4x4Wire's TrailTalk Forums: The 3.0 build-up thread.

I know that this has been beatin to death but this is what I posted on yotatech and it pretty well sums up where I'm at with the plenum design so far.

I know that the Downey extrude honed plenum dynoed at 8hp on a stock setup. I think with an extra 1/8 of diameter in the runners, longer runners and single directional flow plenum I can get more then that and increase the milage by reducing all the turbulance in the air flow.

Here's the simple version of how I see the plenum working as is.

1. Air comes in the 53mm TB at WOT. 53mm is small but maybe not too small for the 3.0, we do know that a 3 mm OB does have an effect at WOT probably because that increases the size to almost match the 59mm - (size of egr pipe) intake tube.

2. air travels down the ~57/58mm intake tube which isn't all that smooth but we'll say that thats OK for now.

3. Air hits the back of the wall of the chamber causing disruption and a posative pressure area in th center of the chamber which is smaller (I haven't measured yet but you can see by just looking at it)then the combined dia of the intake runners forget their volume.

4. Air moves from the smaller chamber where it is turbulant and enters the 35mm runners which are larger then the chamber meaning that already turbulant air looses velocity and thus momentum increasing the turbulance and further decreasing the momentum needed to make lower end power. Keep in mind that the rough cast sides of the runners are now adding to the drag because the air is so turbulant, this effectively makes the runners more constrictive.

5. Air comes into the 38mm lower intake runners which are larger then the upper once again loosing velocity and thus momentum then it gets the fuel and...

6. Then the air hits the small ports and valves of the head (this is another discussion altogether though).

An ideal intake is supposed to get smaller from the begining of the runner to valve and this one is the opposite. Look at some pics it is completely different from the 3vzfe (TB size?) and very very different from the 5vzfe(TB size?) which I would say is a very good design for a truck. The 5vz has longer runners to create the momentum needed for lower end power and is all uniform directional flow. I would even bet that all those guys who are putting 5vzfe engines in things like MR2s would benefit from the 3vzfe style intake over the 5vzfe one.

I think Toyota just made some simple mistakes with the plenum design likely cause it was their first kick at the cat and they needed something that would work more then they needed something that would work well. In the end they offered the market an engine that has more power then the 22re and didn't make so much power that it called too much attention to itself as they drew off market share from the domestic companies.

For mine I plan of using an altogether larger TB, larger intake tube as close to 70mm as I can with a larger(not quite sure of exact size yet) plenum and larger(38mm), longer(by about 2"-3") runners.

Kinda like this:

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(aka suprathepeg, aka Sean)
89 v6 SWB truck "BLACK BEAUTY" EB valves, P&P head 30 over.
95 FZJ80. Lifted. locked and rollin on 33s (my dream machine)

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