Verdict on quiet(er) exhaust options?

I've done a ton of searches on exhaust options for the CRF150r, but can't really find anything definitive except the OE exhaust is a really good performer and there is no quiet muffler.

Aside from grafting a CRF250x muffler, are there are there any quieter cans out there? Q4 is usually the go-to solution, but have not found any sound output comparisons.

Edited by mjruopp

We have a power core w/SA and right now it's just a tad bit quieter over stock with worn packing. Problem is you can not go quieter without loosing power on this bike. End cap w/SA and quiet insert or the CRF250X muffler are your only options for true quiet exhaust with the CRF250x muffler being the quietist but also the most noticeable power loss. Simple to fab up, use a Lexx muffler strap or like and grind off the CRF250x bracket. Bolts right on with a removal of a side plate bumper. Aftermarket slip-ons are only quiet for a couple of hours then just as loud as stock. If you want to keep it quiet, repack every 5-10 hrs but that not too practical.

I've seen threads on the 250x muffler and the 150f/230f mufflers adapted.

Looks like the 250x is the easier adaptation, needing only the rear mount location moved or an aftermarket strap used.

The 150/230 muffler looks like it needs the inlet pipe and forward mount cut/fabricated; looks cleaner than the X muffler.

Anyone with experience available to comment about installation, weight differences, noise level/quality?

I've seen threads on the 250x muffler and the 150f/230f mufflers adapted.

Looks like the 250x is the easier adaptation, needing only the rear mount location moved or an aftermarket strap used.

The 150/230 muffler looks like it needs the inlet pipe and forward mount cut/fabricated; looks cleaner than the X muffler.

Anyone with experience available to comment about installation, weight differences, noise level/quality?

 

I don't have any comparisons because my bike had a Q4 on it when I got it (no s/a). First, I installed a plain s/a, to be Forest Service legal. Then I came across a s/a w/quiet-core insert, and it did reduce the sound a bit. I replaced the Ti Powerbomb with an SS Megabomb and noticed a further reduction in sound output. Subjectively, it seems about as loud as my old XR200R when the baffle fell out. It is probably still not quiet enough for responsible trail riding, but, ironically, the local dealership says the combination of Megabomb and Q4 w/quiet-core will pass the Colorado State Patrol inspection for a plate.

 

Between the CRF250X and the CRF230F muffler, the latter looks like more work, but I agree that it looks cleaner. I'm trying to get weights on them to help me make up my mind which way I'm going for my next try.

 

CRF250X; http://www.thumpertalk.com/topic/966657-crf250x-silencer-installed-on-crf150rb-pics-of-the-install/?p=10104435

 

CRF230F: http://www.thumpertalk.com/topic/367049-too-loud-for-me/page-3#entry3318170

I don't have the actual weight of the 250x muffler but it felt like 2x and 1/2 the noise output w/baffle. Because the 250x muffler has a larger pipe and you loose power, the 230 would just choke the 150r. If you loose that much power, sell the 150r and add better forks to a 230??

I don't have the actual weight of the 250x muffler but it felt like 2x and 1/2 the noise output w/baffle. Because the 250x muffler has a larger pipe and you loose power, the 230 would just choke the 150r. If you loose that much power, sell the 150r and add better forks to a 230??

 

I hate the weight gain more than the loss of power. The guy who did the 230 can dynoed his bike before and after: lost about 2hp up top (19.6 to 17.4), and said that on the trail he didn't miss the power. Still much quicker  and more agile than a 230.

When I did the 250x muffler, the motor response was much slower, lazier and just lost the fun factor.

When I did the 250x muffler, the motor response was much slower, lazier and just lost the fun factor.

 

I'm guessing that the problem with the 250X muffler is that its larger flow capacity slows the exhaust gas velocity, creating back pressure. To get engine response back in situations like this, the usual fix is to "cam down" with shorter timing and less overlap. For some applications, that's not a bad thing, since what you get back happens earlier in the powerband.

 

I wonder if a scaled down Flowmaster style chambered can would work on this engine? Mechanically, they're pretty simple, but getting the right proportions would take a lot of experimentation in the absence of the proper equations.

 

 

Anybody have any ideas on how to design such a can, and if it would even fit on the bike?

Edited by Old Plonker

Would be nice if the 150 had dual cams and you could vary the valve overlap and test the results without having to get a new cam.

I'm guessing that the problem with the 250X muffler is that its larger flow capacity slows the exhaust gas velocity, creating back pressure. To get engine response back in situations like this, the usual fix is to "cam down" with shorter timing and less overlap. For some applications, that's not a bad thing, since what you get back happens earlier in the powerband.

 

I wonder if a scaled down Flowmaster style chambered can would work on this engine? Mechanically, they're pretty simple, but getting the right proportions would take a lot of experimentation in the absence of the proper equations.

 

 

Anybody have any ideas on how to design such a can, and if it would even fit on the bike?

I think that the can would be much larger then what we have today. Do we have the room on the bike?? In the end I don't feel it would be quieter.

Some good points made here.

I suppose the 150r has to make good use of a free-flowing exhaust to make good power from that displacement.

A multi-chamber design to get quiet is a bit too restrictive. Indeed, it would be nice to have DOHC to play with timing and overlap.

I was hoping a Q4 or similar free-flow design would provide acceptable sound attenuation with minimal impact on performance.

I think that the can would be much larger then what we have today. Do we have the room on the bike?? In the end I don't feel it would be quieter.

 

Back to reality: the CRF250X can weighs 6.5lbs, the CRF230F can weighs 5.3lbs, and the FMF Q4 weighs 3lbs. Is half the sound worth twice the weight? Yeah, if we want to keep our trails. Argh. The Q4 with the s/a quiet core is quiet enough to be street legal. Is that enough? I'm looking for someone with a sound meter to test it.

Edited by Old Plonker

Kicking myself in the ass because I passed up a new-open-box Q4 last week for around $150 on fleabay. Will continue to be on look out...

15 or so hours on our powercore and it's just as loud as stock. Time to repack??

I should add that the SS MegaBomb took a little edge off of the Q4 at the most offensive frequency. The Ti PowerBomb that it replaced seemed raspier.

Chuck has an interesting thread over on the XR200R forum:

http://www.thumpertalk.com/topic/749867-uncorking-a-xr200r/

He tested the CRF250X can against a bunch of others, and chose it over the others so far. His results don't necessarily apply to the CRF150R, but he knows how to think.

I'm going to have to try a CRF250X can for myself.

:) Edited by mjruopp

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