Exhaust Q & A

[RangerFabWorks]

Ok, thanks BW67.
Hey, are you a LI Jets fan?

yes but what brings that up?

 

[Bondo]

yes but what brings that up?

Dunno, I just noticed you were from LI.

3 decade Jets fan myself!

 

[RangerFabWorks]

Dunno, I just noticed you were from LI.

3 decade Jets fan myself!

sweeeet!!!!

 

[2Lo4Snw]

The only time any great amount of backpressure is "needed" is when there is a large amount of valve overlap. Meaning both the exhaust and intake valves are open at the same time. Excessive overlap can cause fresh intake charge to be "scavenged" out the exhaust before it has a chance to be compressed and burned. Backpressure in this situation helps form a "barrier" to cause the intake charge to stay in the combustion chamber before escaping out the exhaust system. We see this in a lot of motorcycle sportbike applications where compression ratios reach over 12:1 and there is a lot of valve overlap. Works similarily to 2 stroke theory with exhaust pulses/waves (backpressure) blocking the exhaust port to allow the incoming intake charge to stay in the combusion chamber. 4 Stroke design benefits from this theory but just not as extreme of a case as the 2 cycle design.

 

[whale]

threadjacked thread necro?