E85 Jetting progress

[Chuck]

Someone suggest where I can go from here:

2001+ (3 circuit) carb
gas config 20/65/140, 2.5 turns
lunchbox, stock exhaust
runs great at all speeds and all throttles

E85 test 1:
27.5/87.5/190, 1.5 turns - restricted idle air passage (with extra 130 jet) to make it idle properly
This is approximately +35% on all jets, which is generally recommended for E85 rejetting.

idle ok, revs ok with no load
rides ok with gentle throttle application (barely any throttle)
pulls ok at full throttle (could be better, not sure)
no power in between - say 15% to 70% throttle - blah - flat
better with choke

test 2:
change mid jet to 130, just to see (it's what I had laying around)
way too rich at idle, smells like a bar, visible fuel in exhaust stream - no go

test 3:
drill 87.5 mid jet to approx 95
possibly better mid throttle, but not much, still better with choke - almost drivable
Still pulls ok at max throttle

test 4:
drill mid jet to approx 110
BAD.  Mid power still bad unless using choke.  With choke, almost drivable
No power at all at max throttle.  Completely dead.
Engine dies at idle with choke - I'm definitely going the wrong way with this jet

-----

So test 1 was the best (or maybe test 3 was slightly better), but basically all the futzing with the mid jet made it worse.

My concept of "mid throttle" may be completely wrong, and it's in fact "low throttle."  Who knows?

Anyway I think I mis-diagnosed the mid jet, and in fact I should have been making the pilot richer, and adjusting the idle screw to compensate for the idle condition.  I should put the mid jet back to 87.5 (I have two left) and start drilling the pilot.  That sound about right to anyone??

That way, I can probably get to un-block the idle air circuit (which seemed dumb, but was the only way to get running in the initial config) and maybe what I think is mid throttle is low throttle, high is mid, and there's a max throttle I haven't dreamed of yet.

Only problem with that is increasing the pilot by more than 40% seems nuts.  But if I ignore the numbers and go by symptoms, it seems like the right thing to do.

Any other ideas, or should I charge on ahead?

[Chuck]

Oh, except I don't have a drill that even remotely fits inside the pilot jet.
So that's going to stall me for a while.

[CanukGS500]

one thing you may want to consider in your tuning efforts is that E85 has a much higher octane rating than gasoline.  This in turn means you can/should advance your ignition timing to take advantage of this fact.

IMO, your test 1 jetting to give you the extra 35% fuel is a good choice.  From there I would try advancing your ignition timing a few degrees and see what happens.

[The Buddha]

From #4 I'd go larger on mids, and smaller on mians. But maybe ethanol cannot burn at 7K rpm.
Look for posts from rema1000 - he did ethanol a few years ago.
Cool.
Buddha.

[Chuck]

From #4 I'd go larger on mids, and smaller on mians. But maybe ethanol cannot burn at 7K rpm.
Look for posts from rema1000 - he did ethanol a few years ago.

Seriously?  Does the mid start kicking in at 15% throttle application?  I'd thought I'd bolloxed everything drilling out the mid so much.  I can use the 130 mid and I have some 142.5 mains lying around that I can start enlarging...  at least it's something I can do, since otherwise I have to order new pilots (or really tiny drill bits).

What throttle range does the pilot affect?  The main reason I thought the pilot was too lean was that I had to block off the idle air, which still seems stupid to me.

I got my initial guesses from Rema100, but he's using a pre-01 carb with a stock airbox, so I was only able to use his percentages.  And he doesn't answer emails.

[Chuck]

one thing you may want to consider in your tuning efforts is that E85 has a much higher octane rating than gasoline.  This in turn means you can/should advance your ignition timing to take advantage of this fact.

This is a good idea, but I have to get the fuel mix right before adding another variable.   Advancing won't fix a rich or lean condition.

Eventually I will do this, though.  I'll probably do something like this: http://www.gstwin.com/diy_timing_advance.htm

The amount of advance is probably enough to just drill new holes, instead of slotting the ones already there.

With two carbs and two ignition pickup orientations, I'll still have a vaguely "flexible fuel" ride.  (It will take about 30 minutes to "flex")  If I'm crazy I can go all the way and increase the compression, but that will depend on aforementioned craziness and the assured permanent availability of E85.

[CanukGS500]

well I brought it up because of desriptions of your fuel tests.

I'm going to try and find it in one of the old car forums i used to be a part of... I remember reading someone who was converting to E85 and had a very similar situation to yours after adjusting his fuel injectors to give the proper fuel (part throttle under load wasn't good).  His situation improved after he bumped up the timing because the higher octane rating and the slower rate of burn of ethanol meant advancing it to compensate.

when i read the results of your first test, it made me think of that article.

I'll try and track it down, and if i do i'll post it.  just ignore the "fuel injector" part

[Chuck]

Sounds cool.  Hope you find it.

Even if it's not what I'm dealing with now, it's something to handle next.

[The Buddha]

Mids I think are 1/4 to 3/4 throttle, just like needle.
Advancing timing will let it burn at higher rpm's ...
Cool.
Buddha.

[Chuck]

I got another two tests in today.

Test 5:
130 mid
main jet drilled to .058" (160-ish jet???)

results the same as test #2 - too rich, no power anywhere - can't even take off

Nice thinking, Buddha, but I don't think that worked out.


Test 6:
Drill pilot to .040" (Smallest drill bit I have - insanely large pilot, but I had to try it.)
mid 87.5
main 190
NO AIRWAY BLOCKING (YAY!)

Rich wet idle (hard to keep running)
Awesome power up to about 20% throttle.  Great take off.  Cruises fine at 40-50mph.
(That probably means the mid would be too lean with the correct pilot, but let's not jump ahead)
No power above 20% throttle - choke makes it worse - too rich - I'm not surprised

-----

Okay, so I'm not surprised that the oversize pilot is too rich.  However it cleared up my need to block the idle air passage, and it has significant effect on low throttle settings.  More than I expected.  I think I need to find the right pilot and get a clean idle with an unmodified air circuit before I can get the midrange sorted out.  Blocking the air was an awful hack and I'll be glad to get rid of it.  Once I've got a mix that burns on all jets, then I can finish tuning it the "right" way (main jet first, and work down).

I might still find the mid is too lean after getting the pilot sorted out.  But I'm sure I have to visit the local dealer and see if we can work out a jet swap program, because now having accurate jets is getting a bit more important.

This is my first real carb tuning experience.  I'm sure it would be easier if I was jetting for the same fuel it was designed to run.    At least when this is over, I'll be smarter than when I started.  (And I can learn how to brew my own fuel.  )

[Chanse]

How about installing an air\fuel ratio gauge to help with the diagnosis. Might tell you at what RPM your starting to get to o lean or rich. Just a thought, but it seems alot of trouble to keep guessing.

[Chuck]

Haha, the AFR is not what I'm guessing at, it's which jet to change.  I'd like a gauge for that!    Whether I'm rich or lean is painfully obvious.  A gauge might help me get from "running" to "running well" though.  But folks have been doing that by feel for generations, too.  I've done it on countless lawn mowers and tractors, but they typically only have the one main jet.  It's this two main jet business that's getting me, although I'm sure that will result in better running in the long run.

BTW the jets in play are not affected by RPM, just throttle.

[jrains89]

any news on this e85 project, i would love to be able to run e85

[Chuck]

Working on other projects now.  Today it's a broken furnace.

I've confirmed that a way oversize pilot allows the normal air passages to work, so I just need to dial in the correct pilot (somewhere between 30 and 60) for idle and low throttle to work correctly.  (Need either fine drill bits or a pile of pilots, depending on the budget.)  Then I'll go back to the mains and tweak them until it works.

I definitely will update progress when I have some.