I hate to post this... But... Cobb stage 2 question

[Spamby]

I'm of the understanding that some back pressure is a good thing, for the most part.

 

[Batmobile_Engage]

 

[Batmobile_Engage]

I know a couple guys that have a catless downpipe and remove the catback when they get to the track.

Though they often run a different tune for that...

 

[Spamby]

Thanks. Now I'm touching myself.

 

[Alin]

I know a couple guys that have a catless downpipe and remove the catback when they get to the track.

Though they often run a different tune for that...

How would that affect me and my car/tune if I were to remove my CBE?

 

[Batmobile_Engage]

You might not see too much difference because your downpipe is catted, but either way, removing part of the exhaust is likely to cause one of two (or both) problems. You will overboost at low to mid-rpms or in higher gears at WOT, you will hit peak boost (idk what your target is, but lets say 20 psi) and then the boost pressure will slowly increase past your target. Obviously both of those can affect your AFRs because your fueling isn't tuned for those boost levels......and we all know how important stable AFRs are.

 

[Alin]

You might not see too much difference because your downpipe is catted, but either way, removing part of the exhaust is likely to cause one of two (or both) problems. You will overboost at low to mid-rpms or in higher gears at WOT, you will hit peak boost (idk what your target is, but lets say 20 psi) and then the boost pressure will slowly increase past your target. Obviously both of those can affect your AFRs because your fueling isn't tuned for those boost levels......and we all know how important stable AFRs are.

It was only a hypothetical question. BTW, i have a catless downpipe. :tup: I have rock solid AFR's! :tup: :lol: With the straightpipe, we weren't making any progress, so I traded my straightpipe for a SPT CBE. My car feels unreal as it is right now. However, the car went through A LOT of torture when I went stage 2.... Solely because I didn't possess the knowledge I do now. :tdown: :doh:

 

[Batmobile_Engage]

I could have sworn you were catted. Oh well. I'm no expert by any means, but I try to be as accurate as I can and I as understand it, what I said about the backpressure and so forth is the best of my knowledge on the subject.
Basically, if you were to run an OTS map that was setup for a catted dp, the wastegate duty cycle would be set at (for example) 50% or so in 5th gear and you're really pounding it...now that duty cycle is set to provide you the proper boost pressure through the powerband in that gear...here you are running a catless dp all of a sudden and that 50% duty cycle just isn't cutting it anymore because of the reduced back pressure. Flow speed as well as turbine rpm is still climbing. A manual boost controller, acting in what is basically a feedback mode can control this, but even a protune would likely produce this result if you swapped in a catless dp on a catted tune.

 

[Alin]

Thank you for sharing that info! :tup:

 

[Batmobile_Engage]

If anyone finds this incorrect, please correct me for the benefit of us all.