has anyone ever seen anybody cut square exaust ports into a turbo motor??

i bought a 13Brew outta a very hard running south florida FD (dynamic turbo's 10.50 sec FD)

when breaking the motor down to do a rebuild, i noticed that the motor had square exaust ports.



my engine builder laughed for like 10 mins. when he finally stoped laughing, he showed me an old racing beat book (or it may have been dowlings book) that had a line in it saying "when oppening up the exaust ports, be sure to square them up" the book meant to be sure that the ports were even. apparently Mr. C***** L**** of C** Racing in Miami took this the wrong way and cut SQUARE EXAUST PORTS.



my question is this, is there some kinda performance advantage to be had here? the guy who built the motor is well known in road racing circles, and had been building powerful rotaries for many years. does he know something i dont? or did he just make a mistake or what?



again, this motor put out 540rwhp in the FD and the car ran consistant 10.50's with a pettit ECU and an AIC. something had to be working right.....



anyway, i didn't have time to wait for my mech to port another set of housings, so i just let him enlarge the intake ports a lil more and told him to re-use the square ported housings....



any thoughts?



http://nopistons.net/albums/album51/aad.sized.jpg



heres my secondary intake port after porting, before polishing



http://nopistons.net/albums/album51/aab.sized.jpg



http://nopistons.net/albums/album51/aae.sized.jpg

i think it might be ok, cause the whole port is open at once? it obviously works



mike

tell your builder to do more research than just using an old racing beat book.



I have seen pictures of square exhaust ports posted before on other forums, nothing wrong with them....specially for very high power turbo engines.

damn that thing opens up real early. why'd he make it so big if the sleeve's still in there? i don't think the shape of the sides of the port matter too much.

Funny I did mine close.My top and sides are squared but i have a little bit more (not much) of a concave in the middle/bottom.Notice stock hight and width isnt much more.High boost fast release(why squeeze cause you start losing compression any way) to minimize exhuast in intake mix.

I dont think they are suposed to be "Square" and very big as the Apex will hit the edge Square on.



I know there is an Advantage of the ports that big but if it was me i would have shaped them a little or put a slight rad on the edges.

my builder was also concerned about seal breakage due to the sel hitting the edge flat like that....

any other opinions?

Nice looking housings you got there. https://www.nopistons.com/forums/pub...#>/biggrin.png

Hey, I recognize that motor!

I thought you were joking about the square exhaust ports. Have you called CLR to see what he thinks about it?

Best,

John

Rice Racing's Exhaust is'nt far off the same size.

hey i was about to post that pic!



mike

nope, no joke john. nah i didn't bother calling carlos, **** CLR.

the motor is running strong as hell, i'm awaiting some repairs and i'll try to get the car on the dyno to see what square ports can do https://www.nopistons.com/forums/pub...IR#>/smile.png

i knew rice had huge ports, but i never realized they were square also. i think peter has removed the sleves though

Yeah he took the sleeves completely out

When the port opens all at once like that it creates a sharp hard pulse that will spool a larger turbo with a big ex housing faster.. and make a very loud exaust note.. https://www.nopistons.com/forums/pub...#>/biggrin.png I'd leave the bottom of the port and maybe round out the top a little, maybe bring it up 2mm in the middle and round it to the corners so the apex seal doesn't hit a flat edge when it closes.. Other than that it should work..

I am not sure where i found this pic but its a nice shape and size port.

That looks like a nice 425 ish hp engine lasts a long time port there.. lot's of apex seal ride area, not really much wider than the stock port, but up a few mm's and down a few..

I supose the Bhp depends on the Bridge and T51 bolted to it realy? LOL

what i wanna know is why they ported it so much at the bottom? the sleeve's still there so it doesn't help w/ total exhaust flow. all they did was shorten the power stroke and they didn't even gain any flow out of it.

dragon, grizley and fdracer, which port are you guys referring to? mine or that last one?

lol.. the last one.. https://www.nopistons.com/forums/pub...#>/biggrin.png



If you turn up the boost up goes the power.. :bigok:

I think He's talking about yours.. https://www.nopistons.com/forums/pub...#>/biggrin.png



the reason for this is that the whole port is not open all the time. Ie. as the rotor tip sweep across the port part of the port is still blocked, so e ven when it is closing up there is lot's of surface area to continue and channel the exaust in to the sleve. As it opens the top of the port is still closed as well and it has the same effect while opening up to dump the exaust sooner.. It's like putting huge valves in a piston engine and increasing the hell out of the duration they stay open but even then they are not opn all the way open the whole time...

that's true, but he's significantly reduced power by shortening the power stroke so much. the sleeve's still gonna be a bottleneck no matter how long your duration. in fact a smaller exhaust port would help in port velocity and would get the exhaust gas out faster. if he wanted more duration he shoulda delayed closing a touch and have a more reasonable opening time,instead of exclusively just hogging out the bottom. my thoughts would be to just take out the sleeve and just hog out the whole exhaust port like rice's.

Pulling out the sleeve isn't a good Idea on a daily driven car, When your throwing a lot of boost in to a engine there is a ton of exaust waiting to get out so exaust velocity is not a problem. The car also probably has a huge side port so they didn't go up too far due to overlap.



But yea they did go a little low... I would have waited a few more mm's before I opened up the port.

normally i'd agree pulling out the sleeve isn't a good idea, but the exhaust opening is already huge so he's already halfway there. rice racing daily drives his car so it's possible. i agree w/ you that there's a ton of exhaust waiting to get out, that's why i think the sleeve is still gonna hinder him no matter how big the exhaust opening is. eventually the sleeve's just gonna start stuffing exhaust back into the motor.

lol.. with the duration that ports got it's probably all gone before the port even thinks about closing.. https://www.nopistons.com/forums/pub...#>/biggrin.png