Author Topic: Air fuel ratio guage  (Read 285 times)

Online coater87

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Air fuel ratio guage
« on: 31.05. 2019 19:22 »
Try this

https://youtu.be/fZOd3CT6aeQ

 I posted video first because I could make it work. *wink2*

 I had my old carb sleaved, and I could never get it tuned in. It was always so rich it would foul plugs, or so lean the plugs would be white. The white part scared me enough to buy a new carb from Amal.

 I also installed an air/fuel ratio sensor and guage from AEM to make setting up the carb easier. Our winters are long and I have the time.

 In the end, I ended up with

230 main
107 needle
20 pilot
3.5 slide
and the needle in the 4th slot.
pilot screw at 1 and 7/8 out.

 Its 7.5/1 compression, iron head.

 timing is 31/30, and the fuel is leaded 101 octane.

 I have had to learn how to start the bike all over, it does not need as much tickle as it used too, and also needs one small prime kick. I added a choke, which is now disconnected because it would vibrate closed slowly while I drove it.

 at wide open throttle, I have a ratio of 13,20 to 1.

 A perfect ratio is supposed to be 14.7/1 for new computer controlled, fuel injected motors. Anything higher than that is too lean.

 For ethynal gasoline, 12.8 - 13.2 is a good target, stay under 14.7 to one. Little blips higher than that are normal and will happens when you snap open the throttle. You just dont want to drive around at higher than 14.7 to 1.

 For leaded fuel, 12.5 to 1 is a good target.

 Its 90F out right now, I am going for one more blast with new plugs, and make sure everything is good. If it is, the good tank and exhaust is going back on and I am going to call the carb set up.

 Hope the video works for everybody, I am just learning this stuff and its a lot of mistake making.

 Lee

 This gave me a lot of peace of mind, I did not like finding the plugs white. Almost worse was fouling a plug while at a stop idling.

 Its 90F out today
Central Wisconsin in the U.S.

Online RDfella

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Re: Air fuel ratio guage
« Reply #1 on: 31.05. 2019 20:26 »
I always worry when we start getting technical about non-technical machines. Hell, it's easy enough to set up a carb provided you follow the usual steps. Main jet covers full throttle, needle part throttle, cutaway lower end and affects opening of throttle and pilot for tickover up to 1/4 throttle. What an engine likes may or may not coincide with preferred values. Frankly, I can't stand the flat spots and ten seconds to tickover of modern emission-conscious vehicles.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Online Triton Thrasher

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Re: Air fuel ratio guage
« Reply #2 on: 31.05. 2019 20:47 »
I always worry when we start getting technical about non-technical machines. Hell, it's easy enough to set up a carb provided you follow the usual steps. Main jet covers full throttle, needle part throttle, cutaway lower end and affects opening of throttle and pilot for tickover up to 1/4 throttle. What an engine likes may or may not coincide with preferred values. Frankly, I can't stand the flat spots and ten seconds to tickover of modern emission-conscious vehicles.

There’s always one!

Online muskrat

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Re: Air fuel ratio guage
« Reply #3 on: 31.05. 2019 21:25 »
G'day Lee. Well done mate.
There may be a little difference between that side pipe being straight through and the other side muffled, but should be close enough for our old bangers.
I often thought about doing that to the cafe on both sides to tune the twin carbs. Those sensors you used are a lot more accurate than the probes that stick up the end of the pipe.
Cheers
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Online orabanda

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Re: Air fuel ratio guage
« Reply #4 on: 01.06. 2019 00:46 »
Great work Lee!

If you have the time (and inclination) it would be interesting to see how the RH cylinder compared.

Also, what's your elevation? (height above sea level, not body position).

Richard

Offline worntorn

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Re: Air fuel ratio guage
« Reply #5 on: 01.06. 2019 02:21 »
This is a great approach.
As far as it being a bad thing to use modern methods on an old bike, I can't agree with that concept.
We use a lot of modern bits to make our old bikes perform better, leak and burn less oil.
Electronic ignitions, 12 volt charging and lighting, 2 ls brakes replacing original 1 ls, modern compound and profile tires, and on and on.
For example- an original 1947 Vincent in good condition would normally burn 1 Imperial gallon or 160 ounces of motor oil every 1500 miles ( Riders Handbook specifications page)
Fitted with close fitting modern low expansion pistons, all  modern Nitrile  gaskets, various ORing seal fixes and Honda chrome rings, I ran 2800 miles without adding oil, then topped off at home with 8 ounces.

So I see using modern technology to get the AFR in target as just another way to make an old bike perform better.

Glen

Online coater87

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Re: Air fuel ratio guage
« Reply #6 on: 01.06. 2019 02:46 »
 OK, my HASL is about 850 feet, give or take a couple.

 I picked the left hand side because it ran the leanest of the two from looking at the plugs. I can pop the set-up over to the right hand side for you and let you know what the differences are. I know a straight pipe will run a little leaner than a muffler, so I am trying to take that into account.

 I could see a huge advantage to having two of these set-ups for dual carburetors. Zero guessing in setting them up to run equally. When I talked to the car guys they wanted me to go to the junk yard to get the sensor, they are free if you can get them out of the pipes. Than all you need is a guage to read and those are getting cheaper all the time. We just need a sensor and a way to read it under load.

 I bought all this stuff as a package and just welded on some bungs. I dont have to pay for Dyno time, or doubt my plug chops, or guess at all. I can take it off and put it back if I ever change anything in about an hour.

 I have also swapped in a #4 slide, and I will see tomorrow if I am done.

 Lee

 
Central Wisconsin in the U.S.

Offline Swarfcut

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Re: Air fuel ratio guage
« Reply #7 on: 01.06. 2019 07:19 »
Lee  I am glad there is One.   Someone prepared to use a bit of lateral thinking and come up with a very workable solution to the problem, who then executes it with the stuff available to hand. Congratulation on a job well done.

 I am also reassured that an old school AMAL design has been proved to be able to provide close to the Stoichiometric Ratio which means the engine is running at close to complete combustion, which is good for the motor, good for your billfold, and very good for the environment.

 I am well impressed by the way you did it, the bike sounds happy, there is little vibration. Looks to be a good ride.

 Swarfy.

Online RDfella

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Re: Air fuel ratio guage
« Reply #8 on: 01.06. 2019 10:58 »
It seems some may have misunderstood my original post re modern technology on old machinery. Of course some modern stuff – eg tls brakes will effect an improvement, but with old design / clearances etc what the engine is happiest with may well not be what someone has decided is the ideal. Modern engines are built to suit ideal figures, 1940’s designed machinery was not so the mixture (or ign timing) it is happiest with will almost always be different from engine to engine. The figures produced from this experiment may be interesting, but otherwise serve little purpose. For example, my Jag runs quite rich. Smokey rich. They do, because they need to (mainly due to rubbish manifold design). Set it at the optimal air / fuel ratio and it’ll be undriveable. Probably have an under-bonnet fire from the backfires to liven things up as well. In the late 60’s I put a Singer on one of the then new engine tuning machines. Think it was Tecalemit. Mixture and timing spot on etc. Drove out of the garage and had to stop less than 100yds down the road to re-adjust because it was undriveable.
Tune an engine to where it’s happiest, not religiously to some figure someone in an office has decided it should be.
I don’t measure my morning toast with calipers because there’s no point. Likewise I don’t tune my older engines using the sort of modern equipment necessary for modern engines to comply with environmental legislation. I want my engines running sweetly, not set to some scientifically agreed formula that may not be appropriate.
I’ll finish with one last example. At a hill climb in the 70’s a friend was using his Cooper single seater. During practice it was running rough as hell, and so I asked him what jets he was using in the Webber carbs. When he told me, I suggested alternatives. He scoffed, asking if I thought I knew more than the engine supplier. During lunch break he came over and asked me what I had suggested. Seem to recall it was 130 / 160 or thereabouts. I also suggested he slacken off the rear shocks, as the car was squatting off the line. On the next (first official) run he set a new record. Tuning by ear. *smile*



'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Online Triton Thrasher

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Re: Air fuel ratio guage
« Reply #9 on: 01.06. 2019 11:18 »
No quantity of typing by anyone is likely to persuade me that I should not measure the richness of the mixture by whatever means are available.

It can be hard to pin down tuning problems by ear or plug chops, in cases like a rich cutaway with a weak needle jet (or vice-versa), or a satisfactory idle but a rich condition on over-run sooting up the plugs.

Online KiwiGF

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Re: Air fuel ratio guage
« Reply #10 on: 01.06. 2019 12:45 »
Great approach I like it   *smile*

These bikes are for riding and messing about with, this takes the “messing” to a new level   ;) if it took 5 minutes and $5 we’d all do it wouldn’t we?
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Online Seabee

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Re: Air fuel ratio guage
« Reply #11 on: 02.06. 2019 05:13 »
I would love the peace of mind knowing that I was not dangerously lean, even if it liked running there!
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Online coater87

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Re: Air fuel ratio guage
« Reply #12 on: 03.06. 2019 10:41 »
 I switched the sensor over to the right hand side.

 The timing side is consistently .80 to 1.20 more rich than the left side through the entire range, so there really is bias. Now how bad my head is compared to others I dont know.

 Some day I might make up an anti bias gasket and see if I cannot even these out better. But for now, the carb is set-up for the leanest pot and I am going to leave it there for a while.

 Lee
Central Wisconsin in the U.S.