Hello, I have a kooks H-pipe with a straight pipe to the back. All piping is 3”. I do have the stock headers on the car still. However, whenever i let off the gas, in low RPMs it won’t compression brake, it’ll kinda chug and not properly engine brake. When I’m in higher RPMS it will take a second, vibrate and then it will start to properly engine brake. Is this a back pressure issue? And help would be great!

 

Is this an automatic we're talking about?

These cars aren't diesel based engines so engine braking has less to do with engine backpressure and or compression and more to do with simple mechanical momentum/drag.

What I mean by that is No, backpressure has nothing to do with it. If your car is an automatic the delay is the car holding whatever gear its in when you first take your foot off the gas, then the vibration is the transmission engaging the lower gear which causes the mechanical drag from the drivetrain to slow the car down. Depending on what options package you have and your shift options, SPORT mode is usually the most aggressive for this meaning it will more readily down shift when coasting to prepare it self for quicker acceleration when you get back on the gas. Eco mode will be the worst of them because it will hold the gear as long as it can before downshifting in a effort to save gas.