dual plenum part two.....

[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.

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[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.

[IanSzgatti]

and have the presure waves arive at the back of the valve just before it opens.

jesus h christ... and im still waiting to install a CAI. Anyways, thanks for that.

[merlot566jka]

dont wait, dive in and learn. take hold and control what you want to know. youd be suprised how fast youll learn, (and how fast you spend money)

[silvergtjrad]

dont wait, dive in and learn. take hold and control what you want to know. youd be suprised how fast youll learn, (and how fast you spend money)

Amen. I went from doing oil changes to building an engine. Also went from spending $100 every few months, to at least $100 every few weeks.

[IanSzgatti]

Amen. I went from doing oil changes to building an engine. Also went from spending $100 every few months, to at least $100 every few weeks.

well i went from changing my oil to going to college and completing at least my level one ASE certification. I'm now working in an independent shop where I get all the nice shity jobs.

at any rate, there is so much in the way of theory here you guys toss around that is outside the realm of 'normal' day to day automotive service. Even though im wrenching everyday, scanning OBD, etc, it's still not to boost the performance of an engine.

You guys have an understanding of things here that my co-worker would never be able to answer too. In fact, when I told him how I'd love to swap a 3400 into my malibu, and start modifying it from there... he balked and told me it's a waste of time... I'm wondering why he can't see the potential, but then again, the only thing he knows how to find online are boobs. (of which I am a fan of).
So, I love whats happening here, and appreciate the encouragement. also, sorry for being a windbag in your thread.

[IsaacHayes]

What would be considered small plenum vs large TB and vise versa?

Like a 3500 plenum and a small port 3100 TB? (52mm)
Or a 3100 small port plenum and a 65mm tb?

I had a 56mm on the 3500 plenum and it did pretty good. The 52 seems about the same maybe worse. I do seem to lack power in the high RPM compared to lower RPM, but that is probably because I still have the stock exhaust on. I should have better high RPM power than before because I went from small plenum, small long runner, to larger shorter runner and big plenum. The car is faster though. Just choking on the high RPM.

I will find out soon if it's choking because of the TB or exhaust. I'm getting a 62mm TB any day now. If it doesn't help in the upper RPM I know it's the exhaust (which will be fixed soon). And then I can test the TB's again.

I usually go by TB size by the amount of power the engine is making/capable of. 52mm is pretty limiting. A good idea is to look at other factory engines making the power yours will be making and see what TB size they have. But not all are a good example though. Some have huge TB's compared to the power they make. I haven't really seen any high power motors with tiny TB's on the other hand.