Attempting to design quiet custom exhaust (warning: ridiculously long and detailed!)
Hey all,
I know that there have been many threads on this topic, but here is my attempt to build the quietest custom exhaust for the lude that I can think of based on the reading I’ve done from all the different Honda forums. If any experts out there have input, I’d really like to hear it. Thanks to Daemione’s research, a lot of which this is based off.
Goals:
- the reason I’m getting this system is to go with the SMSP header
- therefore the exhaust will be a 2.5� OD straight through design with mandrel bends
- I want the exhaust to be as quiet as possible; will try to fit in as many resonators as possible; willing to lose 1-2 hp, although according to some of Dave’s (SMSP owner) measurements, flow difference between straight pipe and Magnaflow resonators is negligible
- Will try to assemble it as economically as possible, below are the cheapest prices I could find
First off, for reference, here is a pic of the SH exhaust system (actually, an Apex'i WS, but measurements are same as stock):
So, here are the components I’m considering, from front to back:
1. Cat: Carsound 94406 cat, ~$95 from heeltoeauto.com
a. 15.5� long body, 7� wide, 4� high, 2.5� in/out
b. A universal long oval with the addition of a built-in resonated core that helps quiet exhaust noise
2. Resonators: Magnaflow 14416, $65 w/o shipping from bigexhaust.com
a. 4� round stainless steel, 20� total length, 14� body, 2.5� in/out
b. First straight section behind cat is about 40� long; the SMSP header is said to be about 6-8� longer than the stock BASE header. So for SH, it's presumably 3-5" longer than the stock header (stock SH header = 3" longer than stock base header). Being conservative, this leaves about 32-35� of straight pipe to work with. If anyone with the actual SMSP header could provide more exact measurements, that would be excellent.
c. I will therefore probably fit two of the 14� resonators back to back in this straight section, for 28� total resonator length. Could possibly try to fit in an 18" and a 14" resonator, for 32" of total resonator, but this would be cutting it way close, and I'm not absolutely certain this would fit. Now if you were buiding this system for use with the stock header, you'd then have the full ~40" to work with, and could thus fit in the 22" + 18" Magnalfow resonators for 40" total of resonator!!!
d. Have considered fitting in more resonators in the middle of the S bend (ie, after first 90 degree turn), and after the S bend (where there’s about 18� of straight pipe to work with). However, talking it over with the exhaust shop, the tunnel in these sections is not high or wide enough to accept 4� rounds. If installed, they would hang too low to be feasible. I’ve heard that the heat shields can be banged out, but I don’t know if large enough to achieve enough height. I was advised against removing the heat shields, since these sections of pipe are right next to the gas tank, which is made of plastic.
3. Muffler: Magnaflow mufflers, but considering a few different setups, based on which will be the quietest:
a. Option #1: Magnaflow 12258, 76.05 w/o shipping from bigexhaust.com
i. Aluminumized oval 5 x 8, 18 body, 2.5 in/2.25 DUAL out
ii. the is the biggest (told by Magnaflow probably therefore quietest) I can fit on; overall length of stock muffler with tips is 23�, therefore with an 18� body, only have about 5� for tips
1. so would use two Magnaflow 35125 4.5� long, 3.5� diameter, double-walled stainless steel tips to go on the dual outs, $20.15 each from bigexhaust.com
2. On this Magnaflow muffler, the dual outs are 4� apart center to center; if I put these 3.5� tips on, they will then be .5� apart—just like stock. However, it might look ridiculous having dual 3.5� tips (stock dual tips are 2.5� diameter)!! Any comments on how this would look?
b. Option #2: exact same setup as above, but with Magnaflow 12246, $64.23 from bigexhaust.com, an 18� long, SINGLE 2.5 in/SINGLE 2.5 out
i. Any ideas if there’s a difference between single and dual out wrt to sound? Was told dual might be quieter, but also that dual might flow too much = not enough backpressure = poor low end torque. Let’s not start that debate!!!
ii. Since it’s a 2.5� out, would step down at the tips, since most tips have 2.25� inlets; in light of the supposed benefits of backpressure, this is not a problem for me.
c. Option #3: Magnaflow 12216
i. Aluminumized oval 5 x 8 WITH 14� BODY, 2.5 in/ SINGLE out, $57.06 from bigexhaust.com
ii. Rationale here is that a 14� body would now allow for use of a resonated tip (= even quieter), which are always longer
iii. Would use Pilot 005 resonated stainless steel, 8� long, 2.5" in, 3.5 diam, $12.49 w/o shipping from expressdistributing.com
iv. could also use a dual tip (also always longer, and thus not possible to use with the 18" body single out muffler mentioned above), but haven't seen any that are resonated, so would defeat the purpose of using the shorter body muffler.
iv. ***So, any idea what would be quieter: long body 18� muffler W/O resonated tip, or shorter 14� muffler W/ resonated tip?***
d. Option #4: Magnaflow 12158
i. Same as Option #3, but this muffler is 2.5" in/DUAL 2.5" out
ii. Using this muffler, I could put two of the above resonated Pilot tips on!!! Hmmm, would this be even quieter? Who knows???
e. Lastly, Option #5: Hytech twin-loop muffler, ~$400 from Hytech
i. 2.5� all the way through
ii. Will DEFINITELY give quietest sound; again, willing to accept slight restriction, CON is expensive, so cost-wise would much rather go with Options 1-3
4. Mandrel Bends
a. For S bend, will purchase 2 stainless steel 90 degree bends S2509006-16, $15.15 each from promical.com
b. For bends leading to muffler, will purchase 3 stainless steel 30 degree bends S2503006-16, $12.33 also from promical.com
c. Anyone know what CLR (center line radius, ie, sharpness of bend) I need? they come in 4, 6, 9, and 12" CLRs. I assume about 6" for the S turns and 4" (sharper) for the C pipe?
Well, there you go. That’s my obsessive look at trying to build a quiet 2.5� straight through. I know it’s ridiculously long and detailed, no flaming please!!! Hopefully for others trying to design a custom system, you'll find all this research useful. And if any advice on my specific questions, I’d greatly appreciate it. Thanks…
btw, total cost for parts with shipping ranges from about $325 to $420 for the all Magnaflow setups, or about $700 for the Magnaflow resonators + Hytech muffler setup.
Add to this about $150-200 for an exhaust shop to weld it up.
What about just finding out the inner diameter of some of the fake mugen exhuasts? I don't know the exact diamater of loop in my mugen, but you might be able to use that, but buying the muffler would be expensive, but I do know they sell knock offs....
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Quote:
Originally Posted by SK Honda 7
but yea i wouldnt stroke ryan unless shrek was watching.
Sorry it's taken me so long to get to this - work's actually been busy for a change.
Re: the muffler size vs. resonated tip debate, I'm not sure. Going by the raw amount of absorption material, it seems to me that adding 2" of length to a muffler can is going to make a bigger difference than any resonated tip would - but I honestly don't know much about resonated tips & their efficacy. I can't help getting a "gimmicky" vibe from the idea, but again - no personal experience.
I have, however, read a few cases where people have changed their exhaust tone fairly dramatically simply by reducing the size of their muffler outlet or tip. I really want a dual-outlet on my set up, so I was going to try and go with the dual 2" outlets - the outlets might even extend far enough out to not even need to bother with extraneous tips for length (although I've read that tips should extend at least beyond the bumper to avoid having the exhaust use the rear bumper like a big drum & droning like crazy).
But assuming they extend far enough, I don't think I'd mind the "raw" look no tips would give, although I suppose I'd need to see it in person before knowing for sure.
As far as flow goes, dual 2" openings flow a little more than a single 2.5" opening, so there shouldn't be bottleneck there.
Area of the outlet pipe(s):
single 2.5" = 4.9in^2
single 3" = 7.1in^2
single 3.5" = 9.6in^2
dual 2" = 6.3in^2
dual 2.5" = 9.8in^2
dual 3" = 14.2in^2
dual 3.5" = 19.2^2
Although if bigger outlet = more noise, I guess you'd want the single 2.5" outlet instead of going dual. But a big variable is how the flow actually separates into two streams within the muffler itself. Anyone know how Magnaflow accomplishes this?
And I'm definitely not sure about the aesthetics of dual 3.5" tips - I think they'd look pretty obviously aftermarket. Although who knows - sometimes the proportions can work to trick the eye in cases like that. But personally I think I'm taking the smaller tips spread slightly farther apart.
Oh, and as for knock-off twin pass mufflers, I looked at them a while back, but wasn't able to find any that have a big enough inner diameter piping.
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Originally posted by Daemione Sorry it's taken me so long to get to this - work's actually been busy for a change.
Re: the muffler size vs. resonated tip debate, I'm not sure. Going by the raw amount of absorption material, it seems to me that adding 2" of length to a muffler can is going to make a bigger difference than any resonated tip would - but I honestly don't know much about resonated tips & their efficacy. I can't help getting a "gimmicky" vibe from the idea, but again - no personal experience.
This is a really timely thread, I don't know why I didn't look at it before.
I want to add my actual experience to what is being discussed here. I recently bought a Carsound hi-flow cat and a 2.25" mandrel bent cat back from kteller8. I read about the fitment problems in the past threads, but the shop I went to had no problems with it at all. The piece that goes under the rear suspension cleared without any problem. I highly reccomend anyone considering a cat-back to purchase from him, you will be pleased.
I also used a 36" Magnaflow Thrush series resonator (looks like a cherry bomb). It is a good one to use, because it is a straight-through design without louvers, and its cheap. When I put it on, it occupied most of the length between the cat and the first 90 deg bend toward the rear.
My real issue is the muffler. I am currently using a special uber-secret ninja-master muffler. The downside however is that it sucks balls. I knew it was basically going to be a big experiment when I put it on, so I risked and came up short. I put the car on they dyno last Saturday, and actually lost peak HP because the tip is too small . Anyways, I am looking for a new muffler to add, and I am leaning toward something in a twin-loop design. I would really love the Hytech, and I am even willing to shell out the $$ for it. However, I emailed John about it yesterday, and he said that the Hytech won't fit the Prelude. I am a little skeptical, and I have sent him a note back asking why. Since all my parts are custom fit, I'm sure I could get it in if I could buy one.
Anyway, I am also looking into other twin-loop designs, since they seem like the best possiblity for quiet and power. Mugen is the obvious alternative, but finding one is a bit hard. I have looked into the knockoffs, but I can't even find those. If someone knows where to get a twin-loop knockoff, I am really interested. Hell, I would be very excited about a groupbuy on anything twin-loop.
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Twin loop mufflers
- I too have scoured the web looking for someone who sells them, and have had no luck at all. From what I've been able to gather, the DC Sports copy is not a true twin loop design, and the only other one that might be an option is a Mugen copy made by a co called XForce. Looks like some RSK guys use this one. Don't know the specs on it, or who sells it. Too bad the Hytech might not work. Mugen diameter is too small.
I think though that I'd really like to just go with one of the Magnaflow mufflers to keep costs down for now.
Resonated Tips vs. Bigger Muffler
- I've been told by multiple Magnaflow techs that a bigger can will be quieter than 1 or 2 resonated tips. So I think that issue is resolved and I'll try to fit in that 5 x 8 x 18" can. Regarding its size, I think it shoudl fit, but I'm a bit worried about how its going to look with the can ending literally right at the inside edge of the bumper lip. An option is to paint the can black, but I think I'd rather go with the reliability and weight savings of stainless steel, and just have to deal with this bigass shiny can jutting out the back.
- about not putting tips on Daemione, I wouldn't mind that either, but according to my measurements the bare tips will end up being just a bit short = sooty bumper. That's why I'm going with the nonresonated short 4.5" long tips, should end up being just about stock length.
- Re size of tips, aesthetically, I don't think dual 3.5" tips will look that bad. They'll be separated by .5", same as stock, which will actually make them look closer than stock. I haven't been able to find short 4-5" tips in a diameter smaller than 3.5". I think 3" would be perfect, if we could find some.
Single vs. Dual Tips
- My main issue now is deciding between the Magnaflow single and dual tip mufflers. To answer your question Daemione, Magnaflow uses a V design for their dual tip mufflers. Immediately upon entering the can, the inlet just splits into two 2.5" diameter paths, surrounded by their sound deadening material.
- As far as quietness, I've heard reasoning both ways about what will be quieter. Two sound-deadened paths might be quieter, but then you also have a larger open cross-sectional area, which might be louder. I too like the aesthetics of dual tips, but will still go with what's quieter, whatever that ends up being. What may end up deciding singel vs dual for me is -->
- I'm unsure about is the whole back pressure idea. Is there a consensus on this board about whether back pressure is necessary or not? i've done all the searches, but haven't been solidly convinced either way. What do you guys think about this?
- i mentioned this concern to Dave of SMSP, and he basically scoffed at the idea of back pressure being necessary. this man know's what he's talking about, it's just that I've seen so much to the contrary that I'd like your opinions too. The reason is that different cars react differently to very low back pressure, some more susceptible to losing low-end torque. How do our preludes behave? I'd guess from everything else that they are susceptible to this, which is why I'm so wary.
- if back pressure IS necessary for our cars, then I will give up the dual tips because they flow so freely, and go with the single 2.5" out Magnaflow, stepping down to 2.25" at the tip inlet.
So those are the muffler questions for now.
Another snag is the Carsound cat. I had wanted to get the Carsound 94406 resonated cat, but it has a 15.5" long body (21" total). The body is about as long as the stock cat, but this cat is also 7"wide, and with the SMSP header pushing things back about 8", I'm afraid the width of this cat will not fit that far back in the tunnel. So I may go with the standard 93506 cat that Dave uses, or get the 43306 CA compliant cat, both of which have 12" long bodies.
So, finally, this is my current list of what to get, with the above consideration possible changing things:
68.47 Carsound cat 94406
111.14 Magnaflow Resonator 14416 SS 14/20, 4" round x 2
91.92 Magnaflow Muffler 14246 SS 5x8x18, 2.5 in/single out
20.15 Magnaflow Exhaust Tip 35125 SS 2.25 in, 4.5L, 3.5 diam
291.68
- all from justmagnaflow.com. Cheapest prices and free shipping on orders over $50!!!!! amazing! better than bigexhaust.com.
65.22 Mandrel bends: S2509006-16, 2.5� OD X 16, 90 degree, 6 CLR x 2 and S2503004-16, 2.5� OD X 16, 30 degree, 4 CLR x 3
To summarize and with my own conclusions, simply put, the point of bigger diameter exhaust systems is to accomodate higher exhaust flow demands created by the engine at higher rpms. It is the increased capacity of bigger exhausts to remove exhaust gases at high rpms which basically creates hp (it does this by maximizing both inflow and purity of the gas/air mixture on the intake stroke). A second component equally important as exhaust flow capacity (ie, diameter of your exhaust system) is exhaust flow velocity; you also want to create the highest flow velocity possible, because the faster the flow the more of an effective vacuum, ie, the lower the pressure will be at the exhuast port, not only allowing for exhaust to be pushed out by the upstroke of the piston, but also actively sucking out the exhaust from the cylinder (gas moves from higher to lower pressure, this is known as "exhaust scavenging").
So ideally you'd like to have both a high capacity and fast flowing system. To repeat, the way you get this is by having a large diameter, unrestricted system.
However, this comes at a cost, because a given volume of air will flow more slowly through a larger diameter pipe. Thus for your gain in flow capacity you are compromising flow velocity. This becomes significant at low rpms, when exhaust volume is low relative to high rpms, and thus slow flowing. Again slow flow = poorer suction (exhaust scavenging) at the exhaust port, making it harder for the engine to get rid of exhuast, and leading to mixture of exhaust and fresh gas/air mixture (during the overlap time when both the intake and exhaust ports are open).
So the problem at low rpms is low flow velocity. Its not at all that there is a "lack of back pressure." In fact, due to low flow velocity, there is higher pressure at the exhaust port, creating too much back pressure!
The idea then us to find the best compromise between the benefits of high flow capacity at high rpms and downside of low flow velocity at low rpms. Another way of putting it is what do you want to tune your exhaust system for? high rpm efficiency or low rpm efficiency?
So that's my quick summary of back pressure. When people say you need back pressure, they are really just pointing to the advantage of higher flow velocities (in reality lower back pressures at low rpm!!!) created by a smaller diameter system.
Ok, so now applying these concepts the question of using the Magnaflow single vs. dual tip mufflers the question becomes, what will preserve the greatest flow velocity at low rpms? Pro back pressure people, based on their reasoning, would suggest that a single outlet muffler would be better (provides more back pressure than a a more freely flowing dual outlet muffler). But based on the above, this thinking would be incorrect. So what then? Well, actually, either way, i think the answer is it shouldn't make too much of a difference between singe and dual outlet this late in the exhaust path.
If going with the singe outlet, I was planning to use tips with with a 2.25" inlet, because these are the only nice-looking, cheap tips I could find that were only 4.5" long. Now stepping down from the 2.5" exhaust piping to the 2.25" tip inlet, you might think this is a good thing, because via the Venturi Effect you'd be increasing exhaust flow velocity (Venturi effect is pinching end of garden hose to create jet of water). However, increased flow velocity after the exhaust would be useless, and before the pinch not only would velocity be the same, but you'd also be introducing more back pressure created by the pinch/restriction(and again, this would be even worse for low rpms).
With a dual outlet muffler, there's no such restriction at the end. The only consideration is, would the increased flow capacity of the dual outlet muffler slow down exhaust flow velocity enough to be significant. I'd guess no. But if it did, then the ideal would probably then be a single outlet muffler with a 2.5" inlet tip. I think these differences are negligible though.
Given the above, the deciding factors between single vs dual out mufflers then become aesthetics and quietness (since backpressure as a consideration has been eliminated). As I've said, I like dual tips. Now the only thing is how to decide which will be quieter. Any ideas?
If I'm wrong about anything I've mentioned, please correct.
Originally posted by devtec Twin loop mufflers
- I too have scoured the web looking for someone who sells them, and have had no luck at all. From what I've been able to gather, the DC Sports copy is not a true twin loop design, and the only other one that might be an option is a Mugen copy made by a co called XForce. Looks like some RSK guys use this one. Don't know the specs on it, or who sells it. Too bad the Hytech might not work. Mugen diameter is too small.
I think though that I'd really like to just go with one of the Magnaflow mufflers to keep costs down for now.
There are several knock offs I'm aware of. Xforce is one of them (company in OZ I think), and OBX, Ractive, and Top Speed all made replicas as well. Of the Replicas, the Top Speed version is the only one I would consider buying if I could actually find it.
It turns out the Hytech may fit after all. I am still talking to John about it, but he is making some assumptions that my not be true. I also have a lead on a JDM Mugen exhaust with larger dimensions than the USDM versions. Either way, I will own one of the two.
Quote:
I'm unsure about is the whole back pressure idea. Is there a consensus on this board about whether back pressure is necessary or not? i've done all the searches, but haven't been solidly convinced either way. What do you guys think about this?
- i mentioned this concern to Dave of SMSP, and he basically scoffed at the idea of back pressure being necessary. this man know's what he's talking about, it's just that I've seen so much to the contrary that I'd like your opinions too. The reason is that different cars react differently to very low back pressure, some more susceptible to losing low-end torque. How do our preludes behave? I'd guess from everything else that they are susceptible to this, which is why I'm so wary.
- if back pressure IS necessary for our cars, then I will give up the dual tips because they flow so freely, and go with the single 2.5" out Magnaflow, stepping down to 2.25" at the tip inlet.
Carsound Cat... maybe I'm weird, but I put one on after my Random went (threw CE 67 if I remember right...) and kept throwing a CE 67. Put on a new Random, and the CE's went away.
A little of back history...I have a DC header going through a Random cat into a custom exhaust that has the 22" magnoflow cat(if I remember all of it) and one of the magnaflow sport mufflers. THIS IS LOUD!. Maybe not as loud as some of the systems out there, but people hear me coming. I do get comments on the tone, but make no mistake, this is OBNOXIOUS.
So much so I've been pondering scratching the whole thing for an Apexi WS or try something like the Hytech muffler...or evern one of those aeroturbines...
...and just a note...highway travel at between 3000-4000 RPMs is the most annoying frequencies...
No FLAME-Are you desiring to reinvent the thing? I really hope not. We have a shop here that does what you want in stainless every day. He specializes in just what you want to have. Sadly, this is not going to be cheap in either case. He uses a mandrel bender and can use any components that are needed to get the job done right. I'm sure you have a place in your area with this kind of fabrication ability. Make sure that the welding is first rate. Some of the parts you mention will work very nicely. You might also take a look at CATCO convertors from Summit.
If you want to spend a bit more I will suggest that you go with the Thermal R&D unit. That is what we have. Simple install, all stainless mandrel bent and so far has the look and sound we wanted.
Happy Luding
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Grandpa's toys-modded suspensions and a few other tweaks
'99 Prelude SS - A sweet song in motion SOLD
'89 CRX Si= SCCA/NASA/PDA ITA #99
'03 Dodge Dakota Club Cab (4.7L)-gonna tow
Thanks to KONI, KIRK Racing, Longacre, UPRacing, Summit, Racing Electronics and my crew.
Re-measured the stock muffler last night - I'm confident that there is plenty of room for the 18" magnaflow muff if you/we go that route.
The stock muffler is a weird oblong triangular shape, but it's 15" long, 11" wide, and 10" tall, with 8.25" tips. There's 4" of space behind it before you run into a frame/bumper rail, and another 1.5" in front of it before you hit the sway bar mount.
So with the front of the muffler located where the stock one is, an 18" 5x8 oval body muffler should fit easily. We'd need to add another 2.25" of tip length to get them to extend as far as the stock ones do.
Didn't get to double-check the stock cat size & it's available clearance, though - I'll do that this weekend when I've got it up on stands for another project.
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Originally posted by Daemione Re-measured the stock muffler last night - I'm confident that there is plenty of room for the 18" magnaflow muff if you/we go that route.
One thing I forgot to mention is that I placed an order with John at Hytech for the twin loop muffler. I have measured lots of things under the car, and I am more than sure it will fit. I will post complete pictures and an explanation of my setup when the muffler gets put on.
I can't wait!
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A question with the custome exhuast 400 tiwn loop muffler from Hytech + resnator + weld + pipe. We are looking about 700 how much was mugen again 900???
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Vick's E46 Retro 
I knew it was basically going to be a big experiment when I put it on, so I risked and came up short. I put the car on they dyno last Saturday, and actually lost peak HP because the tip is too small 
. Anyways, I am looking for a new muffler to add, and I am leaning toward something in a twin-loop design. I would really love the Hytech, and I am even willing to shell out the $$ for it. However, I emailed John about it yesterday, and he said that the Hytech won't fit the Prelude. I am a little skeptical, and I have sent him a note back asking why. Since all my parts are custom fit, I'm sure I could get it in if I could buy one.
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