speaking of exhaust systems...someone else promised dynos back in Early December....
12-28-2006, 06:34 AM
#2
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Not yet, going to GMG soon
Unfortunately, MagnaFlow has not pursued this much...they've been busy with holiday rush stuff.
I'm going to GMG soon for a bunch of other stuff, so I'll have some dyno numbers then,
Stay tuned.
In theory, since Milltek's system does not use an x pipe crossover, and based on other system's results and seat of the pants evaluations, I'm betting that the MagnaFlow will show a 20-25hp increase, but that's just speculation.
I'm going to GMG soon for a bunch of other stuff, so I'll have some dyno numbers then,
Stay tuned.
In theory, since Milltek's system does not use an x pipe crossover, and based on other system's results and seat of the pants evaluations, I'm betting that the MagnaFlow will show a 20-25hp increase, but that's just speculation.
12-28-2006, 01:11 PM
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No photo, but there is a video
Click here to watch the video, taken on my RS4 by a German TV show that was here filming in November<ul><li><a href="http://www.youtube.com/watch?v=zMoztOtiXeY">http://www.youtube.com/watch?v=zMoztOtiXeY</a</li></ul>
12-28-2006, 01:17 PM
#6
Oh ... there's an X Pipe crossover in the MagnaFlow RS4 exhaust (long and really geeky)
First, I have to apologize for the way I've thought about MagnaFlow, and yourself. Although I've never expressed it, I thought, probably like many here, that your exuberance about MagnaFlow catbacks on the RS4 was colored by the fact that you work for them. (The term, "MagnaFlow Shill" came to mind.) I figured that there was no way that the MagnaFlow catback could be much better than anything else, and so, tended to disregard most of what you've said in that regard. However, you do have quite a bit of experience as a high performance auto enthusiast, so I have tried to keep an open mind.
It may be because I've not been listening, or not been fully engaged, but this is the 1st time I've understood that the MagnaFlow RS4 exhaust system uses an X Pipe Crossover. Interestingly enough, even the MagnaFlow website does not really do justice to the technology. Since I've recently gone from an "Oil Research" to an "Exhaust Research" phase (I'm AADD, and can never keep focused on one thing for too long!), I've got a pretty good understanding of how and why good exhaust systems work. It took me about 10 minutes to "grok" why the MagnaFlow system has the potential for being the best RS4 catback system out there. So, I'm going to be doing a bit of, as Ricky Ricardo says, 'splainin for the benefit of everyone on the board.
I happen to be a flow expert of a different sort. My expertise is in Applied Electromagnetics. Quite a bit of what I do on a daily basis is to optimize high speed electronic interconnect. Interestingly enough, as I've started studying engine exhaust systems, I've realized that pulse flow dynamics (as seen in automobile exhaust systems) is mathematically identical to electronic transmission lines used in pulsed communication systems (i.e. - electronic computers, internet switches ....) As a result, it's been fairly easy for me to understand what makes a good and a bad exhaust system.
The interesting thing about 90 degree V8 engines is the firing order. It is asymmetric. If you look at the firing order for the RS4 V8, for example, it is 1,5,4,8,6,3,7,2, with a cylinder firing every 90 degrees of crankshaft rotation. For every two crank rotations, 720 degrees, there are 8 exhaust pulses that are evenly spaced in time.
However, if you look at the firing order for each cylinder bank, you see something different.
For one bank it is:
1,X,4,X,X,3,X,2
For the other bank it is:
X,5,X,8,6,X,7,X
Where X is a 90 degree interval where no cylinder fires on that bank.
Now, if we place these together in time, and extend them across 4 crank rotations we get:
1,X,4,X,X,3,X,2,1,X,4,X,X,3,X,2
X,5,X,8,6,X,7,X,X,5,X,8,6,X,7,X
What you'll see is that for both banks, the firing order throughout two crank rotations is not uniform. That "interesting" firing order gives a dual-exhaust V8 it's unique burble.
Da -- Da -- -- Da -- Da Da -- Da -- -- Da -- Da Da -- on one pipe
-- Da -- Da Da -- Da -- -- Da -- Da Da -- Da -- -- Da on the other pipe
Exhaust does not come out of the engine in a stream, but rather as pulses. You can feel the pulses by placing your hand at the end of the exhaust tip. However, by the time exhaust pulses get down to the end of the exhaust pipe, internal pipe and baffle friction causes the pulse to disperse and widen over time. This causes closely spaced pulses to partially combine. For example pulses 2,1 and 8,6, that are only phased by 90 degrees of crank rotation, combine partially, both filling the exhaust pipe and muffler simultaneously. This causes the pressure to increase, which then reflects back towards the engine, impeding flow. There is also a period of 180 degrees every two engine rotations where no exhaust pulses originate from the bank.
If we look at exhaust flow like a train track, there are periods of time on each bank where the tracks are crowded, and periods of time when the tracks are empty. If this were a railroad, with two sets of tracks (like the two banks of exhaust), we might exercise some flow control by using a crossover switch, to even out the traffic volume. If we take both banks as a whole, it's easy to see that there is no overlap, and exhaust energy could be switched from one pipe to the other, during free periods, to relieve back pressure due to overlap. Well, this is kind of how the MagneFlow X Pipe Crossover works. Unfortunately, the train track analogy is not quite correct, since the train moves in only one direction, but anyone who has worked with fluids knows that fluids flow across all branches of a pipe, and not just in one preferred direction.
If it is implemented well, a crossover can even flow across the two exhaust pipes, but it's not 100% efficient. Each exhaust pulse from each bank is split to both pipes. In theory, each exhaust pulse splits four-ways at the crossover. Some of the pulse continues to travel down the same bank tail pipe. Some of the pulse travels down the opposite bank tail pipe. Some of the pulse travels around to the opposite bank downpipe. And some of the pulse reflects back to the same bank downpipe, as negative backpressure (vacuum). If timed correctly, the reflected exhaust pulse can provide some scavenging for the next exhaust port opening. But this is pretty iffy, since it is dependent upon the design of the total exhaust system from exhaust ports through the headers and down tubes. If the downstream tube diameter is larger than the upstream tube diameter, a larger percentage of the total exhaust pulse charge will be transmitted out the exhaust pipes. The closer the crossover is placed to the down tube junction, the closer it will approximate an 8-4-2-1 exhaust system, where all the ports are fed into one header, and the better any potential scavenging. If placed near low flow stock cat downpipes, the downpipes will keep any crossover exhaust from passing back up to the engine. But, with high flow cats and downpipes, it's possible that the crossover could cause exhaust flow interference, if placed or designed incorrectly.
At this point, whether or not MagnaFlow catbacks with X Pipe Crossovers will improve performance more so than conventional catbacks is debatable, but still possible. If the the crossover design and placement is correct for the RS4, and if everything else were even in the rest of the exhaust system, (pipe diameter, muffler flow ....), then my SWAG is that the X pipe will provide improvements for the 2,1 and 8,6 exhaust flow, which comprises about 25% of the exhaust volume. Since the overlap is about 1/2 of that, theres a potential for 12.5% flow improvement, if the crossover is 100% efficient. However, I expect the efficiency to be somewhere around 70%, for a total flow improvement of 8.75%. Dyno testing of the Milltek solution is showing around 20 HP performance improvement for non-res catback alone. If my educated guesses are right, I'd expect to see about 20 x 1.0875 = 22 HP with the MagnaFlow system. Any other gains would be most likely due to the increased Magnaflow muffler flow.
Of course, I could be totally full of crap, too! Like everyone else, I look forward to your dyno runs, Craig.
It may be because I've not been listening, or not been fully engaged, but this is the 1st time I've understood that the MagnaFlow RS4 exhaust system uses an X Pipe Crossover. Interestingly enough, even the MagnaFlow website does not really do justice to the technology. Since I've recently gone from an "Oil Research" to an "Exhaust Research" phase (I'm AADD, and can never keep focused on one thing for too long!), I've got a pretty good understanding of how and why good exhaust systems work. It took me about 10 minutes to "grok" why the MagnaFlow system has the potential for being the best RS4 catback system out there. So, I'm going to be doing a bit of, as Ricky Ricardo says, 'splainin for the benefit of everyone on the board.
I happen to be a flow expert of a different sort. My expertise is in Applied Electromagnetics. Quite a bit of what I do on a daily basis is to optimize high speed electronic interconnect. Interestingly enough, as I've started studying engine exhaust systems, I've realized that pulse flow dynamics (as seen in automobile exhaust systems) is mathematically identical to electronic transmission lines used in pulsed communication systems (i.e. - electronic computers, internet switches ....) As a result, it's been fairly easy for me to understand what makes a good and a bad exhaust system.
The interesting thing about 90 degree V8 engines is the firing order. It is asymmetric. If you look at the firing order for the RS4 V8, for example, it is 1,5,4,8,6,3,7,2, with a cylinder firing every 90 degrees of crankshaft rotation. For every two crank rotations, 720 degrees, there are 8 exhaust pulses that are evenly spaced in time.
However, if you look at the firing order for each cylinder bank, you see something different.
For one bank it is:
1,X,4,X,X,3,X,2
For the other bank it is:
X,5,X,8,6,X,7,X
Where X is a 90 degree interval where no cylinder fires on that bank.
Now, if we place these together in time, and extend them across 4 crank rotations we get:
1,X,4,X,X,3,X,2,1,X,4,X,X,3,X,2
X,5,X,8,6,X,7,X,X,5,X,8,6,X,7,X
What you'll see is that for both banks, the firing order throughout two crank rotations is not uniform. That "interesting" firing order gives a dual-exhaust V8 it's unique burble.
Da -- Da -- -- Da -- Da Da -- Da -- -- Da -- Da Da -- on one pipe
-- Da -- Da Da -- Da -- -- Da -- Da Da -- Da -- -- Da on the other pipe
Exhaust does not come out of the engine in a stream, but rather as pulses. You can feel the pulses by placing your hand at the end of the exhaust tip. However, by the time exhaust pulses get down to the end of the exhaust pipe, internal pipe and baffle friction causes the pulse to disperse and widen over time. This causes closely spaced pulses to partially combine. For example pulses 2,1 and 8,6, that are only phased by 90 degrees of crank rotation, combine partially, both filling the exhaust pipe and muffler simultaneously. This causes the pressure to increase, which then reflects back towards the engine, impeding flow. There is also a period of 180 degrees every two engine rotations where no exhaust pulses originate from the bank.
If we look at exhaust flow like a train track, there are periods of time on each bank where the tracks are crowded, and periods of time when the tracks are empty. If this were a railroad, with two sets of tracks (like the two banks of exhaust), we might exercise some flow control by using a crossover switch, to even out the traffic volume. If we take both banks as a whole, it's easy to see that there is no overlap, and exhaust energy could be switched from one pipe to the other, during free periods, to relieve back pressure due to overlap. Well, this is kind of how the MagneFlow X Pipe Crossover works. Unfortunately, the train track analogy is not quite correct, since the train moves in only one direction, but anyone who has worked with fluids knows that fluids flow across all branches of a pipe, and not just in one preferred direction.
If it is implemented well, a crossover can even flow across the two exhaust pipes, but it's not 100% efficient. Each exhaust pulse from each bank is split to both pipes. In theory, each exhaust pulse splits four-ways at the crossover. Some of the pulse continues to travel down the same bank tail pipe. Some of the pulse travels down the opposite bank tail pipe. Some of the pulse travels around to the opposite bank downpipe. And some of the pulse reflects back to the same bank downpipe, as negative backpressure (vacuum). If timed correctly, the reflected exhaust pulse can provide some scavenging for the next exhaust port opening. But this is pretty iffy, since it is dependent upon the design of the total exhaust system from exhaust ports through the headers and down tubes. If the downstream tube diameter is larger than the upstream tube diameter, a larger percentage of the total exhaust pulse charge will be transmitted out the exhaust pipes. The closer the crossover is placed to the down tube junction, the closer it will approximate an 8-4-2-1 exhaust system, where all the ports are fed into one header, and the better any potential scavenging. If placed near low flow stock cat downpipes, the downpipes will keep any crossover exhaust from passing back up to the engine. But, with high flow cats and downpipes, it's possible that the crossover could cause exhaust flow interference, if placed or designed incorrectly.
At this point, whether or not MagnaFlow catbacks with X Pipe Crossovers will improve performance more so than conventional catbacks is debatable, but still possible. If the the crossover design and placement is correct for the RS4, and if everything else were even in the rest of the exhaust system, (pipe diameter, muffler flow ....), then my SWAG is that the X pipe will provide improvements for the 2,1 and 8,6 exhaust flow, which comprises about 25% of the exhaust volume. Since the overlap is about 1/2 of that, theres a potential for 12.5% flow improvement, if the crossover is 100% efficient. However, I expect the efficiency to be somewhere around 70%, for a total flow improvement of 8.75%. Dyno testing of the Milltek solution is showing around 20 HP performance improvement for non-res catback alone. If my educated guesses are right, I'd expect to see about 20 x 1.0875 = 22 HP with the MagnaFlow system. Any other gains would be most likely due to the increased Magnaflow muffler flow.
Of course, I could be totally full of crap, too! Like everyone else, I look forward to your dyno runs, Craig.
12-28-2006, 01:20 PM
#7
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Not to my knowledge...
I think we've touched upon this before, but I'll recap for those who missed the discussion:
In MagnaFlow's eyes, oval tips are not desirable because:
They are only available in "single" wall...single walled tips discolor and turn brown rapidly. Since MagnaFlow warranties their products for life, they did not want to be troubled by people returning systems for golden/browned tips.
Most people want an exhaust system that does not appear stock...it made little sense to them that they would be able to sell a system that looked, for all intents and purposes, exactly like the stock RS4 system. It's not this way with any other vehicle and frankly, MagnaFlow people were astonished to learn that anyone desired this configuration.
The stock system has an oval tip, but has two outlets coming from a muffler that has a single inlet. This muffler and dual outlet configuration hampers power, which is why MagnaFlow went another way. Milltek didn't use this configuration in their setup, but they did have to find a way to make an oval tip work. FYI: they don't make their own tips either, they buy them from a vendor, just as MagnaFlow does.
Last but not least, I can appreciate that some people are adamant that they want an oval tip...I don't blame them a bit and I understand their approach.
However, with the money you save on a MagnaFlow (which will be literally hundreds of dollars), if you really have to have an oval tip, all I can do is suggest that you buy one from some place else and have your shop graft it on.
I think I've done all I can to share my sentiments with my bosses at MagnaFlow, and if there was a way to make one work and still live up to the high quality standards the company maintains, it would be done.
Right now, I'm focusing on dyno validating the system independently to put to rest any concerns consumers may have as to the power it produces.
In MagnaFlow's eyes, oval tips are not desirable because:
They are only available in "single" wall...single walled tips discolor and turn brown rapidly. Since MagnaFlow warranties their products for life, they did not want to be troubled by people returning systems for golden/browned tips.
Most people want an exhaust system that does not appear stock...it made little sense to them that they would be able to sell a system that looked, for all intents and purposes, exactly like the stock RS4 system. It's not this way with any other vehicle and frankly, MagnaFlow people were astonished to learn that anyone desired this configuration.
The stock system has an oval tip, but has two outlets coming from a muffler that has a single inlet. This muffler and dual outlet configuration hampers power, which is why MagnaFlow went another way. Milltek didn't use this configuration in their setup, but they did have to find a way to make an oval tip work. FYI: they don't make their own tips either, they buy them from a vendor, just as MagnaFlow does.
Last but not least, I can appreciate that some people are adamant that they want an oval tip...I don't blame them a bit and I understand their approach.
However, with the money you save on a MagnaFlow (which will be literally hundreds of dollars), if you really have to have an oval tip, all I can do is suggest that you buy one from some place else and have your shop graft it on.
I think I've done all I can to share my sentiments with my bosses at MagnaFlow, and if there was a way to make one work and still live up to the high quality standards the company maintains, it would be done.
Right now, I'm focusing on dyno validating the system independently to put to rest any concerns consumers may have as to the power it produces.
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12-28-2006, 01:23 PM
#8
Thanks Craig
Unfortunately it doesn't show the exhaust system configuration well. But that is a nice exhaust note. One of the things I didn't point out in my geeky post above, is that the X Pipe Crossover will remove that V8 dual-pipe burble, which has a lower frequency component. The Magnaflow exhaust will sound more like an F1 engine, with a fully unified exhaust ... and it does.
12-28-2006, 01:31 PM
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A scholar, a gentleman, and a confession...more inside
Your thread is spot on. Very well done. Although I'm not even remotely the exhaust genius our guy Richard Waitas is (he works for MagnaFlow), I've heard his speeches on this topic and much of what you assert was corroborated by Richard's discussions.
In short, while I could not tell you why an X is better than an H in great detail, I can tell you that it is indeed, better.
Is it 2hp better than the rival Milltek? 5hp? Time will tell, but previous experience suggests that it is a few percentage points better, but the dyno numbers should help a bit.
What we really need is back to back comparisons at GMG on the same car....let the chips fall where they may and I'm sure both Milltek's and MagnaFlow's will perform as advertised.
With that said....I've been in this business 22 years and I LIKE TO THINK that I have a reputation for being honest...brutally honest.
If our system sucked, or didn't deliver as advertised, or was in some other way inferior, inadequate, or would reflect poorly on me as an individual, I simply wouldn't talk about it all.
I make nothing from it's sale...not a nickel of commission, not a promotion, nothing.
Frankly, while the point of our tips has been repeatedly debated and I've stated the company's position publicly, privately, my opinion is that I love the dual twin tips, but I wish they were bigger. Just my opinion. It doesn't make the MagnaFlow system better, worse, worth more, worth less, just different.
Ultimately, consumers will decide with their pocketbook.
I am SINCERELY appreciative of all the feedback I get here on this product, as I pass it along. Whether or not the company will change it's views remains to be seen, but ultimately, I'm here to share RS4 experiences, not to defend a position or further someone's agenda.
I've posted tidbits on the RS4 system because I wanted to help the Rs4 community. I did the same on the M3 boards, the Mercedes Benz CLK and SL forums, the Supra forums, etc.
You're free to check any forum and do a word search under my name or MagnaFlow to see how active I am.
Again, it is my great privilege to share information from an "insider's" perspective.
I ask only that you do not shoot the messenger ;-)
In short, while I could not tell you why an X is better than an H in great detail, I can tell you that it is indeed, better.
Is it 2hp better than the rival Milltek? 5hp? Time will tell, but previous experience suggests that it is a few percentage points better, but the dyno numbers should help a bit.
What we really need is back to back comparisons at GMG on the same car....let the chips fall where they may and I'm sure both Milltek's and MagnaFlow's will perform as advertised.
With that said....I've been in this business 22 years and I LIKE TO THINK that I have a reputation for being honest...brutally honest.
If our system sucked, or didn't deliver as advertised, or was in some other way inferior, inadequate, or would reflect poorly on me as an individual, I simply wouldn't talk about it all.
I make nothing from it's sale...not a nickel of commission, not a promotion, nothing.
Frankly, while the point of our tips has been repeatedly debated and I've stated the company's position publicly, privately, my opinion is that I love the dual twin tips, but I wish they were bigger. Just my opinion. It doesn't make the MagnaFlow system better, worse, worth more, worth less, just different.
Ultimately, consumers will decide with their pocketbook.
I am SINCERELY appreciative of all the feedback I get here on this product, as I pass it along. Whether or not the company will change it's views remains to be seen, but ultimately, I'm here to share RS4 experiences, not to defend a position or further someone's agenda.
I've posted tidbits on the RS4 system because I wanted to help the Rs4 community. I did the same on the M3 boards, the Mercedes Benz CLK and SL forums, the Supra forums, etc.
You're free to check any forum and do a word search under my name or MagnaFlow to see how active I am.
Again, it is my great privilege to share information from an "insider's" perspective.
I ask only that you do not shoot the messenger ;-)
12-28-2006, 02:09 PM
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Craig...I was on the website, and when will it be available......
If it is not already. I'm thinking that maybe this early spring I would go with some catbacks....