Hi everyone, I have a bit of a hairbrained idea I thought I'd throw around and see what everyone thinks.
I threw together a rough drawing of what I have in my head and attached it to this post. It is very rough, mind you.
The main idea is to have a sleeve inside a sleeve. The main sleeve will be pressed in and tack welded to the housing.
The second sleeve with have the same OD as the ID of the determinant sleeve, but could one of many IDs, depending on the application.
My goal was to have a port profile for a somewhat "streetable" motor, but for track days or fun at the drag strip, I could swap in a different profile.
This would also allow one to test different styles or sizes of ports.

In my rough drawing, I had the original bore in the rotor housing at ~2.248 and the OD of the main sleeve at 2.250.
The ID of the main sleeve and the OD of the inner would be approx 2.00 and perfectly round.
I had planned on buying a 1.5" ID tubing for the inner sleeve, so I'd have room to play with for non-round shaped ports.
You can also see the 2.5" O-rings I drew in to seal the sleeves/manifold. I figured this would make positive and inexpensive way of sealing everything up.
Finally, the entire system would be plumbed into a 2" tubing manifold and 54mm ITBs. And I realize I would need different fuel and possibly timing maps for each set up.

Feel free to input any and all suggestions.

*Note, the images of the sleeves are Untrimmed. I made the inner longer than the other in the drawing so the differences are more noticeable.

-Alex

 

thats a great idea!
You will have to machine all the right tolerances for where the sleeve meets inside the housing however, or else it will develop a leak.

is this in an N/A or turbo application?

have you thought of doing the same thing with the exhaust?

 

This will be for a NA application. I had planned on running the inside and ouside of both sleeves through a lathe, and run as little clearance as possible.
With 4 bolts and the o-ring, I dont think Ill have a problem with leaking. I plan on making the sleaves 6" or so long.
The longer, the harder it would be to leak I would think, at least at tight tolerances. I dont want to mess with the exhaust side, at least not for now.
I wont know if I could make a system that could contain that much pressure/heat. At least on an NA intake, its relatively low/negative pressure.

 

i thought about this too. the only problem i see with it, is that, since you can't really bring the inner sleeve safely to the rotor housing surface, that it won't quite work like the port is actually smaller.

however i don't see that to mean it won't work. for mine i was thinking of something more like a weber carb venturi http://www.pegasusautoracing.com/Images/M/72116.JPG

mine is a full MFR sized PP, and its just really different compared to a sideport, with efi, you might find that you don't even need the sleeve...

 

I had planned on bolting both the main sleeve and the inner sleeve together and using Di-Chem (sp) or some other dye and scoring the countour of the rotor housing.
And like a traditional DIY PP-sleeve, using and end mill to machine to flush.
Im sure it would need cleaning up afterwards, but if I machined the two at the same time, it would be relatively close, no?

 

You need to treat this in a slightly different way which is a bit hard to explain. At work, we design and build large mud pumps for oil drilling. Depending on how much flow or pressure we need, we change piston and liner sizes. What you are suggesting is similar to changing liners in a mud pump except for the obvious fact that liners are really like changing the cylinders in a piston engine. The concept is the same. You want a different sized tube for the air to flow through. We use liner inserts that all have the same outside diameter but the inside diameter is what is different. Then we use a crew on liner lock system that has a seal to it. You are suggesting accomplishing the same thing but with the flanges as the attachment.

I'd suggest installing a large threaded insert permanently into the engine. The each runner bore size that you want is merely a screw in insert with a flange attached to it. The flange determines how far in the sleeve goes and if done right will put it as close as you need it to be. The back of the flange should have a groove machined into it with a flat mating surface against the rotor housing so you can crush a rubber o-ring as a seal against any pressure somehow making its way up through the threads.

The threaded rod doesn't have to extend all the way into the face of the rotor housing. It merely has to get to it but should be ever so slightly machined into that surface but not going all the way through. This way you'd have a flat that you could screw everything into. The largest diameter runner you intend to ever use would then be your bore through.

 

The only issue I see with this is how much expansion will take place. If it is 6"long and is smooth with the inner surface... is it flush when hot or cold? Next would be the issue of having to machine all sleeves at the same time while the rotor housing is off the engine and it will only work for that one rotor housing. I guess the best way to go about it would be for you to get the rotor housing inserts as close a possible and warm them up. Once you have that done cut a bunch of inner inserts and machine them for that rotor housing while the inserts are hot. Then cut the ports on these blank inserts how you want them. That way once the engine is warmed up it will have the right tight tolerance.

Just my 2 Euro Cents.

 

I'm not totally sure I understand your concept. If the threaded insert doesnt extend to the combustion chamber, how would it still control the port timing? If the larger interior diameter is still exposed to the combustion chamber, would it dictate the timing?

If I were to make a inner sleeve with threads, it would be impossible to thread the it all the way flush since the contour of the housing would hit the rotor as its being turned 360. Are you simply saying that the inside diameter is more important than the the actual shape that meets the inside of the housing? I had planned to machine the backside of the inner sleeve (intake manifold side) to the same 2" ID as the runners, so I could run the same manifold.

Forgive my rambling, not enough sleep and too much caffeine.

 

It's an interesting idea for sure. It shouldn't be too hard to machine the inner tube so it is a minimal amount back from the apex seal surface. It could sit back say.. .005" and I think you would get the effect your looking for. I don't think heat expansion is too great a problem. The housing, insert, and inner tube would all be at around the same temp. A problem would arise if the inner tube would somehow way get hotter than the insert.

 

It's hard for me to explain without actually drawing it up. Let me see what I can do.

 

Lets see if this works. I very quickly drew it up so hopefully it's clear. There are actually a couple of ideas here. The first is the threaded insert. This won't completely change port timing due to clearances between apex seal and insert but would change tuning. Don't worry about a radius from a small port that then feeds into a larger radius. It won't hurt flow.

The other method I feel would be easier and there are 2 ways to go about it. The first is to have 2 ports side by side in the same housing but with their own runner. You could close one runner to get a smaller area and lower tuning. However in the side by side method, you don't change timing. Just area. If you were to do 2 ports but one above the other, you could use the lower one for lower rpms and then open the upper one later. Timing would truly change and area would also increase.

If these link up sideways I apologize. Just turn it.

 

i think there are some structural limitations that make this impractical.

1. there is not much to thread an insert into, and you have to be careful not to distort the housing as well.

2. the spot where the PP sleeve goes thru the thichoid wall isnt flat, we looked at this too, you can't screw something in and have it meet a curved surface, this is with 787B port timing which is HUGE

3. there is a small problem with the intake manifold, i guess you uses hoses.

it obviously works, but in a rotor housing it would be really complicated... we thought about something like this too.

 

I know the surface isn't flat. You can't make an insert fit against the spex seals. All you can do is machine a flat into the housing and have the insert stop at it. If you look carefully at my first picture you'll notice that the insert doesn't go all the way through. The bore of the largest desired runner size is what is actually cut into the housing. Any smaller sizes stop just short of this point. It won't hurt flow at all but it also won't change port timing. My second drawing is the only way to change port timing while changing runner area.

 

I like the idea of having two ports, but I dont think I have the means to make a manifold that complicated.
I also dont have the tooling to cut threads that large. I would be working out of a small machine shop at my university that is primarily for our Formula SAE car.

With and unthreaded inner sleeve like I proposed, I think I would be able to get the inner face considerably closer to the apex seals. Would that really make much of a difference, or would the few thousands of an inch clearance make an impact on port timing?

 

i like idea #2, that is a great one.

#1 we looked at, but there isnt enough meat there to machine it flat, although it depends on port timing.

attached pic is right from the r26b sae paper, surprisingly drawing is to scale

 

A small gap between the inner sleeve and the seal will have little impact on the port timing. Only a very small amount of air will be able to flow during that point. A couple of things you will have to consider with your design:

1: Thermal expansion: The inner sleeve will be constrained on the outside of the engine. Any thermal expansion of the inner sleeve will cause it to extend towards the combustion chamber and if a seal hits it... well u can imagine.

The Fix: Design a stop inside the outer sleeve or do some calcs to determine the amount of expansion and account for it.

2: Sleeve angle: if you are running a few thous of clearance (which i dont think you will be able to do unless u use a stop) and the inner sleeve turns a slight angle, it will cause the non parallel end of the sleeve to also protrude into the combustion chamber this will be very bad if a apex seal hits it.

The Fix: add an alignment pin on the flange to keep the inner sleeve at the proper angle.

 

Those are all very good points. I had aready thought about number two, and considered your remedy as well. I planned on using a similar pinning system as the rear stat gear in our motors. I havent taken thermo-dynamics or any materials classes, so Im going to have to ask for help when it comes to calculating the expansion of aluminum. I really think having the sleeve stop much before the ledge will effect port timing, especially if the inside diameter of the inner sleeve is much smaller than it outer diameter. I kind of think of it like the bevels on the RX8 rotors. Im going to talk to the machine shop director sometime this week and try to find a junk rotor housing over Thanksgiving break to see what I can do.

 

According to The Machinery Handbook, thermal expansion for Aluminum is 1.2X10^5 in/in per degree F. Or, .000012 in per inch per degree F. An aluminum tube 2" long gets .0024" longer when heated a 100 degrees.

You don't need to leave much clearance.

I still don't see what is going to be heating this tube so much more than the surrounding housing.

 

Nice idea!

What if you used a conical taper on the permanent metal sleeve in the rotor housing and use a Teflon liner that just meets the taper for the largest port configuration.

For smaller configurations use Teflon liner with the smaller aperture and machine the Teflon so the apex seal can actually ride over it continuous with the rotor housing surface for your more conservative port timing to get to the track.

Stuck on Teflon for low thermal expansion and if there is slight misalignment I think the apex seal can peel it off and the engine can obviously digest it OK as the 86-92 housings had powdered Teflon on the rotor housings for initial start up (93- on were graphite coated?).

Stuck on the conical taper at the housing wear surface as it is at the point of contact; ie, if you relied on the flange for location as in your original concept pic you have the entire length of the sleeve to be affected by thermal expansion.

 

What happens when you overheat the engine? I recently saw 250F coolant temps right before my stock radiator exploded. If you did machine work at 70 deg that's a 180 deg swing in temps. There is also radiant heat from the exhaust manifold. Its difficult to guess what temperatures the sleeve would see.. the best bet would be to take temp measurements of the stock manifold after spirited driving.

More realistically the tube length will probably be about 4 inches, that would cause an almost 5 thous expansion with a 100 deg temp rise.

It may not be a problem but it has to be accounted for and you should include a degree of safety just for the unknown. Under no circumstances do you want a pipe protruding into the combustion chamber.

 

The rest of the engine also expands with heat. All of it. And yes, the aluminum housings more than the irons. Your housings are machined at 70 degrees and expand when over heated the same as any aluminum. So will the permanent insert and the removable tube. 250 degree aluminum is 250 degree aluminum. There's no magical difference because it's made by Mazda. I have a feeling, since there is a bunch of much cooler intake charge going through it, the inserted tube would be cooler then the permanent one and the coolant temp housing.

Four inches!? Keeping the assembly right against the housing and under the intake, one should not need more than a couple of inches.

I have a question for you. If I have a plate with a hole in it and then heat the plate, does the plate get bigger and the hole smaller?

 

I like the Teflon idea. I priced 2" OD/1.5" ID tubing and its about $40 a foot. Wouldnt need much.
With Teflon though, how do you make some sort of sealing surface, ie flange?
You cant weld it or fuse it, right?

Has anyone else ever made a Pport with sleeves that extend to the combustion chamber?
Ive found a few pics of some, I attached one as an example.

 

*Double post*

 

Nope, plate gets bigger, thicker, the diameter of the hole gets bigger, and so does the distance from the edge of the hole and the edge of the plate. But I dont see why thats important.

Yes, everything expands but not equally. The inside sleeve is constrained at 2 points, the inner housing surface and the outer housing surface. It will not expand by the same amount as an aluminum pipe that is constrained at only one end. The housing is also constrained by dowel pins and tensions bolts it will not expand at the same rate that a free housing would expanded at. Overall its probably not an issue but if I just spent alot of time and a nice chunk of money I would make sure I was convinced that it wouldnt be an issue.

Your right, 4in is probably pretty generous.

 

Actually the way that I'm talking about is exactly how Racing Beat builds their p-ports. They take and bore a hold through and thread it. Their insert is also threaded. The insert doesn't go all the way into the housing. It stops at a flat just before the end. The bore that extends into the engine is the same one as the I.D. of the sleeve itself. They just use epoxy to fill in and seal it all off but none of it is welded. Expansion also isn't an issue. The idea may not be practical for someone with limited resources but it is definitely possible and works quite well.