Page 1 of 4

Posted: Fri Feb 27, 2004 10:18 am
by stevec
Now that I think of it, I did hit 60 once in my LJ10, going down a long hill when I drove it to work. That was the morning the flex pipe split on me; I got flipped off at least 5 or 6 times from the noise. At least I couldn't hear what they were saying! It was that same afternoon, on the way home, when I blew the seal on a rear wheel cylinder...needless to say, I haven't driven it to work since.

It was the most I've driven it in a day (70+ miles roundtrip), and feeling it run with the cracked exhaust made me think that a better designed expansion chamber would give it more power. I've been researching expansion chambers over the winter, and I've crunched the numbers on a two-stage chamber that (hypothetically) would maximize the output. I'm going to talk to some people in my 4x4 club and see if I can get one made. I'll let you know how it turns out if and when I get it done!

Posted: Fri Feb 27, 2004 7:42 pm
by Jimny
SWEET on the Chamber.....I checked into it once too, there is a guy in Tulsa OK that can figure what type, size etc for a chamber and build it too, but I have not been able to find out his name.

Posted: Mon Mar 01, 2004 11:19 am
by stevec
Figuring out the dimensions isn't hard if you're a math geek like me...I've just got to find someone who can make the cones correctly...after that, it's just welding the pieces together.

Posted: Mon Mar 01, 2004 6:49 pm
by Jimny
Math? Is that what they were trying to teach me in school? It's not my fault I don't know math, I went to school in Kansas.

Expansion chamber

Posted: Mon Mar 01, 2004 8:59 pm
by russmehl
I know a guy who is really good with stainless..... a for-ever expansion chamber?
Does this mean there are no exhaust parts left?
Russ

Posted: Tue Mar 02, 2004 5:28 am
by Jimny
I think you will have to put the same type of "stuff" Suzuki used in their expansion chambers to keep it quiet. If not I bet it would sound like a Comanche or a dirt-bike. I am wondering if back then they used asbestos.

Ceramic fiber?

Posted: Tue Mar 02, 2004 6:03 am
by russmehl
My first thought is to use glass wool (yeah, man... I'm running a glass pack") and then I wonder if Ceramic fiber would last through the vibrations... there should be something cheap and easy to get.
Russ

Posted: Tue Mar 02, 2004 6:06 am
by Jimny
Glass packs on a LJ? COOL!!!!!!

I have a set of glass packs on a street rod and they handle the vibration. That'sa good ideal!!

Numbers

Posted: Tue Mar 02, 2004 6:08 am
by russmehl
Got to run it by the numbers guy...
Russ

Posted: Tue Mar 02, 2004 10:14 am
by stevec
I'm sure the original ones used asbestos, or some other cancer-causing agent that is illegal now. The first step is to build one that will optimize the LJ engine's power (or at least so better than the stock exhaust!). Once that is done, then an outer covering can be made that will act both to quiet it down as much as possible, and also act as a heat shield.

Glass packs are illegal on most trails around here, as they are not an adequate spark arrester, but this usually refers to using them as a muffler. With a proper muffler behind it, that shouldn't be an issue.

Russ, there are no new LJ10 exhaust parts left. For the LJ20, the manifold gasket is still available, but I don't think much else is.

Expansion chamber

Posted: Tue Mar 02, 2004 11:10 am
by russmehl
So what have people done... snow machine, cycle? Not good enough if your crunching numbers...
Russ

Posted: Tue Mar 02, 2004 2:16 pm
by stevec
Jimny, didn't you use a Polaris x-chamber once?

I'm sure if you look hard enough, you can find one off an ATV or snowmobile that will work ok. I tried locally, but didn't see anything that would match up well, so I decided to look into making them. Plus, I'm not looking to just slap something on that works, I want it to be either OEM, or better.

Posted: Tue Mar 02, 2004 5:41 pm
by Jimny
Yes I did, I had it on Zuk10 for a while. I think I might have lost the low end but not much. The best way is to make one exactly for an LJ.

Posted: Wed Mar 03, 2004 10:32 am
by stevec
That doesn't surprise me. A simple (one-stage) expansion chamber can help a two-stroke engine generate a lot of power, but makes for a narrow power band. With a two-stage chamber, you can tune it to make power through a much longer band. I would guess that your's allowed for power at higher rpms, which sacrificed power at lower rpms.

Posted: Fri Mar 05, 2004 10:35 pm
by Smuz
You guys got WAY too freakin much time on yer hands.

Posted: Thu Apr 01, 2004 5:31 pm
by russmehl
I've been having educational conversations with my resource people... one of whom was a professional cart racer many years ago. He suggested that what I really wanted was a "slippy pipe". This is an expansion chamber that can change length as your needs change. Novel idea... he says he might just still have one in the shop. Anybody else have experiance along these lines?
Russ

Posted: Thu Apr 01, 2004 6:49 pm
by Jimny
No experience but I want to know more! I'm going to do some Internet reading on that subject tonight.

Posted: Thu Apr 01, 2004 7:58 pm
by Smuz
You didn't tell me you could read.

Smart alec!

Posted: Thu Apr 01, 2004 8:03 pm
by Jimny
As long as they have lots of pictures!

Posted: Tue Jul 20, 2004 9:07 am
by stevec
Smuz wrote:You guys got WAY too freakin much time on yer hands.
Haven't done a thing with this in months, so you're wrong on this point, smuz! :roll:

Posted: Tue Jul 20, 2004 10:29 am
by russmehl
SteveC, did you ever get all the numbers crunched? I've discovered a guy in our complex with a roller, and he seems willing to let me use it or roll some stock for me. Like I've got much time... but it needs doing.
Russ

Posted: Tue Jul 20, 2004 12:32 pm
by stevec
I think I've got 'em at home; I'll have to look...

Posted: Mon Jul 26, 2004 3:58 pm
by Crossthread Fred
I would be interested in those numbers too, Steve. I think I know of a good fab shop that could make an expansion chamber for me. My LJ never had one when I bought it, so I would be curios to see the difference.

Just a cool side note. The muffler that was on it was rusted out so I cut it off, and replaced it with a silencer from a Honda CR 500. It exits right above the rear axle, and sounds great too. Plus the silencer is serviceable(re-packable)

Posted: Tue Jul 27, 2004 4:14 pm
by Crossthread Fred
Nevermind those numbers Steve. I think I may have found that software you were talking about at http://microcarproject.tripod.com/html/ ... oftwar.htm

Some pretty cool info there. :cool:

Posted: Thu Jul 29, 2004 3:08 pm
by stevec
Yup, that looks like the formula I was using. I think the only factor I couldn't find was the exhaust duration, but it seemed like I did get it. I'll have to dig that stuff out at home.