Will switching from Synthetic to Dyno oil harm my engine?

Actually, that's not true for a diesel. Spark-ignition engines are limited in both CR and boost (or lets say the sum effects of boost and CR, which equates to the combustion chamber pressure at the instant before ignition) because detonation will occur at some point, no matter how high the octane of the fuel used. A diesel, on the other hand, has no such mechanical limit except the mechanical strength of the connecting rods, bearings, and crankshaft- and these effects are WAY beyond consideration in most purpose-built engines (although they're a real issue in some gasoline engine conversions like Powerstroke and Duramax). In practical terms, NOX production is the real limiting factor when you have to meet emissions requirements.

And as for the obvious effects of higher combustion pressures on oil contamination, I really have to wonder how much real-world experience you have... have you EVER observed an engine operating under high load and high boost? Gasoline or diesel? In either case, the typical thing you can see is a shocking amount of vapor blowing out the crankcase breather (way beyond what can be handled by positive crankcase ventilation). And that's on a brand-new just-broken-in engine on a dynomometer, not some 400,000 mile tired-out rig, either.

The REAL reason that there is such a difference between the engines in your example (SD22, Cummins, and Navistar/Powerstroke) is because one is an IDI and the other two are DI, which demand less compression for starting (when the turbo isn't operating anyway).

PV = nRT. heating is adiabaic. the above sounds like constant volume which clearly is not the case.

ie. combustion temperature

T1 - T2 / T2, where T1 is combustion, T2 is exhaust, in Kelvins.

because it's hard to get T2 lower.

good points mike! i've had similar experiences to yours, and often do stuff myself if i have the time or inclination. but, like you, there's stuff i can't do because i don't have the tools or won't do because i don't have the time. i don't do alignment or crank regrinds for instance. while it can be apita, and if you call enough people, you can find people that know their business.

as for replacement vs. repair, replacement makes perfect economic sense /if/ and only if the diagnosis is good. just bought a car from someone after they'd spent a fortune on trying to get it to start properly. it still wouldn't so they gave up. new distributor, new plug leads, new injectors, new starter, new battery, the works. turns out, incredibly, that the morons at the garage had not bothered to change the plugs for what looked like over 100k, so of course, absent electrodes, the plugs weren't much good! if it /had/ been a distributor problem, as you say, the labor of repair vs. replace with the uncertainty of subsequent reliability means that replacement is definitely the way to go. all about the quality of the diagnosis.

BMEP is the highest pressure attained during combustion. This is affected by numerous factors, not the least of which is the mechancial compression ratio and boost pressure. All else being equal and with natural aspiration, do you disagree that BMEP with 24:1 is going to be higher than BMEP with

17:1?

snipped material regarding gasoline since my dialog is regarding diesel.

We should agree here because detonation is combustion starting before scheduled ignition, which in the diesel arena begins when fuel first exits the injector.

Spent 12 years driving line haul, some of that as O/O. Being that road draft tubes are illegal since about 1990, one does not see blow-by belching forth under the cab. I recall well the days when you'd see a turbo glowing dull red on a long pull. Obviously the driver wasn't paying attention to the pyrometer limit of 1100 degrees. The company I retired from kept OTR trucks to 600k miles typically. The engines were fine for the most part. Turbos however were considered expendable items.

I recall making that distinction some time ago regarding soot production. ID injection diesel does not have the flame front dampening that IDI combustion chambers provide. Of course, there are trade-offs but emissions and 'greeness" rule so .... IDI.

Rapidly rising pressure results in heat. You can have pressure but without heat ... no ignition.

:) Maybe I'm just big headed, but > if you withdraw from the qualification process, you can't complain

I never complained about lack of candidates?

And believe it or not, I know enough people in medical areas to know the number of mistakes (that are generally covered up) are actually scarily high, and YES I do worry about the guy checking the bolts on the wings - being an engineer has instilled into me a complete lack of trust of anyone i dont *know* personally and know the quality of their work.

I know an aircraft technician, and I know the quality of his work is good, I've seen it with my own eyes. I'd have him help me on my car, but I'd be double checking everything myself.

I DO qualify them myself, and I've yet to meet someone i trust to do a better job than me. I know that i may take longer, I may have to buy an extra tool, but I know what im doing and i know i do it right - im not leaving it to whether or not someone forgot to torque something up when the finished for their coffee break. I'm also not trusting someone who gets paid more for the more work they fit into a day. Or for finding more things to replace - tis a totally backwards thing to do in my view. Why trust someone to do something I can do myself. And when i have to, say i needed a block honing or turbo rebuild, yes i am very untrusting and dislike being put in that position.

I've seen a lot of these places, and worked in a few. Worked in a few scientific labs, seen the shortcuts people make. Unless I can see the work being done, or know the person who is doing it personally it aint being done.

The vast majority of main/little/big end seizures are oil starvation related. There are few other things capable of causing it, but if i had symptoms of low pressure I'd have the bottom off the engine to check the lot. Job done properly, not either a)guessed at or b)replaced sequentially like a dealer would. Couple of my mates have worked as spanner monkeys in dealerships, ive seen how they work, and I've also seen how they take fast cars like mine and rag the crackers off it while its left there. Main dealers, more so specialists. Trust yourself, if you dont know - learn.

J

Since a 17:1 is likely to be direct injection and the over-twenty to one will be indirect, then it is likely that the 17: 1 will have the higher peak pressure, not least because the pressure rises so suddenly to the peak. This is why direct injection engines are more noisy. Of course technology advances and it is now possible to limit the peak pressure by injecting sequentially in up to five stages for each power stroke and each cylinder can be adjusted dynamically in real time using individual knock sensors to adjust the fuel volume for each injector. Modern fuel injectors of the piezzo controlled type each have a bar code which is read by a laptop which informs the ECU which setting to apply to match it to each other injector in the system. With this constant then everything can be controlled with unbelievable accuracy.

Huw

I don't understand what you are implying here. Are you implying that IDI engines are greener or the other way around?

Huw

Sorry Huw. You do not get to rewrite the question via your answer. The passage "All else being equal" is germane.

Agreed. But this gracious contribution of yours is beyond the current scope. But we'll get to it soon! LOL You know how these threads evolve.

You inferred on the simple level. I know my audience. :-)

Yes Huw, all this is appreciated but a dodge from the question I posed to you.

See the comment I made just moments ago. Shades of gray represent the superficial understanding. ;-) From a very qualified Cummins source, I've been told I a good grasp of the interdependent variables. How the fuel delivery basics can be electronically manipulated is an ongoing education.

But they cannot be equal because there are no IDI engines running 17:1 and no DI running remotely near to 24:1. You may know that IDI engines do not incorporate the combustion chamber, as such, within a recess in the piston crown which is the case with all DI diesels.

Huw

Well then on a simple level the presence of a turbocharger does not correlate to increased soot production. That is the simple truth.

Huw

*snip*

Who said anything about a light? there wasn't one, the note change happened about a mile earlier. As I said earlier, he KNOWS cars. he was a semi-pro rally driver, and did all his own race prep, and he had been a very highly trained engineer for the previous 330+ years (mainly on oil and other fluid ssytems, starting out on the fuel systems of concord, at lucas.

I myself am a design/research engineer, and I also do a lot of safety work (when i was based in the UK, i'd have comapnies phoning me up from california to ask for help, or time, or whatever, hell, the US govt. even reqested me at work on a project at their old navel base in the middle of SF bay, and despite that, I don't have such a high handed, arse-faced opinion o my abilities.

I wouldn't trust anyone with a pigheaded self superior attitude like yours to change a flat. People like you give all the rest of us a bad rep, because you know it ALL, and you refuse to listen.

If you know his work is good, and he's a friend, and you STILL insult his basic competance, then i've very surprised a) that you have any friends and b) that you are anything but self employed

I know an aerospace engineer too. I can remeber her fiesta breaking down outside where she worked. One of the engineers comming to use the wind tunnel made some comments about her competancy to work on the car. He gave her the same kind of gab to his mates whilst they were waiting for their car (a brand new hyundai, about to go into the wind-tunnel for testing iirc) to arrive on the banck of the truck. how he'd let a woman work on this hyundai, but he'll be double-checking everything to make sure she didn't f*ck up. Guess who was the shitty engineer who made all the faults? Here's a hint, it wasn't the 5'3

27yo girl... No, it was the loud mouthed, self important bloke who wouldn't trust anyone elses work. Thing was, now he's unemployed. no-one trusted his work. He was so busy checking everyone elses work, that he never did anything himself, and what he DID do was, in a word, bleeding terrible.

Ah ... we are separated by a common language. ;-) I could have worded my thought better.

The slower flame propagation imposed by IDI chamber design also makes for more soot and requires more timing lead. ID chambers don't have the "nooks and crannies" (so to speak) so flame propagation is faster which in turn requires less timing lead to achieve BMEP at the same number of degrees ATDC as an IDI ... all else being equal. It's really amazing how much of the diesel "cackle" you can remove by retarding injection timing. But you'll lose power and gain a smokier exhaust.

But THAT was the statement I made. "All else being equal." That examples may or may not actually exist is not relevant.