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Gas mileage: AWD mode Vs. Front wheel drive mode


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Hello,

 

 

I have been in a huge battle trying to get past the smog issue in California. However, I think I may have found a loophole with my custom project build.

 

Vehicles with permanent AWD, or traction control that cannot be disabled are exempt from having to go on the dynamometer.

 

So my question is: In my 79 BRAT there is an option for all wheel drive, and an option for just front wheel drive.

 

What is your fuel mileage in all wheel drive mode, and what is your fuel mileage in front wheel drive mode?

 

If I make the transmission AWD only, (D/R tranny) then I don't have to have the thing on a dynamometer, and that will make passing the check that much easier.

 

Thanks!

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Well there won't be a huge difference in gas mileage, but when your Brat is in 4WD it is not AWD! It will not drive well at all on tar and will make things wear very quickly, so that's not really an option you have, unless you somehow swap in a different tranny that is actually all wheel drive and not four wheel drive

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While they won't load an engine/drivetrain with AWD, they will still do a visual inspection for all smog gear, catalyst, etc, and then perform sniffer test at the prescribed idle and RPM levels.

 

If all your equipment is working, but failing HC or NOx levels, it's a whole lot easier to just add two gallons of denatured alcohol ($14/gal) to 1/8 to 1/4 tank gasoline and watch the magic.

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The only 5 speed D/R that was AWD (Full-Time 4WD really) was the 87 to 89 RX transmission. It is a form of AWD with a center locking diff that allows it to go from AWD to 50/50 4WD. Although the low range is only 1.2:1 and the diff ratio is 3.7 so it's really a very poor choice for off-road unless at *least* the low range is changed to 1.59:1 - but that requires a full transmission dissasemble and reassemble plus sacrificing a true 3.9 ratio D/R for it's low range gear set and input shaft assembly.

 

GD

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OK, so I have been to lucerne valley, and it amazes me that they actually require enhanced smog (dyno) way out there.. I mean.. thats like.... REMOTE.

 

I live in San Luis Obispo county and they dont even require enhanced.

 

As far as your situation goes. Anything 4wd, selectable or not, for safety reasons they should be only doing an idle/2500 smog test. The transmission isnt designed to have the front wheels spinning with the back wheels stopped. If the smog tech damages your transmission while smogging it, then the shop is liable for any damages.. long story short, its much easier for the tech to override the dyno test and usually always does for anything 4wd.

 

The dyno test only tests for oxides of nitrogen additionaly to what a normal test does. Unless youve removed the catalytic convertor from your 79 brat that it didnt come with :lol:.. doing the enhanced test over the standard test shouldent make a difference. What I would be worried about on something that old, is the new evap pressure test. If your evap system is not hooked up right or you have a rust hole in the top of your gas tank, they'll fail you for it just cause your gas tank wont hold pressure.

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They don't have a two axle dyno? Here, they have a special lane for the full time AWD vehicles, because there are so many of them. I can't imagine they could run an effective smog program otherwise. But maybe CA doesn't have as many subarus and such.

 

They still can't run the dyno if you have studded tires -- which kind of sucks. Several of my vehicles are unregistered because I don't drive them enough in the summer to warrant buying a whole new set of tires just to dyno them (but luckily most of them of getting old enough to get collector plates soon and not require dyno tests every year).

 

Z

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