Rx330 Computer Settings

[lex_luthor]

Hi,

I just got a 2004 RX330.

The manual indicates that there are lots of choices a Lexus Owner can make about various settings in the car (i.e. lights come on or not, time delays, etc.)

Is there anywhere that lists all of these settings in once place so that I can just easily look through it and give the dealer the exact changes I want to make in an easy format?

Are there any particular changes that anyone would recommend doing for sure.

Thanks!

[SeaDuck79]

I asked my dealer about that, and they handed me a list of about 3 pages. There are some changes that my wife and I will make. My dealer (this may or may not be a Lexus corporate policy) said that within 90 days of the sale, code changes were complimentary.

[wwest]

1. Have the dealer unlink the A/C operation for defog/defrost/demist functions.

2. Have the dealer unlink the A/C from automatic climate control operation.

3. Make sure the default setting for the climate automatic switch from heating, footwell, into cooling mode, is OFF.

[lex_luthor]

Could you explain why I'd want those options changed to how you describe?

I just want to make sure those are changes I'd personally want as well.

I guess I'll ask the dealer for a master list of options.

[Guest dms666]

You are referring to the famous C-BEST settings.

Here is a list of the modifications that can be made. I had the following changes made:

1. Open all doors when shifted into Park.

2. Lock all doors when shifted into Drive.

3. Open all doors with one press of key remote unlock button.

[lex_luthor]

Thanks! That should be real helpful.

You know 1 and 2 that you listed can be done on your own. The manual lists how to do that.

I'd still like to know what all those A/C settings above do.

I'll definitely review this document.

[wwest]

Absent the changes the A/C will run automatically, maintain the cooling evaporator as close to 32F as possible, all year 'round, with only one exception and that is if the OAT declines below about 33F.

Needlessly running the A/C can cost you about 10% highway fuel economy and as much as 30% (extreme) city. During the summer months the only benefit with OATs below 65F is the dehumidification capability. At those temperatures the human body "at rest" is not usually discomforted by high humidity levels. 40% RH, generally, is thought to be our "mean" at rest comfort level and we generally don't begin to notice/react to RH as high as 80% at these temperatures.

By unlinking the A/C from automatic use you get to determine when it operates. Once you turn it on it will remain in use through restarts, etc, until you turn it off.

On days that you do use the A/C you can radically increase your personal comfort level and the system cooling efficiency, thereby also helping fuel economy at an additional level, by setting the system to max cool and recirc and then using the manual blower speed control to maintain your own personal comfort level. If, over time (l_o__n___g trip), I start to feel too cool then I first switch the system to combined dash/footwell outflow, and then if that's still too cooling, to "fresh".

On a hot and really BRIGHT sunny day I find that very cool, almost cold, low velocity airflow from the outlets increases my comfort level significantly over the reheated ~65 airflow the system would normally supply.

If you want to get really extreme you can add an electrically controlled water control valve to prevent the otherwise constant how water flow through the heater core within the A/C plenum when in "cooling" mode. Although in "max cool" none of the system airflow is intentionally reheated via flow through the heater core you would be surprised at how many BTUs of cooling is required to overcome the radiant heating effects from a heater core elevated to the 190F engine operating temperatures.

Without unlinking the A/C from operating automatically (with no indicator of same to the driver) in defog/defrost/demist, you may find yourself suddenly with absolutely NO FORWARD VISION some fairly cool morning or shortly after the oAT declines below 35F.

The Toyota/Lexus/NipponDenso (Denso US) automatic climate control system relies EXCLUSIVELY on the dehumidification capability of the A/C to defog and/or prevent fogging of the windshield. First, neither you, as the driver/operator, nor any system component, can determine if the A/C can be functional for this capability in varying climatic conditions.

As the ambient OAT declines the level of moisture the atmosphere can hold, in absolute terms also declines, and even beyond absolute values, the predominant RH also declines during the winter months in many areas of the US.

What this means to you is that the functionality of the A/C to be of any help at all in defogging the windshield and/or preventing it from fogging over, is totally and completely unpredictable.

The A/C evaporator cannot operate below freezing level without soon becoming clogged with frozen condensate. Most designs regulate the refrigerant flow in some manner such that the evaporator cooling vane surface temperature NEVER declines below ~35F.

So the incoming airflow cannot be dehumidified at all unless cooling it to a low of 35F will bring it to dewpoint, the level at which the moisture contained in the airflow begins to precipate out of the airflow and condense on the COLD evaporator vanes. With the OAT below about 47F the RH must be unusually high, Seattle say, for dehumidification to occur.

And please note that if you happen to be relying, hopefully inadvertently, on one of these systems for defogging your windshield, turning the blower speed up to accelerate the defogging effects has an adverse affect. The slower the airflow moves through the evaporator the cooler it will become, increasing the probability that it will be cooled to dewpoint and therefore some level of dehumidification will actually occur.

The Toyota/Lexus/Denso theory is that "washing" the interior surface of the windshield with DRY airflow will defog it fairly quickly and this is absolutely true, the theory is absolutely correct, it's in the practice, as implemented by Denso, that the theory falls apart.

We all know that windshield fogging is much more prevalent in cool and/or colder weather, really we can say its restricted to that enviroment.

Back when we first started to enclose the passenger compartments of our vehicles we quickly discovered that this resulted in the creation of an environment in which the propensity of the interior surfaces of the windshield and windows increased dramatically. As a result we quickly, just as quickly, discovered that providing lots of fresh airflow through the cabin virtually eliminated the problem.

But guess what?

Driving around in the wintertime with all that now COLD fresh air flowing freely through the cabin tended to freeze our tails off. So we added in car heating.

And guess what?

We discovered that heating the cabin atmosphere to our personal comfort level also resulted in lowering the RH and thereby the probably of encountering windshield and window fogging.

But the exceptions were dramatic to say the least. Stop and pick up some one who has walked a mile or so in the cold freezing rain, or a couple of sweaty snow skiiers, or just the kids at school after a few minutes of standing out in the rain all bundled up in winter coats and clothing.

Bingo! The RH inside the cabin goes up dramatically within just a few minutes and now the atmospherically carried moisture begins to condense on the cool (that's really cold airflow impinging on the windshield exterior surface at roadway speeds) interior windshield surface.

Okay, QUICK, lower those rear windows and get some fresh (COLD, Brrrrr...) air in here, flushing the moisture laden atmosphere from the passenegr cabin.

OR....

Hmmmm.....

Why not simply HEAT the windshield so that its interior surface temperature never declines to the dewpoint of the cabin atmosphere?

DONE!

And that's how things remained, pretty much, until the advent of A/C equipped vehicles.

Once A/C was installed in the very first automobile I'm quite sure it wasn't very long before someone discovered that an ancillary function, and undesired one up until now

[DURSO]

Absent the changes the A/C will run automatically, maintain the cooling evaporator as close to 32F as possible, all year 'round, with only one exception and that is if the OAT declines below about 33F.

Needlessly running the A/C can cost you about 10% highway fuel economy and as much as 30% (extreme) city. During the summer months the only benefit with OATs below 65F is the dehumidification capability. At those temperatures the human body "at rest" is not usually discomforted by high humidity levels. 40% RH, generally, is thought to be our "mean" at rest comfort level and we generally don't begin to notice/react to RH as high as 80% at these temperatures.

By unlinking the A/C from automatic use you get to determine when it operates. Once you turn it on it will remain in use through restarts, etc, until you turn it off.

On days that you do use the A/C you can radically increase your personal comfort level and the system cooling efficiency, thereby also helping fuel economy at an additional level, by setting the system to max cool and recirc and then using the manual blower speed control to maintain your own personal comfort level. If, over time (l_o__n___g trip), I start to feel too cool then I first switch the system to combined dash/footwell outflow, and then if that's still too cooling, to "fresh".

On a hot and really BRIGHT sunny day I find that very cool, almost cold, low velocity airflow from the outlets increases my comfort level significantly over the reheated ~65 airflow the system would normally supply.

If you want to get really extreme you can add an electrically controlled water control valve to prevent the otherwise constant how water flow through the heater core within the A/C plenum when in "cooling" mode. Although in "max cool" none of the system airflow is intentionally reheated via flow through the heater core you would be surprised at how many BTUs of cooling is required to overcome the radiant heating effects from a heater core elevated to the 190F engine operating temperatures.

Without unlinking the A/C from operating automatically (with no indicator of same to the driver) in defog/defrost/demist, you may find yourself suddenly with absolutely NO FORWARD VISION some fairly cool morning or shortly after the oAT declines below 35F.

The Toyota/Lexus/NipponDenso (Denso US) automatic climate control system relies EXCLUSIVELY on the dehumidification capability of the A/C to defog and/or prevent fogging of the windshield. First, neither you, as the driver/operator, nor any system component, can determine if the A/C can be functional for this capability in varying climatic conditions.

As the ambient OAT declines the level of moisture the atmosphere can hold, in absolute terms also declines, and even beyond absolute values, the predominant RH also declines during the winter months in many areas of the US.

What this means to you is that the functionality of the A/C to be of any help at all in defogging the windshield and/or preventing it from fogging over, is totally and completely unpredictable.

The A/C evaporator cannot operate below freezing level without soon becoming clogged with frozen condensate. Most designs regulate the refrigerant flow in some manner such that the evaporator cooling vane surface temperature NEVER declines below ~35F.

So the incoming airflow cannot be dehumidified at all unless cooling it to a low of 35F will bring it to dewpoint, the level at which the moisture contained in the airflow begins to precipate out of the airflow and condense on the COLD evaporator vanes. With the OAT below about 47F the RH must be unusually high, Seattle say, for dehumidification to occur.

And please note that if you happen to be relying, hopefully inadvertently, on one of these systems for defogging your windshield, turning the blower speed up to accelerate the defogging effects has an adverse affect. The slower the airflow moves through the evaporator the cooler it will become, increasing the probability that it will be cooled to dewpoint and therefore some level of dehumidification will actually occur.

The Toyota/Lexus/Denso theory is that "washing" the interior surface of the windshield with DRY airflow will defog it fairly quickly and this is absolutely true, the theory is absolutely correct, it's in the practice, as implemented by Denso, that the theory falls apart.

We all know that windshield fogging is much more prevalent in cool and/or colder weather, really we can say its restricted to that enviroment.

Back when we first started to enclose the passenger compartments of our vehicles we quickly discovered that this resulted in the creation of an environment in which the propensity of the interior surfaces of the windshield and windows increased dramatically. As a result we quickly, just as quickly, discovered that providing lots of fresh airflow through the cabin virtually eliminated the problem.

But guess what?

Driving around in the wintertime with all that now COLD fresh air flowing freely through the cabin tended to freeze our tails off. So we added in car heating.

And guess what?

We discovered that heating the cabin atmosphere to our personal comfort level also resulted in lowering the RH and thereby the probably of encountering windshield and window fogging.

But the exceptions were dramatic to say the least. Stop and pick up some one who has walked a mile or so in the cold freezing rain, or a couple of sweaty snow skiiers, or just the kids at school after a few minutes of standing out in the rain all bundled up in winter coats and clothing.

Bingo! The RH inside the cabin goes up dramatically within just a few minutes and now the atmospherically carried moisture begins to condense on the cool (that's really cold airflow impinging on the windshield exterior surface at roadway speeds) interior windshield surface.

Okay, QUICK, lower those rear windows and get some fresh (COLD, Brrrrr...) air in here, flushing the moisture laden atmosphere from the passenegr cabin.

OR....

Hmmmm.....

Why not simply HEAT the windshield so that its interior surface temperature never declines to the dewpoint of the cabin atmosphere?

DONE!

And that's how things remained, pretty much, until the advent of A/C equipped vehicles.

Once A/C was installed in the very first automobile I'm quite sure it wasn't very long before someone discovered that an ancillary function, and undesired one up until now

[wwest]

I wrote most of that between 5 and 7AM when I realized if I didn't hurry I would be late for work.

But while standing in the shower and thinking over what I had written a rather strange thought came to mind.

Remember those pictures of cars from the roaring twenties where the driver/ showfer sat out front in the weather while the passenger sat warm and cosy in the fully enclosed cabin?

I always thought that to be the height of arrogance on the part of the owners but I just came to the realization that there may have been a really practical reason. The windshield would likely never fog over.

[lex_luthor]

wwest, thank you very much for that detailed reply.

Could you do me one more favor and look at dms666's post/attachment and tell me exactly which options there I should set to what. I really don't want to do the wrong thing......

Thanks!

[wwest]

I just read the C-best attachment and the wording seems to me to be so obtuse that I end up with no idea what its meaning really is. If I were you I would go sit down with a lexus service manager and have her explain each and every option.

If anyone can explain the options in plain english I would be very interested.