SnowmanSteiner

That's true I didn't think about that. One of my concerns is the fact that the intake runner length is defined by how far to the tb so coming up with something that will move to compensate for the throttle body moving is what I am thinking of now. And yes the 787B is an incredible machine.

- Steiner

Scalliwag

Hey I was seeing the pic in your sig earlier but now the closing ] is missing?

SnowmanSteiner

Yeah it was apparently too big, and I don't have time to resize it right now, so I just took the end off the tag so it wouldn't show up, and so it wouldn't **** the mods off . Till be back tomorrow.

- Steiner

Scalliwag

See if this will work

Kenku

Well, like I said, harmonic tuning of intake and exhaust manifolds are comparatively pretty simple. To model anyway... there's all sorts of little fiddly bits having to do with making the things work.

I'm a little bit confused as to what you mean by "coming up with something that will move to compensate for the throttle body moving". IIRC, the throttle slide on the R26B was fixed.

Oh, as another fun thought having to do with the variable manifolds... BMW figured out how to package one into a fairly normal sized assembly on, IIRC, the 7-series. I don't think it would be impossible to borrow their idea...

Scalliwag

SnowmanSteiner

Haha damn I don't even have to do any work. As far as the throttle body issue, from what I read the volume of the intake runners is what matters, so the volume is from the port to the throttle body where it encouters the most resistance, so if you were to change the volume you could shrink the size of the ports, or make a mechanism that slides the throttle body forward or backwards to attain the best volume for a peak hp rpm.

- Steiner

Shamrock.James

yeah i have thought about this but how do you have a throttle body that slides back and forward, I came to the conclusion that you would need to use a valve system with solenoids controlling them..

pp4rotor

actually, just like the 787b is not too dificult.

http://www.mymazdarotary.com/mazda_r...paper_html.htm

one could use either stepper motors or servo motors, would be a pretty simple setup. we are actually working on a system for future formula sae cars similar to this.

Kenku

Well, yeah... the volume from the port to where it encounters the most resistance. The trick is, the Mazda setup uses slide-valve throttle bodies... so at WOT there's effectively no resistance at all. Thus it becomes simple pipe-organ harmonic tuning.

SnowmanSteiner

Well if we get into tuning of the intake pipes, than we could get into the tuning of the RX-8 intake pipes. Mazda has definately been using different ways to find extra horses, and more importantly tune.

- Steiner

Kenku

Well... first off, keep in mind that when I'm talking about "tuning" I'm referring to pressure wave tuning, nothing to do with fuel. Y'might have gotten that anyway, but I wanted to make it clear.

That said, the Renesis doesn't really have any extraordinary tricks with the manifolds; the various ports have different length runners so that pressure wave tuning will give a boost at various RPMs, but aside from being of a far better design, it's not really any more advanced than earlier manifold designs.

The *main* reason the Renesis ends up making more power is because of the side exhaust ports. They reduce misfire rate *DRAMATICIALLY* which means that, among other things, they can get away with larger ports. The intake is actually opening up at 3 degrees ATDC, which is 26 degrees before the old 13Bs were, and 22 degrees earlier than even the RB street port timings listed on Yaw's site. The exhaust port is closed at 3 degrees BTDC, so there's 6 degrees of dwell.

Port area and timing, that simple. It's just that they figured out how to make it idle and pass emissions at the same time.

SnowmanSteiner

What I was talking about was that I read somewhere that the entire intake, not just the runners were harmonically tuned so that at certain rpms the air flowed better due to the sound waves generated in the intake. I believe they have two differnet pipe running from the intake box one is shorter and it switches to the shorter one at a certain rpm, for a shorter path to the intake, and b for the harmonic resonance.

- Steiner

Kenku

Well, yeah. The effect gets smaller and smaller the farther out you go, but the intake tract is tuned like that. Miatas are too, though only at one length... people found that on their own when they took out the crossover pipe type dealie in the front and moved the MAF sensor. Pretty much everyone uses this stuff to one extent or another and have (to one extent or another) since the 60s. Companiest have just gotten better at bothering to do it.

If you think about it, there's all sorts of different things in the entire intake tract for sound waves to reflect off of, and they do... there's all sorts of frequencies the air charge will resonate at, but not all are as strong as others. Where *most* of the tuning you can do with regards to that stuff is in the length of the runners between the port and the plenum; that's the highest energy waves usually. But there's still more so you can set up the next thing in the intake tract to resonate at some frequency or other, which would be the area to the throttle body. And there's still pressure waves going on, so you set up the rest of the intake tract to get just that little bit more, because it's basicially free power.

... but all that bit with harmonic tuning is well understood and relatively simple to optimize.

SnowmanSteiner

Yeah the benefits of the system from the tb back to the air box, is small. And there are much greater responses when you tune from port to the tb. I just think it's neat that they do these little things to try and tune the car very well. While I like the idea of such small ideas like that, a lot of times, say in an actual small business scenario, those things can be a pain if you actually take the time to make small little things like that work, if the benefits of it aren't worth the time that you have to put in.

- Steiner

QuagmireMan

a good healthy bump to remind people of good hard work.

SnowmanSteiner

Damn, I had completely forgot about this thread Good thing it came up though, as I have been having some thoughts as of late... Oh and of course I must add, Scalli you are the man, I can't imagine how many ideas you have floating around up there just waiting to see paper, and better yet, the machine shop.

- Steiner

z8cw

Great threat and great work....I just remembered this threat since my aluminum guy suggested something different for the sleeve you press in for the PP. How about making the hole at the inside housing slightly smaller than the whole throuigh the outside. That will allow you to narrow the tube and create a lip that will rest against the inside housing wall. You can introduce a bevel with an oring and then in case of a semi pp use the manifold that bolds against the outside to push the sleeve in place.

Any thoughts on this would be appreciated.

Thanks
CW

Scalliwag

The problem with that is that the tube ends against a curve. That area of the housing has more curvature than would allow you to machine a flat surface for the bevel on the tube to rest against. It's a lot easier to see the problem with a drilled housing in front of you.
But you could have a threaded or keyed sleeve pressed into the housing and have different sized tubes you could insert into the sleeve.
That would allo you to use the same housing as either a semi or full pp depending on the size of the hole in the tube you inserted.

One huge fear with that is that if the tube you insert is not keyed in some way so that it could not rotate even slightly is that if it was ground flush to the inside of the wall it could turn making part of the insert get struck by an apex seal.
Since the tube is curved at the end it has to remain fixed in order to remain flush. or there will be big trouble in little China.

Turbo1

I havn't read the entire thread, but.

Do you make the hole on the housing undersize a bit, and heat the housing/freeze the tube for a good interfearance fit? Seems like that would be better than just epoxy.

Kenku

Man, this brings back memories. And reminds me that I need to go pull apart the project motor and get started.

Scalliwag

The tube is press fit. You could get real creative and freeze it with liquid nitrogen or dry ice so it would final fit even tighter. Or do that in order to slip it in easy so you could mark the tube for trimming and slip it back out real quick for cutting before it had a chance to expand. Never heat a housing. The risk of warpage far outweighs any benefits I can think of.

After playing with this I have concluded that boring the hole in a bad housing (you need to practice on a bad one the first time anyways) and then open the hole slighty more with a flapper (sanding) disk. Then you could slip the tube into it and mark it for a rough cut to prepare the tubes for the good housings.
You don't want to prep the tube flush in the bad housing because if you don't have it turned just right when you press fit it in and have a low spot
If you press fit these right then pulling one out would be a serious bitch.
You can also turn a few grooves on the outside of the tubes to help the epoxy grab the tube in case your press fit is not tight enough and you do not have a TIG to tack weld it on the outside edge. The tack is overkill anyways but it tends to make people feel better

z8cw

Thanks,
My biggest worry is the seal against the inside housing. My Aluminum specialist is worrried about the housing sleeves expansion vs the aluminum tube vs the rest of the housings. He thinks it will eventually give if not made to move. Does anyone know you the racing beat housings are made and if they hold up?

CW

2a+RoN

sorry i skipped a few pages and didn't see if you had a price for doing the pp work on a housing...

Scalliwag

A standard pport is $150 per housing without epoxy or flush ground. In other words it is boring the hole and making the tube.
After talking to people and getting PM's about pports, this style of pport as far as the homemade version was started in Puerto Rico. But my buddy and biz partner David who is Puerto Rican seems to think this is true as well. That concerns me because David also thinks the Puerto Ricans invented everything from the telephone to ice fishing though so I am not certain enough to label it the "Puerto Rican PPort". What is worse is that his brother Victor says the same thing and he is certifiably full of ****
So I am referring to it as a standard pport. Anything different would be priced according to what was involved.

Paul Yaw used the same pport style. You can find it here http://www.yawpower.com/picture.html and go to pic 25 thru 34. So trying to find good solid answers on where the design started seems to be very elusive.