NITROUS OXIDE ( nos / n2o ) advice forum

Most of us at one time or another have had troubles from electrical interference on our controllers. If we havent personally, we know someone who has. many times the problems come from flyback voltage that occurs when the magnetic field around a solenoid collapses. extremely high voltage is sent straight to the controller and it scrambles things, or turns on voltage protection (which can shut off the unit or physically damage parts designed to be replaced if it happens.) ((( btw, i should note that the faster a solenoid pulses, the less time for the field to collaspe and the less flyback there is to begin with. on my bike i have 0 detectable flyback from the pulsoids at 38hz. i could probably pic some up with an o-scope, but if the controller cant see it, then its negligible.)))

Well, i didnt invent this solution, but it sure fixes the problem. the answer is a TVS Noise Suppression Diode. placed as close as possible to all solenoids on the vehicle. especially trans brake and air shifter solenoids that can flyback as high as 600v. one leg is wired in to each wire from the solenoid. alternatively, you can also use hot side switching and use the engine block as a ground. the hot side switch will force the flyback voltage to travel down the ground side, and the engine block will act as a large capacitor due to the alternator being directly attached to it. sometimes this works, sometimes it doesnt. Thirdly, and i have done this before, some vehicles use a 24 or 16v start/charging system and its hard to tap into it to begin with. in this case you can just use a small Lithium Ion battery at 12.6 volts and run a completely serperate circuit. the downside to this however is that you will have to use 2 data loggers. one for the nitrous setup and one for the engine. the reason being that each system will have a different reference voltage, if you monitor the voltage from one system but use the ground from another it will not be correct, or will fluctuate widly. the second downside to this, is that you didnt actually eliminate the flyback voltage, you just isolated it.

The simplest an best performing answer of all of the above is to use the diode. cheap, little bit of wiring, and it works. I havent seen any diodes listed on trevors site, so i will give you guys the link of what i use. Trevor you know as soon as WON sells it, ill be using yours! lol here you go


http://www.lingenfelter.com/mm5/merchan ... e_Code=LPE

lingenfelter is a very good company to deal with. i put them up there with WON in my "best businesses" category so dont be afraid to deal with them.

also this is not a "normal diode" so dont go to radio shack and think those will work (unless its atcually a TVS diode) These diodes are actually (normally) a bi directional clamping device. they allow current to flow either direction when needed and clamp down and absorb when high voltage protection is need. they also change the electron path and force it to cancel itself out in the solenoid windings. its a little more complicated technially than that but you can google for more info.

Hope this helps anyone having problems. this will deal with most solenoid induced transbreak issues, as well as bad logs, or an ecu that acts funny.

(ps, this isnt needed on the low voltage side of the ignition coils. the flyback voltage from those is already dealt with inside the ecu, and im not sure that trevor hasnt done the same inside the max for the nitrous and fuel, im not using one so i wouldnt know)


edit... and a little more info

http://www.semtech.com/images/promo/Wha ... Diodes.pdf

http://www.littelfuse.com/tvs-diode.html

the problem usuually doesnt occur with pulsoids.. its generally trans-brake and air shifter induced. (ie, larger solenoids that have time for total magnetic field collaspe) I have had the problem on a couple bikes now. on one the air shifter was causing interference in the nitrous controller causing it to lose its ignition signal and stop spraying. then it would start again a second later.

Very interesting post. Perhaps a little bit above my understanding of electronics etc but are you saying the collapse of the magnetic field induces a high voltage spike in the solenoid windings?
If so, does this apply to only high power solenoids? Though an ignition kill solenoid wouldnt be that powerfull i'd guess? Fortunately the symptons you give there are different to what im suffering.
Do these diodes have to be fitted at source? Or could a single diode be used close to destination?
I have a small quantity of generic relays on the bike controlling various things which are generally either on or off. Are these likely to cause me issues compared to proximity of wiring to high energy coils?
Sorry for the 101 questions lol
Cheers
Steve

what he said. lol..

it is best to put the diode as close to the coil as possible. the diode absorbs quite alot of the charge but its my understanding that it also routes some back to the coil. and it was also stated that if the diode is a long ways away then the wire will build up magnetic field as well and intensify the effect.

OK cool.... So if i put this into radio terms as i'd understand it from my early interest in CB radios and the like (Yeah i know... SAD!!! Lol) the power feed if looked at on an oscilloscope would be like an FM carrier wave with the interference modulated on to it?
If that is the case, i also remeber how ineffective hi and low pass filters were in the day.

Also, if i remember correctly, from my school days and physics in particular, electricity in the real world flows from negative to positive, which would make sense of why earthing to the frame rather than the battery works.

So, in my instance, if moving the earth to the frame doesnt work either entirely or not at all, assuming the cause of my problems is the cause, is there something i could wrap the harness in to shield the wires from inductive interference? Would say something as simple as two or 3 layers of tin foil have any effect if earthed at both ends or would that cause further inductance?

Am thinking an oscilloscope would be a usefull thing to have right now, but dont have access to one, but think it would probably shed some light on to cause of interference.

Again, sorry for all the questions
Cheers
Steve

nothing wrong with questions. thats how we all learn and move the game forward.

Im not 150% sure that im entirely accurate, but this is how i understand it so far. im still learning on this subject so bare with me. so far i have found the best results making all the solenoids "power switched" instead of "ground switched" the back emf only happens when the magnetic field around the coil collaspes. that can only happen when the current stops flowing. if the current stops flowing then obviously you have broken the circuit. (via a switch) MOST of the time people make things ground switched, so the side of the circuit that is open back to the source is the power side. (through any electronics or relays it used to get there in the first place) there is only 1 positive potential on the bike and thats the main source for all the electronics so we DONT want to use that. (there is actually 2, but its routed to the battery) By making it power switched you make the path back to the source on the ground side. and there is MANY MANY paths back to ground. with many large "capacitors" along the way (engine block, frame, tires, etc)

Additionally, the best reason to use the ground side is because of the way a alternator or stator works. you have large sine wave, from positive to negative potential and back again. (x3) what this means is that the largest negative potential on the bike is NOT at the negative battery terminal, its actually at the stator housing. (or as close to you can get to it.) that means that this spot in the grand scheme of things can absorb a lot of current very rapidly, making for a good capacitor.

now, we have put a lot of voltage spikes (interference) on the engine block, so we don't want to use that as our reference for digital ground. since its going to be changing potential a lot, we need somewhere cleaner and more steady. so for digital ground, its best to use a ground far away from that, or directly at the battery. if its done right then you will have perfectly clean traces on your data log. also, if your datalogger has a different reference (ground) voltage, than your ecu and sensors do, then your data log will be skewed. for this reason, i tie my datalog ground ( digital reference, NOT the power ground) directly into the ground wire coming off of the TPS circuit BEFORE it goes through the ecu. that ensure that my datalogger and sensors all have the same amount of current flow, and will read identical with no oscillation. and by keeping back emf tied to the engine block ALL of our electronics have clean steady power..


..now.. all that said.. you can just use the diode and not worry about it LOL. some controllers force you to use a ground side switch on solenoids, so in this case you don't really have a choice and all you can do to prevent back emf is use the diode, or use some wiring trickery to switch both sides at the same time. but this locks flyback inside the coil and can cause it to over heat. not to mention its complicated to wire.

anyways.. thats the best grasp i have of the way it all works right now, and so far ive been lucky enough to be able to rid all interference problems.

btw.. if you REALLY want to get into how all the ground paths, and emf can ruin your electronics and logs, go to a stereo forum. those guys can tell you anything you need to know. if you have every heard the feed back in a speaker system, that is caused by improper wiring and interference. so those guys have a huge need to get it right, becasue you can actually hear the issues. and large sub woofers are just like a nitrous solenoid. it causes the same problems.


you know.. while we are on this subject.. the "names" of the termials really should be reversed. LOL if you think about it, the positive side has less electrons than the negative side. thats what makes it positive by our current labeling standards. if you have -5v and -50v each on one end of the wire then the -5v is the positive by current labeling. even though its still a negative voltage! LOL. the negative side of the battery has more electrons to give away which makes it the negative by labels but is more positive in number of electrons.. which would mean in our example that; by number of electrons; -50 is the positive and the -5 is the negative, which would give way to the conventional wisdom that high pressure moves to low pressure. which is the norm in air flows, water flows, etc.. so why not in electricity? head hurt?

Again, Thanks guys, sorta got my head round it, well as far as i will without actually seeing it by means of oscilloscope.

At present i still think my issues are caused by the coils and possible inductance, though i may of course be proved wrong on that front yet. Just based on the principle that while sitting in the pits, even with the engine running, it all works. As soon as engine is under load it doesnt. As we know, this will be when spark voltage is at max and any magnetic fields will be at their strongest. The only other possible i havent been able to rule out, mainly because the max ceases functioning at all, is the supply voltage to the max when everything else is working at max effort, as the max doesnt log the voltage, or anything else, after a run all logs read 0.

That aside, this is a very interesting subject even if it is very technical/complicated. So again, thanks for the efforts to explain it in understandable terms

Steve

This is the bit i remember from school days. As it was explained at the time, when it was first discovered about the flow of electricity, movement of charged ions etc. There were already so many rules such as, is it the left hand rule of thumb that determines north pole on an electro magnet, where the thumb indicates magnetic north if the fingers are wrapped around the coil in direction of flow, flow being positive to negative? Apperently it would have screwed up so many such laws that it was easier to keep as it was

Just as a follow up to this, have ben looking at the small handheld oscilloscopes now available on ebay from £40 upwards. Has anyone ever tried one of these? I would imagine they are pretty basic but would they be ok to solve interference issues rather than spending a grand on a fluke? I know ya get what ya pay for, but i cant justify that sort of outlay for a problem on a single bike then sit it on the shelf for the rest of eternity, whereas £40-75 i can justify

Cheers
Steve

We have one that cost about £200 a few years back, so it would probably be less than half that price now and it does just fine, so I'd expect the £40 job to be adequate.