Saturday, August 6, 2011

Multivariate Vapor Lock Equation

As I've posted through this blog, we have had a few technical setbacks, and they held us up two extra days in Albuquerque. To be fair, because of the problems I got to Albuquerque one day early so I could work on the car with Gary Phipps, we intended to stay one night anyhow, so the three nights we spent there ended up meaning that we left one day late. We solved all the problems those days with the exception of the vapor lock. The vapor lock is something we have to live with. It has humbled me and the car to the point that I now admit there are limits to the capabilities of the car given the quality of today's fuel mixtures. I am fully confident I would not be having these problems if I could use leaded fuel from the 1950s. That said, here is the discussion of the multivariate vapor lock equation...

There are several things that induce vapor lock in the car. These variables include temperature, altitude, how hard I'm running the car, and duration of running the car. I'm trying to visualize some surface graphic with green (good), yellow (getting close), and red (sure vapor lock) and drive below the limits of the red. I've learned that if the temperature is in the 80s I probably won't have vapor lock issues, but if it is in the 90s I probably will. The question is "When?" How much do I have to back off in order to extend our trip a few extra miles. An example of the calculus I was pondering today when it was 95 degrees out was, "I'd rather eat lunch right here, but if I do my next leg will be too long and I'll have to stop for a vapor lock cooldown. But if I keep going, can I make it to the park? If I make it to the park then I know the next leg will be short enough that we'll be safe, and when we get to the park we can take at least an hour break for lunch and some sightseeing in the visitor center and the overlooks." As it turned out, we almost made it to the park, which was very discouraging at the time. We missed it by 10 miles. Instead, we had to hang out at a Navajo trading post for 45 minutes before driving the last 10 miles and taking that long hour break.

Tomorrow the calculus has me thinking the best thing to do would be to leave at 6am so we can get a solid 5 hours of driving in before we start worrying about vapor lock. So now I'm looking at the map and saying, "Where will I be after 5 hours of driving tomorrow?" In an ideal world, we'd find someplace really neat at 11:00 or 11:30am, then take a 4-5 hour break there, then get back in the car for a couple more hours of driving. But I can't find anything interesting -- we'll be approaching the Mojave Desert. If there's next to nothing there, maybe we'll just drive until lunch, then alternate 20-30 minute driving stints and hour breaks through the heat of the day. We'll be on Historic Route 66 for much/all of that, so there should be things to see.

4 comments:

  1. You are already on the road so don't know when you will see this. The Mojave is geologically interesting but devoid of most anything else. Out of Needles there is a looong uphill to the moonscape of the Mojave. The other side is Barstow (in a drier desert than ABQ) which is a good 5 hours away from Williams if you stick to I-40. Since you are on old 66 it will take longer. Gas stations can be 100 miles apart in the Mojave: check your gauge. Because of the heat soak, stopping in Needles is not encouraged even though its to be a 'cooler' 108F today.

    I have my added pump in place with transparent lines and am analyzing data; I have duplicated your problem. Unfortunately, there is nothing I can tell you to do differently. The problem is getting fuel TO the pump(s). As it exits a 106F tank its already not entirely liquid. Actually what you/we need is the original UNLEADED petrol from the 30s.

    gsp

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  2. aren't there lead additives you can buy? would that help the problem?

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  3. Sorry to hear that you have the same problem, but hopefully you won't have the same symptoms. I don't think I would have made it much farther after Needles, but even after resting I couldn't make it 38 miles without a stop on the side of the road. I then spent 5.5 hours at the next gas station in Fenner waiting until 8pm to leave (when it was cooler).

    See you in a few days...!

    Bob, I'm not sure if that would help the problem. Taking ethanol out probably would. I could use lead additive, and any other number of concoction additives....not sure what I should do. :-(

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  4. Matt,
    They still sell leaded gas from the 1950's. It is called 100LL and just about every general aviation airport has it. You might try looking for the local airports on your way back across the desert and fill up there. Not cheap, but certainly less prone to vapor lock.

    Bruce

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