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Automotive/High altitude driving

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Expert: - 8/5/2007


Question
I own a studebaker pickup with the champion flathead 6. I want to take a trip to the rockies, 10K+ feet. Should I install bigger or smaller jets in the carb? Can you express in terms of % how much horsepower is lost for every 1000ft of elevation?  I plan on towing a trailer.

Answer
I would think that a better idea would be to leave the main jets (or jet, in this case, I believe) alone and consider instead opting for a power valve that is calibrated for high altitude driving.  

A high-altitude calibrated power valve will provide fuel enrichment for less drop in manifold vacuum than will a sea-level calibrated power valve.  Inasmuch as your vehicle is a truck, with a trailer to haul, a two-stage power valve may be an even better choice.  Two-stage valves provide the enrichment in two steps, the first being partial enrichment before the vacuum drops too far.

In both cases, under normal cruising manifold vacuum, your properly-sized main jets will provide the baseline near-stoichiometric air/fuel ratio for efficient and clean running.

As to the percent power loss per kilofeet of altitude, I would have to look that up, and you could do that just as easily as I can.  There are variables, involved - whether or not a vehicle is turbocharged, for example.  In general, turbocharged engines lose about half the power that normally-aspirated engines lose.

I have a 351W in my E250 class-B motorhome conversion, converted by myself to Holley 4160 operation in 1992 to improve both the vehicle's economy in around-town driving and to get more power for the over-the-road and mountain driving in BC.  My list 0-80452 carburetor uses a two-stage valve, and works well in all modes, and continues to provide excellent emissions performance in the annual ASM2525 AirCare test, so long as I stay on top of any potential vacuum leaks!  At some point, I may well upgrade to a ProJection throttle-body EFI system - or perhaps even a new power plant (diesel) - or maybe even a new truck some decade along, but the system suits its purposes well for now.

Good luck with the trip ... EGK

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Ernest (Ernie) Kenward

Expertise

The challenges I most enjoy are thoughtful technical questions of a trouble-shooting nature in both electrical, power electronic and mechanical systems, mainly automotive but also machine control and small-machine PLC applications. Please note, however, that I am NOT a walking shop manual! I DO, however, make it a point to have those manuals and other service literature for those vehicles I DO own, and highly recommend that anyone serious about maintenance or modification of their vehicles do the same; MOST of your answers WILL be found there. For that matter, I do NOT go out of my way to acquire shop manuals for any vehicle I do NOT own! That being the case, any general query to me along the lines of "What is the meaning of this code read from the ECU of my 2015 XYZ?" or "Where is the fuse for the windshield washer pump found?" (try your car's electrical distribution panel for a start!) will not go far. What I do offer is a pretty good collection of literature, insights and hands-on experience with 1950s to 1980's Ford products (plus a developing database of information and practice with the Mercedes diesel cars), along with an engineering perspective and the ability to design and implement custom control, electrical and mechanical subsystems for vehicles. For that reason, I am happy to make my thoughts and efforts available to those who are of like mind and/or are seriously making a point of learning about their vehicles. Use the Opportunity to Learn!

Experience

A key skill in my work and hobby pursuits both is STRATEGIC TROUBLESHOOTING. I am a senior instructor in Electrical Engineering Technology at a leading Canadian polytechnic, my areas being Electrical Power and Industrial Control, electrical and electronics design and manufacturing, and AutoCAD and related CAD/CAE software - plus equipment problem-solving and new equipment design and prototyping. Hobby-wise, I have 30-plus years of experience in auto restoration, mostly in electrical and mechanical systems. Ongoing projects include a 1959 Edsel Corsair, my 1978 Ford E250 class-B motorhome conversion, and the care and upkeep of my Mercedes 300CD. My vehicles become engineering test beds for electrical and mechanical upgrades as ideas present themselves. This includes the design and production of circuit boards to restore or enhance features for which no OEM replacement parts are obtainable, or where better specifications or reliability can be had via newer concepts. Regarding the E250 RV conversion, I designed and continue to revise a custom power distribution system, managed by a Programmable Controller (PLC); this has made most revisions as easy as uploading new firmware as I develop it. The "mini" PLC is a powerful device for custom automotive control systems. One good example (there are many) would be the Moeller "Easy Relay"; these offer a wealth of control, monitoring and variable-and-status display options for such projects. A good example project which has worked well is that one for my RV noted above, which has been on the job - revised in firmware only - for a decade now. It is a load management and charging control system to avoid the sulfation-induced early failure that often befalls deep-cycle batteries used in RV power applications. The battery installed in 2003 lasted long enough to more tnan pay for the PLC that contributed to its longer life ... and the PLC will be there for the next battery as well!

Organizations
IEEE - senior member ... past WCC Student Activities; SME - senior member ... past chair, greater Vancouver chapter chair 318; Edsel Owners' Club - have served in various capacities on chapter executive during seventies; have been Power and Driveline resource on the Edsel Owners' Club "E-team" for more than a decade.

Education/Credentials
Graduate of UBC

Awards and Honors
Certificates of appreciation from IEEE and SME for work in student and chapter activities

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