talent
 

Your upper end IMs look very good. How did you come by the taper. Is there some calc you did for volume per cylinder?

I put a lot of time into designing my plenum shape, with some help from solid works, and those that can use it.

Gotpsi? Any chance you remember my runner length and plenum size? Been getting some interest about the manifold but don't have many answers for them. Anything you can tell me about it would be appreciated :D

Ill have to look at my notes and get back to you but I believe the plenum was in the 160in3 range, and the runners in the 12" I think, it was some time ago now. I'm thinking I made them 6" on that mani plus the centerline of the port in the head length which is what I'm drawing a blank on at the moment.

ME TOO!!!! the stainless makes so many pretty colors...you should try titanium

Sent you a PM!!! :)

So for 6" runners, what torque peak were you building that for, what RPM?

For the plenum volume, do you choose that by engine size or horsepower goal?

Doublepost.

Plenum volume by use, just to generalize, the larger the plenum, the less responsive the engine will be, as a rule of thumb for forced induction the plenum will be 1.5-2x the size of the engine displacment.But will be larger for crazy HP applications. Runner length is a bit more complicated, especially for N/A applications. Shorter runners will allow the engine to still be efficient at high rpm when off boost, and less restrictive anywhere in the rpm range when in boost. I have all the specs of that mani written down I just have to find them for specifics.

Ok so I looked into my notes, with the runner length on that mani its set up to make torque up to 8k, peak torque depends on when your turbo spools and takes over the wave affect in the runners and plenum, so you will see gains as soon as you are 100kpa+ and will build power to redline from there, the only limiting factors are the cams you are running. Also with the way I set up the plenum and the throttle body, the throttle response should be just as good as a stock mani, and should help spool with good tunning.

The reason I ask about 6" runners is that I /think/ that's the exact length Brain had and then ditched because the powerband was moved up way too high.

That manifold was built for a different head, different length runner. I can make them as long as you want, that is just one of the ones I have built. My mani has even shorter runners but it is track only, and is only ever below 4k when I'm in the pits.

Right, but even with a turbo, you adjust the runner length inversely to your target torque peak, correct?

Or are you saying that shorter runners just increase response at the cost of N/A drivability, the shorter the better when turboed?

For instance... if you had an N/A engine with a desired torque peak of about 6200 rpm, and a turbo engine with the same desired torque peak, would you use the same length runners?

Or are you saying that shorter runners just increase response at the cost of N/A drivability, the shorter the better when turboed? shorter is usually better with a turbo.

For instance... if you had an N/A engine with a desired torque peak of about 6200 rpm, and a turbo engine with the same desired torque peak, would you use the same length runners? It would depend on your turbo, if you want response for the street short runners and a small turbo would be great, if you want big power you want short runners and a big turbo, if you want a big turbo and better response than overall power than long runners are better. In your case since your turbo is not huge and its a street car you would be best suited somewhere in the middle.[/QUOTE]

I really hate to sound like a tard, but here it goes... Gotpsi. You are saying that you must create over 100kpa (14+psi) to overcome the wave effect that is being generated by the cycling intake.
Two questions. If you never go above 14 pounds of boost will you ever take over the wave effect? If that is true all the people running 5, 6, or even 10 psi will never overcome the surgeing of the on/off of the intake valve...

Question two. Man your engine is the bomb, torque up to 8k. How high does it rev?

No, he's saying the manifold he built for FRT_Fun was setup to have torque to 8k...

Also throttle body size will also affect response which is why you need to go bigger with a large plenum, because your off boost throttle changes may lag if the throttle body is to small, making for an annoying stumble or laggy turbo, even if you are at high rpm before you open it up.

100 kpa is 0 psi, anything over that will overcome the waves.

Just thought I would though some pics up of some of the newer manifolds that have been done w/ tapering runners.

[IMG]https://www.miataturbo.net/attachmen...ine=1330197063[/IMG]

[IMG]https://www.miataturbo.net/attachmen...ine=1330197063[/IMG]

[IMG]https://www.miataturbo.net/attachmen...ine=1330197063[/IMG]

[IMG]http://i391.photobucket.com/albums/o...x/IMAG0285.jpg[/IMG]




Also doing them with flush runners for those that want it.
[IMG]https://www.miataturbo.net/attachmen...ine=1330197063[/IMG]

Can't wait to see how that one does. When does it ship?