High Altitude Kit

[turdle]

Hi everyone. I own a 1977 VW Transporter Type II w/FI that I bought new here in Colorado. First I'd like to thank the community for all the helpful tips and help topics which has saved me many times! Next I need to ask about a required option that was mandatory in Colorado at the time of purchase. It is referred to as a "High Altitude Kit" which consists of a toggle switch mounted to the frame above the battery and wires which join the wiring harness near by. The switch is labeled High and Low but since the day I got it it never seemed to make a bit of difference in performance, millage, idle, etc. I always thought it was a scam and could never figure out what it was supposed to do. The various dealers I talked to couldn't ell me either. Any ideas?

[busdaddy]

Welcome,
This switch sounds interesting, could be something that alters the resistance of temp sensor 2. Pictures would be very helpful here, of the switch, where the wires from it go and the throttle body as well.
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[pb24ss]

Where in Colorado are you? Have you ever hooked up a timing light and flipped the switch and compared timing at idle and under load?

[busdaddy]

Hmmm....... may be somehow related to this:

[turdle]

[turdle]

[WhirledTraveller]

Karl's old posts state that USA ecu's don't have the circuitry to take advantage of this. However that would imply your ECU would have to have a different part # than a typical USA bus. Maybe you could pull your ECU and take a look at the part # and compare with the ratwell table here:

http://www.ratwell.com/technical/FISwap.html#ecu

Obviously if it does anything it must affect mixture only... there's no way for it to alter the timing which is controlled by vacuum and centrifugal force.
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1977 Westy, Automatic. Big Valve heads, CS Cam.

[SGKent]

aren't the European buses also T1 beetle FI motors in that era?

Peronally I would leave it alone. To me 5,000 feet is not high altitude. 12,000 feet is.

Think of all the buses that vacationed Yosemite, Lassen, Donner grade to Tahoe, Big Bear area in So Cal, peaks in Washington and Canada without one.
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"Most people don't know what they're doing, and a lot of them are really good at it." - George Carlin

[bretski]

Turdle,

If you need some help tuning, drop me a line. I'm in Fort Collins.

[raygreenwood]

High altitude adjusting without ECU circuitry can be done a few ways. Since high altitude typiclaly causes lean running...a "crude" method would be to add an inline variable resistor to either the CHT or ambient air temp sensor...or both...to richen the mixture up. Or...you could add an adjustable vacuum breaker to the fuel presure reg...and bleed small amounts of vacuum off to enrich at that point.

However....since main load adjustment on L-jet is done at the AFM flap....I have a fairly certain speculation that what may be happening in the ECU is that the input from the wiper arms on the flap is augmented or ballested within the ECU.....to take up for the fact that the now less dense air will move the flap less for each incoming air volume.

This is not much different than what D-jet did with the CO adjustment knob on the ECU in very late type and late 411/412 D-jet. Ray

[SGKent]

Hi Ray - My flight instructors always taught me to lean out the mixture at altitude because it went rich. Are you sure you don't want to reverse and go the other direction on this?
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"Most people don't know what they're doing, and a lot of them are really good at it." - George Carlin

[TomWesty]

I'm with Mr. Kent. Higher altitude means less dense air, meaning air to fuel ratio tips toward less air, same amount of fuel, thus richer.

[raygreenwood]

[SGKent]

[turdle]

Now that I created a thread about the high altitude switch and a discussion about timing came up, I always timed my bus at about 8 or 9 degrees BFTD and always ran pretty good. What input do you all have about timing a FI 2 liter at 5200 feet?

By the way.... While cleaning my engine I noticed the stickers on the engine lid. There was one I never paid munch attention to that states that the vehicle meets 1977 EPA guidelines for vehicle operation at high altitude. I'm not quite sure I want to pull the ECU to locate a number. If it works, don't mess with it.

[Tcash]

[SGKent]

here is a 1977 low altitude sticker. See how it compares. It sounds to me that the engine is tuned (CO etc) at the altitude it will be operated at.

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"Most people don't know what they're doing, and a lot of them are really good at it." - George Carlin

[Abscate]

Since there is an altitude discussion in another thread, a well moderated forum will update a pertinent thread on the topic and then link to the info in the new thread. That keeps information accessible and catalogued.
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[Tcash]

Out of the 1977 USA/Canada owners manual

[Tcash]