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914World.com _ FS/WTB: 914 Parts _ adjust mixture for different elevations
Posted by: redflagmaclo Jun 2 2022, 12:09 PM
I’m wondering if anyone has reccomendations on how to splice/add a variable resistance potentiometer in the main electric line from the manifold pressure unit to the ECU.. I’m going to be spending a lot of time in the Santa Fe/Los Alamos NM area which covers 5000’ to 7800’ elevations. I need the ability to lean the mixture as I travel from 1000’ MSL to over 8000’. My son and grandkids live there and I can now spend quality time with them and I make 2 visits a year from NC. I’m the original owner of a ‘74 2 liter and have just become a member of this group. Wish I had joined a long time ago.
Posted by: TheCabinetmaker Jun 2 2022, 12:49 PM
I've driven all over that area. Never had any problems with my djet.
Posted by: brant Jun 2 2022, 01:58 PM
unless your running a wide band AFR read out.
not sure I'd mess with the mixture
the system self adjusts somewhat for altitude already
and the risk of damage from turning it lean... by the seat of your pants... would worry me.
the motors like to run lean... feel good when they are lean... right up to the point that damage occurs.
Posted by: StarBear Jun 2 2022, 02:06 PM
Wow, another original owner! That makes maybe 7-8 of us.
Welcome aboard! 
Posted by: JeffBowlsby Jun 2 2022, 03:49 PM
D-Jet automatically adjusts for differences in atmospheric pressure. One of the great things about D-Jet.
The MPS mechanically compares intake air manifold pressure to atmospheric pressure to determine its sensor output value (inductance) which is delivered to the ECU as a factor in determining the fuel injection pulse width.
Posted by: mgphoto Jun 2 2022, 04:19 PM
You could add a potentiometer to the head temp sensor but you would need an AFR meter to track fuel ratios to prevent the engine from damage running lean, as stated the MPS is well suited to compensate for changes in altitude.
Posted by: 914sgofast2 Jun 2 2022, 08:19 PM
D-Jet automatically adjusts for differences in atmospheric pressure. One of the great things about D-Jet.
The MPS mechanically compares intake air manifold pressure to atmospheric pressure to determine its sensor output value (inductance) which is delivered to the ECU as a factor in determining the fuel injection pulse width.
WOW! That’s great to know. So if I drive up to Lake Tahoe from Sacramento then my 1.7L should make it?
Posted by: mgphoto Jun 2 2022, 10:30 PM
D-Jet automatically adjusts for differences in atmospheric pressure. One of the great things about D-Jet.
The MPS mechanically compares intake air manifold pressure to atmospheric pressure to determine its sensor output value (inductance) which is delivered to the ECU as a factor in determining the fuel injection pulse width.
WOW! That’s great to know. So if I drive up to Lake Tahoe from Sacramento then my 1.7L should make it?
Not a problem, it was built to do just that.
Posted by: TheCabinetmaker Jun 3 2022, 06:18 AM
Wow, another original owner! That makes maybe 7-8 of us.
Welcome aboard!
Owner since 73!
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