Brise Starter Current Draw / Transients

[Jonathan Kay]

Thanks for that superb analysis. 

First thoughts:

1. Sounds totally consistent with what people have been observing.
2. Are those vertical white gridlines 50 ms apart? What's the voltage just to the right of the second of them?
3. Related to (2) and knowing that curve is there a way that an ordinary multimeter could be used to diagnose this?
4. Are you going to discuss with Brise... and will their response be "Fit a bigger battery"?

And one that's off the wall: How hard would it be to build a protected PSU to keep the ECU feed voltage (but not the battery voltage) high enough during cranking?

Jonathan

 

[revilla]

Jonathan,

The oscilloscope I used was a cheap-and-cheerful open-source DSO203; I would have liked to have used something better but I didn't feel like buying one just to do this one-off measurement so I was limited to using what I could manage to borrow. The instruction manual was a crude translation from Chinese and the UI was very unintuitive so I was just trying to work it out as I went along. I hope I got it basically right ...

Yes the vertical lines are supposed to be 50ms apart. The timebase is set by the orange figures at the top, so triggering off a single event (falling edge through threshold as shown by top icon on the right, threshold voltage 7V as indicated by the blue horizontal line marked "T" on the left) with 50ms per division.

The voltage scaling was harder to understand. I set it for DC coupling, 2V per division. This is the figure shown in light blue to the right of the second vertical line at the top (the yellow, purple and green blocks are for other channels but I only used one). However, testing it with a known voltage (the battery voltage) the vertical scaling did not appear to correspond to the 2V per division selected. I have no idea why. For this reason I adjusted the reference time lines T1 and T2 (the dotted vertical white lines) to correspond to two of the time divisions and confirmed the time difference between them ΔT as 50mS at the bottom. I also adjusted the reference voltages V1 and V2 (the dotted vertical horizontal lines) to align with the open battery voltage and the lowest voltage seen and used these to give the actual voltage numbers, ignoring the vertical divisions.

I don't think a multimeter could sensibly used to diagnose this; we tried. An analogue multimeter is far too slow responding to see the voltage dip. A digital multimeter is similarly too slow-sampling. My reasonably expensive meter only updates about once per second. When we tried to use it to look at the voltage during cranking, it occasionally flicked up a single very low reading but with very little consistency. It obviously depended upon how the timing of its sampling cycle aligned with the voltage transient. If you just take points along the time axis every second, there is a good chance of one of those happening to fall within some point of the transient but very little chance of it picking up the bottom of the trough. In reality I suspect that many multimeters may also "average" over a period of time, making it even harder; the other problem of course it that this behaviour will most likely vary from one type of multimeter to another. In order to see what is really going on, you really need the higher sampling rate of an oscilloscope. I guess if a multimeter had a Min/Max Voltage Hold function it could be used to show the depth of the trough but would still not show the width. I suspect both of these parameters are important in determining whether the ECU's internal power supply regulation would be able to handle the transient. Again though, without a lot of testing it is difficult to know what it would and would not tolerate.

To be honest I don't think it would be very hard at all to provide a buffered power supply to the ECU; if I had the time (rather than two little daughters!) I'd probably relish the challenge. A rough measurement of the current draw on the ECU supply pin would allow a calculation of the size of capacitors required etc. An alternative would be a small integrated switch-mode supply with step-up that could continue to provide 12V out with a reduced input. It would be quite a fun little challenge to crack; however counting against all of this would be the added complexity and the fact that the car would then be depending upon bespoke electronics. I would prefer a simpler and more "traditional" solution to be honest.

Just sticking with a Magneton is one possible solution, although as you know they certainly are more prone to K-Click type issues than some of the alternatives. There are other alternative starters available which have not been reported to cause these problems, although I haven't been able to examine any of them (yet ...). A battery with a higher cranking current rating may work better - this does not necessarily mean a "bigger" battery as some of the more modern alternatives such as lithium technologies may well have lower internal impedances. I know smaller lithium cells are now able to supply very high currents in comparison to other chemistries.

Brise have actually been very helpful on this. They have already supplied Pete with an alternative starter based on a different core. In fact they asked me to do this analysis on the starter we had as they were aware that some of their starters had caused problems but had not been able to examine one causing problems in situ. Hopefully this information (which I will pass on to them) will allow them to resolve the issue for the benefit of all.

[Mechanical Moz]

Very interesting stuff!  I have this problem on my EU2 car with Brise starter.  It started happening as the ageing Banner began to die, slowly getting worse.  I replaced that with an Ultramax type battery but still occasionally it crops up.  

I found that the engine will fire and immediately die but, if I keep it cranking through the initial kick, then after a couple of seconds it will splutter in to life and then run fine.  That makes sense as the combination of the recovery of the battery voltage, the spinning alternator and resetting ECU/IACV position eventually all get to a point where the engine will run.

I'll have to get in touch with Brise, although the starter is a long time out of warranty.  It must be at least 4 years old as it was already fitted when I bought the car, I'm sure there is a DT invoice in the history folder somewhere. 

[Jonathan Kay]

Brise have actually been very helpful on this. They have already supplied Pete with an alternative starter based on a different core. In fact they asked me to do this analysis on the starter we had as they were aware that some of their starters had caused problems but had not been able to examine one causing problems in situ. Hopefully this information (which I will pass on to them) will allow them to resolve the issue for the benefit of all.

Thanks. Do you and they suspect that the problem is inherent to the design of the model or that it will vary between units?

To be honest I don't think it would be very hard at all to provide a buffered power supply to the ECU; if I had the time (rather than two little daughters!) I'd probably relish the challenge. A rough measurement of the current draw on the ECU supply pin would allow a calculation of the size of capacitors required etc. An alternative would be a small integrated switch-mode supply with step-up that could continue to provide 12V out with a reduced input. It would be quite a fun little challenge to crack; however counting against all of this would be the added complexity and the fact that the car would then be depending upon bespoke electronics. I would prefer a simpler and more "traditional" solution to be honest.

If you sensed the voltage on the solenoid feed and the extra PSU only joined in when that came up you'd only depend on it during starting...

But for a genuinely traditional approach you could start cranking with the ECU off then flick it in after that initial transient drop in voltage. Biggles or what?

Jonathan

[CharlesElliott]

But if the ECU was off, that would likely cause issues between the ECU and the 5AS immobiliser. 

[Jonathan Kay]

Foiled again. But wouldn't it have been fun to shout "Contact!"...

Of course it needs the deeper fix as Andrew has observed.

Jonathan

[revilla]

Jonathan,

1) I think there is a problem with the design. There are too many reports of problems ... see posts #10, #24 and #28 in this thread alone for starters (another shocking pun!). Dave Andrews also told me a couple of stories of people having similar problems. I suspect there will be some variation between units, variation between batteries, variation between quality of wiring looms, some cars with FIA switches and some without, all of which will contribute to determining whether a particular car has a problem or not. It seems as though some are OK whilst the battery is in A1 condition but start to show the problem when the battery is slightly low or failing.

2) See here for possible solutions which may meet your requirements.

Cheers,

Andrew.

[Paul Deslandes]

Very interesting analysis Andrew and congratulations on your persistance!

Starters are series machines and my guess is that the armature and field resistances are much lower in the Brise, allowing a significantly higher stalled current to flow until the motor starts rotating and generating a back emf.  Once they're both running, the supply voltage looks about the same, which suggests that they're both drawing a similar steady state load current which is limited by the field resistance and back emf.

I suspect the Brise has a lower resistance field winding to deliver more starting torque, which is proportional to field strength and therefore motor current.

It would be very interesting to hear if Brise come up with an answer or improvement.

Paul

[Mechanical Moz]

Unfortunately replacing the Brise starter (with an identical WOSP unit) didn't cure the problem of the engine starting then dying unless the throttle was held open.  I went through all the connection points from the battery to the ECU supply and found corrosion in the spade connector between the purple wire from the ECU fuse and the brown/slate wire into the MFRU, but replacing this connection had no effect.  In the end I connected another car battery up with jump leads to the Ultramax NP12-20 battery in the car and this cured the problem.  Happy that there wasn't a problem with the wiring or the starter I ordered a new Banner battery.  Sure enough with this fitted the car starts just fine.

I suppose thinking about it now the problem developed as the original Banner died, got a bit better with the new Ultramax but then deteriorated again and is now cured with a new Banner.  I guess with these starters and batteries everything is just on th edge of working properly so there is little room for loss of performance in any given part of the system. 

My reason for not replacing the old Banner with new in the first place was the car is kept on a conditioner and the Banner loses electrolyte, whereas the Ultramax is sealed.  My thinking now is to prevent the parasitic drain of the immobiliser by fitting a switch to the permanent live supply for the 5AS module.  I don't particularly want to fit a full battery cut off, just an easy way to prevent the drain whilst the car is unused for weeks.

[Billy.Whizz]

I was told once of a chap arrested for stealing and drinking battery acid, he was taken to the police station put in a dry cell and charged the next day, he's currently doing ok and was very lucky it wasn't terminal. 

[Fallon]

Hi Paul,

Thanks for the link, I think this relay is already in place on my car (pretty certain) so thats 1 job I don't have to do.

Hi Jonathan,

Intersting reading! and unfortunately that is exactly what my car is now doing, start her up and need to apply some throttle. Then after 5 second ish she will idle fine. I thought nothing of it, having only started her a handful of times since fitting the motor and Andrew resolving my timing issue. I have a new battery fitted so don't have the option to replace to remove the problem so I think I need to source a new starter.

Any advice on what is the best starter to get would be gratefully received.

Also, Will using the car in its current state damage the ECU with it having to reboot on start up?

[SLR No.77]

My K is fitted with a WOSP starter and it's been faultless.

Stu.

[revilla]

It won't harm the ECU. It's just that the brief dropout in the supply voltage at the ECUs ignition sense terminal fools it into thinking you've switched the ignition off, so it sets about preparing for the next start.

Before buying a new starter, best to check that it's really this problem that's affecting you. We should have looked at it when you were here! Best to get a scope on it and see what the voltage drops to, then watch the IACV pins to spot it recycling.

Another thing you could try to diagnose it:

Does it do it every time you start, or just when either hot or cold? If you can get it into a state where it does it each time you start, with the engine idling happily, unplug the IACV connector ( with the engine still running). Then shut it down. If it then mysteriously starts and idles with the IACV unplugged, that pretty much proves it's the IACV cycling that's killing it.

You know where I am, and it's only a short drive and quick check. If you want to pop over one evening, let me know, it's no problem.

[Fallon]

I might take you up on the offer, possibly pop over early before one of your branches meet ups to kill two birds sort of thing.

I'll see if I can try what you have suggested with my limited tech skills as so far it has done it every time, hot or cold. Not the hugest sample size yet though as the starter was only fitted on Thursday evening.

We have managed to resolve the dreaded click and a badly timed engine in the last few days so I am happy I now have a reliable car again albeit one that needs a little reving on start up 

[revilla]

If you only fitted the starter on Thursday night ... was it definitely not showing this behaviour before that? or before you had the HG done? If it was starting and immediately idling OK before that, it strongly implicates the starter. Or was it all a bit tied up with the cam timing issue and just not idling properly anyway?

[Fallon]

It is definitely related to the new starter

wasn't there before HG work and associated timing issue, only apparent after new one fitted and still apparent after timing correction.

Engines aren't my thing as I have proven but fault finding I do know and I'm as sure as I can be its the SM based on all the great support on here.

I might swap in the old one for a cold start one evening to prove it.

[anthonym]

I am sad when I see these bad Brise threads. My own experience is with their older pre problem kit, which for me has always been excellent. I remember TB was real p.o. about the wosp as he reckoned it was using his know how. 
 

All water under the bridge now since I think he sold out. Anthony