Cat Delete. What do I need to adjust?

[mfiazzo]

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!!!!!

[proporsche]

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

Ivan

[pampadori]

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.

[mfiazzo]

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

[RarlyL8]

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.

[eastbay]

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.

[PFNog]

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

[ToySnakePMC]

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.

[RarlyL8]

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

[rnln]

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

[john walker's workshop]

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.

[Pigeye]

Adjusting idle mix in SOP when deleting the CAT??

[RSBob]

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.

[mfiazzo]

Thank you all for your input.

[Dr J]

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

[pmax]

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

Not fun IMO in a targa...

[Qcurtis88]

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

[911mhutch]

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

[PeteKz]

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

[Schulisco]

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