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Exhaust tip color

Discussion in 'Other Cars' started by Mrpcar, Feb 24, 2013.

  1. Mrpcar

    Mrpcar Active Member

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    Want to start another discussion topic. "Exhaust tip color"

    The exhaust tip can tell a lot of things about how well the engine is working. Too much carbon = running a little rich. No carbon build up = too lean, or just running really clean.

    Well, here are some exhaust tip pictures. To my surprise the Ferrari is actually running pretty clean. At 15,000 miles when I took my exhaust manifold off I couldn't see any carbon deposit on the back of the valve at all.

    Can you identify which is which? To my surprised the Ferrari tip looks cleaner than the Prius...

    [​IMG]
     
    #1 Mrpcar, Feb 24, 2013
  2. David Beale

    David Beale Senior Member

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    You can't use this method when you have a cat. converter. It totally changes the results. All you're reading is how fast the cat warms up and how well it's working.
    The Ferrari has a cleaner tip because the engine runs much hotter than the Prius engine. This results in the cat working much better. If the Ferrari has a cat.
     
    #2 David Beale, Feb 25, 2013
  3. Mrpcar

    Mrpcar Active Member

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    It does have a CAT, actually have 2 of them. A pre-cat help to decrease cold start unborn fuel, and a main cat.

    But I think exhaust tip color does show how rich /lean a motor is running despite of a cat.

    Recently couple of the injectors in the X5 went bad and started to leak (direct injection injector issues), and I noticed a lot more carbon build up around the exhaust tip area. That's how I was able to identify I had a leaky injector in addition to weird engine starting behavior.

    Here is a discussion thread on that subject. In the middle of the page there are some pictures.

    2013 X5 5.0 M Performance Package. Runnig Rich 7.8 MPG! + Tranny Issues. - Bimmerfest - BMW Forums
     
    #3 Mrpcar, Feb 25, 2013
  4. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    The Ferrari probably doesn't have very many miles on it either... :)

    At first when I looked at the title of the thread, I was thinking..."Colored exhaust tips? :eek: Holy Crap!! What are those kids going to bolt onto their cars next???"

    Humble apologies to the OP... ;)
     
    #4 ETC(SS), Feb 25, 2013
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  5. Joe-G

    Joe-G Member

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    Actually in a modern car with OBDii functioning properly, the tips just tell you how hard you've been driving the car.

    A properly functioning OBDii system will maintain 14.7 or close to it during closed loop operation, and if you never floor the car, it'll always run closed loop (after warmup) and thus 14.7, and the tips will be pretty clean, perhaps a slight dark gray coating.

    Each time you floor the car it goes into open loop which in an N/A car is typically tuned by the factory at around 11.5:1, quite rich, as the additional fuel protects the engine from detonation and cools the combustion chamber. And it makes the tips sooty black in the process.

    When I ran my Vette in the timed mile on a runway up to 185 mph the tips were so black I had to use my wife's scrubby pad. To be specific I had to buy her a new pad. Lol I now use anti-bluing cotton wadding for motorcycles, it does a great job keeping the tips clean.

    I offer this information based on 6 years of tuning my Corvette with HP Tuners and a wideband and observing the normally polished stainless exhaust tips during different types of driving.

    Back when I was racing my 72 Hurst/Olds we would read the plugs to see what jets to put in the double pumper I had on the car or the needles to put in the Quadrajet when I had that setup. On those cars the tip color did mean something and it was often light gray from a lean cruise or sooty black from rich cruise. Nowadays I read the open loop air fuel ratio (and many other parameters) on my laptop during runs and make adjustments in the pits.

    Same concepts in tuning the car as the old days but my fingernails stay a lot cleaner.;)
     
    #5 Joe-G, Feb 25, 2013
  6. Mrpcar

    Mrpcar Active Member

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    It's not the OBD2 that tunes the fuel mixture, it's the on board DME (Digital Motor Electronics), ECU or Motronic whatever you want to call it. OBD2 is mainly for emission related devices only required on cars made starting in 1996. OBD2 system does not alter or change any performance or fuel mix of the car.

    A car only goes to open loop if there is a faulty sensor or if there is something wrong with the engine. It goes back to factory default data map to keep the engine running. Sort of a limp home mode. A health normal car should run in close loop. The base data value is changed according the way you drive and from sensor inputs. When you disconnect the battery everything is erased and car goes back to original factory data map, but will relearn again.

    Some car manufacturers can use their diagnostic computer to reset certain data maps points specifically for transmission or engine management all separately.

    I've never heard of any car running in open loop when you don't floor it... Must be a GM thing.
     
    #6 Mrpcar, Feb 25, 2013
  7. Joe-G

    Joe-G Member

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    I believe I said a car runs open loop when floored.

    In my Vette you can control when the car goes into open loop if you tune it, but with the factory tune basically WOT is open loop and it relies on pre-programmed maps and the MAF sensor to control fueling.

    I appreciate your clarification, OBDii doesn't control the engine, the computer does, but cars with OBDii all have feedback loop computer systems to control fueling and thus emissions.

    I also agree with you that cats don't control the color of exhaust tips, I've factory dual cats and now aftermarket high flow cats with headers and both exhibit the same exhaust tips...clean if I don't get on the car and go open loop, and sooty black if I do.
     
    #7 Joe-G, Feb 25, 2013
  8. Mrpcar

    Mrpcar Active Member

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    I am pretty sure OBD2 is strictly for emission monitoring purpose, does not give any feed back to control fuel.

    Although you can hook up a reader and get bunch of interesting engine running data but the data is not used to change any fuel map. It is strictly for reporting and help diagnose troubled area. The ECU is the only device in the car that controls and changes fuel mixture. (Unless you've made modification to your ECU like adding on a piggy back system etc.)

    Just to confirm, I googled it.

    On-board diagnostics - Wikipedia, the free encyclopedia
     
    #8 Mrpcar, Feb 26, 2013
  9. CTpriusV

    CTpriusV Junior Member

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    I'm not sure of your wording but I do tune my Vette through the obd2 port, I can change things like Idle, fuel ratio timing red line in the ecu, reset H-codes??????? I've been doing this since the mid 90's with my SS Camaro
     
    #9 CTpriusV, Mar 7, 2013
  10. Mrpcar

    Mrpcar Active Member

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    That's because you are using the obd2 port the flash the ECU to make those changes. Not sending information through the port to make direct adjustment. :)
     
    #10 Mrpcar, Mar 7, 2013
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