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On 24 Feb 2003 at 19:58, Keith Park wrote: > ! I felt much better after a nice calm "Your Fine" from Jim Adney. but > when he blew past me with an AUTOMATIC I started feeling that all was not > well again. Well, it was a 69 FI AT compared to your hybrid 69/73 MT FI. I just don't think you can expect good results under all conditions while mixing parts from different families. Plus the 73 system is the most smogged of all the FI years. > This created a condition that made the pressure sensor never give the > control unit the signal for the throttle I desired. And of course my > vacuum gauge is measuring vacuum as compared to the atmosphere AT > ALTITUDE so is giving very misleading readings. Have I got this right > Jim? You need to keep in mind that this is the same for any normally aspirated engine. Only a turbo will still get all the air it wants at altitude. The rest of us will always see a loss of power here. You can't make up for less air by adding more gasoline. > The result of all this was a slow go but EXCELLENT gas mileage, and I didn't > seem to have any problems with the poor quality western gas. I'm set up to > use 92 Octane with 7.7:1 and my FI setup. but never noticed any knocking or > pinging with the 89. Running at altitude will have the unexpected benefit of less pumping loss. This is the power wasted in pulling the air in thru the intake system. Since you are forced to run with the throttle farther open than normal there is less restriction in the intake and less pressure drop between the outside and the combustion chamber. This improves the efficiency, even though you aren't getting much power out of it. > I could keep the pedal mashed at 35 in third > (about 2500RPM) and the engine would be smooth and gutless but nice and > cool. with outside temps around 50F. When I downshifted to second to get > more power and got the RPM up for more power the oil temp would suddenly > shoot up 30degrees or more, I'm surprised. I would have expected an increase in heat produced, right along with the greater power output, but I thought the greater fan speed would have taken care of this. Perhaps the fan loses effectiveness at lower speeds at altitude. I don't have any idea how this works. > I remember Shad Laws saying that the head temperature would skyrocket > when floored at altitude even though the oil temperature was low. but I > didn't ever hear any knocking or see any sign of it. I Don't have any > head temp gauges though Remember that knock is a compression phenomena, not really caused by head temp. It happens too fast for the mixture to be heated by the head. At altitude it is even harder to get enough air in there to cause knock conditions. > Lastly, and as Jim A will attest, I spend too much time looking at my > gauges. but I just cant help it! Part of it is Psychological. I changed the > Tee that the temp gauge is mounted on from Cast iron to Brass, which moved > temp readings up about 25F and made for much quicker response. Being alone with an older engine is certainly harder on your nerves. I don't understand the cast iron to brass change since those two have about the same thermal conductivity; any chance the brass one was shorter or thicker wall? Here's something to ponder: What if the brass part was actually thinner wall (because brass is more expensive) and therefore less thermally conductive? In that case, the higher temp might be due to the fact that it picks up more heat from the air around it and is less able to shed that heat into the oil. It would be interesting to measure the temp of the air around the oil sensor. Only then would we know which way the heat is flowing. I've always felt that a good oil sensor should work via a probe that actually sticks down into the oil cooler where it is bathed in flowing, rather than stagnant, oil. -- ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA ******************************* ------------------------------------------------------------------- List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org