Its a fairly well known fact in the gasser world that you want your cylinders and heads(coolant) as cold as possible and your oil as hot as possible for the most horsepower.

One big reason a snowmobile engine lives just fine at 15:1 compression ratio on 92 octane fuel, they rarely run above 130 degrees.

Of course a diesel is a different breed indeed.

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81 300SD daily driver/project
86 420SEL (sold)
85 380SE(in the graveyard)

metal contact and friction occur in both types of engine just the same... heat is a catalyst for wear.

it reduces the lubricating abilities of oils and softens metals.

science project:
next time you're cooking - slide the pan on the cooking surface.. wait until full temp, then slide again... What are your results?

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What is normal operating temp for my 300SD. I cant seem to find a straight answer. My car runs at just a bout the little line below 80deg C. Too cold I know, but from Nevada to Washington a big change in ambient temp

Ian

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Regards,
Ian White

1995 E300 Diesel w124 OM606
2014 E550 w212 M278 biturbo

2001 BMW 740i E38 M62 (past)
1981 300SD w126 OM617 (past)

I ran a 160 in the truck, didn't like it. Never got warm enough for my tastes. Gen III/IVs run better warmer.

FWIW - this is my fourth Gen III from GM. I do my own tuning on them.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Thats how both my vehicles run and its perfectly fine, UOAs done on both reveal very good oil performance and minimal wear metals, thats all I need to now.

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99 Gurkha with OM616 IDI turbo

2015 Gurkha with OM616 DI turbo

2014 Rexton W with OM612 VGT

I run the stock stat in all my benzes.

I have run cooler stats in several of my us built trucks over the years to correct poor performance related to poor smog control design.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Unless the oil is getting past 100*c, thats not true.

15psi is too high, you're just restricting the exhaust. More than 12psi is useless unless you've removed the internal full load limiter.

Hmmmm....

I would have to say that when results argue with theory, I tend to believe the results. I started out with 10 psi of boost, initally making the rough setting on the bench with regulated air pressure. IIRC, this resulted in approximately 7mm (.275") of threads visible above the diaphragm piston.

Performance was quite good at 10 psi, so I began increasing boost in 2 psi increments and checked acceleration with a stopwatch from 50 to 100 mph with the kickdown disabled.

Since 12 psi made a noticeable difference in acceleration, I increased boost pressure to 14 psi and more improvement was noted. I also verified these readings using the 617.950 Shop manual recommendation of removing the air filter element and 'dragging' the brakes to keep engine rpm at 4000 in second speed range.

Increasing the boost pressure to 16 psi resulted in a power loss and verification that the electrical over-boost protection circuit was working. It will drive the rack back towards the idle position when boost pressure reaches 1.1 BAR (16.1 psi) on the 617.950 engine.

Now, without getting into a lot of technical specifications without my tuning notes at hand, I can tell you that my full load limit adjustment, inconjunction with adjustments to the ALDA have been performed on this IP. I had this done by John at Advanced Diesel Systems in Fresno.

In my most humble opinion, if you raise boost pressure and the car is verifiably faster under load, then the likelihood that you are 'restricting' the exhaust is highly unlikely...Robert

Please read my post again where it says "unless you've removed the internal full load limiter."

Yes, but I dare say it wasn't removed, only adjusted and this was done after the increase in boost pressure experiment...Robert

No difference. The full load adjustment only has control of 20hp over stock.

Could you explain that to a higher degree of specificity for me???

No, it cannot be simplified any further than what I have already said.

Ok...

So, you are saying that, in your opinion, the full load stop has direct influence over fuel management in a manner that would equate to an approximate gain of 20 BHP???

I can easily see preferring a 60 degree thermostat. Although our winters do get down to 0-10 F on the worst days, our summers get miserable. 90-95 air temp, 100-110 or higher coming off the asphalt... I've put better fan clutches, better fan blades, everything in my #14 SDL, and it still does its best to overheat given the opportunity in the summer. It also apparently hasn't got enough horsepower to climb a 7% grade with the a/c on - when I shut the compressor off, the temp goes to 100 and stops, when I leave it on it just keeps climbing until I get scared and back off and shut the air down. To me this suggests a barely-adequate cooling system... the 80* thermostat is new within a year or two, the radiator is new within two or three years... everything that can be replaced has been replaced, and the thing is just marginal for this climate. Having an extra 20 degrees advantage on the thermostat appeals to me, especially since hard interstate runs in hot summers defines my driving experience for most of the year.

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~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL