A modern cat is about as restrictive as a glasspack muffler or just a bend in the tailpipe. It is not uncommon for someone to remove there muffler and keep there cat and find increased performance without too much noise.

Yes a smog pump has a parasitic drag I don't personaly recommend anyone keep there smog pump unless they have to for legal/emissions reasons. But the performance gain that can be found from removing the smog pump on many of our older vehicles isn't only from the loss of the drag. It is from the loss of all the vacuum leaks that so often accompany the smog pump and all the emisions equipment that goes along with them. In the early years detroit hadn't yet figured out how to make it work well and last. Today we have much better performance cats that stay clear, don't restrict flow and don't require air pumps to make them work. If placed at the proper distance down stream on a well tuned fuel injected engine.(with a carb you need a smog pump to make a cat work period)

Many of our trucks see a great benefit from removing all the surpurfulous vacuum/emissions equipment and adding a few degrees of timing. They run cleaner and get better mileage good things all around.

 

Like I stated before the smog pump uses LESS THAN ONE (1) HORSEPOWER to turn. There is no need to remove it.

 

And it only takes 50HP to cruise down the highway. So 2% of the power being used at cruise is turning the smog pump that you don't need. Why keep it.

 

Opossum, can you clarify some things for me? You want clean air but also recommend removal of the smog pump? Earlier this morning you said that not having the air injection (smog pump) would clog the catalytic converters, which would lead to removing them, which makes for dirtier air.

 

at what rpm? and how do you know this? i've SEEN a water pump take up 12hp at 8,000 rpms and i know this because we put an electric water pump on the car the same day and dyno'd it again.

and if you have a cat on an engine it reduces sound, to me this is saying there is a restriction......why don't drag cars run cats?.....why don't pro 5.0 cars run smog pumps?.........why do they make a smog pump elimination pully if it doesn't cost hp.....

 

I know I contradicted myself a a bit but that's because it is all true for the right situation. The safest thing to do is keep all the air pump stuff. But if the rest of the system is made to work well, you can get away without it. Modern cats can handle more heat so they can be placed closer to the motor. This keeps them fired up more and reduces the need for added air. Secondly a well tuned fuel injection system is very consistant for the cat further reducing the need for a smog pump.

Smog pumps were a patch technology created to meet smog requirements before Detroit hade figured out how to do so. In the beginning of catalytic converters they were not a honeycomb design as they are today, they were basicaly a can filled with BB's that were coated with a catalyst. These cats clogged easily and were very restrictive. Add to that the inconsistant exaust comming off a carborated engine in the years with smog reguirements and no fuel injection. It became nessasary to add a stream off fresh air to add oxygen to the cat, and to keep it working consistantly. Detroit for a few years was not comfortable eliminating the smog pump in there early fuel injection vehicles even with new style cats. (federal law reguires that the cat last 5 years or it's on the manufactures dime) As fuel injection was added to more and more vehicles and the emissions tech got better you see a progression from air tubes in the manifold, to air tubes that only feed the cat, and fanaliy to the elimination of the smog pump.

WOW I'm long winded, or would it be fingered.

All that said most of the vehicles I work on are upgraded. And I can't quite reconcile what they were thinking puting air in the manifold then using an oxygen sensor down stream. This seems destined to make the engine run artifically rich. I haven't had any problems with the engines runing lean after the air pump was removed. As would be expected if the computer was compinsating for the added oxy. Maybe they run rich new and always with the air pump I don't have that answer right now I'll have to look into that.

 

Cool man, 'preciate it. The upstream air injection seems to only work right after start up when the O2 sensor signal is ignored anyway, so that shouldn't cause any problems unless it's routing to the head when it's not supposed to.