homemade electronic map limiter.... anyone else using one?
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Re: homemade electronic map limiter.... anyone else using one? (schwett)
well, it works without the op-amp. given that the map circuit in the ecu is high impedance, that should be fine, according to the designer. obviously it's a LOT simpler without the op-amp.
however, i decided to try another circuit, which i like because it passes the map signal out totally unmolested when below the cut-off. here's the schematic :
and my implementation of it :
yes, there's another half to the little case. doesn't look like much with it on.
it has a tiny hole in the side for acces to the set screw on the pot. it's a 15 turn pot, so you can very precisely set the output voltage.
problem is......... IT DOESN'T WORK, and i can't figure out the problem. the voltage regulator is outputting 5v. the pot is outputting 2.85v. 2.85v is present at one side of the relay, but no matter what i do it seems to output the original map signal. the relay clicks as soon as i energize the circuit with the 12v supply to the regulator.
any suggestions? the problem is obviousyl not with the pot or the vrm. the op-amp is an nte 975, the relay is a 5volt radio shack piece labeled "SPDT micromini 5VDC Relay" p/n 275-240A. the transistor is also radio shack, MPS3904 "NPN Silicon Transistor." i am not really sure what voltages to look for where, but i'd guess the problem is the op-amp. what the hell is it supposed to do, anyway!?!?
however, i decided to try another circuit, which i like because it passes the map signal out totally unmolested when below the cut-off. here's the schematic :
and my implementation of it :
yes, there's another half to the little case. doesn't look like much with it on.
it has a tiny hole in the side for acces to the set screw on the pot. it's a 15 turn pot, so you can very precisely set the output voltage.problem is......... IT DOESN'T WORK, and i can't figure out the problem. the voltage regulator is outputting 5v. the pot is outputting 2.85v. 2.85v is present at one side of the relay, but no matter what i do it seems to output the original map signal. the relay clicks as soon as i energize the circuit with the 12v supply to the regulator.
any suggestions? the problem is obviousyl not with the pot or the vrm. the op-amp is an nte 975, the relay is a 5volt radio shack piece labeled "SPDT micromini 5VDC Relay" p/n 275-240A. the transistor is also radio shack, MPS3904 "NPN Silicon Transistor." i am not really sure what voltages to look for where, but i'd guess the problem is the op-amp. what the hell is it supposed to do, anyway!?!?
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:shrug:
well, i didn't like the fact that the other one presented a small voltage drop at all times. there was also a lot of talk about whether or not it was "good design," which i don't really understand.... it seemed safer to me to have a circuit that was doing nothing almost all the time, and then simply supplying a regulated signal in boost. unfortunately i can't figure out why the second one doesn't work.
beautiful work....but if the other one worked fine...why?
again...really good work
again...really good work
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Re: strange results! (00SilverLS)
DOH, didn't notice there was a second page of posts...
anyway, I am planning on wiring up some pots to the MAP in order to run some larger injectors ala. "Bigger Squirts" on autospeed.com. Maybe there's a way to combine both of these, unless this serves the same purpose...
[Modified by ion_four, 7:35 AM 6/3/2002]
anyway, I am planning on wiring up some pots to the MAP in order to run some larger injectors ala. "Bigger Squirts" on autospeed.com. Maybe there's a way to combine both of these, unless this serves the same purpose...
[Modified by ion_four, 7:35 AM 6/3/2002]
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Re: homemade electronic map limiter.... anyone else using one? (schwett)
ok, i'm done for now. i went back to the simpler one, made even simpler by getting rid of the misbehaving op-amp.
like the other, it is adjustable via the little tiny screw on that 15 turn pot, which you can get to through that tiny hole in the front of the case. the entire adjustment range seems to be from around 2.5 to 3.2v, (?) so it is possible to achieve a very particular output voltage. i have it set to 2.85v for now.
it handled every high voltage feed i gave it very nicely. after setting it, 3.10v from two aa batteries came back 2.85v. 7.82v from a Li Ion camera battery came back 2.85v. 3.15v from 2 D batteries came back 2.85v. 12v from a wall wart came back 2.85v (only tested that for a second.)
with lower voltages, there is a small voltage drop. i haven't gone to the trouble of figuring it out, but it seems to vary a bit. 1.214v from a single nimh aa came out 1.212v. 1.546v from a normal aa came back 1.542v. 2.794v from the two together came back 2.762v. 1.579v from a different aa came back 1.574. those are all very acceptable, and the result wouldn't even be noticeable or measurable in terms of fueling. however, one particular battery showeda a large from from 1.213v to 1.092v. that's still relatively small (<10%) but it is more than one woud like. since a voltage that low would only be present in closed loop operation, it doesn't worry me at all.
the components are very very cheap :
100 ohm 1/4w resistor
100k ohm 1/4w resistor
20k ohm 15 turn cermet pot
tl431 adjustable shunt regulator (nte999 is what i used)
radio shack mini project case
some wire
all in all, less than $10 and closer to $5. i don't have a running car to test this in, but when i do, i'll let everyone know if it works. i plan to mount it in the engine bay where it's easy to get to, just after the map sensor.
[Modified by schwett, 1:48 AM 6/4/2002]
like the other, it is adjustable via the little tiny screw on that 15 turn pot, which you can get to through that tiny hole in the front of the case. the entire adjustment range seems to be from around 2.5 to 3.2v, (?) so it is possible to achieve a very particular output voltage. i have it set to 2.85v for now.
it handled every high voltage feed i gave it very nicely. after setting it, 3.10v from two aa batteries came back 2.85v. 7.82v from a Li Ion camera battery came back 2.85v. 3.15v from 2 D batteries came back 2.85v. 12v from a wall wart came back 2.85v (only tested that for a second.)
with lower voltages, there is a small voltage drop. i haven't gone to the trouble of figuring it out, but it seems to vary a bit. 1.214v from a single nimh aa came out 1.212v. 1.546v from a normal aa came back 1.542v. 2.794v from the two together came back 2.762v. 1.579v from a different aa came back 1.574. those are all very acceptable, and the result wouldn't even be noticeable or measurable in terms of fueling. however, one particular battery showeda a large from from 1.213v to 1.092v. that's still relatively small (<10%) but it is more than one woud like. since a voltage that low would only be present in closed loop operation, it doesn't worry me at all.
the components are very very cheap :
100 ohm 1/4w resistor
100k ohm 1/4w resistor
20k ohm 15 turn cermet pot
tl431 adjustable shunt regulator (nte999 is what i used)
radio shack mini project case
some wire
all in all, less than $10 and closer to $5. i don't have a running car to test this in, but when i do, i'll let everyone know if it works. i plan to mount it in the engine bay where it's easy to get to, just after the map sensor.
[Modified by schwett, 1:48 AM 6/4/2002]
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Re: homemade electronic map limiter.... anyone else using one? (falconGSR)
lol. if you want that, you're going to have to make one yourself and check it out. the parts cost less than $5 without the case.
however, i'm sure you could find out what's going on above the load limit simply by checking out the specs on the regulator!
however, i'm sure you could find out what's going on above the load limit simply by checking out the specs on the regulator!
oscilloscope traces?
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Re: homemade electronic map limiter.... anyone else using one? (schwett)
Still waiting on the schematics of the final product
Thanks for sharing!
One question, though...there was a project on autospeed.com with a similar goal in which they just had pots on the output and ground of the MAP, I believe...this was to run bigger injectors, more so than block the ECM from seeing boost...will your mod allow bigger injectors to idle, or is it just to serve the purpose of a missing-link/ check valves and still require an fmu or similar?
Thanks for sharing!
One question, though...there was a project on autospeed.com with a similar goal in which they just had pots on the output and ground of the MAP, I believe...this was to run bigger injectors, more so than block the ECM from seeing boost...will your mod allow bigger injectors to idle, or is it just to serve the purpose of a missing-link/ check valves and still require an fmu or similar?
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Re: homemade electronic map limiter.... anyone else using one? (ion_four)
yep, it's basically an electronic missing link.
the schematic is up there, first page, just take off the op-amp!
[Modified by schwett, 3:28 PM 6/7/2002]
the schematic is up there, first page, just take off the op-amp!
[Modified by schwett, 3:28 PM 6/7/2002]
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Re: homemade electronic map limiter.... anyone else using one? (schwett)
So, what do you think about the idea of merely hooking up some resistors to the MAP sensor to limit the signal, across the board? This (and possibly your circuit) would seem to be necessary in order to run larger (450cc) injectors. Your circuit is more for FMU, correct?
http://www.autospeed.com/A_0008/page1.html
Their approach seems more suited toward modifying a car without changing the status of it's induction, ie. souping up a turbo, or NA, but not adding a turbo to an NA, since it not only amplifies the power curve, but completely changes it at the point of turbo spool-up...
I'd think that a version of your circuit and just the pots would be a good combo to achieve this. or would yours be redundant? Or would this just suck (if so, explain)?
I may be making a trip to the shack later tonight...
http://www.autospeed.com/A_0008/page1.html
Their approach seems more suited toward modifying a car without changing the status of it's induction, ie. souping up a turbo, or NA, but not adding a turbo to an NA, since it not only amplifies the power curve, but completely changes it at the point of turbo spool-up...
I'd think that a version of your circuit and just the pots would be a good combo to achieve this. or would yours be redundant? Or would this just suck (if so, explain)?
I may be making a trip to the shack later tonight...
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Re: homemade electronic map limiter.... anyone else using one? (schwett)
i checked the link site... didn't see it... but i do see it on the one in your sig. what does it look like? $70 isn't too bad i guess. same as a missing link.
the one i made cost about $5-10 though, but i have yet to see if it works. here's the schematic, but nobody go build one until i can test it! it would be a bummer if 4 or 5 of us built the same non-working voltage clamp. heh.
notes from the designer : The op amp is set up so the output follows the input 1:1. R1 and R2 set the reference of the TL431 so that when + input on the op amp reaches 2.8V, the TL431 will start to conduct and limit the voltage to 2.8V. R3 drops the voltage when the TL431 is conducting, otherwise R3 would drop a maximum of 9 microvolts. Also, if the input in the ECU is high impedence, you probably wouldn't even need the op amp in the circuit I drew. I really doubt the op amp is even needed.
If the input inpedence of the ECU were not high enough, you would have voltage drop on R3 even when the TL431 is not conducting. That would mean the ECU would always see slightly less voltage than what the MAP is sending.
Also, replacing R1 with a 20K pot would make this circuit adjustable.
click on the "link engine management" link in my signature, its somewhere there on the site.. probably under accessories or options.
[Modified by schwett, 10:06 AM 5/21/2002]
the one i made cost about $5-10 though, but i have yet to see if it works. here's the schematic, but nobody go build one until i can test it! it would be a bummer if 4 or 5 of us built the same non-working voltage clamp. heh.
notes from the designer : The op amp is set up so the output follows the input 1:1. R1 and R2 set the reference of the TL431 so that when + input on the op amp reaches 2.8V, the TL431 will start to conduct and limit the voltage to 2.8V. R3 drops the voltage when the TL431 is conducting, otherwise R3 would drop a maximum of 9 microvolts. Also, if the input in the ECU is high impedence, you probably wouldn't even need the op amp in the circuit I drew. I really doubt the op amp is even needed.
If the input inpedence of the ECU were not high enough, you would have voltage drop on R3 even when the TL431 is not conducting. That would mean the ECU would always see slightly less voltage than what the MAP is sending.
Also, replacing R1 with a 20K pot would make this circuit adjustable.
click on the "link engine management" link in my signature, its somewhere there on the site.. probably under accessories or options.
[Modified by schwett, 10:06 AM 5/21/2002]
Is it doing the same thing as this?
[Modified by ion_four, 12:28 AM 6/8/2002]
[Modified by ion_four, 12:29 AM 6/8/2002]
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Re: homemade electronic map limiter.... anyone else using one? (Sonny)
So, whats the point of this thing? What does it do? Sorry I'm dumb. 
If the MAP sensor "sees" boost, it will cause the ECU to throw a code. The map limiter circuit allows the sensor to see boost, but it will clamp the voltage going to the ECU so that a code will not be thrown. Adjusting the max voltage seen by the ECU from the MAP sensor is also a way of controlling injector duty cycle at WOT.
Sonny
If the MAP sensor "sees" boost, it will cause the ECU to throw a code. The map limiter circuit allows the sensor to see boost, but it will clamp the voltage going to the ECU so that a code will not be thrown. Adjusting the max voltage seen by the ECU from the MAP sensor is also a way of controlling injector duty cycle at WOT.
Sonny
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Re: strange results! (Jordo)
it prevents the ECU from seeing boost. the stock map sensor normally should never output more than 2.8 volts or so, because that's what it outputs at normal atmospheric pressure (will vary with elevation, weather...)
when you throw a turbo or SC on, you generate positive pressure and the map sensor sends a 4v or 3.5v or whatever signal to the ECU. the ECU does not like this, throws a code, and the car bogs and gets pissy.
the j&s safeguard has a built in map limiter, as do the piggyback electronics included with a jrsc for some cars. some people also use a mechanical check valve to bleed off the boost pressure before the map sensor, and some people use a missing link which is similar in principle (i.e. it's a mechanical device) but doesn't work quite the same way.
so to summarize, yes, it works in theory and on the bench, it was cheap, and to make one you follow the schematic above but remove the op-amp (triangular symbol with 5 leads.) you no longer need the 12v, and the input into the ecu is the one that was coming into the op-amp from the left.
when you throw a turbo or SC on, you generate positive pressure and the map sensor sends a 4v or 3.5v or whatever signal to the ECU. the ECU does not like this, throws a code, and the car bogs and gets pissy.
the j&s safeguard has a built in map limiter, as do the piggyback electronics included with a jrsc for some cars. some people also use a mechanical check valve to bleed off the boost pressure before the map sensor, and some people use a missing link which is similar in principle (i.e. it's a mechanical device) but doesn't work quite the same way.
so to summarize, yes, it works in theory and on the bench, it was cheap, and to make one you follow the schematic above but remove the op-amp (triangular symbol with 5 leads.) you no longer need the 12v, and the input into the ecu is the one that was coming into the op-amp from the left.
im a noob,what exactly does it do?
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Re: strange results! (schwett)
Right on!...
So, this circuit only hides the boost from the MAP? It won't do anything for running larger injectors, like the little schematic I put up, from autospeed.com, above?
The tl431 is a Voltage Regulator for 2.8v? I went to radio shack (and aside from being completely ignorant of all electronic components) they said they'd have to order it...
My new goal is to make my own fuel management as well as gauges (atleast A/F), and possibly EGT. I know a little about electronics, but not alot.
So, this circuit only hides the boost from the MAP? It won't do anything for running larger injectors, like the little schematic I put up, from autospeed.com, above?
The tl431 is a Voltage Regulator for 2.8v? I went to radio shack (and aside from being completely ignorant of all electronic components) they said they'd have to order it...
My new goal is to make my own fuel management as well as gauges (atleast A/F), and possibly EGT. I know a little about electronics, but not alot.