In V6 engines where there is more than one exhaust bank, X-pipes work on the same principle of using the low pressure component of an exhaust pulse from one bank to increase the velocity of the next exhaust pulse from the other. Linking the two banks of the engine in this way more closely times the exhaust pulses increasing velocity and VE.

 

Makes sense, what do you mean by VE though?

 

First of all, I was not trying to disagree with you. No need to get so defensive. It is true that turboed car needs exhaust velocity, but it is different from from N/A cars. While you want the biggest catback that maintains high exhaust velocity in an N/A car, turboed car would benefit from the largest catback you can slap on there period. Downstream of the turbos, no restriction is more important than exhaust velocity. That's all I was trying to say.

I dont think there's a need to question anyone's credibility. I'm one of the very few people that installed a TT kit on the G37. I wouldnt count that as a bolt-on. I've done extensive research on the topic.

If you expect all comments to be "oh mike you're so great", and bark at anyone that challenges your ideas, then I think it's time to grow up.

 

Volumetric Efficiency

 

I believe the term you're looking for is "scavenging effect".

OP, great post. I agree that back pressure is often misunderstood/misused.

 

Of the engine or of the exhaust piping? Can you elaborate please?

 

I guess you could say of the engine by way of the exhaust design or based on the system as a whole.

 

"Scavenging effect" is the end result but I thought it would serve Sam better to explain how X-pipes work as opposed to just throwing out terms.

 

 

Aaah makes sense now, what's the difference in scavenging effects between x-pipes, y-pipes and h-pipes though?

 

Good read

 

I'm not sure what the difference between X and Y pipes are for net gains, but I do know that properly engineered H-pipes will have the same performance gain as a X pipe. The key is that the exhaust pulse overlap on the H-pipe has to be the same as an X pipe for the performance gain to be the same. The difference is the sound; X-pipes give a higher pitched sound, while H-pipes give a lower sound. (Think regular Vette with a catback and stock H-pipe [which btw is crap], and a Vette with a X-pipe and catback)

Z06 with Exhaust

YouTube - 2008 Corvette Z06 with Corsa Exhaust and CAI - Auto Addiction ltd

Z06 with Exhaust and X-pipe

YouTube - 2008 Corvette Z06 With Corsa Mufflers and X Pipe By Serious Autosport


Note how the first clip has that typical "beefy american muscle" sound, while the second one doesn't.

 

I dont know much about exhaust, and your write up gives a good idea of how it works. thanks for the write up.

question: Several people after changing exhaust components such as HFCs or full catbacks sometimes develop the hissing sound on deceleration around the cat converter area. is the sound due to pressure and velocity? is air flowing reverse and back into the engine?

 

Awesome. Love technical stuff like this. Thanks.
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If you're here to learn, check out these articles:
!Header Basics
Tuning the LET - Exhaust
The truth about exhaust backpressure and torque

This is neat in that it shows how important each and every part is in an engine. It's about collectors but still applies somewhat to the discussion at hand. If nothing else, read the last paragraph on this one:
http://www.jgenginedynamics.com/Adob...collectors.pdf


I'm still looking for a specific one that I can not find right now.