Aloha, I understand this carb is harder to tune and is best for constant WOT and uses a lot of gas. Maybe you will use twice the amount of gas. Frank
More like Tripple.
Not suited for streetuse.
Bram: Why does it take much more fuel than regular "floater" carbs?
Cause exessive fuel would mean a drop in power, and I dont think you would drive like that.
Or is it on lower rpm and throttle opening that the engine runs very rich?
And another question, does these cart carbs carry a small amount of fuel or does the fuel go directly from the pump to the jets?
What I am wondering is if the carb cuts the fuel delivery to the air the moment the pump stops pumping or if you could drive a short period with fuel left in the carb (like on floater carbs when you cut the fuel delivery to the float bowl).
So if you cut the fuel delivery to the carb at WOT will the engine die instantly or will it run for a few seconds more (risk leaning under that period)?
It will run a few seconds, because there is fuel in the fuel line.
These carbs have a membrane, and that's why they need vacuum.
Maybe I'm going far off topic now, if so please say so...
What I want is to cut the fuel delivery to the air right off, with maybe a max of half a second where it continues to deliver fuel.
So if you cut the fuel on the fuel line right in front of the carb fuel inlet and cut the vacuum too, will it still run for a few seconds on fuel still present within the carb or will the engine die instantly?
I'm trying to find a way to make two separate fuel systems which you can very quickly switch between during the ride.
But that also means that the primary fuel system (carb maybe) will have to begin working the moment you switch from the secondary fuel system.
So far the only way I've come up with is EFI with two separate injectors, but that would be too hard to make I think...
That might work, if the valves to the different fuel lines are positioned directly in front of the carb inlet it might work cause then the fuels won't have much time to blend with each other.
The extra amount of secondary fuel needed could be injected using some kind of injection system.
With a membrane carb that might work, but I wonder how well the parts handles methanol and nitromethane.
I am more fond of floater carbs, but the float bowl carries too much fuel to allow a quick switch between the fuels without allowing the fuels to blend.
Maybe I could decrease the volume in the floatbowl and use a membrane fuel pump to keep the fuel level right?
Btw Bram, do you still use your membrane carb or do you use a floater carb now?
Bram: okey, was the tm28ss better?
well, because methanol and nitromethane carries a fair amount of more oxygen than ethanol. When you engage the secondary fuel system that wouldnt matter much, it would just run rich for a short period of time cause the engine keeps getting ethanol.
But when you disengage the secondary fuel system the spray of extra secondary fuel stops, but the carb still has a small amount of secandary fuel inside itself that will cause it to lean off in a very not so good way :/
Hopefully it leans so much that the engine cant ignite that fuel, but you can never know...
Even if it's in a very short period of time I don't want to drive super lean at high rpm...
Maybe should make the disengage of the secondary fuel injection delayed by a second or so, so it will richen the mixture the moment you switch back to the primary fuel...
StepVino: Nope, but I know what I will have to do, pour a lot more fuel into the engine, maybe twice as much as now (and now on ethanol i drive with around 45% more fuel than on gasoline)
The methanol and nitromethane both burns very slowly (on rich mixtures which I will run on) so I don't have to bother about the ignition system more than I have to make sure it can ignite this fairly wet mixture.
Because of the higher energy released I will lower the compression ratio and take a little higher squish just to be on the safe side.
The thing I don't know is if things in the carb can handle the fuel or not, but that maybe don't make much difference when it's only going to be there in a very short time...