| Author | Message | ||
| Jim (Jim_in_california)
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Guys, something's been bothering me for a bit now. MANY years ago I used to screw around with fast two-stroke street bikes - Yamaha RD350s and such. Fast as hell and equally unstable  . But the thing was, to get real performance out of a two-stroke (gas) engine, the design of the entire exhaust system was *critical*. Not just length and pipe bore, but backpressure and "expansion chambers" - pipes that went from narrow to extremely fat back to skinny. These are typical, for a two-cylinder bike - one complete pipe per cylinder: http://www.pro-flo.com/images/dg_pipes.jpg These are good for up to 30% more power over stock when combined with re-jetting (what we'd call "swapping injectors" in the bus world). Is there any degree of similar engineering going on with DD 2-stroke diesel exhausts? | ||
| Doug Wotring
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nope.....a DD will run just the same with no exhaust....just make more noise whole different princicple involved on a diesel | ||
| TWODOGS (Twodogs)
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ditto............. | ||
| Marc Bourget Rating: N/A |
They do all those cute things on MCs to generate a "negative" pulse back at the cylinder when the port's uncovered. DD has things like valves and does the "scavenging thing" with a rootes type blower Moi | ||
| jimmci9 #2 Rating: N/A |
yes... detroit has definite specs for the exhaust tubing... diameter mainly....each particular engine has different needs.. whether its a 53, 71, 92, 149 or 110 series... | ||
| Henry R. Bergman, Jr. (Henryofcj)
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Actually 2-stroke Detroits do require some tuning in the exhaust system. I believe jimmci9 #2 got it exactly correct. We had to do this stuffing 353 and 453 Detroits into Ford pickups years ago. A longer exhaust pipe made a big difference. | ||
| Marc Bourget Rating: N/A |
True, MHO, what the motocycles do is a quantum level higher on the exhaust pulse "technology scale". Shoulda thunk more about it before I typed. And, I don't mean to diminish Jim's comments or DD's efforts, they're "right on" for that setup. | ||
| Jim (Jim_in_california)
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Huh. Well it's still an argument against homebrew exhaust systems, at least without doing a bit of research. FOUR stroke exhausts are yet another story and it would shock me to learn that the engineering between gas and diesel was too much different. On a four-stroke, you want a "merged pipe" where the merge point is determined by how far downstream from the heads you are to allow one cylinder's discharge to be barely past the merge when the next one is coming into the top of the pipe. The previous pulse acts as a suction for the next, and so on. You can do this with 2, 3, 4, 5 or 6 cylinders all at once. On a V6 or better you do separate merges each side and then dual systems past each of the two merge points. That's how they run best anyways. The pipe interior diameters determine where the engine makes power. On a four-stroke, the motor won't make big power until the pipe "fills up" (visualization tool only, not "really" correct) - bigger pipe, takes longer to fill, power hits at a higher RPM but there's more peak power on tap. Smaller pipe, power hits sooner, more bottom-end grunt but you run out of oomph sooner. Common crankpin engines like a Harley are weird in yet other ways but let's not go there. Still, on bikes it's the two-strokes with the most elaborate engineering needed and I was wondering if that carried over to the DDs. | ||
| TWODOGS (Twodogs)
Rating: N/A |
all the dragster guys will be glad to get your information | ||
| Jim (Jim_in_california)
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They're supercharging and running a buttload of valve overlap impossible on anything streetable even discounting smog laws...you make big power ONLY on the top end that way. With lots of overlap on the cam, the intake and exhaust valves are both open a good bit of the time. Then when you supercharge, you're stuffing through there at a hell of a clip. You don't need suction on the exhaust. It's inefficient but it makes BIG power. Briefly. A NASCAR motor uses merge pipes exactly as I've described. | ||
| Brian (Bigbusguy)
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I was told buy the top DD tech at Wyotech . The detroit 2cyl runs best with wide open exhust and the less back psi the better. I will open up mine some more. I already cut out most of the baffels in my muffler I get more air blowing out of it but no more noise . Brian 4905 Klamath Falls Oregon | ||
| truthhunter@shaw.ca
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While on the exhaust topic, if any one has knowledge of first hand experiience on wraping the exhaust with insulation, or good types of material to use. My goal is to keep the heat contained in the exhast system and out of the engine compartment without a big cost, effort or risk! -are there any dangers, damage risks or performance concerns if one were to insulates the exhaust system from the mainfolds right out the the tail pipe? I have a 1975 MC 8 -8v71 HT 740. | ||
| FAST FRED Rating: N/A |
"are there any dangers, damage risks or performance concerns if one were to insulates the exhaust system from the mainfolds right out the the tail pipe?" If the engine compartment isn't rain tite , or the fender mud flaps are missing , the insulation can get wet , and the steam looks a lot like smoke. Hamilton Marine in Maine has a catalog and sells the NON ASBESTOS insulation wrap youre looking for , 800# , give them a call. FAST FRED | ||
| Jim Shepherd (Rv_safetyman)
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On the subject of exhaust insulation, several speed shops sell an insulation that you can wrap around the pipe. The challenge is how to insulate the manifolds. If you look at my bus project page (below), you will see how I did mine. I carry the material that you use on the manifolds Jim Shepherd Evergreen, CO ’85 Eagle 10 http://rvsafetysystems.com Bus Project details: http://www.rvsafetysystems.com/busproject.htm (updated 2/17/05) | ||
| Jim Shepherd (Rv_safetyman)
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A little off the subject. Down the board a bit, I started a thread on mufflers for a four stroke. This involves a Series 60 in an Eagle. As a result of that thread, I found a possible solution to my problem, but would like more input from you folks. Also, it might work on a two stroke (back on subject). The part of the thread I would like input on is: I ran across an “internal muffler” or muffler insert (http://www.iowa80.com/iowa80/shop search for item 08301). This is a device you insert inside a 6 inch diameter pipe. It is intended for a truck exhaust stack, but I would use it in a horizontal application. The insert is really interesting to me. My problem is that if I have a relatively large diameter (10 inches or greater) muffler, I don’t have any length to work with (get your minds out of the gutter <grin>). If I can stick with 6 inch diameter, I think I can get the 72 inch length I would need for the insert. Does anyone have any experience with this kind of “muffler” for this size of application (they are used in motorcycles and some custom type car applications)? Does anyone know who the manufacturer is (did a google search and came out empty handed)? Jim | ||
| Brian (Bigbusguy)
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Any one know how much noise a non tubo 8v71 will make with no muffler? Im looking on running my exhust up to the roof in my rear cap. So if it was up high would it still be to noisy with no muffler? Also I was thinking the slop it spits out does any one think it would be a problem raining oil goo if I had it piped to the roof? Brian 4905 Klamath Falls Oregon | ||
| TWODOGS (Twodogs)
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brian....4 stroke diesels sound great without a muffler....not the case for a two-stroke | ||
| Gus Haag (Mrbus)
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Brian, If you run your 8V71 with no mufflers, even out the top, we will probably be able to hear you in Minnesota. And if you use a Jake Brake, they will hear you in Florida. Gus Haag | ||
| Gary Carter Rating: N/A |
I had the muffler gutted on our 4106. A friend was following us in the smoky mountians and told me when I hit a hill it sounded like a herd of Harley's. | ||
| Nick Morris (Nick3751)
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I just started mine today for fun with no muffler period, only idled for a few min. but wasn't any louder at idle than with the muffler all in one piece. | ||
| Brian (Bigbusguy)
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Well I guess I will need a little muffler. I also idleded mine with no muffler when I was repairing my factory muff it was also was not any louder then with a muff. But under a load Im sure it would be loud. Brian 4905 klamath Falls oregon | ||
| FAST FRED Rating: N/A |
" think it would be a problem raining oil goo if I had it piped to the roof? " Most of the oil all over towds comes from engine LEAKS , not the exhaust. You would definatly need a rain cap and some sort of drain to keep the engine exhaust from filling the cylinders when not in use. On dry stack work boats , we simplly use an inverted pail over the stack end. Might be a hassle in a destination park. There are MANY inline truck mufflers that would work well with a roof stack, why no kindness for the rest of the world? FAST FRED | ||
| Brian (Bigbusguy)
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"why no kindness for the rest of the world?" If its too loud your too old Might be a hassle in a destination park. ?? What ever that be I wont go there. There is two types of loud one that sounds good like a built 8v gas motor running headers and flowmasters . Or the bad type a honda type car with a stupid looking oversize muffler hanging off the back and sounds like a chain saw all noise no go. Also 3406 with 6" open stacks sounds cool too. Brian 4905 Klamath Falls Oregon The sound of my bus will arrive 10 min before me. | ||
| Jim-W Rating: N/A |
Brian, I have heard my 8V71/4905 without any muffler. It's not too bad idling, but when revved up it must be 140 Db! It really HURTS your ears standing at the engine working the throttle. I am certain that you would get "cop stopped" going through many small towns climbing a hill on a two lane. Many go right through residential neighborhoods. I'm 50 and I guess I'm too old. Jim-Bob | ||
| Jim (Jim_in_california)
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My brother ran a Toyota Supra with basically no muffler...had a header dumping to a SuperTrapp hollowed out right under the passenger seat, no plumbing at all back of that. This was on the twin cam motor and seriously tuned up...that thing would hit an honest 160mph. Anyways. As long as he short-shifted it around town and kept the revs down below about 2500 it sounded OK. And that would go to about 65mph in fifth. Wind it up to six grand and it sounded like an F16 taking off and it would go to match . Point here is that noise is VERY dependent on revs. | ||
| FAST FRED Rating: N/A |
"If its too loud your too old Might be a hassle in a destination park." This is the Mantra of the Hog folks that the world looks on at best as spoiled children , at worst as FOOLS! It would be sad to see the Bus Conversion campers looked on with the same distaste as the noise for noise's sake bike "riders". Why not do as I ask the Harley kids to do, re-route the exhaust FOWARD over the handle bars , sweaping back so the megaphones end a few inches from the "riders" ears? Would be great on a bus , you could grove on all the 2 stroke rapid power pulses! Could start a trend! Be sure the exhaust pipe come INSIDE the bus , so your friends don't miss a thing. FAST FRED | ||
| truthhunter@shaw.ca
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Fast F has a very novel solution that has the potential to satisfy everyones needs. So much for that old clechae "you can't please everyone". | ||
| uncle ned
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have a short muffler on my 6v92 in my 04.about 18 inches long, sets beside the 730. just get a good sound. | ||
| Brian (Bigbusguy)
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It sounds like some Harley rider must have kicked FF walker out from under him he dont like them. There is nothing better sounding then the sound of a good Amercan made Harley. If I had a tubo it would be easer to use a smaller muff. Right now my muff is as big as a 55gal drum. I do like the idea of the inserts for the 6" pipe . I will look to see if they make em for 5" then I can add them as needed to get it sounding right. Im thinking I should be able to have reduced temperatures increased horsepower increased torque increased fuel economy less engine wear & tear with a lower back pressure and have a good sound also. Brian 4905 Klamath Falls Oregon | ||
| RJ Long (Rjlong)
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Brian wrote -"There is nothing better sounding then the sound of a good Amercan-made Harley." Agreed, but: As you are well aware, Brian, there are some Harley riders that are of the "SEE ME, SEE ME!" mentality, blatently making a racket just to draw attention to themselves. Then there are the majority of HD folk who love their bikes, but take the responsible position of being "good neighbors" to those around them. Obviously, Fast Fred was addressing the former group, not the latter. Gotta understand Fast Fred - The majority of his posts are designed to make you pause for a moment and THINK (often slightly "outside the box"), even when written in his notoriously tongue-in-cheek style. The problems arise when people misinterpret his humor and believe they're being "dissed", which is NOT his intention, 99.9% of the time. He is opinionated, like we all are, he just wants us to think intelligently about what we're doing. And it works! Look at how often people react, positively and negatively, to his posts. That's EXACTLY what's he's after when he writes - people to think about what he's said and respond to it. Makes for lively "cuss & discuss" sessions which then benefits all. Personally, I think THIS sounds a whole lot better than a Harley: http://www.pacbus.org/flash/detroit.swf FWIW, RJ PD4106-2784 Fresno CA | ||
| truthhunter@shaw.ca
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Just as I was starting to think I could find a way to respect Fast F you have to go and ruin it. Thanks alot RJAY | ||
| FAST FRED Rating: N/A |
"There is nothing better sounding then the sound of a good Amercan made Harley" Happily its NOT a sound heard for too often , as most hog noisemakers prefer being parked and stairing at their antique design, and all the shiney chrome do dads, leaking fluids. On most long trips there are more hogs layoing dead in the back of a pickup , than actually driving! THANKFULLY!! | ||
| Ron Walker (Prevost82)
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God Fred.. you must be still living in the 80's. Harley's reliability has greatly improved in the passed 20 yrs. The wife and I rode our Harleys from Vancouver BC to Keywest and back, without any break downs or "leaking fluids", we didn't think twice about riding harleys on this 10,000 mile adventure. We go on a 5000 miles ride every summer and have over 100,000 on our bikes, neither bike has ever seen the back of a pickup. A friend we ride with has over 180,000 miles on his hog. The days of breaking down on the side of the road is about as common as with a new car. Ron | ||
| Brian (Bigbusguy)
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What was that old saying . "Buy a Harley buy the best ride a mile walk the rest" LOL they be better now. I may get a hog noisemaker one day but will have to buy used the new ones cost as much as my house. Brian 4905 noisemaker Klamath Falls Oregon where its 4200 feet and all up hill to get out of here. | ||
| truthhunter@shaw.ca
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Silence is golden to me, as I like hearing myself talk. However for those that can not get enough sound, I would have to give the designer's prize to Fast F for his "perfect compromise" solution. | ||
| gg04
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Jim..When I repowered my 04 it changed the exhaust from coming out the front to the rear straight off of the turbo with 6" pipe with no room for a muffler I just turned the pipe down the bumper and made a baffle out of 5" pipe a side grinder and hammer added the baffeling its located with three sets of 1" strips welded to the pipe to center it in the 6" exhaust..at first I also closed the end of the baffel off but after driving and playing with it I have removed the end cover..still has less noise than the old original duel exhaust...Make your own nothing to it..gg04 |
