astrochild7

iTrader: (3)

what is the optimum port width on exhaust.. when doing a race port. I'm doing somthing like a d-port shape. i know we don't want to loost the seal in the exhaust port, but what can you get away with????? any takers...

<<<>>> also looking for some good pics of port styles and sizes both intake and exhaust....

thanks
jody hammock

astrochild7

iTrader: (3)

no one????

Jimmy325i

Optimum is relative to the intended use of the engine. Exhaust timing has a huge effect on useable power and where it happens. We need to know more than you don't want to spit a seal out the first time you crank it over. (I doubt you'd be able to make a decent looking port capable of that without removing the inserts)

astrochild7

iTrader: (3)

the motor is a 13b currently stock extrude honed intake- ported throttle body plan on matching intake with housings.. while the engine is apart we are lightening and balencing the eccentric/rotors - milling the oil passeges - modding the bearings - possible half bridge port. - siping the water jackets
still running s4 turbo(upgraded comp. wheel / huge port on wastegate/ bigger flapper-- huge port on hot side of turbo.

a friend of mine has a machine shop next to his house...<<i mean back yard>> i plan on using this motor as a template of modds. i'm sure i can offer these mods at a resonible price. if anyone is interested..


thanks

jody hammock

astrochild7

iTrader: (3)

hey jimmey325 come back your the only one to say anything... what is this sensitive info.... its only a matter of time...

rotarygod

iTrader: (1)

As long as you are still keeping the stock exhaust sleeves then you should match the port width to the sleeve opening. It is not too much. How much you go up or down is up to you. If you stare at the rotor housings with an apex seal in hand you can easily tell how wide is too wide. Unless you are going to remove the sleeves altogether you shouldn't see any problems. I have a streetport 6 port with ports as wide all the way around (top, bottom, sides) as the exhaust sleeve opening and it works like a champ. It is using the stock seals. My 4 port turbo engine has custom machined exhaust sleeves and the opening is slightly wider but not really enough to visually tell. No problems there either.

A quick question on your setup. Are you still using the stock turbo with just a compressor upgrade? If you are then it will be just fine for a streetport but not for a bridgeport, not even a half bridge. The problem you will encounter is that on the top end your boost pressure and therefore your power will start to fall of pretty rapidly much like the stock turbo does. Before it does go back down however you will see an increase of torque throughout the usable rpm range. The stock exhaust turbine (as well as many aftermarket) is just too restrictive. You are pumping more air into the engine since you have more intake timing but you can't get it out any faster. The overlap of exhaust port and bridge ports will cause some of this exhaust air to go back into the intake side since there is too much of an exhaust restriction through the turbo. This will dilute it and kill your power. This only gets worse and worse the higher boost you run. The only cure at this point is a much larger turbo. Stick with a low overlap streetport and you'll be happier. If you can afford a larger turbo then hell yeah go for it. If you have a completely aftermarket setup now then the problem may still be present but not to the extent of the stock unit.

astrochild7

iTrader: (3)

yes i realize the turbo issue but i have no choice at least for a year...(other chioce is run 2 s4 ported turbo's???alway's ??) well second i can't remember who sells after markert sleeves.. the other thing is my engine builder and i have been looking at being conservative with exh and just open the mouth to the sleeve.. but were looking at puting a small pp port within the street port timing he want s to plumb the feeder out of the secondary runners and really hog them out.. i haven't seen many people run small conservative pp in a d-port shape with the street port sides still open.. I've heard thats what they are doing in aus.... to keep an idle..

third i'm lucky i pulled this engine apart when i did. it was getting ready to eat the side seals and a cracked apex... the housings are almost new very clean.. orig problem blown oil control seals, due to addition of atkins thermal pellit.. the oil seals couldn't handle the increase ... also found chunkes on the pan... but engine is perfect.... think came from when i blew the last turbo cold side???

astrochild7

iTrader: (3)

yes i'm addicted to the thaought of a street reliable pp. gotta have it.... it's free