HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
Blogs
Made by Monkeys

Auto Climate Control Is Backwards

View Comments: Oldest First|Newest First|Threaded View
<<  <  Page 3/7  >  >>
dmorgan
User Rank
Iron
just my 2 cents
dmorgan   2/23/2012 3:43:53 PM
NO RATINGS
This is just another reason why I buy domestic. My 2005 Silverado crew cab heats & cools like a champ. In South Georgia where is gets 80 in Feb. with 60% humidity and 100+in July with 100% humidity, I need something that will heat me up quick & cool the same way.

benmlee2
User Rank
Gold
Re: Climate Control
benmlee2   2/23/2012 3:46:17 PM
NO RATINGS
One reason I like Apple products is because as an engineer, I hate half baked products features just to sell.

Looks like Toyota only designed for condition with the car parked in a garage with temperature same outside as inside. Toyota definitely need to spend a couple dollars more and install an additional temperature sensor before they go full auto climate control.

For me, the only thing that needs to be auto is cycling the A/C button on and off to reach right temperature. Leave all the rest manual. However, given majority of population, might be better off auto.

Hackna
User Rank
Iron
Re: Seems right to me
Hackna   2/23/2012 4:24:08 PM
NO RATINGS
Repeatedly cooling recirc air is the quickest way to cool the cabin. (Almost all A/C systems pull-down tests are done in this mode.) Blower speeds usually start on high and step down as the cabin temp approaches the set temp, eventually settling on a lower speed. If and when to go to fresh air mode depends on the outside temp and humidity. (Note that most recirc modes do include a small percent of fresh air.) If your trip is long enough and the cabin gets cool enough you may even get compressor cycling to prevent the evaporator coil from freezing. (Ever have mist coming out of the A/C vents?)(Driving the first few minutes with the windows rolled down about 2 inches will let the hot air escape and improve your cool down time.)

If you have manual controls the first few minutes of heat up can be in recirc mode. (Say when your scraping ice or just warming the engine.) Once you start driving it should be set to fresh air to prevent breath and moisture from fogging the windows. Defrost should always be in fresh air mode with the A/C on. (The A/C will only run if the outside temp is high enough.) Some vehicles with inadequate body exhausters will fog the windows in cold weather regardless. I find cracking a window can help clear this up.

I would expect modern automatic climate controls to be well thought out and tested. The logic used has tradeoffs like every engineering endeavor.

I know some trade secrets and prefer manual HVAC controls, if available.

 

benmlee2
User Rank
Gold
Re: Seems right to me
benmlee2   2/23/2012 5:34:10 PM
NO RATINGS
Are you sure the industry pull down test does not just apply to the lab environment and not the real world. If you are pulling hot air from the cabin in recirc mode, the air will never be as cool as outside air. Consider a winter day in sunny California. Air temperature is very cool, but trapped heat inside the car is hot. Openning the window is way better than any A/C.

The only exception is if you direct cold air to the floor. Air intake for A/C is near the floor. That way, air intake gets cold air and makes it even colder. With A/C at max fan, air gets very cold. Not sure if Toyota does that.

That brings another point. Fresh air from outside has to pass thru a hot firewall before reaching cabin. On cheap cars, there is no insulation on the firewall. You end up getting warm air from outside. If the firewall is well insulated, many times, A/C is not even needed. Also, with old vent windows, A/C is rarely needed.

RICKZ28
User Rank
Platinum
Climate Control
RICKZ28   2/23/2012 5:56:46 PM
NO RATINGS
From what I read, and after thinking about it, I think the automatic system by Toyota is correct.  Toyota would be liable if an automatic HVAC system needlessly fogs the windows.

I've found the best way to cool-down the inside of a hot car in the summer is to roll down the windows, drive a mile or so to clear the hot air from inside the car.  My wife always rolls down the windows of her 2007 Acura TSX using the remote control, so it's already cooling-off inside by the time we enter the car...nice feature!  I keep my car windows cracked during hot and sunny weather to avoid the inside from getting too hot (and to help protect the leather interior).

I've also experienced fogged windows just after getting into a cold car during the winter.  I found the fastest way to clear the windows is to drive with the windows open about an inch for a mile or so, then close the windows and crank-up the heat.

Sometimes people cannot be totally comfortable all-the-time despite modern technology...so we just have to live with it!  It also takes time to cool-down or heat-up homes that had the HVAC turned off...not immediate comfort.

 

oldtimer8080
User Rank
Gold
The problem " fogging up " the matter
oldtimer8080   2/23/2012 6:16:02 PM
NO RATINGS
To avoid frosting or fogging up the windows, THE A/C MUST BE ALWAYS TURNED ON IN DEFROST MODE OR ANY COMBINATION THAT USES THE WINDSHIELD VENTS!

That is the option that gets the car company out of lawsuits for " obstructed vision " that causes accidents.

I know it looks silly on first glance, but anyone who has scraped off ice ON THE INSIDE OF THE WINDSHIELD knows why this is done.

 

The side effect of chilling air in the A/C is condensation, just look under a parked truck or car at the mall to see the pool of water underneath. I had a third party installed A/C in the motorhome that would freeze up in les than 10 minutes on a hot, humid summer day. Shutting off the A/C for the same time " defrosted " the thing....

Remember, there might be solid engineering behind some silly looking observations

bobl
User Rank
Iron
Re: Seems right to me
bobl   2/23/2012 7:03:57 PM
NO RATINGS
I still would like the opportunity to actually control the recirc function.  Sometimes there are reasons why you might not like to have outside air used.  Smells, dust, etc.  I had (note, had) a Chevy Trailblazer that would allow me to put it in recirc mode, but it would automatically reset to non-recirc mode every time I turned the A/C off and back on. 

 

I live in southern California.  It gets hot here during the summer.  Recirc would be nice to have.  My new Dodge Challenger has the same situation in that I can't control the recirc mode unless it is actually in 'cool' mode.

Tim
User Rank
Platinum
Re: Another pointless automation
Tim   2/23/2012 8:01:10 PM
NO RATINGS
Yes, I guess it was more of detents than ratchets.

Hackna
User Rank
Iron
Re: Seems right to me
Hackna   2/23/2012 8:08:09 PM
NO RATINGS
The industry tests are done both in the lab and field. 110F ambient with 140F interior soak temp and solar load, usually at idle. (This is the worst case for A/C.) The recirculated cab air cools every time it passes through the evaporator. Cooling the same air over and over again will get it down pretty low quicker than continually drawing in 110F air.

Manual system engineers will usually only test hot temp A/C pull down, cold temp windshield defrost and cold temp heat up. If it can handle those the driver can make anything in between happen.

Automatic system engineers will test a range of conditions. But there is a time and budget limit. Your winter day/hot interior condition is common enough that it should be something they account for. But then they would have to predict how cold a winter day it was and how long the interior has to heat up and how hard is the wind blowing. So they compromise and the driver wonders why the system works counter-intuitively.

Ask 10 people what comfortable is and you will get 11 answers. HVAC system engineering is an art and a science that usually doesn't please everyone.

Some of the other posts have great tricks to improve HVAC performance.

Tool_maker
User Rank
Platinum
Re: Another pointless automation
Tool_maker   2/24/2012 8:25:38 AM
NO RATINGS
Ann you are so correct. I guess I must just be old fashioned, but I prefer to be able to control things by myself. If I want to recirculate the air I will and I do not feel the need for something making the decision for me. I also prefer single function knobs and buttons. In my wife's vehicle we have an aftermarket, Sony, radio.

When I want to change the volume heaven help you if you inadvertently push it in. It then adjusts the bass, push again for treble, again and it is now balance, and the next push takes you to fade. It takes a fifth push to adjust volume and you just have to pray you do not hit a bump or you get to start the cycle all over again. I know there must be someone somewhere who thinks this is cool, but I surely do not know why.

<<  <  Page 3/7  >  >>
Partner Zone
More Blogs from Made by Monkeys
Made by Monkeys highlights products that somehow slipped by the QC cops.
Made By Monkeys highlights products that somehow slipped by the QC cops.
Made By Monkeys highlights products that somehow slipped by the QC cops.
Made By Monkeys highlights products that somehow slipped by the QC cops.
Made By Monkeys highlights products that somehow slipped by the QC cops.
Design News Webinar Series
9/25/2014 11:00 a.m. California / 2:00 p.m. New York
9/10/2014 11:00 a.m. California / 2:00 p.m. New York
7/23/2014 11:00 a.m. California / 2:00 p.m. New York
7/17/2014 11:00 a.m. California / 2:00 p.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Oct 20 - 24, How to Design & Build an Embedded Web Server: An Embedded TCP/IP Tutorial
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Next Class: October 1 - 30
Sponsored by Gates Corporation
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2014 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service