Torque produced 2000 rpm
Discussion
Not very often i ask questions (according to the mrs i think i know everything).
in these modern petrol engines (lets just talk about petrol) ,how are they getting max torque so flat so low down in the rev range.
surely full spool of the turbo still occurs at least 2500 rpm. I know that there is obvious progression in the efficiency of variable vane turbos and intake/exhaust manifolds over time.
even take most things from the 00s ,for arguments sake say a astra vxr that produces it at 2400rpm.
then compare it to a modern bmw or anything with direct injection.
who knows the science ?
in these modern petrol engines (lets just talk about petrol) ,how are they getting max torque so flat so low down in the rev range.
surely full spool of the turbo still occurs at least 2500 rpm. I know that there is obvious progression in the efficiency of variable vane turbos and intake/exhaust manifolds over time.
even take most things from the 00s ,for arguments sake say a astra vxr that produces it at 2400rpm.
then compare it to a modern bmw or anything with direct injection.
who knows the science ?
not sure how many cars use them, but Variable Inlet Vanes on turbos can help the turbo produce more of its total boost earlier. They alter the area over which the exhaust flow enters, speeding it up and also alter the angle with which it hits the blades. This gets the turbine spinning up faster, earlier and hence, you get more torque lower down. As you increase the engine speed, the vanes are altered in the other direction and this essentially widens the operational window of the turbine, meaning it doesn't tail off as early at the top end.
Again, not sure how many cars will use this technology.
Again, not sure how many cars will use this technology.
Otispunkmeyer said:
not sure how many cars use them, but Variable Inlet Vanes on turbos can help the turbo produce more of its total boost earlier. They alter the area over which the exhaust flow enters, speeding it up and also alter the angle with which it hits the blades. This gets the turbine spinning up faster, earlier and hence, you get more torque lower down. As you increase the engine speed, the vanes are altered in the other direction and this essentially widens the operational window of the turbine, meaning it doesn't tail off as early at the top end.
Again, not sure how many cars will use this technology.
Damn...you really have to respect the engineers for thinking of stuff like that. It seems so obvious now but it must have taken quite a bit of work to come up with an idea like it.Again, not sure how many cars will use this technology.
Otispunkmeyer said:
not sure how many cars use them, but Variable Inlet Vanes on turbos can help the turbo produce more of its total boost earlier. They alter the area over which the exhaust flow enters, speeding it up and also alter the angle with which it hits the blades. This gets the turbine spinning up faster, earlier and hence, you get more torque lower down. As you increase the engine speed, the vanes are altered in the other direction and this essentially widens the operational window of the turbine, meaning it doesn't tail off as early at the top end.
Again, not sure how many cars will use this technology.
Also these 'flat' torque curves are done by the limiting output torque (therefore input torque) of the transmission. So they appear to be producing the same torque all the time but it's actually limited by the fueling.Again, not sure how many cars will use this technology.
A lot is smoke an mirrors.
It's easy to have a vehicle that can make a lot more torque, then simply peg it back with electrics to produce a flat torque curve.
And while modern variable this and that is superb, don't forget many modern turbo setups simply don't rev as well as old ones. The Focus ST (5 pot) is a good example, loads of low down grunt, but noses over badly at high rpm.
It's easy to have a vehicle that can make a lot more torque, then simply peg it back with electrics to produce a flat torque curve.
And while modern variable this and that is superb, don't forget many modern turbo setups simply don't rev as well as old ones. The Focus ST (5 pot) is a good example, loads of low down grunt, but noses over badly at high rpm.
300bhp/ton said:
A lot is smoke an mirrors.
It's easy to have a vehicle that can make a lot more torque, then simply peg it back with electrics to produce a flat torque curve.
And while modern variable this and that is superb, don't forget many modern turbo setups simply don't rev as well as old ones. The Focus ST (5 pot) is a good example, loads of low down grunt, but noses over badly at high rpm.
I am not concerned on how they reduce it so much, i knew it would be fuel limited but more on how its produced.It's easy to have a vehicle that can make a lot more torque, then simply peg it back with electrics to produce a flat torque curve.
And while modern variable this and that is superb, don't forget many modern turbo setups simply don't rev as well as old ones. The Focus ST (5 pot) is a good example, loads of low down grunt, but noses over badly at high rpm.
i have no examples here as it wouldn't be fair post up random dyno charts from google of remaps.
In general from what ive seen over the years ,the remap only produces the more power over the mid to end of the range.
How do the OEM`s get it so low from just above idle ,if your limiting then you can produce even more surely.
pimpchez said:
I am not concerned on how they reduce it so much, i knew it would be fuel limited but more on how its produced.
i have no examples here as it wouldn't be fair post up random dyno charts from google of remaps.
In general from what ive seen over the years ,the remap only produces the more power over the mid to end of the range.
How do the OEM`s get it so low from just above idle ,if your limiting then you can produce even more surely.
I'm not sure I'd consider 2400rpm to be just above idle if I'm honest.i have no examples here as it wouldn't be fair post up random dyno charts from google of remaps.
In general from what ive seen over the years ,the remap only produces the more power over the mid to end of the range.
How do the OEM`s get it so low from just above idle ,if your limiting then you can produce even more surely.
Low end grunt isn't a new thing, my 1999 Camaro can make over 95% of it's PEAK torque by 1500rpm, yet still hold that to 4400rpm for it's actual PEAK.
A very flat torque curve, done with only an OHV engine and 2v per cylinder.
Modern multivalve engines use trick electronics and variable lots of things. But this is mostly done to allow the torque to be produced at high rpm, without all these bits the torque could still be made at low rpm. But making torque at high rpm means more power, due to:
HP = torque x rpm / 5252
With turbo motors it's even easier to get a flat torque curve over an rpm range, as you have so much control over the turbo.
Combine this with higher static CR's and smaller turbo's and varaible vane and nozzle technology, then it's easier to make significant boost at low rpm and more torque. The down side is still top end power. Many modern turbo units that make good low and mid range boost, simply can't supply the air flow at high rpm. The BMW 335i is an example of this, as is the Foscus ST MK2.
The fundamental differences in a modern turbo engine compared to a "classic" one (i.e Cosworth YB etc)
1) Dual variable camshaft phasing - Old engines used fixed cam timing, this meant a compromise between making good top end power, and making high torque at low speed. Modern engines run with the ability to phase both inlet and exhaust cams, often by a lot of crank degrees (~120degCA etc!)
2) Compression ratio - With modern control electronics, and the detonation supressive effects of direct fuel injection, a much high static compression ratio can be tolerated. This hugely boosts torque at all speeds, and means that a lower boost pressure is required at high speed, bringing us to:
3) Turbo size and inertia - Modern engines are much more efficient in terms of specific air consumption (better control of the charge burning, via high accuracy EMS / direct injection, and lower parasitic and frictional loses) so the peak power target can be met with a physically smaller turbocharger. This will help to push the boost threshold down the rpm curve as gas velocities in the system will be higher for any given massflow
4) Dual scroll, VGT, and close coupled exhaust manifold design - The boost threshold is highly dependent upon pressure "pulse" charging at lower engine speeds, usefully capturing those pressure waves and using them to speed up the turbine is critical for boost threshold. Using dual scroll turbines (2 cyls paired and separated into the turbine entry, using small, short, low thermal inertia exhaust manifolds, and in some cases (not many due to cost) moving to a variable geometry turbine system.
5) Turbo charger efficiency - huge gains have been made in the efficiency of the turbocharger unit themselves. These efficiency gains make massive differences to the boost threshold speed as in this area the massive positive "gain" of the system quickly spools the turbocharger. These gains have comne from better, more optimised design of the compressor and turbine aerodynamics, lower thermal inertia, and improved blade clearances due to better bearing orbit control (ball bearing turbos)
6) Clever torque based engine management systems - Modern EMS system operate way faster,and with much more accuracy. combined with electronic(as opposed to pneumatic) control of things like wastegates, the system response can be much better optimised. Tricks such as controlling pre-throttle boost rather than manifold pressure allow transient response times to be improved by orders of mangnitude when combined with advanced spark and fuelling strategies (i.e. deliberately late burn / retarded to spool up turbo etc)
1) Dual variable camshaft phasing - Old engines used fixed cam timing, this meant a compromise between making good top end power, and making high torque at low speed. Modern engines run with the ability to phase both inlet and exhaust cams, often by a lot of crank degrees (~120degCA etc!)
2) Compression ratio - With modern control electronics, and the detonation supressive effects of direct fuel injection, a much high static compression ratio can be tolerated. This hugely boosts torque at all speeds, and means that a lower boost pressure is required at high speed, bringing us to:
3) Turbo size and inertia - Modern engines are much more efficient in terms of specific air consumption (better control of the charge burning, via high accuracy EMS / direct injection, and lower parasitic and frictional loses) so the peak power target can be met with a physically smaller turbocharger. This will help to push the boost threshold down the rpm curve as gas velocities in the system will be higher for any given massflow
4) Dual scroll, VGT, and close coupled exhaust manifold design - The boost threshold is highly dependent upon pressure "pulse" charging at lower engine speeds, usefully capturing those pressure waves and using them to speed up the turbine is critical for boost threshold. Using dual scroll turbines (2 cyls paired and separated into the turbine entry, using small, short, low thermal inertia exhaust manifolds, and in some cases (not many due to cost) moving to a variable geometry turbine system.
5) Turbo charger efficiency - huge gains have been made in the efficiency of the turbocharger unit themselves. These efficiency gains make massive differences to the boost threshold speed as in this area the massive positive "gain" of the system quickly spools the turbocharger. These gains have comne from better, more optimised design of the compressor and turbine aerodynamics, lower thermal inertia, and improved blade clearances due to better bearing orbit control (ball bearing turbos)
6) Clever torque based engine management systems - Modern EMS system operate way faster,and with much more accuracy. combined with electronic(as opposed to pneumatic) control of things like wastegates, the system response can be much better optimised. Tricks such as controlling pre-throttle boost rather than manifold pressure allow transient response times to be improved by orders of mangnitude when combined with advanced spark and fuelling strategies (i.e. deliberately late burn / retarded to spool up turbo etc)
Max_Torque said:
The fundamental differences in a modern turbo engine compared to a "classic" one (i.e Cosworth YB etc)
1) Dual variable camshaft phasing - Old engines used fixed cam timing, this meant a compromise between making good top end power, and making high torque at low speed. Modern engines run with the ability to phase both inlet and exhaust cams, often by a lot of crank degrees (~120degCA etc!)
2) Compression ratio - With modern control electronics, and the detonation supressive effects of direct fuel injection, a much high static compression ratio can be tolerated. This hugely boosts torque at all speeds, and means that a lower boost pressure is required at high speed, bringing us to:
3) Turbo size and inertia - Modern engines are much more efficient in terms of specific air consumption (better control of the charge burning, via high accuracy EMS / direct injection, and lower parasitic and frictional loses) so the peak power target can be met with a physically smaller turbocharger. This will help to push the boost threshold down the rpm curve as gas velocities in the system will be higher for any given massflow
4) Dual scroll, VGT, and close coupled exhaust manifold design - The boost threshold is highly dependent upon pressure "pulse" charging at lower engine speeds, usefully capturing those pressure waves and using them to speed up the turbine is critical for boost threshold. Using dual scroll turbines (2 cyls paired and separated into the turbine entry, using small, short, low thermal inertia exhaust manifolds, and in some cases (not many due to cost) moving to a variable geometry turbine system.
5) Turbo charger efficiency - huge gains have been made in the efficiency of the turbocharger unit themselves. These efficiency gains make massive differences to the boost threshold speed as in this area the massive positive "gain" of the system quickly spools the turbocharger. These gains have comne from better, more optimised design of the compressor and turbine aerodynamics, lower thermal inertia, and improved blade clearances due to better bearing orbit control (ball bearing turbos)
6) Clever torque based engine management systems - Modern EMS system operate way faster,and with much more accuracy. combined with electronic(as opposed to pneumatic) control of things like wastegates, the system response can be much better optimised. Tricks such as controlling pre-throttle boost rather than manifold pressure allow transient response times to be improved by orders of mangnitude when combined with advanced spark and fuelling strategies (i.e. deliberately late burn / retarded to spool up turbo etc)
Thanks for this detailed answer.I suppose it makes sense that its many advances across the system that make up the overall benefits. 1) Dual variable camshaft phasing - Old engines used fixed cam timing, this meant a compromise between making good top end power, and making high torque at low speed. Modern engines run with the ability to phase both inlet and exhaust cams, often by a lot of crank degrees (~120degCA etc!)
2) Compression ratio - With modern control electronics, and the detonation supressive effects of direct fuel injection, a much high static compression ratio can be tolerated. This hugely boosts torque at all speeds, and means that a lower boost pressure is required at high speed, bringing us to:
3) Turbo size and inertia - Modern engines are much more efficient in terms of specific air consumption (better control of the charge burning, via high accuracy EMS / direct injection, and lower parasitic and frictional loses) so the peak power target can be met with a physically smaller turbocharger. This will help to push the boost threshold down the rpm curve as gas velocities in the system will be higher for any given massflow
4) Dual scroll, VGT, and close coupled exhaust manifold design - The boost threshold is highly dependent upon pressure "pulse" charging at lower engine speeds, usefully capturing those pressure waves and using them to speed up the turbine is critical for boost threshold. Using dual scroll turbines (2 cyls paired and separated into the turbine entry, using small, short, low thermal inertia exhaust manifolds, and in some cases (not many due to cost) moving to a variable geometry turbine system.
5) Turbo charger efficiency - huge gains have been made in the efficiency of the turbocharger unit themselves. These efficiency gains make massive differences to the boost threshold speed as in this area the massive positive "gain" of the system quickly spools the turbocharger. These gains have comne from better, more optimised design of the compressor and turbine aerodynamics, lower thermal inertia, and improved blade clearances due to better bearing orbit control (ball bearing turbos)
6) Clever torque based engine management systems - Modern EMS system operate way faster,and with much more accuracy. combined with electronic(as opposed to pneumatic) control of things like wastegates, the system response can be much better optimised. Tricks such as controlling pre-throttle boost rather than manifold pressure allow transient response times to be improved by orders of mangnitude when combined with advanced spark and fuelling strategies (i.e. deliberately late burn / retarded to spool up turbo etc)
edit to add , thanks to everyone that input.
this is from the forthcoming mini:
Petrol engines
Turbocharged, direct-injection three- and four-cylinder petrol engines will be offered as part of the range. The launch 1.5-litre 3-cylinder unit gets 134bhp and 162lb ft (170lb ft on overboost) from just 1250rpm. The launch 2.0-litre 4cyl unit, meanwhile, gets 189bhp and 206lb ft (221lb ft on overboost). Both engines rev to 6500rpm, with further variants planned for future release.
this is what got me thinking in the first place
Edited by pimpchez on Monday 30th September 11:57
Max_Torque said:
5) Turbo charger efficiency - huge gains have been made in the efficiency of the turbocharger unit themselves. These efficiency gains make massive differences to the boost threshold speed as in this area the massive positive "gain" of the system quickly spools the turbocharger. These gains have comne from better, more optimised design of the compressor and turbine aerodynamics, lower thermal inertia, and improved blade clearances due to better bearing orbit control (ball bearing turbos)
)
Lower thermal inertia to reduce the energy of the flow being lost to heat the turbo? That would explain the move to aluminium turbine housings. )
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