Why do diesels have lower rev limiter?
Discussion
easily sorted...gently rub off the numbers that are ont he rev counter now and then carefully apply some new numbers whereby it starts at 0 and where it currently says 5,000, you put 7 or 8,000 bingo.
All of a sudden the performance matches your visual expectation based on perceived revs...
All of a sudden the performance matches your visual expectation based on perceived revs...
doogz said:
angusc43 said:
paddyhasneeds said:
Sorry to show my lack of engine knowledge here, but why do diesels always have a much lower rev limiter than petrol cars?
Because they are designed to go in tractors and in industrial plant.But diesel engines are good for tractors. A million farmers can't be wrong.
Mikeyplum said:
There is also a good, sort of, tutorial where this yank guy strips down an engine which was victim to the turbo seals going and "running away"... should see the state on the internals! 
This one? http://www.youtube.com/watch?v=WmkHTkmj2_UI love it at 5 min in when he is explaining the spun bearings and says "this engine was on the edge of taking a s
t!"It's a very good video.
Charlie Foxtrot said:
This one? http://www.youtube.com/watch?v=WmkHTkmj2_U
I love it at 5 min in when he is explaining the spun bearings and says "this engine was on the edge of taking a st!"
It's a very good video.
Can't tell at the moment as I'm in work (Damn you "Media Streaming Banned" filters!!) I love it at 5 min in when he is explaining the spun bearings and says "this engine was on the edge of taking a s
t!"It's a very good video.
But I'm guessing that's the one!
I love how excited he is about a mashed engine!!
doogz said:
angusc43 said:
doogz said:
angusc43 said:
paddyhasneeds said:
Sorry to show my lack of engine knowledge here, but why do diesels always have a much lower rev limiter than petrol cars?
Because they are designed to go in tractors and in industrial plant.But diesel engines are good for tractors. A million farmers can't be wrong.
Just thinking about this on my walk around the countryside (as you do).
Now a four pot single turbo diesel (like our old Astra 1.9CDTi 150) can be hustled along fairly quickly BUT the useful power band is 2500rpm to about 4000rpm - 1500 of useful revs.
But then look at a decent bi-turbo six pot like our current 335d - useful rev range is 1500 (when turbo one kicks in) to just under the red line - 5000rpm. That's 3500 useful revs - more than twice the four pot.
However most judge all diesels on mainstream four pots and that's that - fair enough the view of them is fairly dim.
Now let's compare to a mad bad purists high revving car - maybe a CTR, maybe a more exotic 911 Turbo - useful rev range for a CTR? I'd say 6000-9000. And the 911 Turbo - no point revving it about 5500rpm and the fun starts at 3000ish - so 2500rpm of fun.
So while the noise isn't as good (I'd say a wrung out 330d/35d unit sounds better than most four pots though), the "fun band" is similar.
Ready for a cr4p analogy?
It's like only taking notice of boxers that punch to the head while ignoring body punch boxers like Hatton because they don't box as "pretty." Both come up with the same result - going quickly - but one is more glam and therefore "cooler."
Now a four pot single turbo diesel (like our old Astra 1.9CDTi 150) can be hustled along fairly quickly BUT the useful power band is 2500rpm to about 4000rpm - 1500 of useful revs.
But then look at a decent bi-turbo six pot like our current 335d - useful rev range is 1500 (when turbo one kicks in) to just under the red line - 5000rpm. That's 3500 useful revs - more than twice the four pot.
However most judge all diesels on mainstream four pots and that's that - fair enough the view of them is fairly dim.
Now let's compare to a mad bad purists high revving car - maybe a CTR, maybe a more exotic 911 Turbo - useful rev range for a CTR? I'd say 6000-9000. And the 911 Turbo - no point revving it about 5500rpm and the fun starts at 3000ish - so 2500rpm of fun.
So while the noise isn't as good (I'd say a wrung out 330d/35d unit sounds better than most four pots though), the "fun band" is similar.
Ready for a cr4p analogy?
It's like only taking notice of boxers that punch to the head while ignoring body punch boxers like Hatton because they don't box as "pretty." Both come up with the same result - going quickly - but one is more glam and therefore "cooler."
Mikeyplum said:
Charlie Foxtrot said:
This one? http://www.youtube.com/watch?v=WmkHTkmj2_U
I love it at 5 min in when he is explaining the spun bearings and says "this engine was on the edge of taking a st!"
It's a very good video.
Can't tell at the moment as I'm in work (Damn you "Media Streaming Banned" filters!!) I love it at 5 min in when he is explaining the spun bearings and says "this engine was on the edge of taking a s
t!"It's a very good video.
But I'm guessing that's the one!
I love how excited he is about a mashed engine!!
ked engines. It's great, nothing I didn't know already but really good wathing and a guy who must really enjoy his work.Charlie Foxtrot said:
Mikeyplum said:
Charlie Foxtrot said:
This one? http://www.youtube.com/watch?v=WmkHTkmj2_U
I love it at 5 min in when he is explaining the spun bearings and says "this engine was on the edge of taking a st!"
It's a very good video.
Can't tell at the moment as I'm in work (Damn you "Media Streaming Banned" filters!!) I love it at 5 min in when he is explaining the spun bearings and says "this engine was on the edge of taking a s
t!"It's a very good video.
But I'm guessing that's the one!
I love how excited he is about a mashed engine!!
ked engines. It's great, nothing I didn't know already but really good wathing and a guy who must really enjoy his work.I remember chuckling at that one video and haven't seen the rest, so will have a butchers!
Vladimir said:
Yes Angus and you forget that your low revving V8 is actually not unlike a big diesel.
Well in some ways you're right. Lots of bottom end, yes. Less top end than the later n/a 5.5. But loads more top than any of the diesels. And silky smooth to boot.Vladimir said:
Except most handle better than your corroding old E class luxobarge...
Steady on. It's not corroding (it's galvanised). But yes, it's a luxobarge. Air suspension makes it surprisingly handy, though.Vladimir said:
E55 AMG - maybe.
E500? Naaaah.
Fair enough. It's not an E55. But it's still a very refined petrol which suits the car's character very well. E500? Naaaah.
Edited by angusc43 on Monday 16th May 22:54
doogz said:
angusc43 said:
doogz said:
angusc43 said:
doogz said:
angusc43 said:
paddyhasneeds said:
Sorry to show my lack of engine knowledge here, but why do diesels always have a much lower rev limiter than petrol cars?
Because they are designed to go in tractors and in industrial plant.But diesel engines are good for tractors. A million farmers can't be wrong.
It just seemed like you were being stupid, obviously i didn't get that you were being a bit sarcastic first time round.
Vladimir said:
Just thinking about this on my walk around the countryside (as you do).
Now a four pot single turbo diesel (like our old Astra 1.9CDTi 150) can be hustled along fairly quickly BUT the useful power band is 2500rpm to about 4000rpm - 1500 of useful revs.
But then look at a decent bi-turbo six pot like our current 335d - useful rev range is 1500 (when turbo one kicks in) to just under the red line - 5000rpm. That's 3500 useful revs - more than twice the four pot.
However most judge all diesels on mainstream four pots and that's that - fair enough the view of them is fairly dim.
Now let's compare to a mad bad purists high revving car - maybe a CTR, maybe a more exotic 911 Turbo - useful rev range for a CTR? I'd say 6000-9000. And the 911 Turbo - no point revving it about 5500rpm and the fun starts at 3000ish - so 2500rpm of fun.
Really? Looking at a dyno-chart for one the 335d seems to make peak torque at 1500rpm then hits peak power at 4200rpm after that it quickly tails off. 4200-1500 gives you a mere 2700rpm of usefulness. Now a four pot single turbo diesel (like our old Astra 1.9CDTi 150) can be hustled along fairly quickly BUT the useful power band is 2500rpm to about 4000rpm - 1500 of useful revs.
But then look at a decent bi-turbo six pot like our current 335d - useful rev range is 1500 (when turbo one kicks in) to just under the red line - 5000rpm. That's 3500 useful revs - more than twice the four pot.
However most judge all diesels on mainstream four pots and that's that - fair enough the view of them is fairly dim.
Now let's compare to a mad bad purists high revving car - maybe a CTR, maybe a more exotic 911 Turbo - useful rev range for a CTR? I'd say 6000-9000. And the 911 Turbo - no point revving it about 5500rpm and the fun starts at 3000ish - so 2500rpm of fun.
eldar said:
This is the answer. Plus the risk of scouring lubrication oil and using it as fuel...
http://www.youtube.com/watch?v=5zx3qKX_Pno
Not sure what that's got to do with engine revs? Landrovers like the one you posted, and most other diesels that suffer from a 'runaway', do it because the turbo seals fail.http://www.youtube.com/watch?v=5zx3qKX_Pno
It can get worse than just the engine blowing up.
I was involved with a few others in helping the skipper of a 50Ft fiberglass catamaran ferry a few years back.
The diesel in one hull had run away, & finally blown up. He thought he was in enough trouble, but had got it into harbour & tied to a jetty. No one had noticed in the excitement that the side with the blown motor was getting lower in the water, until it was down a couple of feet.
A bit of the blown engine had gone through the hull, leaving about a 4" hole. A lot of water comes through a 4" hole. We tied a large 112 footer alongside, while someone found something to shove into the hole from the outside underwater. Everything in that engine room was under water, & he had to go & buy a 5 horse power petrol pump to pump it out, & keep it out. Poor bugger.
I was involved with a few others in helping the skipper of a 50Ft fiberglass catamaran ferry a few years back.
The diesel in one hull had run away, & finally blown up. He thought he was in enough trouble, but had got it into harbour & tied to a jetty. No one had noticed in the excitement that the side with the blown motor was getting lower in the water, until it was down a couple of feet.
A bit of the blown engine had gone through the hull, leaving about a 4" hole. A lot of water comes through a 4" hole. We tied a large 112 footer alongside, while someone found something to shove into the hole from the outside underwater. Everything in that engine room was under water, & he had to go & buy a 5 horse power petrol pump to pump it out, & keep it out. Poor bugger.
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