Mixture Control Indicator

Discussion in 'Half VW' started by N8053H, Aug 17, 2013.

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  1. Aug 29, 2013 #21

    Pops

    Pops

    Pops

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    First of all, of course you need a CHT, EGT. Steve at Great Plains also recommends a Manifold Pressure Gauge and have the pitch of the prop for 21" of manifold pressure at cruise rpm. A lot of pilots flying behind VW engines are running the engine at to high of manifold pressure that helps cause the high CHT and Oil temps.

    I do not want FI for my VW, also I do not want a starter, alt, battery, etc. All of that adds up to a lot of weight and the more you have, the more you have to go wrong or break. Yes the FI will be a little more fuel efficient and a little more power, but at 2.9 gph and 12-1 HP to weight ratio at GW, fuel is not a factor and I have more than enough power with 1200-1300 fpm climb. If its not there, it light, 100% dependable, cost nothing. I'll take light and simple , Thank You.
    Sort of like me :) Dan
     
    Last edited: Aug 29, 2013
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  2. Aug 29, 2013 #22

    Jay Kempf

    Jay Kempf

    Jay Kempf

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    This question keeps coming up. Here's the easy way to think of it. If an engine management system can deal with the difference between a heavily turbocharged and normally aspirated version of the same engine shouldn't it follow that it should be able to handle a little change in altitude. Turbos are huge changes in density by comparison. Yes, you can customize the fuel air mix at certain RPMs but that is a target. The automatic system will trim to keep the mixture set across the entire RPM range while adjusting for density. Modern systems can adjust for Manifold Absolute Pressure (MAP sensor), Mass Air Flow (MAF sensor), and O2 percentage (O2 sensor), as well as boost, knock sensors, timing, and cylinder head temps if you like. The latest stuff I have seen can incorporate dual spark plug setups, plus there are a ton of other spare inputs and the code is open source if you want to overgeek yourself. And all that stuff can be reported in real time or collected history if you like. The reason computers have taken over is two fold: because they came available, and because we are fighting a battle of tail pipe emissions. The battle over emissions required better control of the fuel flow during all kinds of modes to pass emissions tests on dynos so that autos could be certified. Carburetors couldn't do it. The first rudimentary mechanical fuel injections systems were better but were a pain in the neck. So computers have made better and more accurate control of fuel flow to lower emissions meaning they control fuel closer to optimum at all times. That means they are better at managing the engine than you are.TDI is another level of control of combustion beyond intake injection. It is revolutionary. I am hoping that the aftermarket starts providing some sort of kit. Tough design problem though. it would almost require a spark plug injector combination retrofit component. I am sure someone is scratching their head somewhere trying to figure that out. Hope they succeed.

    Kewl, when you go advanced during an edit it takes out all the carriage returns. Never happened to me before.
     
  3. Aug 30, 2013 #23

    Topaz

    Topaz

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    Well, we're definitely far beyond the limits of my knowledge here. The only fuel-injection system I've actually worked on is one of those "rudimentary mechanical fuel injection systems" - or rather, very close to one (electrically fired independent injection, but mechanically timed): A 1973 Porsche D-Jetronic system.

    This stuff seems a little more advanced than that. ;) Thanks for the information. Obviously the altitude question isn't really relevant anymore, or so it seems.

    I'm more of a mind with Pops on this one, though. I really want dirt-simple, and don't want to have to mess with adapting a system. No prejudice against what you're talking about at all - sounds like there's a lot of control available there, and a lot of optimization possible. If/when someone comes up with a bolt-on system for an aero-converted VW and it's at a reasonable price, I'll consider it when the time comes.

    Chrome. I'm not seeing that problem at all. I do have a weird issue with italics, bold, etc., but it's manageable.
     
  4. Aug 30, 2013 #24

    Turd Ferguson

    Turd Ferguson

    Turd Ferguson

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    x2.
     
  5. Aug 30, 2013 #25

    Jay Kempf

    Jay Kempf

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    Funny thing is my Porsche is newer than yours by a few years but it is completely mechanical other than some heaters that provide warmup functions. I am one with that system but I would never build a new engine for a new application using that system. It is VERY Similar to the original Bendix system that I have on my io 470. And I wouldn't use that system either on a new experimental engine build. There are just too many things you can do to get more efficiency and reliability out of an engine with the new FI systems.
     
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  6. Oct 8, 2013 #26

    buzzypeterson

    buzzypeterson

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    I had a small vw on a himax that ran perfect the first year I got it then started fouling plugs. I never would have believed it, she had lots of power in flight and ran good for the most part.... only issue was it took a lot of work to start. I ended up rebuilding and found out I had a few cracked rings. Got new cylinders on but it still fouling. Messed around for countless hours with carbs, bought an aerocarb and it ran better but I had to mess around with the carb so much, at idle the thing would load up and it was lean at the upper end. a friend was getting rid of a mag so I bought it just because I knew it was newer than mine. and wouldn't you know first pull she ran, can't remember touching the mixture after that.

    On my latest engine we couldn't get it to run right.. we tried I swear to you over 10 carbs because the mag we were using was recently rebuilt so we thought "it can't be that". The spark was nice and bright white. I was 100% sure it wasn't spark. We got so sick of trying every different carb under the sun... some updraft, some down..... and having the thing clunk off. we figured last thing to do would be to hook up a new stock distributor and coil and if that didn't work we were in deep trouble. Hard to believe but first pull on the prop she ran perfect. even though we had spark and it was timed right it wasn't hot enough. I bought one of those army surplus mags for the 4A-084 for about 100 bucks.

    Not trying to argue with you but if you are fouling plugs look at your spark. if it is hard to start by hand your impulse coupling is going but that doesn't necessarily tell you much, if it is loading up when you pull it back at low throttle settings and you have a regular float carb you have a magneto that isn't hot enough. You should not have to adjust mixture in flight at all. this lean to peak stuff is great for high performance airplanes but I don't think they are talking to you and me with our'e vw's
     
    Dan Thomas and cluttonfred like this.

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