Contour Enthusiasts Group Archives Forums Modifications Duratec Performance Torque Vs Backpressure...

OK guys, I'm 'calling you out'...keep hearing loads of BS how increases in torque,or loss of torque, are claimed by upping or maintaining 'backpressure'...,people running with gutted cats,MSDS headers etc, free flow less restrictive exhaust sytems then we harp back to 'must have back pressure'...SO to increase torque we need MORE backpressure right?...so who is going to be the first to 'neck down' either the Y pipe or part of the 'front end' of the exhaust to say 1" pipe to prove to us all how much torque you can get from restricting the exhaust????

This means war!

Just kidding!

I have no idea... but isn't it just to a certain extent? I mean, if you seal up the exhaust to a 1 cm opening, I don't think that's good.

And it all depends on Aspiration and whatnot, right?

I dunno.

I'm just bored.

Terry,

Is is true that you want the exhaust to flow out faster (higher speed)? I have heard mention of an optimal diameter piping, but was skeptical. Maybe we just care about CFM?

Aaron

Numbers says it all. We changed from very high flow cat to a lesser high flow cat, Run 21 to Run 26. Both were 3" inlet and outlet, the Hermoff has less pressure drop, meaning higher flow rate, than the CATCO.



On another topic, this is the results of what we got when the 180 bend was removed from the rear section of the Y-pipe.

Is it just me... Or does it look like the Superchip actually did something?

Terry- Please see my response to Dual Style Mustang Exhaust??? and let me know if this makes sense or not.

Thanks, 2112

Yup, that chip did do something. Out of all the chips that we have tested, there was something about this particular program that allowed it to work with a great number of changes. Got lucky, I guess.

An exhaust system can be designed/tuned to work best (most efficiently evacuate to the exhaust gas and return a reflected pressure wave to keep the fresh charge from going out the exhaust) at a particular RPM. The header length and diameter is determined by the RPMs (frequency) and cylinder displacement. An engine's power peak will, however, be primarily determined by the intake and cam lift/timing. If the exhaust is designed to force the torque peak to a lower RPM the ultimate torque peak will be lower. (If the exhaust is designed for a higher PRM than the rest of the engine, torque will be lost across the power band.)
Once you're past the headers, resonance tuning (length) doesn't have much effect. Once past the collectors I would want the least amount of flow resistance as possible.

Yes to all the above but my original question is backpressure & torque........

If you add backpressure, by making the exhaust more restrictive, the peak torque will drop. It may go up by a bit at lower RPMs though.