[Kim]

I have a lot of soot buildup on the back of my car, especially directly around the tailpipe, even after driving only a little bit (say 100-200 km). I have to use pre-wax cleaner almost every night to get it off - it looks like a combination of black soot (which comes right off) and yellowish varnish (which needs the other stuff to come off). I know that I have a crack in the back of the muffler where the tailpipe comes out, and Pete is going to replace it, but is this something that others get? My fuel mileage has remained totally unchanged since I did all of this - airbox, Stage 2, engine back complete exhaust with lo-flo cat. So if the car is running rich it isn't just sucking gas through with reckless abandon. I also tend to smell exhaust in the car, especially when stopped at a light, but that might be due to the break in the muffler under the car. I have a wire/oil air filter (k&N) and I am going to check it to see if it is in need of cleaning next time get the car (Thursday).

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[stevekat]

What is your fuel mileage? is this your Tip or your six speed?

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[flash]

not me, and i run an extra 2lbs or so of fuel pressure

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[Kim]

6 speed coupe. My monthly fuel consumption, based on driving anywhere from 600 to 10,000 km per month, has consistently been at about 32 mpg Imperial or about 26.5 mpg US. This has remained unchanged since 2004.

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[94SilverCab]

I also note a significant amount of "soot" around the tailpipe. Maybe I just have a tendancy to push the right pedal more than I used to?

I was concerned to hear that you can smell exhaust, that sounds like an installation issue and not related to the system.

Regards,

Jay

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[ds968]

no soot whatsoever here. ( airbox mod, KN filter, chip, BB catback exhaust )

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[flash]

the yellowish varnish is the nature of stainless - i have to polish that regularly too

the soot is carbon - that can be caused by a number of things, including but not limited to: low compression, rich mixture, tired O2 sensor, clogged air cleaner, cold weather, ineffective cat, leaky exhaust system (though generally would have to be up front)

if you are smelling exhaust, i would get under there and find out where the leak is and fix it

which car is this? how many miles on it? how old is the O2 sensor?

i should add that many people still follow the old school philosophy of letting their car idle for a while in the morning before taking off - this is when the car runs the richest, and when this soot is the heaviest

many drivers still blip the throttle before starting too - this can cause fuel dump too

both of these are also unnecessary in today's computer controlled cars - in fact, most owner's manuals tell you NOT to warm it up. or to touch the throttle on startup - our manual says on page 25 not to do either of these

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[Kim]

1. no blipping
2. no warmup idle
3. varnish is on the rear valence, not the tailpipe. It is exactly where the soot is also. It just comes off harder
4. inside of tailpipe is VERY sooty
5. car is coupe, 300,000+ km
6. O2 sensor about 140,000 old (4 years)
7. checking air cleaner tonight

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[flash]

holy cow! - likely just age then

that O2 sensor is about 26000 miles(40000 kilometers overdue ) - interval is about 60000 miles

if that engine has not been gone through, i'm willing to bet your compression and leakdown numbers aren't all that swell - a tired engine will do that for sure

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[RS Barn]

We see 1--15 968's a month.
Stock exhausts are very sooty inside tailpipe. they extend farther rearward than our tips and let soot escape.
They also don't have tapered bore which delivers a better sound and power.
RS Barn chips don't change A/F until full throttle load and that doesn't make extra carbon out exhaust.
944 Turbos don't emit much carbon until you open up exhaust and then they soot like crazy until hot
Just part of the performance world.
Pete

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[Kim]

Head was done about 15,000 km ago. Valve seals replaced. Rings were not touched. I was told that compression was good then. O2 sensor has 120,000 km on it now. I will get a new one. I guess I presumed that it would need to be replaced when the RS Barn cat was installed as part of the head gasket project but the records for that repair do not show it. I guess the old one came out properly and was reused. Every seal on the engine has also been replaced since then, some more than once.

Car also seems to be using a lot of oil lately, and just since the O-ring for the dipstick tube was replaced. It doesn't seem to be in there right as I have to really shove the stick in hard and pull it out hard. I am afraid that I will pull the handle out of the dipstick itself. But there are no oil leaks now and I don't see any blue smoke or smell anything like burnt oil. The oil is going somewhere. But I am am going through a litre of oil about every 2000 km.

I will have the entire exhaust system looked at tomorrow when I get an oil change.

The replacement RS barn muffler should arrive in a few days and that will at least rule out the cracked section under the car.

Also, just as an aside, I got new rear tires last week and was advised that about half of the wheel nut were in so poor condition that you could pull them apart with your fingernails. I could not believe it until I saw it for myself. I have ordered 20 new ones. Be aware.

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[flash]

yeah - those lug aluminum nuts suck - they are only good for about 25 on and offs before they start to lose the ability to hold torque - that's why most tires shops won't torque them past 85lbs - not sure why i have been hanging onto mine - one of these days i'll off them

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