Very technical electrical modification to the throttle peddle question !

[Blazerfrazer]

Hi All hope you can help or can point me in the right direction! I have a 160SR that ( don't laugh ) I use for driving lessons, I am a driving instructor.
I used a sport + 1.2 before and it was a great little car. The problem is that the throttle peddle is a little sensitive for when the pupils set the gas to find the biting point. I took the peddle off in the hope that I could perhaps just add a resistor to the wiring that would allow me to change the resistance at the touch of a switch. I hoped that full throttle on the pedal would only register half throttle as far as the ECU is concerned. This also would give a little less sensitivity when first pressing the pedal. At the moment you only have to press it about 2 or 3mm and it revs right up! Basically I want to calm it down a bit, then on my way home I can switch it back and hoon home lol. I became stuck when I discovered more wires than I expected! any bright sparks out there able to help me? thanks.

 

[Ed]

Probably something I could do, but I would need to dissect one to see how its made internally.

 

[Blazerfrazer]

Thanks for that, where would i go to find one? i will ask my local scrappy on monday, is this the place to find out if anyone knows where there is a complete car breaking as i need a parcil shelf, a wheel, a pedal now and a full 160 standard exhaust

 

[Ed]

Depends where you are really, there are usually a lot of breakers all over the place.

 

[MSG2]

I am into electronics, but from the look of it, it is not going to be easier, it looks like the (just by my guess) that the system uses some sort of digital encoder, hence why you have multiwire connector, but here is some simple solution which you might be surpriced can work pretty well.

Use a an extra return spring, this will make the pedal feel heavy, and a light touch will not make it rev mad, so you will need to press the pedal much harder to rev up!!

I discovered this phnomenon on my Hillman Hunter where I removed the accelerator return spring and all of a sudden the car started to feel very responsive, and fast!! so i never placed it back, the carbrettor had its own return spring so the butterfly would return to closed position on its own when let go off the pedal.

But if Ed can sort it out then fine.

Electronically if the output codes are digital then you could use an electronic control system where an input digital value calls a different output stored value using an eeprom, so one will firstly have to find out what the original output digital values are and then feed them into an eeprom which then outputs diffrent stored values half of the original, not that it can't be done.

I beleive (without looking into it first) that its a simple decoder using some fancy grey code (like binary encoders) gold plated disc and wipers to generate digital code relavent to the pedal position, wouldn't think it uses a simple resistor potentiometer. or has a potentiometer with analoge to digital converter.

its showing 6 pins so it could be 1 common and 5 data bits giving 32 seperate values for the full scale pedal travel, or if it has built in analouge to digital convereter then two pins for the power rail and 4 for the digital code giving 16 seperate values for the pedal travel.

 

[Ed]

I am into electronics, but from the look of it, it is not going to be easier, it looks like the (just by my guess) that the system uses some sort of digital encoder,

Unlikely imo since is possible to loose track of where you are with a digital encoder on something that does not sync repeatedly.

 

[MSG2]

Unlikely imo since is possible to loose track of where you are with a digital encoder on something that does not sync repeatedly.

well like I said without peeking into one, it is hard to tell, but i am basing my judgement on the number of pins from that device, since an analoug system would only need a few wires or a serial bus interface again works on a couple of wires, my bet would be on a digital encoding.

Ed, it would be nice to know what you find, just out of interest. good luck anyway.

 

[richj]

bet you 10 pence its analogue

 

[MSG2]

If it is analogue then it may be easier to change the sensitivity using either a non-linear pot, or may be playing up with a resitor in parallel rather than series, i.e the output wiper voltage is shunted by a resitor across wiper and ground so as to give lesser value change for the same amount of pedal travel.

 

[richj]

I would guess there are two sensors, one for down, and one for up. That way, it doesn't matter if the input voltage changes because the ecu can 'work out' 1/4 down + 3/4 up, 1/2down 1/2 up etc. Probably vastly more complicated than that, but there my ten pence worth

 

[MSG2]

well, I got a 10p at the ready,(LOL) we will need Ed to send a probe and land it inside that module, I will put 20p on a rotary encoder, the digital value is what tells the ecu the relavent change in the position and the travel direction, well still, but definitely for the sake of interst I would love to know the truth and accept it happily once Ed lands a probe.

So if this is all electronic control, does this means that the induction air flow control is also electronicaly controlled possibly by means of a stepper motor?

 

[Ed]

So if this is all electronic control, does this means that the induction air flow control is also electronically controlled possibly by means of a stepper motor?

Yes all drive by wire throttles are stepper motor (or whatever) controlled

 

[Blazerfrazer]

WOW what a responce! thanks guys! the new pedal for disection just arrived and i am about to take it apart!! will post pictures this evening or tommorow morning, thanks again

Hi, well i took it apart and it came apart much easier than i thought, shame as i wouldn't have got this one to take apart if i knew! safe than sorry i suppose. the first side that came off revealed a large spring....

then the other side came off and i stabbed myself with the screwdriver!! but i was please to see a variable resistor! 4 tracks and 6 connections,

i will draw a diagram of where they all connect to and add it later.

i notice that this pedal from a 1.0 micra they sent me has a different part number, i dont think this will a problem as i only got it to see inside one, not to use it.

http://www.btinternet.com/~frazer.smith1/forums/pedal3.JPG


Ok guys! hit me with it

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Ok, I have cut more of it away now to expose the strip and show the end of the wiper arm. you can see where the tracks go but I have no idea what's going on. I notice a second black strip that had nothing rubbing on it and 5 other pads made of the same material, I suppose they are set resistors?

the wiper arm I have noticed has 2 of the 4 connections joined.

 

[Antony]

ah the joys of having a whacking great cable atatched to the engine...lol

my instructor had a 1.2 k12 (yes everyone i learned to drive in a k12) and that would rev up realy quickly but was completely gutless. i couldnt go over 50mph up a hill....made me look a right git.

 

[Blazerfrazer]

I have removed the strip and put it on the scanner, then I noticed that 2 of the strips have a solid connection running through them, so I scanned the other side to show you and flipped it so it matches the other side for comparison.

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[MSG2]

very interesting blazerboy, I have to commend you at disecting this and photographing it really brilliantly, so from here I or spmeone else like Ed should be able to figure out what you need to do. Amazingly I had not expected it to have variable resitor!!!

I thought it would be a high tech digital encoder!!! I owe RichJ 10p!!!

first of all, blazerboy, which side do the wipers rest when the pedal is up? left or right ? from the wear on tracks it seems it rests on the left, but correct me if I am wrong.


The 5 tracks of various lengths you see are thick film resistors to fine tune the response!! so basically you will be manipulating these externally by adding or taking resistance away.



Also may I caution you that no attempt should be made to solder any resitors on this plastic flexiboard, as the soldering iron will just melt through and ruine it completely. so any resitors will have to be added on the outside on to wires etc,


Only thing you can do is try and insert a resitor or resitors in series with various pins and observe what happens, it will have to be a trial & error, unless someone else has done it previously and changed the response and knows what to do exactly.



Alternative, a primitive solution is to use a heavy return spring and you will be pleasantly surprised!!

I have removed the strip and put it on the scanner, then I noticed that 2 of the strips have a solid connection running through them, so I scanned the other side to show you and flipped it so it matches the other side for comparison.

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Didn't get what you meant by your last statment re two of the strips having solid connection.....do you mean the two tracks running from the left to right in your bottom picture to pins 1 & 2.

 

[richj]

lol I take paypal

I think I would use Op amps. Simply divide the voltage by two. But there are two sensors (in the pic). You would need to map/measure exactly what they do.

I would also feel slightly uncomfortable having my throttle controlled by DIY electronics

 

[Blazerfrazer]

Hi, what i meant was, there is a copper track running the length of the top and bottom strip, have a close look at the bottom picture, so they are not variable like the middle to strips. Yes i woulds like to add resistors to the external wiring so that i can short out the added resistors with a switch, this would allow me to put the car back to normal with a switch in my glove box. I purchased this second pedal with the connector cut from the donar car, this means i can use this plug to easily connect to my car for tests, as soon as i have been told what to measure i will go out to my car with a meter and take a resistance reading.
The resting point is to the far left of the track when the pedal is not pressed.

I have done a simple diagram of the connections, the red shows the resistors, i have drawn them so scale so you can see the difference in the sizes. both the wiper arms work at the same time and they start from left to right ( left is no gas )

 

[Ed]

Before you do anything else you need to measure and record the voltages on pins 1 and 6. from 0-100% throttle.

If It was me I would then feed this into a pic and make a lookup reference table to do a scaled conversion on it.

 

[MSG2]

Hi, what i meant was, there is a copper track running the length of the top and bottom strip, have a close look at the bottom picture, so they are not variable like the middle to strips. Yes i woulds like to add resistors to the external wiring so that i can short out the added resistors with a switch, this would allow me to put the car back to normal with a switch in my glove box. I purchased this second pedal with the connector cut from the donar car, this means i can use this plug to easily connect to my car for tests, as soon as i have been told what to measure i will go out to my car with a meter and take a resistance reading.
The resting point is to the far left of the track when the pedal is not pressed.

I have done a simple diagram of the connections, the red shows the resistors, i have drawn them so scale so you can see the difference in the sizes. both the wiper arms work at the same time and they start from left to right ( left is no gas )

Amazingly you have figured it out exact !! 10/10, you must know your stuff!!! Aah but there is a small error, the wiper shown from pin 6 should point to the right Pin 1, this is where the position would be relavent to the wiper position of the left set up. but still well done!!

as you can see from your own diagram, and the position shown by your wiper arrows is with the pedal in the up position, hence resistance between terminal 1 & 6would be at its lowest (with your wiper pointer (pin 6) switched to the right towards pin 1, and same again for the lower track, the resitance between 2 & 3 will be lowest,

So you really need to check what voltage you are getting at pin 6 and pin 3 which are the two wipers, and also see what voltages are at all other pins, with pedal in the up position and the pedal in the down position, all voltages measured against vehicle earth or ground reference. This should give you enough idea what to do or which pins to modify either by placing a series resitors or shunting voltages using a paralell resitor.

The trick was the two solid tracks which you said ran at the back on the top strip and the bottom strip, as they make the top strip and the bottom strip as a wiper point.

Just updated your diagram accept the wiper is now in the position it should be.

Pins 3 & 6 are the actual sensing pins, where the potential changes due to the pedal position, so I belive inserting a series resistor in pins 3 & 6 won't do the job as this will only effect the current and not the voltage, but I beleive that altering the resistors to the other pins of the potentiometer may alter the required response by adding or inserting a series resitor to any of the pins 1, 2,4 &5 but not the 3 & 6, as I strongly beleive the ecu senses the voltage rather than the current sense through this variable pedal control.

I would experiment with something like a 5K preset and alter to see what happens to accelerator response, wheather you get any ECU faults due to ecu sensing a tamper with values. and then if it works , fine tune the presets and wire it to a switch so that as you could choose which response you want as you stated.

Amazingly you have figured it out exact !! 10/10, you must know your stuff!!! Aah but there is a small error, the wiper shown from pin 6 should point to the right Pin 1, this is where the position would be relavent to the wiper position of the left set up. but still well done!!

as you can see from your own diagram, and the position shown by your wiper arrows is with the pedal in the up position, hence resistance between terminal 1 & 6would be at its lowest, and same again for the lower track, the resitance between 2 & 3 will be lowest,

So you really need to check what voltage you are getting at pin 6 and pin 3 which are the two wipers, and also see what voltages are at all other pins, with pedal in the up position and the pedal in the down position, this should give you enough idea what to do or which pins to modify either by placing a series resitors or shunting voltages using a paralell resitor.

The trick was the two solid tracks which you said ran at the back on the top strip and the bottom strip, as they make the top strip and the bottom strip as a wiper point.

 

[Blazerfrazer]

Hi, i did these two diagrams before i checked the forum, here is what i have

Frazer

 

[MSG2]

I will look into your resistance measurements and study them , in the mean time something struck me, because I cannot see a good reason for Nissan to have two seperate variable potentiometers to determine the pedal travel, so I thought may be the reason is so that you could choose how you want your car to respond???? so may be somewhere you might be able to select a button that then changes the rate at which the accelerator pedal responds, like for example in Vauxhalls they use a "Sports" button which increases the response in some way.

 

[Ed]

I will look into your resistance measurements and study them , in the mean time something struck me, because I cannot see a good reason for Nissan to have two seperate variable potentiometers to determine the pedal travel,

A really obvious one to me is for error detection. I have not tried, but you may find they are a specific ratio to each other, if this changes then the ECU can detect there is a fault with the sensor.

 

[MSG2]

There you are Ed, you could well be right about the self monitoring against malfunction. The relationship or the ratio of the two wiper voltages is exactly 1:2, so one pin outputs a duble the voltage, so that means in order to fool the sytem we will have to modify both poteiometers such that they remain balanced within that ratio.


Thanks Ed, yes it must be some sort of error detection, I can imagin if there was problems with wires shorting or becoming open circuit and it could send the car revving mad!! Thanks for your thoughts on this. cheers

Well having studied all the parameters, I think you could change the pedal response by simply changing the +5V to a lower value, this will alter the wiper voltages in the same proportion, so no need to worry about resitor balancing,


So if you add for sake of argument a series resistor of say 1K then we must add a series resitor of 2 K in the other circuit.
to maintain the tracking ratio.

But an easy solution is to use a silicon diode in series with the +5V supply at pins 4 & 5 , this will reduce or drop the the +5V to 4.56V and so give a slightly lower value at the wipers proportionally in the same ration to each other.

You can try one or 2 or even 3 silicon diodes in series with the pins 4 & 5 which can be connected together and as they both require a +ve feed on them so by applying a lower +ve voltage of say 4V by using 2 silicon diodes in series, this should alter the pedal response.


But, there may be a snag, will the ECU detect that the idle accelerator voltage has gone down below the standard set value of 0.387 at pin 6, and twice this ie. 0.765 at pin 3. , since if you feed lower voltage into the pots it will give proportionally lower voltages all around.

In my view it shouldn't cause any problems, but we don't know, it might effect the engine idle speed, but I can only guess. If it does then we will have to find a way of keeping the minimum voltage points unaltered but alter the rest of the response using some other trick.

So please get hold of a few silicon diodes and experiment and report us the results. If this doesn't work you will have to get Ed to sort a look up table using a Pic !!! pics are my weakness!!

Added comments on 23rd Jan 09 9.00am

It is quite easy to predict the voltages when you alter the supply voltage, as all the voltages on a potential diveder network will fall proportionally, so for example if you dropped a +5V to 4.4V using a single silicon diode, then 4.4V is 88%, hence the voltages at pin 3 & 6 will also fall by the same % amount , so for a 0.387 it will be 0.340v at pin 6.
and for 0.765v it will be 0.673V at pin 3.
These figures maintain the same ration but the ecu may not accept them.

 

[MSG2]

waiting for any update.
I think that one of the things that might happen is the ecu might not work on these lower values than the preset values by Nissan, and even if the engine idles independently from these values, then pressing on the pedal for a few mm down would probably have no effect until the pedal output voltage has reached beyond the preset Nissan values, so the pedal may not be responsive for a few mm of travel and then it will become responsive and the rate of change will be lower than before, but it is the dead spot on the pedal that is what i am worried about, so do you think we will have to adopt another solution as stated by Ed using a pic and look up table.

 

[Blazerfrazer]

Hi, i am just about to shoot down to maplin for some bits, i will have time today to try stuff and report back, do i just ask for 3 or 4 regular silicon diodes or do they have a proper name, and what about a few combinations of resistors of different values. as soon as you confirm i will go down. ( will check the forum often today )

Just a quick update, i pulled the plug on the pedal and started the engine. it hardly ran so i stopped it. i then plugged it back in and it ran really badly. there was a cloud of smoke that i assume is unburnt fuel and after 30 seconds the idle was back to normal. i went for a drive to check i have not broken the car!! and i noticed the yellow engine managment light is now on all the time. hi hope i have not damaged the cat converter. it only ran for 8 seconds without the pedal connected. i did the test to see how interested the ecu would be about the idle voltage. will the light go off in the end? or do i need to reset something or disconnect the battery.

 

[MSG2]

Disconnect your battery for 5 minutes and hopefully this will reset the ecu if not then don't wporry at this stage, it will get reset by itself after a few switch on and offs of the ignition but on that I( am not 100% sure.

Regarding the diodes, just ask for general purpose silico diodes rated at 1 amp exact type 1N4001, 1N4002, 1N4003 any of these, the last number does not matter as that denotes how much voltage a diode is rated at, as you are dealing with just 5V so any of these diodes will do. And remember the diodes have a silver band close to one end, this end denotes cathod, which usually means the current flows one way from cathod to anode as in electron flow, but as in conventional current flows from positive to negative so the diode's silver band side is where the positive will emerge from when you apply positive to the other side where there is no band.


here is how you would try:

So if you were to apply negative to that side where there is no band, then this negative will not pass through, thats what the diodes are for , a kind of one way street for current flow.

As for the resitors, just get a few two will do presets, small ones approx 1/2 square witha screw driver slot turn.

I am not so familiar with Nissan's fault codes, on Vauxhalls I can extract the fault codes from the ecu by earthing a certain point on the diagnostics adaptor , and this then makes the ecu light flash, and we call it "flash the code" There must be something similar available on Nissans, and a possible way of reseting the ecu.

Your car will run very rough when a serious fault such as the one you have generated defaults the ecu into a limp mode.

Have a look at this thread tells you if you might be able to reset your ecu code following magpie's instructions in this thread.
http://www.micra.org.uk/showthread.php?p=220477&highlight=fault+code+flashing#post220477

and have a look at this as well:http://www.micra.org.uk/showthread.php?t=27058

 

[Blazerfrazer]

Hi, I have done some testing, I got all the bits from Maplins and I connected the diode as per the diagram, here are the results.

I connected the diode and the car started normally and ticked over at aprox 1000rpm which is normal I think, cant remember what it was before I started to mess with it DOH! any way, I think I notice the little dead spot that you mention, but only just. the dead spot is only just noticeable with careful pressing and listening. The rev response is the same as before. Then I took the diode out and tried again to check what the pedal felt like when back to normal, to see if it had a slight dead spot anyway. The first thing I noticed when removing the diode was the tick over went up to 2000rpm so it must have learnt the new value, then after a few seconds it re learnt it again and went back to 1000rpm ( clever little thing! ) the dead spot was gone I think but it was so hard to tell. I await your prognosis before I try any more diodes or resistors.

 

[MSG2]

You won't harm the ecu by adding a few more diodes, add two and then study the response, and this will make the dead spot a little more, and the response will be slower, then try even 3 diodes or even 4 , but all diodes must face the same way (like batteries in a torch)

Also is there any way you can note the RPM v/s the pedal travel on some sort of cardboard scale held steadily next to the pedal, this a little more scietific way to find out what changes have occured to the response for the same amount of pedal travel, the reves should in my opinion rev slower.

Bear in mind that by adding more diodes the upper most voltage on the wiper pins will be lower than before and so under load the car engi8ne will not reach full revs, but this is to be expected with this method. This should not be an issue with learner drivers.

 

[Blazerfrazer]

I am uploading some utube videos of some tests right now, I will put the links up as soon as they are ready! ( 30 mins i expect )

http://uk.youtube.com/watch?v=-vodni23RR4

http://uk.youtube.com/watch?v=202OgOWOyZE

http://uk.youtube.com/watch?v=ttOnQ5MPlVo

There is a snag even if this 4 diode methods works and that's is its not easy to change the setting back, it takes about 5 minutes of messing about switching the engine on and of to get the ecu back to normal. It revs right up to 4/5000rpm when I remove the 4 diodes. I need to be able to switch it back easily or I might as well got a 1.2! let me know what you think when you have seen the videos

 

[MSG2]

for some reason the you tube videos keep saying video not available.

regarding the ecu not adjusting to normal, don't let the circuit become open at any time, as this might cause the ecu to jump to high revs, to remove the diodes out of the circuit i.e. to put it back into normal mode, simply bridge the diodes, i.e. take two wires, and solder one wire to the begining of the first diode and the other wire solder to the end of the last diode (the 4th diode) then just flick the switch, which bridges or bypasses all the 4 diodes, now, if you think what will happen of course the wiper voltage will rise and the ecu thinks the pedal is down!! so starts to rev mad on no load on the engine, so you will need to reset the ecu by switching the engine off and on again, it may be the only way out for now, this phenomenon would happen even if you were to use other methods, since we did not realise that this damn ECU is self learning thing!! so it will do the same with any other method deployed. i.e. not reset factory default values.

BTW, what is the status with your ecu light now, has it reset or still on?

 

[Blazerfrazer]

Hi, it takes a little time for youtube to process them, they should work soon. i will try what you suggested with the diodes and not let it open circuit, but i did turn the ign off every time i changed anything. it makes sence though, once it learns with the diodes in place, removing will make it think the pedal is pressed

Is it possible to remap the ecu?

O, i forgot to say, the ECU light is still on

 

[Ed]

BTW I think a diode is a bad way of doing this. You never use diodes in voltage dividers in this fashion, only if your creating a ref. voltage say with a zennor diode.

 

[Blazerfrazer]

Come on youTube !! sort it out!

 

[MSG2]

BTW I think a diode is a bad way of doing this. You never use diodes in voltage dividers in this fashion, only if your creating a ref. voltage say with a zennor diode.

every one has a way, I am not using diodes as a potential divider, so for a start you did not grasp the idea of using diodes, all the diodes are doing is providing a lower operating voltage for the potential divider network, so instead of having a scale from 0.7V to 4.5V from up position to the down position, using 4 diodes are removing
0.6 x 4 =2.4V from the 5 volt supply rail, so the potential divider network is now spreading lower span of voltage i.e 5.0-2.4 = 2.6v so this should give you roughly a voltage from about 0.3V to a maximum of about 2.5V on the wipers , hence the pedal travel scale has been alterd to a twice as slow response. And this will also limit the engine reves which may be benificial in the case of learner drivers.

Of course there are other ways of doing it digitally, or using pics, but first always an easyiest solution is better.

Hi, it takes a little time for youtube to process them, they should work soon. i will try what you suggested with the diodes and not let it open circuit, but i did turn the ign off every time i changed anything. it makes sence though, once it learns with the diodes in place, removing will make it think the pedal is pressed

Is it possible to remap the ecu?

O, i forgot to say, the ECU light is still on

I beleive so, it should be possible and if that can also be done in a way that you can switch in and out different responses.

Better still I suggested a simple tension spring!!

 

[Blazerfrazer]

Hi, when the youtube videos load, you will see just how little the pedal had to move to rev right up to 5000rpm, i am sure a spring will work a bit but it is sooooooo sensitive!

 

[MSG2]

Hi, when the youtube videos load, you will see just how little the pedal had to move to rev right up to 5000rpm, i am sure a spring will work a bit but it is sooooooo sensitive!

is this with mod or without mod?

while we are waiting for Youtube loading up, can you tell me if the 4 diodes worked somewhat, was there a big dead spot?

Obviously, there are still some more ways to overcome the problem where the ecu does not restore to default values when the diodes are taken out or bypassed with a flick of a switch.

this can be achieved by applying a bias voltage to the wipers to retain the standard values whilst the pedal is in the up position. This bias voltage has to be applied in such a way that it does not effect the potential divider network voltage, but after a small dead spot the voltage on wipers will start increasing slowly giving higher engine speed but under a greater control.

Ed, please, by all means suggest an alternative circuit, and let us see what we need to do, any circuits, etc, and it will be intersting obviously.

saw the videos, quite intersting, and I saw the result when you used 5 diodes, uisng 5 diodes will take out 0.6v x 5 =3volts away from the original 5.0V supply across the potential divider network, and so you will get only 2V left across the potential network, so with 5 diodes it is gone too slow, keep 4 diodes and switch them in and out without making the circuit go open, in other words bridge the diodes with a switch wired across the diodes,

Blazerboy, being that you are a driving instructor, I feel bad having to tell you that in the video you are seeing an engine with absolutely no laod, not even the clutch when depressed imposes some load on the engine, so what i suggest that you actually try the mod in a real given situation by driving and don't forget when you get a biting point that is a load on the engine and stops it revving away freely, so please do a small test drive, and I don't ned to tell you if anything goes hay wire, i.e engine goes raving mad, depress clutch and brakes!!! lol.

honestly you will need to conduct real tests.

 

[Ed]

I'm sorry I don't have the time I would like to, to write an extensive post but my thoughts are as follows:

You want to change the ratio of the throttle opening Vs pedal position. Adding diodes however you want to do this will simply not work. It wont change the ratio of the tracks, or how the throttle opens, therefore it needs to be abandoned, and a more suitable method established. I am unfortunately not able to be specific in how you should do this with diagrams etc simply due to liability.

Further to this I'm becoming slightly concerned about what is going on here simply due to the fact of safety. This after all is a driving school car were playing with here. And IMO too much guesswork is being done.

Anyway:

Full throttle and Closed throttle voltages must remain as close as possible to what they would be normally.

Have the closed throttle and full throttle voltages even been established yet?

All that has been done so far is to cause the car to run badly and the ECU light to now be on.

May I suggest a step back to reconsider the best way to do this, as so far what has been tried has at best been risky, and at worse dangerous.

 

[MSG2]

I'm sorry I don't have the time I would like to, to write an extensive post but my thoughts are as follows:

You want to change the ratio of the throttle opening Vs pedal position. Adding diodes however you want to do this will simply not work. It wont change the ratio of the tracks, or how the throttle opens, therefore it needs to be abandoned, and a more suitable method established. I am unfortunately not able to be specific in how you should do this with diagrams etc simply due to liability.

Further to this I'm becoming slightly concerned about what is going on here simply due to the fact of safety. This after all is a driving school car were playing with here. And IMO too much guesswork is being done.

Anyway:

Full throttle and Closed throttle voltages must remain as close as possible to what they would be normally.

Have the closed throttle and full throttle voltages even been established yet?

All that has been done so far is to cause the car to run badly and the ECU light to now be on.

May I suggest a step back to reconsider the best way to do this, as so far what has been tried has at best been risky, and at worse dangerous.

With all due respect Ed, you seem to think that we don't know what we are doing and that we are gussing all the way, well not quite true because our mods have been thought with a lot of consideration and has resulted in what we expeceted it to achieve.

You obviously have missed some of the posts in which we stated the pedal down and pedal up voltages. They have indeed been established.

For the sake of simplycity, what we have done is achieved half a throttle response when the pedal is fully deperessed, now you will find that for most normal driving one doesn't even fully push the pedal down to the floor, unless you are a boy racer, most learner drivers will probably not use more than a quarter of the pedal travel, still leaving plenty in reserve, and once we have sorted out the bias voltages that will make the mod switch in and out seamlessly.

Further to your comments about the ECU light having tripped in, this was nothing to do with the mods using diodes or anything for that matter, this happened when Blazerboy disconnected the pedal module from the ECU while the ignition was on or the engine was running.

Lastly please supply any evidence that the engine has been running badly, you might not have seen the 3 videos in which there is no sign of engine running badly, you are obviously missing something.

finally with regards to the ecu light, it will be reset after following instructions from a link in which it exlains clearly how to do that.

So why would this mod be any more dangerous than the car already is , just touch the pedal and it revs madly, thats more dangerous in my view.

I think your argumenet is based on irrational thinking or just some bad feelings perhaphs.

we have achieved what we wanted and it is very safe and the switch over will be seamless as well.

but as I said best mode would have been a more stronger return spring, this would have definitely made the pedal feel less responsive or much harder to press down to achieve the same respons than before . No hard feelings mate.

 

[Ed]

Ok, missed the voltages. Your ECU info links referred to the K11 micra. This thread is about the K12, which uses an entirely different ECU.

Anyway, I shall leave you to it, if its going to get personal I'm simply not interested any more.

 

[MSG2]

Ok, missed the voltages. Your ECU info links referred to the K11 micra. This thread is about the K12, which uses an entirely different ECU.

Anyway, I shall leave you to it, if its going to get personal I'm simply not interested any more.

No worries mate, as I said we are all entitled to our opinions, which sometimes can be true and at other times based on irrational thinking.

I share your safety concerns, and these are our concerns too, we wouldn't delve into something if we did not know what we were doing, it is not a guess work here, we are heading in the right direction after Blazerboy exposed the device and took pictures of it, there are no more guesses here, yes there was a question as to why there are two sets of tarcks, and you answered that correctly, but we would have found that out beleive me. We know most things are there for a purpose.

I can rest assure you that this mode won't cause any danger, provided it is implemented correctly and with good workmanship and all joints and connections made properly.

I can also assure you that once Blazerboy has reset his em light, and the mode with 4 diodes with a bias voltage to maintain the minimum refernce voltages to the ecu, there will be absolutely no problem and the switch over from one mode to the other will be seamless.

Safety obviously is the prime concern in any field, be it engine mods or suspension lowering etc, and the same applies here too, we will take utmost care to implement this device without any danger risk to anyone. it is a mode no different to an ecu remapping, except we are modding the hardware rather than the software.

Any way thanks for your valuable contribution. I appreciate that. cheers.

 

[Blazerfrazer]

Anyway, I shall leave you to it, if its going to get personal I'm simply not interested any more.

Hi Ed, please dont loose interest, you and MSG2 have all the brains here!! I need you both !! the diode method might still stumble, i dont even know what you you mean by "pics" yet!! dont go.....

Blazerboy, being that you are a driving instructor, I feel bad having to tell you that in the video you are seeing an engine with absolutely no laod, not even the clutch when depressed imposes some load on the engine,

Hi, just a little info on why i would benifit from this mod. mostly all my pupils have no trouble with driving my 160 as they all started with my 1.2 k12. its just the NEW pupils that struggle. Imagine me sat at the side of the road with a pupil that has never pressed any pedals before, i am getting them to feel for the biting point for the first time, " press the gass a little, not too much" and yes you see what i mean now, there is a red k12 sat at the side of the road giving it death ,5000,6000 rpm then back down to nothing..lol when you see the video "standard" you can appreciate how difficult it must be for them, its hard for me or anyone if it isnt immeadiatly backed with a little clutch stright away. thay can take 10 seconds or so to find a bite when they dont know when it will come, they are nervous first time also, and they know its wrong when the engine makes all that noise and it puts them off.

i will test drive with 4 diodes today and report back very soon. Frazer

 

[richj]

I can't wait to see how this turns out The diodes are reducing the output voltages across the whole range. WHY?? thats not the desired result is it!

 

[MSG2]

I can't wait to see how this turns out The diodes are reducing the output voltages across the whole range. WHY?? thats not the desired result is it!

Well, if you go back to the very 1st post on this thread, it clearly says what is to be desired or expected by Blazerboy, and I have come up with a very simple solution which literally divides the pedal range by half, with this set up for learner drivers, you would never see learner drivers belting around the streets with their foot right down !!

It provides a simple and effective soloution for now, but a more elaborate solution is to have the whole pedal range but with a slow response, which again can be easily implemented using A/D converters and looking up alternative values stored in an eeprom and then converting this new value back into analoge using a D/A converter.

Its not like I don't know my stuff. and why when I suggested the most simple solution to start with that does not interfere with any electronics such as using a more powerfull return spring that will effectively give you a different feel when you press the pedal, you would seem to be pressing it quite hard but the pedal has barely moved, so this way the engine will rev miserly all because of a simple principle ......the heavier spring requires a lot of effort to press the pedal down. to a driver it would seem he has pressed the pedal quite a bit down whereas he has barely managed to move it.

I have no intention to fall into an argument with Ed, who has been a member here since 2001 with more than 11,000 posts contributed, so I absolutely respect that and him being able to be more reasonable in his coments.

Blazerboy has explained how his new learner recruits are finding it extermely difficult to control the engine revs, and he has demonstarted in his video how dangerous it is at the moment, a slight clutch pedal slip and that engine doing 5000rpm I would think is more dangerous than an engine purposely restricted from revving more than say 3000RPM under load. Most cars will have their max torque at less than that any way.

 

[richj]

I'm not suggesting you don't "know your stuff". The diode idea is a bad one, it isn't a solution to the problem -> it won't work. As far as this thread reads, there is no indication that you: firstly know what the 2nd potentiometer is for and secondly know how the ecu treats the two voltage values. As such any suggestion you make is a guess - and seeing how we are talking about the throttle, i think this is dangerous and probably irresponsible. You questioned the damage to the car comment - The unburnt fuel comment may or may not be an example of this.

As far as I am aware, Ed is or has been a professional electrical engineer of some description.

The light has come on because the value is lower than the acceptable range, indicating a faulty part.

What blazerboy wants is the initial throttle (fully up) to be the same, and the final throttle (fully down) to be half what it is, with a linear ratio between the two.

I think you should take a step back and propose ideas for criticism before you recommend someone starts messing with a very important element of car control and safety.

Firstly, the relationship between the two potentiometers needs to be clearly identified. Once you/we have done that - its time to talk about a way to achieve the desired result.

 

[MSG2]

Firstly, you said the diode idea is a bad one, how if I may ask you? explain to me why is it a bad idea? Did you even know why I am using diodes for? Have you any idea what is the intended purpose of these diodes in this particular senario? diodes aren't just used for reactification, but for lots of other purposes too, one of which being a thermostate sensor for a fridge!!

And why wouldn't it work? when the fact has been demonstarted on Blazerboy's video clips. What further evidence do you need to be co nvinced that my idea is actualy quite a simple one and very effective and very safe indeed, safer than the space shuttle!!

Secondly, why is it important to know what the two potentiometers do? we already know they generate two values one being twice that of the other for error detection, and to control the throttle, which is what we are trying to do, except we are fooling the ecu that we have only pressed the pedal half way when the fact is we are pressing it down fully, so what is the difference apart from limiting the engine revs to max 3000RPM under full load!

Thirdly, the em light came on when he disconnected the module from the ecu harness and turned the ignition on, that is before even carrying out any modifications. so please read the posts clearly and get your facts right, the em light has since stayed on and we will be resetting it and you don't know if the em light will come back on if the ecu detects the lower pedal voltage, again this won't be the case when we have given the ecu a minimum bias value,

Fourthly, you have got all your facts wrong, at no time did Blazer wanted the initial throttle (fully up) to be the same, so basically you haven't even grasped the problem so I don't think you are in any position to issue criticism when you haven't even fully grasped the problem to start with.

Fifth, you suggested that I take a step back and propose ideas for criticism before I reccomend someone to start messing about with a very important element of the car control and safety!!

Oh boy!! Now if you go back again, to the very first post, Blazerboy has already suggested that he is going to try some resistors etc, so did I advocate him to do that, No absolutely not, he would have gone ahead and tried something any way, Blazerboy seem to know more about the problem than you could grasp.and he also knows how to reactify the issue, its just that he needed a little more guidance, and there is nothing wrong in suggesting a working remedy that is safer than a space shuttle. Have you got any facts that this mod is dangerous, have you actually seen the mod and tested it yourself to determine that it posses a danger. I can tell you it doesn't pose slightest bit of danger, and at a flick of a button it will resume normal response as mapped in the ECU.

Finally before all this happened, I knew what was going to come, its nothing new, so I even PM'd Blazerboy and notified him that when you have two or three people suggesting a remedy for a particular problem, there will be a clash of personality. And he replied do you think this might cause bad feelings, and I said it may, and it did, this is before I even started!!!

I have been through all this before and its not new, many people just don't like newcomers coming up on forums and suggesting clever little mods!!

So please allow us both to proceed with this clever little mod which will make Blazerboy's car more safer than it actually is now.

 

[Blazerfrazer]

oops, sorry guys. i feel bad that there is some friction, MSG2 did say there could be but through inexperience with forums i didn't understand. Please everyone calm down, i need all your support. I have now test driven the car with 4 diodes, please see the diagram. I have a feeling that the sharp throttle curve is just the same but comes in after 2mm of dead space. What I really need, I think, (if it's possible) is to change the curve so that the beginning travel doesn't have quite such an effect (see diagram: "proposed"). This isn't the actual curve I require, just an example of the shape.
I would just like to pick up on a couple of points. 1) the heavier spring idea might not be as successful as thought. the reason why I believe this is because although more pressure is required to press the pedal, once it does start to move the revs will still jump up high again soon after it moves. I'm really looking for physical travel not to have such an effect over the engine. 2) with regards to safety I don't see this as a problem because even when the engine is at 5k revs with 2mm of pedal movement, there is no guts. If the clutch pedal was to fly up you would get possibly the tiniest screech and the car would stall.
My only issue with my throttle pedal is the inability to instruct the pupils to set the gas approximately somewhere between 1500 rpm and 3000 rpm when teaching the biting point for the first time. When they try it's 5000 rpm or tickover. They manage it in the end as they get quicker at finding the biting point. But early on this is very frustrating for myself and the pupil. I'm able to make this comparison because of the 1.2 micra (K12) I was using before which has far more control with off load revs.

The 4 diodes although did have a dead spot that doesent matter to me, did seam much easier to drive for sure. I did what you suggested and shorted the diodes out with out opening the circuit ( with the ing off ) and it still was upset due the the new values it had learnt.

with the standard setup, it is possible to put the revs where you want them but you need to do it by hand or practice to death as it is so sensitive, the fact that you can carfully set the revs,leads me to think that the solution is possible

 

[Arnold]

MSG2 can you calm it down please, everyone is here to help and everyone has is entitled to their opinion on the best methods. Ed is an electrical genius, and i seriously would listen to the bloke!

 

[richj]

yes as i wrote above - the diode idea wont work, as demonstrated by the 2nd graph. There is no clash of personality - msg2 is just wrong on this occasion.

The throttle when the peddle is fully up, i.e the car is idling, should be exactly the same as it was before any modifications where made.

The throttle when fully down, i.e full throttle, should be half what it is standard.

Every point between the two should be half what it is normally. That way every 1mm of throttle has half the effect.

Msg2 - using diodes doesn't achieve that does it.

Your explanation of the two sensors is incorrect. I posted above what the actual reason for them is.

If you havn't already got this far, check out:

http://www.bba-reman.com/content.aspx?content=nissan_dtc_po221_tps

You should have notice the opposite values, (yes for error prevention) but not in the way you specified.

So yes, take a step back, post an idea and let us discuss and criticise it.

The solution i suggested first: a divider op amp and a multiplier op amp saturated at the new maximum throttle voltage is still the easiest way to get the desired result - but maybe not the best?

 

[MSG2]

Ok, it is good that you have plotted these and you have shown that with 4 diodes the curve has moved further down the pedal travel. in other words there is some dead area for the first few mm travel, which was predicted, but surely the rest of the curve cannot be the same as the curve without the 4 diodes.

Since the wipers of the potentiometer are getting half the voltage for the same amount of pedal travel, therefore the response curve has to be shallow and not the same as the curve without the diodes.

I suspect that the graph cannot be plotted accurately as there is no load on the engine, perhaphs you might bbe better of plotting again but have the engine under some load, which you can impose on it through having all your electrical gadgets on, such as the headlights, A/C, heaters, demisters, heated seats / whatever you can think of, this little load may yield a more accurate graph.