..Philip. wrote:
> Steve wrote:
>
>>Philip wrote:
>>
>>>Are you aware that NOx contaminates the lubricating oil? I am not.
>>>If less soot is being produced, then how is -more- soot being
>>>"pushed past the rings into the LUBRICANT"
>>
>>Ring sealing technology has improved since 1960, but only very
>>slightly compared to improvements in other areas, such as fuel
>>delivery management and forced induction pressures. Combustion pressures
>>tend
>>to be much higher with direct injection, hence there's a bit more
>>blow-by. So even though the combustion gasses may be cleaner, more volume
>>(albeit of cleaner gas) passes through the crankcase. Also, the higher
>>pressures result in higher piston underside temperatures, and that
>>too stresses a lubricating oil.
>
>
> Nissan SD22 (debuted in 1964), indirect injection, advertised compression
> 21:1, non turbo. and oil cooled pistons
> Ford and Dodge Cummins of late ... direct injection, advertised comp 17.5:1
> with turbo, 21.5:1 without, and oil cooled pistons.
>
> From these stats, your claim of "Combustion pressures tend to be much higher
> with direct injection" is not supported. Perhaps you'll clarify.

from
http://www.chevron.com/prodserv/fuel.../L2_6_3_rf.htm

"Since rapid fuel autoignition requires a certain air temperature, an
IDI engine needs a higher compression ratio to achieve the desired air
temperature in the prechamber. IDI engines operate at compression ratios
of about 20:1 to 24:1; while DI engines operate at ratios of about 15:1
to 18:1. The heat losses that necessitate these higher compression
ratios have another, more important effect: they decrease the efficiency
of the engine. IDI engines typically achieve fuel efficiencies that are
10% to 20% lower, on a relative basis, than comparable DI engines."

this text appears to be from the bosch automotive handbook - a superb
publication.

>
> In the case of the SD22, there are pistons with three compression rings and
> those with two compression rings. Depends on application.
>
> It is known that indirect injection while quieter, does result in more soot
> production.
>
> AS I see it, less soot production due to chamber design and better fuel
> management ... MORE than off sets your claim of greater oil contamination
> due to compression ring blow-by so far as oil service life is concerned. Is
> there disagreement?