A/C and starting

Does the compressor put much of a load on the engine at startup?
Lately I've taken to turning the A/C off after I shutdown the engine
and giving it a couple of seconds of run time before I turn the A/C
back on. Am I being silly? If it only saves a couple of percent, yes
I am.
--

- dillon I am not invalid

"Iran wants nukes? North Korea wants nukes?
I'm sure we can give them some. Or the Navy."

- former B52 wing commander

Dillon Pyron > wrote in
:

> Does the compressor put much of a load on the engine at startup?
> Lately I've taken to turning the A/C off after I shutdown the engine
> and giving it a couple of seconds of run time before I turn the A/C
> back on. Am I being silly? If it only saves a couple of percent, yes
> I am.



The compressor clutch will not engage until the engine is running, so the
position of the A/C switch makes no difference on startup.

You're better to turn the A/C off a couple of miles from home, not right at
shutoff. Allowing the evaporator a few minutes to come to ambient
temperature (with the blower fan remaining on) will help dry up the
condensation that eventually leads to that "stinky socks" smell.

--
Tegger

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

On Aug 24, 2:13 pm, Dillon Pyron > wrote:
> Does the compressor put much of a load on the engine at startup?
> Lately I've taken to turning the A/C off after I shutdown the engine
> and giving it a couple of seconds of run time before I turn the A/C
> back on. Am I being silly? If it only saves a couple of percent, yes
> I am.

I go beyond that. I usually don't turn on AC until the engine has
warmed up (at least a minute).

On 8/24/09 4:13 PM, in article ,
"Dillon Pyron" > wrote:

> Does the compressor put much of a load on the engine at startup?
> Lately I've taken to turning the A/C off after I shutdown the engine
> and giving it a couple of seconds of run time before I turn the A/C
> back on. Am I being silly? If it only saves a couple of percent, yes
> I am.

Most cars don't energize the compressor until the key is back in the "run"
position after starting. Now if your engine is flaky & doesn't start up
smoothly, it might have a hard time with the extra load hitting it shortly
after starting, but there is no extra load while starting.

Thus spake Tegger > :

>Dillon Pyron > wrote in
:
>
>> Does the compressor put much of a load on the engine at startup?
>> Lately I've taken to turning the A/C off after I shutdown the engine
>> and giving it a couple of seconds of run time before I turn the A/C
>> back on. Am I being silly? If it only saves a couple of percent, yes
>> I am.
>
>
>
>The compressor clutch will not engage until the engine is running, so the
>position of the A/C switch makes no difference on startup.
>
>You're better to turn the A/C off a couple of miles from home, not right at
>shutoff. Allowing the evaporator a few minutes to come to ambient
>temperature (with the blower fan remaining on) will help dry up the
>condensation that eventually leads to that "stinky socks" smell.

Thanks. More for the stinky socks advice. I HATE that with a
passion.

And if you have a turbo, make sure it idles for at least 30 seconds,
unless you have some sort of additional pressure oiling system.
--

- dillon I am not invalid

"Iran wants nukes? North Korea wants nukes?
I'm sure we can give them some. Or the Navy."

- former B52 wing commander

Dillon Pyron wrote:
> Thus spake Tegger > :
>
>> Dillon Pyron > wrote in
>> :
>>
>>> Does the compressor put much of a load on the engine at startup?
>>> Lately I've taken to turning the A/C off after I shutdown the engine
>>> and giving it a couple of seconds of run time before I turn the A/C
>>> back on. Am I being silly? If it only saves a couple of percent, yes
>>> I am.
>>
>>
>> The compressor clutch will not engage until the engine is running, so the
>> position of the A/C switch makes no difference on startup.
>>
>> You're better to turn the A/C off a couple of miles from home, not right at
>> shutoff. Allowing the evaporator a few minutes to come to ambient
>> temperature (with the blower fan remaining on) will help dry up the
>> condensation that eventually leads to that "stinky socks" smell.
>
> Thanks. More for the stinky socks advice. I HATE that with a
> passion.
>
> And if you have a turbo, make sure it idles for at least 30 seconds,
> unless you have some sort of additional pressure oiling system.

pressure isn't the issue with a turbo, it's "heat soak". heat from the
turbine conducts back to the shaft and the bearings after it's switched
off and cooks the oil in it. allowing the turbine to cool by idling
[some trucks used to spec three minutes] before switch off mitigates
this. using an oil that can take the heat [synthetics] is strongly
recommended.

jim beam > wrote in
t:

> Dillon Pyron wrote:

>>
>> And if you have a turbo, make sure it idles for at least 30 seconds,
>> unless you have some sort of additional pressure oiling system.
>
> pressure isn't the issue with a turbo, it's "heat soak". heat from
> the turbine conducts back to the shaft and the bearings after it's
> switched off and cooks the oil in it. allowing the turbine to cool by
> idling [some trucks used to spec three minutes] before switch off
> mitigates this. using an oil that can take the heat [synthetics] is
> strongly recommended.
>


I think what Dillon means is the sort of system that maintains oil flow
through the turbo for X-minutes after engine shutdown. Such a system is
meant to prevent the oil in the turbo from being heated to the point of
coking.


--
Tegger

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

Thus spake Tegger > :

>jim beam > wrote in
et:
>
>> Dillon Pyron wrote:
>
>>>
>>> And if you have a turbo, make sure it idles for at least 30 seconds,
>>> unless you have some sort of additional pressure oiling system.
>>
>> pressure isn't the issue with a turbo, it's "heat soak". heat from
>> the turbine conducts back to the shaft and the bearings after it's
>> switched off and cooks the oil in it. allowing the turbine to cool by
>> idling [some trucks used to spec three minutes] before switch off
>> mitigates this. using an oil that can take the heat [synthetics] is
>> strongly recommended.
>>
>
>
>I think what Dillon means is the sort of system that maintains oil flow
>through the turbo for X-minutes after engine shutdown. Such a system is
>meant to prevent the oil in the turbo from being heated to the point of
>coking.

Yeah. Since I don't race "tin tops" any more, I can't remember the
name of the system that did that. It would store up about a litre of
oil in a little resivor and then use either air pressure (via a
piston) or an electric pump to push the oil into the system. They
also had one that primed the system at startup.

With three pump dry sump systems, I don't worry about that, much.
--

- dillon I am not invalid

"Iran wants nukes? North Korea wants nukes?
I'm sure we can give them some. Or the Navy."

- former B52 wing commander