dual plenum part two.....

[merlot566jka]

so the last plenum had a vacuum chamber that shared the vacuum between both plenums. the problem is that the iac fed into this chamber, and when the iac opened it was jacking up the map values and the iac would just keep opening more and more, untill the vacuum looked right for an idle....the end result was a 2500rpm idle.

to fix this, im making a whole new plenum. in this the vacuum will come from a combined chamber of both plenums. the iac will feed into a seperate chamber where there will be an individual tubes going to each velocity stack. here is a paint diagram....


and when my camera decides to load ill show you the pics of my new supplies

[merlot566jka]

[IsaacHayes]

Actually, they way you have the picture you should use that for IAC/everything no problem. My guess the last plenum had a leak or the MAP was only reading one side.

The MAP and brake booster need strong vacuum that's not shared with anything.

If the TB you are using does not have a built in IAC, then running an external one that feeds both sides is recommended.

If you are going custom I'd keep the plenum's seperate with the TB blades. Then just make a connection on the back/center of each plenum with a T that goes to the brake booster, and another for MAP farther away from that one, then a smaller one for whatever else like FPR.

[merlot566jka]

it has an iac in the tb, but the problem is getting it to feed both plenums equally.
the map was feeding off the same chamber that fed everything else. in other words it didnt get acurate readings.

i see what your saying there, make it true dual plenums and then run a connection between the two for the map, one for the brake booster and one for fpr and one for pcv

[IsaacHayes]

http://www.mez.co.uk/ms12.html

I just found that, haven't looked at it all that much but has some cool stuff I thought you might get some ideas from maybe?

[merlot566jka]

interesting! i havent seen that site yet.

heres what i got most of my ideas from

http://www.discovery-automotive.com/projects/kolar/DSC01633.jpg

http://www.928developments.com/manifold1.gif

http://www.gtr.co.uk/forum/upload/69...l-plenium.html

[Superdave]

you should do something like this...

[torq455]

i know what that's from!!!!!! mmmmhmmhmmm!

[Ortie666]

Thats one of twm's injection systems on that manifold, it has the same flange faces as a set of tripple barrel webers.. I have been trying to find a cheaper set of the webers or zenith's for a couple of years now.. I had that plan after I built my first manifold, little did I know thay actualy made them..

[Ortie666]

First manifold.. wasnt too great.. had a real stiff 3000rpm powerband, not too streetable especialy in a 1900lb car

[bszopi]

Its kind of slow at work today, so I played some on the side...



I'm still playing with it, but I think that gives you an idea of what Isaac was talking about.

[merlot566jka]

ah i c,

im too lazy to draw mine up all the way. im more of a 'fab as you go' type of person. i dont like to put too much pre-planning into it. i like it all infront of me and hands on to make it work

[IsaacHayes]

A good design though is something to take your time with. Unless you just like having lots of different prototypes lying around!

[IanSzgatti]

is there an ideal plenum volume you'd like to see relative to total combustion chamber volume?

[merlot566jka]

grapeaperacing.com

youll find the info youre after above. for my set up im looking for power in the 6800 rpm range. with that and dual plenum im looking at 70-80 cubic inch plenums. the 3500 plenum is well over 3000cc. with large plenums, a smaller tb works well and with smaller plenums, larger tbs work well. realitive small and large...nothing extreme. usualy plenums are a funtion of the cylinders they feed, in that of a percentage. smaller plenum is good for low end and large plenums are good for high end. when you get into the helmholtz resonators, plenum volume gets funky. that is my over all goal with the dual plenums, to take advantage of the helmholtz resonator and have the presure waves arive at the back of the valve just before it opens.