what type of port should i use?
06-01-13, 12:39 AM
#1
what type of port should i use?
ok, so im going to rebuild my engine, just trying to decide on what port to use... im going to run a little boost, and the car will be driven in the city and on the dragon most of the time. i want something that is somewhat "streetable" yet i want to build a pretty quick car, lol...
im kinda afraid to go with a full bridge port, but ive heard of half-bridge ports and my buddy was saying something about drilling??? he used to have an fb and he said that when he built his motor, they drilled like 3 or 4 small holes in the place of a bridge port.
or should i just leave bridge porting alone and go with a mild/street port? just brainstorming at the moment lol
im kinda afraid to go with a full bridge port, but ive heard of half-bridge ports and my buddy was saying something about drilling??? he used to have an fb and he said that when he built his motor, they drilled like 3 or 4 small holes in the place of a bridge port.
or should i just leave bridge porting alone and go with a mild/street port? just brainstorming at the moment lol
06-01-13, 12:54 AM
#2
Old [Sch|F]ool
I've had half bridge and full bridge. IMO if you're going to do that, go all the way. No half bridge, no half-height nonsense, it's going to have about the same drivability no matter what, You can't drive it like a street port, doing things like coasting in gear. I've got mine tuned to where it's pretty tame to drive on the street, is quieter than either of my VWs to the point where it's my preferred long-trip car, gets shockingly good fuel economy (about 22-25 mixed, with a current high of 28-29mpg) and is generally not the hideous undrivable painful to live with beast that people make them out to be.
But it's still not for everyone.
If you are going to have a turbo, I'd just go with a mild street port. Exhaust becomes absolutely critical if you have any kind of bridge port, and playing turbine wheel/housing science experiment can get expensive in a hurry...
But it's still not for everyone.
If you are going to have a turbo, I'd just go with a mild street port. Exhaust becomes absolutely critical if you have any kind of bridge port, and playing turbine wheel/housing science experiment can get expensive in a hurry...
06-01-13, 03:07 PM
#6
Moderator
iTrader: (3)
Join Date: Mar 2001
Location: https://www2.mazda.com/en/100th/
Posts: 31,145
Received 2,799 Likes
on
1,981 Posts
with the turbo, stock or street port is the way to go.
Trending Topics
06-01-13, 10:17 PM
#8
well, I sort of stated it poorly, because I didn't really mean to imply that it's just the exhaust porting. rather it's the overall airflow through the engine. what I was hinting at when I said manipulation was using some overlap to help spool. think of what bridges would do with a turbo of the same size, but to a lesser degree.
06-02-13, 03:37 PM
#19
ok.. lol i know where tdc and bdc are, but "opens a __* BTDC or ATDC" is kinda where i get confused.. does that mean for the irons that the face or the rotor begins to pass over the intake port? and im assuming the exhaust closes when the apex seal passes the end of the exhaust port.
06-02-13, 10:21 PM
#22
74 spec is the same as T2 and FD secondaries. 50° port close timing. Food for thought.
More food for thought is how much smaller T2 and FD primaries are than your 12A. They are small for greater velocity at low RPM so the fuel injectors work right. You however have a 12A and you can port all four to T2/FD secondary size (saem as 74 spec) with zero penalties. That is a lot more total intake port area than the T2 and FD guys can get away with.
More food for thought is how much smaller T2 and FD primaries are than your 12A. They are small for greater velocity at low RPM so the fuel injectors work right. You however have a 12A and you can port all four to T2/FD secondary size (saem as 74 spec) with zero penalties. That is a lot more total intake port area than the T2 and FD guys can get away with.
06-03-13, 11:54 AM
#23
74 spec is the same as T2 and FD secondaries. 50° port close timing. Food for thought.
More food for thought is how much smaller T2 and FD primaries are than your 12A. They are small for greater velocity at low RPM so the fuel injectors work right. You however have a 12A and you can port all four to T2/FD secondary size (saem as 74 spec) with zero penalties. That is a lot more total intake port area than the T2 and FD guys can get away with.
More food for thought is how much smaller T2 and FD primaries are than your 12A. They are small for greater velocity at low RPM so the fuel injectors work right. You however have a 12A and you can port all four to T2/FD secondary size (saem as 74 spec) with zero penalties. That is a lot more total intake port area than the T2 and FD guys can get away with.
06-03-13, 12:37 PM
#24
Don't ask me. I had access to a genuine 74 side plate (look for 3B in raised letters on the casting). Then I made a paper template. If you compare the delayed closing of 74 to the early closing of a stock 12A, you'll see what I'm talking about. Then just port up to the closing line of the 74 port on all four and you're done. Well, you DO have to know HOW to port in order to get decent results. Ever ported before?
If you don't have a real 3B iron kicking around, just get any T2 or FD end plate and make your template from that. However the very bottom is going to differ. You can ignore it as there is like no flow or very little flow down there. It was a change Mazda made on all 86 and later engines.
If you don't have a real 3B iron kicking around, just get any T2 or FD end plate and make your template from that. However the very bottom is going to differ. You can ignore it as there is like no flow or very little flow down there. It was a change Mazda made on all 86 and later engines.
