Backpressure?

[warriorkid]

Ok, ive heard that a little backpressure is important on a quad. But if you think about it, you want to get as much air out of that head as possible. And having backpressure makes it harder for that air to escape since there is a force keeping it from leaving. So my question is, how important is it really, to have backpressure? My friend has an old lt230 that is a mess around bike, and he is wanting to put a total strait pipe on it. And if backpressure matters then we need to try somethin different.

thanks,
1fastyamaha

 

[yamarider]

With the way the exhaust system works on a small performance engine, the exhaust system is designed to actually create a vacuum between strokes to evacuate even more air than running straight pipes or even running with no exhaust system at all. Between exhaust pulses, my HMF actually pulls in mud, roots, and water flying past the end cap, just from the vaccuum that's created within the system. Which reminds me, I gotta clean that thing out and repack it soon, it doesn't sound as good as it used to.

But i'd say try to keep some kind of muffler on there. I doubt he wants to go through the trouble of rejetting the carb on a beater like that, and with running straight pipes he's probably going to be running lean without a rejet. Then he's running a chance of burning a valve or doing other internal damage. Not that it's going to be a big loss or anything, but it's something to keep in mind before he does anything.

 

[dave76]

It's a well known fact on a Harly, that strait pipes actually lose horse power, and some kind of baffle will aid in making HP. Strait pipes are good for one thing, making noise, that is unless you have a full race motor thats gonna run at it's highest RPM all the time and it is tuned for it. But hey even Pro Stock racing has gone to mufflers. They do exactly what Yamarider explained.

 

[ledain]

my HMF actually pulls in mud, roots, and water flying past the end cap, just from the vaccuum that's created within the system. Which reminds me, I gotta clean that thing out and repack it soon, it doesn't sound as good as it used to.

Ya i noticed my HMF Sucks in a ton of dust when im riding in the desert.

 

[warriorkid]

i didnt even notice taht about my HMF. but its been 6 months since i rode it, lol. I think when i re-pack it (sometime soon) im going to cut it down and make it a shorty. I made a custom tip for it that made it a little louder, so it should be a screamer if I make it a shorty.

 

[dswwarrior350]

i didnt even notice taht about my HMF. but its been 6 months since i rode it, lol. I think when i re-pack it (sometime soon) im going to cut it down and make it a shorty. I made a custom tip for it that made it a little louder, so it should be a screamer if I make it a shorty.

The hmf can is already too short in my opinion, cutting down isnt going to do much but make it louder.

 

[warriorkid]

Well, arent yoshimura pipes louder than HMFs? And for some reason people still cut the yoshi's down, right?

 

[mattd]

Someone told me that you cut the pipe to get more low end torque so thats probably why people cut the yosh.

 

[warriorkid]

yea, i forgot to mention that...lol. So as well as adding more noise, it will give a little more low end.

 

[dswwarrior350]

Well, arent yoshimura pipes louder than HMFs? And for some reason people still cut the yoshi's down, right?

They are not louder. They produce a deeper tone where the hmf is more crackly. All it is going to do is give you a slight boost in low end.. Im not exactly first in line to cut a 300 dollar stainless steel silencer to actually make my quad slower from a loss of topend power. The boost in low end is most likely next to nothing on a motor with only 20-22 horsepower stock. However you can give it a try and let us know how it works haha

 

[warriorkid]

its the same deal with the yoshi dude. Obviously it helps, because Josh(hotcams77c) cut it down. And he knows his way around motors. And how would i lose top end? Air in/air out. It will still have all the components of the muffler, just 3 inches shorter.

 

[yamarider]

You will be losing top end because the extra backpressure is what causes that vacuum that pulls the excess exhaust gasses from the cylinder. And it's not like the HMF needs to be any louder, nor does the Warrior need any more bottom end power. The warrior pulls like a tractor, especially when stock.

 

[bickel76]

i dont mean to jack this thread, but i'm sure that i need to re-pack my t4. has anyone ever used home insulation before? i've heard that you can use it but was just curious if anyone has experience with it.

 

[warriorkid]

You will be losing top end because the extra backpressure is what causes that vacuum that pulls the excess exhaust gasses from the cylinder. And it's not like the HMF needs to be any louder, nor does the Warrior need any more bottom end power. The warrior pulls like a tractor, especially when stock.

Could always be louder and have more pull. :

 

[dswwarrior350]

i dont mean to jack this thread, but i'm sure that i need to re-pack my t4. has anyone ever used home insulation before? i've heard that you can use it but was just curious if anyone has experience with it.

go buy some muffler packing.. its like 7 bucks at the most and wont burn out in one ride and smell like house insulation will
.

 

[warriorspeed350]

i tested backpressure of my WB's today.......just put a piece of paper up to it and it stays on the tip while the exhaust is still blowing out

 

[dswwarrior350]

The wb has a closed endcap doesnt it?

 

[warriorkid]

yea, it does...wtf are u talkin about Warriorspeed?

 

[imtarnished]

Not all of them do. If you have the E series, it would then have a closed cap, If you have the diffuser discs in, and not just running it open.
~Bill

 

[warriorkid]

He has the e-series and it has discs in it (atleast it does in the pics i saw)