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Legal reason for ERDTT

13K views 26 replies 16 participants last post by  canehdian 
#1 ·
Hello !
Can someone tell me the official gm reason for the ERDTT ? Fog in the dash, heat assistance for driver...?
 
#2 ·
Federal regulations require that vehicles with and engine be able to clear the windshield in a given amount of time. Starting the engine makes this possible in the Volt. Those regulations do not apply to BEVs since they don't have an engine. Hence not an issue with a Tesla or a Bolt EV.
 
#4 ·
I sometimes wonder about the true reason for ERDTT.

Granted, we live in a world of tradeoffs. Maybe, to meet the required levels of defrost at cold ambient temperatures would have required an even larger electric heater in the Volt, and that may have lead to increased cost and lower EPA efficiency ratings. On those cold days, the heater would have drawn so much power that the Volt would have reduced power output (the battery can only supply so much power). People would not be happy if they had less performance on cold days.

In addition, the battery pack performs best in a temperature window of about 35 F to 78 F, IIRC. As you get outside these temperatures, you must heat or cool the battery pack. This is yet another power draw that the Volt must contend with on cold days.

My personal belief is that the GM engineers weighed all the design parameters and came up with a good compromise. The Volt is an EV is most driving scenarios, but in extreme cold temperatures, they utilize the ICE to provide cabin heat and battery pack heat. Since you have an ICE anyway, this was the best way to solve the cold temperature issues.
 
#8 ·
I sometimes wonder about the true reason for ERDTT.
... My personal belief is that the GM engineers weighed all the design parameters and came up with a good compromise. The Volt is an EV is most driving scenarios, but in extreme cold temperatures, they utilize the ICE to provide cabin heat and battery pack heat. Since you have an ICE anyway, this was the best way to solve the cold temperature issues.
I modified this fall the temp sensor so that ERDTT doesn't start unless outside temp is about -35C. I never had a problem with the heat in my car, even though we had some very low temperatures, and yes, the car was outside unplugged for more than 7 hours.
I don't really buy the GM explanation about ERDTT, because I've never seen posted why they agreed to modify the temp from -4C to -10C (Gen1 2012 vs Gen 1 2013+ and Gen 2). Why -10 C was their choice, it is a mystery to me. -18 C (0F) would have been more suitable IMHO, and I am sure many of the owners would have not modify anything on their car.

And why we have ERDTT in the Volt when the same system is used in Bolt and Spark EV. Those don't have a problem with defrosting then ?
 
#10 ·
I just discovered this morning my ELR does it at 32.


I couldn't care less. The whole crying about burning gas once in a while is crazy...Go buy a Leaf.
 
#11 · (Edited)
Unless you do a 2 miles commute every day during winter. Which is a pain from ICE point of view, because in 2 miles it doesn't warm up and it gives you about 15 mpg or less in cold weather. But you have 23-24 miles AER at your finger that you can't use. Pretty smart engineering... NOT !
 
#19 ·
I only made a distinction between you first part - Trump like - and the rest, which are more like you. And no, Trump is not as the world is. World, as far as I know, when in doubt, reads and informs itself. When mistaken, it assumes it and try to correct it. NOTHING of these I see in Trump. He knows-it-all and he is always right.
 
#20 ·
Trumps current 'car' is a Kodiak Diesel medium duty truck with a fully armored Cadillac body attached, it is about 13,000lb. It flies more miles than it is driven and gets about 5 mpg. He inherited it from the last POTUS.

Not sure if it has ERDTT, but diesels hate the cold. The fuel jells and you are stuck.
 
#22 · (Edited)
Remove the air temperature sensor, wrap the ends of a $0.10 resistor around the two terminals, ERDTT is gone. A well documented mod. Also available pre-made on eBay for about $50.

To answer the OP's question see post #2 in this thread. Beyond that, it's conjecture.
 
#24 ·
I can sympathize with those who don't like ERDTT and can drive exclusively within range of all electric, as I would not like to use any gas unless I was going further than electric range.

The primary issue is that the car simply does not know how far you are going to drive.

If the car knew that your destination was within electric range, it could potentially defer the ERDTT for those drives.

Likewise, if the car knew you are going on a longer trip, it could use ERDTT to properly warm the interior and ICE accordingly to outside conditions.

I think the biggest failure that GM did for the volt, was to not integrate navigation into the vehicle. If they had done so, and make the car smarter about your destination, it could run the ICE at the most optimal times during the trip to maximize range.

Then we would not have to micro manage things like the HOLD or MOUNTAIN modes, to save electric power for when it can be more efficiently used (ie slow/city driving instead high speed highway driving).

If the vehicle was programmed to understand your daily commute, it could optimize its systems to better match your route/traffic patterns.

In any case, there is nothing that GM is going to do change the behavior of ERDTT on your vehicle, short of a class-action or some kind of recall.

So you can either learn to love it or ignore it, or do the aforementioned mod to fix it permanently to your satisfaction.

How does the saying go?

God, grant me the serenity to accept the things I cannot change,
Courage to change the things I can,
And wisdom to know the difference.
 
#26 ·
The federal motor vehicle regulations require a certain level of defrosting performance. The Volt design needed to incorporate ERDTT to meet the standard. The regulations don't care how far your trip is, etc. You just have to meet the standard. Not sure why the Bolt can meet it, but there must be some design differences there. I don't think this is a major problem for most owners, but you can always defeat it if it is a major problem for you. Personally, I live in North Carolina and mine has not come on yet during 2 winters. If temps get below 15, I will welcome some additional cabin heat.
 
#27 ·
This is about the only chance of getting an official legal reason as to why it exists and cannot be disabled, otherwise we're not getting one if we didn't by now.
http://gm-volt.com/forum/showthread.php?110073-GM-sued-in-Canada-for-ERDTT

The only unofficial reason we've been given is above, FMVSS. But that didn't come from official channels at GM. That was given to us by WOT on these forums.
 
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