Why has this got a sticky before it's tested ?

 

Not yet mate been busy at work again and with all these holidays I haven't wanted to go disturbing the engineer, I should take it there on Wednesday I think to get welded but I carry the manifold in my boot everyday, just incase I'm going past there at the right time . I've thought of a way to make a proper long runner manifold but I don't know anyplace near me that sells aluminium tubing and pipe

Here's a picture of the basic design but in real life it would have even longer runners and a throttle body and CAI ducting from either the front or rear of each plenum tube, something like that should dump a decent VN V6 with a good exhaust straight under 15 seconds on the quarter mile

 

geta, no guessing I know exactly how long and the area the runners need to be, I have plenty of engine design programs. I'll try and find some pictures of this walker manifold.

I was talking to the engineer today about getting my manifold welded, he cut me a bit of aluminium with his plasma cutter (man that's a cool invention! I was a little worried about what it might do to your fingers?. Anyway he suggested I cut right through the bottom of the manifold and make a key in the divider so it slots through the bottom and then he can weld it easily just about all the way around.

I went to my dads shed and finished the divider and it was such a good fit I had to tap it into place with a hammer and no light shines past the divider anywhere, masterpiece! : ) It's getting welded up on Friday I'll get some gaskets and should have it on the car next week, I'll get another picture of it before it's welded then one when its welded and another when it's painted black . The engineers Cobra is looking good, has a BA Boss V8 motor in it and he just bought a manual box for that also he's getting a capa super charger for it and aiming for 550kw at the wheels. I don't think I'll want to take a ride in a sub 1000kg car with that much power .

He also said the a long runner tuned manifold would be pretty easy to make using aluminium pipe and bending it with sand inside, he reckons you can make all sorts of crazy stuff with it