Power and Torque question
Discussion
I know it's been done to death on here but I have a specific question.
Would there be much difference in an engine which produces 122bhp and 207lbs/ft torque and another that produces 143bhp and 221lbs/ft.
Also compare the same 143/221 engine to a 177/258 engine.
This is in the same car and all engines are diesel.
Just trying to figure out which engine would be the best in real world driving rather than looking at power figures and 0-60 times. I realise that the first one will be the slowest and the last one will be the fastest, but by how much is what I want to know.
I suspect I should go for the 177/258 but these are more expensive to buy and are slightly more thirsty.
Hope all this makes sense!
Thanks
Would there be much difference in an engine which produces 122bhp and 207lbs/ft torque and another that produces 143bhp and 221lbs/ft.
Also compare the same 143/221 engine to a 177/258 engine.
This is in the same car and all engines are diesel.
Just trying to figure out which engine would be the best in real world driving rather than looking at power figures and 0-60 times. I realise that the first one will be the slowest and the last one will be the fastest, but by how much is what I want to know.
I suspect I should go for the 177/258 but these are more expensive to buy and are slightly more thirsty.
Hope all this makes sense!
Thanks
HustleRussell said:
I suggest you drive them all; peak output figures tell you little about the tractability and smoothness of the engine.
ETA: in my experience, the more powerful diesel engines often have peaky and unpleasant power deliveries and require much stirring of gear knob to keep on the boil.
I agree, the feeling of having a tiny powerband is more pronounced in powerful diesels. Also expect traction issues when trying to pull away briskly if it is FWD.ETA: in my experience, the more powerful diesel engines often have peaky and unpleasant power deliveries and require much stirring of gear knob to keep on the boil.
HustleRussell said:
I suggest you drive them all; peak output figures tell you little about the tractability and smoothness of the engine.
ETA: in my experience, the more powerful diesel engines often have peaky and unpleasant power deliveries and require much stirring of gear knob to keep on the boil.
I drove the lower powered one yesterday but thats it up to now. I suspect I'll find it hard to get all 3 to drive back to back which would be best.ETA: in my experience, the more powerful diesel engines often have peaky and unpleasant power deliveries and require much stirring of gear knob to keep on the boil.
I'm going from a petrol 1.6 turbo which produces 175bhp and 192lbs/ft torque. Our current car felt a lot faster than the 122/207 which I expected it would.
The car in question is a BMW 1 series so that answers the fwd issues if it is a larger output diesel.
BMW 1 series by any chance? 
Have a look at the range of RPM over which the peak torque figure applies.
Some cars will hold 'peak torque' over a 2000 RPM range (ie peak torque in a plateau between 1750 and 3750 RPM). Some will peak and drop off (like Mercedes 250 CDI engine, 369lbft but only in a 200RPM range between 1600-1800 RPM range, and down to a couple of hundred lbft by 4250RPM).
BTW, the 118d is nippy but left wanting on occasion. The 120d is quite a bit quicker and not much worse on MPG but has slightly shorter gearing than the 118d (which accounts for some of the acceleration benefit and MPG penalty).
The 123d has shorter gearing again and is really not very good on fuel at motorway speeds (compared to the 18d and 20d).
I can't comment on the 116d as I have not driven one, but it doesn't appear to be any more economical or cheaper to tax than the 118d, and it's only going to be slower!
Have a look at the range of RPM over which the peak torque figure applies.
Some cars will hold 'peak torque' over a 2000 RPM range (ie peak torque in a plateau between 1750 and 3750 RPM). Some will peak and drop off (like Mercedes 250 CDI engine, 369lbft but only in a 200RPM range between 1600-1800 RPM range, and down to a couple of hundred lbft by 4250RPM).
BTW, the 118d is nippy but left wanting on occasion. The 120d is quite a bit quicker and not much worse on MPG but has slightly shorter gearing than the 118d (which accounts for some of the acceleration benefit and MPG penalty).
The 123d has shorter gearing again and is really not very good on fuel at motorway speeds (compared to the 18d and 20d).
I can't comment on the 116d as I have not driven one, but it doesn't appear to be any more economical or cheaper to tax than the 118d, and it's only going to be slower!
texasjohn said:
BMW 1 series by any chance?
Have a look at the range of RPM over which the peak torque figure applies.
Some cars will hold 'peak torque' over a 2000 RPM range (ie peak torque in a plateau between 1750 and 3750 RPM). Some will peak and drop off (like Mercedes 250 CDI engine, 369lbft but only in a 200RPM range between 1600-1800 RPM range, and down to a couple of hundred lbft by 4250RPM).
BTW, the 118d is nippy but left wanting on occasion. The 120d is quite a bit quicker and not much worse on MPG but has slightly shorter gearing than the 118d (which accounts for some of the acceleration benefit and MPG penalty).
The 123d has shorter gearing again and is really not very good on fuel at motorway speeds (compared to the 18d and 20d).
I can't comment on the 116d as I have not driven one, but it doesn't appear to be any more economical or cheaper to tax than the 118d, and it's only going to be slower!
Yes, it is a 1 series.Have a look at the range of RPM over which the peak torque figure applies.
Some cars will hold 'peak torque' over a 2000 RPM range (ie peak torque in a plateau between 1750 and 3750 RPM). Some will peak and drop off (like Mercedes 250 CDI engine, 369lbft but only in a 200RPM range between 1600-1800 RPM range, and down to a couple of hundred lbft by 4250RPM).
BTW, the 118d is nippy but left wanting on occasion. The 120d is quite a bit quicker and not much worse on MPG but has slightly shorter gearing than the 118d (which accounts for some of the acceleration benefit and MPG penalty).
The 123d has shorter gearing again and is really not very good on fuel at motorway speeds (compared to the 18d and 20d).
I can't comment on the 116d as I have not driven one, but it doesn't appear to be any more economical or cheaper to tax than the 118d, and it's only going to be slower!
Notice you had a 118d John. What sort of mpg did you get?
Peak figures don't mean much. Its how and where they are made and the under the curve performance. If it is a 1 Series then I believe the 123d uses quite a unique turbo setup compared to the other models and has a much broader power band and a flatter torque curve held higher in the rpms.
Look in the back pages of the 1 series brochure for the peak torque range.
MPG -
Was getting around 48-53 on the daily commute and would get high 50s on a run. Could get into the 60s if the long run was done at 60mph. Personal best was 74mpg on a 250 mile trip but literally did 55 all the way! I don't believe the 120d is much less frugal than that.
MPG -
Was getting around 48-53 on the daily commute and would get high 50s on a run. Could get into the 60s if the long run was done at 60mph. Personal best was 74mpg on a 250 mile trip but literally did 55 all the way! I don't believe the 120d is much less frugal than that.
Slashmb said:
Does anyone know where I can find the torque curves for these engines to view online? I remember looking a few years ago and gave up in the end as I couldn't find any.
Your best bet will be to drive them all and see what you like/don't like.I'm sure Google might turn out a few graphs though if you do a little searching. Also are you pro or against a remapped vehicle?
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