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Dyno run on 18V engine. Comments?

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B-racer Avatar
B-racer Jeff Schlemmer
Shakopee, MN, USA   USA
1950 Willys Jeep Pickup "Ratrod"
1971 MG MGB ~ For Sale ! ~
2014 Dodge Charger
Your old engine was in a very poor state of tune. I've never seen an MG B-series on the dyno that didn't make 70 hp - at least after adjusting fuel mixture and timing.

Then again, I'd never pay a dyno operator if they can't supply an AFR graph either. Simple basics. $250 or less will give them a sensor to input AFR into any dyno software.
I'd want to see the rich misfires you're having that give an "unsmooth" chart as your is. I know there are smoothing features they can turn on to make it look better, but generally speaking, an RFI based misfire (electronic ignition) causes what you see on your chart. If they fix their scaling, the graph will overlap properly too.



jeff@advanceddistributors.com

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pinkyponk Avatar
pinkyponk Gold Member Adrian Page
Berwick, NS, Canada   CAN
In reply to # 3885723 by B-racer Your old engine was in a very poor state of tune. I've never seen an MG B-series on the dyno that didn't make 70 hp - at least after adjusting fuel mixture and timing.

Then again, I'd never pay a dyno operator if they can't supply an AFR graph either. Simple basics. $250 or less will give them a sensor to input AFR into any dyno software.
I'd want to see the rich misfires you're having that give an "unsmooth" chart as your is. I know there are smoothing features they can turn on to make it look better, but generally speaking, an RFI based misfire (electronic ignition) causes what you see on your chart. If they fix their scaling, the graph will overlap properly too.

I'm not sure an AFR graph would be much use to you, Jeff. An air/fuel graph would show misfires as lean. (We've gone over this before.) If the air/fuel charge does not fire, all the oxygen in it that didn't burn is detected by the oxygen sensor... which can only detect oxygen... not fuel. An actual misfire caused by too much fuel would be accompanied by black smoke belching from the exhaust. I think Thomas and the dyno operator would have noticed that.

Adrian



Home built Eaton M62 Supercharger with 7.6psi boost, 8:1 compression, custom "supercharger" cam from Schneider Cams, Mikuni HSR48 Carburetor, cold air intake, ported head, matched manifolds, CB Performance computerized ignition, Fidanza 9 pound flywheel, Maxspeeding rods with Teflon wrist pin buttons.

MG-Maxx Avatar
MG-Maxx Silver Member Charles Waugh
West Haven, CT, USA   USA
1979 MG MGB MkIII "Rumpelstiltskin"
2008 Chevrolet HHR
Just for more info.

I attended a local Dino day. Only a few showed up. A Healey with a 2.4l(IIRC). He had the most at both numbers over 100.

There were 4 MGBs.

The chrome bumper had 64rwhp. Rubber had 54 rwhp. There was a 77 that had a newly built race style motor. He had 87rwhp torque was around 100ftlbs.

My 3.5l V6 had a little more



Chuck
Hamden, CT

79 MGB - Rumpelstiltskin
Just awakened after a 10 year slumber.
GM 60V6 Gen 3 - 3.5L EFI V6 T-5.

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B-racer Avatar
B-racer Jeff Schlemmer
Shakopee, MN, USA   USA
1950 Willys Jeep Pickup "Ratrod"
1971 MG MGB ~ For Sale ! ~
2014 Dodge Charger
Adrian, when an AFR gauge reads 12:1 instead of 13:1, what does that mean to you? Is 12:1 AFR more rich? Or is 13? This isn't hard to decipher. We're talking about fine tuning here - not gross overfueling.



jeff@advanceddistributors.com

pinkyponk Avatar
pinkyponk Gold Member Adrian Page
Berwick, NS, Canada   CAN
In reply to # 3887540 by B-racer Adrian, when an AFR gauge reads 12:1 instead of 13:1, what does that mean to you? Is 12:1 AFR more rich? Or is 13? This isn't hard to decipher. We're talking about fine tuning here - not gross overfueling.

I'd say either was pretty close to right for maximum power. Neither ratio would cause misfires... but if they did they would show as lean.

Adrian



Home built Eaton M62 Supercharger with 7.6psi boost, 8:1 compression, custom "supercharger" cam from Schneider Cams, Mikuni HSR48 Carburetor, cold air intake, ported head, matched manifolds, CB Performance computerized ignition, Fidanza 9 pound flywheel, Maxspeeding rods with Teflon wrist pin buttons.

B-racer Avatar
B-racer Jeff Schlemmer
Shakopee, MN, USA   USA
1950 Willys Jeep Pickup "Ratrod"
1971 MG MGB ~ For Sale ! ~
2014 Dodge Charger
Adrian, how can a rich partially burned mixture always show lean? That makes NO SENSE. Its ridiculous. I know what's rattling through your mind, but it doesn't work that way. . When fuel is in the tailpipe, whether its oxygen or gasoline, the meter reads excess oxygen as rich. A lean mixture is composed of low oxygen levels. Its full of other gasses, but not oxygen. The components of air coming out of the tailpipe include a seriously reduced amount of oxygen. High oxygen levels throughout average running does not equate to a lean mixture. If it did, we could never trust an O2 gauge. You assume the mild misfires I'm speaking of mean a zero-burn cylinder cycle, flooding the exhaust with fuel and air. I'm not talking about no spark. I'm talking about the far more common issue - weak spark, improperly timed spark, pre-triggered spark caused by RFI or EMI where the coil hasn't fully charged. Mild misfires. Many times you can also see a double-spark scenario where the coil discharges twice as frequently as it should resulting in a 30 degree dwell instead of 60 degrees.

In the end, mild misfires cause a loss of 5-15% power. They're found in 1/3 - 1/4 of all MGBs on the road and most people who have these issues aren't even aware of what they're missing. Sometimes they're caused by old high resistance plug wires, fouled plugs with weak spark, an improperly curved distributor that causes a severe rich symptom during part of the rpm range, running the wrong needles in your carbs, the wrong or no dashpot oil, etc... Basically anything that can stop the spark plug from providing a clean, proper, consistent, precise spark.

This argument is similar to one I had at MG2008 with a man in the parking lot. He argued that engine vacuum starts at zero at idle and reads the highest at wide open throttle. He had never driven with a vacuum gauge on his car, but he knew that's how it worked and I was dead wrong no matter what I said. Don't be that guy. I'm guessing Adrian has never seen how the AFR graph is affected by mild misfires on a dyno, and how it looks in comparison when you resolve the problem.



jeff@advanceddistributors.com

pinkyponk Avatar
pinkyponk Gold Member Adrian Page
Berwick, NS, Canada   CAN
In reply to # 3889058 by B-racer Adrian, how can a rich partially burned mixture always show lean? That makes NO SENSE. Its ridiculous. I know what's rattling through your mind, but it doesn't work that way. . When fuel is in the tailpipe, whether its oxygen or gasoline, the meter reads excess oxygen as rich. A lean mixture is composed of low oxygen levels. Its full of other gasses, but not oxygen. The components of air coming out of the tailpipe include a seriously reduced amount of oxygen. High oxygen levels throughout average running does not equate to a lean mixture. If it did, we could never trust an O2 gauge. You assume the mild misfires I'm speaking of mean a zero-burn cylinder cycle, flooding the exhaust with fuel and air. I'm not talking about no spark. I'm talking about the far more common issue - weak spark, improperly timed spark, pre-triggered spark caused by RFI or EMI where the coil hasn't fully charged. Mild misfires. Many times you can also see a double-spark scenario where the coil discharges twice as frequently as it should resulting in a 30 degree dwell instead of 60 degrees.

In the end, mild misfires cause a loss of 5-15% power. They're found in 1/3 - 1/4 of all MGBs on the road and most people who have these issues aren't even aware of what they're missing. Sometimes they're caused by old high resistance plug wires, fouled plugs with weak spark, an improperly curved distributor that causes a severe rich symptom during part of the rpm range, running the wrong needles in your carbs, the wrong or no dashpot oil, etc... Basically anything that can stop the spark plug from providing a clean, proper, consistent, precise spark.

This argument is similar to one I had at MG2008 with a man in the parking lot. He argued that engine vacuum starts at zero at idle and reads the highest at wide open throttle. He had never driven with a vacuum gauge on his car, but he knew that's how it worked and I was dead wrong no matter what I said. Don't be that guy. I'm guessing Adrian has never seen how the AFR graph is affected by mild misfires on a dyno, and how it looks in comparison when you resolve the problem.

I certainly don't want to be that guy! Of course you believe I am dead wrong no matter what I say. I must admit, I did understand a misfire to mean the charge did not burn... either partially or completely.


"how can a rich partially burned mixture always show lean? " An engine running at a steady state of 12:1 will show leaner than 12:1 if it begins to misfire. The un-used oxygen from the misfire is read by the O2 sensor as leaner than what was intended. I abbreviated this to misfires show as lean.

"When fuel is in the tailpipe, whether it's oxygen or gasoline, the meter reads excess oxygen as rich." Oxygen is not a fuel and does not burn. Combustion is the chemical reaction of fuel, heat and oxygen. Oxygen accelerates the reaction. If the oxygen does not find fuel to combine and react with it will pass into the exhaust where the O2 sensor reads it. It cannot detect fuel, only oxygen. If it detects more oxygen than it expects to see it interprets this as a lean condition.

"A lean mixture is composed of low oxygen levels." This is incorrect. Obviously an un-burned lean mixture is rich in oxygen and low in fuel.(too much air, not enough fuel = lean) An un-burned lean mixture will be read as lean on an O2 sensor. If oxygen is unable to combine with fuel molecules because there is insufficient fuel to combine with the oxygen, the oxygen passes into the exhaust. This excess oxygen is read by the O2 sensor and the gauge displays it as lean.(too much air, not enough fuel = lean) Remember that the stoichiometric ratio of 14.7:1 is by weight. 14.7 pounds of air to 1 pound of fuel. 14.7 pounds of air is about 1400 gallons. A pound of gasoline is about a pint and a half.

"High oxygen levels throughout average running does not equate to a lean mixture." High oxygen levels in the cylinder is a good thing if it is mixed with an appropriate amount of fuel. High oxygen levels in the exhaust is an indication of a lean mixture or misfires.

Here is a ink to everything you could ever possibly want to know about misfires: https://www.searchautoparts.com/motorage/technicians/electrical/misfire-detection

And a really interesting article from Innovate about O2 sensors and the effect of exhaust leaks on A/F readings: http://blog.innovatemotorsports.com/how-an-exhaust-leak-affects-wideband-o2-sensor-readings/

Adrian
(Who is going out to tinker with his MG)

Edit: corrected a typo about weight of gasoline.



Home built Eaton M62 Supercharger with 7.6psi boost, 8:1 compression, custom "supercharger" cam from Schneider Cams, Mikuni HSR48 Carburetor, cold air intake, ported head, matched manifolds, CB Performance computerized ignition, Fidanza 9 pound flywheel, Maxspeeding rods with Teflon wrist pin buttons.



Edited 4 time(s). Last edit at 2019-02-12 07:41 AM by pinkyponk.

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