Db test on exhaust??

Hi people,

Has anyone done a Db test on how loud their gutted or aftermarket exhaust is??? (i'd be more interested in the readings from the gutted ones) I'm considering gutting the exhaust on my 07 viffer... but want to check how loud its gonna be first!!

If you have an iphone, they have Db testers on there, one called 'Decibel' oddly enough. I know they wont be accurate, but it would give me an idea on the noise difference.

Any help would be much appreciated

Cheers

Jamie

 

I know that a Two Bros Vale on a 6gen is 98db @7000rpm and baffles in, 102db without. I can't be sure, but a gut job should be a few db louder.

 

Righto, thanks guys

 

At this point, everyone knows how I feel about the gut, but this seems like a good short term answer (don't know why I've never heard of it) while waiting for a real exhaust. Wonder why everyone is going to the trouble of a full blown gut when this relatively easy solution accomplishes the same thing?

 

That article goes far in detailing what I don't like about gutting internals. Gutting is a simple solution in noise generation without regard to operation. If everybody that removed exhaust internals got a dynoed map afterwards then it would be no big deal; except that a dyno tune goes against everything the gut represents.

 

Well ive gone and bought myself some leo vince carbon fibre cans anyway

Just couldnt resist!!

 

I've read that thread several times before. There is some bogus info in there. The general idea is good, that's all. I don't believe the mfr's go thrui all the trouble to "tune" the exhaust for max performance. I believe their main design is for fit and lower sound levels. There are many bikes that run better with after market exhaust because of less back pressure and a better tune. You will change the exhaust pulse time just by changing engine timing. Depends on when you initially set off the boom compared to the cam profile of when you close the intake and exhaust valves.

The power is made at the collector in a header (open exhaust) now when you put any kind of pipe after that you are basically changing the sound. Unless you get real restrictive. The biggest issue I feel is matching the exhaust tube diameter to the hp of the motor and the length of the primary tubes going to the collector. Anything after that is just noise control.

I don't know anybody that can actually figure out when the pulse wave returns up the pipe and gets to the exhaust port at a given point. The only way I know of is to have a dyno and use different length and shape(bends) to see where the highest hp or tq is just by changing pipes, depending on what your building for. Once you change cams, timing or the fuel system you will be changing other aspects that will effect the type, size and speed of the pulse wave.

 

Nice choice, I think that you'll be very happy.

 

Um, the last time I looked Honda was a multi-Trillion dollar corporation with its hands in everything from motorcycle racing to aerospace engineering and satellite design. We are talking about R&D departments with virtually unlimited resources in a world where we can split an atom and then map out the exact path that the protons took en route to the next collison down to the billionth of an inch. I think that determining the exact point at which a wave travels through a pipe after ignition would be fairly simple by that point, don't you.

And at what particular point are you claiming bogus information? Not that I'm saying everything I relayed is 100% accurate, because I'm simply a student and was relaying information that was squeezed into my head in just 3 weeks time... but I'd like to know what you have contention with so that I can clear it up or offer more accurate information than what was already provide.

 

I think you need to come in to the real world. There are budgets for all corporate departments, even R&D. There are real world regulations those companies have to play in. They have to make compromises to meet those regulations. They have to decide on where they are going to use that money. For their factory backed race bikes I would think they would spend the money. For all of their production bikes to eeck out maybe 1hp I don't think so. They won't get the return (hp) for their money like a fixed dimension such as more cam, piston etc will.

All the tune in a pipe happens in milliseconds. It's there to stop over scavenging the cylinder. When the exhaust goes out it clears the cylinder of burnt gases. The cam over lap keeps clearing those gases and helps draw in new A/F mix. The secondary pulse travels back up the pipe and will retard, if not stop, the cylinder scavenging. To tune a pipe as perfect as you say they do. They would have to time that pulse just perfect to hit the exhaust port at the point all the burn gases are expelled and keep any new A/F mix from exiting just prior to E valve seating. On all their production bikes? For what?

Now change the cam install point one degree (cam chain slop) and all that goes out the window. I agree exhaust systems are technical and can play a big part in hp, tq, type of power ban or what ever they are designed to do for a particular engine.

The diameter, length and type of bends play a more important role than trying to time a pulse. Which plays a part of pulse timing. There are to many uncontrollable parameters in production engines for that. It's great in theory but real world it's mute. I agree they probably get it the closest on race bred type bikes.

I do agree with you that the design of the exhaust plays a big role in how the engine runs and depending on how you change your exhaust system can hurt how the engine runs or the need to re-tune. Which could mean just an A/F ratio change in part of the power band. But to state that the manufactures tune exhaust to have the pulse waves perfect or close to it, I don't buy that. Most are just the opposite because of regulations.

 

Tink thanks kind of a stretch there when the average muscle car was std at 335-350 hp out of 350-400 ci. Now take the high performance models of 390-475hp plus 450-500 lbs of torque out of 421-455 ci. Which today's cars don't make the torque of yesteryear. For example the 2010 Camaro LS3 6.2l engine puts out 426hp with ONLY 420lbs of torque. My standard lowly stock 66 389 at the time was only 335/360hp with 437/430lbs tq. Hardly twice the power.

Yes both groups have their specialty builders that can squeeze the bejesus out of both era engines. Today they should make better/easier hp with 40 years more technology. The biggest difference I see is the fuel mileage has increased immensely. The use of SC or turbos have increased also to make big hp out of little motors like the WRX or Mazda 3S.

Even with all of this they still have to make compromises. Your right though they have figured it out and part of that is friction. The machining today is way better than yesteryear as well as the materials they are using. Aluminum is cheaper today. A lot of cars have aluminum heads. Which require more compression (hp) and resist detonation at those levels. Put aluminum heads that flow 250 cfm on my 389 along with manifold, fuel system, roller cam and that new Camaro won't touch me.

But todays cars no where near double now is it..............................

 

So, basically then... and correct me if I'm wrong here guys... you pretty much just verified everything that I stated in Tink's post on exhaust waves, and reinforced the idea by going into detail on what needs adjusting and at what point to make the best scavenge for each type of engine based on the amount of a/f mix required to get the most power out of the cylinder at hand... right? So this means that either you're a very intelligent person or you've spent a bit more than 30 minutes doing some last minute research on Google about the subject.

But how can you say all that and then flip it and say that you don't buy that a company that's sole purpose is to build performance engines doesn't have the ability to tune their engines to the point that they achieve maximum performance down to the point of proper exhaust waves at the port? And why wouldn't they transfer that technology to the consumers edition of their vehicles when that what they make their money on is the end sales of their production line of cars, bikes, and sport vehicles?

Real World: Honda (which claims a $1.7 billion profit in '09 and had $92 billion in sales in '07) has a budget for R&D of $4.7 billion per year -- which is just 5% of sales). That's a larger percentage comparison than the U.S. Government in terms of Military expense to R&D at NASA.

Real World: Honda uses their racing teams to test new equipment and technology that, if it passes, goes directly into consumer models - mostly unchanged (RR models)

The most powerful Honda engine would have to be the 3.0 L carbureted V-8 engine that was used in Formula One series racing, although this engine is now retired and was replaced with a 550 hp 3.5L V-8 used in the SuperGT circuit, it produced about 750+ HP with 225 ft-lb of torque and had an electronically limited top of 10,300 rpm's. This is, by the way, a variation of the prototyped engine used in the 290 hp Acura NSX-R, which is also capable of the same 225 ft-lb of torque.

Unfortunately, the torque of an engine is very hard to change. Pretty much when you take an engine design from any manufacturer you're going to have a set amount of torque for that engine for the lifetime of it's production, even though the horsepower may increase over the years. HP is easier to increase than torque because unless your using a supercharger, the air intake is at atmospheric pressure and the engine can only put out what it gets in, so to speak. Now when you look at racing engines that don't have to fall on the ears of the EPA and have all the restrictions that production cars do, then you get a bit juicier. Larger displacements, smaller and smoother intakes, perfected scavenging, and just enough pipe on the exhaust to get the job done puts modern day NASCAR Cup series engines at nearly 900 Hp with about 520 lb-ft torque.

Now, some clarity on the exhaust to muffler debates. The exhaust is, for the purpose of this debate, the pipe originating at the exhaust port and ending at the muffler pack. The mufflers job is simply to reduce noise (or make it these days) and plays no critical role in the effectiveness of the engines ability to produce power. So, for your comment about the EPA regulations, the only thing the EPA regulates when it comes to the exhaust is the sound (80 Db max) and that is attained with the muffler, not the exhaust. To say that the EPA would make a manufacture 'de-tune' an engine due to regulations is just silly. The VFR1200f is 'de-tuned' for safety by Honda themselves because if they set the mapping to allow the full potential of the bike like they did in the testing trials, the common consumer would end up killing themselves or others because of the fact that the 1.2L V4 puts out 80 ft-lbs of torque @ 170 hp... and that's limited! The EPA has nothing to do with how limited a bike is on power, unless your talking about California models with their 50 lbs of extra hoses and canisters and crap to counteract the 200 million tons of pollution that the state puts out annually... like doing that to a couple thousand bikes is going to make a difference while the 20 million diesel trucks continue to dump their crap into the air. Sorry, sore subject. Anyways.....

The common practice today is to use slipper mufflers which, if installed properly, needs no change to the exhaust and simply reduces or increases the sound of the bike. However, because most modern day bikes have such long exhaust pipes, most people and shops cut off up to 12 inches of the pipe in order to allow for an acceptable cosmetic appearance for the muffler. This changes the pipes tunability and will effect the scavenge, which will require a lower a/f mix as well as an advance or retard in the timing to compensate.

This is the most true for two stroke engines, and is defined by the bulbous exhaust just after the initial bend. That's not the muffler, that's just how much back pressure the exhaust wave needs to provide in order to keep the engine running properly at high rpm's. Four strokes aren't that intense due to their design, and only need sometimes just an 1/8th inch diameter change and slight pitch to return the proper pulse.

The result of running open pipes on ANY engine, be it a car, bike, or diesel engine will all result in the same thing. A loss in hp (the ability to reach speed quickly) and a loss in effective torque (total power). That and if it's a V-twin makes it sound like a sick John Deere! LOL

But, as I was saying though... you agree that the technology is there, and you included the base of the theory, which you didn't deny was good in production... yet how can you say now that it doesn't exist in real world engines?

Tell you what... You take ANY 2 bikes off of ANY dealer lot, I'll take the one thats stock, and you take one that has a modified exhaust with no internal mods made to the engine (a simple cut and install). We'll take those two bikes to a track and run them on a 1/4 mile. I'd bet my ass that the stock bike would win.

My point was and still is, if you modify the exhaust pipe - you must adjust the engine accordingly or you will lose power. Power is not gained by simply putting an aftermarket exhaust on your bike.

Class dismissed. :smile:

 

"But how can you say all that and then flip it and say that you don't buy that a company that's sole purpose is to build performance engines doesn't have the ability to tune their engines to the point that they achieve maximum performance down to the point of proper exhaust waves at the port?"

So Honda's sole purpose in life is to build performance engines? News to me. I thought their purpose was to manufacture car, motorcycles etc for the public. I never said they didn't have the ability to tune down to the pulse wave. What I said they won't do it in production cars or bikes. Why because of cost. For a specific model they may get it the closet they can. Just give me some kind of proof they do that for Goldwings, VTCs or Civic, Accord engines or what ever. No matter how much money and technology they have. The biggest draw back is the $$.

"The most powerful Honda engine would have to be the 3.0 L carbureted V-8 engine that was used in Formula One series racing, although this engine is now retired and was replaced with a 550 hp 3.5L V-8 used in the SuperGT circuit, it produced about 750+ HP with 225 ft-lb of torque and had an electronically limited top of 10,300 rpm's. This is, by the way, a variation of the prototyped engine used in the 290 hp Acura NSX-R, which is also capable of the same 225 ft-lb of torque. "

Now we are talking factory race engines/cars vs production. Apples and oranges. Then look at some of the American factory A/FX cars of 600-800 hp NA. Factory built from the 60/70's.

"Unfortunately, the torque of an engine is very hard to change. Pretty much when you take an engine design from any manufacturer you're going to have a set amount of torque for that engine for the lifetime of it's production, even though the horsepower may increase over the years. HP is easier to increase than torque because unless your using a supercharger, the air intake is at atmospheric pressure and the engine can only put out what it gets in, so to speak. Now when you look at racing engines that don't have to fall on the ears of the EPA and have all the restrictions that production cars do, then you get a bit juicier. Larger displacements, smaller and smoother intakes, perfected scavenging, and just enough pipe on the exhaust to get the job done puts modern day NASCAR Cup series engines at nearly 900 Hp with about 520 lb-ft torque."

Your two sentences are B.S. You can change tq by changing when the intake valve closes. Talk to any good cam grinder. Just change rocker ratio. That's just one way with the cam/rockers. Ever here about bore/stroke ratios? Dual plane and single plane manifolds will play a big part in the tq equation. Tq is what gets the car moving. After 5250rpms the tq starts to fall off. Then you better have rpms to make hp. That's why F1 turns to 18,000 rpms to make 600hp compared to something like a Ford Shelby GT at over 500hp @ around 6000rpms. It's in the tq. You wouldn't want that in a street production car like the F1 now would you? As far as air intakes you'll never reach 100% VOE in most production engines. NA racing engines can go over 100% by using the ram effect, by maybe 10%. Most still don't for one reason or another.

"The mufflers job is simply to reduce noise (or make it these days) and plays no critical role in the effectiveness of the engines ability to produce power."

Not all mufflers just reduce sound. Some are so restrictive they will rob power. So your saying the bike will run exactly the same with the mufflers off vs on, on all bikes without any changes? Oh really? Are you saying the exhaust system is designed from the exhaust port to the collector without considering the muffler that will go on it? Don't you think that might change the pulse wave by creating a restriction from the muffler? Not many factory mufflers I know of are straight thru. They hold back and rearrange the noise waves (pulse) to tone it down. On performance bikes like the CBRR bikes it’s most likely less loss than say a Goldwing or VTC.

“To say that the EPA would make a manufacture 'de-tune' an engine due to regulations is just silly.”

I never said that. In actuality that happens. The EPA won’t tell them to de-tune. They will just say here are the regs, you build to them. If de-tuning gets you there the easiest/cost effective guess what?

“However, because most modern day bikes have such long exhaust pipes, most people and shops cut off up to 12 inches of the pipe in order to allow for an acceptable cosmetic appearance for the muffler. This changes the pipes tunability and will effect the scavenge, which will require a lower a/f mix as well as an advance or retard in the timing to compensate.”

Or really, even on VFR’s and the like. Your talking chopper now, not the bike type that this post originally started with. So Harley is doing pulse type exhaust tuning to get hp. Yea right. You don’t really know how it’s going to effect the motor until you can get actual test on it. To state to retard or advance timing is going to fix that is just wrong. Ignition timing has nothing to do with exhaust gas pulses for these discussions. This I would like you to show me.

“This is the most true for two stroke engines, and is defined by the bulbous exhaust just after the initial bend. That's not the muffler, that's just how much back pressure the exhaust wave needs to provide in order to keep the engine running properly at high rpm's.”

It’s called an expansion chamber. Totally different animal compared to a 4 stroke we are discussing. Apples and oranges again.

“yet how can you say now that it doesn't exist in real world engines?”

I never said it doesn’t exist in real world engines. I said it doesn’t exist in most production engines in the real world. There are exceptions to everything. Like purpose built race cars/bikes that are sold on the street. (Yes they are there and they are like hens teeth) Mainly because of design costs, testing and all the variables that can change it. Like a minor cam change and they are going to redesign the whole exhaust system to get the pulse timed perfectly. That you would have to show me.

The result of running open pipes on ANY engine, be it a car, bike, or diesel engine will all result in the same thing. A loss in hp (the ability to reach speed quickly) and a loss in effective torque (total power).

I know you haven’t dealt with Top Fuel or Top Alcohol engines now. Or FI tractor pull engines and such. I guess we have to take those straight pipes off and bend them up to get more power. Real world experience would change your mind.

Your class grade = C


You made the comment you can’t change an exhaust system and expect to make more power. You say you will have to rejet for better A/F ratio. Guess what that’s all part of changing the exhaust, or air filtration or anything on an engine. Then again there are exceptions such as if the bike was on the rich side (which the mfg’s favor) it just might come out right on the money. So it is possible. Never say never. Most likely naa you'll have to minor tinker with it.

When you build engines for performance everything is a compromise. Someday you may find that out like I did. The more I know, the more I don't know.

 

End of discussion.

Ok, this is getting a bit off the debate side and a bit more towards bashing and that's not my intention, nor am I cool with that. I stated facts, you voiced opinion. I backed up facts, you supported your opinion. At no point did I slam your integrity... at best I pointed out that I believed you didn't just look up the info online and act like you knew what you were talking about.

You guys went off on a tangent about car engines and how they weren't any better today than they were 30 - 40 years ago. So I threw in some knowlege that I had out there to help prove a point, but you missed it and instead chose to get all high and mighty about it. Whatever.

Honda, Sir, was created as an engine manufacturing company that turned into a motorcycle company with one point in mind... to be the best motorcyce on the racing circuit in the world, while providing the consumer with the fastest, safest, most economical transportation available. That was Mr. Honda's dream, and he stuck to it. Within 3 years of building his first racing bike, Honda Motorsports not only dominated every race they entered, but they completely revolutionized the motorcycle industry and have been on the cutting edge of R&D for the past 60+ years. Only recently (1970's) did they branch out and begin mass manufacturing cars and watercraft, which they put the same amount of dedication and integrity in development and cutting edge design as they did with their powersports lines.

That's the only part of your last post I'm going to defend. The rest of your retort is nothing but opinion and intentional slamming using automotive analogies that don't hold water when it comes to motorcycle engine design, which if you haven't noticed is quite different from the designs and mechanics used in building car engines as you said that you have done. I would NEVER allow an auto mechanic to fix my motorcycle, just as I would NEVER allow a motorcycle mechanic to touch my car. Two different styles, two different theories.

I shared this banter of yours with several people in class tonight who are very familiar with the topics at hand. Most of them shook their head and passed you off as that crusty old guy in the shop that thinks because he worked on cars most of his life that he knows everything and can fix anything he touches, and when he's proven wrong instead of backing down and learning something he just flares up, gets pissy and kicks you out of his work area.

I'm attending one of the best schools out there for learning the theory and design of the common motorcycle, and am 3 weeks from completing the training program designed by Honda taught by some of the best experienced instructors in the industry that have not only turned wrench on hundreds - in some cases thousands - of bikes before deciding to pass on their knowledge, but a few of them actually worked with the race teams and did the exact job that you so blatently state doesn't exist or is impossible to do. If you really want to learn something, then open your eyes and listen. Take the time and take a tour of a school like MMI and ask the instructors about your doubts and questions... better yet, go back to school and learn it yourself.

I'm not a top student by any means, and I'm still learning every day... but if I come on this site and open my mouth about something, it's not stuff I'm just pulling out of my ass. Either it was taught to me in class or it's in the 2,000+ pages of notes sitting on the shelf in my garage. And if I don't know the answer to something, I am humble enough to say so and get the right information from trusted sources before sticking my foot in my mouth. Just saying.

 

I'd like to apologize to you, Ward for the unintentional takeover of your post here. I didn't think it would escalate to this level of stupidity, and I'm sorry.

For the record, I side with Tink on the holes in the can theory... not that it matters since you already bought a really nice set of pipes. Hope you enjoy them, and yes... post pics. I'd like to see them. And if you get curious like we are, throw her on the Dyno and show us how she runs with them.

Happy riding, Sir!