What are the specs of the absolute largest street port that can be made on a 13B-REW? What exhaust specs would compliment it for a turbo aplication with a large A/R P trim turbine ?

 

http://www.rotaryengineillustrated.c...ts-intake.html

Gives open and close timing, although their pretty generic and conservative street ports. As for Monster street ports, I doubt most guys bother blueprinting or actually time there ports. If they do, I doubt they'll devolge their info freely on a open forum.

Monster street port? Just enlarge so your corner seals are at least 60% supported on your open side and your side seals dont catch your closing edge. Your closing edge is limited to how thick you think your castings is lol. You can get open and close times by using a timming wheel (simple gratuated wheel) mounted to the eccentric while you turn your rotor around on your ported or scribed plate.

~Mike...........

 

Cool link. I see what you mean about closing edge being limited by material available. If you had no passages to worry about breaking into; how far could you go before you caused trouble with performance?
I also noticed that you are a little more conservative with corner seal support than the author of the link. 60% vs. 50%. Would 50% support cause an engine to unexpectedly fail or simply increase wear and reduce lonjevity?
I didn't see anything on exhaust port timing. Would anyone like to teach?

 

It's such a big subject, it's impossible not to oversimplify with anything short of a full-length book. Please remember, bigger is not always better. Even a small streetport, which looks hardly worth the effort, can have outstanding results with the right setup. The "system" is always more important than the components, so it is best to match your porting to the turbo, manifolds, fuel supply, tuning setup.

As far as 50% vs 60%, the basic idea is that you need to support AT LEAST half of the corner seal to avoid tipping and possible catastrophy. Measurement of the exact percent is not as important as playing it as safe as you can afford. Turbo motors don't need a lot of overlap, so it shouldn't be much of an issue unless you just need massive port volume and durration. Even on 670+ RWHP FD engines, we are not advancing the port opening to the point where corner seal support is an issue; it's more a problem for NA guys who are doing a "rally" streetport. On turbo motors, we usually advance the opening timing of the exhaust ports and leave the closing timing alone or very close to stock. Even then, it's not a huge change in timing so much as the other changes made that result it big gains.

An introductory article on porting can be found on pages 76-79 of Volume 3, Issue 2-2006 of Mazdasport Magazine -- http://www.mazdasportonline.com/mag -- with a follow-up article in the next issue.

 

If you look closely at the picture with the Dykem layout fluid you can see a line on the opening edge of the port. That line is the path of the leading edge of the sideseal. I like to keep it supported the length of the port. Yes you can drop the sideseal into the port but for me the advantages does not outweigh the risk. I would just go with a bridgeport instead of taking the chance of damaging the sideseal. This is about as big as you can go with a streetport. Hope this helps you out a little.

 

Interesting point about the side seals. If you did a street port with half the corner seal half supported, what happens with the side seal? Is it unsupported? How is this take care of or justified?

 

^^^ Thinking the same thing?

 

http://www.nopistons.com/forums/inde...howtopic=33859

 

i think most people dont have the setup to take advantage of the ports anyways, the NA guys run the stock intake and ecu just to give one example....

 

I disagree. Porting is very effective even on a relatively stock NA car, with as little as an improved exhaust (cat replacement pipe or high-flow cat). The stock ECU on an NA car is more than capable of handling more output, as long as the porting is not too extreme. The NAs tend to run rich, so you may find more gains by leaning it out with a S-AFC or similar, but there is no need to run a standalone ECU or other extreme solution to get the benefits of streetporting.

BTW, the stock intake is already quite good. When I upgraded my old S5 NA to a K&N cone filter, cold air box and supplied it with cold, fresh air (vented headlight cover, etc.), I only picked up 1 rwhp on the dyno. But when I replaced the cats with a downpipe and presilencer, I made an additional 23rwhp...still using the stock exhaust manifold and cat-back. Exhaust, exhaust, exhaust. Forget the intake, unless you run out of other things to do first.