Installer88

iTrader: (3)

So I have a few questions on intake manifold design. First, the car is an IS300 with a 4g63, so an off the shelf manifold will not work. I took an oem 1g eclipse manifold (due to larger runners). Then I cut off the plenum, and made a 13" x 3" plate and cut out the ports and am welding it to the runners. Then I have some 6" od aluminum that I am planning to cut out 3" length wise, and weld it into the plate. The runners are 8.5" long, and overall plenum volume should be around 300 cubic inches based on the inner diameter and overall length.

The questions I have are: how much taper should there be in the plenum, and how should I make the endplate shaped (flat, angled, or make it come to a point)? I know this will not be perfect due to not having a flowbench to test it, but I am wanting to make it as good as I can. This is my first manifold I am making, so I am not so sure about those designs. As far as stuff in the engine bay, it is very open, so there is nothing around that area.

Here are the pics

Installer88

iTrader: (3)

And here is a pic of the current engine bay, the car is getting floor mount pedals, so no brake booster will be in the way.

Installer88

iTrader: (3)

Plenum material has arrived.



Here is with 3.5" cut out of the bottom so I can weld it together.


What do you think about following this line to make the back go down approx 1"?



Then following this line too?


What do you guys think?

R/TErnie

iTrader: (32)

work on your velocity stack area... you're going to need a SERIOUS amount of radius on those inlets.

This means a LOT of welding prior to putting the plenum on.

Runner length is too long IMO. Curved runners = Fail.

You might want to taper the plenum from the 1st runner to the last as well. I can show you later.

Installer88

iTrader: (3)

I am working on making the runner to plenum section have more radius. It is hard to see in the pics I took, but I rounded them before welding, and I plan on rounding them again. I figured the longer runners will help with low end torque, the engine is a 2.3 stroker, so it won't rev super high. The plan is to finish the runners while I am figuring out how I want to make the plenum. I just cut it so it would be easier for everyone to see what I have in mind. As far as the taper, like the line I have in the third pic, or more?

SmurfZilla

iTrader: (33)

I think you're one crazy sum*****

Installer88

iTrader: (3)

I started making the velocity stacks. I need to add more material in some areas to make it even. But here is a pic.

R/TErnie

iTrader: (32)

Those aren't really velocity stacks, but more of a radiused entry.

Make the radius 4 times larger than what you have

Installer88

iTrader: (3)

How much of a differance do you think the radius I have vs making it 4 times larger will be? If I have to add a lot of material on the backside, I will have to cut the manifold to get the welder in there. On the inside edges, I can only weld them throgh the top.

Installer88

iTrader: (3)

R/TErnie thank you for the help. But, what would do between the runners? There is only 1/8" of material between each runner to work with.

R/TErnie

iTrader: (32)

just radius between the runners what you can. Don't knife edge it. Everything else should be a large diameter.

From what you have... to what I'm telling you... I would say 5% gains in actual power.

Installer88

iTrader: (3)

So I made the runner to plenum radius as large as I could without a ton more welding and grinding. I will take pics of that later.

I started modifying the plenum to have cyl. 4 smaller than cyl. 1. I welded the parts I removed onto the bottom, but just tacked everything else. I will take some measurements to see if I want to stick with thos idea.

03whitegsr

iTrader: (8)

Ported Evo manifold + ported 2G head...

That's the direction I would go on that setup.

The 1G runners have virtually no taper to them, so the length with the bend in there is going to hurt power. I'm generally a fan of longer runners, but only if they are fairly straight on path and tapered on the cross-section.

Installer88

iTrader: (3)

The evo flange is wrong, so I would have to cut off a dsm flange, and weld it to the evo manifold.

03whitegsr

iTrader: (8)

You sure it wouldn't just take cutting the EGR section off the manifold and tapping the EGR port for a plug in the head?

Or is the port size/position that different?