Using smaller wheels when towing?

[anko]

For me ... the ideal solution would be to force serial mode before SOC go to critical level ... charge up to 50% SOC ... and then back in parallel mode till 30% SOC

You do not care about staying on topic, do you :lol:

I guess you cannot have what you want, as the car will not allow you to do it. But what if you could increase (or better maintain) SOC without dropping out of serial mode? For example ... by installing smaller tires? That would be much more comfortable to the ears AND more efficient as it does not require serial mode :idea:

 

[zzcoopej]

You know the RPM of the ICE for any given speed, and the standard power curve. Can't you predict the result of shifting the sweet spot by 5%?
Do you feel the ICE is operating that far from its design efficiency sweet spot just due to towing being 10km/h lower speed than no towing?

 

[anko]

You know the RPM of the ICE for any given speed, and the standard power curve. Can't you predict the result of shifting the sweet spot by 5%?

I don't think I can shift the sweet spot. All I can do (in theory, that is) is increase the RPMs for a given speed (normally, you get 37 km/h per 1000 RPM). If I was able to increase the RPMs by 5%, hopefully the available power would also increase by 5%: I have come to the conclusion that the car aims at 'producing 75% of available torque'. When it does so at 5% higher RPMs and the torque curve was flat. the power will be 5% more. But the torque curve is not flat. Torque increases with increasing RPM, peaking at (almost) 4500 RPM. So, the gain might be even a little bit more than 5%. My guess is that 5% might be enough to prevent SOC from dropping. And if it cannot totally prevent it, it might slow it down to an extend where it is no longer an issue.

Do you feel the ICE is operating that far from its design efficiency sweet spot just due to towing being 10km/h lower speed than no towing?

Not sure the sweet spot has much to do with it, other than the car's desire to operate at 75% load. The 'smaller wheel' thought is about maximising power output, rather than optimising fuel efficiency (although I think one might lead to another, buy preventing serial hybrid mode at motorway speeds).

 

[elm70]

Pushing some numbers:

Most common tyres on PHEV are : 225/55R18 tyres and 18" x 7.0J alloy wheels

Basic Tyres on some version are: 215/70R16 tyres and 16" x 6.5J alloy wheels

Both are around ~70.5cm in diameter ... aiming for -5% ... new diameter is ~67cm

Keeping the standard R18 .. you can look for a 225/45 R18 tyres

Moving to the R16 rim .. you can look for 215/60 R16

From comfort point of view, R16 looks a better option .. also 215 / 225 should help a bit on better efficiency

Car will lose less then 2cm in ground clearance ... not a big change

PS: You can crunch number easily using this web site: https://tiresize.com/calculator/

 

[anko]

From comfort point of view, R16 looks a better option .. also 215 / 225 should help a bit on better efficiency

Agreed. Probably a lot cheaper, too :idea:

 

[Trex]

Hi anko,

Was fixing up the downloads of images and saw this graph again,



and noticed the "hump" in the redline of torque around 90kph.

Would travelling a bit slower (less drag) at around that speed help in your case to keep your battery charged up? Or is it still not enough output from the generator or just too dangerous to travel at that speed ie too slow over there on your motorways these days?

Back in the 80s I travelled around a bit of Europe and Great Britain with a Ford (petrol) transit camper van, on a mainly surfing holiday, and for fuel economy reason had to travel at a max of 90kph everywhere (would have run out of money otherwise) and did not piss too many people off I think from memory (pulled over and let them pass on narrow roads), as tourists did not want to upset the locals, but may be different or illegal now.

Regards Trex.

 

[Harald]

Hi anko,
Was fixing up the downloads of images and saw this graph again,...
Regards Trex.

Hi Trex,

thanks for sharing this graph. I was searching for such a picture for a while but couldn't find one.

Travelling at approx. 90 km/h shouldn't be a dangerous style and should also not disturb anybody.
This would mean to adapt to the speed of the trucks and to glide together with them. No truck driver should be unhappy as long as he is not slowed down by this PHEV in front. The energy consumption would be more than 5% better in this case, when dragging a high load on a trailer. When having the ACC cruise control, it even wouldn't be nasty to drive.

Best regards, Harald

 

[greendwarf]

Last sentence - above 65kph additional power demand e.g. when "flooring it", comes from the electric motors.

This would suggest that if there is battery available then there would be no delay in providing the power needed - and this is certainly my experience when overtaking at speed. But would this happen if in Save or only Charge mode?

 

[anko]

Last sentence - above 65kph additional power demand e.g. when "flooring it", comes from the electric motors.

This would suggest that if there is battery available then there would be no delay in providing the power needed - and this is certainly my experience when overtaking at speed. But would this happen if in Save or only Charge mode?

When you do not need more than 60 kW for acceleration, sure. When you do need more, there are two possibilities:

ICE already doing most of the work before flooring it (save or charge mode): acceleration should be fast.
E-Motors doing all the work: you need to wait for the ICE to spin up.

Above 120-ish km/h, the first is always the case.

 

[anko]

Would travelling a bit slower (less drag) at around that speed help in your case to keep your battery charged up? Or is it still not enough output from the generator or just too dangerous to travel at that speed ie too slow over there on your motorways these days?

As a matter of fact, there was a guy in the Netherlands who towed a trailer professionally on a daily basis. He was very unhappy with the car, and asked Mitsu how they could claim the PHEV could handle a towing weight of to 1500 kg. They said: "We never said how well it would do that. Best you do not go over 80". The nerves :evil:

80 is to slow. But I am afraid 90 is not slow enough. I am usually traveling at 95-ish. Yes, less drag at that speed, but also less torque. (the curve may show a hump, but it is still uphill all the time)