Exhaust port timings? can someone confirm?
 

Is anyone able to confirm some timings for me? I've done my exhaust ports and just been measuring the timing to make sure I havn't gone too far early. My hair brained thoughts are that I want them to open up earlier to help spool the turbo sooner with higher EGTs,etc. I'm not massively bothered about top end and don't want to sacrifice mid range so I've only gone a little bit upwards so I don't get much more overlap with the intake ports. I've got an Apexi Rx6 turbo kit to go on and hoping for around 400ish bhp. I did have a much bigger turbo before the engine blew but the car is a drifter now so looking for more balanced track sort of setup.
I'm toying with the idea of going more extreme and doing a half bridge but want to read up more on the effect of the overlap on a turbo engine. If it was an NA I wouldn't want it but it seems that the overlap doesn't effect midrange as much with a turbo? could be wrong?? anyhow...

I've got them opening up at 84 deg BBDC which (luckily!) is the same as Racing Beat do their street ports so thats good because I was worried I'd gone a bit far hence getting out the protractor!

The part thats confusing me is the exhaust closing time. I've only gone up a millimeter ish so hardly changed it from stock at all. I'm measuring it as 58 degrees ATDC. According to the article above the stock ports are 48 ATDC and the racing beat street ports are the same. If anyone could measure it for me that would be most greatness! even if you just measure up the housing and I'll convert if to degrees myself with my amazing contraption here :D

http://i13.photobucket.com/albums/a2...l/IMG00363.jpg
Super professional protractor looks just like a cd with cardboard stuck to it :scratch:
http://i13.photobucket.com/albums/a2...l/IMG00367.jpg

Bump! no one? :(

hmmm
 

well i dont know about all the timing degrees and all but i do know from experience that overlap sounds nice but your going to get better top end but dirty boosted intake air. when there is overlap the exhaust goes into the intake its not too bad on a n/a car but on a boosted car your going to have boosted exhaust pressure ram into the intake. i have found good luck with porting the intake farther up and to the right or rotor porting witch does the same and then bringing the exhaust port downward which made my turbo spool great since it still had alot of energy going out of the exhaust port and you get faster revs by doing this also i really dont know if this helps but i thought i would explain what i have tested

Thanks for the reply, really appreciate it. The stuff about opening the exhaust earlier and closing the intake later is exactly what I'm doing so its really good to hear its worked for someone and that you did it for the same reasons. I think I'm going to go ahead with it as it is and give it a go. Worst case I'll have to rebuild with some different housings if its real bad!! I'll be careful to keep an eye out for too high EGTs, only thing I can think of that could be adversly effected by opening the exhaust earlier. I've got a ball bearing apexi rx6 turbo kit so the center housing is happy with higher EGTs :) Hopefully it will actually work, if not back to the drawing board!

thanks
 

good old washer fluid helps keep things cool

Good point :) I've got a WI kit here.