Intake manifold design - New 997 GT2
07-18-2007, 06:03 AM
#16
Nordschleife Master
Originally Posted by Laust Pedersen
Increased back pressure is really increased exhaust gas recirculation (EGR), which reduces NOx emissions and lowers knock sensitivity, so it is not all bad.
but... how do you mean that increased back pressure would lower knock threshold??
07-18-2007, 01:58 PM
#17
Addict
Rennlist Member
Rennlist Member
Wow nice, so there actually are people reading my posts. 
As mentioned increased back pressure also means increased exhaust gas recirculation (EGR), which lowers the combustion temperature, again resulting in reduced NOx and knock sensitivity.
Here is one of many references, this on to an SAE paper on the subject with the title “Knock Reduction of Spark-Ignition Engines By Egr”: https://shop.sae.org/technical/papers/860034
Taken to the extreme you can also look up the Homogeneous Charge Compression Ignition (HCCI) process (actively pursued by auto manufacturers and many universities), which in many cases is controlled by the amount of EGR.
Laust
As mentioned increased back pressure also means increased exhaust gas recirculation (EGR), which lowers the combustion temperature, again resulting in reduced NOx and knock sensitivity.
Here is one of many references, this on to an SAE paper on the subject with the title “Knock Reduction of Spark-Ignition Engines By Egr”: https://shop.sae.org/technical/papers/860034
Taken to the extreme you can also look up the Homogeneous Charge Compression Ignition (HCCI) process (actively pursued by auto manufacturers and many universities), which in many cases is controlled by the amount of EGR.
Laust
