coldy13

I don't know when I'll actually get started on it, but I'll be making my own P-Port sometime soon. I just picked up a good engine today, got a GREAT deal on it. It was a new engine from Mazda a couple years ago, now it has 20k on it. The machining of the housings is not a problem at all for me, but the port timing and angle of the port is. Time to start researching to find what timings/angle will give me the power where I want it.

sccagt3

I have a 51 IDA and three MFR PPorts for sale!

coldy13

My dad and I will be making the PPort housings ourselves, we have the right machines and tools to do it with. But how much do you want for the 51 IDA, cause that's the carb I want.

chairchild

And how much are you asking for those housings?

Are they 13b or 12a based?

sccagt3

$550 for the carb and $500 each for the 13b pp
housings. These are in the parts for sale section.
Sorry for the post here also, just thought someone
in this thread might be more interested. Price is firm
find me a better price for the same items and I'll
buy them.

chairchild

Dammit - I need 12a PP housings

re10

Has anyone here done or seen a 10a PP?

Rotortuner

I think there is at least one in OZ. look in some of there forums and i think you should be able to find it. i think i saw a pic of one in a r100. Looked so cool.

CJG

neit_jnf

iTrader: (17)

Look at the ports on my p-port engine, I need advise to make them larger without tinkering too much with the intake and exhaust timing and without f'ing up anything. They are from my model rotary engine made by OS.

Complete motor teardown here: https://www.rx7club.com/showthread.p...hreadid=280086

Scalliwag

That little motor is cool! Without effecting the port timing the only way you can go is sides. If you do anything you may want to make it look a little more like a square than a circle.
But as far as I know you are in fairly unexplored waters to you don't want to do anything too radical. You may want to check with some of the RC model hobbyist and see if they have any information.
I would square off both the intake and exhaust side if it was me but I have fugged up a lot of shiite in my 43 years so you may want to keep that in mind

Kenku

Oh, I figured I'd talk about this in here because it's sort of applicable.

Picked up an SAE paper the other day; by Mazda, from '90. It's modeling power output of peripheral port motors, followed by coming up with an "optimum" port timing. What's interesting is that the port timings they come up with are completely different than any other published ones I've yet seen. The "baseline" port shape is about the same as the published values for the MFR ports on Paul Yaw's site, but the "optimized" port is... well, I'll just come up with a little chart.

Baseline Optimized
Exhaust Open 73 BBDC 73 BBDC
Exhaust Closed 65 ATDC 55 ATDC
Exhaust Area 9.2cm^2 12.5cm^2
Intake Open 100 BTDC 80 BTDC
Intake Closed 75 ABDC 80 ABDC
Intake Area 20cm^2 25cm^2

Note that there's both less port timing and more area... and all the port timing changes made for less overlap. The ports are a lot more rectangular, extending out towards the edges of the rotor housings farther than the more square baseline ones.

Oh yeah, also note that the port they publish for the "baseline" one opens the intake 14 degrees earlier than the MFR one Yaw has the data for, but is otherwise identical. This might be explained by the fact that all the MFR housings I've seen for sale are supposed to be for earlier motors, so perhaps there's even development work done between the later MFR housings and the ones we're familiar with.

They don't actually publish very detailed dyno results. The "optimized" timing beats the "baseline" port by a good 2-5% volumetric efficiency from 7500 RPM on up, and trails by 1-2% below. The one dyno plot they have is of a 3-rotor motor, and seems to indicate a gain of 30hp at 8500 and 50hp at 9000, while only losing 10hp at 7k or below. Absolute power numbers... aren't on the graph, regrettably. And even the comparison numbers are estimates, as the graph is of a type used to merely show a trend.

The capper to this is that the time of the paper (and some of the talk about variable length intake tracts on a 4-rotor later on) seem to indicate that this was either being developed for the R26B LeMans motor or for a follow-on effort... either way, it makes me *REALLY* curious.

Thought some of you might be interested.

Scalliwag

Wow that is interesting stuff! Once I get caught up with all this new shop stuff I got going I want to setup a degree wheel and layout a housing to that spec and see what it looks like.
I may talk David Sanchez into letting me do a couple of his extra housings to that spec as well.

Kenku

Well, they have some lineart pictures... I'm half pondering scanning the article and turning it into a PDF for people to look at. The SAE number is 900032 and it's in the transcripts (the big, yearly, bound best-of books) so it should be possible to find in a library.

I'm seriously *SERIOUSLY* thinking about carving those ports into a spare (in questionable shape) 12A we have. Could use the ITA car I share with my dad as a testbed... uh... and maybe they wouldn't notice the Weber-fed peripheral ported motor. Well, okay, more seriously, in the class I autocross in it would be perfectly legal to run a pp motor.

Might be trickier to machine... the hole is 46mm diameter at the surface where it mates to the intake manifold, and much larger on the port-side. Or, in terms of area, 17 square cm widening out to 25 square cm.

Oh yeah, the model says that 30 square cm ports will get even *MORE* flow across the 7-9k RPM band, but only by around 1% over the 25. And I have to wonder if there's room to *fit* 30 cm of port area without going the whole width of the housing.

Kenku

Oh, hm. I just thought of something that could make building this a bit more of a headache. Exhaust.

I'm under the impression that in most PP cars, the exhaust sleeves are taken out for. Problem is, because the port timing on the "optimized" motor isn't that different than stock, obviously most of the added area is going to come from expanding to the sides. So, this both means that the normal sleeves won't work and that there needs to be a sleeve in there to prevent a sudden expansion in the runner which would kill gas velocity and cause turbulence.

Well, this led me to start thinking, of course. The stock-style flanges aren't really all that complicated... seems to me that it would be possible to bend a piece of steel tubing into the right shape and weld a flange on the end. There might have to be some extra aluminum coming out of the hole to get it to go in, but I think it should work.

Scalliwag

If you were real good with blacksmithing skills (hey aren't we all?!?!?! ) you could shape a malling form so you could take a red hot short piece of pipe and whack it down onto the form. The form would need to be shaped the way you wanted the inside of the sleeve to look.
You would hammer form the piece to shape on the form. You could use a very short cut of pipe that matches the collar and weld it on from the inside. Then rotary down the weld.
The backside of the collars at the flanges have to be pretty square to sit right in the reccess.

Sure that is a lot of work but it could be done. The hardest part would be making the form.

Kenku

The form doesn't seem that hard, really... but it would really probably be simpler to do it the even-more old fashioned way, with a hammer and anvil.

Doubt it would be perfect by any means, but it would be doable with equipment I have. And welding... well, I know some guys.

It'd be something just about unique too.

Scalliwag

What I figure on using a form is that it would be easier to match the shape for each pair.
Plus if you ever got it right you could knock the out quicker and probably sell some sets of "high-flow exhaust sleeves" Hey you gotta admit that sounds pretty cool!

Kenku

Well, that's a very good point... both consistency and doing it as a business venture.

I figure though, y'gotta start somewhere... the business thing gives me ideas though.

See, the reason I got this paper in the first place is because of a long-term project I'm working on. I'm trying to figure out a mathematical model for rotary engine performance based on the normal geometry and ports. This has, obviously, been done before... just not in form that's easy to use (so far). The trick bit is a thought I had to have it go and come up with a theoreticially "optimum" port configuration. Say, you want the most power possible from 5-9k RPM... you tell it that and it comes up with a configuration with the most area under the power curve. Or you want part-throttle running to still be good, or to get emissions under such and such level... all the stuff is *out* there.

LIS, long-term project.

Scalliwag

Wow that is a monumental task you have there. Especially when all the other variables have to be factored in; length and diameters of runners and exhausts and the length from the exhaust port the tubes come together.
If you factor in boost and compression ratios of the different rotors that could be used this becomes enormous.
That would be very baddass to pull off. I sure hope you do A fully staffed research facility and a lotto powerball win (or dead rich relative) would sure speed things up.
Building the motors and manifolds and getting an engine dyno and documenting every detail makes me numb just thinking about it

Kenku

Well, boost I was basicially going to avoid screwing with. Although, I did see an interesting paper presented this year about modeling transient performance of a turbocharger... I don't see any reason why it wouldn't be possible to go back and tack more features on after it's working.

I'm thinking that intake and exhaust manifold tuning are comparatively simple and well understood. Or, to put it another way, I think that it *might* be possible to do them afterwards without messing up the data. I hope.

The trick is crunching the numbers without doing literally *EVERY* possible combination by using fairly simple tricks to get it to see trends. Say you have 20 variables to define where the ports are. You have upper and lower limits to where they can physicially be on the engine without eating seals, leaking oil, or other various stupid things; those limits are programmed in beforehand. So for each of those 20 variables, you try 20 different settings, making 400 setups. That seems like a lot, but computers are here for a reason. You compare the area under the curve on all of them and pick the best few. Most of them are going to be useless, but likely there will be a chunk of data that looks interesting. So you take that chunk and repeat the process, narrowing down each time... and keep doing it until the gains each time are too small, or the power blinks off and you lose all the data.

There will end up being a *lot* of engines made and run on dynos to verify things, by necessity. Probably a dozen or 3, which is a daunting prospect to a college student. I'm... not sure *exactly* how to deal with that part of things. Research grant, maybe... or I could take out a loan, cut a deal with Mazda to get a shitload of unported housings (and a slightly smaller shitload of internals) rent time on a CNC mill, do nothing but build and dyno engines for a year or two, publish some of the results, sell the ones that turn out really good to racers, get hired by Mazda on the condition that they pay for the rest of the expenses that I'd incurred (probably cheaper than if they did it themselves) and successfully pave the way for rotaries not only coming to prominence in racing but in the consumer market as well!

Okay, maybe that slipped from "good, if fanatical, idea" to "flat out delusions of grandeur".

peejay

Where can you autocross with a home-built PP?

SCCA only recognizes MFR p-port housings. Does NASA have an autocross series now?

- Pete (Interested...)

Kenku

I'm in Midwestern Council, which is a *LOT* more loosely organized... but evidently a lot less bureaucratic. As people have said, it only exists for the purpose of going out and racing... anyway.

Autocross rules are at http://my.execpc.com/~mcscc/mcgcrv6.pdf but I'll summarize. The first part of the class is, like anything else, based on what car you have. The second bit is modification... from stock, prepared, modified, to race. What's neat is how the modifications are listed though... there's a list of types of modifications, and each has a points value attached to it... stuff like running specialty compound tires is 3 points, changing spring rates is 2, cams are 2, etc etc etc. For a total of 0-2 points you're in stock, 3-7 is prepared, 8-17 is modified, and over 17 is race. So you get to do *WHATEVER* you want to the car. If you're thoughtful (or nutty enough to do it without much suspension work) you could run a turbo 1st gen in prepared... or spend those points on suspension like most do.

Well, the car I share with my dad is prepared... pretty close to the limits of ITA. Adding up the points honestly, I'm autocrossing in the race class... so really, there's no class that they can stick me in that's *MORE* modified. Heck, a lot of the other people out there are running hotter cars... the guy who won the last time I went out last year was running a turbo VW Rabbit with coilovers... and knew what he was doing behind the wheel *FAR* better than I did.

Oh yeah, this is "high speed" autocross; open-tracking as a lot of people prefer to call it.

Actually, what's really neat is that they pretty much will let you race anything you bring down even in wheel to wheel... one guy who I've seen out a few times has a Porsche 914 with a lot of modifications including a 911 motor (of some vintage or other; sucker's keeping pace with the GT-1 cars) and... someone who had a Ford Mk. 4 that was constructed out of spares.

... anyway. I'm done rambling.

peejay

Neeeeat.

Sure beats being bumped into (E Mod? D Prepared? I forget) just for having a street ported engine. Even though the rest of the car is bone stock. Reminds me of why I never bothered autocrossing.

RALLYcrossing, on the other hand... You can do pretty much what you want, since the car is not the limiting factor.

SnowmanSteiner

Another thing to consider to make your problem worse is variable intake runners, like on the 787B to give a broader peak power range. I've thought of doing something like this but more specifcially just for tuning intake runners, so that I could devise a system like on the 787B of variable intake runners to yeild a peak hp range over a larger area. Of course this would depend specifically on the port that someone had, exc.exc.

- Steiner

Scalliwag

Theoretically his model should account for a variable intake runner by default. Whatever data he generates on a motor with different length runners could be used to find the optimum length at particular RPM ranges.
Let's say he finds the peak horsepower/torque for a 6" runner and then the same for a 12" with the same diameter tubes. Even if your test runners are fixed it could still create the model for a variable.

The 787b is an awesome piece of machinery BTW