RE: Let turbos be turbos: Tell Me I'm Wrong
Discussion
Mr Whippy said:
By definition a turbo will always be noticeably laggy.
I'm intreagued to try one of theses "torque fill" hybrids to see how well they hide turbo lag. Obviously they can't completely remove it unless the electric motors produce as much power as the ICE and are only used for torque fill (which would be a daft thing to do) but I'm interested to see how good they are at fooling the driver's senses which is really what matters. kambites said:
I'm intreagued to try one of theses "torque fill" hybrids to see how well they hide turbo lag. Obviously they can't completely remove it unless the electric motors produce as much power as the ICE and are only used for torque fill (which would be a daft thing to do) but I'm interested to see how good they are at fooling the driver's senses which is really what matters.
The concept obviously works but it's not that great at fooling the driver's senses because the turbos still take time to spool up, generate power and deliver the engine noise you expect. The "shove" is instant but it isn't in sync with the engine noise which makes for a somewhat strange sensation. Many people mentioned this with the P1.Mum had an early Saab 900 turbo which was utterly fascinating. Lag became a family discussion topic at dinner. I recall Mum having to plan overtaking manoeuvres about 10mins beforehand to build enough boost to safely get past. And the whistle and thrust would induce cackles of laughter from the back seats. Quirky and charming.
kambites said:
I'm intreagued to try one of theses "torque fill" hybrids to see how well they hide turbo lag. Obviously they can't completely remove it unless the electric motors produce as much power as the ICE and are only used for torque fill (which would be a daft thing to do) but I'm interested to see how good they are at fooling the driver's senses which is really what matters.
That's why e-boosters are heading to market. It isn't an e-motor fill, it's a manifold pressure fill with a similar response rate to a crank driven supercharger.If the manifold density is there that the turbo wants to provide but is unable to, it will feel similar to an NA. Having seen some data and driven a (ropey) demonstrator, it's certainly very impressive.
zeppelin101 said:
That's why e-boosters are heading to market. It isn't an e-motor fill, it's a manifold pressure fill with a similar response rate to a crank driven supercharger.
If the manifold density is there that the turbo wants to provide but is unable to, it will feel similar to an NA. Having seen some data and driven a (ropey) demonstrator, it's certainly very impressive.
Starting to sound like something that breaks expensively and/or 'runs out'If the manifold density is there that the turbo wants to provide but is unable to, it will feel similar to an NA. Having seen some data and driven a (ropey) demonstrator, it's certainly very impressive.
Is there any reason we're not seeing decoupled turbines and compressors 'filled in' where needed by electric motors... on hybridy type stuff any way?!
Dave
I loved the old school lag "nothing nothing oh my god" feeling of my cosworth engine on a gt30 turbo. Now doing something a bit different with it, higher comp ratio and modern twin scroll turbo all in a very light package.
Be interesting to see how different it feels and if it's as much fun.
Be interesting to see how different it feels and if it's as much fun.
Mr Whippy said:
Starting to sound like something that breaks expensively and/or 'runs out'
Is there any reason we're not seeing decoupled turbines and compressors 'filled in' where needed by electric motors... on hybridy type stuff any way?!
Dave
Temperature plays a large part in a permanently decoupled compressor, the rest is electrical load.Is there any reason we're not seeing decoupled turbines and compressors 'filled in' where needed by electric motors... on hybridy type stuff any way?!
Dave
The next generation of mild hybrids (essentially an assisted ICE, rather than a petrol assisted electric drivetrain) will see a jump up in vehicle voltage to 48V which is an enabler for all sorts of technology. The trick is getting a battery pack that has suitable capacity to provide 4+kW of power for a period up until the turbocharger can take over. Obviously because the mass flow is increased via the e-booster this takes less time than it usually would, but it is still a period of time where energy needs to be used which then needs to be recovered in some way.
As with any hybridisation, the art of getting it right is in the battery pack. That is the major limitation for the implementation of some really advanced systems in terms of weight and capability.
Part of the problem with the way turbo engines are designed at the moment is marketing power. In a game of top trumps, having peak torque available 100 rpm or more earlier than your competitors is seen as an edge, because very few customers can understand something like torque rise rate against engine speed which would probably be a more objective measure for a turbocharged engine rather than a torque curve.
Edited by zeppelin101 on Monday 20th April 14:51
I enjoy driving turbocharged (petrol) engines, as long as they're not solely tuned for economy.
Since remapping mine (2.0 turbo Mondeo, from 200 to ~240-250bhp) it has introduced a bit more "old school" boost lag as well as a fair old increased dollop of torque and power, which makes it quite enjoyable to drive as well as remaining very flexible at lower revs. It still runs out of puff at about 6-6.5k but that's just because it's a relatively small turbo.
It can't beat the lovely sing-song that my old ST220 made, nor the pin sharp throttle response, but I'm a fan of both worlds really
Since remapping mine (2.0 turbo Mondeo, from 200 to ~240-250bhp) it has introduced a bit more "old school" boost lag as well as a fair old increased dollop of torque and power, which makes it quite enjoyable to drive as well as remaining very flexible at lower revs. It still runs out of puff at about 6-6.5k but that's just because it's a relatively small turbo.
It can't beat the lovely sing-song that my old ST220 made, nor the pin sharp throttle response, but I'm a fan of both worlds really
Gary C said:
s m said:
Often it is turbo stall - the sound of the compressor blades trying to "chop" through a wodge of compressed air as the throttle is closed
A recirc/dump valve allows flow to be maintained to prevent surge.The spinning assembly looses speed due to friction and work done. Work done is proportional to the mass of air moved by the compressor, and if the unit is not moving air, then it will slow less, however a dump valve maintains flow (to prevent surge) and actually contributes to reducing compressor speed.
I always thought the main purpose of a bov was to get rid of compressor surge rather than any real ability to maintain turbine speed because when the throttle is shut the turbo is starved of exhaust gas flow and will slow anyway.
zeppelin101 said:
Temperature plays a large part in a permanently decoupled compressor, the rest is electrical load.
The next generation of mild hybrids (essentially an assisted ICE, rather than a petrol assisted electric drivetrain) will see a jump up in vehicle voltage to 48V which is an enabler for all sorts of technology. The trick is getting a battery pack that has suitable capacity to provide 4+kW of power for a period up until the turbocharger can take over. Obviously because the mass flow is increased via the e-booster this takes less time than it usually would, but it is still a period of time where energy needs to be used which then needs to be recovered in some way.
As with any hybridisation, the art of getting it right is in the battery pack. That is the major limitation for the implementation of some really advanced systems in terms of weight and capability.
Part of the problem with the way turbo engines are designed at the moment is marketing power. In a game of top trumps, having peak torque available 100 rpm or more earlier than your competitors is seen as an edge, because very few customers can understand something like torque rise rate against engine speed which would probably be a more objective measure for a turbocharged engine rather than a torque curve.
I suppose that is one way to go.The next generation of mild hybrids (essentially an assisted ICE, rather than a petrol assisted electric drivetrain) will see a jump up in vehicle voltage to 48V which is an enabler for all sorts of technology. The trick is getting a battery pack that has suitable capacity to provide 4+kW of power for a period up until the turbocharger can take over. Obviously because the mass flow is increased via the e-booster this takes less time than it usually would, but it is still a period of time where energy needs to be used which then needs to be recovered in some way.
As with any hybridisation, the art of getting it right is in the battery pack. That is the major limitation for the implementation of some really advanced systems in terms of weight and capability.
Part of the problem with the way turbo engines are designed at the moment is marketing power. In a game of top trumps, having peak torque available 100 rpm or more earlier than your competitors is seen as an edge, because very few customers can understand something like torque rise rate against engine speed which would probably be a more objective measure for a turbocharged engine rather than a torque curve.
Edited by zeppelin101 on Monday 20th April 14:51
It just seems more logical to alleviate the way a turbo is always a compromise where it fits the engine. Being able to widen that envelope also gives you benefits in sustained use at varying engine load/rpm ranges, than just to alleviate the lag that a given turbo gives.
Also it still seems weird to run the engine into a drive-train directly, vs just running an engine into a generator and then have a central e-motor.
I suppose part of the issue is driver expectations. Not having a rev gauge that goes up/down with speed may be seen as 'weird'
Dave
Mr Whippy said:
It just seems more logical to alleviate the way a turbo is always a compromise where it fits the engine. Being able to widen that envelope also gives you benefits in sustained use at varying engine load/rpm ranges, than just to alleviate the lag that a given turbo gives.
These sorts of systems enable the turbo system for a transiently operating engine to be designed in a more useful way. For example, at present a turbocharger is sized such that it must achieve the peak torque condition and peak power at certain engine speeds and the resulting inefficiencies at either end must be tolerated by the charge air cooling system.Conversely, with a system using an e-booster, the turbocharger sizing is less reliant on the earliest peak torque point (depending on battery capacity etc) and can be designed to be more efficient everywhere else. This gives a few nice benefits, such as de-rate performance at altitude/increased temperature and an improvement in efficiency for the charge cooler circuit etc etc if so desired.
It's a case of reducing the importance of one requirement and reap the benefit in efficiency improvements elsewhere.
Turbocharger efficiency is already leagues ahead of where it was not so long ago now that less manufacturers are using pneumatic wastegates - this enables all sorts of improvements in general engine efficiency and fuel economy capability.
There is still a way to go to optimise efficiency in engines, hybridisation is an enabler in both directions (full electrification and traditional powertrains)
Yeah we can push efficiency, but a fixed compressor with a shaft linking it to a fixed turbine seems a huge compromise right away.
A free compressor even, would only have an ideal performance over a fairly narrow range if it were electricity driven.
Obviously it's all small steps, but some of these steps seem stupendously small in possible efficiency gains (real world, not ideal case euro cycle stuff).
I'm just surprised we haven't seen some amazing new fully e-powered compressors arrive, something that would be a generational leap, rather than a tiny jump on-top of existing tech that's somewhat limited already in outright efficiency terms.
Ie, fixing a transient to slightly better optimise for steady state.
Why not just go right in and fix the entire envelope with a great new compressor design?
Dave
A free compressor even, would only have an ideal performance over a fairly narrow range if it were electricity driven.
Obviously it's all small steps, but some of these steps seem stupendously small in possible efficiency gains (real world, not ideal case euro cycle stuff).
I'm just surprised we haven't seen some amazing new fully e-powered compressors arrive, something that would be a generational leap, rather than a tiny jump on-top of existing tech that's somewhat limited already in outright efficiency terms.
Ie, fixing a transient to slightly better optimise for steady state.
Why not just go right in and fix the entire envelope with a great new compressor design?
Dave
Mr Whippy said:
Yeah we can push efficiency, but a fixed compressor with a shaft linking it to a fixed turbine seems a huge compromise right away.
A free compressor even, would only have an ideal performance over a fairly narrow range if it were electricity driven.
Obviously it's all small steps, but some of these steps seem stupendously small in possible efficiency gains (real world, not ideal case euro cycle stuff).
I'm just surprised we haven't seen some amazing new fully e-powered compressors arrive, something that would be a generational leap, rather than a tiny jump on-top of existing tech that's somewhat limited already in outright efficiency terms.
Ie, fixing a transient to slightly better optimise for steady state.
Why not just go right in and fix the entire envelope with a great new compressor design?
Dave
Where is the energy coming from to run such a device? A free compressor even, would only have an ideal performance over a fairly narrow range if it were electricity driven.
Obviously it's all small steps, but some of these steps seem stupendously small in possible efficiency gains (real world, not ideal case euro cycle stuff).
I'm just surprised we haven't seen some amazing new fully e-powered compressors arrive, something that would be a generational leap, rather than a tiny jump on-top of existing tech that's somewhat limited already in outright efficiency terms.
Ie, fixing a transient to slightly better optimise for steady state.
Why not just go right in and fix the entire envelope with a great new compressor design?
Dave
As I said before, battery capacity/weight/size are the limiting factors in any additional electrical tech.
In actual fact, a turbocharger in it's current form is quite efficient, although the next step is moving from radial/mixed flow wheels to axial flow wheels, such as Honeywell's DualBoost:
http://turbo.honeywell.com/our-technologies/gasoli...
Nothing particularly new about axial wheel design, but there is scope for additional improvements over where the majority of turbo tech is currently.
Anything that is moving air at a pressure is going to be limited in efficiency, whether it's driven by an e-machine or exhaust enthalpy. That's basic thermodynamics. Turbochargers are not that inefficient really, peak compressor efficiencies of 72-79% and turbine efficiencies up to 75% are not that bad really. Certainly, a fully electric compressor is not going to be capable of achieving anything game changing.
Edited by zeppelin101 on Tuesday 21st April 09:22
zeppelin101 said:
Where is the energy coming from to run such a device?
As I said before, battery capacity/weight/size are the limiting factors in any additional electrical tech.
In actual fact, a turbocharger in it's current form is quite efficient, although the next step is moving from radial/mixed flow wheels to axial flow wheels, such as Honeywell's DualBoost:
http://turbo.honeywell.com/our-technologies/gasoli...
Nothing particularly new about axial wheel design, but there is scope for additional improvements over where the majority of turbo tech is currently.
Anything that is moving air at a pressure is going to be limited in efficiency, whether it's driven by an e-machine or exhaust enthalpy. That's basic thermodynamics. Turbochargers are not that inefficient really, peak compressor efficiencies of 72-79% and turbine efficiencies up to 75% are not that bad really. Certainly, a fully electric compressor is not going to be capable of achieving anything game changing.
Energy would come from brake regen, an exhaust turbine that just runs into a generator? Loads of places to get energy rather than via a fixed shaft which limits both wheels to the same speeds etc.As I said before, battery capacity/weight/size are the limiting factors in any additional electrical tech.
In actual fact, a turbocharger in it's current form is quite efficient, although the next step is moving from radial/mixed flow wheels to axial flow wheels, such as Honeywell's DualBoost:
http://turbo.honeywell.com/our-technologies/gasoli...
Nothing particularly new about axial wheel design, but there is scope for additional improvements over where the majority of turbo tech is currently.
Anything that is moving air at a pressure is going to be limited in efficiency, whether it's driven by an e-machine or exhaust enthalpy. That's basic thermodynamics. Turbochargers are not that inefficient really, peak compressor efficiencies of 72-79% and turbine efficiencies up to 75% are not that bad really. Certainly, a fully electric compressor is not going to be capable of achieving anything game changing.
Peak efficiency around 70-80% is ok, but that is peak. It'd be nice to say between 80-90% efficiency across the range with an e-machine drive axial compressor of some variety... or something totally different again?!
OK it's not been invented yet, but that is what I don't understand. Further adaptation of fixed compressor/turbine shaft designs is great and everything, but it's starting the game with a pretty fixed set of limitations it seems.
Dave
Ohhh man am I back in love with that old school big turbo feel right now. I'd forgotten what if felt like.
I've just bought an older 911 turbo with a pair of k24's hanging from the bottom and you get that wonderful feeling at low rpm of riding along on a wave of torque, before suddenly the wave breaks and it just explodes off with comically savage violence.
You can eat road and overtake anything you need without ever actually waking the turbos, it accelerates plenty fast without ever reading more than 0.1bar positive pressure. Its just nice to know that with a flex of your toe, you have the option to scream off into the distance with your body pinned into the seat and a grin from ear to ear
I've just bought an older 911 turbo with a pair of k24's hanging from the bottom and you get that wonderful feeling at low rpm of riding along on a wave of torque, before suddenly the wave breaks and it just explodes off with comically savage violence.
You can eat road and overtake anything you need without ever actually waking the turbos, it accelerates plenty fast without ever reading more than 0.1bar positive pressure. Its just nice to know that with a flex of your toe, you have the option to scream off into the distance with your body pinned into the seat and a grin from ear to ear
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