hhr_2009

I'm thinking of adding a 2.5 inch ZZP DP with no cat attached to a stock GM performance Catback.
I had a tune done a couple of years ago when I added the header and GM Catback, will I need a second Tune because of the DP.
Also, will it be louder with no Cat.

Thanks guys

843de

With the lowered back pressure from running without a cat into a low restriction exhaust, you may need to have it retuned. It all depends on how the current tune will respond to the loss of back pressure.

Will it be louder, probably not much.

hhr_2009

I was thinking of the same, it might be best to leave everything as is and not get a DP

prod

Or get a downpipe with a cat. I got the zzp longtube header and catted 2.5" downpipe, no codes at all, not tuned yet.

skyline26

your CEL didnt come on?

prod

Me? No. But I would guess no cat would.

skyline26

im shocked that your DP didnt set off your CEL..it does to everyone lol
set mine off too this past weekend when i changed it
i ordered an o2 defouler to see if that will help..and im burning thru so much more gas now with the bigger tires, DP and cat back geez lol

hhr_2009

Just wondering if I would need a second tune if I get a 2.5 DP installed concidering that I already have the header and GM performance catback.
Also, will it be louder then it is now, will it burn more gas, and will I get the extra 15 HP that ZZP says I will.

BNRacing

You don't need a tune for it other than turning off the CEL if it pops on. If you have a Trifecta tune you can turn off the CEL yourself in EZFlash

skyline26

your going to burn rich with that pipe...thats whats happening to me now and im burning thru gas like water