exhaust porting
 

other than advancing timing is there any point in exhaust porting for a mild street port? the sleeve is what is gonna determine the port diameter, so is there really any need in porting the housing, since the sleeve will still be a bottleneck?

This can increase your power quite a bit but your torque will suffer. The sleeves themselve are bottle necks but you can get sleeves made that are the same size of the port. There was a guy who did it on this forum and said that the power was more that porting the housing.

i'm sticking w/ the stock sleeves, i'm wondering if it's worth it to port the exhaust if i'm still using the stock sleeves.

YES!

The problem with the stock sleeves is that the area of the port changes so rapidly.

You have two choices - enlarge the opening of the port, or make a new sleeve. Leaving it alone is the worst of both worlds.

peejay, how does it help if i port the opening if air still has to squeeze through the sleeve afterward? what's better for a street driven fd, to port the bottom or the top of the exhaust port?

port the housing to the sleeve size. it will make a huge difference. port the top and the bottom of the housing as well as the sides ... the sleeve acts similar to a venturi ,, helping evacuate the exhaust quicker ,, like a scavenging affect... if you take out the sleeves you engine will run way hotter,and if you measure your exhaust manifold its most likely the size of the sleeve so it wont make a difference anyway...

there was a big disscussion awhile ago and i think someone said they could just remove the sleeve and its not needed in the exhaust port...

it is needed if want low end drivability. anyway the advantages of taking out the sleeve and hogging out the exhaust port won't be realized w/ the stock exhaust manifold.

I'm the guy who made new sleeves for my engine. Maximizing flow through the stock size port with a new sleeve yields better flow than a typical ported stock sleeve exhaust port does. The factory sleeve is not a bottleneck as far as port size is concerned. Its problem lies in the fact that the sleeve has a very high amount of area increase over a very short distance. This causes turbulence through the port which decreases the velocity of air. This turbulence in the port causes it to be much more inefficient than a smooth, nonexpanding port of the same size. The easiest way to help this is to port the housing out to the sleeve size. The coefficient of expansion is much less now so turbulence is reduced and flow is increased. There is still expansion however and still a power loss over optimal. Changing the port size also changes the overall timing and overlap. Adding timing is not neccesarily a better thing for power but it is to a point. Do not remove the sleeve altogether.

Man I wish I had some new sleeves!

Very true...if you hate you engine then go ahead and remove the sleeve altogether. Your flow will be horrible, but you'll gain power on top, but it's NOT HARDLY worth it. Remember torque is what gets you moving so why get rid of it? Horsepower just sells cars :D (okay so maybe it does a little more, but you can't deny that...)

who you talking to? no one ever mentioned they were gonna remove their sleeves.

I was reading 2 posts at the sametime and posted in the wrong one. :D

Are you on crack? have you ever done any of this or are just making shit up from what you have think to be true?

I have no sleeves ! I have alot of torque and allot of power, my car revs like a motorbike, my car is efficient (400km to 50 lt fuel city driving), it does not over heat, it has been running for 3 years (daily driver) it has 566bhp on pump gas @ 7300 to 7500rpm with a wide flat torque band !

Proper porting techniques shift torque to where you want it, power is what does work. ! Do some searches on this forum, learn about fundamentals of physics, then post some facts bro :D

You can make a nice size port around the stock sleeves on a 13B rotor housing.

I have no sleeves either , the exhaust ports were increased substancially over stock and were done very , very well by our local "porter" who has years of experience with both turbo and non turbo engines and swears that thats the only way to do it , especially if its to be a high HP turbo motor !.

I`am not running sleeves either, it does make it LOUD.
The inside size of the port is 1.5 "(width) height is about
1.75 ".Outside is 2 1/4 inch(extractor side)

It has lots of overlap, and makes great power !!(not to even mention the lumpy idle combined with a 50deg streetport (extended port in some countries)

Now then...before you go on talking about people being on crack, think to yourself...you are running a TURBO CHARGED CAR! Of course your flow will be greater, I was speaking of the N/A car which doesn't nearly have the same velocity as the turbo car. Sorry if i wasn't clear on what I was saying, but ask next time before you spew about the crack that I'm wiping from my nose. If you still want to call me a crackhead feel free to do it, but then you must do the same for Mazdatrix, myself, and rotarygod.

Not to sound rude or anything, but trust me I've been studying physics for quite some time now...so don't worry I'm not gonna post some crazy bullshit unless of course it's a question about the piston rings :D.

I've been studying the exhaust ports quite extensively lately and it does appear that there are some neat things that take place with removing the sleeves. I am speaking from the turbocharged side of it though. As long as no one has to pass emissions (like I do!) then there appear to be some advantages to removing the sleeves and going REAL big on the turbo cars. Removing the sleeves on an n/a would really only be beneficial if the car had a huge bridgeport or a peripheral port. It is an absolutely terrible idea for a street driven stock or street intake port n/a. Power band is shifted too high from the exhaust standpoint.

The new sleeves (like mine) and higher velocity way of doing things works fantastic on n/a's and turbos as well. However the new sleeved exhaust port will not have the ultimate power potential that those with monster sized exhaust ports have. What it will do good is spool the turbo extremely fast, have little overlap (good for emissions), and good low and midrange power for street use. Top end is still good if you are trying to stay under about 450 hp. It is great for someone who wants a fast car with little turbo lag and a broad power band lower in the rpm range than a racecar.

The new way of doing things is to go with MORE timing on the intake and exhaust for turbo cars. This was always contrary to normal traditional thinking but many are proving it to be fairly streetable with the structural capability of the engine as the limiting horsepower factor. Good for racecars or those who don't have emissions testing (or connections at emissions stations). I have a friend who has a tube frame rotary powered VW that has an insanely large bridgeport with monster sized exhaust ports that runs 10's. It idles very bad, has poor emissions, poor gas mileage and an 11000 rpm ceiling (where the bearings like to die!). Not a streetable n/a but an application where no sleeves is better. Smaller intake ports and a nice turbo might be a different animal however.

If you remove your sleeves upgrade your radiator cus the bare aluminum will transmit way more heat to the water jacket than the steel, they're there as a heat barrier, also removing the sleeves doesnt do much untill you make the port pretty big

My motto is: If your not grinding intake ports large enough to HAVE to pull the sleaves then you need to go bigger. Cus if your not then your still playing in the sand box.

CJG