diesel driving style - Page 4 - PeachParts Mercedes-Benz Forum

psfred · #46 11-16-2003, 11:24 PM

Top end is around 5000 rpm. Most likely the only way you would exceed this is to run downhill on a steep grade in a lower gear with the acelerator floored, not something I'd expect any reasonable person to do. Or maybe downshift at top speed just for the hell of it (I've heard stories of bent valves on BMWs that have both rev limiters and electronic automatics that HAD to have been overreved, so anything is possible).

Not to worry, the hp drops off terribly fast above 4800 rpm, so it's very unlikely that you will overrev an automatic in normal driving. You can overspeed more easily with a manual, but they typically are only in the 4 cylinder models in the US.

I don't worry about it -- I've been driving the 300D to work recently (I hate to, but the 280 burns SO much fuel....) and it runs better than ever. Hard driving doesn't bother an MB diesel at all!

However, no load rpm is a problem -- it's fairly easy to exceed 5100 rpm with the tranny in neutral, and this can be expected to produce the same result as does overspeeding a gasoline engine under no-load conditions -- a thrown rod. No matter how the engine is designed, the piston is being yanked back and forth terribly hard under no-load conditions. Since there is nothing to prevent it, the engine will speed up dramatically, and when it goes fast enough (very little horsepower required to turn the engine), eventually the rod bearings will fail on one of the reversals. Next time round, the crankpin rams the end of the rod through the block.

Peter

Peter

lietuviai · #47 11-17-2003, 10:37 PM

One easy way to get your RPM's over redline is to get the car airborn!

85drtysthbenz · #48 11-17-2003, 11:03 PM

i have a question...i regularly drive my car on the interstate at over,or close to,100mph for almost 2 hours at a time....am i killing my car? i have the 85 300sd with the 617.xxx engine....and at 100mph,my car is running at just under 4000 rpm.....also,when i get off at my exit,the car seems a little sluggish for a few moments after slowing down to city speeds and at redlights it shakes a little bit,not terribly...but definitely more so than if i just drive at "regular" speeds....i hear people say on here a lot "drive it like you stole it"....well i actually do drive my car like i stole it,and im wondering if im going to have to pay the fiddler soon....just fishing for a few opinions

DslBnz · #49 11-17-2003, 11:09 PM

Probably just have some loose carbon.

You will never kill your car if you were driving it for 5 hours every day at 110 mph. With the proper maintenence, it will still go well past 400K miles. Remember, all MB's are designed to be run flat out, every day. ESPECIALLY diesels!

My dad is the most maniacal driver I've ever known. I mean, not swerving in and out of lanes, but always going 100 + mph in his oil-burner. His last one, an '84 300D turbodiesel, lasted 463K miles, and it would have still been going if my dad was able to fix the oil ring when it blew. Unfortunately he was out in the middle of nowhere.

R Leo · #50 11-17-2003, 11:10 PM

Quote:

Originally posted by 85drtysthbenz
im wondering if im going to have to pay the fiddler soon....just fishing for a few opinions

You may not have to pay the fiddler but you will eventually have to pay the fine.

79-240d-project · #51 11-17-2003, 11:44 PM

A little off topic, Mercedes wise, but still a diesel.

I seem to remember an article in the Cummins news letter about the ISB(Dodge pick-up) and no load rpm's. The article stated that no rpm's over 2000 until warmed up and no rpm's over 2800 without a load on the vehicle.

It seems the ISB loves to run really hard with a load on it.

#52 11-18-2003, 12:37 AM

Where do you people get this kind of speed!?!?
I can't even get to 85 before I spot a police car somewhere!

I did get mine past 100mph once, almost reached the water redline but I got to 4400rpm.

BTW, when you all are crusing at/near/past 100mph, what does your temperature gauge reach or level off at? I can cruise at 65mph 95*c and 8psi boost and 75mph 105*c. and 13psi boost.

85drtysthbenz · #53 11-18-2003, 01:02 AM

since ive had this car(a little over 3 yrs) my temp gauge has never went over 100*C, not once.....it usually stays right around 90*C, even at high speeds for long periods...and thats in sunny florida

any of my 100-110mph cruising is always on interstate 75 between Wildwood(central FL) and Valdosta,GA

oh yeah,the only thing not stock on my engine is a manual boost controller i installed a week or so ago....im running 11psi max boost,with the ALDA adjusted,too

#54 11-18-2003, 03:32 PM

I've driven over 100 mph on longer road trips for extended periods and enjoy it, but other than the other drivers on the road, my main concern has been the handling limitations of the car at speed. Its very stable, but that huge steering wheel and less than taut suspension can make it feel like a bit of a drifter. I also think to myself...105 for 3 hours in a twenty year old car...can't be wise. Apparently I'm incorrect on that point. My mechanic even told me when I recently picked up the car.

Oh yeah, my temp has never gone above 100. It usually stays around 80 or so, no matter what I'm doing. It got close to 100 once, in heavy stop and go traffic, hot summer day, and when I got home I realized I was way low on coolant.

toknow · #55 11-18-2003, 03:52 PM

Can somebody, more technically oriented, explain what happen when we press the accelerator in our diesels and when released. I know that there is no throttle in diesels, so the air is flowing all the time, and the IP just spraying the diesel fuel. But, the IP is mechanically driven by engine gears, so it should continue even if accelarator released? what is that thing that controls the fuel there and how it is related to the ALDA (technically)

Another point, the high reviving thing in these engines could result in accelerated wear of the rings and loosing compression through years faster.

About the turbo, is there cars that can be supercharged at lower rpm and turbo charged at higher rpm?

thanks

#56 11-18-2003, 04:34 PM

Quote:

Originally posted by toknow
About the turbo, is there cars that can be supercharged at lower rpm and turbo charged at higher rpm?

thanks

I think others can explain the IP workings better than I can.

As for the turbo you talk about, I have seen people use nitrous blown directly at the turbine in the exhaust manifold to get boost early on.

84300DT · #57 11-18-2003, 04:44 PM

dunno about you guys but whenever i get the blue bomber over about 85 i feel like something's gonna break

but nothing has sofar...

it just feels more comfy at 80 or below

DslBnz · #58 11-18-2003, 05:20 PM

About the cops, I once was on "a run" doing about 95 - 100 mph (in my old 300SD), and an unmarked police car spotted me. He tried to pull me over, but I refused to acknowledge him as I didn't know who it really was. He pulled up next to my SD and maybe signaled for me to pull over. I refused to pay any attention to him. It wasn't until I noticed the lights in the back of the car that I realized what he was. I almost had a stroke. He never pulled me over, strangely enough.

I did reduce my speed DRASTICALLY to 60 - 65 mph after I saw him. His car was a black Lumina, and when I spotted him, he was merging onto the highway. I thought he MIGHT be a cop, but I didn't know for sure. Could've been some crazy trying to pull a gun on me. I'll only stop for Cruisers. At least I know they're cops.