Stroker M20 exhaust

[digger]

you dont want back pressure, you want good velocity and correct lengths.

i'd use a resonator in the middle section otherwise it's loud/sounds crap IMO. a resonator wont cost hp if you use a hot dog style unless you use a restrictive muffler as a resonator even then it wont be alot.

you need a surprisingly big restriction in the exhaust to cost hp on a lowish hp m20. i did tests once and you need something like a 1" orifice plate in each tailpipe to start to really hurt a 200whp engine.

this kinda means that people are generally using oversized pipes.

[AWDBOB]

Digger, I'll be running LTs with 2.25" collectors, and a catback with 2.25" piping to a muffler in the back.

What would you recommend for a mid pipe? The end result will be a simple stock bottom end 272 cam M20 with ITBs, I just want to make sure I don't kill the power without enough backpressure.

Is it alright to stay 2.25" duals in the mid pipe? Straight pipe or resonator in there? Just want to make sure I don't lose power.

[Regnar75]

"knowing this pipemax says 32" is the correct location for the Y-pipe and Burns X-design says 30". So both are in good agreement so that's decided."
this is interesting, does this mean the ideal location of Y pipe on m20 exhaust system would be 30-32 inches from the exhaust port on the head?
"about 400mm when might be better to have used 800mm or 1600mm which are also harmonic lengths" or do you mean even more so like 60+ inches like the s54? this is interesting and i was just planning on rebuilding my exhaust but this is making me think twice about how i should place my Y pipe.

[digger]

Wow glad i found this thread. I normally skip over the exhaust section of this forum.

Excited to see you're going with single 3". This may be of some interest to you. It's a 4 banger but same chassis ;)

http://www.e30m3project.com/e30m3per...haust/exh1.htm

Is the placement of the venturi collector close to where the "x" would go in a dual system?

ill be putting it venturi at 3rd harmonic, x-pipe is 2nd according to pipemax. i could also put the venturi at the 2nd. i wont do any testing of venturi position on this engine perhaps the next it depends how things respond

id seen that article ages ago but forgot about it and thats what i will be doing in effect, i'd be interested to know if the S14 was tuned afterwards as it makes a big difference

[tinkerputzer]

Wow glad i found this thread. I normally skip over the exhaust section of this forum.

Excited to see you're going with single 3". This may be of some interest to you. It's a 4 banger but same chassis ;)

http://www.e30m3project.com/e30m3performance/installs/installs-2/exhaust/exh1.htm

Is the placement of the venturi collector close to where the "x" would go in a dual system?

[digger]

Ha, yeah I agree with that. Sometimes I forget you are on the other side of the planet Calling burns would be kind of difficult haha

Are you going to be using a flex pipe? I put mine right after the merge, but at that point in time I was just making the exhaust and not engineering it so to speak. Also, are you separating the exhaust? I did mine in three pieces, well six total if you include the headers. The Accuseal clamps work great if you don't want to run v-bands. I would also recommend TIG'ing everything, even the slip fits; the penetration control is just so much better and it just looks cleaner. The flex pipe is a slip fit on my merge collector. This was my first TIG protect too, and now I have much better bead uniformity haha

IMG_4150 by Los Pantelones!, on Flickr

I also did not back purge mine, and it turned out okay. For 304 stainless it's a must, and would not look this clean on the inside.

IMG_4149 by Los Pantelones!, on Flickr

im not currently running a flex pipe seems to work ok like that.

i will have segments, there is currently a slip joint and a flange joint. slip joint will remain with clamps.

butt welds will be TIG and purged, bends will be mandrel ones

[pantelones]

they look pretty cool at worst, supposed to arrive on monday

Ha, yeah I agree with that. Sometimes I forget you are on the other side of the planet Calling burns would be kind of difficult haha

Are you going to be using a flex pipe? I put mine right after the merge, but at that point in time I was just making the exhaust and not engineering it so to speak. Also, are you separating the exhaust? I did mine in three pieces, well six total if you include the headers. The Accuseal clamps work great if you don't want to run v-bands. I would also recommend TIG'ing everything, even the slip fits; the penetration control is just so much better and it just looks cleaner. The flex pipe is a slip fit on my merge collector. This was my first TIG protect too, and now I have much better bead uniformity haha

IMG_4150 by Los Pantelones!, on Flickr

I also did not back purge mine, and it turned out okay. For 304 stainless it's a must, and would not look this clean on the inside.

IMG_4149 by Los Pantelones!, on Flickr

[digger]

The decibel output is not reduced (by much...), but the frequency is changed by the resonator. I don't have the formula/s on hand, but you can calculate everything out to produce the tone you desire. The general purpose is to target a certain RPM band; for instance a highway cursing scenario that has terrible drone can be fixed by either adding resonator pipes, or reconfiguring the exhaust. Theory in practice seen here....

http://www.modified.com/tech/modp-1102-motordyne-tuning-test-pipes/

IIRC the s2000 had resonator pipes stock near the rear muffler, but I could be wrong. Speaking of s2000's, I came across this awhile back and think you might find it interesting. Not practical on your time frame, but food for thought....

http://www.s2ki.com/s2000/topic/991992-gern-pipe-group-buy/

Also, the venturi from what I have read is either purely snake's oil, or has a very minimal effect. Although, the link above makes me think twice about that. It would be a ton of arithmetic to calculate the scenario, but it is definitely is worth looking into. Did you speak directly to burns about your exhaust plans, and if so, what did they have to say? The fact that they produce them to begin with does mean that there is merit to the idea, but I came across this insightful bit...

As you have stated and already figured out (length), the merge on single merge collector's secondary is very, very important. A (m20 scenario) 2-1-2-1 set up would not be as crucial on the last merge, but rather the secondaries themselves are the most crucial, even more than the primary length/merge. NASCAR has heaps of info on header design, but you have a really nice set to begin with.

Also, my understanding of everything after the merge and "open exhaust" scenario leads in the direction of as long as the units can flow the peak CFM produced you can do what you please. I don't have any experience with the mufflers you are planning on using, but I made a header back exhaust that sounds great with minimal drone and rasp. The drone and rasp that did occur was due to the thin headers I was using. If you were local to me I would do your exhaust for free since you have given myself, and the whole forum a vast amount of knowledge! Please have it TIG'ed, back purged, and NO cheater bends! Good luck with your exhaust and I hope some of this was helpful :up:

from my understanding the gradual change of a venturi produces an affect over a wider rpm band than an abrupt area change and it helps at the bottom end if nothing else. apparently allows you run shorter primaries which canproduce more topend. my header primaries are a little short by 2" so might work to my favour....idk

they look pretty cool at worst, supposed to arrive on monday

i emailed roman but did not speak to him, the time difference at this time of year is prohibitive.

i will ask for non slip joints to be TIG'd im not going to go to an elcheapo exhaust place

[pantelones]

Most resonators are just straight through glasspacks. On those type, the size of the body has the largest effect on how much sound is reduced.

The decibel output is not reduced (by much...), but the frequency is changed by the resonator. I don't have the formula/s on hand, but you can calculate everything out to produce the tone you desire. The general purpose is to target a certain RPM band; for instance a highway cursing scenario that has terrible drone can be fixed by either adding resonator pipes, or reconfiguring the exhaust. Theory in practice seen here....

http://www.modified.com/tech/modp-1102-motordyne-tuning-test-pipes/

IIRC the s2000 had resonator pipes stock near the rear muffler, but I could be wrong. Speaking of s2000's, I came across this awhile back and think you might find it interesting. Not practical on your time frame, but food for thought....

http://www.s2ki.com/s2000/topic/991992-gern-pipe-group-buy/

Also, the venturi from what I have read is either purely snake's oil, or has a very minimal effect. Although, the link above makes me think twice about that. It would be a ton of arithmetic to calculate the scenario, but it is definitely is worth looking into. Did you speak directly to burns about your exhaust plans, and if so, what did they have to say? The fact that they produce them to begin with does mean that there is merit to the idea, but I came across this insightful bit...

Best look at exhaust systems that no one is trying to market to you if you are considering performance. A place where they are spending hundreds of millions of dollars trying to squeeze horsepower out of an internal combustion engine, and where they aren't trying to sell you some billet trinket, is probably a good place to start to find some answers to these exhaust questions.

As you have stated and already figured out (length), the merge on single merge collector's secondary is very, very important. A (m20 scenario) 2-1-2-1 set up would not be as crucial on the last merge, but rather the secondaries themselves are the most crucial, even more than the primary length/merge. NASCAR has heaps of info on header design, but you have a really nice set to begin with.

Also, my understanding of everything after the merge and "open exhaust" scenario leads in the direction of as long as the units can flow the peak CFM produced you can do what you please. I don't have any experience with the mufflers you are planning on using, but I made a header back exhaust that sounds great with minimal drone and rasp. The drone and rasp that did occur was due to the thin headers I was using. If you were local to me I would do your exhaust for free since you have given myself, and the whole forum a vast amount of knowledge! Please have it TIG'ed, back purged, and NO cheater bends! Good luck with your exhaust and I hope some of this was helpful :up:

[digger]

Most resonators are just straight through glasspacks. On those type, the size of the body has the largest effect on how much sound is reduced.

I don't see any issue running two mufflers as long as they flow enough but i know you have that covered.

yeah thats why i asked about a muffler instead of a bottle style (hot dog) resonator the extra volume is surely better. im running two at the moment (either 2.25" or 2.5" not sure) and there is hardly any volume in them so i wonder how effective they actually are. my muffler is huge though 22" long 12" wide at the body

I don't see any issue running two mufflers as long as they flow enough but i know you have that covered.

i havent found specifics for the borla pro xs but since itwould go in place of a glasspack an XR1 would also work subject to being compact.

the best clearance would be with one of these

http://www.borla.com/products/xr1_se...rt__40536.html

but added expense of two oval transition pieces which might not be justifiable given at the end of the day my cat is lowest point at the moment though the new cats will be a little more compact at 4" as it doesnt have the heat shield. im not sure how low a 4" body cat would hang when hugging the body

[LJ851]

Most resonators are just straight through glasspacks. On those type, the size of the body has the largest effect on how much sound is reduced.

I don't see any issue running two mufflers as long as they flow enough but i know you have that covered.

[digger]

Im starting to think the sizes might not be big enough to support the power output either. Remembering rough tables you can use as a guide, 3" single is good for about 750cfm and supports about 320-330hp, while 2" is about 320cfm and somewhere around 150hp. Used in twins, it's less than 300hp. I know it's only a guide and the figures are probably a little underestimated rather than being dead on, but you might have to step up to 3 1/4" and 2 1/4" secondaries to support the power this thing could potentially put out. Im only using other rough figures as a guide, but what are you expecting, have to be somewhere in the range of 330hp (or more)?

As far as construction goes and components, I reckon it is going to be a case of how quiet you really want this thing to be and potentially having to tune out some of the drone or frequencies you hate. You can get some super high flow mufflers like those spintech race series or dynomax ultraflow mufflers which flow absolute shit loads and are pretty compact (especially in the case of the spintech). Used a few on V8's recently but they probably aren't going to quieten it down enough for you though. Along with some of the flow masters, they would be pushing mid 90's to 100db I reckon.

Not running a resonator is really just going to be about your personal taste I think and you'll probably just have to try it and see. Not so much from a loudness stand point, but if there is too much crackle or bark that you can't stand. If there is, you'll probably have to add in a resonator which will take out some of the higher frequencies and leave you with the lower burble.

Normally I'd be inclined to build one without a resonator and see what it sounds like, but in this case with a single system and the fact you hate any rasp and crackle, I don't think you are going to get around this and will have to run one. I would probably make a suggestion that if you are going to only run a single muffler in the system, id be stepping up to the next full size in diameter into the muffler which will help quieten it down more. If you are running a 3" system, id look at maybe stepping up to a 4" entry muffler, something as long as you can physically fit between the diff and the valance, talking in the realm of 18-20" long. Should give you the best change at reducing volume as much as possible, especially if you run something that is advertised as high flow/horsepower, so bigger entry in and longer is going to help keep it quiet.

David Vizard recommends 2.2CFM per hp so 720CFM and graham Bell says a 3" is good for 320bhp. DYnomax VT 2.5" flows 970cfm (according to them) so 3" is probably more. In Vizards book a 3" borla flows the same as the pipe. im sure it wont be costing any meaning amount of hp. i'm not expecting anymore than 320-330bhp with the CR and duration i will use.

Rama made 290rwhp through a 2.5" system AFAIK (definitely when he was 260rwhp it was 2.5") and IIRC recently upgraded to a 3" and said not a big difference. Robs 2.8L with 360rwhp uses 3" so should be fine.

i wouldnt run a single muffler. id run a another muffler in place of a resonator so have two mufflers

[Madhatter]

Im starting to think the sizes might not be big enough to support the power output either. Remembering rough tables you can use as a guide, 3" single is good for about 750cfm and supports about 320-330hp, while 2" is about 320cfm and somewhere around 150hp. Used in twins, it's less than 300hp. I know it's only a guide and the figures are probably a little underestimated rather than being dead on, but you might have to step up to 3 1/4" and 2 1/4" secondaries to support the power this thing could potentially put out. Im only using other rough figures as a guide, but what are you expecting, have to be somewhere in the range of 330hp (or more)?

As far as construction goes and components, I reckon it is going to be a case of how quiet you really want this thing to be and potentially having to tune out some of the drone or frequencies you hate. You can get some super high flow mufflers like those spintech race series or dynomax ultraflow mufflers which flow absolute shit loads and are pretty compact (especially in the case of the spintech). Used a few on V8's recently but they probably aren't going to quieten it down enough for you though. Along with some of the flow masters, they would be pushing mid 90's to 100db I reckon.

Not running a resonator is really just going to be about your personal taste I think and you'll probably just have to try it and see. Not so much from a loudness stand point, but if there is too much crackle or bark that you can't stand. If there is, you'll probably have to add in a resonator which will take out some of the higher frequencies and leave you with the lower burble.

Normally I'd be inclined to build one without a resonator and see what it sounds like, but in this case with a single system and the fact you hate any rasp and crackle, I don't think you are going to get around this and will have to run one. I would probably make a suggestion that if you are going to only run a single muffler in the system, id be stepping up to the next full size in diameter into the muffler which will help quieten it down more. If you are running a 3" system, id look at maybe stepping up to a 4" entry muffler, something as long as you can physically fit between the diff and the valance, talking in the realm of 18-20" long. Should give you the best change at reducing volume as much as possible, especially if you run something that is advertised as high flow/horsepower, so bigger entry in and longer is going to help keep it quiet.

[digger]

anyone got any thoughts on using a muffler instead of resonator?

i'm thinking of ground clearance. the vibrant ultra quiet is 4.5" and i can get a borla pro xs in 4" height so thats a decent amount difference.

would a muffler be a better resonator than a bottle style resonator?

i would then run a dynomax muffler in the muffler position so have two mufflers rather than a resonator and muffler

[digger]

Interesting, so if you combine to 1 pipe too early or too late, you lose power? How significant?

yes, in my case i had the x-pipe too close it seems it was about 400mm when might be better to have used 800mm or 1600mm which are also harmonic lengths that provide more torque theoretically but when you have cats, resonators and mufflers this can throw it all out the window. if you look where OEM puts H-pipe on S54 it has halfway down, now it is a different engine but new m20 engine will be similar in allot of ways as far as engine size, power and torque numbers