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View Full Version : boost required to adjust mapclamp


evil_2
10-25-2019, 09:38 AM
how much boost is needed for me to get the initial setting on my mapclamp? i bought a dasmpar MC and the adjustment was turned by the person i bought it from.

punkrokdood
10-25-2019, 09:39 AM
huh????

evil_2
10-25-2019, 09:42 AM
to set the mapclamp you need to run a certain amout of boost with a boost leak tester and check it with a meter to get the base 4.6v or somewhere around there.... how much boost? is it the max psi the map sensor can read or is morethan that?

punkrokdood
10-25-2019, 09:46 AM
to set the mapclamp you need to run a certain amout of boost with a boost leak tester and check it with a meter to get the base 4.6v or somewhere around there.... how much boost? is it the max psi the map sensor can read or is morethan that?
why do you need to do that?

set the clamp to not clamp at all (i can't remember which way to turn the screw)

then slowly clamp it down while watching your A/F ratio during some WOT runs, or on the dyno till you get it where you want it...

i don't see any need for a baseline...

if there is a baseline, the i guess "stock" is a good one to go from

punkrokdood
10-25-2019, 09:48 AM
if you want to tune to a voltage then you can look at these tables
http://www.streetracingtechnology.com/forums/showthread.php?t=1098

evil_2
10-25-2019, 10:05 AM
why do you need to do that?

set the clamp to not clamp at all (i can't remember which way to turn the screw)

then slowly clamp it down while watching your A/F ratio during some WOT runs, or on the dyno till you get it where you want it...

i don't see any need for a baseline...

if there is a baseline, the i guess "stock" is a good one to go from

the thing with the dasmoapr MC is that there is no stopping point on the adjustment screw...it just turns, and doesnt click..the person i bought it from said they had turned it...so if i was to just install it and do an initial run i could be clamping too much and trash my motor..see what im saying?

evil_2
10-25-2019, 10:07 AM
if you want to tune to a voltage then you can look at these tables
http://www.streetracingtechnology.com/forums/showthread.php?t=1098


thanks for the link....once i get the base voltage down or heck even set it to a specific volts..im thinking 4.2v would be good....from there i could just adjust it with my wideband...i wish i would have bought one that hadnt been mesed with...

punkrokdood
10-25-2019, 10:16 AM
it doesn't sound right that it keeps turning... but i dunno, i've never messed with a map clamp, just know how they work. I'm not 100% sure that running a boost check on the car will cause the map sensor to give a readable voltage... you may need to put the key in the "on" (not start) position... i've never tried reading voltage from the MAP either :lol:

evil_2
10-25-2019, 10:20 AM
it doesn't sound right that it keeps turning... but i dunno, i've never messed with a map clamp, just know how they work. I'm not 100% sure that running a boost check on the car will cause the map sensor to give a readable voltage... you may need to put the key in the "on" (not start) position... i've never tried reading voltage from the MAP either :lol:


yeah, you are right..you do have to turn the key on..

punkrokdood
10-25-2019, 10:23 AM
yeah, you are right..you do have to turn the key on..
i ifigured at least that... just wasn't sure if it would read a voltage in the "on" position, or if the car had to actually be running to get a voltage reading

evil_2
10-25-2019, 10:23 AM
i ifigured at least that... just wasn't sure if it would read a voltage in the "on" position, or if the car had to actually be running to get a voltage reading

just the on position

gudeman00
10-25-2019, 11:37 AM
So I know it's not too safe but if I run a voltmeter and check what it's at, technically, if that chart by funks is safe, I could tune the mapclamp to a certain setting and not use a wideband.

evil_2
10-25-2019, 11:50 AM
i would highly reccomend a wideband...i mean you could techncally set it per voltage but remember. you are overiding the saftey mechanism for boost in the pcm...and all cars are different as well..

as for my car...i have a wideband. in every gear my afr's are 10.0 in boost until right before redline...i know i can can lean it out.

punkrokdood
10-25-2019, 11:52 AM
So I know it's not too safe but if I run a voltmeter and check what it's at, technically, if that chart by funks is safe, I could tune the mapclamp to a certain setting and not use a wideband.
yea, you could... but you'd need to see how rich/lean you are. every car is gonna flow SLIGHTLY different even from the factory... then if you've added other bolt ons, that will change your flow, and how much fuel you need. it might be safe at 4.3 volts one day, then add an exhaust and throttlebody, and you might have to go to 4.8 volts, then add a return line, you might go down to 3.8 volts and still run a 10:1 A/F if your fuel pressure is high. if you tune VERY conservatively, you COULD tune it off the voltage alone, but i would say DO NOT DO IT! if your ONLY mods were intake, exhaust, wga, map clamp and s2 injectors, then MAYBE i'd say clamp around 4.5-4.8 volts, without checking A/F but i'd be scared :lol:

spools
10-25-2019, 04:27 PM
when i installed my mapclamp all i did was turn the car to the on position with the mapclamp installed, did a voltage test on the map sensor, and then adjusted the mapclamp till it was at like 4 volts or something... then i started my car and tested the A/F.. and adjusted the mapclamp from there... setting it to 4 volts put me in the range iw anted without being to dangerous... i think i was at like 12.4 or something on the first pull. so, i just adjusted down till i got a 11.5... been there ever since. hope that helps any.

evil_2
10-25-2019, 06:28 PM
so you didnt have to boost your car with a leak tester to do set it?

blackbird
10-26-2019, 01:33 PM
Map clamp. Truth that a ў50 part really can kill a $2k engine. :lol:

Yes, I'd get a wideband installed on the car if you're considering playing with one. While you can adjust them with a multimeter to get in a ballpark cut-off range you still need to know how the changes are affecting the car. The MAP sensor is very important on a speed density system, but the PCM still uses other sensors to determine fueling and timing.

Speaking of timing also pick up one of the scan gauges that can read knock in degrees to go along with the wideband and you'll be set for "tuning" with most basic modifications. I'd actually recommend for anyone currently stock that plans to modify their car to pick up all the gauges, scan tool/gauge, etc. first. That way you can see how the car is behaving stock and what the PCM does and then be able to take what you learn to keep it happy and safe when you start upgrading.

evil_2
10-26-2019, 03:06 PM
Map clamp. Truth that a ў50 part really can kill a $2k engine. :lol:

Yes, I'd get a wideband installed on the car if you're considering playing with one. While you can adjust them with a multimeter to get in a ballpark cut-off range you still need to know how the changes are affecting the car. The MAP sensor is very important on a speed density system, but the PCM still uses other sensors to determine fueling and timing.

Speaking of timing also pick up one of the scan gauges that can read knock in degrees to go along with the wideband and you'll be set for "tuning" with most basic modifications. I'd actually recommend for anyone currently stock that plans to modify their car to pick up all the gauges, scan tool/gauge, etc. first. That way you can see how the car is behaving stock and what the PCM does and then be able to take what you learn to keep it happy and safe when you start upgrading.


i have a wideband....i said that in one of my posts above..

im still looking for a definite answer...does my map sensor have to see boost in order to adjust the mapclamp? and if so, how much? my clamp was used and did not come with it factory pre-set...

once i get a decent base voltage down then i will tune it with my wideband

blackbird
10-27-2019, 01:05 PM
I think it's already been covered in a few posts now, but you can either adjust it to the max cutoff voltage of the Zener diode or the variation depending on components (which means adjust it so it isn't clamping/hiding any voltage from the PCM) and then adjust down slightly until you get the A/F you're looking for. Or if you want to adjust it prior you'll need a multimeter and can either read directly or manually apply 5V+ to the clamp and check the output or connect the MAP sensor up to a regulated, low-pressure boost source (i.e. compressor) and use a multimeter to measure the cutoff point.

Either way you're not going to know what exact voltage to set it to to start with, and you don't want to set it too low. So it would be best to start with it essentially turned off and work down to adjust A/F. I'd still check and make sure you aren't clamping it too much by measuring the voltage cutoff during and after you're tuning A/F, especially if you don't have a scan tool/gauge to monitor what's going on with timing and knock.

evil_2
10-27-2019, 01:11 PM
I think it's already been covered in a few posts now, but you can either adjust it to the max cutoff voltage of the Zener diode or the variation depending on components (which means adjust it so it isn't clamping/hiding any voltage from the PCM) and then adjust down slightly until you get the A/F you're looking for. Or if you want to adjust it prior you'll need a multimeter and can either read directly or manually apply 5V+ to the clamp and check the output or connect the MAP sensor up to a regulated, low-pressure boost source (i.e. compressor) and use a multimeter to measure the cutoff point.

Either way you're not going to know what exact voltage to set it to to start with, and you don't want to set it too low. So it would be best to start with it essentially turned off and work down to adjust A/F. I'd still check and make sure you aren't clamping it too much by measuring the voltage cutoff during and after you're tuning A/F, especially if you don't have a scan tool/gauge to monitor what's going on with timing and knock.

ok, so if i use a boost leak tester run 20psi into the car with the key on i should be able to set it or at least get it close right?

if i cant do that with tis mapclamp, im just goingto buy a brand new one that is pre-set at the lowest setting...i have no idea why the peron htat i boght it for turned the adjustment for no reason..

OTownSRT4
10-27-2019, 02:05 PM
Turn that thing a hundred turns to higher voltage, run the car WOT and turn it to lower voltage until you AFR's are were you want them. This is why i like the PTP clamp. Not that i really ever mess around with it, i just love the option to check the voltage at any time. Good luck

evil_2
10-27-2019, 03:09 PM
Turn that thing a hundred turns to higher voltage, run the car WOT and turn it to lower voltage until you AFR's are were you want them. This is why i like the PTP clamp. Not that i really ever mess around with it, i just love the option to check the voltage at any time. Good luck


now if i turn it to the right 100 times wont it eventually got back to the lean side?

OTownSRT4
10-27-2019, 03:31 PM
now if i turn it to the right 100 times wont it eventually got back to the lean side?

No, i can't remember how it was explained to me so "no" is the best answer i can give.

cookie32
10-27-2019, 03:38 PM
anyone know where to get a good boost leak tester?

evil_2
10-27-2019, 03:45 PM
anyone know where to get a good boost leak tester?


i make them...

evil_2
10-27-2019, 03:48 PM
No, i can't remember how it was explained to me so "no" is the best answer i can give.

ill mess with the mapclamp and turn it a "few" times....lol

i guees what ill do is hook it up and run it on the car and at WOT if it goes over 12.0 ill shut her down and re-adjust

blackbird
10-27-2019, 06:00 PM
Do you have a multimeter and/or do you know how to use one? There are a few different designs and ways to put them together, but a MAP clamp essentially is based around one or two Zener diodes (which is what 'limits' max voltage) and a potentiometer (variable resistor) that allows you to adjust and move the voltage cutoff point. There are industry standards on the way to adjust most pots to increase or decrease resistance but the best way is to just check with a multimeter.

For a quick overview, there are three wires connected to the MAP sensor; a 5V constant power going to the sensor, a ground wire, and the signal wire going feeding back to the PCM and is what's used to determine manifold pressure. What you do is install the "MAP clamp" between the MAP sensor's output wire that goes to the PCM and the MAP sensor's ground wire.

To keep it very simple without getting into how the Zener diode works, you can think of a Zener as functioning like an on/off switch in this application. It's sitting there connecting the MAP sensor signal wire to a ground wire. If you were to do that wire a regular piece of wire it would short out and the PCM would never see any voltage. Instead it doesn't do anything until the voltage output coming off the MAP sensor goes above a certain point it and then it 'turns on' and dumps the excess voltage to the ground wire (i.e. shorting out the voltage that would normally go to the PCM by dumping it into the ground). That in turn limits what is left that can make it to the PCM.


Now the steps to measure what your MAP clamp is set to. Going off the factory service diagram the following color codes correspond to the following wires on the MAP sensor harness:
Orange --> +5 Volt supply
Black/Light Blue --> Ground
Dark Green/Red --> MAP signal to PCM

Like I mentioned there are a few different ways to construct a MAP clamp but it should be soldered between the ground and signal wire. If you don't have a multimeter you're going to need one and can pick up a cheap digital one for around $10 at places like Wal-Mart and most auto part stores. With the ignition off you want to disconnect the wiring connector from the MAP sensor. Then looking at the plug identify which wire is which according to the color codes listed above.

Before you can measure anything you want to take a small piece of jumper wire or a paperclip and connect the pins in the connector for the +5 Volt supply to the pin in the connector for the MAP sensor signal wire (then if you turned the ignition on without a MAP clamp it would cause the PCM to see a full 5V from the MAP sensor and think you are at full boost).

Next step is to set the multimeter to read DC voltage. You want to use the scale or range that can read 5 volts, which on most will be something like a 0-20V range. What you want to do next is expose the electrical connection made when the MAP clamp was installed. You might need to remove the electrical tape, etc. to do this. Then take the metal tip of the red multimeter probe and touch the connection on the dark green/red (signal) wire side of the MAP clamp and place the tip of the black probe on the black/light blue connection side of the MAP clamp. Turn the ignition to the "run" position without starting so it provides the +5V supply to the MAP sensor. Read what the multimeter displays and then adjust it accordingly. A lot of the potentiometers are cheap and can shift a little so you're still best to start modifying A/F with it max'd out and not clamping (which would be 5V during this test). Remember that the max voltage you read on the multimeter can be compared to the linked charts earlier in the thread to give you an estimate of what the max boost the PCM will see. Since you don't know what's safe or not for your particular setup this won't do a ton of good for the initial tuning process.

When you're done just remove the jumper wire and plug the harness back into the MAP sensor, make sure you wrap the MAP clamp connections back up (3M/Scotch Super 33+ electrical tape is next best after shrink wrap), and I'd also reset the PCM since it will probably throw a code for MAP voltage too high during the test. You could also just use the probe of the multimeter in the back side of the MAP sensor connector but there's an increased chance the MAP sensor itself could be damaged which is why it's best to take it out of the loop. So there you go. :thumb:

evil_2
10-27-2019, 06:08 PM
Do you have a multimeter and/or do you know how to use one? There are a few different designs and ways to put them together, but a MAP clamp essentially is based around one or two Zener diodes (which is what 'limits' max voltage) and a potentiometer (variable resistor) that allows you to adjust and move the voltage cutoff point. There are industry standards on the way to adjust most pots to increase or decrease resistance but the best way is to just check with a multimeter.

For a quick overview, there are three wires connected to the MAP sensor; a 5V constant power going to the sensor, a ground wire, and the signal wire going feeding back to the PCM and is what's used to determine manifold pressure. What you do is install the "MAP clamp" between the MAP sensor's output wire that goes to the PCM and the MAP sensor's ground wire.

To keep it very simple without getting into how the Zener diode works, you can think of a Zener as functioning like an on/off switch in this application. It's sitting there connecting the MAP sensor signal wire to a ground wire. If you were to do that wire a regular piece of wire it would short out and the PCM would never see any voltage. Instead it doesn't do anything until the voltage output coming off the MAP sensor goes above a certain point it and then it 'turns on' and dumps the excess voltage to the ground wire (i.e. shorting out the voltage that would normally go to the PCM by dumping it into the ground). That in turn limits what is left that can make it to the PCM.


Now the steps to measure what your MAP clamp is set to. Going off the factory service diagram the following color codes correspond to the following wires on the MAP sensor harness:
Orange --> +5 Volt supply
Black/Light Blue --> Ground
Dark Green/Red --> MAP signal to PCM

Like I mentioned there are a few different ways to construct a MAP clamp but it should be soldered between the ground and signal wire. If you don't have a multimeter you're going to need one and can pick up a cheap digital one for around $10 at places like Wal-Mart and most auto part stores. With the ignition off you want to disconnect the wiring connector from the MAP sensor. Then looking at the plug identify which wire is which according to the color codes listed above.

Before you can measure anything you want to take a small piece of jumper wire or a paperclip and connect the pins in the connector for the +5 Volt supply to the pin in the connector for the MAP sensor signal wire (then if you turned the ignition on without a MAP clamp it would cause the PCM to see a full 5V from the MAP sensor and think you are at full boost).

Next step is to set the multimeter to read DC voltage. You want to use the scale or range that can read 5 volts, which on most will be something like a 0-20V range. What you want to do next is expose the electrical connection made when the MAP clamp was installed. You might need to remove the electrical tape, etc. to do this. Then take the metal tip of the red multimeter probe and touch the connection on the dark green/red (signal) wire side of the MAP clamp and place the tip of the black probe on the black/light blue connection side of the MAP clamp. Turn the ignition to the "run" position without starting so it provides the +5V supply to the MAP sensor. Read what the multimeter displays and then adjust it accordingly. A lot of the potentiometers are cheap and can shift a little so you're still best to start modifying A/F with it max'd out and not clamping (which would be 5V during this test). Remember that the max voltage you read on the multimeter can be compared to the linked charts earlier in the thread to give you an estimate of what the max boost the PCM will see. Since you don't know what's safe or not for your particular setup this won't do a ton of good for the initial tuning process.

When you're done just remove the jumper wire and plug the harness back into the MAP sensor, make sure you wrap the MAP clamp connections back up (3M/Scotch Super 33+ electrical tape is next best after shrink wrap), and I'd also reset the PCM since it will probably throw a code for MAP voltage too high during the test. You could also just use the probe of the multimeter in the back side of the MAP sensor connector but there's an increased chance the MAP sensor itself could be damaged which is why it's best to take it out of the loop. So there you go. :thumb:

i own a fluke multimeter...actually i repair the electronic weapons system componenets on f15E strike eagles for the air force...

i totally undertsand your directions and running a jumper makes this install totally easy..thank you for your wisdom..i appreciate it..

blackbird
10-27-2019, 06:27 PM
Then you should be all set. My last four years active duty were spent teaching basic electronic theory so that post is the really, really "simple" version as far as describing how everything is working and what you're doing but it should get the job done.

evil_2
10-27-2019, 06:29 PM
Then you should be all set. My last four years active duty were spent teaching basic electronic theory so that post is the really, really "simple" version as far as describing how everything is working and what you're doing but it should get the job done.

cool, what branch were you in?

blackbird
10-27-2019, 06:45 PM
Marines for very close to ten years. Went to the dark side at the end of last year.

evil_2
10-27-2019, 06:47 PM
Marines for very close to ten years. Went to the dark side at the end of last year.


im a Staff Sergeant in the air force..ive been in almost 12 years

blackbird
10-27-2019, 06:54 PM
I was a Staff Sergeant as well, but the difference was that I was also an E6. :jester: j/k Both my parents were in the Chair Force during the Vietnam era, my grandfather was in the Navy during WWII, and I have a cousin in the Army. We used to have some gentle ribbing and inter-service rivalry at family gatherings.

evil_2
10-27-2019, 07:02 PM
I was a Staff Sergeant as well, but the difference was that I was also an E6. :jester: j/k Both my parents were in the Chair Force during the Vietnam era, my grandfather was in the Navy during WWII, and I have a cousin in the Army. We used to have some gentle ribbing and inter-service rivalry at family gatherings.

chair force.....lol

wish i had a "chair" job...lol

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