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Thread: Back to my fuel vapor in the lines.

  1. #11
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    Quote Originally Posted by 55 Rescue Dog View Post
    There are countless oval track race cars out there running 600+HP, 7500+RPM engines, running a mandatory mechanical fuel pump in 90+ degree weather.
    Are they running the same pump gas with the same Reid vapor pressure as I get here?
    http://www.jmcampbell.com/tip-of-the...s-tvp-and-rvp/

  2. #12
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    Quote Originally Posted by 55 Tony View Post
    Are they running the same pump gas with the same Reid vapor pressure as I get here?
    http://www.jmcampbell.com/tip-of-the...s-tvp-and-rvp/
    I have no idea, but maybe get some good race gas and see if that makes a difference, or set it up for E85 and make even more power. I'm running 50% 110 octane gas with 87 unleaded and it works great. What do the race cars in your area run for fuel?
    Last edited by 55 Rescue Dog; 03-05-2018 at 04:15 PM.

  3. #13
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    Even my SBC powered drag Camaro uses a mech pump, However I do run a 400 gph electric on my BBC drag Camaro. It has a fuel cell in trunk and the pump is mounted below it with #10 an hose going forward. Not a very street friendly setup Electric pumps are pushers not pullers. This is why late model FI cars have pump in tank. .
    Last edited by markm; 03-05-2018 at 04:18 PM.

  4. #14
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    RescueD, I don't know where to find racing gas around here or anywhere. I guess I'd have to find a race track.
    Just so you got it straight, octane has nothing at all to do with the boiling point or reid vapor pressure of gasoline.
    Reid vapor pressure and fuel temperature (and the pressure or slight vacuum in fuel lines (before and after the pump)) have everything to do with the vapor point of gasoline and vapor lock. If I'm running pump gas and the pump is sucking hard enough to create a 1psi vacuum, that is a huge difference in the vapor pressure from the same fuel at 0 psi. It will vaporize at a lower temperature. You know how a sealed container of gas left to sit a while when opened will release fumes under pressure. The same thing happens in fuel lines. The most volatile ingredient in gas is usually butane and that will boil at a much lower temperature then most of the other ingredients. Just try to use a butane lighter below 32F. That is below its boiling point so it has no pressure to push vapor out to burn. Warm it in your hands or pocket and it literally boils inside the lighter and then vapor under pressure comes out to be ignited with a spark. Unfortunately an engine will not run on vapor. It needs atomized liquid. But they put butane in our gasoline. I hope that makes sense and is more or less correct.

  5. #15
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    Quote Originally Posted by markm View Post
    Even my SBC powered drag Camaro uses a mech pump, However I do run a 400 gph electric on my BBC drag Camaro. It has a fuel cell in trunk and the pump is mounted below it with #10 an hose going forward. Not a very street friendly setup Electric pumps are pushers not pullers. This is why late model FI cars have pump in tank. .
    And what is the Reid vapor pressure of the gasoline you run? Are you running pump gas?

  6. #16
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    I recently attended a Renegade race fuel seminar, they have a new Hotrod 93 fuel with zero alcohol I can buy it for 4.95 a gallon at the pump locally. My race cars live on their 110. if they ever have a program in your area I would encourage anyone to attend.
    https://www.renegaderacefuel.com/
    Last edited by markm; 03-05-2018 at 05:25 PM.

  7. #17
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    Quote Originally Posted by markm View Post
    I recently attended a Renegade race fuel seminar, they have a new Hotrod 93 fuel with zero alcohol I can buy it for 4.95 a gallon at the pump locally. My race cars live on their 110. if they ever have a program in your area I would encourage anyone to attend.
    https://www.renegaderacefuel.com/
    That seminar sound interesting. Maybe I can call them and ask what their Reid vapor pressure value is. Do you know what it is for their 110?

    Edit: I just emailed them asking about the vapor pressure.
    Last edited by 55 Tony; 03-06-2018 at 04:58 AM.
    Tony

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  8. #18
    Registered Member chasracer's Avatar
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    I am stepping in here and not fully aware of your parts and combo - so bear with me please.

    I think the perfect combination for a slightly warmed up street combination is a stock type fuel pump that is of hi-performance nature - I have used the Holley brand in the past but I have no idea of whether those are good now or not - things change. I am sure there are others out there that provide plenty of pressure and volume. To lessen the demands on the pulling side of the pump, I have used the small 12v electric pumps that you can find at almost any automotive parts shop or online. These only provide about 4-4.5 pounds of pressure but they are quiet and are very good at keeping fuel at the stock type pump. If pump noise is an issue, consider mounting the pump to the frame with a thick piece of rubber as an insulator. The sidewall of an old tire is a good source for the rubber piece. (BTW - this rubber also works nicely for a stock body mount isolator) Another issue that I see on a LOT of cars intended for mostly street use is the killer fuel line size. I understand that there are plenty of people running 1/2" or larger fuel lines without any problems but the original Hemi powered Chrysler cars with dual 4 barrel carbs only had a 3/8" feed line and that was considered "big" back then. The larger that line gets, the harder it is to push fuel through it and unless you are supporting 600+ horsepower that needs that kind of fuel volume it can be another item that is causing issues. The type of fuel that we can purchase at the pumps today is completely different from what we purchased in the mid-70's. To make up for the lack of lead in the fuel as it relates to octane, fuels today are what you call aromatic. These chemicals increase the octane levels but they evaporate quickly and are very susceptible to vapor lock problems in older vehicles. A number of people with stock '55-'57 Chevys have a hard time with starting after letting the car sit for a few days. The fuel has evaporated via the vent tube(s) on the carburetor and the accelerator pump fuel level will normally be low too. A bit of cranking refills the carb and they start. Old lead based fuel did not do this and while you could encounter vapor lock, it was usually question of the fuel line being too close to a heat source. Also, these new fuels are part of the reason that we now have sealed gas tank caps and fuel injectors instead of carburetors. One last item to mention is the fuel tank cap - I honestly do not remember the changeover year, but at least prior to the mid-70's, fuel tank caps were of a vented type. Putting a non-vented cap on these tanks will cause fuel delivery issues too.
    Last edited by chasracer; 03-06-2018 at 05:35 AM.
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  9. #19
    Registered Member chevynut's Avatar
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    Like I said in the prior thread (don't know why you didn't just keep that one ) IF YOUR PUMP IS WORKING CORRECTLY, I believe you have a restriction in your fuel line between the mechanical pump and the tank. Also, your fuel bypass in the filter isn't helping the situation because if I understand it correctly, it causes the pump to have to pull more fuel from the tank than the engine needs and returns the excess to the tank. As it pulls more fuel, the pressure in the line drops.

    The pump you're using should provide more than enough fuel for your engine at full-throttle, if it's working as it's supposed to.

    To prove this, you could put a small gasoline container in your engine compartment temporarily and feed the pump from that. Then try a full-throttle pass to see if the problem goes away.
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  10. #20
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    There is no restriction in the fuel line. When I was messing with the pump the last time and took the tank line off the pump, the fuel ran out since the tank was almost full. I put a container under it and verified that it kept running and wasn't just what was in the hose. I had to lift it higher than the tank to stop it.

    I did remove the bypass filter and replaced it with a plastic one so I could see if vapor was coming into the filter. Although I had the same problem before the bypass was installed and the problem actually lessened with the bypass filter. I have not had a chance to test it due to rain.

    I am pretty certain the pump works fine. It had the problem from the time I got it on the road and since then the pump and regulator has been changed. I can't put the old pump back on because I cracked the housing from turning the fitting too tight.

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