Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: bluffcitybenz on October 02, 2009, 15:24:11
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Good day all! I feel I am beating a dead horse here, but I am still in the tuning phase of my 230sl engine rebuild. I have taken this vehicle through the emission test twice and failed both time. The first test failed on hydrocarbons, the second failed on hydrocarbons and carbon monoxide. The second trip did yeild 43% less hydrocarbons(2400ppm((spec is 900)), but now CO is out of spec @ 9.69%(CO spec 8.9%). When HC was at 4223ppm, CO was 8.54%. Correct me if I am wrong here, but isn't CO and HC directly proportional to each other? The spark plugs appear to be in the "normal" burn heat range when compared to a spark plug chart. The HC reading would indicate I am still rich, but what is MB's stance on HC ppm(CO is 3.5-4.5% right?)? Anyone else out there have any nominal results?
(http://i791.photobucket.com/albums/yy197/daehdaed/DSC05781.jpg)
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Sorry I can't help you with the percentages, but I noticed that your ceramic insulators are an orangy-red color. Mine are the same color and I use an octane boost additive. Do you use octane boost as well?
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In The Netherlands, the CO emissions test does not apply to old cars like ours. Not everyone knows that, and although a long shot, you may want to verify whether there's a similar exemption for your car.
If I am correct (books + car are a few miles away from me + PC) I tune my car to between 3.5% and 4% CO level. The CO level on your car does seem very high. I believe I am able to get mine down to around 2% (which is the limit for newer cars in The Netherlands) but she does not run so well then. I'm not familiar with the hydrocarbons aspect of your question, sorry!
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In the sixties, cars were emission certified in an earlier version of a dyno driving test. The 280SL was certified with EPA in 1971 with the following results:
HC 1.8 grams/mile
CO 19 grams/mile
NOx 2 grams/mile
CO2 556 grams/mile
combined Fuel Economy 15 mpg
sorry, no ppm values
Proper adjustment of the injection pump and linkage is essential and described in detail by Joe Alexander in our Technical Manual.
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The red colour on spark plugs is often caused by a fuel additive that has manganesse in it. Unleaded fuel will usually leave the threaded portion darker to almost black in appearance - I consider this to be normal. The electrode tip of your spark plugs seem to have a normal colour so it doesn't appear to be ignition related.
If you removed the plugs right after shut down from a longer drive this is how they should look if all things are working right. If you let the car idle for a while I would think they would quickly darken to almost black.
3 - 4 % at idle is normal for these engines but they tend to go quite lean at road speed - it's the way they run. Since almost all of your miles are done at road speed the idle mixture seems to have less importance but it can load up the plugs causing missfire so it's a good idea to adddress this.
I would look at the CSV. Extra fuel is coming from somewhere. If you've checked everything and it's stil rich then the pump needs to be calibrated.
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Just found an old article in a German car magazine, comparing a 230SL about 10 years ago with and without an oxydation catalyst, which at that time was available from the Classic Center for retrofitting.
For HC, the car with the catalyst is listed as 50 ppm, the stock car without the catalyst as 700 ppm.