a couple of months ago, i put a set of slp 1 3/4" headers, dual 2 1/2" cats, 3" catback and a flowmaster 40 series muffler on my near-stock l03 firebird.

the car runs great since i did the install with two exceptions.

1. idle. when i first start the car, it now idles at 1,500 rpm. i always let the car warm up for at least 2 minutes before i drive it. by that time, the idle has usually slowly fallen off to about 1,000 rpm. the car drives fine and will eventually settle down to idling at 6-700 rpm, just as it did before i did the exhaust. also, even when it's fully warmed up after hours of being driven, it's often slow to drop back to idle. it wasn't like that before.

2. mileage. before the exhaust change, i got 14-16 mpg in town and 26 or so on the highway. now, i get 28-29 mpg on the highway, but in town i'm lucky to get 12. it's not just lead foot fever, either. i drove an entire tankful short shifting to the extreme, seldom revving over 2,000 rpm in any gear and only got 13 mpg.

i think i may know the answer to this one. i'm still running the stock oxygen sensor. i've read about people who'd had problems after exhaust mods with the o2 sensor never getting to operating temp. my car runs great, so i didn't think it was a problem, but now i wonder.

i live less than 2 miles from work and normally go to lunch near where i work. i'm wondering if the o2 sensor never gets hot enough on those short drives to go into closed loop, but does on long highway drives.

i'm thinking about using the 02 sensor kit they sell at ccs motorsports. it's at the bottom of the page:

http://www.ccsmotorsport.com/products.htm#heatedo2kit

anyone have any thoughts?

 

With shorties I don't think you would have a problem with the stock o2 sensor. If they are coated it will help keep the heat in even better and I would think you would be fine.

 

they are coated, but, if i remember correctly, that makes it worse, as the heat passes through instead of staying in the headers.

 

I dunno. To me it keeps the heat inside where you want it instead of escaping into the engine bay. Maybe my thinking is way off, but it would seem to me the coating would actually help heat the 02 up better. Regardless, as long as you have shorties where the 02 is in generally the same place as stock you SHOULDN'T have problems.