Painless "Perfect Engine Management System"
01-19-2005, 01:10 PM
#21
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Originally Posted by Speartech
Maybe. Does MS use a full time baro input?? If not, I don't think it could know the pressure change that occurs with altitude, unless it has an algorithm to check for it.
the map sensor takes the reading of the absolute air preasure in the manifold (Manifold Absolute Preasure == MAP) which is self compensating because as the outside air preasure drops the manifold absolute preasure drops.
More Than Zero
01-19-2005, 02:20 PM
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Thanks for the comments and info, dieselgeek. Actually I'm trying to minimize the risk involved by researching the options. I'm looking right now at modifying a stock setup, or using the MEFI (either from a marine engine or Painless), or using the Megasquirt if it meets the requirements. I'm looking at at least 8 months to a year before I need to make a decision and start actually installing the engine controller, whatever it ends up being.
I'm of the opinion that automotive electronic engine management should be as safe as the antiquated stuff on Lycomings and Continentals. In over 40 years of driving, I've never had an engine suddenly quit because of ignition or fuel delivery. Lots of that time obviously has been behind engines using really primitive systems compared to what we have now. I did, however, have a 150hp Lycoming fail to start one time and found the "dual" magneto detached from the engine....both mags had a common shaft...so much for redundancy. Glad it happened before flight.
The engine is going on a SAL Mustang, a 2/3 P-51 replica. http://home.comcast.net/~ogoodwin/Mustang.html for pictures and comments.
In the case of the Megasquirt, am I correct in assuming that in SD mode, the computer takes throttle position, MAP, and rpm, and adjusts the mixture to fit preexisting tables telling it what the fuel input should be for those conditions, changing the fuel flow to fit changing perameters as altitude/temperature/baro pressure changes on climb or descent? I assume this is the same way a modified stock PCM or MEFI would also accomplish fuel control?
Thanks for the offer of help, as you can tell from my questions, I need all I can get:-) I'll gladly accept any help and comments I get.
Olen
I'm of the opinion that automotive electronic engine management should be as safe as the antiquated stuff on Lycomings and Continentals. In over 40 years of driving, I've never had an engine suddenly quit because of ignition or fuel delivery. Lots of that time obviously has been behind engines using really primitive systems compared to what we have now. I did, however, have a 150hp Lycoming fail to start one time and found the "dual" magneto detached from the engine....both mags had a common shaft...so much for redundancy. Glad it happened before flight.
The engine is going on a SAL Mustang, a 2/3 P-51 replica. http://home.comcast.net/~ogoodwin/Mustang.html for pictures and comments.
In the case of the Megasquirt, am I correct in assuming that in SD mode, the computer takes throttle position, MAP, and rpm, and adjusts the mixture to fit preexisting tables telling it what the fuel input should be for those conditions, changing the fuel flow to fit changing perameters as altitude/temperature/baro pressure changes on climb or descent? I assume this is the same way a modified stock PCM or MEFI would also accomplish fuel control?
Thanks for the offer of help, as you can tell from my questions, I need all I can get:-) I'll gladly accept any help and comments I get.
Olen
Originally Posted by dieselgeek
Megasquirt doesn't necessarily need an O2 sensor, and it's MAP sensor helps it compensate for air density.
What you'd set on the ground would work all the way up until you run out of air, but it would keep the mixture perfect.
I would still try to get an O2 sensor in there, for both logging purposes and corrections on the fly (pun intended).
Funny you bring this all up - I'm a private pilot, and also an EAA member.
You DO realize the extreme chances you take when installing ANY kind of aftermarket EFI on the motor and go for a flight? I'm sure you've heard this a thousand times. What kind of plane is this going into?
I'd be glad to help, and there's a thread on MS-EFI.com about guys who use Megasquirt in their airplanes. Crazy bunch, but I *DO* have to point out that I have yet to see a single megasquirt failure while driving, and Ive built a number of them already...
I'd consider a dual-megasquirt setup that you could switch manually between. It wouldn't be that hard to do. Ask any questions you like, this is interesting!
-scott
What you'd set on the ground would work all the way up until you run out of air, but it would keep the mixture perfect.
I would still try to get an O2 sensor in there, for both logging purposes and corrections on the fly (pun intended).
Funny you bring this all up - I'm a private pilot, and also an EAA member.
You DO realize the extreme chances you take when installing ANY kind of aftermarket EFI on the motor and go for a flight? I'm sure you've heard this a thousand times. What kind of plane is this going into?
I'd be glad to help, and there's a thread on MS-EFI.com about guys who use Megasquirt in their airplanes. Crazy bunch, but I *DO* have to point out that I have yet to see a single megasquirt failure while driving, and Ive built a number of them already...
I'd consider a dual-megasquirt setup that you could switch manually between. It wouldn't be that hard to do. Ask any questions you like, this is interesting!
-scott
01-19-2005, 02:25 PM
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M_T_O, I'll look into the anti reversion cone idea. It might even help make the short stacks more efficient...I realize I'll be losing power from them anyway, compared to headers. There's just not room in my cowling for headers, though. The whole engine has to fit into a space only about 26 inches wide. I can see the advantage of O2 sensors, but just can't figure a way to make them work at this point.
Olen
Olen
Originally Posted by M_T_0
I agree 100% with the above, The Megasquirt would be what I would use But I don't want the liability for this one. and no you can run it in SD mode which just looks at map and rpm (and a few others) but the O2 gives you feadback to fine tune itself on the fly lol pun intended lol.
but anyway good luck with this one.
More Than Zero
PS: the problem with the O2 will be that with only 10" of exhaust tube you will be getting a lot of o2 back up the exhaust from the outside and it will read lean all the time. you might try to incorperate an antireversion cone into the exhaust stacks and install the O2 upstream of that to get a good reading.
I belive that MS is now incorperating knock sensors into the system you can use the stock LS2 or ls1 sensors threaded into the exterior of the block.
but anyway good luck with this one.
More Than Zero
PS: the problem with the O2 will be that with only 10" of exhaust tube you will be getting a lot of o2 back up the exhaust from the outside and it will read lean all the time. you might try to incorperate an antireversion cone into the exhaust stacks and install the O2 upstream of that to get a good reading.
I belive that MS is now incorperating knock sensors into the system you can use the stock LS2 or ls1 sensors threaded into the exterior of the block.
01-19-2005, 02:56 PM
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Originally Posted by Speartech
Maybe. Does MS use a full time baro input?? If not, I don't think it could know the pressure change that occurs with altitude, unless it has an algorithm to check for it.
Not maybe, but definitely. THe Speed Density algorithm in Megasquirt already compensates, on teh fly, for differences in density altitude: the MAP pressure changes for a given volume of airmass based on the oxygen density... in other words, the lower MAP reading at higher altitude will compensate for less oxygen to burn.
There IS a small concern because at higher altitude, BACKPRESSURE goes down, therefore Volumetric Efficiency goes up, and you actually need to RICHEN the mixture a little to compensate for this. There's a built in "7.7%-per-5000 foot difference in elevation based on MAP" - those numbers are derived from NASA and are also in all the OEM manufacturer's ECMs, however that might be off by a fraction of a percent at higher altitudes. If you want absolute correction, you can install a "MegaBaro" circuit for on the fly barometric measurements - OR the easier way is to figure out how an O2 sensor can be made to work.
I know at the dyno shop they use an O2 sensor (wideband) only a few inches up the tailpipe, farther from the combustion source than in your aircraft, and no closer to "open air" than in your proposed stack design: I think you can calibrate a wideband to make it work for EGO correction, and set it to a reasonbale limit like no more than 15% fuel added or taken away.
There's no question a MS would run your aircraft engine flawlessly. What I would suggest worrying about is setting up an inexpensive, redundant Megasquirt unit as a backup. You won't be able to do a dual ignition setup unless you figure out how to get two separate sparkplugs in the heads for each cylinder, but you could do dual EDIS modules, dual megasquirts, and dual ECT/MAT/MAP sensor setups using a simple A/B switch setup... it shouldn't be that hard to do. I'd skip trying to make a system that's "redundant" in that it automatically fails over if there's a problem - keep it simple, like typical magneto setups on aircraft, where the operator switches from primary to backup if there is a problem - and this can be a nice, redundant, safe setup.
I helped build a Coot Amphibian about 10 years ago... N89VA. Also restored a 1947 Luscombe 8F and put about 100 hours on it before selling it on a near-worthless college education!
Keep us updated.
-scott
01-19-2005, 03:17 PM
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I agree about the redundancy. I don't feel the need for auto change over and will use a switch, same as the fuel pumps. I'm an OLD pilot used to OLD airplanes, although I have flown some pretty up to date stuff I'm prejudiced in favor of "simple". A lot of the automation and magic ends up being a detriment, since if it doesn't work for some reason, you then not only have to fix the problem the automation failed to fix, you have to figure out how to bypass the automation. A two position switch is fine for me, thanks.
The dual spark plug isn't IMHO necessary. If a plug, wire, or coil failure occurs, 7 others are still out there plugging (no pun intended, but there it is anyway) away. I don't plan to fly at night or in weather, I get plenty of that on the job. In that case, the other 7 should get to the nearest airport. Basically, a limp home is fine.
Olen
The dual spark plug isn't IMHO necessary. If a plug, wire, or coil failure occurs, 7 others are still out there plugging (no pun intended, but there it is anyway) away. I don't plan to fly at night or in weather, I get plenty of that on the job. In that case, the other 7 should get to the nearest airport. Basically, a limp home is fine.
Olen
Originally Posted by dieselgeek
Not maybe, but definitely. THe Speed Density algorithm in Megasquirt already compensates, on teh fly, for differences in density altitude: the MAP pressure changes for a given volume of airmass based on the oxygen density... in other words, the lower MAP reading at higher altitude will compensate for less oxygen to burn.
There IS a small concern because at higher altitude, BACKPRESSURE goes down, therefore Volumetric Efficiency goes up, and you actually need to RICHEN the mixture a little to compensate for this. There's a built in "7.7%-per-5000 foot difference in elevation based on MAP" - those numbers are derived from NASA and are also in all the OEM manufacturer's ECMs, however that might be off by a fraction of a percent at higher altitudes. If you want absolute correction, you can install a "MegaBaro" circuit for on the fly barometric measurements - OR the easier way is to figure out how an O2 sensor can be made to work.
I know at the dyno shop they use an O2 sensor (wideband) only a few inches up the tailpipe, farther from the combustion source than in your aircraft, and no closer to "open air" than in your proposed stack design: I think you can calibrate a wideband to make it work for EGO correction, and set it to a reasonbale limit like no more than 15% fuel added or taken away.
There's no question a MS would run your aircraft engine flawlessly. What I would suggest worrying about is setting up an inexpensive, redundant Megasquirt unit as a backup. You won't be able to do a dual ignition setup unless you figure out how to get two separate sparkplugs in the heads for each cylinder, but you could do dual EDIS modules, dual megasquirts, and dual ECT/MAT/MAP sensor setups using a simple A/B switch setup... it shouldn't be that hard to do. I'd skip trying to make a system that's "redundant" in that it automatically fails over if there's a problem - keep it simple, like typical magneto setups on aircraft, where the operator switches from primary to backup if there is a problem - and this can be a nice, redundant, safe setup.
I helped build a Coot Amphibian about 10 years ago... N89VA. Also restored a 1947 Luscombe 8F and put about 100 hours on it before selling it on a near-worthless college education!
Keep us updated.
-scott
There IS a small concern because at higher altitude, BACKPRESSURE goes down, therefore Volumetric Efficiency goes up, and you actually need to RICHEN the mixture a little to compensate for this. There's a built in "7.7%-per-5000 foot difference in elevation based on MAP" - those numbers are derived from NASA and are also in all the OEM manufacturer's ECMs, however that might be off by a fraction of a percent at higher altitudes. If you want absolute correction, you can install a "MegaBaro" circuit for on the fly barometric measurements - OR the easier way is to figure out how an O2 sensor can be made to work.
I know at the dyno shop they use an O2 sensor (wideband) only a few inches up the tailpipe, farther from the combustion source than in your aircraft, and no closer to "open air" than in your proposed stack design: I think you can calibrate a wideband to make it work for EGO correction, and set it to a reasonbale limit like no more than 15% fuel added or taken away.
There's no question a MS would run your aircraft engine flawlessly. What I would suggest worrying about is setting up an inexpensive, redundant Megasquirt unit as a backup. You won't be able to do a dual ignition setup unless you figure out how to get two separate sparkplugs in the heads for each cylinder, but you could do dual EDIS modules, dual megasquirts, and dual ECT/MAT/MAP sensor setups using a simple A/B switch setup... it shouldn't be that hard to do. I'd skip trying to make a system that's "redundant" in that it automatically fails over if there's a problem - keep it simple, like typical magneto setups on aircraft, where the operator switches from primary to backup if there is a problem - and this can be a nice, redundant, safe setup.
I helped build a Coot Amphibian about 10 years ago... N89VA. Also restored a 1947 Luscombe 8F and put about 100 hours on it before selling it on a near-worthless college education!
Keep us updated.
-scott
01-19-2005, 03:22 PM
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Originally Posted by dieselgeek
Not maybe, but definitely. THe Speed Density algorithm in Megasquirt already compensates, on teh fly, for differences in density altitude: the MAP pressure changes for a given volume of airmass based on the oxygen density... in other words, the lower MAP reading at higher altitude will compensate for less oxygen to burn.
There IS a small concern because at higher altitude, BACKPRESSURE goes down, therefore Volumetric Efficiency goes up, and you actually need to RICHEN the mixture a little to compensate for this. There's a built in "7.7%-per-5000 foot difference in elevation based on MAP" - those numbers are derived from NASA and are also in all the OEM manufacturer's ECMs, however that might be off by a fraction of a percent at higher altitudes. If you want absolute correction, you can install a "MegaBaro" circuit for on the fly barometric measurements - OR the easier way is to figure out how an O2 sensor can be made to work.
I know at the dyno shop they use an O2 sensor (wideband) only a few inches up the tailpipe, farther from the combustion source than in your aircraft, and no closer to "open air" than in your proposed stack design: I think you can calibrate a wideband to make it work for EGO correction, and set it to a reasonbale limit like no more than 15% fuel added or taken away.
There's no question a MS would run your aircraft engine flawlessly. What I would suggest worrying about is setting up an inexpensive, redundant Megasquirt unit as a backup. You won't be able to do a dual ignition setup unless you figure out how to get two separate sparkplugs in the heads for each cylinder, but you could do dual EDIS modules, dual megasquirts, and dual ECT/MAT/MAP sensor setups using a simple A/B switch setup... it shouldn't be that hard to do. I'd skip trying to make a system that's "redundant" in that it automatically fails over if there's a problem - keep it simple, like typical magneto setups on aircraft, where the operator switches from primary to backup if there is a problem - and this can be a nice, redundant, safe setup.
I helped build a Coot Amphibian about 10 years ago... N89VA. Also restored a 1947 Luscombe 8F and put about 100 hours on it before selling it on a near-worthless college education!
Keep us updated.
-scott
There IS a small concern because at higher altitude, BACKPRESSURE goes down, therefore Volumetric Efficiency goes up, and you actually need to RICHEN the mixture a little to compensate for this. There's a built in "7.7%-per-5000 foot difference in elevation based on MAP" - those numbers are derived from NASA and are also in all the OEM manufacturer's ECMs, however that might be off by a fraction of a percent at higher altitudes. If you want absolute correction, you can install a "MegaBaro" circuit for on the fly barometric measurements - OR the easier way is to figure out how an O2 sensor can be made to work.
I know at the dyno shop they use an O2 sensor (wideband) only a few inches up the tailpipe, farther from the combustion source than in your aircraft, and no closer to "open air" than in your proposed stack design: I think you can calibrate a wideband to make it work for EGO correction, and set it to a reasonbale limit like no more than 15% fuel added or taken away.
There's no question a MS would run your aircraft engine flawlessly. What I would suggest worrying about is setting up an inexpensive, redundant Megasquirt unit as a backup. You won't be able to do a dual ignition setup unless you figure out how to get two separate sparkplugs in the heads for each cylinder, but you could do dual EDIS modules, dual megasquirts, and dual ECT/MAT/MAP sensor setups using a simple A/B switch setup... it shouldn't be that hard to do. I'd skip trying to make a system that's "redundant" in that it automatically fails over if there's a problem - keep it simple, like typical magneto setups on aircraft, where the operator switches from primary to backup if there is a problem - and this can be a nice, redundant, safe setup.
I helped build a Coot Amphibian about 10 years ago... N89VA. Also restored a 1947 Luscombe 8F and put about 100 hours on it before selling it on a near-worthless college education!
Keep us updated.
-scott
I would call the manufacture of the O2 sensor to see how hot they can be run but I don't think that you will have too much of a problem with them being too close to the block. But as far as the wideban's being used within 10" of the tip's on a car exhaust, they normaly like to get them a lot further up the exhaust stream (like 24") and this is on an exhaust after a collector where there are several exhaust pulses run togeather to keep the air from getting back into the exhaust, this will be a lot worse with just 1 exhaust pulse in a single stack.
also I would be shure to get good match flowed injectors if you are going to have just 1 O2 in 1 cylinder, if you have too much varance between injectors you could run 1 cylinder too lean wile the O2 see's a good afr in its cylinder.
good luck with it but keep the parachute handy lol.
More Than Zero
02-14-2005, 04:47 PM
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Originally Posted by Project GatTagO
There is info here:
http://www.painlessperformance.com/perfect.asp
It basically uses the GM MEFI ECU. Its fine for a stock LS1, but the ECU can't easily be tuned if you make changes to the engine.
Andrew
http://www.painlessperformance.com/perfect.asp
It basically uses the GM MEFI ECU. Its fine for a stock LS1, but the ECU can't easily be tuned if you make changes to the engine.
Andrew
Adrian Murray, President
Painless Performance Products
02-14-2005, 05:03 PM
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Originally Posted by Speartech
Correct. The MAP sensor (Manifold Absolute Pressure) compensates for altitude at key on, and at some various throttle transitions.
I think retaining the O2 sensors would still be nice in order to make sure the tune in the ECU is correct (or at least close) by monitoring how much fuel is being added/subtracted; at least until you know it's all mapped out correctly.
BTW, MEFI is simply Marine Electronic Fuel Injection. As it has been revised over the years it has been called MEFI 2, MEFI 3, MEFI 4. It's kind of a simplified engine only controller that's good for things like boats that don't have much complexity or requirements. Basically idling, full throttle, a little cruising.
I think retaining the O2 sensors would still be nice in order to make sure the tune in the ECU is correct (or at least close) by monitoring how much fuel is being added/subtracted; at least until you know it's all mapped out correctly.
BTW, MEFI is simply Marine Electronic Fuel Injection. As it has been revised over the years it has been called MEFI 2, MEFI 3, MEFI 4. It's kind of a simplified engine only controller that's good for things like boats that don't have much complexity or requirements. Basically idling, full throttle, a little cruising.
If you have questions, contact us. We'll give you straight answers.
Adrian Murray, President
Painless Performance Products
1-888-350-6588, ext 1019
02-14-2005, 07:43 PM
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02-15-2005, 10:37 AM
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Thank you, Andrew. I should point out that your original post was correct based upon what was publicly known about the MEFI computer at the time. What you will see when the product is released bears a physical resemblance to the Delco MEFI but the programming is ours. We are currently setting the parameters for what can be user-programmed and hope to release software this summer. We are considering making the software a free download so that users can reprogram their ECM without incurring added expense. We think this will add to the appeal of the product.
Adrian Murray, President
Painless Performance Products
Adrian Murray, President
Painless Performance Products
