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Re: MGB Fuel Mileage

To: Charles & Peggy Robinson <ccrobins@ktc.com>
Subject: Re: MGB Fuel Mileage
From: Phil Bates <jello@ida.net>
Date: Sat, 26 Mar 2005 10:03:25 -0700
What I mean is that I need to do some adjustments to the OD system.  I'm 
not really sure what is wrong yet, and as it's cold, I haven't tried 
that hard to track it down.  Generally, though, I drive 22 miles a day 
on the freeway.  When I get up to 75 (which is the speed limit here - I 
don't speed anymore) I turn on the overdrive.  It usually takes about 15 
seconds to kick down into overdrive, and the overdrive usually stays 
turned on for about 10 miles.  Then it kicks back out, and doesn't want 
to go back into overdrive for that trip.  That afternoon, same thing, as 
well as the next morning etc.  I suspected the solenoid, and had a few 
issues there - but ultimately they were easily correctible.  Then I 
suspected the plunger adjustment - I can't get to that right now to 
check it.  But right now I'm kind of thinking it's either my relay, or 
that my screen (in the O/D oil pressure system) isn't as clean as it 
should be.

This will sound strange to a lot of people though - I don't think it 
effects the mileage much.  The reason I say that is that I have a 
manifold vacuum gauge installed - which should give a fair read of your 
efficiency.  Whether the OD is on or off, I have the same vacuum reading 
at freeway speeds.  Then again that could be bad theory because 
certainly at higher engine speeds, the engine develops more vacuum, so 
to even out the manifold pressure compared to higher speeds, the carb 
buttrfly's must be more open - but I don't move my gas pedal when teh OD 
kicks out.  It is an infinately more comfortable drive with the 
overdrive though.

Phil Bates
'67 MGB
'58 MGA
misc other europen cars

Charles & Peggy Robinson wrote:

> Phil Bates wrote:
>
>> I think it depends a lot on your tuning abilities.  You can get 30, in
>> good tune and with an engine in good condition.  I'm up a bit in 
>> altitude
>> (at 4800 ft) and I only get 22.  Most of my driving is on the freeway at
>> 75mph - and I've been driving the B everyday.  The overdrive is about 
>> 1/2
>> functional.
>
>
>   What do you mean by, "The overdrive is about 1/2 functional"?  In my 
> experience, it works or it doesn't.
>
>   Cheers,
>
>    CR




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