12A half bridge - remove exhaust sleeve?
 

I'm not so concerned about street driving with this engine because its main purpose is autocross in the SM2 class.
I've widened the exhaust port to within 0.5 inch of the side and have brought the lower edge down to to create a D shape with the straight side at the top. I wasn't sure how far down I can remove material so I cut open a scrap housing through the exhaust port. Exhaust sleeve is removed.
Now I can see how far to lower it without getting in to the coolant passage. This is the standard 12A exhaust port.
http://i84.photobucket.com/albums/k4...IMG_3340_1.jpg

After doing this the exhaust sleeve seems to be more of a hinderence than a help. If I grind the sleeve to match it to the new width and earlier opening the sleeve becomes very thin. I don't think it is going to help the flow. Should I throw them away?

*Right clicks - saves picture in tech folder*


They also isolate the housing from the hot exhaust gasses.
Im willing to believe that running without them could raise the operating temperature of the engine.

are you going to port all the way up to the top of the port? I don't think that overhang would be very good for flow.

I bet you could get away with removing them, but coating the inside where the sleeve went with some kind of ceramic heat barier would be a good idea, maybee the 2000+ degree jet hot coating. You would also need to fill the sleeve pin hole, but thats no big deal.

No, you don't need to fill the pin hole; it's blocked by the irons. Some sort of ring is nice at the end of the port where it meets the header though; where the flange of the exhaust sleeve was, otherwise the transition's even more abrupt than it would be.

I dunno how much you want to lower it though.

temperature would be my concern as well, but i do know many have run race engines without the sleeves. i've seen them. i suppose a coating could work to keep temps "normal", but if it did become a problem, increased cooling volume should work just as well, right?

if not filling hole I would be woried about exhaust possbly breaking down the outer o ring over long periods of time. Maybe its of no real concer.

The mfr peripheral port housings don't have sleeves. They are just aluminum. Heat gets rejected by the coolant system which is why they don't melt.

I like this cross sectional cutaway. It demonstrates very clearly why I made new sleeves for the 13B.

yes it does!

I like that cut away as well. It goes good with the 13B rotor I cut up. Anybody want to see a 13B housing hacked apart?

Thanks for the replys
I decided to keep the inserts and matched them to the ports.

Hey Bruceman,
Nice cutaway. On my 13B I tig welded a bead at the edge of the sleeve. This gave me some meat to play with using a dremel and a carbide bit. I just kept grinding/fitting till I had just a thin gap between the housing and the sleeve and a very nice transition.
Oh yeah I'm just up the road from you. If you need any machining or shop stuff done let me know.
http://derekfons.com/rxbeetle/images...l/P1010077.JPG
http://derekfons.com/rxbeetle/images...l/P1010093.JPG

Oh yeah I'm just up the road from you. If you need any machining or shop stuff done

the gap is there between the sleeve and the rotor housing for air injection...

I removed the sleeves and made new aluminum ones in my 1/2 bridge REW. Temperature difference is minimal. Hottest it would get prior to removing the sleeves was about 82* C. Now the highest I've seen is 83.5* and its getting pretty damn hot here in AZ..
http://i15.photobucket.com/albums/a3...ust-port-1.jpg

Any long results from running w/ no exhaust sleeves. Pros/ Cons?

I've been daily driving my car since April w/ the above sleeve setup. No problems whatsoever with overheating, and even in the summer when ambient temps are 115*.

I ran a N/A 12a streetport with a similar exhaust port as 2a+RoN's without a sleeve at all... the car was my daily driver for over 2 years and saw 8k, 9k and even 10k weekly if not daily :naughty: in all weather climates from 29-108 degrees.

The motor never missed a beat and ulimatly was torn down due to a oil pressure problem that was the result of a breech in the front cover/plate oil galley.

Sweet. So it is an option to remove these things w/ no adverse affects. Cool!

Dang Bastard, did you build that motor?

Did you have the rotors clearanced, lightened, and/or balanced? I'm working on a custom peripheral port 12a and will see 9k often. I'm definitely going to have the clearancing and balancing done. I'm considering the lightening.

Just adding something to this

You only want to port the D shape (With the Stright edge on top) with turbochargers.

The early opening helps spool the turbo

If you are going to run it N/A you want to open later so you use every little bit of the exhausts power before it leaves the motor.

Also the more square the opening is the louder it will become.

Just my .02

I was 15 at the time and it was my first motor...my older brother did most of the work. we spent days breaking down over 10 motors to get the best parts we could find. Back in those days the only companies around were Rotary Engineering and Racing Beat. The GSL-SE was just coming out in showrooms :lol: and no one knew what an RX3 was

we assembled the motor on a stump in the back yard and after firing up the motor for the first time it smoked like a chimney. we figured it would have to be rebuilt again but i drove it for a few weeks anyhow. Then one morning I fired it up and the smoke was gone:shocking:

anyhow that motor ended up lasting for over 2 years and heard the buzzer almost everyday.
the motor made great power from about 5k all the way up to about 9k. anything above 9k was just to keep the revs up


the only thing done to the motor was porting. The motor was rebuilt with all used parts with the exception of the gasket and o-ring set.

12a's rev a lot better then 13b's and if you balance everything then there is no reason you shouldn't be able to have a super reliable pp motor. the only issues the pp motors have are the blocking of the water jacket. after a while they just start leaking coolant



the large square ports have been known to work the apex seals pretty hard. if you plan on building a motor to last a long time I wouldn't go as big as the one pictured above. The rounding of the closing edge is to help releve the flexing of the apex seal

yes... they get very loud and raspy with a port like that

Well most people think that the apex seal flexes because of the square opening, but the flex is from opening up the exhaust (Side-to-Side) and not leaving enough metal on both sides. If you square up the top and bottom and don't touch the sides much there is no problem with flex.

who else here is running with no exhaust sleeve

I believe a big part of the bowing of the apex (steel) seal is due to the blast of exhaust moving across it when the port opens. Take a torch to a piece of steel laying on a bench and pay attention to which way it curls. This is why ceramic is superior.

ive done them with and without the insert,, D ports with flat up, D ports with flat down, early open and late close,,
i have done the shop templates,, and even evolved my own over many progressive changes
you name it,, i gave it a crack ( well maybe not the roo tail port ! )

i have seen nil ill effects on any housing from running sans insert,, beside maybe a slightly hotter running engine
\
IMO
taking the insert out allows you options of moving the floor or roof further
and allows you to take out the reversion step and get a straight floor if you wanted so

to get the best from them ,it will sometimes require you to bell mouth or port match the extractors or turbo manifolds


i find the D port with the flat down allows you to follow the natural shape of the casting ( sans insert ) a little better
and the rounded close ports are certainly quieter , and interact with carbs better

i see few advantages in having the D the other way around,, beyond having exacting overlap period

i find the big square ports suit turbos as they have best surface area for the port timing
and you can control the exhaust/ inlet overlap period better with the straight close
they are louder,, and in turbo engines if you take them wider
there is large gains in TQ across the majority of the rev range to be had for minimal changes in port timing

how much you get away with will depend on the revs and the type of seals you use
i have had nil issues with +5 mm wider each side and mazda seals

here is a few examples,, just to show i have given all types a go



http://img811.imageshack.us/img811/7994/pic1022302.jpg
http://img42.imageshack.us/img42/4110/pic1022305.jpg
http://img856.imageshack.us/img856/9919/pic1105357.jpg
http://img694.imageshack.us/img694/3937/pic1111413.jpg
http://img3.imageshack.us/img3/8162/pic1115433.jpg
http://img193.imageshack.us/img193/3540/pic1117435.jpg
http://img825.imageshack.us/img825/6987/pic1115431.jpg
http://img560.imageshack.us/img560/2359/dsc02778j.jpg