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Discussion Starter · #21 ·
I cut the pipe I ordered into the pieces I will need. Now I need to go to my muffler guy and get the pieces expanded so they will slip over each other and so I can install the spark arrestor in the end. It looks like there will be clearance with the bed in the dump position.

Artic air here next week so after that will measure the before sound level then put it on and measure after. I have been doing other things so had some time today to mess with it.
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Thanks for the update and pics.
Keep doing so!
 

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Discussion Starter · #23 · (Edited)
Here is an interesting article about choosing exhaust pipe size. Looking at the chart you can see why Polaris chose the 2" pipe diameter for the 1 liter 100 hp general engine. 1 3/4" size would have been the minimum for our engine which needs a pipe size that can flow 250cfm minimum.

So by using 2" to account for any bends in the pipe there is always more than enough flow because the bends never drop to 1 3/4".
 

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Discussion Starter · #29 ·
Artic air here this week. Next week I will take the general out and measure the db in the cab and from behind at idle, cruise rpm accelerating. Then I will get the resonator on and measure the difference.

I bought a stopwatch to measure 0-40 times before and after because someone thought adding the resonator would cause a loss of performance. I dont expect any difference in performance but will measure anyway.

So it will take next week to do the before and the next week to do the after only because I want to have actual data to validate the results.
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Discussion Starter · #30 ·
Finally got out with the general and measured the db. I measured in the cab by my ear as this is what you are hearing. At idle is was 80db, pretty quiet. At about 4000rpm riding along it was 90db, mild acceleration up past 6000rpm it was 95. Full throttle applications were 100db.

Acceleration from 0-40 using hi range averaged 4.8 to 5 seconds.

I am hoping adding the resonator will drop the cruising db at 4000rpm down to 85, 6000rpm down to 90db and full throttle down to 95db but I think that is being a little optomistic. I think it would make for a more pleasant experience trailriding. The engine itself makes a lot of mechanical noise.

If any one has the HMF twin loop quiet system it would be cool if you could measure it for comparison.
 

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Discussion Starter · #31 ·
Today I left it at the local welding shop I use to get the pieces welded together and the pipe welded on. Should get it back next week and will get the results posted.
 

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4-5 decibels is a significant difference
 

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Discussion Starter · #34 ·
Got it back from the shop today. They did a awesome job. I bought some black exhaust wrap to wrap it. Will take it out Friday and measure the db again and see if there is a change.
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Discussion Starter · #36 ·
I wrapped it. am going to take it out this afternoon and measure the db
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and the accel again from 0-40. I reinstalled the spark arrestor too.

Isaw another thread where someone measured the before and after on the hmf twin loop quiet system and got a 10db reduction at cruising speeds. That is a lot! I dont want to spend $800 for that system so am interested to see if I get any reduction with the resonator. The fab shop guys I know charged me $50 to weld it all together so I am into this experiment for about $160 so far counting the wrap and metal zip ties.
 

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Wondering if you are going to have to put a hanger on that pipe? Could put a lot of pressure when riding off-road on that muffler exhaust port.
 

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Just saw where it looks like you tack welded a rod onto the exhaust end of the new pipe from the inlet pipe to the muffler.
 

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Discussion Starter · #39 ·
yes its braced up with that rod pretty stout and the tailpipe resonator is really light. Its welded to the outlet of the muffler too so its rock solid
 

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Discussion Starter · #40 ·
I got to give it a good test today. Acceleration from 0-40 in Hi range avg 4.9 seconds so no change there.

idle 67db previous was 80db
4000 rpm 82 db previous was 90db
5000 rpm 85 db not measured previously
6000 rpm 90 db previous was 95
Full throttle 100 db, no change from previous

All tests were done in Hi range. I do have a front winddhield, no back windshield. I am happy with it as cruising speed in Hi range for me is 5000 rpm and at 85db I can have a conversation and the volume at 85db is fine for me.

At full throttle still loud, these engines make a lot of racket at full throttle, a lot of mechanical noise besides the exhaust. I was really just after a decent noise level at cruising speed. I was really suprised how much quieter it was at idle.

This mod cost me $160. Your results could vary depending upon the skill of the fab shop that welds it together. These guys make beautiful smooth welds and really help me with my projects as a favor because they dont make any money at it really. I mean $50 and a case of beer, deal...

When you have the bed open for maintenance there is about a 1 1/2" clearance to the pipe. If I open the tailgate with the bed in the raised position the tailgate does contact the pipe. Its a compromise, I never use the bed as a dump bed so was not a issue for me. Will take pics of the clearance
tomorrow.
 
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