Honda F1 project leader Yusuke Hasegawa has outlined a number of reasons why Honda has been struggling so badly in the beginning of the 2017 Formula One season. He confirmed that lots of problems were not discovered while running on the dynamo meter.
More efficient combustion means less heat for the turbine, less heat for the turbine, less energy to potentially harvest. Less energy to harvest means less ERS deployment, less ERS deployment means less power.
I think that more efficient combustion does not neccessarily means less heat for turbine, more efficient combution might also means extracting more heat from a given fuel so higher pressure of combustion product to move piston and also as for turbine.
In a case that exhaust valves remain closed for a longer period during expansion stage then u have more efficiency and less remaining exhaust gas pressure for turbine which I don't think this is used for these high revving engines as u know in high revolution it's better to open exhaust valve earlier to have a longer exhaust duration.
There are indeed different ways to achieve more thermal efficiency.
Efficiency in its simplest form means how much energy (heat) are you extracting from what you put in. So without knowing how they got there it's very difficult to know if there will be more or less turbine energy available. There could very easily be more energy available to drive the turbine. Something to think about.
While on the talk of efficiency here's a fantastic video from the NASCAR world that directly relates to this discussion.
If you haven't seen it before it's well worth the 45 minutes or so to watch it.
[quote=MrPotatoHead][quote=amho]
I think that more efficient combustion does not neccessarily means less heat for turbine, more efficient combution might also means extracting more heat from a given fuel so higher pressure of combustion product to move piston and also as for turbine.
In a case that exhaust valves remain closed for a longer period during expansion stage then u have more efficiency and less remaining exhaust gas pressure for turbine which I don't think this is used for these high revving engines as u know in high revolution it's better to open exhaust valve earlier to have a longer exhaust duration.[/quote]
........So without knowing how they got there it's very difficult to know if there will be more or less turbine energy available. There could very easily be more energy available to drive the turbine. Something to think about. .....[/quote]
(TJI or similar meaning combusting efficiently a leaner mixture than could otherwise be combusted efficiently)
ie more air and so lower peak temperature so less energy thrown away to coolant so more energy in-cylinder for expansion
but the boost and exhaust pressures will be higher so the exhaust valves won't be opened later
exhaust temperature is lower but the greater expansion ratio across the turbine is surely quite helpful
Last edited by Tommy Cookers on 13 May 2017, 14:48, edited 2 times in total.
Tommy you are on the right track in your thinking.
Remember these engines are fuel flow limited. So they are all going to use the same amount of fuel - but if you can run leaner then you have more air volume for the same fuel - thus more volume coming out of the exhaust valves.
And you are correct - if you reject less energy though heat loss then you will
Make more power and be more thermal efficient and also have more heat energy going out the exhaust.
The above is overly simplified of course.
As far as valve event timing on a turbo engine I think you'll find they have a lot lower overlap and this duration than the NA engines that preceded them. You don't / can't rely on exhaust scavenging to help you like on an NA engine.
well running little overlap allows more true back pressure (a -dP) without affecting in-cylinder conditions via internal EGR
that would boost recovery at some cost in ICE power
and all the similar 'heat dilution' engines in test and service seem to use about 0.5 bar true back pressure (but don't do recovery)
wouldn't we like to know boost and valve timings !
well running little overlap allows more true back pressure (a -dP) without affecting in-cylinder conditions via internal EGR
that would boost recovery at some cost in ICE power
and all the similar 'heat dilution' engines in test and service seem to use about 0.5 bar true back pressure (but don't do recovery)
wouldn't we like to know boost and valve timings !
Absolutely. The dynamics of a boosted engine are complex to say the least. Adding in ERS raises that complexity by an order of magnitude.
I could probably find out the numbers but even if I did I wouldn't be allowed to post them here. So we will have to stick to speculation and guesswork