AERODYNAMICS

Guess things have changed a bit since we drove our coaches trans-canada a
few years ago. We only used fuel from one major supplier, and always got
the alcohol free fuel . At that time, you could pick your octane
requirement. We used 88 octane during the whole trip. I believe the brand
was Petro-Canada. As soon as we returned stateside, our mileage dropped 15
to 20 % over what we were getting in Canada and the old vapor lock symptoms
returned as well. Some of our travels were in the Canadian Rockies and the
Altitude reached 10,000 feet in some places. No knocks, no pings, no
nothing.
Jim Hupy
Salem, Oregon

On Sun, Feb 7, 2021 at 1:41 PM Dave King via Gmclist <

> to James Hupy. Re Canadian Gasoline. I believe for all brands in Toronto
> they now all contain Ethanol EXCEPT the Premium 91 Octane.
> A lot of pumps are labelled like this On the 87 Octanc may contain up to
> 10% Ethanol, the 89 Octane may contain up to 5% Ethanol
> and on the 91 Octane Contains No ethanol. We also have 93 and 94 octane I
> believe they get this by adding Ethanol to the Ethanol
> free 91 Octane as the 93 and 94 do contain Ethanol. It is expensive to use
> the 91 just to avoid Ethanol in a vehicle that really doesn't care.
>
> I keep planning to do some back to back long distance comparison with 87
> Octane and 91 but it never works out. My 2007 Dodge Grand Caravan
> 3.8 L motor doesn't seem to care. If I get the motorhome back on the road
> maybe I can get more performance info.
> --
> DAVE KING
> lurker, wannabe
> Toronto, Ontario, Canada
>
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One need to fill at least 5 times to get a close figure as it will vary
each time you fill up.
One tankfull is not worth using to obtain any worthwhile milage calculation.

On Mon, Feb 8, 2021 at 2:38 PM James Hupy via Gmclist <

> Guess things have changed a bit since we drove our coaches trans-canada a
> few years ago. We only used fuel from one major supplier, and always got
> the alcohol free fuel . At that time, you could pick your octane
> requirement. We used 88 octane during the whole trip. I believe the brand
> was Petro-Canada. As soon as we returned stateside, our mileage dropped 15
> to 20 % over what we were getting in Canada and the old vapor lock symptoms
> returned as well. Some of our travels were in the Canadian Rockies and the
> Altitude reached 10,000 feet in some places. No knocks, no pings, no
> nothing.
> Jim Hupy
> Salem, Oregon
>
> On Sun, Feb 7, 2021 at 1:41 PM Dave King via Gmclist <

>
> > to James Hupy. Re Canadian Gasoline. I believe for all brands in Toronto
> > they now all contain Ethanol EXCEPT the Premium 91 Octane.
> > A lot of pumps are labelled like this On the 87 Octanc may contain up to
> > 10% Ethanol, the 89 Octane may contain up to 5% Ethanol
> > and on the 91 Octane Contains No ethanol. We also have 93 and 94 octane I
> > believe they get this by adding Ethanol to the Ethanol
> > free 91 Octane as the 93 and 94 do contain Ethanol. It is expensive to
> use
> > the 91 just to avoid Ethanol in a vehicle that really doesn't care.
> >
> > I keep planning to do some back to back long distance comparison with 87
> > Octane and 91 but it never works out. My 2007 Dodge Grand Caravan
> > 3.8 L motor doesn't seem to care. If I get the motorhome back on the road
> > maybe I can get more performance info.
> > --
> > DAVE KING
> > lurker, wannabe
> > Toronto, Ontario, Canada
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
> One need to fill at least 5 times to get a close figure as it will vary each time you fill up.
> One tankfull is not worth using to obtain any worthwhile milage calculation.

In the time I was getting to know Chaumière, I would sample all the fuel we bought. I would use a modified version of KenB's alcohol measurement and
would that with the other data. When the fill vent and vapor valve got fixed, I could see the alcohol content in the fuel almost exactly as reduced
mileage (increased fuel rate). The only scatter was cause by the overlap of different fuel quality. It was otherwise very consistent.

For the most part, I would agree with you Jim(K), but we have had a working vapor valve and the modified fill vent for a while, so I can take on fuel
to with better than normal consistency. When I did the overhaul in 2018, I was very concerned that I would be back to the 9.2 that I count on. I
drove the new engine about 190 miles around town (I wanted to be over 200). Then we took off for Ankeny/Amana and the fall international. That was
just short of 1200miles. We were home long enough to answer the mail and wash some clothes before we made of Albany a class reunion for Mary. That
was a little over 1300 miles with the stops to visit friends and family.

This applies in this case because I log each fuel stop mileage, fill and cost. Each got better as the new parts (lots of new parts) settled in. Half
way across NY, that fill came up to total since departure on September 18 to October 03 and about 2000 Miles of 9.1. With the last fill on the
backhaul which included so doodle-bopping in Albany we were back to 9.3 with a standard deviation of less that 0.2MPG. That is about the deviation I
usually see and it is about a 3% which is also the deviation I see between our odometer and the GPS trip log. Unfortunately, the actual logs of those
mentioned excursions were lost with the hard drive crash on the way home from Tallahassee.

Then again... Thinking can be dangerous. I only just now figured out that I can rebuild that fuel consumption from the fuel slips that are probably
waiting for me on the visor of Chaumière. Every fuel stop, I write the mileage on the fuel slip(s). The date and location is already on there.

So, I believe that JimH could detect that alcohol content.

Matt
--
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
 
G'day,

Here's a link to the model that Bill says was used to do the wind tunnel testing:

http://www.gmcmhphotos.com/photos/the-bill-bryant-collection/p1621.html

It doesn't look like any GMC I've ever seen on the road, it has no mirrors, no awning, no a/c units, or spare tire.

Anything and everything that protrudes from the vehicle causes turbulence in the airflow over the vehicle. IMHO there is no way in hell a "real" GMC
would attain a CD of 0.031.

--
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
 
OOPS!

I copied the 0.031 CD from a previous message, it should be 0.3.
--
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
 
Alex Birch's grandson Greg, has the actual model that was used in wind
tunnel tests. He is a member of the GMC Cascaders, and his grandmother gave
many of Alex's collected items to Greg. He brought several of them to
various Cascader rallies. Some really, really neat stuff there.
Jim Hupy
Salem, Oregon

On Mon, Feb 8, 2021, 8:56 PM Robert Mueller via Gmclist <

> OOPS!
>
> I copied the 0.031 CD from a previous message, it should be 0.3.
> --
> Regards,
> Rob M. (USAussie)
> The Pedantic Mechanic
> Sydney, Australia
> '75 Avion - AUS - The Blue Streak TZE365V100428
> '75 Avion - USA - Double Trouble TZE365V100426
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
> OOPS!
> I copied the 0.031 CD from a previous message, it should be 0.3.

Unfortunately, what the 0.3CD only tells you is how it relates to a prismatic (block shape) of the same basic dimensions. It is still a 9'tall, 8'
wide and 26(23)' block, it will just not be as draggy.

From my short time working at a UofM aero lab, I would suspect that the mirrors are the big killer. We were working on stuff for some (unremembered)
major truck builder. We did a lot, but much is forgotten. The thing I most remember is that the truck at highway speed was so far out of the laminar
range that small surface issues like lights and door handles could not be detected. Major fairings did matter and the smoke test told us all about
the space between the cab and the rear wheels. The big west coast mirrors on the model were "Hold that Smoke!". We did one abbreviated run with the
upwind side of the mirrors somewhat faired (we stuck clay on them) and that change was not significant.

I know the new door handles on passcars were really to eliminate pedestrian snagging and not an aero consideration, but they were sold that way.
Some new vehicles have a 360° camera set up, does anybody know if they eliminated the side mirrors?

Now, I could find out some way to get rid of my mirrors, the low profile Carrier A/C would not change much and I could be real near that 0.3 block.
Note: The real reason for the low profile A/C was to clear my barn door.

Matt
--
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
 
The single biggest improvement was tucking in the bumpers.
First trip I noticed a HUGH noise reduction and improved mileage.
 
I'm no sure what 'tucking in the bumpers' means. (Probably not
skootching them into bed with a goodnight kiss).

Is there a photo somewhere ?

Thanks

Stu

Quoting Mike Sadlon via Gmclist :

> The single biggest improvement was tucking in the bumpers.
> First trip I noticed a HUGH noise reduction and improved mileage.
>
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