Texas Two Step Taco

John Murray

Been Around the Block
I watched a friend run a 6.7 in the 1/8th on alky with only one cylinder the other night because the other two cylinders were fat and wouldn’t fire. This was with a 1.7 60’ time. I was reading your tutorial while at the track and was experiencing it in real time. We learned you can’t let the bike sit and idle because it floods the case because there is no load on the engine. Teazer has mentioned an anti knock detection device...I am wondering if that is a good investment.


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You have to really try to make alky det. Don't do anything silly and you'll be fine.
 

Sotaro

New Member
Using John’s calculations with a target of 60 whp. I wonder if this calculation should use BHP or WHP?

Let’s say it’s WHP.

16 x 60 whp = 960 ml per minute of Methanol


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I thought 960 ml/min a very large flow rate. As a contrast, using gasoline of average density, 0.74 grams per milliliter in a 4 stroke engine of average efficiency where the engine used 0.5 lbs of petrol/horsepower/hour:
0.5 pounds/hp hr x454 grams/pound x ml/0.74 grams x hour/60 min x 60 horsepower = 307 ml/min. So, using methanol in a two stroke requires 3.1x more fuel flow. I don't know anything about methanol in two strokes, but that factor of 3.1 seems like a lot. I am glad my car has a four stroke.
 

Texasstar

Can't is a four letter dirty word
I thought 960 ml/min a very large flow rate. As a contrast, using gasoline of average density, 0.74 grams per milliliter in a 4 stroke engine of average efficiency where the engine used 0.5 lbs of petrol/horsepower/hour:
0.5 pounds/hp hr x454 grams/pound x ml/0.74 grams x hour/60 min x 60 horsepower = 307 ml/min. So, using methanol in a two stroke requires 3.1x more fuel flow. I don't know anything about methanol in two strokes, but that factor of 3.1 seems like a lot. I am glad my car has a four stroke.

Well they say it should be 2.3X on methanol but I can tell you by experience that at 300ml/min we were fuel starved on c12. It wasn’t until we got 500 ml/min that we fixed our fuel starvation issues. Here is what the fuel looks like when revving and the tank is subjected to resonance. 3.1 seems to leave us some wiggle room...especially if we can find some more torque.

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teazer

Over 10,000 Posts
DTT BOTM WINNER
I thought 960 ml/min a very large flow rate. As a contrast, using gasoline of average density, 0.74 grams per milliliter in a 4 stroke engine of average efficiency where the engine used 0.5 lbs of petrol/horsepower/hour:
0.5 pounds/hp hr x454 grams/pound x ml/0.74 grams x hour/60 min x 60 horsepower = 307 ml/min. So, using methanol in a two stroke requires 3.1x more fuel flow. I don't know anything about methanol in two strokes, but that factor of 3.1 seems like a lot. I am glad my car has a four stroke.
Rule of thumb for a two stroke is 6.5 pounds of gas per HP hour at its most efficient.

But the issue with alcohol (and there are many) is getting enough flow. We used #400-500 main jets with Methanol compared to lower than 200 on gas and the pump and fuel tap and float valve all need to be upsized as do all the jets.

Methanol has a lower heating value of 56,562 BTU/pound compared to 114,761 for gas, so right there needs a flow increase of roughly 2:1 just to get the same heat energy, but that's not the real concern.

Let's tackle that from the other end. Let's say our motor makes 60 crank HP and burns 6.5 pounds of fuel at say 14.7:1. That means it's sucking it roughly 390 pounds of fuel and 5733 pounds of air.

That amount of air at an Air: fuel ration of 6.45 would burn 888 pounds of methanol and at say 4:1, would burn 1,433 pounds of methanol which is closer to 4 times as much methanol as gasoline.

Those calculations are just to get our brains into gear here.

So we know it will need a lot more fuel. Going back to stoichiometric numbers for a moment, Methanol uses 2.3 times as much methanol than gasoline. and 2.3 times as much fuel adds roughly 13% more heat energy.

The real reasons to use methanol is that it can withstand much higher compression than most gasoline except perhaps Q16 which is over 116 octane. And that's where the extra power comes from on a boosted 4 stroke. increase compression, pour in more fuel and see the HP numbers rise.

What also happens is that methanol has a higher latent heat of vaporization which is the energy required to change it from liquid state to gaseous state. It means that a methanol burning motor has colder denser air and that means more oxygen which may be one reason that it like to be richer than stoich. Because more oxygen molecules need more fuel compared to gas, so extra fuel and extra oxygen all help to make more power.

Except that all the fuel still only burns on the surface of the droplets so we need to atomize the fuel into smaller droplets and our old style carbs don't do a great job at that, so we end up with raw fuel going down the pipe, so the pipe is cold and no longer the tuned length.

Time to fit fuel injection and programmable ignition and to pre-book time at the local mental health facility. :)

It's all doable but takes time and effort to get it right. I am often reminded that the 1320 times on my bike are a function of the ability, or lack thereof, of the rider and that's me. In an 1/8th mile, launch technique is more important than the last extra HP and pipe temperature is probably more of an issue than we might expect.

Keep having fun and keep us informed.
 

Texasstar

Can't is a four letter dirty word
Rule of thumb for a two stroke is 6.5 pounds of gas per HP hour at its most efficient.

But the issue with alcohol (and there are many) is getting enough flow. We used #400-500 main jets with Methanol compared to lower than 200 on gas and the pump and fuel tap and float valve all need to be upsized as do all the jets.

Methanol has a lower heating value of 56,562 BTU/pound compared to 114,761 for gas, so right there needs a flow increase of roughly 2:1 just to get the same heat energy, but that's not the real concern.

Let's tackle that from the other end. Let's say our motor makes 60 crank HP and burns 6.5 pounds of fuel at say 14.7:1. That means it's sucking it roughly 390 pounds of fuel and 5733 pounds of air.

That amount of air at an Air: fuel ration of 6.45 would burn 888 pounds of methanol and at say 4:1, would burn 1,433 pounds of methanol which is closer to 4 times as much methanol as gasoline.

Those calculations are just to get our brains into gear here.

So we know it will need a lot more fuel. Going back to stoichiometric numbers for a moment, Methanol uses 2.3 times as much methanol than gasoline. and 2.3 times as much fuel adds roughly 13% more heat energy.

The real reasons to use methanol is that it can withstand much higher compression than most gasoline except perhaps Q16 which is over 116 octane. And that's where the extra power comes from on a boosted 4 stroke. increase compression, pour in more fuel and see the HP numbers rise.

What also happens is that methanol has a higher latent heat of vaporization which is the energy required to change it from liquid state to gaseous state. It means that a methanol burning motor has colder denser air and that means more oxygen which may be one reason that it like to be richer than stoich. Because more oxygen molecules need more fuel compared to gas, so extra fuel and extra oxygen all help to make more power.

Except that all the fuel still only burns on the surface of the droplets so we need to atomize the fuel into smaller droplets and our old style carbs don't do a great job at that, so we end up with raw fuel going down the pipe, so the pipe is cold and no longer the tuned length.

Time to fit fuel injection and programmable ignition and to pre-book time at the local mental health facility. :)

It's all doable but takes time and effort to get it right. I am often reminded that the 1320 times on my bike are a function of the ability, or lack thereof, of the rider and that's me. In an 1/8th mile, launch technique is more important than the last extra HP and pipe temperature is probably more of an issue than we might expect.

Keep having fun and keep us informed.

Speaking of the chamber do we need to revise our last chamber numbers through Mota for Methanol? Can Methanol be used to tune a pipe by cooling it and then use timing to bring the heat back up where we want it? Team Old Age and Treachery is Back...just wait till you see what our mad scientist from down under has planned.


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teazer

Over 10,000 Posts
DTT BOTM WINNER
good question. I don't know if anyone has a different chamber shape that works better with methanol. You could test different shapes to see and maybe tighten the squish slightly to get the fuel vaporized and turbulent.

For the pipe, test the EGT to see what the difference is and test it under load to see if retarding it to burn more fuel in the pipe makes enough difference.

It comes down to test, test and test some more.
 

Sotaro

New Member
Rule of thumb for a two stroke is 6.5 pounds of gas per HP hour at its most efficient.

Let's tackle that from the other end. Let's say our motor makes 60 crank HP and burns 6.5 pounds of fuel at say 14.7:1. That means it's sucking it roughly 390 pounds of fuel and 5733 pounds of air.

That amount of air at an Air: fuel ration of 6.45 would burn 888 pounds of methanol and at say 4:1, would burn 1,433 pounds of methanol which is closer to 4 times as much methanol as gasoline.
Teazer, I like your thinking. You are off by one decimal point. 0.65 pounds of gasoline per horsepower hour is reasonable. 6.5 pounds of gasoline is not. It is about 1 US gallon of gasoline. You would think you were leaking gasoline out of every orifice if that were your brake specific fuel consumption. I did look up in Wikipedia which showed 0.7 for a piston port two stroke and 0.45 for a lot of four strokes.
 

John Murray

Been Around the Block
Except that all the fuel still only burns on the surface of the droplets so we need to atomize the fuel into smaller droplets and our old style carbs don't do a great job at that, so we end up with raw fuel going down the pipe, so the pipe is cold and no longer the tuned length.

Time to fit fuel injection and programmable ignition and to pre-book time at the local mental health facility. :)

I dunno, sometimes I think these projects are the only things keeping me out of those facilities.

A good carburetor is capable of atomization every bit as good as an injector, sometimes better. I spent a few months in 2020 testing and optimising injection, and it wasn't until I added an upstream nozzle I was able to exactly equal what the carburetor made. It worked fine but had no compelling advantages so was binned. The engine doesn't care what device supplies the fuel but it does care about where the fuel was introduced. See this vid for more if you're interested:
I'd leave the pipe as is for the time being just to get a baseline, though I'd up the comp to somewhere around 14.5 - 15:1. Fuel flow is easy, just give it what it wants. The only opinion that matters is that of Mr Torque Gauge. Of course, do a sanity check on fuel flow and timing after testing but the dyno will get the fueling in the ballpark in no time.
 

Texasstar

Can't is a four letter dirty word
Story of my life I just keep looking for a bigger petcock. Joseph said to add more cowbell, I mean more fuel. This guy is smooth on a 4 speed quad. Who wants to guess what kind of tranny this guy has. I can tell you he built this quad just to silence a troll. Lol. There are doers of the word and not hearers only.
 

Texasstar

Can't is a four letter dirty word
Just to recap how far we have come in 20 runs at the drag strip. The dyno runs of our beloved taco. The Bultaco Montadero with a Bandido.

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Texasstar

Can't is a four letter dirty word
I dunno, sometimes I think these projects are the only things keeping me out of those facilities.

A good carburetor is capable of atomization every bit as good as an injector, sometimes better. I spent a few months in 2020 testing and optimising injection, and it wasn't until I added an upstream nozzle I was able to exactly equal what the carburetor made. It worked fine but had no compelling advantages so was binned. The engine doesn't care what device supplies the fuel but it does care about where the fuel was introduced. See this vid for more if you're interested:
I'd leave the pipe as is for the time being just to get a baseline, though I'd up the comp to somewhere around 14.5 - 15:1. Fuel flow is easy, just give it what it wants. The only opinion that matters is that of Mr Torque Gauge. Of course, do a sanity check on fuel flow and timing after testing but the dyno will get the fueling in the ballpark in no time.

John are you picking up a pulse with one of these hoses for a fuel pump?
IMG_6372.jpg



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John Murray

Been Around the Block
John are you picking up a pulse with one of these hoses for a fuel pump? View attachment 235541


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No, that engine ran a tm38 carb and was only 50 something hp from memory. Gravity feed via a pair of ballvalve type fuel taps was sufficient. Motorcycle carbs can't handle any pump pressure, the pressure overcomes the float valve and they overflow. The only way to make it work is to use a much smaller needle and seat, negating any benefit from the pump. If you need a lot of flow (like the water-cooled engine does at 1100 odd ml/min) a Holley bowl is the only way.

Something to point out in this photo - see how the back of the pipe is mounted with hose clamps? That's a quick and easy way when you're experimenting with pipe length. Once you happy with the results the bracket can be welded.
 

Texasstar

Can't is a four letter dirty word
Ouch, only 50 something HP. May I remind you I have small transfers. First Teazer telling me I need to practice and now you reminding me I haven’t made it to 50 yet. Lol.

So let’s say I am crazy enough to put a Holley float bowl on a Bultaco where would we pick up the pulse for the fuel pump?

BTW what were you doing with those hoses? Increasing crank case volume?


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John Murray

Been Around the Block
Ouch, only 50 something HP. May I remind you I have small transfers. First Teazer telling me I need to practice and now you reminding me I haven’t made it to 50 yet. Lol.

So let’s say I am crazy enough to put a Holley float bowl on a Bultaco where would we pick up the pulse for the fuel pump?

BTW what were you doing with those hoses? Increasing crank case volume?


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No pulse, electric fuel pump. Not sure what hoses you're looking at, maybe gearbox and clutch case breathers. The power you're making from an ancient two transfer engine is very impressive and is RWHP.
 

Texasstar

Can't is a four letter dirty word
Who would be crazy enough to run a Holley float bowl? Team Old Age and Treachery is! I present the genius of John Murray. We are also running two fuels. Fulfilling our name Texas two step!
IMG_9816.jpg



So the Pingel Guzzler Petcocks are expensive and as you know I am frugal and a ball valve is a ball valve IMHO. See any reason why we can’t use a stainless 3/8 ball valve and two 3/8 spiral barb stainless fittings? 5/16 gets us to 900ml per of gravity flow without the gas cap and 600 ml per minute with the gas cap. I am adding a separate tank for the methanol and we will keep the first tank for premix gas. The current tank is 750 ml and I am thinking about running the same for the Methanol.


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John Murray

Been Around the Block
I can't claim any credit for re-purposing Holley float bowls - car guys have been running them on SU carbs for decades.
 

Texasstar

Can't is a four letter dirty word
I can't claim any credit for re-purposing Holley float bowls - car guys have been running them on SU carbs for decades.

Wait a minute...let me give some context to this and why I think it is brilliant. Chainsaws. If anybody has run a chain saw they will understand one thing. Throttle response is amazing and they are designed or WOT! When you told me it was a butterfly carb and that you didn’t like slides for alky I knew exactly why. As far as I know the car guys weren’t running a two stroke that has a very special problem when sitting there idling flooding the cases with methanol. The pooling in our cases. As far as I know I have never heard of running a two stroke with regular fuel on the idle circuit and methanol on the main and I was with two seasoned two stroke racers Friday night at the track and they looked at me like I was crazy when I suggested it after you told me about it. Now if you go watch the quad racer you will see he never takes his hand off the throttle. Why? Because his Lectron has the problem that you solved with the SBN Mikuni or the Super BN as they call it. If anybody takes the time to go back and read your tutorial on Methanol and has tuned a two stroke for Methanol they will see this is not for the faint of heart. Also you took care of a messy utility dealing with methanol by purging the system with regular fuel at idle and not having to changing fuels to put the bike up not to mention the regular fuel puts a little needed heat in the engine. Brilliant or I am easily amused. I can’t wait to try it! OBTW carbs verses EFI. My friend just pulled his EFI off and went to carbs to tune for methanol. Oh and Methanol is more green. Lol.


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