661 Muffler Mod Test - need opinions..

[redbull660]

Gearing up to do another 661 muffler mod test. These are the 3 I am thinking of testing. What do u guys think?


1st combo - just a larger opening with stock cover and baffle

2nd - stock muffler (rear half) but with a dual port cover I made. The hole in the dp cover is .625"...should I make it bigger? Idea here is just to get the exhaust out in a straight line as fast as possible.

3rd - large exit port (similar size to combo #1) and half the baffle has been cut out. Idea here being, less restriction to the exit port.

 

[MustangMike]

Looking forward to seeing the results. Wondering if you keep opening the holes up if you hit a point of diminishing returns, or if the idle gets shaky or throttle response is diminished.

 

[blsnelling]

At least on a ported saw, I can tell you that the strongest MM is removing the baffle and adding lots of exit area. These aren't tuned pipes. The more free flowing they are, the more efficient "the pump" will be.

 

[blsnelling]

Looking forward to seeing the results. Wondering if you keep opening the holes up if you hit a point of diminishing returns, or if the idle gets shaky or throttle response is diminished.

Mine idles and runs perfectly with no muffler cover at all.

 

[redbull660]

I think you can go too large. I tested a muffler that moparmyway modded. The outlet was opened up a lot! i.e. hogged out top to bottom and all the way back and a good deal of the way forward with a very open screen. This setup was running about 2 seconds slower than me just opening the stock setup from .625" dia hole , out to about .90" dia hole.

However it worked well for him because he modded his air filter to use the max flow setup.

Brad - did the muffler rear half, have a baffle in it, when you ran/tested with out a front cover on?


Guess the main question I have here is should I go to a larger opening on the front cover?

 

[Marshy]

Over scavenging can become an issue though can it?

 

[blsnelling]

Brad - did the muffler rear half, have a baffle in it, when you ran/tested with out a front cover on?

It did at that time. I did lots more testing later and found that removing it is ideal. Others have found the same to be true as well.

http://www.arboristsite.com/community/threads/ms661c-muffler-mod-testing.281169/

 

[MustangMike]

What happened to cut times from a modded muff to no cover?