Fins on back of Valve & Fins pre TB

[The1]

Biggest problem with V8 with split plenum is the uneven firing order bank to bank, it doesn't go LRLRLRLR but RLRRLRLL, the v6 however should be good as it does fire LRLRLR so can be easy split up as shown in the earlier manifolds in this post.
Like with all engine design the package of parts needs to work together, no point having an intake manifold with short runners designed for high rpm work and then fitting a tow cam.
This is the reason for variable intake manifold design so the engine can swap from long runners at low rpm to short runners at high rpm. If you could come up with a robust design that sealed well, reacted quickly and could infinitely vary the length of the runners could improve the torque spread across the engine range. The same applies for exhaust, was tried by Yamaha on there motorcycles with the EXUP system.
http://www.yamaha-motor.com.au/service- ... nology/EXU
Have never seen this system fitted to a car, but is no reason I can see that it wouldn't work if tuned to work with the engine rpm, capacity and header length, could even drive it using a 12p flex table

BMW has been doing it for years i think, xforce also has valves in some of there mufflers.

[HQ355]

Some HSV's and fpr's have valves in the mufflers as well, there vacuum operated, mainly to keep them quiet when idling around but noisy when you want them to be

[Gareth]

Bi-modal??

http://www.xforce.com.au/products/varex-mufflers fitted these and sound great

[vlad01]

some time ago at a restaurant in syndey was a real Ferrari V8 engine on a stand.

it had a real interesting intake design. It had 2 separate plenums that tapered down smaller as it got to the rear. The plenums had a bridge across the 2 with a vac operated butterfly between. So I guess they either open or close depending on engine load?

this was it.




another design. Looks to have 2 different length runners per port?

[vlad01]

ahh i know how these work now!




the plates stay closed in the pic above at low rpms whilst the plenum TB are feeding the already open longer crossed over runners. high rpm comes in and the plates int he pic open basically shortening the runners.

Also makes sense the longer ones are small diameter and the shorter larger

top stuff Ferrari

[Gareth]

Top find Vlad

now just to make it fit ecotec...

[vlad01]

thats it!

The1, hurry up, print us one of these please!

[yoda69]

Bi-modal systems I've looked at are typically for noise, they don't vary the length basically bypass the muffler to give a deeper throatier sound.
The Ferrari intake looks interesting, looks like what is done on some inter cooler tanks that are tapered. The idea is to keep the air speed the same throughout. At the plenum opening need enough air for the 4 cylinders, then as it progresses down for 3, then 2 and finally one. The same type of thing is done with commercial building air conditioning systems except they are noticeably stepped to smaller and smaller tubes as you get closer to the end of the system.

[Holden202T]

Thanks for the pics holden 202t, how many killer wasps did the motor make ?

yeah that's part of the issue, he never finished it so no dyno, he did however put the motor into a VH commodore with T400 and e85 carby and it had 328hp at wheels.

on the subject of variable intake manifolds, this is exactly what the Alloytec 190kw motor has in the back of it, a flap to make it dual/single plane .... certainly has more high rpm pull than the 175kw version .... but that could be partly the 4 cam adjustment as apposed to 2 on the 175.

[Gareth]

Holden call it 'VIM' or variable intake manifold, when you do a service update on a series one VE you have to fit 'VIM amp rework kit' that adds an amplifier to the VIM actuator signal, C#nt of a job...