E85 Ethanol Conversion (math warning for the headache prone) :)

[Egaeus]

Okay, so I am thinking of converting to E85 ethanol.  I am not concerned with the relative merits of ethanol or gasoline over the other, or the sustainability of ethanol, or whether you get more energy from ethanol than it takes to produce it.  I am concerned with what it takes to run the motorcycle on E85.  

Now, searching led me to two interesting threads:

http://e85forum.com/about124.html&highlight=gs500
and
http://gstwins.com/gsboard/index.php?topic=7945.msg108039#msg108039

I did some math based on the ChemE (Jim's) numbers in the first thread.  I am currently running 127.5/40 with gasoline and am happy with it.  

A 127.5 diameter has a radius of 63.75

Ideally, the volume of liquid that can flow through an opening is directly proportional to the cross-sectional area of the opening (i.e. twice the area = twice the fuel).

Area of a circle = pi*radius^2

So taking the square of the radius, we get ~4064.1.  

multiplying this by the 1.3814 from the first link, we get ~5614.1.

(pi is irrelevant in this case)

Taking the square root, we get ~74.9.

Doubling to find the new jet size, we get 150 as the desired jet size.  

Similarly, for the pilot jet we get a new jet size of 47.5.  

I even wrote a few lines of code to calculate this because I was tired of doing the math by calculator (you can have it, but you need Matlab or Octave to run it).

Now, this conflicts significantly with Rema1000's reported jet sizes of 160/60.  I'm curious as to why.  

Some possibilities (in no particular order):

-Rema has made filter/exhaust modifications
-Rema is running rich
-The volume of fuel drawn through the orifice is not exactly proportional to the area since it's a venturi system.
-The 1.3814 number used by Jim is not the correct value that should be used.  

Time to go on a tangent here.  On that last point, I actually believe I should be converting the weight difference mentioned in the air/fuel ratio discussion to volume and using that value.  I didn't because I'm certain that it would be an even smaller number.  Well that, and I'm lazy.  The justification is that we want to acheive the same (or similar) level of combustion.  However, to keep from looking like a fool, I'm going to do it now so nobody can slap me around with it later.

According to Jim, the the amount of E85 by weight needed for the correct air/fuel ratio is 32.91% more than gasoline.  So weight_E85 = 1.3291*weight_gas.  Converting this to volume, we get 6.2/6.55*1.3291 = 1.2581.

Doing the above calculations with that number gives jet sizes of 142.5/45.  Someone might want to check that I did the dimensional analysis correctly.  I'm too lazy to work it out properly.  It's either 1.2581 or 1.2541.  Not enough of a difference to matter in this case; it gives the same results.  

So, any thoughts?

[CirclesCenter]

My bet is math is perfect, reality is not.

[Egaeus]

My bet is math is perfect, reality is not.

That would be option 3.  I actually think that it's a combination of 3 and 4.  However, I'd like some science to back that up.

[coll0412]

Yeah you have to remember that you are ignoreing alot of things that change when you switch fuel types
so even though your math gets you somewhat close to what you think, you still will need to find what is best for your bike and riding style.

Ahhh the theoretical vs empirical problem strikes again.

Some things that probably skew your math are, burn rate of the ethanol, how touchy it becomes if it is to go lean, compression ratio(it changes with wear).

[CirclesCenter]

That's why I say just rock what is proven and go from there.

[Egaeus]

Yeah you have to remember that you are ignoreing alot of things that change when you switch fuel types
so even though your math gets you somewhat close to what you think, you still will need to find what is best for your bike and riding style.

Ahhh the theoretical vs empirical problem strikes again.

Some things that probably skew your math are, burn rate of the ethanol, how touchy it becomes if it is to go lean, compression ratio(it changes with wear).

Yes, it's definitely a theoretical vs. empirical problem.  Problem is that I don't have the money to experiment empirically with jet sizes, especially when both jets will have to change.  

I'm not sure the burn rate really enters into the jet size discussion.  That would be more of a timing advance issue, woudn't it?

compression ratio is a definite factor.  However, wouldn't lower compression mean that you'd need even smaller jets, since the less air there is to burn the fuel, the less fuel you need to inject for proper combustion?

I guess that if you are worried about it running lean, you could jet it richer.  I've PM'd Rema1000 asking him to opine as well.  

[CirclesCenter]

I thought jets weren't too expensive?

Maybe I'm just too used to quadrajet carbs, where if you want to rejet you take a couple bucks down to Albertson's or Raley's and pick up a dozen for 1.99. LOL

[ducati_nolan]

I bet you're on the right path to make it work, and after a little bit of tweaking I'm sure it would run just fine.....for a while. I don't know if there is a place to get cheap carb diaphrams, and I think that the alcoholl will degrade those in a short ammount of time. Fuel line and O- rings no big deal, but I think those diphrams are pricey and hard to find. They seem to hold up fine with 10% ethanoll though, so maybee it's okay, but you may want to at least have a spare set on hand.
Good luck. 

[Egaeus]

I bet you're on the right path to make it work, and after a little bit of tweaking I'm sure it would run just fine.....for a while. I don't know if there is a place to get cheap carb diaphrams, and I think that the alcoholl will degrade those in a short ammount of time. Fuel line and O- rings no big deal, but I think those diphrams are pricey and hard to find. They seem to hold up fine with 10% ethanoll though, so maybee it's okay, but you may want to at least have a spare set on hand.
Good luck. 

Rema1000 said he's been running it for 3 years and has nothing to show for it but extremely clean carburetors. 

I thought jets weren't too expensive?

Maybe I'm just too used to quadrajet carbs, where if you want to rejet you take a couple bucks down to Albertson's or Raley's and pick up a dozen for 1.99. LOL

On average, you'll spend about $3.50 per main jet and $4.50 per pilot.

[tussey]

So, any thoughts?

God you're such a nerd 

When you coming down?

[Egaeus]

So, any thoughts?

God you're such a nerd 

When you coming down?

Looks like Turkey Day or possibly the end of Oct.  And yes, I am a nerd.

[LimaXray]

Yeah all modern fuel systems are ethanol safe because of the ethanol content in a lot of gasoline... now methanol, that's a different story

As for your math, remember Mikuni uses the actual flow rates for the jet numbering, so you really don't need to do all that math.  So if you're right by saying the ethanol/gasoline flow rate ratio is ~1.25, that will give you ~158.75 mains and ~50 pilots.

You might want to go a little richer than normal on the pilots as ethanol doesn't burn well when it's cold

Compression ratio and burn characteristics don't matter.  Compression ratio doesn't effect the amount of air entering the centers as it doesn't have any bearing until the valves are closed and no more air is coming in or leaving.  Jacking up the compression ratio would be good as you'd make more power and the high octane rating of the E85 would support it.

Burn charateristics do effect ignition timing.  While you probably can get by without it, it would be best to jack up the timing advace as ethanol does burn more slowly.  This also means you make more power.

[Egaeus]

Yeah all modern fuel systems are ethanol safe because of the ethanol content in a lot of gasoline... now methanol, that's a different story

As for your math, remember Mikuni uses the actual flow rates for the jet numbering, so you really don't need to do all that math.  So if you're right by saying the ethanol/gasoline flow rate ratio is ~1.25, that will give you ~158.75 mains and ~50 pilots.

You're kidding, right?  You mean I did all that for nothing?  I figured that it was the diameter of the orifice in hundredths of a millimeter or some other straightforward measurement.  Guess that's what I get for assuming.  Do you have units for the numbering system?

You might want to go a little richer than normal on the pilots as ethanol doesn't burn well when it's cold

Understandable.  I don't know if I'd go 4 sizes up though.

Compression ratio and burn characteristics don't matter.  Compression ratio doesn't effect the amount of air entering the centers as it doesn't have any bearing until the valves are closed and no more air is coming in or leaving.  Jacking up the compression ratio would be good as you'd make more power and the high octane rating of the E85 would support it.

My theory was that if the compression ratio is lower than it should be, then it is caused by leakdown either past the valves or past the rings.  That means that there is less air to combust the fuel. 

I read about increasing the compression ratio, but I'm not sure I want to go that far, as a quick conversion back to gasoline would be necessary if I were to take a trip somewhere more than 75 miles away. 

Burn charateristics do effect ignition timing.  While you probably can get by without it, it would be best to jack up the timing advace as ethanol does burn more slowly.  This also means you make more power.

I figured that was the case since Rema1000 advanced his.  That's easy enough, and works okay with gasoline as well from what I've read on the site.

[Jughead]

The only Drawback to Ethanol will be Rust.Ethanol is Alcohol and will Draw Moisture out of the Atmosphere.You will be looking at rust forming in the Gastank (Most Cars now have Plastic Tanks) and if left for long Periods of time you will find Rust Forming on your Cylinder Walls,Rings and Valves.It will be OK if you run it Most of the time.I really don't know what the effects would be on the Remaining E85 in the Carbs.More than Likely it wouldn't be good after several months.
On a two Stroke Running Alcohol for Racing is done all of the time but Afterwards the system is Purged with Gasoline to Prevent anything from Rusting.It works but is it really worth Rusting the Bearings out of your Crank if you don't purge it and let it set?

[LimaXray]

Yeah ethanol is hydroscopic and can cause rust issues, but it is not nearly as bad as methanol.  The shelf life of ethanol is far better than methanol because it doesn't suck the water out of the air nearly as quickly.   As long as you purge the system clean at the end of the season you should be fine.  You might want to Kream your tank first just to be safe.

Methanol is what is used in most race engine, and yes it must be cleaned out after every race to prevent various kinds of corrsion, whereas this wouldn't be the case with ethanol.  Methanol is just FAR more reactant and toxic than ethanol (which one can you drink for a good time and which one can you drink for certain death?).  It's little things like that why they sell E85 for the street and not M85.     

When it comes to water, the plus side of ethanol over gasoline is ethanol and water mix and will still burn if there is more ethanol than water.  Gasoline and water won't, the gasoline will float on top of the water, meaning you'll get plain water in the bottom of your tank and in your float bowls, which won't burn at all.

[Jughead]

Kreem is OK but it Starts Peeling after a while.I would Consider POR 15.It's Just ass Cheap or Cheaper than the Kreem Kit.It comes with it's own Cleaner for he Tank and as far as I know from all of the Users that I've talked to it has Never peeled.