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diesels and o2 sensors
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Big Wizard Offline
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Post: #1
diesels and o2 sensors
I have a few questions reguarding diesels in general.
Do many newer diesels have o2 sensors?
Do any diesels have 5 wire wide band o2 sensors?
Do o2 sensor equiped diesels have a pre and post cat setup?
Do you know of any diesel models that need EFIEs?
05-04-2008 10:29 AM
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mike Offline
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RE: diesels and o2 sensors
I don't know the answers to all those questions. But I can tell you this: Diesels don't operate the same as gas engines in regard to air fuel ratio. Gas engines try to maintain a 14.7:1 AFR. Diesels on the other hand use changes in AFR to add/decrease horsepower. Diesel engine AFRs range from about 25:1 to 120:1, depending on demand (different engines may differ somewhat). So an EFIE is not needed to adjust the signal. When you press the accelerator, you add diesel to the AFR and the engine uses that to increase torque and speed. Sounds too simple doesn't it?

So if they are adding sensors to newer diesels, I'm not sure what they are used for. But I'll be very surprised if it changes the above basic operation.

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05-04-2008 10:40 AM
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Big Wizard Offline
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RE: diesels and o2 sensors
Yes they are very simple. I have an older freightliner and excavator that are so simple. Theres like 6 wires for the whole engine. But now diesels are becoming highly computer controlled and I dont have any local customers with one of thiese advanced systems. Theres now multi stage injection and other sensors. Im unsure how the computer controlls the process. I guess I allowed myself to fall behind the technology. As I catch up Ill share the education.
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Robert.
05-04-2008 11:37 AM
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rdgeorge2008 Offline
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RE: diesels and o2 sensors
Big Wizard Wrote:Yes they are very simple. I have an older freightliner and excavator that are so simple. Theres like 6 wires for the whole engine. But now diesels are becoming highly computer controlled and I dont have any local customers with one of thiese advanced systems. Theres now multi stage injection and other sensors. Im unsure how the computer controlls the process. I guess I allowed myself to fall behind the technology. As I catch up Ill share the education.
Thanks
Robert.
ive just finished up with a f350 power stroke working fine no efiee needed no sensor just a pwm with my cells always use a bubbler
05-04-2008 01:07 PM
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mike Offline
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RE: diesels and o2 sensors
Big Wizard Wrote:Yes they are very simple. I have an older freightliner and excavator that are so simple. Theres like 6 wires for the whole engine. But now diesels are becoming highly computer controlled and I dont have any local customers with one of thiese advanced systems. Theres now multi stage injection and other sensors. Im unsure how the computer controlls the process. I guess I allowed myself to fall behind the technology. As I catch up Ill share the education.
Thanks
Robert.

Yes, please let me know what you find out about the fancy schmancy stuff they're adding to the simple diesel engine. I strongly suspect though that it won't change the equation on adding HHO. The basic design of a diesel engine was pretty good, wasn't it? It's very difficult to screw it up. But it looks like they're trying.

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05-04-2008 09:55 PM
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retmil46 Offline
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RE: diesels and o2 sensors
As Chief Engineer Montgomery Scott once said, "the more complicated you make the plumbing, the easier it is to stop up the drain". And that certainly seems to be the intent of the Feds and CARB when it comes to diesels.

After retiring from the Navy in '97, I went to work at the Freightliner plant in Cleveland NC, and spent a good bit of that time as either an assembler or inspector on the engine assembly line. In that time I've seen 3 different increments of emissions controls implemented. The last round in '07 was by far the worst.

As far as O2 sensors, you're pretty safe in assuming that anything built before '07 does not have an O2 sensor in the exhaust. Primary change up until that point was adding increasing levels of exhaust gas recirc - EGR.

Besides being pretty bloody stupid from an engine life standpoint - sucking soot and other junk into the intake, combining it with oil vapor from the CCV to form nice gooey deposits that gradually choke off the intake manifold - the intent was to reduce combustion tenps in the cylinders - also reducing efficiency and fuel economy - to reduce production of NOX.

Added change in '07 was to add particulate filters in the exhaust to capture the added soot resulting from use of EGR. And to burn off the soot that accumulates in these filters, they had to add an extra injector in the exhaust or dump extra fuel thru the engine to jack up exhaust temps to regenerate these filters. So now you're burning extra fuel just to clean out that bloody filter - which is resulting in a 25 to 50 percent hit on fuel economy. On vehicles where they simply dumped extra fuel into the engine, and got the programming wrong, they jacked exhaust temps up to the point they were actually melting turbos. And if you don't allow the ECM the chance to regenerate the filter (ie, due to your driving routine), the ECM will put the truck into limp mode and make it undriveable until you allow it to do it's thing and regenerate that blasted filter - 45 minutes to an hour until you can drive the vehicle.

Here's the catch - all the engine manufaturer reps I've spoken with say that if the EPA would allow them to tune the engine for max efficiency and use aftertreatment in the exhaust for NOX - no blasted EGR - soot production would go to virtually zero, fuel economy would take a drastic jump upwards, and other pollutants would see a drastic reduction as well. But the suits at the EPA have decided that they know more about diesels than the people that actually build them.

On the subject of the EPA and biodiesel - the EPA doesn't like biod because they say it drastically raises NOX production - based on a single test of 3 diffeent engines, of which they picked the worst case scenario. But I've read several test reports conducted by the military - accessible online if you do a Google search - on virtually every type of diesel engine they use - that showed no difference in NOX production between ULSD and biodiesel.

Main focus that seems to be driving the EPA - hybrids are politically correct, clean, and green, while diesels are dirty soot-belching monsters that they would prefer to do away with entirely. I've spoken with a gent at one TDR truck meet, who helped (or I should say tried to help) the EPA draft their diesel emissions regs. No testing, no reasearch, nada - he said they were simply sat down in a room with internet access and told to write regulations for diesel emissions from what they could Google on the web. And speaking with EPA personnel while doing this, he said the attitude of a large part of them was that they didn't give one whit what effect these emissions requirements would have - the more restrictive the better, and if it had the effect of eliminating diesel useage in this country, so much the better - they wanted to do social engineering and kill off diesels entirely, and have everyone driving hybrids.

Mitchell Oates
Mooresville NC
'87 MB 300D Turbodiesel
'05 Jeep Liberty CRD (Common Rail Diesel)
05-05-2008 08:47 AM
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mike Offline
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RE: diesels and o2 sensors
I'm very sorry to hear that. There has been suppression on the diesel engine since the since Rudolph Diesel was murdered. It looks like they may finally succeed after all.

The moral of this story is to stock up on pre '07 diesel engines.

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05-05-2008 10:00 AM
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retmil46 Offline
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Post: #8
RE: diesels and o2 sensors
Indeed. My advice to people who have expressed interest in getting a POV diesel vehicle has been to either buy used - pre-07 or preferably pre-04 (when heavy use of EGR was mandated) - or wait until after 2010 (next round of emissions requirements, and hopefully the last) to give them a chance to get the engines and emissions gear sorted out. Kinda like the old advice "never buy the first year of a new model car, wait a year or two until they get the bugs sorted out".

One thing that EGR has done is drastically increase the heat load on the cooling system - the exhaust gas is run thru a heat exchanger to prevent burning up the EGR valve and lower the temp enough so that it doesn't cause problems when reingested into the cylinder intake. Between the '04 and '07 emissions requirements, the size of the radiators on the Class 8 trucks we build has essentially doubled. On the one cab over design we build, they were unable to change the size of the radiator without affecting the cab's ability to tilt up for access to the engine. To handle the increased heat load from meeting '07 emissions, they had to add an auxiliary radiator mounted in the frame and create a plumbing nightmare of coolant hoses - that particular model truck now has a 1300 square inch main radiator and a 500 square inch auxiliary radiator - the change from '04 to '07 emissions added that much heat load.

Mitchell Oates
Mooresville NC
'87 MB 300D Turbodiesel
'05 Jeep Liberty CRD (Common Rail Diesel)
05-05-2008 10:47 PM
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mike Offline
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RE: diesels and o2 sensors
Man, that's too much.

Emissions standards designed by the federal government. Wow what a scary thought!

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05-06-2008 04:38 PM
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