NOOB'S GUIDE TO PORTING (56K Beware)
Rotary Freak
Joined: Oct 2001
Posts: 1,568
Likes: 2
From: N.J. USA
Originally Posted by airworks-fc3s
guys you are always talking about the importance of the "bowl"! what exactly do you mean? 'cause if i bowl the port too much on the closing side, i'm afraid to fall into the water jacket!! does nobody have any pics about this "bowl"??!!
Newbie
Joined: Mar 2007
Posts: 3
Likes: 0
From: Gainesville, GA
Killer info guys!! Great job RX7 NUT. Power is like beauty. It's in the eye of the beholder. If you port a motor the way you think it's fast, it's fast. If you port a motor the way someone else thinks it's fast, it could be a turd to you. And yeah, power is power, it wins races, blah blah blah... Great work though. There's alot of mis-led info and bs talking on most sites. Thankyou for being the bigger man and stepping up.
John
John
Full Member
Joined: Nov 2003
Posts: 192
Likes: 8
From: .
Originally Posted by RacerXtreme7
VELOCITY VELOCITY VELOCITY!!!!! up until it holds flow back..... THATS what makes power.
~Mike....................
~Mike....................
Often overlooked and not very well understood.
Originally Posted by Blake
Here is a more finished bowl for comparrison. This is a scondary port and the other a primary port, but the principle is the same.
Rotary Freak
Joined: Aug 2001
Posts: 2,267
Likes: 3
Originally Posted by djseven
What type of bit are you using to leave the mirror finish? And what steps are you taking to get it there in what order? Sanding bit, Flap wheel,etc???
For intake porting, the top ones are my favorites. Mainly double-cut carbide olives of various sizes, followed by cartridge rolls of a couple different grits, followed by a flapper with a couple grits. I like to take it all the way to a mirror finish to evaluate the smoothness of the port shape, fix any waves or other irregularities, smooth it back out, then go back and rough-up the bowl of the port slightly to encourage a small turbulent boundary layer on the outside radius.
Thread Starter
Joined: Aug 2002
Posts: 2,828
Likes: 1
From: Houston Tx
It is nice to see this thread helping so many people, Direct and In-Direct. We really need to get this thread changed to a Sticky.
Can you help this out SPEED_NYC
Can you help this out SPEED_NYC
Originally Posted by Blake
These are the bits I generally use.
For intake porting, the top ones are my favorites. Mainly double-cut carbide olives of various sizes, followed by cartridge rolls of a couple different grits, followed by a flapper with a couple grits. I like to take it all the way to a mirror finish to evaluate the smoothness of the port shape, fix any waves or other irregularities, smooth it back out, then go back and rough-up the bowl of the port slightly to encourage a small turbulent boundary layer on the outside radius.
For intake porting, the top ones are my favorites. Mainly double-cut carbide olives of various sizes, followed by cartridge rolls of a couple different grits, followed by a flapper with a couple grits. I like to take it all the way to a mirror finish to evaluate the smoothness of the port shape, fix any waves or other irregularities, smooth it back out, then go back and rough-up the bowl of the port slightly to encourage a small turbulent boundary layer on the outside radius.
Thanks for the info. Exactly what I was looking for.
Full Member
Joined: Oct 2005
Posts: 157
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From: England
really interesting thread.
Quick question on the exhaust port, for a Turbo'd series 5 or 6 engine, how close to the edge of the rotor housing and how high or low can you go.
I have managed to open up the exhaust sleeves so i can make the port a lot larger than stock but some people say dont go up on the port and others say dont go down. Is there a definative answer??
Quick question on the exhaust port, for a Turbo'd series 5 or 6 engine, how close to the edge of the rotor housing and how high or low can you go.
I have managed to open up the exhaust sleeves so i can make the port a lot larger than stock but some people say dont go up on the port and others say dont go down. Is there a definative answer??
Full Member
Joined: Oct 2005
Posts: 157
Likes: 0
From: England
really interesting thread.
Quick question on the exhaust port, for a Turbo'd series 5 or 6 engine, how close to the edge of the rotor housing and how high or low can you go.
I have managed to open up the exhaust sleeves so i can make the port a lot larger than stock but some people say dont go up on the port and others say dont go down. Is there a definative answer??
Quick question on the exhaust port, for a Turbo'd series 5 or 6 engine, how close to the edge of the rotor housing and how high or low can you go.
I have managed to open up the exhaust sleeves so i can make the port a lot larger than stock but some people say dont go up on the port and others say dont go down. Is there a definative answer??
Rotary Freak
Joined: Aug 2001
Posts: 2,267
Likes: 3
Originally Posted by antnicuk
really interesting thread.
Quick question on the exhaust port, for a Turbo'd series 5 or 6 engine, how close to the edge of the rotor housing and how high or low can you go.
I have managed to open up the exhaust sleeves so i can make the port a lot larger than stock but some people say dont go up on the port and others say dont go down. Is there a definative answer??
Quick question on the exhaust port, for a Turbo'd series 5 or 6 engine, how close to the edge of the rotor housing and how high or low can you go.
I have managed to open up the exhaust sleeves so i can make the port a lot larger than stock but some people say dont go up on the port and others say dont go down. Is there a definative answer??
On turbo cars, we tend to port the exhaust down a little bit. This seems to help pre-spool the turbo(s) by raising EGTs. We also generally stick to a "shovel" profile to open the exhaust port quickly rather than progressively. On the closing side, we hardly touch timing at all. Maybe a millimeter or two, but that's it. The issues are overlap and port duration. As for width, we don't change it at all because we don't want the apex seals bowing in. The factory seals are definitely stronger than the aftermarket metallic seals but any seal striking of the closing side is bad. For aftermarket metallic seals, you MUST bevel the closing edge of the port because seal strike is virtually inevitable due to the lower beam strength. Still a good idea for the factory seal, but more a matter of form than necessity. The overall shape of the turbo ports will tend to be square. This maximizes volume while minimizing timing. It also gives the exhaust a "square wave" pressure signal, as opposed to a more "sine wave" of a rounded port. This has advantages wrt evacuation of the chamber improving VE. We don't like this profile so much with non-turbo engines because it is very LOUD. Also, we always leave a step on the lower lip for anti-reversion.
There are many other ways to skin the cat, so don't think this is the "right" way, but it is an approach that we have found works well for us.
Full Member
Joined: Oct 2005
Posts: 157
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From: England
Hi
thanks for your reply,
I am currently building a new engine for my Series 5 TII, I had done the exhaust ports already and made them square as i thought it would get the largest area so i'm glad about that. I did go a little wider each side, i'm about 12mm in from each side although i am using new Mazda 2 piece seals, do you think this would be ok?
Some have said i shouldnt go down because it shortens the power stroke and others have said dont go up due to overlap. I live in the UK and this was advice from 2 specialists i have known for a long time! Due to the doubt, i ported about 2mm down and 4 mm up. I retained the exhaust sleeve but took it out, heated it and splayed the opening so it matches the port in the housing, this way i managed to retain the sleeve but dont have a step between the sleeve and the port opening. The inlet ports are quite a large streetport as are the runners and the Lower inlet manifold.
What do you think? do you keep the sleeve
I currently run a S4 engine with Low comp rotors and a GT35/40 with a 0.96 hot side, the engine was dynoed at 380 RWhp with little lag, i am aiming for 400 RW hp at 1 bar with the new one so i have done a lot more porting and got a 1.15 exhaust housing, hopefully it wont be too laggy. This one will use S 5 rotors and FD e shaft, s gears and oil pressure regs as i want to reve it to 8 k rpm safely
regards
tony
thanks for your reply,
I am currently building a new engine for my Series 5 TII, I had done the exhaust ports already and made them square as i thought it would get the largest area so i'm glad about that. I did go a little wider each side, i'm about 12mm in from each side although i am using new Mazda 2 piece seals, do you think this would be ok?
Some have said i shouldnt go down because it shortens the power stroke and others have said dont go up due to overlap. I live in the UK and this was advice from 2 specialists i have known for a long time! Due to the doubt, i ported about 2mm down and 4 mm up. I retained the exhaust sleeve but took it out, heated it and splayed the opening so it matches the port in the housing, this way i managed to retain the sleeve but dont have a step between the sleeve and the port opening. The inlet ports are quite a large streetport as are the runners and the Lower inlet manifold.
What do you think? do you keep the sleeve
I currently run a S4 engine with Low comp rotors and a GT35/40 with a 0.96 hot side, the engine was dynoed at 380 RWhp with little lag, i am aiming for 400 RW hp at 1 bar with the new one so i have done a lot more porting and got a 1.15 exhaust housing, hopefully it wont be too laggy. This one will use S 5 rotors and FD e shaft, s gears and oil pressure regs as i want to reve it to 8 k rpm safely
regards
tony
I'm sorry wha?
Joined: Aug 2003
Posts: 1,098
Likes: 1
From: Wisconsin
dude awsoem thread. I will probably have to rebuild my engine soon becasue of a noob mistake abotu 1.5 years back, and I figured that this time aroudn I would give porting a shot. This definitely pushes me in that direction. You guys are awsoem for posting all of this. btw I was just wondering Does this mean that Porting the lower intake manifold is a must as well?
