DIY automatic start/stop - Fuel Economy, Hypermiling, EcoModding News and Forum

Daox · 03-10-2011, 02:30 PM

So, my wife has taken over my car (the Paseo), and I am now driving the Prius. She doesn't P&G at all. So, I think a little help from an arduino will help out the mileage. It should be pretty easy to come up with some simple logic to allow automatic start/stop.

The system would work kind of like Honda's IMA system. Put it in neutral and the engine shuts down. Put it back in gear and it starts up. The arduino will use the crankshaft position sensor to verify if the engine is running or not. Switches will need to be added to tell the arduino if the car is in gear or not. So, other than some wiring and adding switches to the shifter, the mod shouldn't be incredibly involved.

I know others have thought of this, but a quick search found nothing on it. Anyway, as usual I'm just using EM as a sounding board for some feedback and ideas. I actually have the code for the arduino written already. I just need to figure out the wiring and necessary relays.

fjasper · 03-10-2011, 03:22 PM

Tangential, but do you plan to use a vacuum reservoir for braking?

Daox · 03-10-2011, 03:32 PM

Good question. No, I had not planned on it. The brake booster on this car provides 3 good pumps on the brake pedal before assist is gone. This has always been enough when I've driven the car even in pretty bad stop and go.

Piwoslaw · 03-10-2011, 04:28 PM

I can't wait to see this done!

Make sure the battery is healthy - The starter will be worked more often than when you drive yourself, for two reasons. First, there are times when you don't turn the engine off, but the Arduino will, maybe because it doesn't know that the light will be green again in 2 seconds. Second, in a few cases you would bump start when the Arduino would use the starter.

BTW: Will the Arduino kill the engine only when the car is stopped, or does 'neutral-->stop' not take vehicle speed into account?
Oh, and I'm sure that it must be in neutral for some minimum number of seconds before the engine gets killed, or maybe 'gear in neutral' plus 'foot off clutch' is enough?

Arragonis · 03-10-2011, 04:45 PM

Going to watch this with interest as I would like a stop/start. I had a short 'go' in a 2010 Insight and the engine stop only seemed to work when the car was stopped and the driver keeps the brake pedal pressed. Are you planning something similar ?

Would an electric pump work for the brakes ?

Daox · 03-10-2011, 04:51 PM

The battery is quite healthy. Its a 1 year old group 24 deep cycle. It could probably crank the engine for a good half hour.

Honda's IMA only stops the engine under X speed (I'm not sure what it is, or if it differs from car to car). Mine will stop the engine any time you shift to neutral. Therefore, if you want the engine to keep running, but you want to coast with the engine on, you'd need to keep the car in gear, but push the clutch in. However, you are correct about the neutral engine stop delay. I currently have it set to two seconds. I figure thats ample time to shift and find the next gear. It may take some tweaking, but thats the current action. I'll also include a switch that shuts the unit off and reverts to normal operation since I would probably not use it a ton while driving unless it works really slick.

Daox · 03-10-2011, 04:53 PM

A vacuum pump would work for the brakes. I really don't think its necessary though. At most perhaps a larger reservoire. Its not like the car will be running in EV mode where no vacuum is available. This will probably mostly be used while coasting up to stop signs and lights. I don't know if my wife will attempt to use it to P&G.

Daox · 03-10-2011, 04:54 PM

One hiccup I do see is that the OEM starter may not be quite fast enough at starting the engine as I'd like it to be. I drove a CRZ last weekend and that engine started instantly. You put it in gear and go just like it had been idling the entire time. I'm sure this setup will not be the same. The driver will have to account manually for the lag time of the starter.

Piwoslaw · 03-10-2011, 05:03 PM

Quote:

Originally Posted by Daox

One hiccup I do see is that the OEM starter may not be quite fast enough at starting the engine as I'd like it to be. I drove a CRZ last weekend and that engine started instantly. You put it in gear and go just like it had been idling the entire time. I'm sure this setup will not be the same. The driver will have to account manually for the lag time of the starter.

A 24-42 volt starter would be a charm...

Quote:

Originally Posted by Daox

I don't know if my wife will attempt to use it to P&G.

I asked my Wife if she would use such an engine-off setup if it was available, and she answered "Yes, if I knew I could control the car when the engine is off".

Arragonis · 03-10-2011, 05:40 PM

2nd Gen Insight is CVT, engine stops when the car is stopped and the brake is on.

"Red Rage" is apparently what sitting in a queue with the brake applied is called