What about pulling the guts out of a "fly by wire" throttle body and use it to control exhaust flow? Like an electronic valve to change exhaust back pressure with either a dial or a throttle switch. This could solve some problems associated with loss of back pressure due to performance exhaust.

 

makes sense to me. Keep the exhaust restricted under low rpm, then as they rise, open up the flow so you dont loose back pressure and bottom end power, but then when your higher up in the power band, theres not too much pressure to restrict the flow

 

Can anyone explain how this whole back pressure thing works? It just doesnt make sense to me. The engine basically works as an air pump and if you want to get air in and out as fast and in the largest quantities as possible. I cant figure out how holding up the exhaust helps.

 

jcbst12, Smoke20 who used to hang out on here a lot was talking about doing this same thing. After doing a lot of research on it he eventually found a company who actually makes kits to do exactly this. I don't recall anything about it but you might find it with the search feature.... "might". It was a long time ago.

 

Yeah, I found a company that makes them but it costs too much for me. My idea was more "budget build" and less "new idea".

More back pressure on a gasoline motor = more torque. less horsepower to a certain extent.

Less Back Pressure on a gasoline motor = more hosepower, less torque to a certain extent.

The idea is to make as much torque AND horsepower as possible while gaining a MPG or two by controlling/manipulating the back pressure while driving.

 

It's a great idea becouse of the back pressure needed to keep the low end torque but gain the top end horse power. I wonder if the commercial one is based offthethrottle position or the RPM's?I could see it not working as well if it wasn't based off of the RPM's, that is the only way that I see it really working all that well. Then you would have to make sure that it was perportional to the rpms as they riseto make sure that you get the most out of the exhuast flow changes. It would be a lot of dyno trial and error, along with a computor controlled valve to control the exhuast flow to the dump. I think there is a similare system on the new Corvettes? So this is not impossible. That is what you guys are talking about right. Dumping the exhuast instead of just restricting the flow and going to full flow on the top end, but still within the exhuast system?

 

JCWhitney had a spring loaded butterfly-valveexhaust tips that used the backpressure to open and close it based on pressure and it was supposed to be the most efficient way to have consistant backpressure at all RPMs, but I can't find it anymore.

 

I think I may have one on my truck, in the old days they used a butterfly valve and it had a weight on the arm of it. When the RPM's went up the valve opened more. Take a look at an old set of stock exhaust manifolds, you may see what I am talking about.