^NoDOHC

Makes perfect sense to me and helps solidfy what seemed logical in concept. Explaining it in terms of energy spent follows right along with what I was thinking.

My thoughts were that if you suddenly give pressurized air MORE space it's going to create "turbulance" as it expands. Then when the chamber/runner constricts back down it requires more energy to press the air back into the smaller area. You're pressing the air against an angled surface and the suspended fuel is going to hit the side and come out of suspension.

That scenario seems equally damaging to the process as having a lip exposed.

The issue that we have with your runners is that we have to worry about both fuel suspension and air flow. The good news is that changes in area and steps will both hurt both.

I wish that I had dyno'ed my engine before the intake maifold modification, but I am reasonably sure that it helped.

I think, at this point, that you're over-thinking the whole thing.
The stock intake manifold system SUCKS.
Any mods to help flow will get you gains.


-Ted

Agreed..... to a certain extent...
Smooth transitions are key. I had to open up the RE mani's to the point where I had to cut the gasket. To make sure they were always the same, I built a template out of some 1/4" AL so that I can quickly and accurately trim the gaskets. I then smoothed the runners and tapered them as much as possible. This was on the UIM to LIM. The LIM to the block was closer, but still a little off.

Just poking my nose in here for a second but what about reversion? Isn't that
supposed to be preserved when porting the intakes on a rotary?

That's port timing, not port matching

It's definately a good discussion to have but it's a whole different can of worms that's been opened a few times before. However, you're right, and it should be preserved. It's one of the reasons I believe that when it comes to port timing, less is more when porting. For example, I never touch the closing of the exhaust or the opening of the intake......

Definitely true about over thinking. In one of my threads I posted that I'm disturbingly perfectionist and I loose sleep over tiny details. Perfect example right here.

It's the little details that make an entire package perform at it's peak.

Take mine for example ;)

And FWIW, I'm an OCD perfectionist as well.

Cool thread. I have occasional access to a flow bench if people are interested in before/after testing or comparisons. There are some rough assumptions that must be made: mainly that the engine doesn't suck a smooth steady stream of air like the pump in the flowbench, there are quick pressure (vacuum) fluctuations as the engine 'gulps' air in while the intake ports are open. It will probably be a while before I get around to testing intake manifold porting or modifications on my car, but if anyone local wants to stop by and measure their setup(s) feel free to send a PM.