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missing component

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dendenceffy

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hi all new to this forum,
currently m working on building my own ignition rev limiter in my rb20de skyline.
ive just recently put a kill switch in to kill the power to the coil pack, which means the car still turns over but it wont start untill the switch has be activated.
anyway back to the limiter. ive found out that there is supply voltage going straight to the coil pack and it stays the same throughtout the revs. my ca is equipt from factory with a fuel cut which is not so good for the engine, the fuel cut limits at 8100 rpm which is fine cause i never on purpose go that high, i want to install a ignition rev limiter at either 7000 or 7500 rpm. i went and recorded the current going through the main power feed to the coil pack and at idle it was about 0.4 A, at 7000 rpm there was 1.75 A, at 7500 rpm there was 1.86 A, i then went to find out exactly how high my fuel cut limiter (8100 rpm) was and it blew the 2 A fuse in my multimeter :/. anyway im looking for a compnent that will limit the current flow but wont effect the voltage as i need a good steady voltage to ensure a good, strong and consistant spark from the spark plug.. preferbly i would like some thing that could direct the excess current to say a LED so i know when im sitting on the limiter. im trying to create a cheap solution for one of these.. https://www.youtube.com/watch?v=PE4wtsMjHTA&feature=related

any help would be greatly appreciated :) cheers guys
 
would a transistor work? also i thought using a resistor would be a bad idea as overtime it would lose its reistance etc
 
i went and recorded the current going through the main power feed to the coil pack
Is that an average current (bearing in mind that ignition coils are pulsed and their peak currents are much higher than their average current) ?
 
You're going totally the wrong way about doing this - you don't want to limit the current, you want to stop the coil from firing altogether. The other problem with doing it this way is that if the car is still fuelling, you could potentially end up with a buildup of unburnt fuel in the cylinders / exhaust / cat which could ignite when your revs come back down leading to a fair bit of coughing and spluttering (and possibly blowing your catalytic converter innards out !)

You're best off going for an off the shelf rev limiter if your knowledge of electronics is at a basic level - by the time you've reinvented the wheel it would probably be cheaper for you as well.

Any particular reason you don't want to cut the fuel ?
 
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You're going totally the wrong way about doing this - you don't want to limit the current, you want to stop the coil from firing altogether. The other problem with doing it this way is that if the car is still fuelling, you could potentially end up with a buildup of unburnt fuel in the cylinders / exhaust / cat which could ignite when your revs come back down leading to a fair bit of coughing and spluttering (and possibly blowing your catalytic converter innards out !)

You're best off going for an off the shelf rev limiter if your knowledge of electronics is at a basic level - by the time you've reinvented the wheel it would probably be cheaper for you as well.

Any particular reason you don't want to cut the fuel ?

tbh i couldnt give to fucks about the cat, as i will be removing it soon, cutting the fuel isnt good because it starves the engine, so letting the fuel go straight through is better for it and sounds better to but thats not why im doing it. stoping the current at a certain point will rev cut as the coils cant get the ignition from the coil pack fast enough effectivly limiting there speed. thansk for the imput though :)
 
Is that an average current (bearing in mind that ignition coils are pulsed and their peak currents are much higher than their average current) ?

hmm good question.. im not really sure, where i plan to put this device is inbetween the relay and coil pack.. thanks :)
 
the current would be increasing throughout the revs until 1.75A to 1.86A then i want to limit it there so it will limit the revs effectively, also i need to keep at v at what there are at which is about 12.6 v +. i would like something that would expel the excess current into a parrellel circuit so it also has 12.6 v + to light up an LED or something similar so i know when the limiter is active. cheers guys
 
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I suggest you get a scope on the live wire with a current shunt and watch the waveform rather than assuming the current is directly proportional to the revs. You'll see some massive peaks and strange waveforms as the coil charges and revs change.

Where have you seen the information that limiting the current to the coil will act as a rev limiter or is this based on some basic tests with a multimeter ?

I assume you don't like using the fuel cut method as your engine may start to run lean at high revs ?


I've been running a business desiging bespoke car electronic systems for the past ten years and haven't come across any method like this in the past. We've put in current limiting in the form of a chopper circuit on lower impedance coils so they can charge faster from a higher voltage source than they were designed for without overheating but I see absolutely no way of this working reliably for a rev limiter application.


Have a read through this document and have a look at how it all works - it may be a little more complicated than you think : https://www.electro-tech-online.com/custompdfs/2011/11/052005_04.pdf
 
I second what Picbits is saying.
 
I suggest you get a scope on the live wire with a current shunt and watch the waveform rather than assuming the current is directly proportional to the revs. You'll see some massive peaks and strange waveforms as the coil charges and revs change.

Where have you seen the information that limiting the current to the coil will act as a rev limiter or is this based on some basic tests with a multimeter ?

I assume you don't like using the fuel cut method as your engine may start to run lean at high revs ?


I've been running a business desiging bespoke car electronic systems for the past ten years and haven't come across any method like this in the past. We've put in current limiting in the form of a chopper circuit on lower impedance coils so they can charge faster from a higher voltage source than they were designed for without overheating but I see absolutely no way of this working reliably for a rev limiter application.


Have a read through this document and have a look at how it all works - it may be a little more complicated than you think : https://www.electro-tech-online.com/custompdfs/2011/11/052005_04-1.pdf

im assuming that its not averaging itself as when i had the multimeter on it, it didnt blow the 2 A fuse untill i went to see were the stock limiter actauly was. its before the coil were the ignitor is, so its not gtting a pulse till after the ignitor i think.
 
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