Coil & Ballast Questions - Clarity Sought!
Discussion
Hullo all.
Please scroll down to *** below if you're not interested in reading so much text.
Been a PH member for many years now, but since owning my first Chimaera I've been using the search function to find answers to almost every question I've had. So thank you all current and past members for creating this treasure trove of TVR goodness
I've tried to search on this topic with little success so far, so apologies if this has been answered before and I have just failed to locate it.
Basically my car (1999 Chim 400) was parked up for a long period in its life and so I'm working through replacing all the relevant bits and pieces.
Right now I'm tackling the ignition system. The car generally runs okay; fairly smooth, idles well, doesn't get hot or lumpy etc. But I do think it may be slightly underpowered for a low mileage engine (36k). I have a fair bit of history and receipts for the car, but nothing from the last decade or longer for the ignition system. So I'm going to refresh it all.
Bit of context for you there!
Easy, eh? No.
Firstly the genuine Bosch coils are hens teeth nowadays, but I'd read a lot of good stuffs about the Viper coils, so I bought the 3ohm (VCS) model from Powerspark based on some info I found here.
Before fitting anything I tested the resistance on my existing coil just to be sure, and discovered the one on the car is a 'high power' coil, approx 0.7ohms resistance when measuring between the two poles on the coil.
That was unexpected so I thought I'd test to see if there's a ballast on the circuit anywhere as per the Powerspark guide (https://blog.simonbbc.com/ballast-resistors-resistance-and-coils/) and found that yes I do seem to have a ballast somewhere, albeit not immediately obvious where.
So this conflicts with any info I've seen so far, I had understood the cars had a standard 3ohm coil and none were ever fitted with ballasts.
I cannot see a ballast anywhere on the car.
I was hoping somebody knows a little about this and may be able to advise on what the standard setup should be here so I can return the car to that form. Or, if sensible mods are recommended I'm happy for that too
I spoke to Powerspark who are extremely helpful. They said that under no circumstances should there ever be both a high energy 0.7ohm coil AND a ballast on the same circuit. That makes sense, but I'm confused why anyone would ever had made these changes to the car, it doesn't make sense to me.
I found this in the loom right near the coil that may be a resistor of some sort, wondering if this normal to anyone?
I'm going to go unravel the loom a little bit now to dig further.
Sorry for the long post, just wanted to add a bit of background as I know therrell likely be questions about it and why I'm looking into it.
Appreciate you all. Take it easy.
Matt
Please scroll down to *** below if you're not interested in reading so much text.
Been a PH member for many years now, but since owning my first Chimaera I've been using the search function to find answers to almost every question I've had. So thank you all current and past members for creating this treasure trove of TVR goodness
I've tried to search on this topic with little success so far, so apologies if this has been answered before and I have just failed to locate it.
Basically my car (1999 Chim 400) was parked up for a long period in its life and so I'm working through replacing all the relevant bits and pieces.
Right now I'm tackling the ignition system. The car generally runs okay; fairly smooth, idles well, doesn't get hot or lumpy etc. But I do think it may be slightly underpowered for a low mileage engine (36k). I have a fair bit of history and receipts for the car, but nothing from the last decade or longer for the ignition system. So I'm going to refresh it all.
Bit of context for you there!
- *****
Easy, eh? No.
Firstly the genuine Bosch coils are hens teeth nowadays, but I'd read a lot of good stuffs about the Viper coils, so I bought the 3ohm (VCS) model from Powerspark based on some info I found here.
Before fitting anything I tested the resistance on my existing coil just to be sure, and discovered the one on the car is a 'high power' coil, approx 0.7ohms resistance when measuring between the two poles on the coil.
That was unexpected so I thought I'd test to see if there's a ballast on the circuit anywhere as per the Powerspark guide (https://blog.simonbbc.com/ballast-resistors-resistance-and-coils/) and found that yes I do seem to have a ballast somewhere, albeit not immediately obvious where.
So this conflicts with any info I've seen so far, I had understood the cars had a standard 3ohm coil and none were ever fitted with ballasts.
I cannot see a ballast anywhere on the car.
I was hoping somebody knows a little about this and may be able to advise on what the standard setup should be here so I can return the car to that form. Or, if sensible mods are recommended I'm happy for that too
I spoke to Powerspark who are extremely helpful. They said that under no circumstances should there ever be both a high energy 0.7ohm coil AND a ballast on the same circuit. That makes sense, but I'm confused why anyone would ever had made these changes to the car, it doesn't make sense to me.
I found this in the loom right near the coil that may be a resistor of some sort, wondering if this normal to anyone?
I'm going to go unravel the loom a little bit now to dig further.
Sorry for the long post, just wanted to add a bit of background as I know therrell likely be questions about it and why I'm looking into it.
Appreciate you all. Take it easy.
Matt
Edited by MattMe on Saturday 25th February 15:44
That photo I posted above appears to be the 'tune sensor' resistor as described here : https://forums.lr4x4.com/topic/66999-lucas-rd-9530...
And looks like this on my car (I've cleaned the terminals already)
I've not been able to locate a ballast resistor anywhere so I'm currently completely stumped as to why the voltage test I have done indicated that there is.
12v on the terminals on the coil with ignition on, connect negative to ground and I get around 7v. I believe even with a ballast resistor this reading should be more like 10v.
This is bugging me!
And looks like this on my car (I've cleaned the terminals already)
I've not been able to locate a ballast resistor anywhere so I'm currently completely stumped as to why the voltage test I have done indicated that there is.
12v on the terminals on the coil with ignition on, connect negative to ground and I get around 7v. I believe even with a ballast resistor this reading should be more like 10v.
This is bugging me!
If i remember correctly a ballast resistor is there to drop the current when the car is running and when starting the resistor is bypassed to maximise the current and therefore generate a bigger spark. I may be wrong as its about a million years since I had a car with one. Therefore you may be seeing voltage with the resistor bypassed
As standard there is no ballast resistor on the Tvr ignition system
Those resistors you found are for ecu protection and rev counter too.
I'd look for a replacement bosch coil which are readily available with a quick search.
Ignition systems need to be tip top on these cars, I'd leave the powerspark coils well alone personally.
I believe this is the correct coil but please check the part number.
https://www.ebay.co.uk/itm/165754647215?mkcid=16&a...
Those resistors you found are for ecu protection and rev counter too.
I'd look for a replacement bosch coil which are readily available with a quick search.
Ignition systems need to be tip top on these cars, I'd leave the powerspark coils well alone personally.
I believe this is the correct coil but please check the part number.
https://www.ebay.co.uk/itm/165754647215?mkcid=16&a...
Edited by Belle427 on Saturday 25th February 17:17
Thanks, Belle427.
Appreciate your input.
Indeed, following my initial post I had dug around a little more and found similar information regarding those resistors.Cleaned up and taped up to be left alone agian
Any thoughts on why, if there's no ballast on the car, why the voltage test seems to indicate there is a ballast somewhere?
If someone wouldn't mind check their coil resistance and completing teh same ballast test I'd really appreciate it...
Any reason for advising to avoid the Powerspark coils, Belle427? I'd seen several TVR owners on here reporting good things about them.
Appreciate your input.
Indeed, following my initial post I had dug around a little more and found similar information regarding those resistors.Cleaned up and taped up to be left alone agian
Any thoughts on why, if there's no ballast on the car, why the voltage test seems to indicate there is a ballast somewhere?
If someone wouldn't mind check their coil resistance and completing teh same ballast test I'd really appreciate it...
Any reason for advising to avoid the Powerspark coils, Belle427? I'd seen several TVR owners on here reporting good things about them.
Something that stands out to me as a possible cause is.....
Current = voltage ÷ by resistance
Engine stationary = voltage approx 12 volts
12 volts ÷ 0.7 ohms = 17.143 Amps when completing the coil circuit by momentarily connecting coil negative terminal to earth (all vehicle wiring disconnected from coil negative before doing so)
Engine running, alternator charging = voltage approx 14 volts
14 volts ÷ 0.7 ohms = 20 Amps each time the ignition module applies a negative to the coil negative terminal
The above tells us that there is a 20 Amps current draw throughout the whole coil primary circuit
As far as I'm aware the Chimaera ignition supply cable to the coil positive terminal isn't heavy enough to carry 20 Amps and the same goes for the negative cable from coil negative to the ignition module
Ignore the above if your vehicles primary circuit wiring has been up-rated
If your vehicles primary circuit is wired with 8.5 Amp max cable there will be a big voltage drop along its length when 20 Amps is drawn through it
Current = voltage ÷ by resistance
Engine stationary = voltage approx 12 volts
12 volts ÷ 0.7 ohms = 17.143 Amps when completing the coil circuit by momentarily connecting coil negative terminal to earth (all vehicle wiring disconnected from coil negative before doing so)
Engine running, alternator charging = voltage approx 14 volts
14 volts ÷ 0.7 ohms = 20 Amps each time the ignition module applies a negative to the coil negative terminal
The above tells us that there is a 20 Amps current draw throughout the whole coil primary circuit
As far as I'm aware the Chimaera ignition supply cable to the coil positive terminal isn't heavy enough to carry 20 Amps and the same goes for the negative cable from coil negative to the ignition module
Ignore the above if your vehicles primary circuit wiring has been up-rated
If your vehicles primary circuit is wired with 8.5 Amp max cable there will be a big voltage drop along its length when 20 Amps is drawn through it
MattMe said:
Thanks, Belle427.
Appreciate your input.
Indeed, following my initial post I had dug around a little more and found similar information regarding those resistors.Cleaned up and taped up to be left alone agian
Any thoughts on why, if there's no ballast on the car, why the voltage test seems to indicate there is a ballast somewhere?
If someone wouldn't mind check their coil resistance and completing teh same ballast test I'd really appreciate it...
Any reason for advising to avoid the Powerspark coils, Belle427? I'd seen several TVR owners on here reporting good things about them.
Just not a fan of cheap coils but nothing against them really.Appreciate your input.
Indeed, following my initial post I had dug around a little more and found similar information regarding those resistors.Cleaned up and taped up to be left alone agian
Any thoughts on why, if there's no ballast on the car, why the voltage test seems to indicate there is a ballast somewhere?
If someone wouldn't mind check their coil resistance and completing teh same ballast test I'd really appreciate it...
Any reason for advising to avoid the Powerspark coils, Belle427? I'd seen several TVR owners on here reporting good things about them.
If you test at coil positive and the other lead to a good ground you should see 12 volts ignition on, this Is all you need to concentrate on.
Testing at coil negative may be confusing you.
Yes, sorry for not replying to your original post.
It seems like you're insinuating I've measured something incorrectly? That might be the case, I'll have another look and post pictures to confirm.
Or is there something else I'm missing here? Your last message seems a little vague.
It seems like you're insinuating I've measured something incorrectly? That might be the case, I'll have another look and post pictures to confirm.
Or is there something else I'm missing here? Your last message seems a little vague.
Edited by MattMe on Monday 27th February 01:13
Just seems like if you feel that way you could just say that I might have measured something wrong and offer some advice rather than whatever this is.
Thanks anyway.
I'll check again when I replace the coil later this week.
I'm curious as to what the resistance is of a standard coil, I've not found that anywhere on the forum or on any Bosch listings.
Thanks anyway.
I'll check again when I replace the coil later this week.
I'm curious as to what the resistance is of a standard coil, I've not found that anywhere on the forum or on any Bosch listings.
MattMe said:
Just seems like if you feel that way you could just say that I might have measured something wrong and offer some advice rather than whatever this is.
This is nothing other than Ohms lawI dont understand your comments, a 0.7 Ohm primary resistance coil will draw 20 Amps at 14 volts
After all, you did ask and I answered with a good explanation
Am I allowed to ask why you question Ohms law? Ohms law doesnt play games, its very accurate
my apologies I have a feeling that you havent understood my above calculation due to my possible bad explanationwill attempt to keep this simple If a vehicles wiring harness is designed correctly it will be able to power all electrical components without any problemsonce any component is upgraded, its circuits wiring may well need to be upgraded to supply it with enough voltage to function correctly
Bringing it back on topic, that as ever Polly is off on one! ...OP, perhaps you and others are confusing 'ballasts'... http://www.vintagemodelairplane.com/pages/Rover_Te... A@
Edited by Adrian@ on Monday 27th February 07:49
MattMe said:
I've not been able to locate a ballast resistor anywhere so I'm currently completely stumped as to why the voltage test I have done indicated that there is.
12v on the terminals on the coil with ignition on, connect negative to ground and I get around 7v. I believe even with a ballast resistor this reading should be more like 10v.
This is bugging me!
12v on the terminals on the coil with ignition on, connect negative to ground and I get around 7v. I believe even with a ballast resistor this reading should be more like 10v.
This is bugging me!
Polly Grigora said:
Something that stands out to me as a possible cause is.....
Current = voltage ÷ by resistance
Engine stationary = voltage approx 12 volts
12 volts ÷ 0.7 ohms = 17.143 Amps when completing the coil circuit by momentarily connecting coil negative terminal to earth (all vehicle wiring disconnected from coil negative before doing so)
Engine running, alternator charging = voltage approx 14 volts
14 volts ÷ 0.7 ohms = 20 Amps each time the ignition module applies a negative to the coil negative terminal
The above tells us that there is a 20 Amps current draw throughout the whole coil primary circuit
As far as I'm aware the Chimaera ignition supply cable to the coil positive terminal isn't heavy enough to carry 20 Amps and the same goes for the negative cable from coil negative to the ignition module
Ignore the above if your vehicles primary circuit wiring has been up-rated
If your vehicles primary circuit is wired with 8.5 Amp max cable there will be a big voltage drop along its length when 20 Amps is drawn through it
Current = voltage ÷ by resistance
Engine stationary = voltage approx 12 volts
12 volts ÷ 0.7 ohms = 17.143 Amps when completing the coil circuit by momentarily connecting coil negative terminal to earth (all vehicle wiring disconnected from coil negative before doing so)
Engine running, alternator charging = voltage approx 14 volts
14 volts ÷ 0.7 ohms = 20 Amps each time the ignition module applies a negative to the coil negative terminal
The above tells us that there is a 20 Amps current draw throughout the whole coil primary circuit
As far as I'm aware the Chimaera ignition supply cable to the coil positive terminal isn't heavy enough to carry 20 Amps and the same goes for the negative cable from coil negative to the ignition module
Ignore the above if your vehicles primary circuit wiring has been up-rated
If your vehicles primary circuit is wired with 8.5 Amp max cable there will be a big voltage drop along its length when 20 Amps is drawn through it
Adrian@ said:
Bringing it back on topic, that as ever Polly is off on one! ...OP, perhaps you and others are confusing 'ballasts'... http://www.vintagemodelairplane.com/pages/Rover_Te... A@
My above input to this topic does explain how 7 volts rather than battery voltage could be present at the coil positive terminalPolly Grigora said:
My above input to this topic does explain how 7 volts rather than battery voltage could be present at the coil positive terminal
What it does/did was added dramatic effect for no good reason...the OP's car runs as OE (with a non ballast'ed coil), others read 'ballast' and read it as a ballast for the coil (my link explains the issues). IMHO these resistors are robust enough to be cleaned (I would clean and paint the ends before refitting) and re terminated with the 100% correct crimped and soldered joints (the black covers can be reused, the correct tang'ed version of the Lucas connector can be purchased so the job is 100%). Lucas FBD943 is the Lucas number..if you can find them. A@PS the tune resistor is down in the foot well.
Edited by Adrian@ on Monday 27th February 13:13
Adrian@ said:
Bringing it back on topic, that as ever Polly is off on one! ...OP, perhaps you and others are confusing 'ballasts'... http://www.vintagemodelairplane.com/pages/Rover_Te... A@
That link doesn't appear to work?Edited by Adrian@ on Monday 27th February 07:49
MattMe said:
That link doesn't appear to work?
from the page...ignore the location as you have a TVR...One of the simplest components in the Rover SD1 Fuel Injection System is a common resistor measuring 6800 ohms or 6.8k ohm. It is a sturdy item encapsulated in resin with 1/4" spade connectors because Rover decided to fit it inline with a single connection from the coil to the ECU mounted virtually in free air alongside the air flow meter.
This trigger resistor is connected in the line between the negative side of the coil to pin No 1 of the Electronic Control Unit (ECU) and by virtue of the pulsing signal on the negative side of the coil informs the ECU that the engine is running. Its purpose is two-fold.
1 As a voltage drop input component to ensure the ECU receives the correct level of input voltage.
2 Protect the ECU from any excess induced voltage that might otherwise occur at the ignition coil.
Interestingly, it appears to have picked up three different descriptive titles depending upon which Rover document one reads. Over time, it has been variously referred to as either a Trigger, Ballast or Inline Resistor.
The word "Ballast" is most misleading as that is usually a term used for a resistor employed to reduce the operating voltage at an ignition coil. The word "Trigger" is a slight misnomer in that it implies some sort of active function which it does not possess. Thus the word "Inline" appears to best describe its use and function. But then, 20 odd years after all the books have been written, it is anybodies guess as to what the designer of the system really had in mind.
One thing for sure, is that the component was almost certainly included for the purpose of protection and it would be unwise to omit it.
Edited by Adrian@ on Monday 27th February 13:23
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