Back pressure

[gs650girl]

My exhaust on my gs650 now has an open pipe coming off of each header but I need to create some back pressure. What is the best way of doing that without making it a lot quieter? I looked at torque cones but I'm not sure what size would fit the best or if they even make small enough ones for the 650s. Any suggestions would be appreciated!!

[Zooks]

Put the mufflers back on and be done with it. The bike will run better and you'll go a long way to helping to create peace with the 'general public'.

Loud bikes annoy lives!!!!!!!!!!!!!!

[brveagle]

I heard that an exhaust can/baffle works wonders improving back pressure.

[Clone]

Back pressure but keep the noise
well, one or the other, to create backpressure and not cook the exhaust valve you would need to slow the flow by PUTTIN' ON A MUFFLER

[wkmpt]

Bananas in the tailpipes create a ton of back pressure.

[drhach]

Why do you need to create backpressure?

[duaneage]

I'll give you a serious answer since we have heard all the jokes so far.

You can use pipe fittings that accept reducer inserts to restrict the diameter a bit. I would take it down about 20% initially and see what happens. Check out the plumbing section at lowes or home depot for ideas. jetting will need to be adjusted accordingly. If you can monitor the heat of the pipes with an infrared sensing tool that would be a plus.

Mufflers are preferred but it's your bike and OK if you want an open exhaust. Just don't drive it past my house.

[Hammered]

You can also run baffles. Threre are several types. They will alter the sound of the open pipes but theres really no way to increase back pressure without altering the tone.

Lollipop baffles

A set of cones turned around backwards

Or spiral baffles

[drhach]

Backpressure is one of those things that you hear over and over. It is a misnomer to say the least. Valves don't burn because there is no "back pressure" on a short exhaust they burn becasue part of the function of an exhaust is to provide cooling. A short exhaust will not do this effectively. You can have a pipe diameter the size of a pencil or a watermelon. If it isn't absorbing the heat and dissipating it, your valves will burn. period. Nothing to do with backpressure. Please people, stop talking about back pressure.

What you are probably losing by removing your mufflers is velocity and momentum. those pipes were sized with the intention of running mufflers. If you are going to run straight pipes (which most of the planet would prefer that you didn't) you should consider reducing the diameter of your exhaust. How much you ask? Who knows? Suzuki did all of htat experimenting for you and they thought that you should have a muffler. Think of it this way a wider river will tend to flow slower than a narrow river given the same amount of water. Wide slow waterways are also generally more stagnant that faster ones (hint hint) With your now too wide pipes, things slow down too soon and the momentum that the exhaust gases have is lost. The gases collect near the exhaust port and basically there isn't enough oomph for them to get all the way out of the cylinder. So your next charge of air and fuel is now tainted with spent gas. Hence the running poorly. Again it is not backpressure, it's just the ability of you system to move the spent gases the way they need to be moved.

Unfortunately the correct answer for getting the bike to run right just gets more complicated. Maybe there are some people here who have already done all of the experimenting and can give you some baselines. But it will still require a lot of tinkering. OEMs spend millions of dollars and hire teams of very talented researchers to sort these issues out. The seemingly innocuous act of cutting off a muffler has far reaching consequences.

[gs650girl]

Thanks guys for some actual answers! In all reality, it really isn't that loud, it might be the way that we created the pipes on it. A stock Harley could blow it out of the water on loudness...and I'm not planning on driving like I stole it...if anything it's more for the looks of straight pipes. Duaneage- thanks for the ideas, I think that is what I'm going to end up doing and then re-jetting it as well. drhach-thanks for the explanation! and Hammered thanks for the picture

[tone]

With 4 open pipes you can use VW beetle baffles, very cheap & reduce the noise without restricting the bike too much

Backpressure err no what you are all refering to is the scavenge effect where the exhaust fumes swirling is around is used to help pull in the fresh air/fuel charge this can be achieved without any baffles or silencer on a well designed & made exhaust