Stepper motor and low value on Roverguage
Discussion
Tweaking and fiddling mode still on.
Roverguage shows my car idling at around 950 rpm but it also says that the stepper motor is at 19-20% at idle. This is at fan cycling temps.
All other values are in range, short term cycling around 0 but mostly negative and long term sitting at around - 45% / - 25%.
Ignition on only, stepper is at around 99%.
The throttle though starts at 1% and not 2%, but literally grazing the butterfly lever brings it to 2, although not sure how that is adjusted with the screw stop under the plenum.
As the target range for the stepper is supposed to be 30-50%, why would mine be lower?
Blipping the stepper from within rovergauge opens it and it settles back to 20% again.
Checked and set base idle at around 600-650rpm.
Roverguage shows my car idling at around 950 rpm but it also says that the stepper motor is at 19-20% at idle. This is at fan cycling temps.
All other values are in range, short term cycling around 0 but mostly negative and long term sitting at around - 45% / - 25%.
Ignition on only, stepper is at around 99%.
The throttle though starts at 1% and not 2%, but literally grazing the butterfly lever brings it to 2, although not sure how that is adjusted with the screw stop under the plenum.
As the target range for the stepper is supposed to be 30-50%, why would mine be lower?
Blipping the stepper from within rovergauge opens it and it settles back to 20% again.
Checked and set base idle at around 600-650rpm.
Edited by jazzdude on Sunday 15th April 10:30
Edited by jazzdude on Sunday 15th April 10:41
jazzdude said:
stepper motor is at 19-20% at idle
You're only in trouble if it hits 0% and your 20% safely margin sounds good to me, 20% is not an issue.jazzdude said:
The throttle though starts at 1% and not 2%
ABSOLUTE throttle can be anything between 1% and 8% but more importantly CORRECTED throttle should automatically adjust down to zero.
Wide Open Throttle should be more than
84% for TVR chips and
91% for Land Rover chips to force open loop below 3,400rpm and applies extra full throttle fuel.
What's your "Checksum Fixer" in RoverGauge because recently I've discovered there are two different Chimmy 400 chips.
You asked me that before Steve, I looked for it and am not sure where the 'Checksum Fixer' is to tell you.
When I pulled the original eprom out a couple of years ago it was stiff and one of the little legs snapped off. So I no longer can fit the original eprom to see what map it had.
I have been using the map I got from you that I told you about in that other thread.
I was going to load the latest map you sent me a few weeks ago this weekend but decided to run the white tune on this map for a couple more tanks first just to satisfy myself that all is well before switching over.
Even though it's running well Steve, the idle is still a little lumpy and I want to get hold of a good dizzy with 20 deg mechanical advance on it to try out full manifold vacuum, just out of curiosity, to see how that works on both tunes.
I've asked Powersparks but was told that the advance curve on theirs is 'fine' for a tvr, meaning it could be a 16 deg again. Sending it on to the Distributor Doctor would be better but it means a month off road again which I don't want to do.
Someone will come along and say leave it as it is but this vacuum thing is an itch I want to scratch.
When I pulled the original eprom out a couple of years ago it was stiff and one of the little legs snapped off. So I no longer can fit the original eprom to see what map it had.
I have been using the map I got from you that I told you about in that other thread.
I was going to load the latest map you sent me a few weeks ago this weekend but decided to run the white tune on this map for a couple more tanks first just to satisfy myself that all is well before switching over.
Even though it's running well Steve, the idle is still a little lumpy and I want to get hold of a good dizzy with 20 deg mechanical advance on it to try out full manifold vacuum, just out of curiosity, to see how that works on both tunes.
I've asked Powersparks but was told that the advance curve on theirs is 'fine' for a tvr, meaning it could be a 16 deg again. Sending it on to the Distributor Doctor would be better but it means a month off road again which I don't want to do.
Someone will come along and say leave it as it is but this vacuum thing is an itch I want to scratch.
stevesprint said:
ABSOLUTE throttle can be anything between 1% and 8% but more importantly
CORRECTED throttle should automatically adjust down to zero.
Wide Open Throttle should be more than
84% for TVR chips and
91% for Land Rover chips to force open loop below 3,400rpm and applies extra full throttle fuel.
What's your "Checksum Fixer" in RoverGauge because recently I've discovered there are two different Chimmy 400 chips.
My rovergauge documents state that the 14CUX 'absolute TPS reading' for the ECU to drop into 'idle mode' is 2% to 10% (and road speed sensor at less than 3mph), anything under 2% gives a fault signal. CORRECTED throttle should automatically adjust down to zero.
Wide Open Throttle should be more than
84% for TVR chips and
91% for Land Rover chips to force open loop below 3,400rpm and applies extra full throttle fuel.
What's your "Checksum Fixer" in RoverGauge because recently I've discovered there are two different Chimmy 400 chips.
bobfather said:
My rovergauge documents state that the 14CUX 'absolute TPS reading' for the ECU to drop into 'idle mode' is 2% to 10% (and road speed sensor at less than 3mph), anything under 2% gives a fault signal.
Which is why I thought is was strange as it is not throwing up a fault.The car starts at around 1200 rpm. and within seconds the stepper pulls it down to 950 rpm and it stays there. It seems the stepper is working perfectly, it is just not 'within range' as the RG documents state.
I recommend putting the laptop away and returning to the basics, if your distributor isn't advancing correctly start there rather than staring into a screen foolishly hoping you'll solve such mechanical issues with a few key strokes, because you won't 
.
Once the distributor issue is fixed and to be clear, you will definitely find the engine idles better and smoother if you run 18 degrees at idle rather than the 10-12 a standard Chimaera runs at, you will also notice a significant reduction in exhaust manifold temps, as clearly documented elsewhere the easiest and safest way to increase your idle timing is switch the vac advance unit from ported vacuum to a full vacuum signal. Be aware though, running more timing at idle will have a negative impact on emissions but the truth is a happy Rover V8 is never going to be a clean one simply because the engine design is ancient and was never intended to run at 14.7:1 AFR and 10-12 degrees timing.
Make no mistake while 14.7:1 is stoich it is also way too lean for a nice smooth idle on the ancient Rover V8, 14.7:1 and 10-12 of ignition timing are both strategies that only exist in a bid to make a dirty old engine design meet ever stricter emissions targets and work with the restrictive catalytic converters used. Bin your cats, switch to manifold vacuum to run 18 degrees at idle then run a fuel calibration that shoots for 13.3:1 and she'll purr like a kitten.
Even with all that and the distributor issue resolved your old Rover V8 is never going to be as smooth as one benefiting from a distributorless ignition system, especially one that runs scatter spark, but the above strategies will definitely give you a more stable idle. Just be sure to correct your base idle setting accordingly as adding 6-8 degrees at idle will inevitably increase your idle speed by as much as 200-300rpm. Actually this increase in idle speed is the engine telling you it's happier with the increase in timing, what its saying to you is by initiating combustion earlier you've achieved a more complete burn of the fuel, and so more torque is being produced.
Back in the day and without the benefit of a strobe this how we set ignition timing, along with the 'run it to det, then retard it a fraction' method which I do not recommend. The process was simple and just required a good ear, rotate the distributor at idle advancing the timing while listening for the rise in engine speed, at the point the idle speed stops climbing you should then retard by 2 degrees.
This ghetto timing method worked perfectly for years, a good experienced mechanic back in the day would have a highly developed ear for such things, once he'd set the idle timing using this method he would test drive the car usually on his favored hill. Timing would be advanced until the onset of what we used to call pinking, at which point the distributor would be retarded by two degrees and the process repeated until there was no audible sign of detonation under load climbing that hill.
On the subject of stepper motors and the like my point would be while extra air valves can be helpful during cold start and to save a stall, generally I'm not a huge fan of idle air control valves be them of the old stepper variety or the more modern Bosch two wire rotary type I have on my Canems system. However, I must say the rotary type has the potential (if properly managed) to offer much better control than a Lucas stepper motor, and by a considerable margin.
People should be under no illusion, any air bleed, even an intentional ECU managed air bleed is still an induction leak, fact!, and all induction leaks intentional or otherwise tend to be enemy of achieving a smooth running engine. It stands to reason any air being introduced must be accompanied by additional fuel if a stable AFR is to be achieved, essentially as the stepper motor opens and closes it then boils down to how quickly the ECU can respond, which in the case of the lurching rich/lean narrow band lambda equipped ancient 14CUX processor..... isn't very fast at all
.
It's also well understood that to achieve the very best throttle response you want 100% of the air you're allowing into the engine to pass via the throttle butterfly and nowhere else, this is because the throttle butterfly is the giant air valve you are directly controlling with your foot. Throttle response is all about translating the instruction your brain tells you foot to respond to, and how quickly and directly that instruction translates into an increase in engine speed.
With all the above in mind it doesn't take a genius to understand why Power's Performance MBE system doesn't even have an idle air control valve, their system exclusively uses ECU managed ignition timing to maintain the target idle speed which in 90% of all situations is in my humble opinion a significantly better idea than trying to control idle speed by allowing a bleed of air around the very system the driver himself uses to control engine speed, IE the throttle butterfly.
If you switch from the emission based ported vacuum to full manifold vacuum to achieve 18 degrees at idle the more stable idle it delivers will ensure less interference from the stepper motor will be required, and with idle air control valves less air bleed is always better. To be honest you may even find with the exception of the first 60-120 seconds of cold start you don't even need that stepper motor at all, this would be especially true for a car with no power steering and or air con and if you set your idle speed 100rpm higher than the 950rpm a Chimaera typically idles at once warm.
Completely removing the stepper motor has it's disadvantages of course and is generally not recommended especially if you do have power steering and or air con fitted, however as an experiment and assuming you don't mind keeping your foot on the throttle for the first minute or so of cold start, removing or at least limiting the stepper motor activity/interference should yield benefits... especially in the area of low speed drivability.
If you do have power steering and air con, with your timing set at 18 degrees at idle you may still find it's advantageous to limit the air bleed by virtue of simply reducing the bore of the hose it pulls it's air from, again this practice should be seen as a temporary experiment but with the additional timing you may just find you find a sweet spot and end up retaining the changes on a permanent basis with no real disadvantages.
. Once the distributor issue is fixed and to be clear, you will definitely find the engine idles better and smoother if you run 18 degrees at idle rather than the 10-12 a standard Chimaera runs at, you will also notice a significant reduction in exhaust manifold temps, as clearly documented elsewhere the easiest and safest way to increase your idle timing is switch the vac advance unit from ported vacuum to a full vacuum signal. Be aware though, running more timing at idle will have a negative impact on emissions but the truth is a happy Rover V8 is never going to be a clean one simply because the engine design is ancient and was never intended to run at 14.7:1 AFR and 10-12 degrees timing.
Make no mistake while 14.7:1 is stoich it is also way too lean for a nice smooth idle on the ancient Rover V8, 14.7:1 and 10-12 of ignition timing are both strategies that only exist in a bid to make a dirty old engine design meet ever stricter emissions targets and work with the restrictive catalytic converters used. Bin your cats, switch to manifold vacuum to run 18 degrees at idle then run a fuel calibration that shoots for 13.3:1 and she'll purr like a kitten.
Even with all that and the distributor issue resolved your old Rover V8 is never going to be as smooth as one benefiting from a distributorless ignition system, especially one that runs scatter spark, but the above strategies will definitely give you a more stable idle. Just be sure to correct your base idle setting accordingly as adding 6-8 degrees at idle will inevitably increase your idle speed by as much as 200-300rpm. Actually this increase in idle speed is the engine telling you it's happier with the increase in timing, what its saying to you is by initiating combustion earlier you've achieved a more complete burn of the fuel, and so more torque is being produced.
Back in the day and without the benefit of a strobe this how we set ignition timing, along with the 'run it to det, then retard it a fraction' method which I do not recommend. The process was simple and just required a good ear, rotate the distributor at idle advancing the timing while listening for the rise in engine speed, at the point the idle speed stops climbing you should then retard by 2 degrees.
This ghetto timing method worked perfectly for years, a good experienced mechanic back in the day would have a highly developed ear for such things, once he'd set the idle timing using this method he would test drive the car usually on his favored hill. Timing would be advanced until the onset of what we used to call pinking, at which point the distributor would be retarded by two degrees and the process repeated until there was no audible sign of detonation under load climbing that hill.
On the subject of stepper motors and the like my point would be while extra air valves can be helpful during cold start and to save a stall, generally I'm not a huge fan of idle air control valves be them of the old stepper variety or the more modern Bosch two wire rotary type I have on my Canems system. However, I must say the rotary type has the potential (if properly managed) to offer much better control than a Lucas stepper motor, and by a considerable margin.
People should be under no illusion, any air bleed, even an intentional ECU managed air bleed is still an induction leak, fact!, and all induction leaks intentional or otherwise tend to be enemy of achieving a smooth running engine. It stands to reason any air being introduced must be accompanied by additional fuel if a stable AFR is to be achieved, essentially as the stepper motor opens and closes it then boils down to how quickly the ECU can respond, which in the case of the lurching rich/lean narrow band lambda equipped ancient 14CUX processor..... isn't very fast at all
.It's also well understood that to achieve the very best throttle response you want 100% of the air you're allowing into the engine to pass via the throttle butterfly and nowhere else, this is because the throttle butterfly is the giant air valve you are directly controlling with your foot. Throttle response is all about translating the instruction your brain tells you foot to respond to, and how quickly and directly that instruction translates into an increase in engine speed.
With all the above in mind it doesn't take a genius to understand why Power's Performance MBE system doesn't even have an idle air control valve, their system exclusively uses ECU managed ignition timing to maintain the target idle speed which in 90% of all situations is in my humble opinion a significantly better idea than trying to control idle speed by allowing a bleed of air around the very system the driver himself uses to control engine speed, IE the throttle butterfly.
If you switch from the emission based ported vacuum to full manifold vacuum to achieve 18 degrees at idle the more stable idle it delivers will ensure less interference from the stepper motor will be required, and with idle air control valves less air bleed is always better. To be honest you may even find with the exception of the first 60-120 seconds of cold start you don't even need that stepper motor at all, this would be especially true for a car with no power steering and or air con and if you set your idle speed 100rpm higher than the 950rpm a Chimaera typically idles at once warm.
Completely removing the stepper motor has it's disadvantages of course and is generally not recommended especially if you do have power steering and or air con fitted, however as an experiment and assuming you don't mind keeping your foot on the throttle for the first minute or so of cold start, removing or at least limiting the stepper motor activity/interference should yield benefits... especially in the area of low speed drivability.
If you do have power steering and air con, with your timing set at 18 degrees at idle you may still find it's advantageous to limit the air bleed by virtue of simply reducing the bore of the hose it pulls it's air from, again this practice should be seen as a temporary experiment but with the additional timing you may just find you find a sweet spot and end up retaining the changes on a permanent basis with no real disadvantages.
Dave, I had put the laptop away, returned to basics and the car runs better than I thought possible, as you know
I have been driving it for the last few days following my ground up ignition and injection overhaul and it really does feel nice, no shunting, no shake on decelerating into a bend, nice easy gear changes and a stepper motor that does not come to a set of traffic lights at over 1200 rpm, just a civilised slightly higher tickover and then an instant drop to normal idle speed.
The lumpiness (and it is a gentle shake) I describe is just me being a bit overzealous and thinking perhaps I could get that sorted too while I am at it.
I am fully aware of the scenarios you describe and this really is not the issue here, it's not about the laptop at all, its just part of my careful going over each thing to ensure this car can carry on giving me this great service.
That my distributor is running a couple of degrees short of it's designed ability apparently comes down to wear on the cam itself (according to Martin - the Distributor Doctor), not the weights so a new one is in order I think, but I can't seem to find one with 20 degs of timing. Martin did suggest that I file off a mm or two from the bob weight at the point where it rests against a pin, something I read that Blitz had done, to get some more timing, but I will keep on the lookout. I won't grinding into my dizzy though unless there is a spare lying around tbh.
Without that Dave, I said this before, I cant use the full manifold vacuum instead of the ported as to have the car max out at 28 deg or even 30 deg at over 3.5k rpm without any vacuum with only 14 deg of mechanical timing, work it out, my idle will be too high using full vacuum.
With modern ECU's these figures might be acceptable, in fact even the target, but you also have fuelling to play with and other parameters and settings don't you.
I have been driving it for the last few days following my ground up ignition and injection overhaul and it really does feel nice, no shunting, no shake on decelerating into a bend, nice easy gear changes and a stepper motor that does not come to a set of traffic lights at over 1200 rpm, just a civilised slightly higher tickover and then an instant drop to normal idle speed.
The lumpiness (and it is a gentle shake) I describe is just me being a bit overzealous and thinking perhaps I could get that sorted too while I am at it.
I am fully aware of the scenarios you describe and this really is not the issue here, it's not about the laptop at all, its just part of my careful going over each thing to ensure this car can carry on giving me this great service.
That my distributor is running a couple of degrees short of it's designed ability apparently comes down to wear on the cam itself (according to Martin - the Distributor Doctor), not the weights so a new one is in order I think, but I can't seem to find one with 20 degs of timing. Martin did suggest that I file off a mm or two from the bob weight at the point where it rests against a pin, something I read that Blitz had done, to get some more timing, but I will keep on the lookout. I won't grinding into my dizzy though unless there is a spare lying around tbh.
Without that Dave, I said this before, I cant use the full manifold vacuum instead of the ported as to have the car max out at 28 deg or even 30 deg at over 3.5k rpm without any vacuum with only 14 deg of mechanical timing, work it out, my idle will be too high using full vacuum.
With modern ECU's these figures might be acceptable, in fact even the target, but you also have fuelling to play with and other parameters and settings don't you.
No problem Steve, I'm just pleased some of my contributions have helped you get to where you're currently at.
If you are insistent on retaining a distributor, other than the cost of it I'm struggling to understand given your current distributor has known issues why you just dont bite the bullet and fit a 123-Tune
It's not as good as a fully mapable 3D didtributorless ignition system but it would be a good improvement over a new standard distributor, and clearly a massive improvement over what you have now.
You've obviously invested a huge amount of time and probably quite a bit of fuel getting to where you are now, and while its admirable you've done so using what you have...... you really can't expect further progress if you insist on persevering with worn components.
I'm pleased you've put the laptop away, your next step should either be a new standard distributor or better still a 123-Tune, if your goal is a genuinely nicer driving TVR then inevitably there comes a point when you need to make what amounts to a relatively small investment in the car, especially given you know your current distributor is worn and there are additional benefits to be had by choosing the 123-Tune.
As I understand it others are assisting you in supplying your engine with a little additional fuel, if you accompany this with the removal of your cats and dialing in 18 degrees of timing at idle you will definitely enjoy further benefits. My comments regarding idle air control valves still stand but they are to some degree a necessary evil, a bit more fuel and timing will go a long way as will fixing your distributor issue... obviously
If you are insistent on retaining a distributor, other than the cost of it I'm struggling to understand given your current distributor has known issues why you just dont bite the bullet and fit a 123-Tune
It's not as good as a fully mapable 3D didtributorless ignition system but it would be a good improvement over a new standard distributor, and clearly a massive improvement over what you have now. You've obviously invested a huge amount of time and probably quite a bit of fuel getting to where you are now, and while its admirable you've done so using what you have...... you really can't expect further progress if you insist on persevering with worn components.
I'm pleased you've put the laptop away, your next step should either be a new standard distributor or better still a 123-Tune, if your goal is a genuinely nicer driving TVR then inevitably there comes a point when you need to make what amounts to a relatively small investment in the car, especially given you know your current distributor is worn and there are additional benefits to be had by choosing the 123-Tune.
As I understand it others are assisting you in supplying your engine with a little additional fuel, if you accompany this with the removal of your cats and dialing in 18 degrees of timing at idle you will definitely enjoy further benefits. My comments regarding idle air control valves still stand but they are to some degree a necessary evil, a bit more fuel and timing will go a long way as will fixing your distributor issue... obviously
You are right, a new dizzy will be needed if I can find one with 20 deg advance.
I have read mixed reviews re the 123 tune in that in a couple of cases people stated they were not far off where they started with the standard dizzy.
The stepper is a necessary evil as I have both power steering and air con.
I have read mixed reviews re the 123 tune in that in a couple of cases people stated they were not far off where they started with the standard dizzy.
The stepper is a necessary evil as I have both power steering and air con.
jazzdude said:
You are right, a new dizzy will be needed if I can find one with 20 deg advance.
I have read mixed reviews re the 123 tune in that in a couple of cases people stated they were not far off where they started with the standard dizzy.
The stepper is a necessary evil as I have both power steering and air con.
Interesting point on the 123-Tune Steve, I must admit I have no direct experience with it but I do know a guy in Holland who has one on his Chimaera and is happy with it, would it help if I got him to get in touch with you?I have read mixed reviews re the 123 tune in that in a couple of cases people stated they were not far off where they started with the standard dizzy.
The stepper is a necessary evil as I have both power steering and air con.
Problem is 90% of what the 123 is wasted as are you going to spend hours on the rollers dialing out every last drop of torque, when the stock dizzy curve is not far out? Its dead easy to file the bob weights, you just drop the springs of the weights, and strap on a protractor so you can see how far the central shaft will rotate in relation to the drive cog, then whip a bit of the bob weight stops with a dremmel and rotary stone until you get a couple of degrees extra- its not a lot of metal. Im certainly running a non ported vacuum at the moment quite happily, and I noticed the idle RPM picked up by no less than 600 rpm when I first did it so it ran better with more advance.
bobfather said:
My rovergauge documents state that the 14CUX 'absolute TPS reading' for the ECU to drop into 'idle mode' is 2% to 10% (and road speed sensor at less than 3mph), anything under 2% gives a fault signal.
BobSorry I should have explained in more detail and well spotted.
Yes you are right 10% ‘Actual’ does auto-adapt down to ‘Corrected’ 0% with no fault code, however I personally set my throttle POT to 8% ‘Actual’ as I prefer to allow 2% tolerance for resistance changes due heat or throttle sticking etc. Also, as you know the higher the ‘Actual’ % gives you higher max % at WOT.
I've tested 1% ‘Actual’ and does adapt down to 0% ‘Corrected’ but I’ve never set mine that low as I always want to maximise the WOT %. Maybe the min 'Actual' varies in different revisions.
jazzdude said:
You asked me that before Steve, I looked for it and am not sure where the 'Checksum Fixer' is to tell you.
When I pulled the original eprom out a couple of years ago it was stiff and one of the little legs snapped off. So I no longer can fit the original eprom to see what map it had.
I have been using the map I got from you that I told you about in that other thread.
I was going to load the latest map you sent me a few weeks ago this weekend but decided to run the white tune on this map for a couple more tanks first just to satisfy myself that all is well before switching over.
Even though it's running well Steve, the idle is still a little lumpy and I want to get hold of a good dizzy with 20 deg mechanical advance on it to try out full manifold vacuum, just out of curiosity, to see how that works on both tunes.
I've asked Powersparks but was told that the advance curve on theirs is 'fine' for a tvr, meaning it could be a 16 deg again. Sending it on to the Distributor Doctor would be better but it means a month off road again which I don't want to do.
Someone will come along and say leave it as it is but this vacuum thing is an itch I want to scratch.
Ahhh very sorry, I’d forgotten it was yourself that didn’t have the original EPROM and I didn’t realise you’ve stuck with my R2967_400 which is basically the early standard 400 cat combined with the Precat map.When I pulled the original eprom out a couple of years ago it was stiff and one of the little legs snapped off. So I no longer can fit the original eprom to see what map it had.
I have been using the map I got from you that I told you about in that other thread.
I was going to load the latest map you sent me a few weeks ago this weekend but decided to run the white tune on this map for a couple more tanks first just to satisfy myself that all is well before switching over.
Even though it's running well Steve, the idle is still a little lumpy and I want to get hold of a good dizzy with 20 deg mechanical advance on it to try out full manifold vacuum, just out of curiosity, to see how that works on both tunes.
I've asked Powersparks but was told that the advance curve on theirs is 'fine' for a tvr, meaning it could be a 16 deg again. Sending it on to the Distributor Doctor would be better but it means a month off road again which I don't want to do.
Someone will come along and say leave it as it is but this vacuum thing is an itch I want to scratch.
The other chip I emailed you has a slightly lower open loop idle (coasting/slowing down idle) and lower cranking idle with LR's later code which all sounds good and runs better on my 4.3 but you’ll have to tell me if I’ve made things better or worse on your 4L.
It might also be worth testing the later (1997on) Chimmy map to see if you notice any of the differences I listed in the other post,
Help yourself .... http://remap-14cux.uk/bins/TVR_R2967_400_1997.bin
Your Dizzy itch makes sense and I would be exactly the same and that's how we learn.
Steve
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