Thinkin about some true duals (bub 7) for my scoot. Just don't want to lose any torque at lower rpm's so I was thinkin about the baffles. I have the tuned baffles from fuelmoto in my rush mufflers ( stock exhaust ) right now and notice that the baffles have a small rod that runs across the baffle exit. I've heard that this is an old trick to add a little back pressure and increase torque. Just wondering if you could take the baffles out of the mufflers on a true dual setup, install a small rod across the baffle exit and have the best of both worlds! All the advantages of true duals and no torque loss. Just wonderin.......

 

First of all, unless you have a very sensitive butt (Never thought I'd ever say those words to another guy) with good quality duals you won't notice the loss of torque on a properly tuned bike.

As for the relationship of backpressure and 2-into-1 pipes - my understanding is they may produce similar effects (potential lost, or increased, HP/TQ) but for different reasons.

With an exhaust that is either too large (pipe diameter) or too open (short straight pipes), and therefore low backpressure, reversion of the gas flow can be a problem affecting the filling of the cylinders with fuel and air. The exhaust can flow back towards the open exhaust valve and polute the intake charge. This will happen with 2-into-1 pipes as well as duals.

The reduced low end torque people claim with true duals is caused by a reduced scavaging affect within the pipes. 2-into-1 pipes scavenge better than (short) duals because each cylinder fires into the same pipe which helps provide a vacuuming effect on the next cylinder to fire drawing the exhaust out of the pipe and helping fill the cylinders with the intake charge. Properly designed true duals and good quality mufflers can reduce the difference between the two types of pipes. For example, a good design might incorporate longer or smaller diameter pipes, which keeps the exhaust velocity high and helps provide a similar vacuuming effect. Poorly designed or restrictive 2-into-1 pipes (i.e., Stock H-D 2-into-1 pipes) will hurt performance just as bad a poorly designed duals.

What I'm trying to say is, I wouldn't worry about the duals vs. 2-into-1 so much, and guessing at the amount of back pressure you need to add to increase torque is probably a waste of time. Just buy good mufflers to go with your duals, get it tuned and ride.

It's been years since I first learned most of this so forgive me if I fumbled the words a bit. There's probably others here with better retention of the facts that can correct me.

 

I have Rush slip ons. It is my understanding that the rod you reference is there so you can remove the baffle or at least this is how I used it when I removed my baffles to repack them.

I don't know if it has any impact on back pressure.

 

You might try these Quiet Riot

 

Thanks for the reply's. I was just sittin here an sometimes I start thinkin up stuff.......

 

This is like you've been watching my house, kind of like you're stalking me.

So two days ago I got my BUB7 "Quiet Baffles" delivered and then you post this, creepy man!

So the BUB7's look great and totally solved the heat issue from the exhaust pipes and sound good but are a tad too loud for me.

So I spoke with the BUB folks and ordered the baffles. I am a bit concerned because they look very suffocating compared to the regular free breathing baffles but I should be installing them Friday night and I will post a new thread about them shortly thereafter with a little report on them.

I have heard no mention of anyone on the board using them so I really have no idea what to expect. The BUB guy told me to expect a little more low end torque due to increased back pressure.

We shall see.

 

Cool, looks like your the guinea pig. I didn't know they had a quiet baffle. Let us know what happens, by the way can I have a slice of that pizza!

 

I knew it