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Daox 09-28-2013 10:58 AM

Installed a coolant temp spoofer on the Prius
4 Attachment(s)
What is a coolant spoofer you might ask? Well the Prius goes through 4 warm up stages before you can get it to turn off the engine every time like you'd like to do. Most of the stages are controlled by the coolant temperature. So, this little circuit tells the ECU that the engine is warmer than it really is to get you through the warmup process quicker. Also, if you have the heat turned on in the Prius, depending on the coolant temp, it will keep your engine running or not. So, the coolant temp spoofer basically allows for more engine off operation.

The coolant spoofer I got was from ccdisce over on Priuschat. Its a custom board he designed to do the job, and he now sells them.

Here is the kit contents.

Here is the little tiny spoofer board. Its only about as wide as a quarter.

To install it you remove the glove box to access the ECU wiring behind it. You only have to hook up three wires: power, ground, coolant temp. So, its very simple. Mine was even easier because I already had the wires hooked up to wiretaps from the arduino board.

Here we go, all "installed". It'll probably stay that way just giving company to my EV switch and ipod.

I only just installed it on Thursday night (2 days ago), but I did notice on the way to work on Friday I was able to get my engine to shut off earlier than before. I'm not sure how this will translate to mpg, but at the very least I should be able to use my heater a bit more in winter and that would be quite nice.

Daox 09-30-2013 03:12 PM

On the way to work this morning I definitely could tell a difference with the spoofer in place. I was able to engine off a fair amount earlier, if I had to guess I'd estimate 1/2 mile earlier than normal.. This comes in handy for me especially since my commute is only 7 miles. My warm up time eats up my mileage pretty badly. Anything to reduce warm up helps my mileage out.

MetroMPG 09-30-2013 03:25 PM

Have other owners chimed in with how much it has affected MPG?

Obviously it'll depend a lot on individual driving/use patterns.

Daox 09-30-2013 03:35 PM

Yeah its highly driver specific. A lot of the PHEV guys like it because they dont have to worry about the engine cooling off and kicking the engine back on. I don't know about non-phev users.

redpoint5 09-30-2013 04:11 PM

Could spoofing the ECU have a detrimental affect on any engine/exhaust components?

Economy plummets on non-hybrid cars as well. I'd like to spoof my car just to keep it from running at 2,200 RPM on cold starts. At least the Prius is designed to warm up very quickly. The 3rd gen warms up in something like 50 seconds, which is much better than the 3 or so minutes my car takes.

OT, but I'm wondering if the plug in Prius can be purchased, or if they are lease only? I see people on Priuschat talking about leasing, but never purchasing. I never see any listed on Craigslist. The Toyota website is worthless. When you click on the "build a plug in Prius" link, it takes you to a page that lists the local dealers you can get in contact with.

Daox 09-30-2013 04:24 PM

The only detrimental thing I can think of is its going to mess with your ignition timing a little because it does alter the coolant temp signal that the ECU sees.

I know this spoofer is smart though. It waits until the coolant is 116F until it starts working to avoid cold engine enrichment running problems. There was also something else about a check engine light that was programmed around when I was reading the install manual which also had revision notes on it.

There is tons more info on the spoofer here:
A Prius ECT Spoofer MCU Controlled | PriusChat

The same general design could be used for any normal car though.

kurzer 12-30-2015 12:22 PM

here is my video how install and how it works.

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