Megasquirt Help.
05-16-05, 10:26 PM
#1
Megasquirt Help.
Well, its gotten to the point where i need to turn the key and cross my finger. but i have one problem. fuel. seeing ad though we dont have pistons it kinda fubars my plans. now this is what i have considered.
to just fire it up straight from the box. i mean simply that. install the last component, button it all up, test with mega stimulator, see if it wworks, and toss it in there and prey.
now people have told me that this will, and iwll not work. i get mixed results. i need hard facts.
i went here
http://www.megasquirt.info/manual/rotary.htm
and have read up on this. most of the info i need was down near the bottom. what i want to do is get a basemap that runs the fuel well, with a 100% stock unmodified s4 6port engine. they have some file on there but i dont want to download that as they dont provide too many details about that file. or they do but im too stupid to see it.
also i found a text document online. heres the context of the document.
MegaSquirt modifications for rotary engines V0.0.1
1.Intro
This document lists the analysis that I have done to see how the MegaSquirt could be applied to Mazda twin rotor engines and if it is feasible to modify the HW and SW for a staged sequential injection system
2.MegaSquirt introduction
The MegaSquirt was design by Bruce Bowling and Al Grippo to be a simple and cheap batch fire fuel injection system. Blah
There are 2 injector driver outputs on the MegaSquirt, running off the PWM channels of the MCU. This allows both saturated and peak and hold injectors to be used on the same hardware: very clever. This allows 2 different injection events to occur in parallel, which suits our purposes very nicely.
3.Specific needs of Rotary engines
The rotary engine, due to the rotor layout has a few key differences wrt a reciprocating engine. Many of these work in our favour. And remember, the otto cycle is the otto cycle:
There are 2 rotors, spaced 180° apart. If you have 3 then you should already have EFI. The ignition pulse on 1 rotor corresponds to 20° BTDC on the inlet cycle of the other rotor, give or take the amount of advance being used. Very handy.
Around 220-280° is available for injection with non-bridge ported schemes. In a reciprocating engine, you can ‘puddle’ fuel on the inlet port to increase the injection time. In a rotary there is little time for this before the next inlet cycle starts. This forces relatively large injectors to be used, with staged injection being a useful method of getting high max flow rates and a good dynamic range. For example, at 8000 RPM 1 revolution is 7.5ms, giving around 6ms for injection.
4.Using MegaSquirt ‘out the .box’
For a stock or street ported rotary the minimal exhaust overlap should not cause too much fuel to be lost out the exhaust, or reversion to be too much of an issue, so batch firing of the injectors is not an issue here. Bridge-ports see later on. In terms of injector strategies there are a couple in general use
A)2-in port injectors in a 6-port or turbo centre plate
B)4 injectors one in each runner
C)2 injectors in the throttle bodies
D)4 injectors in the throttle body
E)2 injectors in the throttle body and 2 remote firing at the butterfly
All of these have various pros and cons, usually related to your welding skills or available cash. In terms of fuel 2 750cc injectors is good for 160BHP in the stock 6-port. 2 880cc units have successfully managed 210BHP in a 12A at 8300RPM. Mat ‘Hitman’ has a lot of experience in NA and turbo apps and is worth contacting for advice, or visit his website. He pushes Haltech, which is fine. If I had the money I would buy a Haltech, but I don’t.
Anyway, if you decide that 2 injectors is the way for you life is easy. Hook both injectors to one of the outputs and set the MegaSquirt to single injector, 1 injection per ignition event. Hook the ignition sense to the leading coil negative terminal/MSD/whatever and move on to the next stage.
This arrangement will give 2 injections per revolution. One at around intake TDC for each rotor and one 180° later, which should even the fuelling out. It will limit you max injection time to around 3ms, or 6ms per revolution, for 8000RPM max.. You could run one injection per 2 ignition events, which certainly shouldn’t hurt in a TBI case, but I won’t vouch for it until I have tried it. Likewise this scheme could potentially give some idle problems due to a min injection time of 2ms per rotor. Suck it and see.
If you are unhappy with this then we move to stage 2
5.Stage 2 injector staging
To get good dynamic range of the injectors staging is often used. This way at low speed/throttle openings only one injector is running. At high RPMs a second one cuts in. This effectively doubles the dynamic range of the system, with the added benefit of being able to use smaller and cheaper injectors.
The simplest form of injector staging is to have 2 equal size injectors. When pulsewidth becomes greater than (say) 3ms then divide pulsewidth by 2 and enable secondaries, with a tad of hysterisis to prevent hunting. Another option is drive staging via RPM and modify the VE table to balance out.
The simple approach does suffer from a reduced dynamic range compared to other methods. The preferred rule of thumb is to have a 1/3 to 2/3 split between primaries and secondaries. This leads to a potential scaling problem.
For example, if at 6000RPM, the max PW is set to 5.5ms and you are at that at part throttle. If you then open the throttle gently, the SW will see that the PW is now, say, 6ms. It will divide this by 3, giving 2ms, which is short enough that potentially there will be an underfuelling with saturated injectors. A solution to this is to take RPM which is represented as RPM/100 in memory (i.e. 60=6000RPM), convert to RPM/1000 (call this KRPM). Then max PW =36/KRPM, where 36 is a constant based upon the desired maximum duration of injection. This is fairly coarse, but should ensure that you don’t stumble too much and any imperfections could be sorted out by mapping carefully.
A third method is to use the primaries only for cruise or steady state work and the secondaries for power enrichment. This is certainly and interesting way to go, especially for turbo installations, but not one I will be following.
There are a myriad of other possibilities but these are the ones I have considered as ‘doable’ in MegaSquirt. The order in which I will do them is still open, but I am warming to the RPM based solution as potentially giving the best balance.
Stage 4:2 MegaSquirt sequential
So you want full sequential injection because it sounds good? OK, here is the easy way
Build 2 MegaSquirts
Epoxy a magnet to the crank flywheel at TDC.
Fit a pair of hall effect sensors one at TDC, one 180° later (top and bottom)
Hook one MegaSquirt to the top sensor and one to the bottom.
Burn in injector staging code if required.
Pros: The code mods are very simple, if needed at all
You get the full 6 ms for injection at high RPM
Cons: 2 MegaSquirts are needed so adding a full $100 to the costs
Tuning will be a little more tricky as you have to set each parameter twice
If this sounds too much like money then there is another way
For full sequential operation the additional mods are:
Additional interrupt line to select between rotors.
Additional timing loop in SW to handle sequential operation, as considerable overlap will occur
The additional interrupt is fed from the crank flywheel again, with a magnet at say 50°BTDC and a matching pickup. This would tell the MegaSquirt that you are about to inject rotor 1 on the next ignition pulse. You would connect the pickup to a spare input line and OR it into the IRQ.
If you want staged and Sequential you need an extra pair of injector drivers. These would be connected to the PWM outputs through an AND gate which is driven by a spare output to engage secondaries.
6.Bridge-ports and timing injector opening
I gave this much thought and have decided that, until someone will supply with a cheap bridge-port to play with I don’t have time to worry about the code mods. When one appears, I’ll code for it.
7.Code modifications
To follow once I’ve worked them out.
now dont complain about my spelling because i didnt write this.
all i want to know or if something is available, i want a simple base map, thats soo uuber simple, that i can get it to run my car and not even have to worry about because it is good enough to run my car just fine. weather i beat obn it a il bit or just want to go from oint a to point b. no tunig really necessary if i just want a simple daily driver, no other tuning required to get it 100% perfect. sice this is a daily driver i need to simply get to school and back and maybe to work and back and ill be fine.
i need help.
to just fire it up straight from the box. i mean simply that. install the last component, button it all up, test with mega stimulator, see if it wworks, and toss it in there and prey.
now people have told me that this will, and iwll not work. i get mixed results. i need hard facts.
i went here
http://www.megasquirt.info/manual/rotary.htm
and have read up on this. most of the info i need was down near the bottom. what i want to do is get a basemap that runs the fuel well, with a 100% stock unmodified s4 6port engine. they have some file on there but i dont want to download that as they dont provide too many details about that file. or they do but im too stupid to see it.
also i found a text document online. heres the context of the document.
MegaSquirt modifications for rotary engines V0.0.1
1.Intro
This document lists the analysis that I have done to see how the MegaSquirt could be applied to Mazda twin rotor engines and if it is feasible to modify the HW and SW for a staged sequential injection system
2.MegaSquirt introduction
The MegaSquirt was design by Bruce Bowling and Al Grippo to be a simple and cheap batch fire fuel injection system. Blah
There are 2 injector driver outputs on the MegaSquirt, running off the PWM channels of the MCU. This allows both saturated and peak and hold injectors to be used on the same hardware: very clever. This allows 2 different injection events to occur in parallel, which suits our purposes very nicely.
3.Specific needs of Rotary engines
The rotary engine, due to the rotor layout has a few key differences wrt a reciprocating engine. Many of these work in our favour. And remember, the otto cycle is the otto cycle:
There are 2 rotors, spaced 180° apart. If you have 3 then you should already have EFI. The ignition pulse on 1 rotor corresponds to 20° BTDC on the inlet cycle of the other rotor, give or take the amount of advance being used. Very handy.
Around 220-280° is available for injection with non-bridge ported schemes. In a reciprocating engine, you can ‘puddle’ fuel on the inlet port to increase the injection time. In a rotary there is little time for this before the next inlet cycle starts. This forces relatively large injectors to be used, with staged injection being a useful method of getting high max flow rates and a good dynamic range. For example, at 8000 RPM 1 revolution is 7.5ms, giving around 6ms for injection.
4.Using MegaSquirt ‘out the .box’
For a stock or street ported rotary the minimal exhaust overlap should not cause too much fuel to be lost out the exhaust, or reversion to be too much of an issue, so batch firing of the injectors is not an issue here. Bridge-ports see later on. In terms of injector strategies there are a couple in general use
A)2-in port injectors in a 6-port or turbo centre plate
B)4 injectors one in each runner
C)2 injectors in the throttle bodies
D)4 injectors in the throttle body
E)2 injectors in the throttle body and 2 remote firing at the butterfly
All of these have various pros and cons, usually related to your welding skills or available cash. In terms of fuel 2 750cc injectors is good for 160BHP in the stock 6-port. 2 880cc units have successfully managed 210BHP in a 12A at 8300RPM. Mat ‘Hitman’ has a lot of experience in NA and turbo apps and is worth contacting for advice, or visit his website. He pushes Haltech, which is fine. If I had the money I would buy a Haltech, but I don’t.
Anyway, if you decide that 2 injectors is the way for you life is easy. Hook both injectors to one of the outputs and set the MegaSquirt to single injector, 1 injection per ignition event. Hook the ignition sense to the leading coil negative terminal/MSD/whatever and move on to the next stage.
This arrangement will give 2 injections per revolution. One at around intake TDC for each rotor and one 180° later, which should even the fuelling out. It will limit you max injection time to around 3ms, or 6ms per revolution, for 8000RPM max.. You could run one injection per 2 ignition events, which certainly shouldn’t hurt in a TBI case, but I won’t vouch for it until I have tried it. Likewise this scheme could potentially give some idle problems due to a min injection time of 2ms per rotor. Suck it and see.
If you are unhappy with this then we move to stage 2
5.Stage 2 injector staging
To get good dynamic range of the injectors staging is often used. This way at low speed/throttle openings only one injector is running. At high RPMs a second one cuts in. This effectively doubles the dynamic range of the system, with the added benefit of being able to use smaller and cheaper injectors.
The simplest form of injector staging is to have 2 equal size injectors. When pulsewidth becomes greater than (say) 3ms then divide pulsewidth by 2 and enable secondaries, with a tad of hysterisis to prevent hunting. Another option is drive staging via RPM and modify the VE table to balance out.
The simple approach does suffer from a reduced dynamic range compared to other methods. The preferred rule of thumb is to have a 1/3 to 2/3 split between primaries and secondaries. This leads to a potential scaling problem.
For example, if at 6000RPM, the max PW is set to 5.5ms and you are at that at part throttle. If you then open the throttle gently, the SW will see that the PW is now, say, 6ms. It will divide this by 3, giving 2ms, which is short enough that potentially there will be an underfuelling with saturated injectors. A solution to this is to take RPM which is represented as RPM/100 in memory (i.e. 60=6000RPM), convert to RPM/1000 (call this KRPM). Then max PW =36/KRPM, where 36 is a constant based upon the desired maximum duration of injection. This is fairly coarse, but should ensure that you don’t stumble too much and any imperfections could be sorted out by mapping carefully.
A third method is to use the primaries only for cruise or steady state work and the secondaries for power enrichment. This is certainly and interesting way to go, especially for turbo installations, but not one I will be following.
There are a myriad of other possibilities but these are the ones I have considered as ‘doable’ in MegaSquirt. The order in which I will do them is still open, but I am warming to the RPM based solution as potentially giving the best balance.
Stage 4:2 MegaSquirt sequential
So you want full sequential injection because it sounds good? OK, here is the easy way
Build 2 MegaSquirts
Epoxy a magnet to the crank flywheel at TDC.
Fit a pair of hall effect sensors one at TDC, one 180° later (top and bottom)
Hook one MegaSquirt to the top sensor and one to the bottom.
Burn in injector staging code if required.
Pros: The code mods are very simple, if needed at all
You get the full 6 ms for injection at high RPM
Cons: 2 MegaSquirts are needed so adding a full $100 to the costs
Tuning will be a little more tricky as you have to set each parameter twice
If this sounds too much like money then there is another way
For full sequential operation the additional mods are:
Additional interrupt line to select between rotors.
Additional timing loop in SW to handle sequential operation, as considerable overlap will occur
The additional interrupt is fed from the crank flywheel again, with a magnet at say 50°BTDC and a matching pickup. This would tell the MegaSquirt that you are about to inject rotor 1 on the next ignition pulse. You would connect the pickup to a spare input line and OR it into the IRQ.
If you want staged and Sequential you need an extra pair of injector drivers. These would be connected to the PWM outputs through an AND gate which is driven by a spare output to engage secondaries.
6.Bridge-ports and timing injector opening
I gave this much thought and have decided that, until someone will supply with a cheap bridge-port to play with I don’t have time to worry about the code mods. When one appears, I’ll code for it.
7.Code modifications
To follow once I’ve worked them out.
now dont complain about my spelling because i didnt write this.
all i want to know or if something is available, i want a simple base map, thats soo uuber simple, that i can get it to run my car and not even have to worry about because it is good enough to run my car just fine. weather i beat obn it a il bit or just want to go from oint a to point b. no tunig really necessary if i just want a simple daily driver, no other tuning required to get it 100% perfect. sice this is a daily driver i need to simply get to school and back and maybe to work and back and ill be fine.
i need help.
05-16-05, 10:44 PM
#2
Rx-hippie
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It comes with a standard base map to get the car running, you can use your narrow band and have a buddy in the pessanger drive and drive around in the hwy and city and have your buddy tune it. SHould take a few hours the get a nice smooth drivable map. The map it comes with will get you running.. but you will be running pig rich. What version of code are you using? Are you using Staged injection? Or what are you using to control primary and secondary?
05-17-05, 12:01 PM
#3
Eats, Sleeps, Dreams Rotary
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The only people here that I can remember who've done a Megasquirt install are Renns and Aaron Cake (non-rotary). Maybe you should try PMing them.
05-17-05, 05:44 PM
#4
It does not come with a standard base map. I have a very crude map that will at least get your car started. I suggest you set the constants up as a 2616 cc 4 cylinder engine. Even fire. For now just use only the 2 primary fuel injectors and worry about tuning up to 4000 rpm. You can plug the rest in later. Load it in as 2 injectors of 460 cc capacity. 2 squirts per revolution. the high impendance injectors need to be set up as 100% in the the MS constans and at 25.4 right underneath it. The low impedance injectors show up automatically at 75% so you need to change it. This alone will allow you to crank it over and get the car to start. Do not put your foot on the gas at all when cranking. this cuts fuel to the engine. Once it starts you will need to hold your foot on the gas throttling it constantly just to keep it going. Go into the VE1 table and edit in the real time map. What you will need to do is to look at where the green marker is and make changes there. This marker is always moving because it shows where the engine currently is at rpm and load. To keep the car running on it's own you will need to richen these areas up quite a bit. As you do you'll notice that you can slowly take your foot off the gas little by little to back the rpm's down. By the time you figure it out, the engine should be up to operating temperature and capable of idling on it's own. If it doesn't but it is at least smooth, adjust the throttle screw until it does and restart it. It isn't hard to get running decently. It is always too lean to begin with and in need of more fuel. Once you try to drive it you'll find it bucks wildly and doesn't want to move. It will be too lean. You need to watch the screen to see where the green marker is so you can richen it up. It'll take you a few minutes to figure out but it is actually quite easy. Once you get this far i can help you set up the staged injection and further tuning. Keep at it and if you have any questions just ask the msefi.com forum. I'm on there under the same name and several others are rotary people including the site mods.
Last edited by rotarygod; 05-17-05 at 05:47 PM.
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