Spoofing a Prius (1st gen) brake pressure sensor for stronger regen: AutoSpeed

[MetroMPG]

Julian has posted another quality article at AutoSpeed just now:

A World First: Modifying Regen Braking

we modify the regenerative braking capability on a Toyota Prius to give greater braking capability in light braking applications. It’s a mod that needed no brake fluid, no rags, created no brake dust and yet makes a major difference to how the car brakes!

(I'm not sure it's a world first - does MIMA on the 1st gen Insight give the driver control over regen strength, or only whether or not it occurs?)

He accomplishes the feat by adding voltage to the sensor, but only when the brake pedal is pressed (activating a relay in the circuit).

The result is a loss of the ability to do extremely light braking, but he's happy with the heightened amount of regen in his braking mix.

Full article here

[jamesqf]

Originally Posted by MetroMPG

...does MIMA on the 1st gen Insight give the driver control over regen strength, or only whether or not it occurs?

MIMA gives essentially full control over both assist and regen. There are some limits: the max rates are still limited by the battery management, so you e.g. can't do full regen if it'd stress the batteries, but within that, yes. You can for instance put the car in neutral, and stall the engine, or rev it to several thousand RPM, just with the joystick.

[orange4boy]

Thanks Darin. I saw that article too. It's on my list of to do's.

He's done a bunch of cool things with that NHW10 like rear discs from a Corolla, the undertray. He turbocharged it!!1!. Yes, you read that right... a turbocharged Prius. He put in an oversize rear anti sway bar. Hacked the power steering electric assist for better road feel. And he gets paid to do it. Good work if you can get it.

I have my work cut out for me.

[tasdrouille]

It's an old article, but it's still interesting. I'm sad autospeed now only publishes 3 articles every 2 weeks, of which 1 or 2 are recycled, previously published articles.

[PaleMelanesian]

There are times where this is useful, but most of the time it's more efficient to avoid regen. Regen gives you back some of the energy, but the conversion losses make it less efficient. mechanical -> electrical -> chemical (battery) -> electrical -> mechanical

[tasdrouille]

Exactly, regen is useful so you don't waste everything when something does not go as planned. Since most drivers never plan anything and simply react, regen is very useful to the average driver, not so for the hypermiler.

[jamesqf]

Originally Posted by PaleMelanesian

There are times where this is useful, but most of the time it's more efficient to avoid regen.

Think of it not as avoiding regen, but as avoiding braking, and you have a point. If you need to brake, however, you're always better using regen instead of friction brakes. (If it provides sufficient slowing power, of course.)

I notice you live in Texas, where it's mostly pretty flat, and so easy to avoid braking. Live someplace where there are hills - the east slope of the Sierra Nevada, for instance - and you will quickly change your mind. There are more than a few places around here where driving without braking would lead to terminal velocities over 80 mph. That's ok on the straight runs, but there are a number that're pretty twisty, and have stop signs &c at the bottom.

[Frank Lee]

Why would he think discs are better than drums?

[tasdrouille]

Originally Posted by Frank Lee

Why would he think discs are better than drums?

Probably for the same reason he went for slotted rotors. It depends from which side of the performance spectrum you're looking at it. I think drums are better myself.

[Frank Lee]

Prius... performance spectrum...