Cat Delete. What do I need to adjust?
 

Hi All,

Car is a 78 911SC. All stock with exception of Danske Muffler. My Cat Converter has a small hole in it. I want to order a "test" pipe and delete the Cat Convertor. No emissions test since tags are classic car.

What would I need to adjust if anything on the CIS if I make the change?

Thank you in advance!!!!!

you do not have to do anything, just enjoy more horsies, about 5 i would imagine;-) and better sound

Ivan

offset your carbon footprint by using less plastics. Forego the straw or the drink lid. Bring your own reusable shopping bags to the grocery store.

But I don't think your CIS is going to care too much.

Perfect, thank you for the feedback. Much appreciated!!!!

Be mindful of the final sound level that you are after. The bypass pipe is just that and can be a little loud if combined with a sport muffler. If so then a premuffler is a better option. Not all are created equally so take a look at the design and materials before you pull the trigger.

Make sure the bypass has an oxygen sensor hole, then you can run a wide band gauge. Best thing you can ever do for a CIS car. I like the AEM X-Series 30-0300 Wide Band, but that's just me.

Yep, check out the M&K pre-muffler instead of just a straight bypass pipe. Better sound, very nice quality materials and construction too.

New member to the 911 air-cooled world, but my first modification to this ‘76 coupe with 3.0 conversion was to drop the old restrictive exhaust and replace it with the Dansk st/st cat delete pipe and matching sport muffler. It has a healthy sound to it - no complaints - and the wifey even approved in her first ride in the car the other evening! Oh, and their matching hardware & gasket kits were excellent fit.

https://i1193.photobucket.com/albums...549681BD3.jpeg

https://i1193.photobucket.com/albums...FD380E043.jpeg

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Could'a shed 20 pounds off that with an M&K, just sayin' ...

guys,
I thought he would need to adjust air mixture?

May need to adjust the idle mix a bit richer now that the cat is gone. Who knows what it was set at previously. At least have it checked.

Adjusting idle mix in SOP when deleting the CAT??

I would recommend taking shallower breaths.

I was shocked at the increase in exhaust after I deleted my cat. Since it doesn’t get driven much I can rationalize not putting it back.

Thank you all for your input.

May get some popping and gurgling on hard decel (sudden closing of throttle when previously at high rpms) which many of us actually enjoy.

You'll get more CO/NO/HC wafting into the cabin and more exhaust sound.

Not fun IMO in a targa...

I just got a test pipe for my 81 Targa. We'll see how it all goes this weekend!

M&K a nice, easy 20 lbs savings waaay in the rear...

If you still have the air injection pump and system, delete those while you have the exhaust apart.

I would check the mixture if it's remained the same as before removing the catalyst. Without the old cermaic catalyst the exhausts flow faster and this could cause a leaner mixture. Best is to use a wide band oxygen gauge to monitor the mixture while driving to see if there are any faults.

Thomas