Emissions removal benefits on early SC?

[smross]

Can anyone tell me the actual horsepower improvement derived from the removal of the 2-way catalytic converter and air pump on an early SC?

TIA

Regards,

Steve Ross

[Porschephanatic]

I can't give any dyno #'s, but I could sure feel a difference just installing SSI's and a stainless Dansk dual in-dual out muffler. Worth every penny, IMHO, though a little too loud for my wife.

[SpeedracerIndy]

I believe you are talking about removing the Cat and putting a Euro premuffler in its place though. Much cheeper than SSIs. I have heard that the euro premuffler with a decent muffler will give close to the performance of the SSIs at a fraction of the price. I have a bursch muffler and an aftermarket CAT in place now from the federalization of my car. I am going to replace the cat with a euro premuffler for around $250. That should tide me over for a while until I can fork over the dough for SSIs.

[Mike Kast]

I was told it's about 20 horses. about 10% ...
180 horse out of the box, straight piped is about 200

[smross]

Yeah, I'm referring to the theoretical removal of the stock cat. and installing a "test pipe" in it's place.

Also, horspower improvement by removing the air pump?

[Jadams1]

Air pump is minimal (seat of the pants scale). I removed mine for cosmetic reasons.

[nostatic]

I've been told the air pump eats a hp or two due to belt resistance. Nothing you would notice. Removing it does open up the engine compartment somewhat though.

[juanbenae]

the test pipe makes for a bit better sound w/ stock muffler but no real "seat of pant" improvement. i like it because it gets the cat out of the way for valve adjustments, the sound is better without being too loud, seems to run a bit cooler on hot days, and most imoportant, the man aint keepin me down with it.

[Marankie]

I have installed a European Premuffler and added another outlet to the stock muffler on my '81 CS Targa. The noticable difference is above 5000 RPM. Now under full throttle it revs easily form 5000 to 6000 RPM, whereas before it took a little time. About a 10mph measured increase in top speed. On the down side, when pulling up to a stop light, there is a short time when you can smell the exhaust from the period of over-run on the engine. However after a few seconds of idle, it smells clean again. I have modified the premuffler to include the oxygen sensor.
By the way the car is for sale. Goreous metalic blue with cork leather interior.

[Andras]

Steve,

You can always just disconnect your air pump temporaily, and see for yourself if it makes a difference.

If performance SEEMS improved, and you hate to have all that plumbing in the engine compartment, then by all means remove it.

If performance SEEMS un-improved, then ditto.

Most people have removed theirs because an air pump is old technology, it makes for a hotter running car, and it blocks access to the rest of your engine (such as plugs, etc.).

Just do it!!!!! (an my car is NOT for sale!!).

Originally posted by smross
Can anyone tell me the actual horsepower improvement derived from the removal of the 2-way catalytic converter and air pump on an early SC?

Back to your original question - you may realize a couple hp, but nothing you could feel. Main improvement is access to engine.

[SpeedracerIndy]

Like others said, I would think the main improvment would be engine bay access. Maybe a little better throttle response from the decreased parasitic loss that the pump genorates. I think it is worth getting rid of to clean up the engine bay. See below:

[Mike Kast]

the 20 horse power from a test pipe is just a fantasy then?

[CarreraS2]

Originally posted by Mike Kast
the 20 horse power from a test pipe is just a fantasy then?

IMO, from what I've seen over the years, yes.

But that doesn't make it a bad thing. For a street car, owner perception is far more important than reality.

[techweenie]

20HP from a test pipe?

Only if your catalytic converter is mostly blocked.

I just did the swap on a '79 engine two weeks ago and the seat of my pants couldn't detect a significant difference.

[vash]

that smog pump is a PITA, i got careless and almost "sanded" through a wire on my multimeter. totally my fault. btw, it doesnt really slow me down so much with the spark plugs. but nevertheless, my AC and smog pump are living on borrowed time.

cliff

[Mike Kast]

Originally posted by SoCal911SC
IMO, from what I've seen over the years, yes.

But that doesn't make it a bad thing. For a street car, owner perception is far more important than reality.

That's funny! It was a Porsche mechanic who told me about the 20 horse. I went from a test pipe w/flowmaster back to a new aftermarket cat w/old stock muffler and I didn't notice a difference either. I just figured it was because I didn't know the car that well yet.
I have the exhaust off right now and I was contemplating putting the test pipe w/flowmaster back on. The duel exhaust looks a whole lot nicer but it is brutally loud, ear ringingly loud!
and the fumes give me a soar throat on a long drive, especially when I'm driving around town, sitting at lights, with the roof off. It gets the teenage boys all excited but that's not really the audience I'm after. Maybe I'll have to think about it some more.
Ok, I have thought about it some more and the cat is going back on

[SpeedracerIndy]

I have always heard that the test pipe will not give as much HP as the euro premuffler. Anyone else heard this too?

[Porschephanatic]

Originally posted by Mike Kast
the 20 horse power from a test pipe is just a fantasy then?


Yes, it is, IMHO. I tried that first, and felt no seat-of-pants improvement, AND I had a partially plugged cat! Gave the test pipe to my wrench, Au Gratis, and bought the SSI/Dansk for a (I'm guessing 20 HP ) improvement I could feel!! I've swapped exhaust systems on well over half of all the vehicles I've ever owned, and never noticed such an improvement through exhaust modification alone.