jetting for E85 (ethanol)

[mjm]

.... what does mean "mains" and "pilots"? I didn't get an engine-related meaning for them in any Portuguese-English dictionary. ....

I am not surprised that automotive definitions are not in a standard student dictionary.  

Main Jet - the largest of the fuel flow jets - generally in sizes like 120, 122.5, 125  and larger.  Larger numbers mean a larger hole for fuel to flow through.  In combination with the Jet Needle and emulsion tube this jet controls the fuel air mixture from a bit above idele through full throttle.  At smaller throttle openings the jet needle is more of an influence thatn the main jet.

Pilot Jet - the smallest of the fuel flow controling jets.  Much smaller sizes than the main jet.  Controls the fule flow at idle

[Rema1000]

I want to buy a GS 500 and convert it to ethanol too. Here on Brazil we proudly use this fuel pure...
Forgive my ignorance (nobody borns knowing anything, my mother says), but, what does mean "mains" and "pilots"?

A carburetor has a few basic parts: it has a "bowl", which works similarly to the water reservoir above a toilet: fuel from the tank fills it up; when it gets full, a "float" (which floats on top of the fuel) rises high enough to close a valve, stopping the flow of fuel, so that the bowl doesn't overfill.

When the engine turns, it creates vacuum, which tries to draw fuel up from this "float bowl" into the engine, through one or more straws, or "jets".  A "jet" can look like a small tube; or a small tube with a nozzle; or even just a screw with a hole through its center.  The bigger the jet is, the more fuel gets sucked through the hole, and the "richer" the fuel mixture is.

Simple engines have only one jet.  However, to provide better efficiency, multiple jets are often used.  On older GS500s, there is a big jet, called the "main" jet, and a very thin jet called the "pilot".  To burn alcohol, both jets must be made larger.  (recent GS500s have 3 jets, not 2).  The size of the hole in a jet is measured in millimeters.  A "60" pilot jet has a hole which is 0.60mm in diameter.  For 100% alcohol, I would suggest starting with a 1.6mm main jet ("160 mains") and 0.6mm pilot ("60 pilot").

For someone new to the workings of a carburetor, I recommend that you read http://www.motocross.com/motoprof/moto/mcycle/carb101/carb101.html

...there will be confusing parts; don't worry.
The next thing you would want to do is to clean the carburetors.  Refer to the instructions at http://gstwin.com/carb_work.htm .   It's very possible that if you take everything apart and put it back together, it will not run right.  If you make changes, then you won't know whether the changes you made caused a problem, or whether you made an error when you reassembled the carburetors.  So first, just take them apart, do a bit of cleaning, and put them back together.

When you are ready to try burning alcohol, then you can look at rejetting.  I have a general web page about rejetting at http://grapeape.specialgreen.com/pictorial/

I am planning too to cut 1,5mm of cylinder head, to increase compression ratio from 9:1 to something a bit lower than 12:1. Is there any problem? Will I reach some cyl-head cavity? Is it needed to cut pistons to avoid contact with valves?

A racer may know about the cyl-head question.   I would like to try 12:1 compression also.

How about the ignition map? Can you give more details and suggestions about modifications on it?

The map is not adjustable on a GS500.  However, the timing reference is adjustable.  There are some instructions for advancing the timing at http://www.gstwin.com/diy_timing_advance.htm .  Also read the discussion at http://www.gstwins.com/forum/viewtopic.php?t=6036 .  I am using 17 degrees advance (which is the stock 12 degrees plus 5 additional degrees), and it works.  With 100% ethanol, you should be able to advance much more than that, but the modification may not be as simple.  You might try advancing 8 additional degrees on the rotor.  If you decide to put the old jets back in, then 12+8 = 20 degrees advance should still work for E22.  If you go much earlier than that, then you won't be able to burn E22 any more.

So a good set of "first mods" to burn E100 is:
advance the timing 8 degrees
put in "hotter" sparkplugs
try 1.60mm hole in main jets, and 0.60mm hole in pilot jets
...and tune using the mixture screws.

It may be necessary to go to 0.65mm in the pilots.
I would be more sure of myself, except that I can't buy E100 here; I can only get E85.  And at some gas stations, it is really only E80 .

[mareaturbo]

Thanks for answers.
Now I know I need....
main jet = gicleur principal
pilot = gicleur de marcha lenta (idle gicleur)

[Blueknyt]

12:1 comp ratio

might be abit harsh for an aircooled to handle. dont think the gasket will hold it either.

[Rema1000]

Last post was October 2004... time for an update.  

I rode for a year on the 160 mains, and stock pilots drilled-out to about 57.5.  Every 3 or 4 months, I had to enrichen the pilot mix screws to keep from stalling at stop-lights.  By summer 2005,  the pilot mix screws were loosened way out, and I decided that the pilots must need cleaning.

So in September 2005, I redrilled the pilots.  The idle got better, but I started having a serious bog at 5k-6k rpm in 6th, which made highway cruising miserable.  If I did a small, gentle roll-on of the throttle from 5k RPM in 6th gear, the bike would shudder and slow down.  Since the only thing I'd done was redrill the pilots, and since I used the same drill bit from last year, I concluded that hand-drilling the tiny pilot jets was difficult to do with consistency.

Since I was using 44% oversize pilots, and only 28% oversize mains, I decided to try splitting the difference.  I went up to 165 mains (32% over stock diameter) and down to 55 pilots (37.5% over stock).  The 5k RPM bog was not as bad, but it was still there.  Even worse, I had to turn the pilot screws a bazillion times out (4? maybe 5?) to get maximum RPM at idle.  I think that I will go back up to 57.5 pilots next time I tinker.

To get rid of the bog at 5k rpm,  I wanted to shim the needle by 2 or 3 mm, but I couldn't find a good spacer.  Instead, I replaced the stock white plastic jet needle spacer (0.105 inches thick) with a 1/4" #4 nylon spacer (0.254 inches), effectively "shimming" by 3.78 millimeters (yow!).  Surprisingly, it runs strong now.  From a steady cruise at 4k rpm, 4500, 5k and 5500, I tried a gentle roll-on of throttle, and the bike responded well.  I'd say that the bike is running as well as it ever has.  I've had a week of riding, and I've not noticed any problems.  Maybe it respond quicker when I snap the the throttle shut now, but perhaps that's my imagination.

If performance gets bad again (like it did last year), then I will go back up to 57.5 pilots.  Also, if I can find a 5mm nylon spacer, I'll try using that as a needle shim (instead 1/4", which is probably more than I need).

Summary of current jetting for 85% ethanol:
55 pilots
165 mains
needle shimmed by 3.78mm

Possibly better would be:
57.5 pilots
155 or 160 or 165 mains
needle shimmed by 2.75mm

...but it's running great now, so I'm not going to touch it!

[Blueknyt]

thats alot of shim, have you tryed 170main?

[Roadstergal]

Thanks for the update, man.  I'm keeping an eye on this mod.

[ukchickenlover]

Problem with hydrogen is that it's only a container for energy, though, not a source. You gotta produce that molecular hydrogen somehow. In practice that'll probably mean a few hundred nuclear plants. Wonder where you'll find the population willing to put up with those and the waste they produce...

Ethanol on the other hand is produced from substances that have already stored solar energy when they grew.

To be fair, there are different ways to produce hydrogen.

There is plently of coal and windmills could be used to create electricity to break water for hydrogen. I think hydrogen engines will be the way of the future.

[rangerbrown]

i got to ask, what if you cant find a E-85 pump to get fuel. will it still run ?

[scratch]

Your jetting would be horribly rich.  Probably too rich to even run; else you'll be fouling plugs like crazy.

[rangerbrown]

i figured, but if and when the e-85 really gets off the ground this would be great.

have the head remilled, and rase comp to 12.5, have the cams regound (comp cams)
have block and head o-ringed or have custom head gaskets made. go larger in pistions and longer stroke if possable.

then a all day dyno, so that jets and timing can be set.


all for about 2k i would think

and maybe a extra 20 hp

[Chuck]

Holy thread resurrection... okay, but I don't think there was a point starting a new thread?  Is there any update on this?  I'm going down this road soon.  It looks like Rema1000 is using a 35% boost on jets, which is pretty consistent with every other E85 conversion resource I've seen.  Since I have a 2001 with a lunchbox and stock exhaust, I'm currently running 20/65/140, and it runs great.  So my initial E85 stab is 27.5/87.5/190.  It seems a bit extreme, but that's what the math says.  (The 2001 main is 4% larger than the pre-01.  The rejet adds another 10%.  So 14.4% on top of Rema's 165 is 190.  Hey, the math works again.)

So if no one gives any convincing conflicting advice, I'll probably be giving that a go.

As usual, I'm not interested in the politics of ethanol.  I'm doing this because it's interesting, not because it saves or destroys the planet or the economy.  Since gas is $3.75 and E85 is $2.79, I'm expecting to break even on dollars, even if I only get 3/4 the MPG.  I also like the idea of my bike smelling like a cheap drink.

[fodder650]

Thats ok Chuck i was going to necro it to when I saw your reply.

Two questions  -

Here in Pennsylvania we run 10% ethanol in all of our gasolines. Is this enough to think about a rejet of my stock settings? I also heard that ethanol is very hard on the rubber hoses in motors. At 10% any idea what kind of mess it could make for my GS?

[Chuck]

There is no reason to rejet for 10% ethanol.  All modern fuel systems are designed to tolerate 10% ethanol.  It says so in my GS owner's manual.  I know that ethanol is not as corrosive as methanol, which is where a lot of the confused warnings come from.  When people say "watch out for ethanol" they're thinking of methanol.

I highly doubt our stock hoses wouldn't tolerate even 85% ethanol.  If they don't, at least it's not as bad as a car.  You have about 18 inches of fuel hose total.  If they start breaking down, just replace them with "ethanol compatible" fuel hose (which you can buy anywhere online), and be done with it.

Since I got no replies, I'll probably go buy the jets and try it.   I'll let you know if anything dissolves.

[Ronin]

Not to change the subject,but I guess gas mileage is the topic.I found this article sometime back in Mother Earth news about water injection.On down hte article they mention that it was used on a BMW motorcycle with great results in mileage.Here's the link:
http://blizzard.rwic.und.edu/~nordlie/water_injection/novak/novak/060-114-01.html 

[Chuck]

Not to change the subject

The subject was rejetting for E85!  But that was an interesting article.

[ohgood]

this is one of those threads that hopefully, eventually, FINALLY will mean something in North America, someday !

I wouldn't mind pulling up to Farmer Jim's market, filling up with ethanol, tossing his daughter or son the CASH at the register, knowing that same few dollars may well be in my hand again and walking out to my bike, chugging off into the sunset....


as opposed to:

Having to check my account balance before filling up at a BP station, handing Habib my credit stick, and imagining my credits flying directly to Saudi Arabia, for some crappy mix of almost-gas, coughing and sputtering off into the smoggy sunset.


Someday, someday, we'll actually use our neurons.

[Chuck]

Righto.  I have no illusion that Ethanol is practical/economical/sustainable/ecological/etc right now.  But I think it will be.  I might as well do what I can to help, and increasing demand should do that.  Right now there are two E85 pumps in my state.  I drive by both of them on a regular basis, so why not?  If farmer Jim sold it, I'd drive out to wherever he is.

[cHa0s]

ok 60 pilots 155 mains and maybe lift the needle 2-3mm

I chose 57,1/4 pilots and 155mainjets, needle at last possible position in my 93. i ride this setup for 5400km. engine starts nicely with choke till 8°C.

[007brendan]

wow, I've never seen a thread raised from the dead so many times