OK, here is a question for you all.

I always have very sooty tailpipes, especially on the bottom of the oval, when driving too and from work, and around town, even on longish trips (250 miles - but limited to about 65 mph max)

I just got back from a weeks vacation at a place called Fripp Island in South Carolina, between Charleston and Hilton Head. Great place by the way.

The trip was about 650 miles one way, mostly on I-95 with speeds around 75-85. No black tailpipes on this trip. What gives?

By the way, the car was a dream, even though I drove it only one way (We drove two vehicles over two different routes).

This is by far the most comfortable car I have ever owned, especially for long distance trips. I even got a 28-29 mpg over certain legs. The ACC was great, set it on 85 and flow with the traffic, though I had to cut the distance interval to 1.5 seconds from 2, or people would keep cutting in.

The CMBS did activate once. There was a downhill left onramp from one freeway, and we were in the number 1 left lane. A car came racing down the onramp from behind us, which would have been like the number 0 lane, cut across us diagonally through four lanes while we were doing about 75. Visual and audible warning cues went off, seat belt tensioning and I don't know if the brakes was CMBS or me, then the seat belts tugged again to loosen up. It was over before we knew it, and my wife thoroughly impressed and shaken up.

 

I've had my 07 CMBS RL since late April but haven't seen it react like that. I've even tried to simulate it, but the most I have ever gotten was the BRAKE light and beep. Even that didn't come until very late when I was within 2-3 seconds of impact. I'm thinking there might be something that needs adjusting on this car but my dealer said there isn't anything to adjust. He checked the "codes" and ran a self diagnostic and everything checked out.

I just took my first road trip this weekend too. Not as long as yours but it was my first time on an extended trip. Took it about 90 miles to Vero beach from Orlando. I agree, its a great cruising car as well as a city car. A pleasure to drive all around.

 

I'm going to guess the following...

The "soot" (carbon) you normally see at the bottom of the tailpipes is more common when you use as a daily driver over several days because of the natural condensation that develops in the car's exhaust system when the car cools after driving, especially overnight. (Have you ever noticed water dripping out of the tailpipes when you start your car in the morning to go to work?) This condensation comes out of the tail pipe and, gravity being what it is...the water drips down and any carbon deposits it happened to pick up are deposited on the pipes on the way out. Day after day, this process repeats itself, leaving your sooty deposits.

Contrast doing 250 miles a week over five days to one solid trip and only one cooling/condensation cycle. There be your answer...

 

I do 95% city driving. No soot on my tailpipes.

Regardless of city or highway driving, you shouldn't have soot on your tailpipes in any great degree. That's usually a sign the fuel mixture may be too rich (among other more serious things). It could just be a computer problem. How's your gas mileage? That could be an indicator of whether your computer is not pulling back on the fuel mixture after the engine warms up. I'm no master mechanic and others can probably add more.

At very least, why don't you try changing fuel brand for a week and see what happens. I don't think that will matter but I'd be curious and try it if that was me.

 

I have an 05 RL and I had the same problem after a year. I actually read somewhere that it was the way that they were designed and the 07's didnt do it. I took the car to the dealer and told them about it and they replaced them with the 07's and now they are doing the same thing.

I would say that is the hardest thing to keep clean on the car. I never thought of it being the fuel mixture. I have used several different stations and the same result. Looks like I need to have them take another look.

 

I would have to agree with bmerton. All cars emit carbon (soot) and most I have owned will have soot build up on the exhaust if not kept clean.

I suspect it is the design / angle of the tailpipes that allows the soot to build up in the exhaust pipes and then drain out with exhaust vapor. Perhaps if there was a different angle, the carbon would not coat the tailpipes so easily?

That said, I use a pipe cleaner brush in my tailpipes when I wash the car. It does clean out the soot beyond just the exhaust tips. As a result I have very little soot on my exhaust tips in between washes. That is what makes me think water vapor is carrying soot build up from deeper in the exhaust system.

Of course there are many other factors, not limited to local & regional fuel grade mixtures / fuel additives, temperature & humidity, and even how much you stomp the throttle. Bottom line...it is a fossil fuel burner, and carbon is a byproduct.

This makes me wonder when hydrogen cell vehicles are on the road and water vapor is the byproduct, we will be buzzing about how the steam splatters our detail job?

 

I always think the CMBS sould activate long before it does but when I'm thinking that, I have plenty of time to react. The system is not a collision avoidance one, just collicion mitigation which would if necessary, lessen the severity of an impact. It will slow, but never stop the car. A few times my brakes have activated and the seat belts tightened. More than anything, it wakes you up quickly.

As for nothing to adjust, perhaps not but the system can be calibrated. When I first picked up my car, the CMBS malfunctioned. After repairing it, the dealer told me it needed to be recalibrated (with special equipment that they didn't have until they needed it for my car) and to do so requires something like 75 feet (could be less, I just don't remember the exact number) of clear level space. You may want to ask your dealer about recalibrating the unit (or just checking if it's correct).

LL

 

I think he was talking about excessive carbon buildup. Of course, you can't expect there to be a clean exhaust pipe after 4 weeks of driving. Chas2, if you think the carbon buildup is unreasonable bring it in for a emmissions test and find out how well the engine is burning fuel. Won't be hard to find out if there's a problem or your expectations are just too high.

Funny, I thought of that once too. I was imagining all the cars on the road emitting water droplets out the back. Are the roads going to be perpectually wet and slick all the time or is there going to be a constant mist rising off the streets.

 

Good idea, maybe the radar needs to be set somehow. Now that I think of it, the ACC doesn't seem to hold onto the car in front for the 300 feet as advertised. It's much shorter, not even 200 feet.

 

If the ACC is not performing as expected, I'd certainly get it looked at. Last time I used my cruise, it was spot on. I even (safely) put myself in situations where I knew it would react...just to be sure it was working. It was.

LL

 

The distance it measures/tracks is settable when you turn it on. On the longest setting on mine it does seem to be about 300 feet.

 

I thought that was for setting the distance YOUR car paces the car in front. There are three settings that are equivalent to around 1, 2, and 3 seconds based on the speed you are traveling.

What I was referring to is the statement I read somewhere that the radar gun can pickup and lock onto a car around 330 feet away. I can tell when it's locked onto an object because the car icon on the screen goes from an outline to a solid image. In my car I need to be about 100-150 feet before it triggers. It's this fact, coupled with my inability to get the CMBS to trigger, that leads me to believe my radar gun may not be working right.

I'm bringing the car over to the dealer tomorrow night to have them program two additional key fobs I bought on ebay. I'll ask my technician friend at that time if there is something "adjustable" on the CMBS system that makes it more or less sensitive.

 

I think there was a TSB about replacing the end caps in the exhaust so it wouldn't have soot on it.

 

Thanks for the answer. That makes sense...now on to our next topic, the CMBS

 

Read the extensive CMBS section in the manual, there are numerous instances where the CMBs will activate that are not imminent crash situations, in many of them you will have seatbelt retraction but not braking. Even in brisk driving if you shave the the front car's bumper too close the brake signal will activate. I have found the CMBS to work fantastically.

 

well I have black residue on my tail pipes every week, when I wash my car, but I don't know if this is what you are talking about. My car has ~2k miles on it. I wipe it off weekly. All of my acuras have done this.

regarinding the cmbs. I have noticed that when the braking is done by the car it is a different feeling.It feels almost like the brakes are being pumped electronically a whole bunch of times. I hope you have your laser cleaned..the brakes is the last step in the process, so it isn't necessarily going to brake if you respond first.

 

You are correct but you are describing full CMBS apllication (full ABS), remember, there are 3 levels,
1-brake light
2-brake light and seat belt tugs
3-full seatbelt retraction plus full ABS.

 

This is exactly what I am talking about. I washed the car before the trip, and this was the first time that I did not have to use 409 on the chrome portion of the tips to get off the soot, which regularly gets the bottom of the oval tips pure black.

I guess bmerton's explanation makes sense to me because each trip to S Carolina was over 500 miles. During the week at the beach, we never used the car, using our minivan and a 4 person golf cart or walking to get around the island. Then the blast back was a similar one day trip of about 600 + miles on a day where the thermometer was reading in the high 90s during the afternoon. After a week of commuting to work, I expect to have the black tips again. I suppose that the different gas may be telling, as we happened to fill up at Exxon stations throughout the trip, and I usually use Sunoco. My trips this week will exhaust the Exxon tank.

 

I predict the different gas station won't make a difference. As TampaRL so eloquently stated, carbon is simply a byproduct of the process. Vehicles are not designed to be able to burn every bit of fuel completely efficiently. There are reasons for catalytic converters being on a car.

Cars are *designed* to run rich under certain conditions (foot to the floor) and lean under others (coasting) and stoichiometric under still others (cruising). You should *not* get a completely efficient burn at all times, no matter WHAT brand of gasoline you are using.

 

I just did a gas tank full of city driving and checked my tips. There was a small amount of carbon deposit on the very edge of the bottom 1/2 inch of the rolled edge. It was not black, it brushed off with my finger, and didn't really leave any mess. Wouldnt even have noticed it unless I went right up to the pipe. Not sure how that compares to you, but I certainly don't have solid black soot on my exhaust and don't need to use any cleaner.

If you really think you have excessive carbon buildup on your exhaust I'd still recommend bringing it in to have the engine exhaust tested. Could be a fuel mixture problem with the injectors (as previously mentioned). If your not having any other symptoms (e.g. visible blue smoke when starting, misfires, white smoke) then it can't be anything serious.

 

Sorry, I misunderstood what you were asking. You are right! Something is amiss on your system I believe because on a straight level road mine definitely fills in the car outline and starts tracking a vehicle that is straight in my path at more than 300 feet.

 

OK, I will definitely force teh issue next time. It's one of those problems that can easily be observed. I hope there is some test equipment they can use to "calibrate" this thing. It obviously works, just not properly.