View Full Version : High Idle

02-28-2012, 06:05 PM
I have installed a Supermeg on my 01 Heritage. Previoulsly had Stage 1 with SE air cleaner and Double Barrel 16 Ga pipes.

My Supermeg is quiter and runs great with no popping on decel. However its seems like Idle speed is higher than it was with previous setup and milage is lower. Any ideas??



02-29-2012, 12:32 AM
On my motorcycles, the fewer the diffusers the higher the MPG, the fatter the mid-range and flatter the top end. The higher the diffuser count the lower the MPG, the flatter the mid-range, and the fatter the top end.

How many diffuser discs do you have on the bike now and what other numbers have you tried?

02-29-2012, 08:02 PM
Thanks for the reply.

I am currently running 14 discs. I thought about 12 but haven't tried yet. Also using closed end cap.


03-02-2012, 08:56 PM
Mine's closed end-cap too. Don't fear experimenting with the number of diffusers, that's what you're suppose to do. Only you will know what type of performance you are looking to achieve.

With a large displacement engine, you can experiment with more than two, if it helps you narrow which direction you need to go quicker. I started with six, went to eight, ten and twelve, before finding that eight was just about perfect. Went to seven, meh! Went to nine, perfect!!!

03-05-2012, 12:36 AM
Thanks again. Was looking for less noise and low end torque. I'll try 8 and work my way up.

03-05-2012, 01:53 AM
Less noise comes from greater muffler volume (as in muffler capacity) and more fiberglass packing. Each model of SuperTrapp will have different characteristics. Mine is fairly noisy or so I think. When I ask my neighbors they all say 'hell no, it's not loud enough.' I think they like it. :cool:

03-05-2012, 08:08 PM
My wife says the Supertrapp is quieter that the 16 Ga Double Barrel I had before. Whatever makes mama happy :)

03-12-2012, 04:27 PM

Went from 14 disks to 12 and seem tohave quiteted down idle and runs about 20 degrees cooler. Still pulls very good.


03-14-2012, 08:48 PM
I can't imagine that there would be that great of difference between 14 and 12, but who am I to say otherwise!?

If you like, keep trying different # stacks and if you have a caliper, measure the distance the diffusers cover. You may find later on that your bike likes an odd number like 11 or 13, but when you check the diffuser distance, it may end up the same as previously recorded 12 or 14.