Laboratory figures TC. On-road figures will be higher. That's VAG ownership for you....
The quest for fuel efficiency removes any desire to run beyond the speed of Tmax (providing the 'torque back-up' that used to make for 'flexibility') with 4Ts. Thus the flexibility has to be with the transmission's keenness to drop ratios in response to demands from a driver's right foot.Tommy Cookers wrote: ↑Sat Sep 09, 2017 2:13 pm
for road driving we need a torque curve consistently rising or flat (at least not falling) over most of the speed range
because only this will allow a consistent response to the right foot action (or inaction) that we call driving
eg where hills and/or headwinds appear, the right foot demands an instant and seamless torque increase
we might by borrowing an aviation analogy see this consistent torque curve as essential to 'speed stability'
the traditional rising torque curve at the low speeds and falling torque curve at the higher speeds giving easier and better control of speed
I'm not convinced passive CVTs do actually suffer from driven pulley over-clamping, that particular issue being put to bed with the advent of torque sensitive driven pulleys.Tommy Cookers wrote: ↑Sat Sep 09, 2017 2:13 pmeven a CVT would without intelligence be less than satisfactory dealing with an inconsistent torque curve
though the undesirable driven pulley over-clamping in the simple CVT helps to stabilise its behaviour and so satisfy the user
improving the simple CVT is not easy for this reason
I think Manolis' claims of over-clamping as a cause of friction relate to the "cheap" moped CVT market.Pinger wrote: ↑Sun Sep 10, 2017 11:34 amI'm not convinced passive CVTs do actually suffer from driven pulley over-clamping, that particular issue being put to bed with the advent of torque sensitive driven pulleys.
What is obvious though is that the efficiency peaks at the 1:1 ratio - where the keen eye will observe that the radius of each sheave (as the belt sees it) is identical. It is moving to lower or higher ratios and incurring a smaller radius on one sheave and thus forcing more bending on the belt that drops the efficiency. Until the evidence appears to support over clamping as the the cause, I'll run with the above as the true cause of inefficiency in the higher ratios.
and since real world vehicles spend most of their time at part throttle, gains in this mode will have the most effect on overall fuel economy.Tommy Cookers wrote: ↑Mon Sep 11, 2017 12:39 pmbut the power loss/belt heating is no greater at these low efficiencies than at the high efficiency end (because that's high power)
reduced clamping will best benefit fuel consumption only where in cruise the engine is unthrottled or slightly throttled
so might be considered an alternative to a conventional design of greater ratio range and bulk ?
IC engines are far too nuanced in their operation Manolis for that approach to work. Read The High Speed Combustion Engine by Sir Harry Ricardo (periodically reprinted, possibly available as 'net download, expensive second hand) and give yourself a grounding in the essentials. You bring fresh thinking but the practicalities need to be understood as a whole. THSCE can provide you with this. From there, who knows what you may come up with.
Relying on memory as opposed to digging out my Aaen book.... sufficient to stop shredding belts at low power outputs. Again from memory, I think the limit was circa 30hp without the belt being destroyed in short order. The Aaen book has the details.
Unlikely. Your general point is correct but for zero consumption benefit you need the following scenarioTommy Cookers wrote: ↑Wed Sep 13, 2017 4:59 pmreducing transmission power loss by eg 10% of engine power ......
will only reduce fuel consumption by 10% if bte does not fall with the corresponding reduction in engine power demanded, bte will fall with reduced power due to increased throttling and eg if bte falls by 10% of 'original' bte then there will be no fuel consumption benefit (likely with high power engines)
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