Drivetrain Exhaust Port Matching
Exhaust Port Matching
Guys:
As we tune and tweak for more performance the value of port matching is well known and significant. The question is, how far to take that before you reach the point of diminishing returns?
I have just received a new aftermarket header that does in fact have a 'D' shape at the head. However, upon closer inspection and alignment with the gasket there is definitely some room for improvement in the port matching. Please see the pic attached and the sharpie lines I have drawn on the flange by tracing the gasket holes. #3 is the worst, and sorry you can't really see the sharpie lines due to the flash.
Ok, just added a 2nd pic, this time without the flash, it is a little easier to see the Sharpie lines drawn.
1. Is there real value in tuning the header to better match the gasket/head?
2. A real concern would be the wall thickness of the header primaries, get too aggressive and I could have a problem by die grinding thru that wall thickness right at the flange.
Comments/Advice?
As we tune and tweak for more performance the value of port matching is well known and significant. The question is, how far to take that before you reach the point of diminishing returns?
I have just received a new aftermarket header that does in fact have a 'D' shape at the head. However, upon closer inspection and alignment with the gasket there is definitely some room for improvement in the port matching. Please see the pic attached and the sharpie lines I have drawn on the flange by tracing the gasket holes. #3 is the worst, and sorry you can't really see the sharpie lines due to the flash.
Ok, just added a 2nd pic, this time without the flash, it is a little easier to see the Sharpie lines drawn.
1. Is there real value in tuning the header to better match the gasket/head?
2. A real concern would be the wall thickness of the header primaries, get too aggressive and I could have a problem by die grinding thru that wall thickness right at the flange.
Comments/Advice?
Last edited by mini_racer; Jul 7, 2008 at 06:35 PM.
Guys:
As we tune and tweak for more performance that value of port matching is well known and significant. The question is, how far to take that before you reach the point of diminishing returns.
I have just received a new aftermarket header that does in fact have a 'D' shape at the head. However, upon closer inspection and alignment with the gasket there is definitely some room for improvement in the port matching. Please see the pic attached and the sharpie lines I have drawn on the flange by tracing the gasket holes. #3 is the worst, and sorry you can't really see the sharpie lines due to the flash.
1. Is there real value in tuning the header to better match the gasket/head?
2. A real concern would be the wall thickness of the header primaries, get too aggressive and I could have a problem by die grinding thru that wall thickness right at the flange.
Comments/Advice?
As we tune and tweak for more performance that value of port matching is well known and significant. The question is, how far to take that before you reach the point of diminishing returns.
I have just received a new aftermarket header that does in fact have a 'D' shape at the head. However, upon closer inspection and alignment with the gasket there is definitely some room for improvement in the port matching. Please see the pic attached and the sharpie lines I have drawn on the flange by tracing the gasket holes. #3 is the worst, and sorry you can't really see the sharpie lines due to the flash.
1. Is there real value in tuning the header to better match the gasket/head?
2. A real concern would be the wall thickness of the header primaries, get too aggressive and I could have a problem by die grinding thru that wall thickness right at the flange.
Comments/Advice?
Header to Head comparisons
Given that the header inlet is much larger than the head exhaust port (see pics)........it would seem that some minor tuning on the header flanges would have no value. If anything is to be adjusted, it would be the head and it would be very significant.
Conclusion, I think I will leave well enough alone........
Conclusion, I think I will leave well enough alone........
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3rd Gear
Joined: Mar 2006
Posts: 228
Likes: 0
Maybe I'm wrong, but if my me memory serves me well, the header's ports should be slightly bigger than the head's ports. Something about slowing flow and maximizing volume (Bertouli effect). Most gasket port outlines are bigger than the head's one. Use the gasket to compare both head and header. Judging by the pics you should be fine
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4th Gear
Joined: Jan 2006
Posts: 353
Likes: 0
From: Rochester, NY
Maybe I'm wrong, but if my me memory serves me well, the header's ports should be slightly bigger than the head's ports. Something about slowing flow and maximizing volume (Bertouli effect). Most gasket port outlines are bigger than the head's one. Use the gasket to compare both head and header. Judging by the pics you should be fine.
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Carbo is correct, as shown in the pics with the header gasket on the header and then on the head. Except for the pasta fluid dynamics thing, of course
The exhaust flow steps from smaller(head) to larger (header), this will help to accelerate the gas flow out of the engine. (suck it out)
The header is RMW, and ready for installation as is, it is beautiful and ready to go with absolutely no additional tuning required.
The exhaust flow steps from smaller(head) to larger (header), this will help to accelerate the gas flow out of the engine. (suck it out)
The header is RMW, and ready for installation as is, it is beautiful and ready to go with absolutely no additional tuning required.
The header is fine as is. My original misunderstanding of the flow step from head to header. See the previously attached pics.
Certainly the header at the flange does not have a perfect contour, but since it is already much larger than the head it does not matter.
Certainly the header at the flange does not have a perfect contour, but since it is already much larger than the head it does not matter.
we found that no header actually fits the ports properly of our big valve head so we designed the shorty to fit those ports. Some of those headers don't even fit stock heads properly. It has been proven to work incredible on stock heads too as it works like an anti-reversion for better scavaging. The quality of this header is superior in materials and craftmanship to what is offered .
Who actually believes round exhaust ports on a header will flow effectively on D port shaped heads?
seems this has spawned the need for "cult" status stickers....
who out there who can make these?
designs welcome
just email them to jan@revolutionmini.com for submission
You need to make sure that the "RMW Cult" is differentiated from "The Cult" (The English rock band). If not "RMW Cult" how about the RMW "R", and the word cult next to it. So it would be "R Cult"
we found that no header actually fits the ports properly of our big valve head so we designed the shorty to fit those ports. Some of those headers don't even fit stock heads properly. It has been proven to work incredible on stock heads too as it works like an anti-reversion for better scavaging. The quality of this header is superior in materials and craftmanship to what is offered .
Who actually believes round exhaust ports on a header will flow effectively on D port shaped heads?
Who actually believes round exhaust ports on a header will flow effectively on D port shaped heads?
I have no doubt about the design or the materials HOWEVER the flange openings do appear a little ruff in the pic posted. PERHAPS its the pic so why don't you post some pics yourself so we can get a good look at.
5th Gear
Joined: Aug 2007
Posts: 619
Likes: 61
From: Oxford England
nope it is rough, but would anyone really want some smaller, yet tider holes,
i was assuming the gasket would take care of it for me anyway,
i have a dremel and the time if you think it's a worth while excercise
but i see it like backing a truck into a barn or into a hanger, its the size of the doors on the truck thats the issue, being in a hanger won't get you unloaded any quicker
i was assuming the gasket would take care of it for me anyway,
i have a dremel and the time if you think it's a worth while excercise
but i see it like backing a truck into a barn or into a hanger, its the size of the doors on the truck thats the issue, being in a hanger won't get you unloaded any quicker
Banned
Joined: Oct 2006
Posts: 715
Likes: 2
we fouproperly of our big valve head so we designed the shorty to fit those pornd that no header actually fits the ports ts. Some of those headers don't even fit stock heads properly. It has been proven to work incredible on stock heads too as it works like an anti-reversion for better scavaging. The quality of this header is superior in materials and craftmanship to what is offered .
Who actually believes round exhaust ports on a header will flow effectively on D port shaped heads?
Who actually believes round exhaust ports on a header will flow effectively on D port shaped heads?
So the RMW header has redesigned physics?
"The first consideration is the proper tube diameter. Many people think "Bigger is Better", but this is not the case. The smallest diameter that will flow enough air to handle the engine's c.c. at your desired Red Line R.P.M. should be used. This small diameter will generate the velocity (air speed) needed to "Scavenge" at low R.P.M.s. If too small a diameter is used the engine will pull hard at low R.P.M.s but at some point in the higher R.P.M.s the tube will not be able to flow as much air as the engine is pumping out, and the engine will "sign off" early, not reaching its potential peak R.P.M. This situation would require going one size larger in tube diameter"
Header basisc 101 from LEADING performance header designers.
"
The second consideration is the proper tube length. The length directly controls the power band in the R.P.M. range. Longer tube lengths pull the torque down to a lower R.P.M. range. Shorter tubes move the power band up into a higher R.P.M. range. Engines that Red Line at 10,000 R.P.M. would need short tube lengths about 26" long. Engines that are torquers and Red Line at 5,500 R.P.M.s would need a tube length of 36". This is what is meant by the term "Tuned Length". The tube length is tuned to make the engine operate at a desired R.P.M. range."
This simply means that one header design does not work on all application.
So I guess you will be working on a couple of designs then ?
And I may not be reading correctly or you may not have posted where I read it but how do you get ANTI REVERSION without a stepped header or anti-reversion plates/tubes or 180? Just asking?
And I may not be reading correctly or you may not have posted where I read it but how do you get ANTI REVERSION without a stepped header or anti-reversion plates/tubes or 180? Just asking?
I know I going to get pounded for this post !
Last edited by Nitrominis; Jul 13, 2008 at 12:04 PM. Reason: added a word
2nd Gear
Joined: Jun 2008
Posts: 84
Likes: 0
From: Hanover, Pa.
I agree with Nitromonis on this. I dont have a dog in this fight, no intents to mod this car...yet.
However, I have to wonder about the engineering involved in a header that is mfgd. and looks unfinished. It does appear that very heavy flange material is used which may be good. However, the unfinished look gives me pause to consider. header design is not a simple task. Lots of design details and engineering along with dyno time involved.
Just my .02
John
However, I have to wonder about the engineering involved in a header that is mfgd. and looks unfinished. It does appear that very heavy flange material is used which may be good. However, the unfinished look gives me pause to consider. header design is not a simple task. Lots of design details and engineering along with dyno time involved.
Just my .02
John
So you are saying that a header designed for a large ported headed works equally as well on a stock port head?
So the RMW header has redesigned physics?
"The first consideration is the proper tube diameter. Many people think "Bigger is Better", but this is not the case. The smallest diameter that will flow enough air to handle the engine's c.c. at your desired Red Line R.P.M. should be used. This small diameter will generate the velocity (air speed) needed to "Scavenge" at low R.P.M.s. If too small a diameter is used the engine will pull hard at low R.P.M.s but at some point in the higher R.P.M.s the tube will not be able to flow as much air as the engine is pumping out, and the engine will "sign off" early, not reaching its potential peak R.P.M. This situation would require going one size larger in tube diameter"
Header basisc 101 from LEADING performance header designers.
"
So the RMW header has redesigned physics?
"The first consideration is the proper tube diameter. Many people think "Bigger is Better", but this is not the case. The smallest diameter that will flow enough air to handle the engine's c.c. at your desired Red Line R.P.M. should be used. This small diameter will generate the velocity (air speed) needed to "Scavenge" at low R.P.M.s. If too small a diameter is used the engine will pull hard at low R.P.M.s but at some point in the higher R.P.M.s the tube will not be able to flow as much air as the engine is pumping out, and the engine will "sign off" early, not reaching its potential peak R.P.M. This situation would require going one size larger in tube diameter"
Header basisc 101 from LEADING performance header designers.
"
The second consideration is the proper tube length. The length directly controls the power band in the R.P.M. range. Longer tube lengths pull the torque down to a lower R.P.M. range. Shorter tubes move the power band up into a higher R.P.M. range. Engines that Red Line at 10,000 R.P.M. would need short tube lengths about 26" long. Engines that are torquers and Red Line at 5,500 R.P.M.s would need a tube length of 36". This is what is meant by the term "Tuned Length". The tube length is tuned to make the engine operate at a desired R.P.M. range."
This simply means that one header design does not work on all application.
So I guess you will be working on a couple of designs then ?
And I may not be reading correctly or you may not have posted where I read it but how do you get ANTI REVERSION without a stepped header or anti-reversion plates/tubes or 180? Just asking?
And I may not be reading correctly or you may not have posted where I read it but how do you get ANTI REVERSION without a stepped header or anti-reversion plates/tubes or 180? Just asking?
I know I going to get pounded for this post !
well... well..... well......
isn't this interesting... the guy who doesn't know what a dyno looks like or a track because his Mini is "just fun"..... for the record while you were out bolting up your oval port OBX to your d-port head I was out making 8 different header combinations for the Mini Cooper S and Cooper to match all different applications. You seem to think your essay above that you stole from a book will help you prove a point.... the point is:::: YOu chose a $159 POS to put on your car
. If you were half as brilliant as you propose to be you would have designed your own header.It's easy to sit on the sidelines and post your drivel about theory.... You seem to forget I have 2 companies that have helped design the headers that are the leading exhaust manufacturers in the world. I guess it's easier to post stuff out of books than bothering to actually do it yourself....
enjoy your obx....
Banned
Joined: Oct 2006
Posts: 715
Likes: 2
well... well..... well......
isn't this interesting... the guy who doesn't know what a dyno looks like or a track because his Mini is "just fun"..... for the record while you were out bolting up your oval port OBX to your d-port head I was out making 8 different header combinations for the Mini Cooper S and Cooper to match all different applications. You seem to think your essay above that you stole from a book will help you prove a point.... the point is:::: YOu chose a $159 POS to put on your car . If you were half as brilliant as you propose to be you would have designed your own header.
It's easy to sit on the sidelines and post your drivel about theory.... You seem to forget I have 2 companies that have helped design the headers that are the leading exhaust manufacturers in the world. I guess it's easier to post stuff out of books than bothering to actually do it yourself....
enjoy your obx....
isn't this interesting... the guy who doesn't know what a dyno looks like or a track because his Mini is "just fun"..... for the record while you were out bolting up your oval port OBX to your d-port head I was out making 8 different header combinations for the Mini Cooper S and Cooper to match all different applications. You seem to think your essay above that you stole from a book will help you prove a point.... the point is:::: YOu chose a $159 POS to put on your car
. If you were half as brilliant as you propose to be you would have designed your own header.It's easy to sit on the sidelines and post your drivel about theory.... You seem to forget I have 2 companies that have helped design the headers that are the leading exhaust manufacturers in the world. I guess it's easier to post stuff out of books than bothering to actually do it yourself....
enjoy your obx....
My post was to serve to help and clarify things. For all I knew you may have more then one header available? I did at one time own an Engine Dyno (not chassis) which was in the machine shop to use for building performance engines. And for many years built my own headers. Can’t say they all work well. LOL Brilliants is not the criteria as you said but a minimum basic knowledge of thermal Dynamics and engine operation helps. But that is all past history in the 80’s
And as for the OBX design I believe I improved them a bit for street use from aprox. 35-6k? And at the time I paid 75 new for them. They were about the only game back in 2003. Since there really is not that many more choices available unless you are intending to race the Mini as your designed big tube header does? This is based on the Dyno reports you post that is always in the 7k plus. Which is not necessarily realistic on the street driven Mini? I apologize if you have a street version that I am not aware of.
As for the non-related question or comment of my avoidance to Dyno’s (POSTING) it would serve no purpose to subject myself to questions about the results. LOL however if and when I do I will choose a shop that you use so that there is no question about the results.
I choose to paste the quote, as it is the common information of performance header designer is the world so it would not be my very limited knowledge of header design. And I see now that the “my” header you phrase is actually the “2 companies that have helped design the headers that are the leading exhaust manufacturers in the world” that are designing you header not you. LOL In that case they already know the information that I used for my questions. LOL