Half Bridge Questions

[matt p]

Big thumbs up for the info shared in this thread.

Nice one guys

[PGiljevic]

Could port timing be increased on a stock port engine by chamfering/scalloping the sides of the rotor? To give earlier inlet opening and closing allowing more air in on stock ports?

Yes I have done that to many motors, when I get a chance I will put up the exact port timing (open close and overlap period) of such a modification. I do this to both opening and closing edges on my rotors, this puts this type of mod between a semi bridge and full bridge in terms of (overlap to exhaust sensitivity) but gives the engine more top end when combined with a street port of the style I do. :yes

What you also need to consider on all of the race porting principles is the area to crank angle relationship as well, this is real important when selecting the type you want to use (given exhaust restriction limits you are forced to comply with these days).

Interesting topic for sure, mostly made totally redundant by the advent of turbochargers and peoples ability to use them correctly though.

[Grant Monkhouse]

yes it made  slightly irrelevant by turbos, i wonder what a supercharged ported engine would like as there isnt a turbo int the way to stop the exhaust escaping??
 
would you say scallopped rotors would work on the engine you are currently putting through extensive testing at ever incresing and amazing bost levels?
 
the way i see scalloped rotors is through the similarities of a piston ported 2 stroke engine, of which my dad knows a hell of a lot about and try to ask him questions about 2 stroke workings all the time as they are an amazing piece of engine.

[Grant Monkhouse]

just had anothe thought, could the exhaust be ported out to sides? you would not be changing the timing of the ports opening and closing so would the engine benefit from increased gas flow but no suffer from loud over lap brapping???
 
hmmmm?? im glad a have a huge imagination for these type of questions. why on earth i became an electrician i dont know. should have got into engines!!
 
oh i know why im an electrician.... the money!

[PGiljevic]

Scalloped rotors are more aggressive in timing compared to a street port and have even more overlap (but no two people do things the same) the same negatives of overlap apply, so it is easy to go backwards.

To be brutally honest with you it is so hard to not gag over the stock std 13B-REW port timing (again we are talking turbocharged) where you can very easily gain the few percent a compromised "port" will give you just by the simple addition of boost (small increases over it) I talked about this at length in one of the other threads where I put up an example of one customer who lives in the UK now with his stock port V\'s a ported example and keeping all other variables in check and only altering boost.

It\'s hard to cater for all peoples taste and objectives in a simple internet posting like here (some are all out racers!, others street racers, others just want a bit more urge over stock) so take from the discussion what you will.

All I know is that in RICESP it\'s a total f7cken ANIMAL :burnout it twists the chassis on acceleartion, wants to slip the twin plate carbon clutch in 3rd gear!, it accelerates as hard as a full bridge port T51 set up running a almost race exhaust. < So from my persepctive cause I live with a car and run many examples I cant quite comprehend why people still are looking for the porting nirvana when its a total non issue once you learn to optimise the set up that Mazda gave you. :Thumbsup! :3Confused I really did not want to even contimplate running a non street ported engine with my special rotors, but given I sell more stock std engines than modified ones I wanted to find out myself just how fast a stock std 13B-REW can be, and I am glad I took the time out to replicate the results I got form others many many years ago in my own test bed with all the data logging advancement since then. It\'s also great to be able to show people first hand what a stock std engine can do, most people dont believe you :rolleyes: which is fine, I guess I would not either if it was a one off, but having repeated it many times now over a large span of time I am more of a believer in stock is best for the street (by a long way) and even stock is best for ANY car (all kinds of hobby motorsport activities) running a normal syncromesh gearbox as well.