Mileage with a Motor Home

Bernie Jacobsen bcjac at ix.netcom.com
Tue Mar 31 04:55:28 GMT 1998


-----Original Message-----
From: Raymond C Drouillard <cosmic.ray at juno.com>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Monday, March 30, 1998 11:22 PM
Subject: Re: Mileage with a Motor Home


>>> >-----Original Message-----
>>> >From: Dave Balfour <balfour at bushnell.net>
>>> >To: diy_efi at efi332.eng.ohio-state.edu
>><diy_efi at efi332.eng.ohio-state.edu>
>>> >Date: Friday, March 27, 1998 9:56 PM
>>> >Subject: Re: Mileage with a Motor Home
>>> >
>> Will it not take more than headers to pull the max torque down by
>>nearly 30%?? Even a 454 may tend to lug at 1800RPM on a machine the size
>>of your MH. If it lugs, the vacuum drops, and with it fuel economy. The
>>reason MAX torque RPM gives best fuel economy is because it allows
>>highest sustained cruise vacuum. Anything above or below tends to drop
>>off vacuum if running anywhere close to rated load.
>
>Maximizing vacuum increases mileage?  What about pumping losses?
>
>If I find the speed of maximum torque on my 360 Jeep engine, should I set
>it up to run at that speed when I am cruising?

How will you find this?  Dyno?  If so,  do you know what your manifold vac
is when cruising?  Use that on the dyno. Measure fuel usage at that level of
manifold vac. at various RPM's. This will tell you a lot.

>
>Ray Drouillard
>'89 Grand Wagoneer
>Holley Pro-Jection, Jacobs ignition, Edelbrock performer manifold, Engine
>Guard pre-luber, 3" exhaust system, 30x9.5 tires, stock 2.72:1 axles

That's pretty tall! you are probably under 2,000 rpm when cruising at 60. Of
course that's not so tall if you normally cruise at 80.

^Bernie




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