Gassing your Pillion (HM1100)

[koko64]

My HM1100Evo comes with a DP 2 into 1 full system. Even at speed my pillion in a million gets gassed by the exhaust. It's fine solo, but I think there is an issue which a wind tunnel would show up.
The exhaust exits well behind the pillion, but I think the issue is similar to when we used to drive station wagons with the rear window wound down back in the day .
There is no such issue with my old M900, even though the pipes exit alongside the pillion (but down low).

I'm considering going to a stock system with the two mufflers, but this is no guarantee of success.
I have removed the DP wind screen in an attempt to change the airflow. I'll test that in a couple of days.

Meantime, anyone have any experience of this, or any solutions?
Cheers.

[Speeddog]

First silly suggestion would be to ride faster. 

I've not heard of the issue, but that's not worth much in this case.

I've had weird aero interaction between my pillion and my helmet, subjecting me to a bobble-head effect, very annoying.

Is this the system you've got?



Are you running the dB killer/insert?

[koko64]

That's the one. No DB insert. The bike came with it. If removing the screen doesn't help then I'm considering buying a stock system. It's the pillion bike.
Cheers.

[Speeddog]

Perhaps an 'elbow' that goes in place of the insert to direct the exhaust more horizontal and outboard may do the trick?

I'd say cobble something crude to bolt in there as an experiment, see if you can solve it that way.
May have to try a few different concepts.

Do you have a few 'test-pilot' pillions to do the donkey work with, then present the solution to the Pillion In A Milion?

[koko64]

Lab rat kids .

Maybe a modified DB killer ay?

[Speeddog]

Something like that, yes.

Just crude and simple stuff to try to get clues on which way to go.
Try to direct the exhaust down a bit and outboard to get it away from the zone directly behind the pillion.

Is the gassing occurring around town, low speed, or at cruising speed on the highway?

[koko64]

At all speeds up to 70 mph, much to my surprise.   Hwy was quite bad.
Tested on closed course conditions of course.

[Howie]

Nothing to add to Speeddog's suggestions.  Without a wind tunnel it is all guesswork.  My concern with returning to the stock exhaust is, with the cats, your Pillion might still be gassed, but without the stink as a warning. 

[koko64]

Cats, like squirrels, can be dealt with
Aint the cat cleaner?

[ducpainter]

Cats, like squirrels, can be dealt with
Aint the cat cleaner?

Cat is 'cleaner', but doesn't eliminate the CO.

[koko64]

  Its the CO Im worried about. 

[He Man]

buy a cheap smoke grenade (they used to sell 50 cent ones that last for 30seconds in the grocery store, or you can always make your own (they arent hard to make a home made one either)

they got hot, but thas easily solved. take one, light it up on a street and go for a ride!!! .

Science though, behind the passenger is low pressure, the exhaust is probably getting sucked into their burble.

nothing you can do about it unless you actually ride SLOWER to reduce the pressure gradient, or you redirect the exhaust. maybe you can change the cap without having to go with an insert.

[koko64]

Thanks fellas.
A twin system straight out the back would have to protude a fair way ay?
Or the current pipe less tucked in and angled straighter?

[koko64]

Lab rat 1 said that the fumes were worse sitting back than when holding on close. Also that the fumes became strong when I lifted my elbows (might need more deodorant). Smell went away with elbows tucked in. (How would Spies go)? Head over my shoulder no fumes noticed.

I'll get the GLW (pillion in a million) to try it with no screen and the pipe moved. Then if that works I'll try again with the screen fitted. A local exhaust guy could give a slight bend if needed.

I found the pipe can move down and out and inch or so. I'll make a bracket and try that. This test was with no screen, and to be honest I didn't notice much difference than with it on. Maybe less buffetting .

I may still get an oem system for other reasons.

Thanks to all you guys for giving me some direction with this. Love this place.
Cheers.

[ungeheuer]

...nothing you can do about it unless you actually ride SLOWER to reduce the pressure gradient....

Sounds like you're rooted Tony