Mass Air Flow
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Best Mass Air Flow Sensor (Review) 2020 – Top 10 Picks
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Forum made EFI?
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Is that an on-board MAP sensor, in the first picture, bottom centre?
MAFs are good for OEM applications where it isn't hard to engineer a plenum to assure smooth airflow over the sensor. A lot harder under the right constraints of a cowl, and in the turbulent, high pulse world of a single cylinder runner. There's gonna be some flow reversal, maybe even with fuel vapor. Tough on those wires that must be kept clean to function.Mass Air Flow
Best Mass Air Flow Sensor (Review) 2020 – Top 10 Picks
Nice collection of options but without matching documentationMass Air Flow
Best Mass Air Flow Sensor (Review) 2020 – Top 10 Picks
Adapting them is going to be difficult. With numbers like those above you can build a table or convert them to a formula. Sometimes finding the data is the hard part.
jbiplane
Well-Known Member
Exactly. For turbo emgines possible atach hose to.
If non turbo does it do barometric correction? I am having to design in double sensors for that with my turbo engine.
jbiplane
Well-Known Member
Yes. In general we are customer driven and can change our hardware as required if order quantity more than 20.
Free EFI tuner course at end of article.
www.hpacademy.com
Mass Air Flow Sensors vs Manifold Air Pressure Sensors | High Performance Academy
In a previous article, we have already looked at intake restrictions and how they can affect the power your engine makes. In this article we are going to delve a little deeper into the intake system and look at the mass airflow meter, what it does and its pros and cons. Improving the airflow...
Various ramblings of a lunatic.
The thing about Pratt and Whitney is the spark isn't varied. The spark is about 20 degrees BTDC to 22 degrees BTDC depending on engine and so it remains. Fixed. And so Air in lbs to Fuel in lbs is also fixed. Having a stationary spark advance greatly simplifies the equation. But this should not be dismissed. Obviously (at least in my mind) for aircraft engines there just isn't a need for a lot of latitude in spark advance/retard for efficient running of the engine in regards to aircraft operation. This translates to there is not a lot of need for variation in lbs air to lbs fuel in aircraft operation. While of course if you vary the spark advance by advancing it more or retarding it from 20/22 degrees BTDC you can vary the air fuel mixture so that peak pressure is around 16-18 degrees ATDC There is a finite latitude that this can be justified for the overwhelming amount of aircraft operations. The areas on each side of safety (excess heat or the lack of combustion altogether) are of necessity to be avoided and except for a few minutes for take-off or in the case of an emergency operations can be conducted around 80% power or less which constitutes for aircraft 16lbs air or more for each 1lb fuel.
Pollution. OK. Are you going to put a catalytic converter and a smog pump on you aircraft engine … yes or no? Because if it is no then WTF.
You can have somewhere around 50% power or lower set with air to fuel around 18lbs air to 1lb fuel and I have been on DC-6's that have done this or close to it because we could not get fuel at our normal refueling stop. We had backup in interim locations to land enroute and such power settings were tribal not book but worked, I cannot remember ever landing enroute.
The Air/Fuel lbs/lbs ratio is entirely dependent on total power required and you can lean to around 20lbs air per 1lb fuel at about 30% power before the engine quits.
Lets talk about 100% power. In my mind this is going to be for the majority of air-cooled engines that we are willing to develop at about and around 0.63hp per ci.. Power above this is in excess of 100% and cannot be maintained 24/7/365. This 0.63hp per ci is variable to a certain degree but a pretty consistent if you look at many aircraft engines. When you look at said engines do not look at maximum hp look at maximum except take-off hp instead. For example a Lycoming O-290-D2 rated as a 135hp engine with 140hp available for 2 minutes … so 290 ci times … 0.465 (not 0.63) = 134.85hp. Anyway 0.63 is generous and considers every effort to eliminate heat with exception to maintain induction or fuel temperatures within a predetermined range.
Power in excess of 100% in my mind is any power that cannot be maintained 24/7/365. If you use power that is time limited it is almost certainly in reality temperature limited and time is just a more convenient means for a pilot to deal with it. Empirically it is known within certain parameters that the engine will not exceed critical temperatures within a given amount of time.
Whenever you use power much in excess of 0.63hp per ci you are approaching or in the zone of time/vs/temperature unless elaborate methods are used to reduce the buildup of heat.
I question 49ci at 0.71hp per ci = 34.79hp or above to be able to maintain 24/7/365. I think it is perfectly rational for take-off and initial climb. There are a number of variables that change when you use propeller reduction and higher RPM's and we ain't talking about those variables direct drive.
The thing about Pratt and Whitney is the spark isn't varied. The spark is about 20 degrees BTDC to 22 degrees BTDC depending on engine and so it remains. Fixed. And so Air in lbs to Fuel in lbs is also fixed. Having a stationary spark advance greatly simplifies the equation. But this should not be dismissed. Obviously (at least in my mind) for aircraft engines there just isn't a need for a lot of latitude in spark advance/retard for efficient running of the engine in regards to aircraft operation. This translates to there is not a lot of need for variation in lbs air to lbs fuel in aircraft operation. While of course if you vary the spark advance by advancing it more or retarding it from 20/22 degrees BTDC you can vary the air fuel mixture so that peak pressure is around 16-18 degrees ATDC There is a finite latitude that this can be justified for the overwhelming amount of aircraft operations. The areas on each side of safety (excess heat or the lack of combustion altogether) are of necessity to be avoided and except for a few minutes for take-off or in the case of an emergency operations can be conducted around 80% power or less which constitutes for aircraft 16lbs air or more for each 1lb fuel.
Pollution. OK. Are you going to put a catalytic converter and a smog pump on you aircraft engine … yes or no? Because if it is no then WTF.
You can have somewhere around 50% power or lower set with air to fuel around 18lbs air to 1lb fuel and I have been on DC-6's that have done this or close to it because we could not get fuel at our normal refueling stop. We had backup in interim locations to land enroute and such power settings were tribal not book but worked, I cannot remember ever landing enroute.
The Air/Fuel lbs/lbs ratio is entirely dependent on total power required and you can lean to around 20lbs air per 1lb fuel at about 30% power before the engine quits.
Lets talk about 100% power. In my mind this is going to be for the majority of air-cooled engines that we are willing to develop at about and around 0.63hp per ci.. Power above this is in excess of 100% and cannot be maintained 24/7/365. This 0.63hp per ci is variable to a certain degree but a pretty consistent if you look at many aircraft engines. When you look at said engines do not look at maximum hp look at maximum except take-off hp instead. For example a Lycoming O-290-D2 rated as a 135hp engine with 140hp available for 2 minutes … so 290 ci times … 0.465 (not 0.63) = 134.85hp. Anyway 0.63 is generous and considers every effort to eliminate heat with exception to maintain induction or fuel temperatures within a predetermined range.
Power in excess of 100% in my mind is any power that cannot be maintained 24/7/365. If you use power that is time limited it is almost certainly in reality temperature limited and time is just a more convenient means for a pilot to deal with it. Empirically it is known within certain parameters that the engine will not exceed critical temperatures within a given amount of time.
Whenever you use power much in excess of 0.63hp per ci you are approaching or in the zone of time/vs/temperature unless elaborate methods are used to reduce the buildup of heat.
I question 49ci at 0.71hp per ci = 34.79hp or above to be able to maintain 24/7/365. I think it is perfectly rational for take-off and initial climb. There are a number of variables that change when you use propeller reduction and higher RPM's and we ain't talking about those variables direct drive.
The power/CI is only valid for engines with the peak power at the same rpm. Your O-290 would have peak power somewhere around 2,750, the Briggs has it at 3,600rpm, a 30% difference.
Peak power on a conventional spark ignited engine is at an A/F ratio of around 13-13.5:1, with air-cooled engines running 12.5:1 for internal cooling.
Ignition timing in the direct-drive rpm range can be fixed at 22-30deg, the actual value depends on single/dual ignition, bore diameter, combustion chamber shape and compression ratio. The big issue is to retard it to near TDC for starting to prevent kick-back.
If you need to run your engine at 100% power in cruise you are either racing, in an emergency or have the wrong engine.
I’m running my Rotax 912 at WOT from SL to 9,500’ (20min) but not 100% power (5,300rpm), well within the Rotax guidelines, burning 26 lph at SL and about 24 lph at altitude, then 17-18 lph cruising.
Peak power on a conventional spark ignited engine is at an A/F ratio of around 13-13.5:1, with air-cooled engines running 12.5:1 for internal cooling.
Ignition timing in the direct-drive rpm range can be fixed at 22-30deg, the actual value depends on single/dual ignition, bore diameter, combustion chamber shape and compression ratio. The big issue is to retard it to near TDC for starting to prevent kick-back.
If you need to run your engine at 100% power in cruise you are either racing, in an emergency or have the wrong engine.
I’m running my Rotax 912 at WOT from SL to 9,500’ (20min) but not 100% power (5,300rpm), well within the Rotax guidelines, burning 26 lph at SL and about 24 lph at altitude, then 17-18 lph cruising.
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BrianW
Well-Known Member
Is a mass flow sensor barometrically corrected?
If a sensor measures mass it is inherently barometrically correct.
All you then need is an appropriate mass-rate of fuel, finely divided to hit the magic ratio.
If a sensor measures mass it is inherently barometrically correct.
All you then need is an appropriate mass-rate of fuel, finely divided to hit the magic ratio.
I agree, for what that's worth. But an additional complication arises with temperature. In theory, any effects of temperature on the density of the incoming air volume would already be included in a measure of its mass. But, almost all modern MAFs work by detecting the air's cooling effect on a heated wire (more air molecules flowing over the wire=more cooling). Obviously, if we have two air volumes of equal mass and density, but one is cooler, it will take away more heat from the wire. So the MAF sensor requires a temperature sensor and correction logic that may be less critical for a speed density (i.e. MAP and RPM) system.
Bille Floyd
Well-Known Member
- Joined
- Sep 26, 2019
- Messages
- 405
What you guys are saying here , might get explained by the (Why)for kawazakie
250cc dirt bike adopted (2) EFI's for low and high rpm ; but no other manufacturer did
Can you explain it to me please ; i read what they said below, but don't understand it ?
Bille
250cc dirt bike adopted (2) EFI's for low and high rpm ; but no other manufacturer did
Can you explain it to me please ; i read what they said below, but don't understand it ?
TEN THINGS YOU NEED TO KNOW ABOUT DUAL-FUEL INJECTION | Motocross Action Magazine
Motocross bikes have a single-injector — except one
motocrossactionmag.com
Bille
The Kawasaki system is what is commonly known as "staged injection," and the write-up looks to have a big dose of marketing mixed in. I don't know about the claimed particulars of the advantages of staged injectors in this high rev 2 stroke application. I do know that staged injection is well understood, and I strongly suspect the other players in that market segment would implement it if they saw an advantage. With improvements in the injectors themselves, staged injection is less important than it used to be.
Bille Floyd
Well-Known Member
- Joined
- Sep 26, 2019
- Messages
- 405
@ Vigilant1
Thanks !!
Bille
Thanks !!
Bille
BrianW
Well-Known Member
Hmmmm......Constant volume, constant density, constant mass and different temperatures???
No can do! Obviously? <g>
Any suggestions/ideas about suitable crank (aka "RPM") sensors for use in triggering a simple analog EFI system on a small industrial engine? One trigger per rev would be best, but every other rev is okay, too. There's a lot of magnetic "stuff" going on with the stock flywheel (magnets for the alternator windings mounted behind the flywheel and magnets for the ignition magnetrons mounted at rim), which makes me suspect that using a Hall effect sensor might pose some challenges.
-- The B&S OEM system apparently uses a Hall effect "missing tooth" sensor. Okay for their purposes, but requires some signal processing to detect the missing tooth (fine for a real digital EFI system, not great for a simple analog EFI system). Anyway, where they've installed it seems to work for them.
-- Maybe use a Hall effect pickup with its own sender "tab" on the flywheel? A small nub sticking above the face of the flywheel might be sufficient.
-- Perhaps use an inductive or capacitive pickup on a spark plug wire? I have seen some circuits that might work for this, but one potential issue is the low strength of the signal produced by the "wasted spark." Without the high-pressure mix in the combustion chamber, the strength of the "wasted spark" is apparently a lot weaker than the "main" spark, and so getting a good trigger from it might be hit or miss.
-- A separate (lightweight) wheel and sensor on the PTO side of the engine? This gets everything far away from magnets of the flywheel, but introduces "another thing."
-- The B&S OEM system apparently uses a Hall effect "missing tooth" sensor. Okay for their purposes, but requires some signal processing to detect the missing tooth (fine for a real digital EFI system, not great for a simple analog EFI system). Anyway, where they've installed it seems to work for them.
-- Maybe use a Hall effect pickup with its own sender "tab" on the flywheel? A small nub sticking above the face of the flywheel might be sufficient.
-- Perhaps use an inductive or capacitive pickup on a spark plug wire? I have seen some circuits that might work for this, but one potential issue is the low strength of the signal produced by the "wasted spark." Without the high-pressure mix in the combustion chamber, the strength of the "wasted spark" is apparently a lot weaker than the "main" spark, and so getting a good trigger from it might be hit or miss.
-- A separate (lightweight) wheel and sensor on the PTO side of the engine? This gets everything far away from magnets of the flywheel, but introduces "another thing."
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Gonna drag out all that discredited Ideal Gas Law flimflam, are ye?
I should have said: With decreasing temperature, the passing gasses take an increasingly large amount of heat from the hot wire in the MAF for the same air mass. This effect is larger than would be predicted based solely on the increased density due to the lower gas temperature. For this reason, readings from hot-wire MAF sensors require temperature compensation.
Depends some on which side of the lawnmower engine you are going to put the propeller on. If you are going to mount it on the "conventional SD-1" side of the engine then the other side possibly hasn't much on it, it may even be "bobbed" off and a dust-cap installed over. So maybe it is easy to put a pickup there and not "bob-it" quite so much. If you are going TiPi's proposed route I am unclear on what he is putting on the PTO side other than the propeller IE since the propeller can completely replace the flywheel maybe a vestige of the flywheel is retained on the side opposite or maybe it is abandoned completely and all the guts swapped over to the propeller side? From what has been discussed on this forum about harmonics on both sides of the crankshaft even though it is more work a complete swap to the propeller side may be prudent? If so a small magnet and pickup on the original flywheel side may be easy enough?
jbiplane
Well-Known Member
I am in process of development of ECU which will integrated to throttle body 70x70mm board at moment. One sided to make cheaper. I afraid it will take few month to complete.
But I have other simple idea - want to share. May be someone will implement or help me to implement. I believe it is possible create simplest ECU which will calculate injection duration and ignition angle based only on rpm. No other sensors. Small tune can be performed by mechanical fuel pressure regulator. In future it can be separate board which regulate fuel pressure by simple circuit board (themperature and barometric corrections). I would be happy to find someone who can help me in electronics to do this joint project from the scratch and will do all mechanical stuff and testing.
In this case processor should perform 1000th times fewer calculations will be cheap and reliable.
But I have other simple idea - want to share. May be someone will implement or help me to implement. I believe it is possible create simplest ECU which will calculate injection duration and ignition angle based only on rpm. No other sensors. Small tune can be performed by mechanical fuel pressure regulator. In future it can be separate board which regulate fuel pressure by simple circuit board (themperature and barometric corrections). I would be happy to find someone who can help me in electronics to do this joint project from the scratch and will do all mechanical stuff and testing.
In this case processor should perform 1000th times fewer calculations will be cheap and reliable.
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