Daox's 2004 Toyota Prius Build Thread

[Daox]

I did try Bob's technique on the way home from work the other day. It seemed to work well and I also noticed what orange4boy noted, you need to go to neutral to hit the low idle. This should help my commute a bit. The first 5 minute segment is always so low, and my trip is always less than 15 minutes, so those first 5 have a huge impact on my mileage.

[groar]

Tim, as you are now the main Prius driver, you may register it in Team Toyota to motivate yourself. You should do better than its average of 42mpg and permit the Toyota to beat the Audi in the Team Competition

Have fun,

Denis.

[bwilson4web]

Perhaps this graph can explain what I was posting about:



All low MAF values are coasting in "N". Obviously, I could have been a little more fuel efficient but I'm not quite that anal. <grins>

Bob Wilson

[Daox]

Lately, I've been working on evaluating the condition of my PHEV kit's battery pack. More info on that over here.

The main reason for this post is because earlier this week I ordered the parts required to make an arduino automatic coolant temp hack. Its a device that tricks the car into thinking its warm before it actually is. This in turn allows you to get into S4 faster, and do more engine off coasting. It will be especially handy in cold weather where the engine temperature can fluxuate like crazy and the engine stays on unless you're above ~155F. With the PHEV kit working and more engine off driving being done this will augment the PHEV too.

In the past I had been hesitant to try this modification even with bwilson's nice analysis that it in fact doesn't create more emissions. I himmed and hawed over it for a while. The final straw was to hear that the 2014 PHEV Prius uses the engine for hard acceleration, and shuts off as soon as the extra power is no longer required. There is no warm up time or anything, just on/off. Hearing that finally convinced me that there is no downside to this mod. Let me engine off as soon as possible and I'll save gas and emissions.

[Daox]

I got my parts the other night and decided to build my version of TheForce's arduino temp hack. I'm using a RBBB (really bare bones board) from moderndevice.com, and a shield of my own making. Its a nice very small unit. I love the RBBBs (and they're cheap)!

Anyway, here are the pics. I still don't have the switch or LEDs mounted yet. I'm going to scrounge those parts off something I have laying around.

Arduino on the left, temp hack shield on the right.




Here is the other side of the shield.




And here it is assembled.

[MetroMPG]

I remember seeing a simple version of this hack on teamswift.net - to trick the Metro ECU into thinking the engine was warmer than it was so the length of the fuel enrichment mode was shortened after a cold start.

[bwilson4web]

It works much better with the NHW11 since the NHW20 has a more modern set of warm-up control laws.

Bob Wilson

[Daox]

I wasn't aware that the warm up cycles were different on the two cars. Thanks Bob.

I still think it'll be very useful in winter time, especially with the addition of the PHEV to allow more electric only / engine off time.

[bwilson4web]

Originally Posted by Daox

I wasn't aware that the warm up cycles were different on the two cars. Thanks Bob.

The real thanks go to Ken@Japan who shared his NHW20 data.

Originally Posted by Daox

I still think it'll be very useful in winter time, especially with the addition of the PHEV to allow more electric only / engine off time.

I have to admit I'm conflicted about this:

• slow speed, "N" gliding warm-up
• 30-40 seconds of cold-start, EV boost
• engine compartment air inlet blocks (aka., radiator blocks)
• block and transaxle heater effects

I live in the Tennessee valley and we don't have as much cold and windy weather as others. Yet I can appreciate that those who live further north need every advantage. But for my commuting car, I really don't do much beyond the radiator block unless the temperatures are below 35F.

Bob Wilson

[Daox]

Below 35F! Thats almost half the year for me!

Anyway, I finished up the temperature hack shield this morning. I did make a small change to the schematic. To reduce the amount of resistors needed I put just one 560 ohm resistor before all of the resistors.

I also changed the code a tiny bit. I swapped some pins on the arduino to digital pot so it would be easier to wire up the shield.





Here is the finished board on the arduino.