I have a pocketbike expansion chamber. I am pretty happy with my top speed, but if I could get a little more torque, that would be great. I am wondering if I drill one small hole at a time into the side of the silencer, would I gain torque? I probably only need to drill one or two holes. I have half decent torque, but I can only climb some hills. others I need to pedal. and I'm not feeling the chamber kick in at lower rpms, where I mostly want it. its ok if I lose a few mph in top speed. hill climbing is where I want the chamber to come on at. would drilling into the silencer accomplish that? I would drill one small hole at a time and test ride until I got the torque I want. I don't have the option of modifying the length of the pipes, so lets refrain from suggesting that.
need advice on drilling into side of xchamber silencer to gain torque
- Thread starter bigbutterbean
- Start date
Drilling holes into the silencer will only make the exhaust louder. Any performance gain would be negligible and in your head due to the louder sound. If you want more low RPM power you need to increase the length of the header pipe between the cylinder and the belly of the pipe. Shortening it will increase the high RPM power. The pipe will "come on" at whatever RPM you tune it to. It will not act like a magic exhaust and increase power across the entire RPM spectrum. Proper carburetor tuning, ignition timing, correctly porting the cylinder, and higher compression will help produce a wider power band.
Even match porting the intake, transfer ports, and exhaust will help out alot if you do nothing else.
Even match porting the intake, transfer ports, and exhaust will help out alot if you do nothing else.
first, I already mentioned that adjusting the length of the pipes wasn't an option. since you missed that part, I will explain why. I already modified this exhaust. I cut it apart and fiberglassed it back together because I don't have access to a welder. I painted it with bbq paint to seal it and protect it from heat damage. so that covers that. now on to the powerband. I have this bike as tuned as its gonna get. I'm not porting or adjusting my timing. I'm not jetting. my fuel mixture is right so I'm not changing anything on the carb. also, I didn't say I wanted to magically widen my powerband. I said I wanted more power at lower rpms. I don't care about my top speed. here is my thinking. I do know one thing about xchambers and its this. hotter gases increase power at higher rpms, and cooler gases increase power at lower rpms. therefore, the cooler the gases in the expansion chamber, the more power at lower rpms. I also know that a less restrictive exhaust makes the gases in the chamber cooler. so, drilling into the silencer should make the exhaust less rrstrictive, thus cooling the gases in the chamber and giving me the power I want at lower rpms. I'm not looking for a lot of gain. just want to stay on the pipe when climbing hills.
You didn't bother to tell us what rear sprocket you're using. If you want more hill climbing ability that's where to start. Not drilling holes in the muffler.
Tom
Tom
if I needed advice on sprockets, I would have posted in that section. I don't have money for a different sprocket. nor do I have extra chain to put a bigger sprocket on. I have to be honest. everything I have learned about mb's I have learned by doing, despite having posted on here many times for advice. the reason for that? I ask specific questions that do in fact have specific answers. but people always try to answer them in their own ways. so after not getting a specific answer on here, I always go figure it out myself. so thanks, but I will once again figure it out myself. despite having been a member of this forum for over six months, I have yet to gain any substantial knowledge from questions I have asked on here. I have always figured it out myself. it would be very simple to answer a question yes or no. I didn't ask for other ways to increase hill climbing power. I asked if my idea would work. I still think it will. I will indeed figure it out myself.
if, as gearnut said, drilling into the silencer wont have any effect on the powerband, then I have nothing to lose by trying it, because it wont hurt anything.
My advice? Don't post anymore questions here. You have repeatedly admonished people who have offered you advice and help with rude comments and put downs. If you have no appreciation for those who offer help then it would be to your benefit and ours for you to not ask for it.
Good luck "figuring it out for yourself"
I know how you made your exhaust system.
I know that is it 'glassed together.
I posted in that thread.
I know how exhaust systems work, from a design and engineering standpoint to real world outcomes.
I shared with you my knowledge of silencer performance versus what you propose to do with yours.
I shared with you what is required to change the performance aspects of an expansion chamber exhaust system, regardless of what you are willing to do with yours, what you need to do to get the results you stated you are looking for.
I know that is it 'glassed together.
I posted in that thread.
I know how exhaust systems work, from a design and engineering standpoint to real world outcomes.
I shared with you my knowledge of silencer performance versus what you propose to do with yours.
I shared with you what is required to change the performance aspects of an expansion chamber exhaust system, regardless of what you are willing to do with yours, what you need to do to get the results you stated you are looking for.
Given your 6 months of frustration, perhaps you would enjoy looking for the answers you'd like elsewhere. May I suggest the following;
Motor-Assisted Bicycling
Motor-Assisted Bicycling
i love it!
he says he can't alter the header. fine.
he asks if his idea will work. check
advised physics that are tied to our universe will prevent what he wants. check.
given other option. check.
OP doesn't like other options & belittles people trying to help him.
OP is but hurt that physics won't let him have his way.
possibly OP wanted someone to lie to him.
he says he can't alter the header. fine.
he asks if his idea will work. check
advised physics that are tied to our universe will prevent what he wants. check.
given other option. check.
OP doesn't like other options & belittles people trying to help him.
OP is but hurt that physics won't let him have his way.
possibly OP wanted someone to lie to him.
He just needs a serious attitude adjustment. If you really want to have a LOT of gain in low end torque here is what ya do. EVERYONE will notice it......tie a skunk on your xchamber! Watch that skunk low end power! It is really over whelming!
Terry
Terry
he doesn't even realise that if he changed gearing that it wouldn't only give him the gearing for power @ lower speeds, but it would also run @ a higher rpm where his current chamber is tuned to. so he would have even more power.
My though on this is since it is your exhaust you should do what ever you want to it, but on the other hand everyone has his on idea of what will work. These guys know what they are talking about.
The longer exhaust pipe before the expansion chamber = better low end power. The shorter the pipe will result in better top end performance, if your bike is setup for top-end. If your happy with your top speed then then making the pipe longer should give you what your looking for. A good balance for both top-end and low-end power is roughly 10''-14'' of pipe before the chamber. Maybe you should make the pipe 16''-20'' 
reading through this thread, I see a few members talking crap and making fun of bbb after he was banned. he was obviously banned for being disrespectful. maybe its the first time he did it, maybe not. but he isn't here to defend himself. where is the respect in that?
It wasn't the first time. The guy doesn't show people who help him any respect. Repeatedly. Hope that answers your question.