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

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

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 piss the mods off:D . Till be back tomorrow.

- Steiner

See if this will work

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... :cool:

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

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..

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.

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.

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

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.

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

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.

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

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

Damn, I had completely forgot about this thread :sad: 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

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

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. :eek: or there will be big trouble in little China.

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.

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

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 :eek:
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 :)

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

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

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 shit :)
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.

damnit, scalli, every time i get caught up with the club and full of enough rotary stuff to satisfy me for a week or two of homework, i find another one of your threads.

I have considered the semi-pp idea for a while...maybe on my next engine... but i had never thought of 'adjustable' ones like you.

My input is this: I'm an on-the-fly type of guy. with a little bit of extra ingenuity and some solenoids (i already have a basic design in the ol' rattlebox) you could make 'automatic' chokes. What i would do is wire them up to the aux output on the Microtech, so that when you switch maps they are automatically opened. In other words... you are sitting at a stop light, an enzo pulls up next to you, you grab the laptop, fugg with it for a sec, wait 15 secs for it to load, and then kick his ass! then switch back and get 20 mpg again without ever getting out of the car.

Damn...im gonna be thinking about this for a week...I have exams coming up, too.

pat

The way I understand it is that the Microtechs dash unit will store 3 maps so you can change them on the fly. So if you did get a solenoid system working and tuned you could have a dual stage semi pport where you could get a good road race setup going on the first stage and for drag you could have a second stage of pports actuate.
I am not sure how you would run all of that but it will give you more to think about ;)

i use the laptop, so i can store at least 4...maybe more. 2 would be all you need tho. as far as on-the-fly, it takes 30 seconds or so to change between them with the laptop, not sure if that is any different witht the dash or not.
I just didnt like your idea about taking it apart and removing the sleeve....or at least thats how i understood it.... seems like there are much easier ways to restrict it that could be remotely controlled with the flip of a switch or push of a button.

Theoretically, you could tune the microtech so that no map change was even necessary, but that would be dumb. However, heres my latest idea:

Set it up with an infinitely variable p-port opening. Have it closed at idle, and then use a seperate injector and controller...maybe modified mega-squirt.. to adjust for just the p-port in real time, so that you can turn it off...and just have the port all the way closed, or turn it on and have it open as a function of load or RPM... giving you more low-end torque and then a gradually increasing power curve. Once you figured out the changes it made, ie how much fuel needed added, whether timing needs to be modified, etc, it would be relatively simple to set up a controller and program it. Every time I think about it, I like that idea more and more.... If only i won the lottery....

anyway, my next engine might see something like this...

I guess I'm just crazy for wanting to run a full fledged pp on the street. Oh well I've never really cared for the amenities of ac/heat/ps/carpet etc in my car.

- Steiner

This type of set up has been ran for years, many of the 24hour endurance cars back in the late 70s and early 80s ran this.....no problems....lots of abuse!!! :bigthumb:

Yes you read right but there is a method to the madness there. The modular manifold system I want has to be changed radically for street and strip. With the big honkin pport tubes you have an insane amount of port timing for street.
With well made insert tubes you could taper the port timing and make it much more street friendly.
Another thing is that for street use I would want the manifold to wrap over the top of the motor to get some runner length and the throttle body would be set as side draft.
But when it came time to race it then it would all come apart by set screws and o-rings. The throttle body for racing then would be setup as downdraft like you see on Scheepers setup. You would just need to remember to switch the maps.
The inserts are the only way I know of to be able to control the port timing. I would want something that was truly livable on the street but could switch to a very radical mammajamma at the track.

It would be a blast to setup :)

"radical mammajamma "

The problem is though, you can't *really* control port timing with sleeves like that, for reasonable levels of fabrication. Even if you restrict the pport runner down to, (pulling numbers out of thin air) 30mm instead of 48mm, the bit cut out of the chromed iron determines when it's open. I don't *think* you're going to try to make the sleeves that close of tolerances are you? ;)

... OTOH, in reality as long as you're close, there won't be *that* much difference. And even if you left quite a bit of room, the choke inserts expanding out to port size may help fight reversion.

That is what I would plan on. Getting the insert as close as what is safely possible. We are working on buying a cryo system for the shop next year. If this ever did come to fruition we could make the tolerances on the inserts incredibly tight and cryo them so that there would be no thermal expansion.
But like you say as long as you are close the timing effect would be whatever the insert is. That is mainly due to the fact it does not pull hardly any air if the wall of the insert is anywhere near it. If this was done on the exhaust side that would not be the case because the force of pressure would drop significantly as soon as it hit any gap.

what is your overall plan for this p-port you are building.

Who is the question poised to?

actually, i hadnt thought of changing the port timing. I was only thinking about tube size to change the velocity of the intake, and injector placing to atomize the fuel correctly. I had a design drawn up in ProE for a prett decent solution to all that. How much of the idle problems of a PPort is due to port timing/duration and how much is due to sze and intake setup?

pat

I think the idle problems are mainly due to the amount of overlap you have with the exhaust. So mainly the port timing, when it opens. But I'd wait for Scalli to reply or someone who has more experience than I.

- Steiner

Well, from what I've determined, most of the idle problems are from the fact that people put carburetors on the things and as such have trouble dealing with the highly fluctuating vacuum. Apparently, Mazda specs motors with the factory race housings to idle at 1k RPM with EFI. But then, they run Alpha-N type injection (no MAP sensor) so fuel going in is completely independent of any manifold vacuum readings.

As for what causes the whole thing... kind of both. Intake reversion is caused because the ports are open until quite a while after the chamber starts getting smaller (this is true on all of the port timings, even the stock ones, but not to this extent) but because the large runners mean that airflow has fairly low velocity at low RPM/idle, it doesn't have enough inertia to resist the reversion. I can't say off the top of my head whether decreasing port area but keeping timing or decreasing port timing while keeping the same area would have more of an effect... there's relatively little published data on how to make pports work well at low RPM, for obvious reasons. ;) Though really, for relatively large changes, it doesn't make sense to not change both at once.

Of course, you have to realize that (at least according to Mazda technical papers) the MFR motors had intake runners that taper as they go towards the ports. The throttle plates may be 48mm (flat slide) holes, but where they bolt to the rotors, they're down to (off the top of my head, don't have the papers in front of me) 39mm. Ignoring frictional losses, that boosts airflow velocity to around 150% what it is at the throttles.

I dunno. Trying to get the things to run well at low-load/RPM seems to be missing the point to me, especially since most of techniques to do so require changes that kill high RPM breathing.

It is both the timing and the tube size. This setup is the piston equivalent of a full race cam and a tunnel ram intake. No matter what you try to carb it with you have idle problems.
In the case of a piston engine the tunnel ram lets the fuel drop straight through the valves which are staying open a long time to maximize the air/fuel charge. That setup is great for drag racing but sucks for street.
That is why I think to get the best of both worlds the inserts and runner extensions would be ideal.
Most people have to settle for what in their view is a happy medium for a street/strip cars and that medium by default will take from the maximum potential of both street friendly and drag performance.
To hell with the balance. I would much rather spend 20 minutes with a T-handle allen wrench to change the intake setup and change maps.
Now of course this does not take into account gear ratios and trannies. A really nutty idea would be to have a Ford 9" with a limited slip for street and have a solid spool with a better drag ratio in a pumpkin for the track. It would be a royal pain in the ass but it would be the best setup to go from a true street to a "badass mamma-jamma" drag car :)

Come on if you're not driving the car every day, it would be tremendous fun to have it just bad as hell. Sloppy ports, overlapping, with that gorgeous brap. Twin wastegate runners coming out behind the front tire, with a downpipe extension coming out right behind them hooked up to an electric valve. Propane/methanol injection with an antilag setup on a huge turbo. Ohh sorry let me wipe the drool off my chin and try and wake myself from this dream.

- Steiner

Enh. Turbo, schmurbo.

Hey we all have our dreams.

- Steiner

But think of the bets you could win when you were able to back what would appear to be some pretty outrageous claims by stating you could do (put E.T. here) in a quarter with the same motor without NOS. While they are listening to this mild mannered sounding motor that they know full well could not do the time you stated.
Talk about fun and profit :D

Well around my town in home, most people know which cars are the ones putting down serious numbers. That and quite a few of them have dumps on them. Thankfully the local police just crack down on the dumb people in the group i.e. people doing burnouts trying to race from stoplight to stoplight etc. I used to want to have a conservative setup that could still kick butt with a few changes, but the more and more that I go out, when I'm home, the more I just want a bad ass car. I like having a race setup on the street I think it would be fun, not to have any crap, besides I have the truck for dd.

Anyway to try and get back on topic, if you really wanted to over-engineer it so that you could go straight from street to race, you could design a system so that the internal tube could close in on itself. Basically have the internal tube not be completely solid have a peice at the top and bottom that can move up so that it retains an oval shape. Problem with this is you have to design very small components to be able to fit in there, drill the outer diameter larger to accomodate them. And the main reason is because the tolerance at the actual housing, where the seal travels, would have to be the same. You could have external parts to just have a lever push up. But again this is basically just over-engineering the crap out of it. I have a hard time coming up with easy solutions I always want to do radical things, and often don't even think about the simple ways until pointed out. I really need to fix that if I am going to be any use in the job market.

- Steiner

i'm still stuck on the sliding inserts thing...heres a quickie i did in class the other day...you should see my calculus notebook. lol. seems like this way you could tune it for a continuous map based on a MAP and then modified per how far open the insert was...and the insert could also be electronically controlled by the computer so that its open percent was a function of RPM.

am i missing something?

you dont think that the heat + vaccum would cause a problem with your slidding insert? would it be air tight? how?

i dont mean to hate, i just want to get your creative juices really going.

it would be semi- airtight. as in, a tight fit, but not necessarily comletely airtight. kinda like a slide stye carb like on a motorcycle. wouldnt need to be airtight, as it is not sealing anything per se, just changing the port size.

pat

gotcha

Nylon or Teflon o-rings work great for those type of setups.