Yesterday if someone had bet me a thumbscrew like this in my open pipes would make a performance difference I would have bet them it wouldn't.



And I would have lost my money.

1997Bagger posted up this video yesterday and I've never seen the exhaust reversion explained so well.


When I went from mufflers to open pipes I felt the mid range power loss. But they sounded so much better I've just dealt with it. I've been modding and racing Vettes and other cars for years, chasing tenths at the drag strip, so my butt dyno is pretty well tuned. I bought a PCIII tuner from Fuel Moto with a custom tune for my mods but it didn't do much, cut back on decel popping but fuel mileage went way down and power was the same so I took it off to get my mleage back.

This dyno result in the video opened my eyes. I feel that dip from 2500-4000, which is 60-85 mph or so. The lower dyno is the open pipes, then the thumb screw at 45 degrees, then 90 degrees, all compared to S&S mufflers. As you can see, the 90 degree thumbscrew gives back about 15 of the 20 foot lbs lost from open pipes. The video explains reversion in a fashion anyone can understand using the slinky.



Well, for $1.18 at home depot and a few minutes to install the thumb screws where baffles would go, I had little to lose.

I am amazed at the difference, for sure you can feel the 15 rwtq being given back by two silly thumb screws. This is right at highway mph on my bike, and the bike is noticeably snappier and pulls harder when passing at part throttle.

For those with open pipes, I highly recommend this mod. Best $1.18 I've ever spent on mods.

 

Welded a big *** washer on the end of my baffle and it made a big difference ...mellowed my sound a bit....

 

That's interesting...

 

I should have stated, this thumbscrew made no change in sound. Running at pretty good throttle in an entrance ramp that is kind of a tunnel I thought I heard some tinnier sound to the exhaust, but it could be my imagination. It's still open pipe loud which is what I wanted.

I do get a kick out of the video when it said trying to fix an exhaust problem with jetting is like fixing a headache with an arm sling. Well now I see what he means - I bought an expensive tuner that is now a paperweight on my bench! Wish I'd have seen this video before I bought it.

 

lollipops are an old drag racing trick thats as relevant today as it was 30 years ago. Its a go to mod with any street bike I've ever run with an open exhaust. I prefer a large washer on the end as it gives the ability to add maximum back pressure if needed.

 

My bad, I realized after I posted...I do feel I got a bit more back pressure but I only think that because I found, I might gave got a bit more power out of that but no scientific proof here....

 

Found a good video which graphically shows why 2 into 1 systems work better than single drag pipes. Something I've known, but this simple example shows how one pipe will draw exhaust out of the other pipe. This is a 4 into 1 collector but you get the idea.

I'm thinking I should weld on a reverse cone shape on my thumbscrew... lol


I guess my factory head pipes are more or less 2 into 1, but I will say, the left pipe on my softail is a lot louder than the left pipe on my Road King and it was basically the same system. On the Road King 90% of the sound came out of the right pipe. Not sure why that is.

 

lollipops are effective, the Patented Thunder Torque Inserts (which is a highly refined lollipop) are much more effective...and deepen the tone some.

At the link above you can see dyno charts...or you can just install them and your butt dyno will notice the improvement right off.

 

Do these things add anything to (for example) V&H Big shots? If so, why haven't V&H already added them given the tiny cost? *confused*

 

They aren't necessary if you have baffles in. Baffles or lollipops break up the sound waves - it's the sound waves which prevent proper scavenging of exhaust gasses at certain RPM's (right at highways speeds) as demonstrated in the video.