Thread: Exhaust cutout causing KR and misfiring

So I have a 07 GP turbo. I just installed an exhaust cutout and went for a drive with it open. When I get into the throttle, just like half throttle, I get a ridicules amount of KR and get misfires on pretty much all cylinders. On the last run I even tried I was at 56% throttle and I got a spike of 14.9 KR. Of course it was followed by lots of misfires, I would assume cuz I went to 0 degrees timing, sounded like I had an anti lag switch. Anyone have any idea what it could be? Oh and I do have hpt to tune with.

Yes it's normal with it shut. No KR and no misfires

On the lower down pipe just before where the cat back exhaust connects.

It's a catless downpipe so it's where the cat would be

Anybody have any idea what it could be or what I can do? I know I can just leave it closed but I want to be able to run it at the track in the spring

you can still make full boost on half throttle... And when the cutout is open you will make more boost faster.

What is your AFR before it starts missing? Commanded and actual please.

I was making full boost a lot quicker, I could really feel the difference even at half throttle. Commanded for closed loop is 14.7 and for open loop it stays between 11.7 and 12.1. When i drove it with the cutout open my AFR was all over the place and really lean. When I did get into the throttle I just noticed my injector duty was at 110% where on all my previous scans it would be around 70 and 80 at the same throttle and gear. My LTFT's and STFT's were also jumping around really bad which it never does. just before I started seeing KR my AFR was at 13.2 and i was at 56% throttle. I'm still kinda new to tuning thats why I want to get opintions before I start doing anything but I was hoping to get things worked out this weekend. I just don't understand how the cutout is effecting everything so much.

Well I could feel it was a lot quicker before I saw KR. I'm wondering if the cutout is coming in contact with something maybe the swaybar and creating false knock because its not steady knock. It will go from nothing and spike up to crazy KR. So I'm going to crawl under the car and see today

Originally Posted by Bio248

this entire post is exactly what's happening.

I understand that. I just don't get why everything changed so much just by using the cutout.

So should I just redo my tune with the cutout open and have two tunes? One for open and one for closed

Ok that's what I figured. Just wanted some opinions about it

My O2 sensor is in the upper downpipe coming off the turbo. It's a Z3 downpipe