Is it true?

Submitted: Tuesday, Jan 27, 2009 at 15:17
ThreadID: 65456 Views:2160 Replies:5 FollowUps:6
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Hi Guys,
Upon our descent of Billy Goat Bluff track from the pinnacles on the weekend it was advised that the first 700 metres required extra caution.This section was pretty chopped up with loads of rocks,steep and quite loose.Apart from low first it was also advised to run the air con to further assist engine braking.I had it on anyway but does anybody know if this actually does assist in severe down hill descents.
Thanks Mark
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Reply By: Crackles - Tuesday, Jan 27, 2009 at 15:24

Tuesday, Jan 27, 2009 at 15:24
Depends on each vehicle. For some the extra load of the aircon helps improve engine breaking marginally but on others they have an idle up feature that would make it worse. Billy Goat track is certainly not that steep to worry about it unless you're driving something geared very high like a Subaru for example.
Cheers Craig............
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Follow Up By: marcus - Tuesday, Jan 27, 2009 at 15:37

Tuesday, Jan 27, 2009 at 15:37
Thanks Craig but wouldn't expect to be seeing too many Subaru's coming down there at the moment in its current condition.
Mark
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Follow Up By: Robin Miller - Tuesday, Jan 27, 2009 at 15:51

Tuesday, Jan 27, 2009 at 15:51
Yep guys , my pathfinder had the idle up relay which I arranged a switch on to disengage as approprite.

Whereas in my current petrol Patrol , it not only makes no difference but in a controlled test on nearby station track we were able to demonstrate that turning the engine off even made no difference.
Thankfully the GU is a manual though with acceptable engine braking.
Robin Miller

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Follow Up By: Crackles - Wednesday, Jan 28, 2009 at 13:16

Wednesday, Jan 28, 2009 at 13:16
"wouldn't expect to be seeing too many Subaru's coming down there at the moment "
What, you mean like these one's Mark? :-)
You'd be surprised where a capable driver can get a Subie & this was back before the difficult rock ledges & boulder strewn sections were leveled out.

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Reply By: Madfisher - Tuesday, Jan 27, 2009 at 15:41

Tuesday, Jan 27, 2009 at 15:41
Most vehicles have an ilde up for air con, but after 1000rpm you do get extra engine braking. I tend to use it as an engine brake more on the road when towing my boat. Years ago I had a Rocky diesel that could decend very steep hills in fourth with the air with out touching the brakes. But modern air con units are much more efficent, and modern vehicles are geared much higher with low ficton engines.
Cheers Pete
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Reply By: Wayne (NSW) - Tuesday, Jan 27, 2009 at 17:45

Tuesday, Jan 27, 2009 at 17:45
Mark,

If you think that it is rough coming down, try going up.

I was there a few weeks ago and some of the petrol vehicles in the convey had to turn the air con off just to make sure that they did not stall or lose power.

Years ago when the idle up on the air con was not an option we use to run the air con on petrol vehicles and even run with high beam and driving lights on just to try and slow the vehicle. It did help but with the gearing being high, even in low range, first gear, the vehicle still felt that it was racing down hill.

Nothing beats a big 6cyl diesel with a manual Toyota gear box for going down hills slow.

Wayne

AnswerID: 346191

Follow Up By: pickle - Tuesday, Jan 27, 2009 at 18:09

Tuesday, Jan 27, 2009 at 18:09
Drove up Billy Goat on Sunday. Bit more chopped up than usual.
Certainly wouldn't recommend running air con going up or down. Sort of seperating yourself from nature with the windows up as well.
Dave
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Reply By: Geoff (Newcastle, NSW) - Tuesday, Jan 27, 2009 at 18:05

Tuesday, Jan 27, 2009 at 18:05
On a certain level I can understand the theory but on another level I don't.

If I use my TD Troopy as an example it'd actually go down the hill faster with the air conditioning on.

The reason for that is the idle up solenoid mentioned by a couple of people above.

As Wayne has mentioned, the best way to go down a hill real slow is with a big diesel six, low range and a manual gearbox.

I guess it depends on the age and the configuration of the vehicle.

Geoff
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AnswerID: 346198

Reply By: Member - Kiwi Kia - Tuesday, Jan 27, 2009 at 20:29

Tuesday, Jan 27, 2009 at 20:29
It works fantastically well on my Kia. A/C off and I have to keep touching the brakes to keep it dead slow. Switch the A/C on and I can put both feet on the floor on the steepest grade.

.
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Follow Up By: Member - Teege (NSW) - Tuesday, Jan 27, 2009 at 21:17

Tuesday, Jan 27, 2009 at 21:17
My auto 2000 Prado is the exact opposite. Turn the air off and keep the foot off the brake. Run the air and constantly on the brake.

teege
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Follow Up By: Member - Kiwi Kia - Tuesday, Jan 27, 2009 at 23:04

Tuesday, Jan 27, 2009 at 23:04
Hi Teege, That would be right - an auto transmission with idle-up when A/C is switched on.

.
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