Had to go to emissions testing today. Opacity was the only item tested. It was done on a dyno at 3000 rpm and opacity readings taken. Limit is 20, mine was 12. Is that real bad for a diesel?

The tech plugged a cable from the computer into the cigarette lighter. When asked what it does, he said it was to measure the RPM. ???

Anyone know how the RPM signal on a diesel can be measured at the cigarette lighter. I find it hard to belief.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

the rpms can be measured by the voltage.(very inaccurat)

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have no worries.....President Obama swears "If you like your gun, you can keep it

I had my Emmissions done last week. I was allowed 37% mine ran 10% at the highest. The guy before me had a 1999 F250 Dualy his was 8%. 12% is great. In colorado they test at 20, 40, and 60 mph on a dyno.

Can you explain how? I guess if it measures 0 rpm, that can be considered very naccurat.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

not sure how it all works i just know thats how autozones tester alt. tester works

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have no worries.....President Obama swears "If you like your gun, you can keep it

Did they check if the ALDA cover is intact? I would think turning it down might reduce opacity (i.e. pass)

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http://farm8.staticflickr.com/7271/7...144c3fc1dc.jpg

My ALDA is at max and I still passed with 6-8%.

12% is a little on the smoky side. Ideally you want to be at 5% or less. My E300 tested at 1.5% and my 240D at 6% if I remember correctly and that was before I started using the cetane booster and StarTron additive which seemed to help a lot. The limit here is 40% which would probably be the equivalent of smoke from a burning tire.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

funola,

How could the voltage in the cigarette lighter possibly tell the speed of the engine on a gasoline or Diesel engine. The voltage regulator is designed to keep the voltage constant regardless of the engine speed.

Voltage test, yes. Engine speed test, no.

P E H

They do an emission test in WA. Had a brain fart and can't recall if it was done on a dyno. They did plug into the cig lighter though. My '85's EGR was "not working" and ALDA was set to the max and it passed better than it did with all that crap working.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

They just started emmisions for diesel cars here in RI. Mine got a 4 for opacity with a 20 limit. test sheet said a 1 was the average#. I never considered my car as particularly non-smokey so I was pleased. The only thing they found wrong was a burnt out license bulb. Now I'm good for 2 years instead of our usual 1 year inspections.

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1981 240d
Newport,RI

"No way in hell the cig lighter was providing the tach signal during the emissions test but that's what the tech says. The LCD display did show a virtual tach and the rpm did change as the engine was reved. I even took some pics. The rpm displayed has to be coming either from the rear wheels via the dyno, or the exhaust pulses were measured. But then why did they plug into the cig lighter?


http://i31.photobucket.com/albums/c397/funola/Photo_020706_010.jpg

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

The SDL passed with flying colors and no egr. I hope she passes after I crank up the ALDA this year. If not I will just add some veg oil and get it re tested.

Diesel emissions seem to be a joke, as long as it runs half way decent it will pass.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

No matter how good the regulator is, at filtering to DC, there is still an AC component with any rectifier (alternator diodes). The plug in the cigarette lighter is for measuring the frequency of the AC. This AC is measurable with a digital multimeter. About the only way to nearly eliminate the AC component is with a "switching" power supply convertor ($$$).

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Sam

84 300SD 350K+ miles ( Blue Belle )

To expound on what SD Blue said, an automotive alternator is a (typically 3-phase) AC generator that has its output rectified to DC. They use diodes to do this, and each diode is essentially a half-wave rectifier. The output current is direct in that it stays on the same side of zero all the time, but it has sinusoidal changes in voltage that have a measurable frequency. This frequency is directly proportional to the rotating speed of the alternator which in turn is directly proportional to the crankshaft speed. The only issues with this method of measuring engine rpm are that you have to know the ratio of the crank pulley to the alternator pulley (E-test shop probably has a one-size-fits-most "approximate" value that they use for most vehicles), and the fact that electrical noise from other electrical system components can make the alternator output frequency hard to measure.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.