Taking your foot off the gas, what speed can you maintain on full assist alone? Eg can full assist maintain (if briefly) a 60mph cruise? Or even 70mph?
Trying to work out what proportion of highway driving could conceivably be provided within the 10kW electrical limit. I'm guessing quite a lot....
Clett
What you are asking is not possible. If your foot is not on the gas, and you are going 60mph, the engine will slow you down, and although the electric drive can probably keep the speed and rpm up, it is working real hard to back drive the engine that wants to be running at idle.
If the car speed with the ICE idling, is the speed you are going.(second at ~20mph), then the joystick can control the speed both faster and slower, but becomes increasing less efficient the further you pull the ICE rpm away from the idle rpm.
We call this the prius stelth mode imulator . It is fun to do, but not that efficient as the load on the electric increases as you pull the rpm up with the IMA. Another case of you really have to try it out to get a feel for it.
The Biggest problem aside from the fact that factory battery will be used up in probably a few seconds doing a full assist at those speeds .... putting that aside the biggest problem is that the engine itself will brake the car if you take your foot off the gas....
Even in 5th gear the engine will brake the car at just about anything above 40MPH ... and the faster you go the more braking action the engine will do.
10 KW of the motor on it's own would porobably be able to maintain the 60 to 70 MPH speeds for however breefly the ~500 Watts of usable power from the battery pack will last..... It is the braking action of the motor that will be the kicker and will probably not let you maintain those speeds....
But I do not have a MIMA yet ... so this would probably be best answered by sompeone with MIMA already who could try it.
But this would be very silly... and not the best use of MIMA.
Hmm... was worried that might be the case. I suppose the other way of looking at it is how much does the instant mpg go up when under full assist compared to no assist at 60mph or 70mph? Does the display even tell you?
Thinking along these lines to try to estimate likely mpgs for a future plug-in charged electric-assist version of MIMA (sorry, I realise it's a long way down the line at the moment, but I can't resist thinking about it!)
I had been guessing that if the electric-motor could provide all of the motive power to push the vehicle at 60mph, then the gas use in that situation would only arise from keeping the revs up on the engine. If the gas use for that purpose was only 6-7% of pushing the car at 60mph, then 1,000 mpg highway should be possible under electric assist!
However, given what you're saying regarding the amount of engine braking experienced at these speeds, it's likely that most of the energy in the gas is going towards keeping the engine turning (ie a lot more than 6-7%!). This in mind, I think my first estimates may have been somewhat optimistic! But 200 mpg+ should still be entirely achievable.
Clett
I think that a consistant 85- 100MPG is more likely, and the present hypermilers may get up to 110 MPG under the right conditions. Only time will tell.
Ah, with MIMA yes. I would agree that those figures (85-100mpg) are realistic, and that MIMA itself is a great step-forward over stock.
However I was talking about things to happen a good bit further in the future - using plug-in charging of additional batteries, with most of the energy coming from these and not from the gas (the whole electric-assist thing that was discussed briefly in the long thread?).
The logic behind the question was that I wanted to establish what the ceiling of possible mpg could be for a plug-in charged extra-capacity MIMA Insight, (not MIMA alone) given a notional limit of 10kW for propulsion. The only way of estimating that is to have direct control of assist, thereby determining the proportion between gas and electric use at different speeds. This is something that MIMA has only just made possible - hence my interest in the experiments.
Sorry if I'm jumping the gun again. I'm a big fan of the potential of plug-in hybrids and can't help my mind wandering to how good the Insight could be in this respect, especially given how rapid progress has been with MIMA and how close things now are to one of the first PHEVs....
Should let you get some rest before pestering you with ideas for new projects though!
Clett, I think you really should have bought a Prius
One consequence of Honda's basic design strategy is that you just aren't ever going to be able to run efficiently on electric alone, because the electric motor is bolted to the IC engine's crankshaft and is always turning the engine. If the engine isn't firing, the motor still has to do the work of overcoming the engine friction & compression.
It's a trade-off: on the upside, you avoid all the extra weight & cost of the Prius' planetary drive interconnect, plus you still get to have a manual transmission, so driving it can be fun
I think MIMA would be very efficient on both city and freeway driving, the efficiency would come from is, not having to take your foot off the gas, you could be in leanburn most of the time, every time you take your foot off the gas you lose momentum as well as the engine being used as a brake.
If you were driving up a midsize hill, and you were keeping the FCD at 125 mph, you would use assist to keep your speed, and keep the FCD at 125, you will use some of the battery charge, but on the way down you don't have to take your foot off the gas, you just keep it at 125 and the battery will charge real quick.
One consequence of Honda's basic design strategy is that you just aren't ever going to be able to run efficiently on electric alone, because the electric motor is bolted to the IC engine's crankshaft and is always turning the engine. If the engine isn't firing, the motor still has to do the work of overcoming the engine friction & compression.
Exactly! The current Honda set up can't be adapted to normal plug-in hybrid operation (ie with EV mode for the first 'x' miles, then gas use after) but it COULD be adapted to have electric assist of the gas engine (ie the gas engine is on and contributing at all times, but while there is charge in the pack, much, much less gas is used than normal - I reckon about a quarter normal gas consumption, or 4 times the normal mpg under this setup).
Why do I think it's still worth thinking about? Because currently the chances of Honda developing a plug-in hybrid are extremely slim. The problem is that there is zero chance of Honda ever signing a technology share agreement with their mortal enemy Toyota to use a power-split device allowing EV propulsion independently of the gas engine (the hatred between the two companies is unparalleled!). So, it appears that the PHEV route is difficult for Honda to take with the IMA system.
However, if we could demonstrate that electric-assist gives stellar mpg results by adapting one of the MIMA cars to plug-in charging, it could help nudge Honda in the direction of offering it as a factory-fit option to IMA buyers. And I for one would pay money for that!
But of course I realise that this is a project for the future, and we should be thankful that MIMA is on its way. So will keep my futuristic thoughts to myself for now!
CLet, on a long trip it is more efficient to use up the battery energy slowly, lets say over a period of a couple of hours or more. This is because the motor and the batteries loose less energy to resistive heating. There is really no advantage of using up the entire charge in the first half hour and then using pure gasoline power. A system like Prius only has an advantage on short runs around town where you can run mainly on electricity. If you are just doing short runs to work and back daily, then you are never going to pay back the 10,000 dollars worth of batteries that they put into a Prius at Tour de Sol.
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Kip Munro
The laws of physics don't need changing, but rather our attitude and values. 72.8 LMPG
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Question for MIMA users
