TheSamba.com :: View topic

Thu Apr 29, 2010 3:32 pm

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?

Thu Apr 29, 2010 3:41 pm

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.

Thu Apr 29, 2010 4:34 pm

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?

Thu Apr 29, 2010 4:47 pm

Hmmm....... may be somehow related to this:
Karl wrote: Those 2 wires coming out of the FI harness were on mid 76-77 buses. They are for an altitude switch on European buses; that was mounted above the ECU. Don't even think about putting a switch in..... USA ECU's do not have the circuitry in them. Either cut them off flush with the main harness or leave 'em alone.

I seem to answer this question once a year...... :)

http://www.thesamba.com/vw/forum/viewtopic.php?p=1563778&highlight=wires#1563778

http://www.thesamba.com/vw/forum/viewtopic.php?p=1038294&highlight=wires#1038294

http://www.thesamba.com/vw/forum/viewtopic.php?p=859254&highlight=wires#859254

http://www.type2.com/archive/type2/075066.html

http://www.type2.com/archive/type2/164626.html

http://www.type2.com/archive/type2/124257.html

Thu Apr 29, 2010 4:58 pm

busdaddy wrote: 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.

Thanks for the reply! The 1st pic shows the switch mounted just above the CU connector. The 2nd image shows how the leads join into the main wire harness that leads to the double relay mounted on the upper part of the left firewall. 3 wires branch off about mid engine and disappear under the air distribution box and I can wiggle them by grabbing a lead on the Temp Sensor II near Cylinder 3. It's all black magic!

Thu Apr 29, 2010 5:24 pm

pb24ss wrote: 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?

Hi pb24ss. I'm up in Fort Collins and I did hook up a timing light and no, it didn't make a difference either way. As I read the threads supplied by busdaddy, it sounds like this harness and switch were only on European models. Mine was bought in Greeley and came from Houston by train. I don't think it ever saw Europe except in manufacture. I looked at the original invoice and it stated the High Altitude kit was added.

Thu Apr 29, 2010 8:19 pm

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.

Thu Apr 29, 2010 9:34 pm

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.

Fri Apr 30, 2010 5:53 am

Turdle,

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

Fri Apr 30, 2010 12:17 pm

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

Fri Apr 30, 2010 9:39 pm

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?

Sat May 01, 2010 10:52 am

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.

Sat May 01, 2010 12:44 pm

SGKent wrote: 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?

Of course you are right! :lol: ...and I knew that ...but my "lysdexia" at the end of a long week caused me to lose my brain function.

I knew there was something wrong with the thought process when I mentioned the possibility of richening with the fuel pressure reg....just couldn't figure out why at the moment that would be totally unecessary.

However, the other three issues are correct. The thinner air causes less flap movement. A switch to feed that resposne into a loop with a potentiometer or a resistance multiplier would work fine (internally). Ballasting the CHT and ambient air temp sensor are still valid. Ray

Sat May 01, 2010 1:21 pm

Quote: Of course you are right! ...and I knew that ...but my "lysdexia" at the end of a long week caused me to lose my brain function.

I do that too and figured that is all it was. :)

Sun May 02, 2010 12:26 am

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.

Thu Sep 28, 2017 4:51 pm

VDubTech wrote: I didn't realize that you could order your Bus from the factory already tuned for high altitude applications. I brought home a '77 Westfalia hardtop camper this past weekend and noticed this on the emissions sticker on the underside of the engine lid, I never saw one like this before:

http://i33.photobucket.com/albums/d57/bigdog8176/white77072.jpg

Thu Sep 28, 2017 5:06 pm

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.

Thu Sep 28, 2017 6:22 pm

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.

Thu Sep 28, 2017 6:23 pm

Out of the 1977 USA/Canada owners manual

Thu Sep 28, 2017 6:29 pm

Abscate wrote: 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.
Nailed it. I was doing research for the other thread. I had hoped there was a way to trick the ECU into the High Altitude mode.
Unfortunately this will not help them.
Thank you
Tcash