Exhaust , torque, PSE, etc

[JimB]

I have a 99 996 race car with a 2004 3.6L X51 engine. All we are allowed to change for club racing is the intake and the exhaust. I have the Evo intake. For the past year I have had cats followed by straight pipes. Last week I removed the cats and replaced them with six inch pipes running from the end of the header out the back of the car. We put the "pre cat" O2 sensors in the pipes and hung the "post cat" sensors in clean air.

The good news.

First, I took 32 lbs off the back of the car. I was already at the minimum 2910 so I had to add the weight back in but it's much better on the floor in the middle of the car than hanging off the back bumper.

Second, I removed a huge source of heat from right below the air intake.

Third, I added 13 rwhp at 7000 rpms.

Finally, she's scary loud and blows fire. No racing value but still fun.

The bad news.

The car has a ton of scoot over 5500 rpms but absolutely dies under about 5000. Unfortunately we did not dyno below 5000. I'm going to redyno with and without the cats tomorrow but I already know what the results will be. Tons of power from 5500 on up. No torque below 5000. This is not all bad as a race car spends a lot of time above 6000 and not much below 5000 but when you do the car is a pig.

The question.

The solution seems simple to me. Add a baffle that adds back-pressure at low RPMs but opens up at the point the torque curves cross.

The challenge.

How am I going to put a variable baffle in my straight pipes?

Does anyone know how they work on PSE?

Any other ideas?

Thanks,

Jim

[X911CarreraX]

you can try to put butterfly valves on ur exhaust, and you can open it at speeds above 5500,but thats manually open it...and im sure you dont want to manually open it at 5500 when ur racing. Maybe you can try to find some thing that will make it open at a certain time. kinda like the PSE..

[Costa]

Jim - The PSE works by utilising a vacuum operated valve.

The vacuum line(s) are passed via a electronic solenoid which in turn controls if there is vacuum applied to the valve or not. This way you can switch the PSE from on to off via a switch on the dash - note that it just has two states On/Off.

On the factory fitted item - the solenoid signal is fed via a relay which turns the PSE sound off (normal muffler sound) within a certain speed range (uses speedo sense signal) - most people disable this feature.

Perform a search on Loren's forum for the PSE for more info

Also see http://www.renntech.org/forums/index.php?showtopic=491

[JimB]

Thanks for the info although I know how PSE is activated. It is easy to install an RPM switch that will send 12 volts at a given RPM. In my case I could set the switch to send power (or remove power) at 6000 rpms. What I'm curious about is what is happening inside the exhaust. Has anyone seen a diagram that shows what is happening inside? If not, has anyone seen an application where a baffle is adjusted real time?

Thanks again for the help.

Jim