Lean idle smells like diesel

[quantum]

I'm currently running the S60 cal on my Omni while I fiddle with other cals for it(2.2l CB, lots of mods) and noticed the idle for the S60 cal is anywhere from 17:1 - 16:1 when the car is warm. This caused a unsteady idle which doesn't bother me, but I noticed that it kind of smells like the car is burning diesel when while it idles lean like that. Anyone else ever have that happen or know if it's something I should look into? Thanks.

[IROCNOROLL]

OK... I'll bite. If you have a vacuum leak, the mix will run lean, and there will be an unstable idle to match. In open loop, the cpu will not react and provide a higher fuel spray.

Or a lean misfire which loads a little more unused 02 into the exhaust, which may drive the readings to the lean side, and give you a hot funny smell. Or a bit of an exhaust leak which will drive the meter lean, and again may give you the smell.

If the system has made it into closed loop, the computer, depending on the cal I suppose, should respond by lengthening the pulse width on time to the injectors, covering the lean. But if there is an exhaust leak, adding to the fuel trim will do nothing to the meter readings, but will give you a rich miss, without the meter rnding. And the smell.

[quantum]

Thanks for responding. There is no closed loop with the S60 cal, pure fuel tables. I'm not looking for a reason why it's running lean; I know that is the cal. I was just curious about the fact that the smell from my lean idle is a bit like diesel. I'm guessing that being that lean produces more NOX so it has a bit of a diesel smell to it, but I though I would post up to see if there could be another explanation.

[IROCNOROLL]

Being that lean can't be good for moving things inside the engine either, me thinks. Is it possible that there is a hint of burnt engine oil there too. Not enough to have blue show, but enough to give the hint of odor?

[turbovanman²]

That smell is NOx, makes me wanna puke,

[IROCNOROLL]

That smell is NOx, makes me wanna puke,

Must be building some way extreme hot combustion chamber flame front temps if your building that kind of noticeable NOx at idle.

It generally takes running temps of at least 22-2300 deg F to make much NOx, and if it's that noticeable, probably closer to 2500 deg F. At idle? Wow!

A little extreme for my world, but that's just me. Are you running a bunch of timing or just so lean to build that heat? Both? Surge at idle may indicate a vacuum leak which can contribute to lean, but Wow!

Makes me wonder how high the NOx production is going when you run the car hard?

[turbovanman²]

Create a lean misfire on a carb vehicle at idle NOx city.

[quantum]

Must be building some way extreme hot combustion chamber flame front temps if your building that kind of noticeable NOx at idle.

It generally takes running temps of at least 22-2300 deg F to make much NOx, and if it's that noticeable, probably closer to 2500 deg F. At idle? Wow!

A little extreme for my world, but that's just me. Are you running a bunch of timing or just so lean to build that heat? Both? Surge at idle may indicate a vacuum leak which can contribute to lean, but Wow!

Makes me wonder how high the NOx production is going when you run the car hard?

My idle EGT is ~1000 and once the revs get above 2200 rpm the s60 fuel tables run at just rich to stoic until boost when it's ~11:1 with 1400 EGT.

[IROCNOROLL]

My idle EGT is ~1000 and once the revs get above 2200 rpm the s60 fuel tables run at just rich to stoic until boost when it's ~11:1 with 1400 EGT.

I hear you. The thing you need to understand is not what is happening outside the chamber in the mani, it's what's happening in the chamber during the flame peak burn temps. While you are reading 1000 deg at the EGT probe, typical flame front temps run at least double that plus, when everything is actually normal. And EGT probe placement in the mani will also change what the read temps are showing. Different cylinders normally run at different temperatures to start with. It is an inherent part of any internal combustion engine. Set up 4 EGT sensors in exactly the same position in relation to the 4 exhaust ports, and you will see very different temperature trends hole to hole at almost any RPM and load. Variances in intake manifold flow port to port, variances in spark timing hole to hole, minor differences in injector flow hole to hole all contribute. Even the actual varied air/fuel charge cycle to cycle on a given cylinder causes differences in the required KV to ionize the gap, (or initialize the spark kernel), and this varies the amount of burn time available from the coil. Watch a secondary ignition scope wave form. The spikes on the waveform are constantly bouncing firing line to firing line, cylinder to cylinder, even at idle. All you are really doing by building a tune for an engine is averaging the good to the bad through a given load and RPM range. Even the readings you see on the a/f gauge are just an average of what amount of O2 is really passing the sensor tip at that time.

Like turbovanman says... you are smack dab in the middle lean misfire territory to make the smell. High flame front temps generate a lot of NOx. The cooling system, along with the aluminum head and the piston dome are working overtime performing the job of being a heat sink, and drawing off a lot of the generated heat before the EGT probe see's the residual temperature in the mani. Even the exh. mani is an acting heat sink. This is the main reason that Mopar engineering added oil squirter's to shoot the bottom of the pistons on the SRT4's. It aids in absorbed heat removal from the piston dome.

One of the short comings of the 2.2 / 2.5 block is the siamesed cylinders, as they prevent coolant from being available uniformally all the way around the top of the cylinder. This uneven cooling contributes to hot spots, and the uneven heat distribution also causes the top of the cylinders to go out of round during high heat events. This will affect the ring package to cylinder wall sealing characteristics. This contributes to oil contamination in the chamber As well as the poor cylinder sealing drops the compression in the cylinder. Oil weakens the air / fuel mixture, lowering the mixtures resistance to pre-ignition, and everything cascades down from there. We won't even start on cylinder deck / wall movement from heat, and how that affects the life and seal of a head hasket. And then engineering, in the wisdom of the bean counters carried that part of the block design over to the newer 2.0 / 2.4 blocks in part to save on retooling $$.

[Tony Hanna]

Is there a .tbl file for the S60 cal? If so, why not just dial in a little more fuel at idle? If the cal is fine otherwise, I'd think that would be the reasonable solution.

[zin]

I hear you. The thing you need to understand is not what is happening outside the chamber in the mani, it's what's happening in the chamber during the flame peak burn temps. While you are reading 1000 deg at the EGT probe, typical flame front temps run at least double that plus, when everything is actually normal. And EGT probe placement in the mani will also change what the read temps are showing. Different cylinders normally run at different temperatures to start with. It is an inherent part of any internal combustion engine. Set up 4 EGT sensors in exactly the same position in relation to the 4 exhaust ports, and you will see very different temperature trends hole to hole at almost any RPM and load. Variances in intake manifold flow port to port, variances in spark timing hole to hole, minor differences in injector flow hole to hole all contribute. Even the actual varied air/fuel charge cycle to cycle on a given cylinder causes differences in the required KV to ionize the gap, (or initialize the spark kernel), and this varies the amount of burn time available from the coil. Watch a secondary ignition scope wave form. The spikes on the waveform are constantly bouncing firing line to firing line, cylinder to cylinder, even at idle. All you are really doing by building a tune for an engine is averaging the good to the bad through a given load and RPM range. Even the readings you see on the a/f gauge are just an average of what amount of O2 is really passing the sensor tip at that time.

Like turbovanman says... you are smack dab in the middle lean misfire territory to make the smell. High flame front temps generate a lot of NOx. The cooling system, along with the aluminum head and the piston dome are working overtime performing the job of being a heat sink, and drawing off a lot of the generated heat before the EGT probe see's the residual temperature in the mani. Even the exh. mani is an acting heat sink. This is the main reason that Mopar engineering added oil squirter's to shoot the bottom of the pistons on the SRT4's. It aids in absorbed heat removal from the piston dome.

One of the short comings of the 2.2 / 2.5 block is the siamesed cylinders, as they prevent coolant from being available uniformly all the way around the top of the cylinder. This uneven cooling contributes to hot spots, and the uneven heat distribution also causes the top of the cylinders to go out of round during high heat events. This will affect the ring package to cylinder wall sealing characteristics. This contributes to oil contamination in the chamber As well as the poor cylinder sealing drops the compression in the cylinder. Oil weakens the air / fuel mixture, lowering the mixtures resistance to pre-ignition, and everything cascades down from there. We won't even start on cylinder deck / wall movement from heat, and how that affects the life and seal of a head gasket. And then engineering, in the wisdom of the bean counters carried that part of the block design over to the newer 2.0 / 2.4 blocks in part to save on retooling $$.

Me thinks me smells an engineer... Lots of good info there!

Mike

[quantum]

Is there a .tbl file for the S60 cal? If so, why not just dial in a little more fuel at idle? If the cal is fine otherwise, I'd think that would be the reasonable solution.

I already have.