Who is running a test pipe in place of a cat?

Yes. It does have more of a gas smell. It is especially noticeable, and acrid, when using ethanol laced fuel.

Actually my Wife complains about it more than I do. Smells like the 60's to me.
Alden

 

The cats were hollowed in the t I purchased. It really smelled like exhaust fumes and I did not like it. Also, could not pass emmissions like that. The cats were re packed and the smell is gone.

 

My 1965 Corvair smells more like the 60s then it did in 1979 when I bought it. In fact, before that I had a 1965 Corvair that actually passed a late 1960s emissions test and did not smell at all. In the case of my current Corvair I work assiduously to keep the idle screws as lean as I can do without affecting the idle. Its not very bad in excess hydrocarbons. This is all very weird to me.

I suspect modern fuel formulations are in some way incompatible with older cars that do not have cats. I am rather sure my 1986 Mondial is running rich for two reasons. First, I accessed the fuel metering screw and gave it 1/8 turn more rich for cooler ignition. Second, the check engine light is on much of the time. However, the car never smells sulfurous [a typical rich mixture through a cat]. When I first took possession of the car it did have some sulfurous smell.

We do not have emissions checks up here in the North Georgia Mountains. If we did about half the entire fleet would likely be failed. Hardly a week goes by when I do not follow a hydrocarbon smell. Sometimes there is a sulfurous smell from cars climbing the mountain but this is almost always in the Fall. I suspect it is caused by formulation switch dates, but I don't know.

Back when I owned a 1984 Z-28 HO five speed I suborned the law by using a cold chisel to empty out the cat. I suspect someday I will die from the asbestos I removed. That car never smelled one way or the other. Further, I easily passed emission tests this way: I installed a home plumbing valve into the Positive Crankcase Ventilation hose and used it to introduce extra air for the test. It almost always passed. When it did not pass I would simply drive around the back of the station, twist the valve to let more air in, and then pass the test.

My Mondial is otherwise dead stock. My experience is it gets clogged up if not driven rigorously. Since I have owned it it has gotten WAY faster then when it was delivered. This is not a criticism of any previous owners. However, the car has a cam with peak torque at more then 5,000 rpm. I do not believe a single day goes by when I do not exceed that many times. I do, however, avoid 7,700 rpms. I scattered a clutch way back when. So I more or less pretend the red line is 6,000 rpm.

The car now has about 56,000 miles and runs like a Singer Sewing Machine.

 

I have no cats at all. My car smells exactly like an old Ferrari should.

 

I have a 1988 1/2 Mondial 3.2, and I put a test pipe in place of the cats. To me, it felt like a 30 HP increase. This is probably not logical, but that's my assessment. I'm guessing my cat was partly clogged, but the car has MUCH more throttle response, it is significantly faster, and it sounds fabulous. The entire mechanical bit took about 1 hour, and I like to poke around whenever I'm under the car. I say, DO IT!

 

My '84 Mondi doesn't have cats -- as others have said, you will get a lot more exhaust fumes. The smell will get on your clothes and your wife's hair. (I don't mind as I like the smell, but my wife complains.)

If the catalytic converter on your car is in good condition (not clogged), then why remove it? The Mondial isn't really a "performance" car anymore, so any performance gains you would see by removing the cats is kind of pointless. The exhaust may sound a little better, but if that's what you are after then I recommend going with an aftermarket exhaust system.

 

If you are looking for a power increase, why not consider "bigger" cats? I am guessing stock cats are something 400 cells per square inch. Going to 200 cell cats would make a big difference without all the fumes and negatives of no cats.

HJS makes some high end stuff, (Supersprint uses them on some of its setups with headers) and should be doable for under $1000. I am sure there are other companies that could also supply appropriate hardware.

Regards,
Jerry

 

warning to people who don't do engine work!!!

BEFORE you go pulling cats, DO consider the positive affects that they do have on the car.

in order for the engine to run properly as engineered (as little or much as they were) the engines DO require a level of back-pressure in the tailpipe. it affects how the exhaust valves operate, and can even affect the smooth operation of the pistons within the cylinders.

for a carefully tuned motor, this is VERY important to long-term health.
especially with how finicky CIS is, I am not a fan of long-term test piping.

get a high-flow cat if anything, it will provide a smell reduction, as well as a little better performance, but you should not go without cats at all.

chances could even be that you might be a tad clogged.

 

When I had my Mondial for sale we had someone from Ca. interested in it and they asked my shop to do a CO test on it to see if it would pass and there is a video of it on their website if anyone is interested. Its Restoration and Performance Motorcars go to videos and its the Mondial CO test.

 

Any well tuned car should easily pass emissions without cats. They are really designed to handle degradation of the tune. Most people will not keep up with maintenance so the Federal Government, in its infinite wisdom, has decreed we make sure those folks don't pollute.

I had an older car that had the cats gutted. Car easily passed emissions (numbers were almost identical to prior year with cats), ran a little cooler, better throttle response and slightly louder. No issue of fumes, probably due to keeping the cat housings intact.

The more modern cars are tuned much more on the edge, so I would agree that bigger cats are better than no cats. The Mondials can run fine without cats, but as noted by some, other issues appear. So the compromise would be more efficient cats.

Regards,
Jerry

 

If I can remember to add some patchouli oil to the fuel next time and get my Wife to wear a peasant shirt on our next drive, I will be in 60's heaven, lol!
Alden

 

Considering that most of us put only a few thousand miles a year on our cars, is this considered "long term?"

I could see if you were running a DD at 15K per year, but my Mondi at less than 3K?

Dunno, that is why I am asking.

My cat is gutted, BTW, not removed.
Alden

 

the only articles you will ever describe are people talking about the effects of too much backpressure bogging the engine, but I do believe, and was taught as a mechanic that a level of backpressure is figured into to how the engine runs.

if you figure a throttle plate as an intake restriction and an open large tailpipe non-cat as non-restrictor.. granted, the flow rates are vastly different due to combustion's affect on air density.
I think of this as causing too much excess vibration in the engine's operation, the backpressure can act as a buffer to smooth the running process. it basically (theory that air is fluid = hydrodynamics) hydraulically dampens the operation of the motor, helping the valves, pistons, and other components to do their job more smoothly.

as you say, 3k a year, not heavy usage.... I just hate that people are so gung-ho about gutting cats.

they do good work. they filter the smell, they reduce NOX emissions by a LOT, and they can help to moderate the tone of the car as a whole.

have I gutted a cat? yes. my saab is gutted. why? it was clogged and rattling. better no cat, than severe restriction.

as stated above, they may not help the co2 numbers, that may be correct, but it DOES change how NOX and CO are emitted, both awful, it transmutes it into nitrogen gas, water vapor, and co2.

if you remove the cat, you can slightly change co2 production, but increase a whole bunch of others. fun stuff. they wouldn't have put it on the car if there was no reason.

 

Not true in Cali the low emission level maximums require a cat, trust me my smog guy "tunes" my cars without cats , but to pass I gotta put the cats on.....this is for my DeLorean and F car

 

Actually F car owners are the worst as we dont run out cars enough to burn the crap that gets accumulated in the cat

 

There is more of an exhaust smell w/o the catalytic converter. But, again, the mileage is so low I/m not feeling any remorse. Ever been in a boat w/ an outboard motor? It's nowhere near that bad.
My car is an 88 1/2 because it was built in August of 1988. I'm told that was when the Mondial t production started and was AFTER the 3.2 production ended. Go figure! But really, Ferrari can't even say w/ certainty how many F40s were made, so what's a Mondial or two after the production "ceased"?

 

did you buy that black one with the questionable vin that was posted up a week or so ago? :lol:

 

No. This is an original federalized car I bought 14 years ago from Lake Forest Sports Cars on the north side of Chicago. I do wish to add that there are very nice folks at that dealership!

 

most people that work and sell classics typically are! it's a special kind of people.

 

I ran Factory test pipes for a while. Enjoyed the increased throttle response and sound but not the stink.
They are perfect for track day though.
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