Torque figure quoted as a range?
Discussion
I can't figure this out and im not getting much from Google probably because I just don't really know how to ask the question.
I understand some cars might say for example 170BHP@6,000RPM and 200 pound foot torque BETWEEN 2,800 and 4,000 RPM (these are just made up figures as an example). I usually see this all the time, especially these days on force inducted engine's. Makes perfect sense to me with forced induction.
Why would a naturally aspirated petrol engine give a between range I've not seen it before??? I'm used to all naturally aspirated petrols quoting their peak torque at a single RPM figure never a spread.
I've just been given a Mercedes W169 with the M266E15 engine. It's a 1.5 litre slant 4 with 94BHP at 5200RPM (God help me
) but quotes itself as having a torque output of 103 pound feet BETWEEN 3500-4000RPM, suggesting that it can maintain it's peak torque for 500RPM rather than reaching a peak and declining instantly. It's a SOHC 8v engine designed with low speed high gear work in mind so I'm guessing it's designed to be this way but I've just never seen it quoted as a range on an N/A petrol and I'm curious as to how this can occur??
I've come from a Honda so I'm used to my horsepower and torque figures being in very different places and with very differing numbers
I understand some cars might say for example 170BHP@6,000RPM and 200 pound foot torque BETWEEN 2,800 and 4,000 RPM (these are just made up figures as an example). I usually see this all the time, especially these days on force inducted engine's. Makes perfect sense to me with forced induction.
Why would a naturally aspirated petrol engine give a between range I've not seen it before??? I'm used to all naturally aspirated petrols quoting their peak torque at a single RPM figure never a spread.
I've just been given a Mercedes W169 with the M266E15 engine. It's a 1.5 litre slant 4 with 94BHP at 5200RPM (God help me
) but quotes itself as having a torque output of 103 pound feet BETWEEN 3500-4000RPM, suggesting that it can maintain it's peak torque for 500RPM rather than reaching a peak and declining instantly. It's a SOHC 8v engine designed with low speed high gear work in mind so I'm guessing it's designed to be this way but I've just never seen it quoted as a range on an N/A petrol and I'm curious as to how this can occur??I've come from a Honda so I'm used to my horsepower and torque figures being in very different places and with very differing numbers
Often a manufacturer will design and tune an engine to have as flat a torque curve in the most used rev range. This makes for a much nicer road car.
When turbocharged engines started to be commonplace, customers became used to having useful torque available at any time, so the few non-boosted engines have to try to replicate this.
The American V8s went about it a different way, obviously. Big lazy V8s tend to have enough torque available at any RPM and that makes for a very relaxing drive. Well worth it over a tuned engine that then has a curve climbing from say 2,000-5,000 rpm, with little below that.
Electric motors are on a different planet for torque!
When turbocharged engines started to be commonplace, customers became used to having useful torque available at any time, so the few non-boosted engines have to try to replicate this.
The American V8s went about it a different way, obviously. Big lazy V8s tend to have enough torque available at any RPM and that makes for a very relaxing drive. Well worth it over a tuned engine that then has a curve climbing from say 2,000-5,000 rpm, with little below that.
Electric motors are on a different planet for torque!
GreenV8S said:
That is making the point that the engine produces that torque over a broad rev range - it is not the peak figure. Some highly tuned engines produce impressive peak figures but only over a narrow rev range, and that makes them miserable to drive.
So technically your saying it probably gets to that figure and DOES indeed fall away from it but much more slowly than an average motor? So it's technically a lie or at least an exaggeration of the truth?I must honestly disagree with you though, as someone used to driving Honda's I adore a revvy engine focused on peak power. Obviously no good in this day and age with economy and emissions but I find them the polar opposite to miserable. I would usually find that type of engine VERY tiring with an autobox which is all I've been used to for so many years but Honda autos are based on manual boxes which takes the pain away.
My first car was a pushrod motor that made its peak power so low down, redlined at near diesel levels so I guess I just rebelled against it. As someone in his 30s I do now appreciate general low down grunt though. The Mercedes is surprising though, the redline is 1000rpm past the peak power output and I expected it to be wheezy and resistant but it actually seems to like a wringing out though. Probably just makes me feel better because it's as fast as molasses in January
hedges88 said:
GreenV8S said:
That is making the point that the engine produces that torque over a broad rev range - it is not the peak figure. Some highly tuned engines produce impressive peak figures but only over a narrow rev range, and that makes them miserable to drive.
So technically your saying it probably gets to that figure and DOES indeed fall away from it but much more slowly than an average motor? So it's technically a lie or at least an exaggeration of the truth?They have therefore (semi) arbitrarily chosen 2 points between which it generates the torque figure (or more) stated.
Modern engines have so many adjustable inputs or parameters it is entirely possible to hold a steady torque figure over a broad RPM range.
As is quite often the case here there is a misunderstanding or lack of knowledge of how accurate something is or indeed needs to be.
Once you've got your head around that it becomes much clearer.
As is quite often the case here there is a misunderstanding or lack of knowledge of how accurate something is or indeed needs to be.
Once you've got your head around that it becomes much clearer.
hedges88 said:
I must honestly disagree with you though, as someone used to driving Honda's I adore a revvy engine focused on peak power.
If you compare two engines producing similar peak power, with one that produces that peak in the top 10% of the rev range and the other producing it throughout the middle third of the rev range, the second one will be much easier to drive fast and usually give much better performance. Having a narrow power band is a disadvantage. Having a broader power band is an advantage that manufacturers sometimes like to brag about. GreenV8S said:
If you compare two engines producing similar peak power, with one that produces that peak in the top 10% of the rev range and the other producing it throughout the middle third of the rev range, the second one will be much easier to drive fast and usually give much better performance. Having a narrow power band is a disadvantage. Having a broader power band is an advantage that manufacturers sometimes like to brag about.
I completely agree, however as someone who enjoys driving and the sensation of driving, the sounds and feedback etc, ie a petrol head like a lot of us on here I just adore a revvy motor. Particularly if it's small and pretty underpowered so you can actually have fun wringing it's neck at speeds suitable for the road. Electric motors, turbo petrols and especially diesels are happy to break traction at a moment's notice whereas with a peaky motor you can just really get some precision going even without some newfangled trick diff. One situation you wouldn't be at a disadvantage is if you pair a motor like that with a CVT, to think they even tested formula one cars like that 
GreenV8S said:
If you compare two engines producing similar peak power, with one that produces that peak in the top 10% of the rev range and the other producing it throughout the middle third of the rev range, the second one will be much easier to drive fast and usually give much better performance. Having a narrow power band is a disadvantage. Having a broader power band is an advantage that manufacturers sometimes like to brag about.
When Rover Group introduced the hundred-horsepower 1.4 litre K series engine, they conformed with the standards of the day and quoted peak torque in their normal publicity. However there was a sales leaflet which included a torque v. r.p.m. graph which showed a pretty-well level character from 2,000 to 4,000 (figures from memory so accuracy not guaranteed) and it was indeed a delight to drive.bmwmike said:
A flat torque curve with high max revs makes a good engine to drive IMO. I don't get all the fuss with diesels for that reason.
Well, I’m sure you don’t really need anyone to tell you that for a commute car on busy roads, a 200bhp 500Nm turbo diesel is a very easy and economical car to drive. I’d hate to do 30k miles per year around the M25 with a VTEC! Very little joy. No, I doubt many would choose the diesel for a Sunday morning blast 
Tony1963 said:
bmwmike said:
A flat torque curve with high max revs makes a good engine to drive IMO. I don't get all the fuss with diesels for that reason.
Well, I’m sure you don’t really need anyone to tell you that for a commute car on busy roads, a 200bhp 500Nm turbo diesel is a very easy and economical car to drive. I’d hate to do 30k miles per year around the M25 with a VTEC! Very little joy. No, I doubt many would choose the diesel for a Sunday morning blast Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff