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Tuning motorcycle carburettors 6
- Thread starter Brett43
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patprimmer
New member
A wide band oxygen sensor for each carburetor and a data logger.
I will take a wild guess that it is one carburettor per cylinder with IR manifolds.
Slightly cheaper option is one or two oxygen sensors and an exhaust gas temperature sensor on each pipe with a data logger. Move the oxygen sensor around for comparison tests to get a base line for the EGTs.
Regards
eng-tips, by professional engineers for professional engineers
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I will take a wild guess that it is one carburettor per cylinder with IR manifolds.
Slightly cheaper option is one or two oxygen sensors and an exhaust gas temperature sensor on each pipe with a data logger. Move the oxygen sensor around for comparison tests to get a base line for the EGTs.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
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Of course I have been jetting carbs "by ear" for performance for some 50 odd years now and I can tell you that, even with all that experience, I would still recommend the dyno to set up the carbs on a bike...Trust me, it will be cheaper and faster to get it right the first time and avoid the risk of internal engine damage. Dyno time for bikes may take a little looking but, Time to jet a bike is minimal and dyno time is usually negotiable, depending on your bike and personality. I have seen "jetting check" adds for $35/hr. in some mags (I just had a portable dyno set up at my shop and did a break in and jet/power check on a new engine for my Mini at a cost of $125/hr.).
If you still insist on doing it like I did it in the 50's, try the local magazine/book store. There is enough on this subject to keep you busy for months! Reading plugs correctly is an easy thing to learn but requires LOTS of experience to be 'spot on'.
Rod
If you still insist on doing it like I did it in the 50's, try the local magazine/book store. There is enough on this subject to keep you busy for months! Reading plugs correctly is an easy thing to learn but requires LOTS of experience to be 'spot on'.
Rod
- Thread starter
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They have a dealer resource link on their page which should direct you to the nearest shop carrying their equipment.
That or find a local racetrack. Here in the states, you can often schedule dyno time on race weekends as at least one local shop will have one there.
patprimmer
New member
I am sure there are plenty in the Melbourne Yellow pages.
Major motor cycle dealers should be able to advise.
Local race bike clubs should be able to advise.
The administrators at Phillip Island should be able to help.
Until I looked it up, I thought you must be out in the boondocks to even ask the question, not just out of Melbourne.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
Major motor cycle dealers should be able to advise.
Local race bike clubs should be able to advise.
The administrators at Phillip Island should be able to help.
Until I looked it up, I thought you must be out in the boondocks to even ask the question, not just out of Melbourne.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
- Thread starter
- #7
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Likely cost. If you're just looking to tune a carbuerated bike on occasion, I'm guessing the sensors and channel are going to set you back more than $60 (approximate cost of a dyno run up here...over $100 if you're tuning with one of the shop guys and making multiple runs to get your curve the way you want it).
The racers I know running FI bikes are using mapping software with their Power Commanders, then verifying the bands through their practice sessions. Frequent dyno runs are a bit pricey for club racers w/o serious sponsorship, at least in this neck of the woods.
As an FYI for me, how much did your data logging combo set you back?
The racers I know running FI bikes are using mapping software with their Power Commanders, then verifying the bands through their practice sessions. Frequent dyno runs are a bit pricey for club racers w/o serious sponsorship, at least in this neck of the woods.
As an FYI for me, how much did your data logging combo set you back?
I have about 1200.00 into the data logger if you include the 8 Exh gas temp sensors and a few othe misc sensors I have, not including the lap top that can be connected to it for real time monitering on my car tuning projects.
I guess my point is a dyno will tell you when your making peak HP, but Peak HP, comes in the "lean" area of A/F ratio
so you still need some sort of A/F metter with a Dyno to be safe. ( I tune Supercharged Mustangs, some with up to 40 psi of boost, small miscalculations can = many broken parts) with my setup I can look at EGT, Calculated A/F ratio thru the wide band 02, while changing the fuel injector pulse curve in real time (on a car anyway) the data logger works ok on a bike or for monitering on-going performance of a race car.
I guess my point is a dyno will tell you when your making peak HP, but Peak HP, comes in the "lean" area of A/F ratio
so you still need some sort of A/F metter with a Dyno to be safe. ( I tune Supercharged Mustangs, some with up to 40 psi of boost, small miscalculations can = many broken parts) with my setup I can look at EGT, Calculated A/F ratio thru the wide band 02, while changing the fuel injector pulse curve in real time (on a car anyway) the data logger works ok on a bike or for monitering on-going performance of a race car.
they sell products like what I have built myself
but they cost a whole lot more
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The dyno should have at least a wideband O2 sensor to sniff exhaust gas during the run. The carbs should be synced prior to showing up at the dyno. It should also have a good and properly operating ignition system. If you can be fairly certain your cylinders are all breathing and firing in a similar fashion dyno time will be reduced. If you are showing up at a dyno tuner to fix your bike rather than tune it you will need more than a single O2 and spend a lot more cash in the process.
Many think of dyno time as expensive yet they spend $500 on a pipe, $150 on a jet kit or $300 on a power commander and throw Shite loads of cash into polishing aluminum and painting body work. Then they say, $250 dollars to correctly set up a power commander or jet kit is too expensive.
Dyno time is cheap compared to what one spends on hot roddding and personal time testing on the street.
Additional note...your peak power will be found at 12.5 to 13.8 to 1. Not lean at all. Lean is mean is an old term and will lead to disaster. If you tune for peak power you will not be lean at all.
Many think of dyno time as expensive yet they spend $500 on a pipe, $150 on a jet kit or $300 on a power commander and throw Shite loads of cash into polishing aluminum and painting body work. Then they say, $250 dollars to correctly set up a power commander or jet kit is too expensive.
Dyno time is cheap compared to what one spends on hot roddding and personal time testing on the street.
Additional note...your peak power will be found at 12.5 to 13.8 to 1. Not lean at all. Lean is mean is an old term and will lead to disaster. If you tune for peak power you will not be lean at all.
"Additional note...your peak power will be found at 12.5 to 13.8 to 1. Not lean at all. Lean is mean is an old term and will lead to disaster. If you tune for peak power you will not be lean at all."
in a nut shell..your wrong and right, Peak HP will be achived at 14.7 to 1 A/F ratio the problem is we can not get a homogenous charge(fuel quality is another issue), but I do agree that the range you posted is the typical A/F ratio that most people find there
safe peak HP. on our race motor we have it dialed in to calculated A/F ratio of 14.1/1
street car: 89 Mustang 10.3 @ 132
Race Car: Mustang Pro Comp 6.45 @ 219
in a nut shell..your wrong and right, Peak HP will be achived at 14.7 to 1 A/F ratio the problem is we can not get a homogenous charge(fuel quality is another issue), but I do agree that the range you posted is the typical A/F ratio that most people find there
safe peak HP. on our race motor we have it dialed in to calculated A/F ratio of 14.1/1
street car: 89 Mustang 10.3 @ 132
Race Car: Mustang Pro Comp 6.45 @ 219
Am I the only one who uses a Vacuum gauge to balance the carbs and peak the power.
A vacuum guage is handy on occasion. Balancing multiple carbs is best done, if you have the skill, by sticking a length of small dia. hose/tubeing in your ear and the open end in the 'bell' of the carb. Old fashioned? You bet. Does it work? It has, for me, for 50 years! I have owned and used several carb balancing devices fron Uni-Syn to an electronic device that reads on a Sun Inst. CRT...I always end up with a piece of plastic hose stuck in my ear and a screwdriver! Just because something is not "new era" does not mean it doesn't work well. The 'old way' has one more advantage, it's a LOT faster. It is a skill (gift if you will) much like accurately setting valve lash...some can, most cannot!
Rod
Rod
- Thread starter
- #16
Hi,
Thanksagain for every body replying,
I have a dial carb balancer and all the carbs are balanced.
It is the air fuel ratio tha t is the problem because I have put pod filters on the carbies.
I have yet to find a dynotune place that is even remotely interested in answering my emails on pricing & when I could book it in!!!!
Thanksagain for every body replying,
I have a dial carb balancer and all the carbs are balanced.
It is the air fuel ratio tha t is the problem because I have put pod filters on the carbies.
I have yet to find a dynotune place that is even remotely interested in answering my emails on pricing & when I could book it in!!!!
14.7:1 is stoichiometric (meaning scientifically correct) but peak power never occurs there, as combustion chambers in almost every engine require more fuel for peak power. Tune an engine for 13.5:1 and measure the torque then lean out fuelling to 14:7:1 and check the power. You will see a drop in torque. As you lean out torque drops very quickly. As you go richer, that max power you will find torque drops off very slowly.
If you have a dyno with O2, you can test this for yourself. You’ll need an eddy current brake and real time torque reading or a least a programmable dyno to perform step and hold testing w/data logging. In my case, my dyno is programmable for step and hold, sweep and manual loading on the fly.
Otherwise reference:
The Internal Combustion Engine in Theory and Practice: Vol. 1: Thermodynamics, Fluid Flow, Performance
ISBN: 0262700263 Format: Paperback, 574pp Pub. Date: March 1985 Publisher: MIT Press Edition Description: Revised Edition Number: 2
Internal Combustion Engine in Theory and Practice: Vol. 2: Combustion, Fuels, Materials, Design
ISBN: 0262700271 Format: Paperback, 800pp Pub. Date: March 1985 Publisher: MIT Press Edition Description: 2nd ed., rev Edition Number: 2
These explain the curves of Air Fuel ratios and their effect on power production using very easy to read graphs including those showing combustion pressure and knock.
Sounds like you are in a tough place to get a good tuner. Keep hunting around to find a dyno with wideband O2 or 4-gas analyzer. That will get you tuned up right.
If you have a dyno with O2, you can test this for yourself. You’ll need an eddy current brake and real time torque reading or a least a programmable dyno to perform step and hold testing w/data logging. In my case, my dyno is programmable for step and hold, sweep and manual loading on the fly.
Otherwise reference:
The Internal Combustion Engine in Theory and Practice: Vol. 1: Thermodynamics, Fluid Flow, Performance
ISBN: 0262700263 Format: Paperback, 574pp Pub. Date: March 1985 Publisher: MIT Press Edition Description: Revised Edition Number: 2
Internal Combustion Engine in Theory and Practice: Vol. 2: Combustion, Fuels, Materials, Design
ISBN: 0262700271 Format: Paperback, 800pp Pub. Date: March 1985 Publisher: MIT Press Edition Description: 2nd ed., rev Edition Number: 2
These explain the curves of Air Fuel ratios and their effect on power production using very easy to read graphs including those showing combustion pressure and knock.
Sounds like you are in a tough place to get a good tuner. Keep hunting around to find a dyno with wideband O2 or 4-gas analyzer. That will get you tuned up right.
patprimmer
New member
14.7 is typically the chemically balanced air to fuel ratio for commercially available petrol.
This means that if combustion is complete, all the fuel and all the free oxygen in the air is consumed.
In point of fact, the quality of the mix of air and fuel is never good enough for all fuel and all free oxygen to react or combine in the time the fuel mixture is in the combustion chamber and the piston is in a position to gain from the expansion caused by the heat of the combustion.
To get maximum power, you need to use all the air early in the power stroke so the pressure gets maximum exposure to the piston as it moves down. This requires extra fuel so there is a better chance of some fuel molecule being close to all the oxygen molecules, but not so many that it displaces to much air, or so that the combustion is so incomplete that soot deposits become a problem.
To get maximum economy you need an excess of air so that all the fuel is consumed, but there needs to be enough to sustain a stable flame front and to prevent free oxygen reacting with internal engine parts.
Only tests will determine the best ratio for either situation. Lots of interrelated variable exist that have an influence, including size and distribution of fuel particles, temperature of intake air, temperature of manifold and cylinder and cylinder head walls, air speed, shear in the airflow and turbulence, turbulence in the combustion chamber, combustion chamber size and shape, quality of ignition system, compression ratio etc.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
This means that if combustion is complete, all the fuel and all the free oxygen in the air is consumed.
In point of fact, the quality of the mix of air and fuel is never good enough for all fuel and all free oxygen to react or combine in the time the fuel mixture is in the combustion chamber and the piston is in a position to gain from the expansion caused by the heat of the combustion.
To get maximum power, you need to use all the air early in the power stroke so the pressure gets maximum exposure to the piston as it moves down. This requires extra fuel so there is a better chance of some fuel molecule being close to all the oxygen molecules, but not so many that it displaces to much air, or so that the combustion is so incomplete that soot deposits become a problem.
To get maximum economy you need an excess of air so that all the fuel is consumed, but there needs to be enough to sustain a stable flame front and to prevent free oxygen reacting with internal engine parts.
Only tests will determine the best ratio for either situation. Lots of interrelated variable exist that have an influence, including size and distribution of fuel particles, temperature of intake air, temperature of manifold and cylinder and cylinder head walls, air speed, shear in the airflow and turbulence, turbulence in the combustion chamber, combustion chamber size and shape, quality of ignition system, compression ratio etc.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
I'd say where on the same page, I have those books and there pretty worn out from years of use.
We have dimpled our intake runners to create small eddy's
to help in A/F mixing and actually slightly reduce air flow
(Yates SB ford Heads -nascar take offs) that where opened up a bit much for supercharged use - the increased turbulance allowed us to tighten our A/F a bit.
some where I have the dyno data in excel there is no mistake in our gains in HP and torque
that said, I consider myself a good "Hobbie" tuner, better then most of the so called Pro's in the new england area anyway- there are not that many people out there with 1200 hp small blocks.
We have dimpled our intake runners to create small eddy's
to help in A/F mixing and actually slightly reduce air flow
(Yates SB ford Heads -nascar take offs) that where opened up a bit much for supercharged use - the increased turbulance allowed us to tighten our A/F a bit.
some where I have the dyno data in excel there is no mistake in our gains in HP and torque
that said, I consider myself a good "Hobbie" tuner, better then most of the so called Pro's in the new england area anyway- there are not that many people out there with 1200 hp small blocks.
whitevette
Mechanical
Hi, Brett43!
You asked "How is the best way to tune multiple carbs on my bike?" There followed a long laundry list of suggestions...ranging from mild to wild!
Dyno time is expensive...and subject to the whims of the operator! I found only ONE post by a gentleman who knew what was real!
Put a piece of plastis tubing in your ear...and synchronize bt the sound of the hiss! This will balance the airflows...and the mixtures to the cylinders. Then, play with the 'plug colors! Either use a "Colortune" sparkplug...or, there are lots of color pics on the 'Net / in books (remember books? LOL). Find your right colors, your right "hiss"...balance, and ride on! -whitevette
You asked "How is the best way to tune multiple carbs on my bike?" There followed a long laundry list of suggestions...ranging from mild to wild!
Dyno time is expensive...and subject to the whims of the operator! I found only ONE post by a gentleman who knew what was real!
Put a piece of plastis tubing in your ear...and synchronize bt the sound of the hiss! This will balance the airflows...and the mixtures to the cylinders. Then, play with the 'plug colors! Either use a "Colortune" sparkplug...or, there are lots of color pics on the 'Net / in books (remember books? LOL). Find your right colors, your right "hiss"...balance, and ride on! -whitevette
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