Measured Air/Fuel Ratio for Optimization

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Fast Eddie said:
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I'd suggest that 'full' rich on an F1 car will not be much below 14.7:1.
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I think we'd need to see the fuel/air printout on a dyno run.
A trace of black smoke out the back on hard acceleration would suggest otherwise. ?

Injected race cars also commonly puff fuel through the engine on the overrun - to cool the engine internals.
Thats the flames you see puff out the exhaust.
Same as kart race guys put a hand over the air inlet on slow corners, to cool the engine with some extra fuel...
Rich is cool, rich is strong, rich wins races.

Same as aircraft guys know that running lean for fuel saving cuts the climb rate, significantly.
And sees the cyl head temp and exhaust gas temp climb, literally, into the red zones on the gauges...
 
When I jetted the 34 mm Mk2 Amals on my 850 850 for methanol I made my own needle jets from brass hex using number and metric drill. The first pair I made were 0.117 inch however I couldn't get the motor to cough., and the bike was sluggish. I then made a pair at 0.116 inch and the motor coughed , so I raised the mikuni DP6 needles one notch, and it was excellent - smooth and really good power. Are we talking about rich or rich? I believe my jetting is still probably slightly rich, however it is where it should be. How big are the steps on a Mikuni needle as far as richness goes ? I'm using 670 Amal main jets however because I've only had the bike on a relatively small circuit, I haven't bothered doing plug chops.
It is obviously not the same situation as riding a petrol fuelled commando on a freeway. With a racer it is about power and unless it gets onto a big circuit, the main jet sizes are not very important. I've used methanol for many years, and I have a fairly good idea what the jet sizes should be. The jetting kit supplied for methanol, for the 34mm Mk2 Amals for the commando is absurd.

You might consider why the needles for Mikuni carbs come in many tapers. I suggest it is all 'suck it and see'. If you think you can get it right by using an O2 measurement - good luck with that. How is the instrument calibrated ?
 
[video]http://www.youtube.com/watch?v=-r1opwkhKDs[/video]

[video]http://www.youtube.com/watch?v=Zzn3-ygH-v8[/video]

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[video]http://www.youtube.com/watch?v=hSPLvPL2OII[/video]
 
acotrel said:
You might consider why the needles for Mikuni carbs come in many tapers. I suggest it is all 'suck it and see'. If you think you can get it right by using an O2 measurement - good luck with that. How is the instrument calibrated ?
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An O2 meter is one tool we can use to set up carburetion. It takes guesswork out of some aspects of setting up the carbs. Mine showed that my race bike on WOT was rich at the lower end on the rev range but spot on at the top, so I needed to change the air correctors. That's quite a difficult thing to do by feel.

Depending on the type, they are either calibrated at the factory or need to be calibrated in clean air before each use.
 
Since no one has mentioned it yet (?), injected triumphs have available upgrade chips for the ECU.*
e.g.
http://www.ebay.com.au/itm/DYNO-BOOST-P ... 0995122161

BTW, think you'll find these don't give more performance by running leaner.
Lean is for fuel savings and emissions control.
Richer is for more power !
Note the little power graph down there somewhere, not that it says much about it.

*Probably not legal, BTW.
 
'Richer is for more power !'

Another statement of 'FACT' ? The most power from old bike engines is leaner than the jetting the manufacturer supplies as standard . It is almost at self-destruct, your comment only applies to the main jet. If you want fast acceleration, jet as lean as possible until the mains take over. It is only at full throttle that you are likely to burn anything if the mains are too lean, otherwise usually only if you continue you ride the bike while it is coughing through lean midrange jetting . If you are riding a two stroke and it suddenly starts to go much faster - watch out, it is probably about to seize. Never make a two stroke 'cough', you can cough out a crank.
If you want max power on a big circuit, jet the mains rich for safety, nothing to do with getting more power. With a two stroke, even getting it to rev up so that you can use full throttle and run on the mains can be a problem, if the low throttle range jets are not lean enough.
 
Fast Eddie said:
Rohan said:
Seeing a telecast of the end of a 12 hr sports car race (Cars !), they mentioned the McLaren had plenty of fuel at the end,
and, not needing to save fuel, had been given the go-ahead for "full rich setting No # 1, for maximum power".

Lean running is fuel saving mode.....
Click to expand...

That's quite right. But it all depends on where the line is between rich and lean.

There is no extra power to be gained by being 'too' rich... only 'full' rich.

I'd suggest that 'full' rich on an F1 car will not be much below 14.7:1.
Click to expand...

The terminology is what is in question here. "Full rich" in this case is likely as you say...very close to perfect mix...maybe slightly richer...not what we normally talk about as rich when tuning a street bike...there seems to be a lot of confusion about this.
 
At lower rpm carb air flow may not pick up enough fuel for best power so carbs are set up or an accelerator pump used to help momentary Richen
mix to rev up strong w/o a bog. Richness for WOT power has most to do with *advancing ignition* to delay/slow the burn for best torque pressure after TDC and not over heat and detonate. Any fuel beyond stocio is wasted to cool chambers. Richcardo found that up to 50% water could be added to make more and more power beyond what merely enrichening can provide and a bit more power > if the fuel mass was reduced somewhat as more and more water added. So what may win a race one humid day may melt soon after take off on a dry day, so enrichen to waste enough fuel it just don't, with the particular spark timing used.
 
I believe water injection was used on some WW2 fighter planes, I always thought it was a way of raising the comp ratio without getting pre-ignition. It might also have had something to do with the use of conventional carburettors which used to flood when the plane dived.
 
acotrel said:
I believe water injection was used on some WW2 fighter planes, I always thought it was a way of raising the comp ratio without getting pre-ignition.
Click to expand...
Yep; that was it. The added cooling effect to the inlet charge allowed for higher compression ratios than without, and, maybe more importantly, kept them out of detonation when running high levels of boost. Along the aircraft references that have come up in this thread, full rich is used during take-off and idling on the ground for the same reason; cooling. Once up to cruise speed/throttle setting (65-75% power), you lean a carbureted engine to max exhaust gas temp, then richen by at least 25'F. This is to ensure no cylinders go lean, as you normally only read one (hopefully, the leanest) cylinder.
On a fuel-injected engine, you lean to max EGT, then continue to lean past until the temp drops off by ~25'F; the assumption being that all cylinders run the same mixture, and you can safely take them all a touch lean for greatest economy.

Nathan
 
We notice you have zero miles riding a Commando on the street Alan, so who here is going to trust this 'advice'.
Show us a dyno run showing significantly leaner giving more power ??

While its probably true that you could get a mere trace more, sometimes, since the factory jetting settings have to cover all atmospheric conditions,
and errs slightly on the richer side, going down more than a jet size less than recommended is simply going to give less go.

While not quite the same thing, I'd comment that some years back, I experimented on my baby GM V8, by disconnecting the accelerator pump.
Fuel consumption on a longer run jumped from an average ~16 mpg to a whopping (for an old V8 ?) 30 mpg.
But that was steady state cruise, the acceleration up hills was woeful.
You couldn't plant the foot and GO, it simply slowed and slowed on steeper hills, right back to crawling in 1st.
Acceleration on the flat and level had to be pretty gentle too.
It was still fast downhill though !

Show us a dyno chart documenting what ye claim !!

P.S. Why do you think all the chip upgrades for the ECU mention MORE FUEL ??
The more fuel it burns, the more power it has - within limits.


acotrel said:
'Richer is for more power !'

Another statement of 'FACT' ? The most power from old bike engines is leaner than the jetting the manufacturer supplies as standard . It is almost at self-destruct, your comment only applies to the main jet. If you want fast acceleration, jet as lean as possible until the mains take over. It is only at full throttle that you are likely to burn anything if the mains are too lean, otherwise usually only if you continue you ride the bike while it is coughing through lean midrange jetting . If you are riding a two stroke and it suddenly starts to go much faster - watch out, it is probably about to seize. Never make a two stroke 'cough', you can cough out a crank.
If you want max power on a big circuit, jet the mains rich for safety, nothing to do with getting more power. With a two stroke, even getting it to rev up so that you can use full throttle and run on the mains can be a problem, if the low throttle range jets are not lean enough.
Click to expand...
 
Rohan said:
We notice you have zero miles riding a Commando on the street Alan, so who here is going to trust this 'advice'.
Show us a dyno run showing significantly leaner giving more power ??

While its probably true that you could get a mere trace more, sometimes, since the factory jetting settings have to cover all atmospheric conditions,
and errs slightly on the richer side, going down more than a jet size less than recommended is simply going to give less go.

While not quite the same thing, I'd comment that some years back, I experimented on my baby GM V8, by disconnecting the accelerator pump.
Fuel consumption on a longer run jumped from an average ~16 mpg to a whopping (for an old V8 ?) 30 mpg.
But that was steady state cruise, the acceleration up hills was woeful.
You couldn't plant the foot and GO, it simply slowed and slowed on steeper hills, right back to crawling in 1st.
Acceleration on the flat and level had to be pretty gentle too.
It was still fast downhill though !
What carb? Holley? Are you sure you didn't disconnect the POWER VALVE? THAT would give the results you mentioned.

Show us a dyno chart documenting what ye claim !!

P.S. Why do you think all the chip upgrades for the ECU mention MORE FUEL ??
The more fuel it burns, the more power it has - within limits.


acotrel said:
'Richer is for more power !'

Another statement of 'FACT' ? The most power from old bike engines is leaner than the jetting the manufacturer supplies as standard . It is almost at self-destruct, your comment only applies to the main jet. If you want fast acceleration, jet as lean as possible until the mains take over. It is only at full throttle that you are likely to burn anything if the mains are too lean, otherwise usually only if you continue you ride the bike while it is coughing through lean midrange jetting . If you are riding a two stroke and it suddenly starts to go much faster - watch out, it is probably about to seize. Never make a two stroke 'cough', you can cough out a crank.
If you want max power on a big circuit, jet the mains rich for safety, nothing to do with getting more power. With a two stroke, even getting it to rev up so that you can use full throttle and run on the mains can be a problem, if the low throttle range jets are not lean enough.
Click to expand...
Click to expand...
 
Rohan said:
We notice you have zero miles riding a Commando on the street Alan, so who here is going to trust this 'advice'.
Show us a dyno run showing significantly leaner giving more power ??

While its probably true that you could get a mere trace more, sometimes, since the factory jetting settings have to cover all atmospheric conditions,
and errs slightly on the richer side, going down more than a jet size less than recommended is simply going to give less go.

While not quite the same thing, I'd comment that some years back, I experimented on my baby GM V8, by disconnecting the accelerator pump.
Fuel consumption on a longer run jumped from an average ~16 mpg to a whopping (for an old V8 ?) 30 mpg.
But that was steady state cruise, the acceleration up hills was woeful.
You couldn't plant the foot and GO, it simply slowed and slowed on steeper hills, right back to crawling in 1st.
Acceleration on the flat and level had to be pretty gentle too.
It was still fast downhill though !


Show us a dyno chart documenting what ye claim !!

P.S. Why do you think all the chip upgrades for the ECU mention MORE FUEL ??
The more fuel it burns, the more power it has - within limits.


acotrel said:
'Richer is for more power !'

Another statement of 'FACT' ? The most power from old bike engines is leaner than the jetting the manufacturer supplies as standard . It is almost at self-destruct, your comment only applies to the main jet. If you want fast acceleration, jet as lean as possible until the mains take over. It is only at full throttle that you are likely to burn anything if the mains are too lean, otherwise usually only if you continue you ride the bike while it is coughing through lean midrange jetting . If you are riding a two stroke and it suddenly starts to go much faster - watch out, it is probably about to seize. Never make a two stroke 'cough', you can cough out a crank.
If you want max power on a big circuit, jet the mains rich for safety, nothing to do with getting more power. With a two stroke, even getting it to rev up so that you can use full throttle and run on the mains can be a problem, if the low throttle range jets are not lean enough.
Click to expand...
Click to expand...

What carb? Holley? Are you sure you didn't disconnect the POWER VALVE? THAT would give the results you mentioned.
 
Do you know your engines ???
I disconnected the little accelerator pump.
Its the little piston in the little cylinder, that squirts the jet of neat fuel into the manifold on acceleration.
http://en.wikipedia.org/wiki/Carburetor ... rator_pump

My Guzzi has them on its carbs too = known as pumper Del'Ortos.
That l'il shot of fuel gives it a big kick in the pants - a big puff of black smoke out the zorsts, and you are GONE...
 
Show us a dyno run showing significantly leaner giving more power ??
Click to expand...

as I mentioned when I started this thread I also have a fuel injected new Triumph Bonneville that I took to my dealer and had it put on their dyno with two open throttle runs up to 7000 rpm resulting in 61hp at rear wheel

I received a print out showing this and also showing a quite consistent air fuel mixture of 15 parts air to 1 part gas

My friend also has a fuel injected Bonneville with the exact same modifications such as mufflers and airbox baffle removed, he put his on the same dyno 15 minutes after mine came off and with the same two runs up to 7000rpm his print out said 59hp, but at an air fuel ratio of 12.5 parts air to 1 part gas, and this is because he purchased an aftermarket ECU map that apparently maps his bike to run a little richer than my own stock ECU mapped bike

My dealer made a comment that my bike showed two more horsepower because it was a little leaner mixture than my buddy's bike, and he also said that this finding was consistent on dyno tests of many bikes when he would change the Power Commander settings to play with the air fuel mixture

so, although this 2 hp difference is not "significant", it is real and does to me seem to verify the contention that all things being equal a little leaner results in a little more hp at WOF in the upper rpm range

now tell me I am full of sh!t, just got lucky, have no clue, stop attacking people, etc etc
 
12.5:1 is VERY rich for ordinary running.

You'd generally only expect to see that sort of reading on hard acceleration.
When it would be puffing black smoke, in serious quantities.

Injected engines, some of them anyway, are apparently capable of lean running down to as low as 24:1.
Has to be VERY light running to achieve that though.
As soon as any level of acceleration is required, it needs to be richened up, considerably...

Thats where the throttle position sensor comes into it.
 
Measured Air/Fuel Ratio for Optimization


Study this for mixture ratio vs power vs kaboom. Bottom graph mimics Peels 3 part mixture ratios.
Measured Air/Fuel Ratio for Optimization
 
Can we have a larger readable version please ?

It appears to plot specific fuel consumption against bmep, which doesn't particularly shed light on anything much ?
Performance motorcycles in particular have paid little attention to miserly fuel consumption - wasting fuel is the order of the day, almost ?
Race motorcycles even less so, although MotoGP bikes getting to the end of the race does come into play.
And even more so this upcoming season...

This also reminds of those little lines in bike magazine tests of old, where they quote the fuel consumption at various speeds.
The 2 that always amused were the Black Shadow achieving 100+ mpg, at 20 or 25 mpg, was it ?
And the BSA Bantam, that could do a claimed 150 mpg at a similar 25 mph or similar.
That means that a Bantam, with a 2.5 gal tank ?, could go more than 15 hours on a single tank of fuel ?
We always wondered HOW they achieved these tests results - who rode a Black Shadow or Bantam at those speeds to achieve those figures... ?

Its also worth pointing out with bmep figures that a single line shows about nothing - its the AREA under the 4 sided bmep graph that shows power output.
 
Of course, if we were going to allow unlimited air with the fuel, and run it as a diesel, then a whole new set of conditions apply.

Measured Air/Fuel Ratio for Optimization


Although the last time I looked, a Commando engine was not really set up for this, in the slightest...!
 
I'm interested in the comment about carburation needing to run rich when you are accelerating hard. Perhaps some carbs have pumps on then so you can whack them open without the engine gasping ? (loss of vacuum causing lean-ness ? When I ride any motorcycle, I feed the throttle on as though it is a two-stroke. If the carburation on my Seeley is even slightly rich at throttle mid-opening, it becomes sluggish. However I don't depend on the crank spinning up in response to the throttle, I keep it spinning high in the rev-range. If I get around a corner with low revs in slightly too high a gear and wind the throttle on, due to the heavy crank, the bike takes forever to get going. I just don't ride it that way. You need close ratio gears for racing a Commando, the standard box is useless.
 
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