installing baffles in drag pipes???

[rustynail99]

ok guys i have a set of gordon scott drag pipes (amazing pipes by the way!!! highly recommend his work! ) i was thinking about possibly putting some baffles in them like these

http://www.tcbroschoppers.com/store/index.php?main_page=product_info&cPath=25&products_id=77

anyone done this mod? are they worth buying? i am leaving my drags pretty long because i do want some decent back pressure.

 

[bloodthirstysystem]

you could just weld a flat washer to a bolt and drill a hole on the underside of the pipes.. there isn't really "back pressure"..

just having some restriction in pipes will interrupt the pulses of exhaust created by the motor and the air rushing back in after each pulse.

"These install inside your pipes to restore back pressure and eliminate popping and backfiring when tuned properly" - not true. properly jetting carbs will fix that. notice how they say "when tuned properly". even with those baffles you will need to tune your carbs

you know when a harley goes by with straight pipes and in between gears they make this disgusting backwards sound of exhaust? that's what baffles fix..

 

[rustynail99]

ok, well i definitly know what the bike backfiring is, and i know no matter what you have to tune your carbs to your setup, but if they will not improve performance then i dont think i really need them, especially if i can tune the carbs to eliminate the backfiring and popping. these baffles are probably for people that are keeping there drags shorter since it creates less backpressure. i think when i get it runnin ill see how it performs and then possibly do the washer mod. thanks!

 

[Ironsled77]

"The disgusting backwards sound " ...... I live for that. My Shovelhead has straight pipes its the shit.

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[bloodthirstysystem]

haha sorry ironsled. when i hear it i think of the motor throwing up everywhere..

baffles are needed to be street legal in most places.

i've heard guys talk about how it changes the performance but i'm not sure of all that

 

[Ironsled77]

Ha its cool. Don't much follow the law around here. There's no inspection and as long as you don't have a gun or a beer in your hand they leave you alone. It had baffles in it when I got it andwas the first to go! I think it runs better than ever.

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[grizld1]

"Back pressure," eh? Don't confuse the resonant pulses of a tuned pipe with restriction. You want the scavenging pulses and reversion pulses in the pipe to work to evacuate the spent fuel charge and retain the fresh one (during overlap); adding restriction doesn't accomplish this, it only kills power. The tuned length of the pipe should be selected according to where you want peak hp to hit, and diameter according to where you want the torque peak to hit. Snuffers and baffle inserts in straight pipes are much more restrictive than free-flowing mufflers, real performance robbers.

 

[angus67]

i put those in my 1 and a 1/2 inch home made drags. they are 36"s long. had to do something to qiet it down while I fuss with the carbs , or ide go deaf. those will deffinately quiet it down.took most of the 'snap' tone out of it. Its no rumbler though.

 

[gordonscott]

"Back pressure," eh? Don't confuse the resonant pulses of a tuned pipe with restriction. You want the scavenging pulses and reversion pulses in the pipe to work to evacuate the spent fuel charge and retain the fresh one (during overlap); adding restriction doesn't accomplish this, it only kills power. The tuned length of the pipe should be selected according to where you want peak hp to hit, and diameter according to where you want the torque peak to hit. Snuffers and baffle inserts in straight pipes are much more restrictive than free-flowing mufflers, real performance robbers.

Perfecto! could not have said it better myself Try them without the baffles first and post results. P.S The pipes are 1.5od and thanks Rusty for the compliment, glad you like them

 

[rustynail99]

thanks guys this is exactly the answers i have been looking for. Michael over at 650 central that sold me my vm34's said to just try the pipes longer see if i like it and cut from there. so i think im going to leave them as long as gordon left them for the time being. plus they look freakin kool like that! lol and seriously for anyone reading this thread GORDON SCOTT IS THE MAN!!! he hooked me up with great pipes for a great price and was extremely patient with my dumb questions! real stand up guy! so give him a call! (wouldnt say it if it wasnt true!)

 

[Georelle]

I was just looking into doing the washer trick last week. I found this in my search.

http://www.nightrider.com/biketech/exhaust.htm

It is an interesting read. According to their tests the washer smooths out the mid range.
I am sure differences in pipes and motors will have different results.

Georelle

 

[rustynail99]

thanks for that Georelle, i will check that out. if i decide to cut them down, i will probably try that first just to see since i would be cutting it off anyway. let i know if you do this mod and how it turns out!

 

[gordonscott]

Hi Guys, I usualy to do not voice much opinion on this subject anymore but like Griz said " The tuned length of the pipe should be selected according to where you want peak hp to hit, and diameter according to where you want the torque peak to hit" It's as simple as that! Everything else is voodoo and witchcraft Look at some of the Harley chops, some of the pipes are no where close to equal length but sacrifice is made for looks over perfomance, I guess it's whats important to you that matters in the end I read the link posted by Georelle ( Hi Georelle ) and again if the pipes were proper diameter and length there would be no need for anything else. Here is a piece from "The Horse" it sums it up best.... "Backpressure? One of the common misconceptions I hear is "you need more backpressure"This is about the same as "you need more choke"and makes about as much sense. The engine needs to move air in, combustion products out, or "breath"if you prefer. If you want backpressure, try farting through a boatswain's whistle. An engine's displacement is constant, but its volumetric efficiency can be maximized. The basis behind backpressure is not completely wrong though, as at first it seems that leaving pipes off would allow the maximum amount of exhaust to escape. But, this leaves only the upward movement of the piston to push the gases out after the initial pressure release. Properly sized pipes route the combustion products such that their velocity sucks out the remaining gasses that the piston can't push out. If the pistons push out 80 ci the pipes could help pull out the remaining 10ci that the heads hold. On the other end of the scale, a pipe that's too restrictive doesn't allow all the gases to escape."So in short a great system can give you a little extra perfomance while a bad one (to restrictive) can hurt perfomance significantly. Try it without the "mods" first and let us know?

 

[rustynail99]

Gordon that was what i was planning on doing after you and grizled recommended that i try it without. just gonna leave them long and see how that does. then go from there. and i certaintly cant argue with words from the Horse. i actually remember reading that article i think, but it was a while ago if i remember? anyway, thanks for the words of wisdom

 

[Georelle]

Hi Gordon- That all makes perfect sense to me. I definitely was not counting on a performance improvement by using the washer trick. I originally started looking at a cheap way to quiet the pipes on a '78 Honda CM185T somebody gave me. I just got it running and it has some "custom" straight pipes on it and it is way too loud for a little 180cc bike. Then when I found that link above I thought about trying that on my '02 Suzuki Marauder that has had the baffles removed. I used to like the sound of it but that "disgusting backwards sound" or as others have called it the "jake brake sound" is getting on my nerves more every time I ride it. It might sound good on an HD shovel but not the Suzuki VTwin.
By the way I am quite happy with the sound of my 650 with the short tapered mufflers. They probably aren't tuned real well however.
Ride Safe
Georelle

 

[gordonscott]

Hi Georelle, I have used the taperd mufflers too and performance was great and I think they sound fantastic! It's amazing how different some mufflers can sound even when the design is very similar. I have used glasspacks, reverse cones, taper tips etc.... and they all sound different.

 

[Georelle]

Yep. I have the exact same as in the top picture. It is good to know they perform well. I have never had any other pipes on my 650 to compare. They do sound great.

 

[Dillrepair]

ok so i have a related question... before i bought my 650 someone else had installed some aftermarket mufflers by cutting the stock stuff off the headers just behind the pegs... i wanted to ditch them and encountered the significantly decreased performance i had read about, was going to just add a small bit of exhaust tube on the end of the headers and put a baffle in but now what i want to know is :
what is the right length? I wanted to keep them short for looks but i'd rather have it run nice so how much tube should i add to the headers? i'm going to have to find a way to attach everything and support it... i don't have a welder unfortunately.

 

[jamesgs4]

you can jet your carbs up to match the increased flow from removing the muflers, instead of adding a new restriction. no welder needed.

 

[Dillrepair]

yes i already increased the jetting in anticipation of this mod. perhaps that needs further modification as well but I'd like to know a ballpark length to shoot for with the pipes.