Big fuse diag with RS-AJP
Discussion
Hello,
I thought I would share what I did yesterday, first to be sure of my theory, and second because this could be helpful to others.
My newly acquired cerb developped pretty quickly 2 symptoms : first erratic tachometer readings, second and some stuttering at 2k RPM.
As these (especially the first) are typical of the infamous big fuse failure, I decided to log the voltage using RS-AJP so I could check the voltage. This is what I got on a short trip :
As you can see, we clearly see the ramp up of the voltage at low revs, where the alternator does not charge the battery much. We also see the regulated voltage (around 13.2V) from the regulator of the alternator. What bothered me is that there are lots and lots of dots under 13V, so something is wrong. I assume it's normal that there are some low dots, but not that much.
So I changed the big fuse to a 125Amp one, and got this :
We still see the ramp up at low revs and the regulation, but regulation is higher (arounds 13.3-13.4V) and a lot more defined. Results! There are still lots of low dots, but definately less, and not so low. I assume it's normal that the regulation is not 100% precise (if not, tell me!) but the upper line of the regulation is clearly much more defined, and the lower cloud is definately less crowded, in spite of a longer logging session.
In practice, the car performed flawlessly, with no stuttering and accurate tacho indformation.
The old fuse looked perfect at removal, so this is definately interesting.
What do you tink about this? Do the theory sound good? Do the second graph look ok, or should it be more accurate and I have problems with alternator regulation or battery wiring?
Thanks!
Julien
I thought I would share what I did yesterday, first to be sure of my theory, and second because this could be helpful to others.
My newly acquired cerb developped pretty quickly 2 symptoms : first erratic tachometer readings, second and some stuttering at 2k RPM.
As these (especially the first) are typical of the infamous big fuse failure, I decided to log the voltage using RS-AJP so I could check the voltage. This is what I got on a short trip :
As you can see, we clearly see the ramp up of the voltage at low revs, where the alternator does not charge the battery much. We also see the regulated voltage (around 13.2V) from the regulator of the alternator. What bothered me is that there are lots and lots of dots under 13V, so something is wrong. I assume it's normal that there are some low dots, but not that much.
So I changed the big fuse to a 125Amp one, and got this :
We still see the ramp up at low revs and the regulation, but regulation is higher (arounds 13.3-13.4V) and a lot more defined. Results! There are still lots of low dots, but definately less, and not so low. I assume it's normal that the regulation is not 100% precise (if not, tell me!) but the upper line of the regulation is clearly much more defined, and the lower cloud is definately less crowded, in spite of a longer logging session.
In practice, the car performed flawlessly, with no stuttering and accurate tacho indformation.
The old fuse looked perfect at removal, so this is definately interesting.
What do you tink about this? Do the theory sound good? Do the second graph look ok, or should it be more accurate and I have problems with alternator regulation or battery wiring?
Thanks!
Julien
Edited by Jooles81 on Sunday 21st August 10:07
Edited by Jooles81 on Sunday 21st August 10:08
The problem is not the idle, tbh. adaptatives are really out, there is some slack in the throttle linkage, and the lambdas are making some strange stuff.
moreover, I took the car again today for a spin. It's running great, though voltage is between 12 and 13V at high RPM, and all over the place, so I think there is another problem...
Julien
moreover, I took the car again today for a spin. It's running great, though voltage is between 12 and 13V at high RPM, and all over the place, so I think there is another problem...
Julien
Hello !
The fuse has nothing to do with the difference. Either the new connection is better, either the old fuse had an airline crack I have not seen. As far as I've read, the low voltage at idle is normal for a Cerbera. Moreover idle is low at 850 instead of 950, which does not help. But I may be wrong!
Julien
The fuse has nothing to do with the difference. Either the new connection is better, either the old fuse had an airline crack I have not seen. As far as I've read, the low voltage at idle is normal for a Cerbera. Moreover idle is low at 850 instead of 950, which does not help. But I may be wrong!
Julien
From what I understand, there is a flaw in the design of the charging system of the cerbera : idle is set at 950rpm,but he alternator charges the battery from around 1050rpm (see my graphs). This puts stress on the battery, especially in town driven cars, and I think this is what led to the cerbera reputation of eating batteries. And this is what I think Aide and Julian64 want to overcome by setting the idle higher.
Julien
Julien
tangerinedream said:
Jooles81 said:
From what I understand, there is a flaw in the design of the charging system of the cerbera : idle is set at 950rpm,but he alternator charges the battery from around 1050rpm (see my graphs). This puts stress on the battery, especially in town driven cars, and I think this is what led to the cerbera reputation of eating batteries. And this is what I think Aide and Julian64 want to overcome by setting the idle higher.
Julien
Woodrow Wilson, the voice of reason...Julien
Julien
Actually, the alternator probably can not be spun faster as, as grufallo said, it comzs from a landy that redlines at 5500rpm.
Solution would be to find another alternator that fits and that can be spun faster.
On the other hand, what limits an alternator speed? Would it be possible to mod an alternator so it can spin faster?
Julien
Solution would be to find another alternator that fits and that can be spun faster.
On the other hand, what limits an alternator speed? Would it be possible to mod an alternator so it can spin faster?
Julien
Found those guys that can build heavy duty alternators for range rovers and the like. Maybe they could make one for the cerbera?
http://www.qualitypowerauto.com/category_106/Land-...
http://www.qualitypowerauto.com/category_106/Land-...
There are 2 other important points: minimal rotating speed to charge the battery, and why the regulated voltage is so low. From the graphs, the alternator regulates between 12.5 and 13.3V, instead of 13.6/ 14.4. Why? Could it be that the cables are so old and worn that the resistance is bringing voltage so low? Are Aide's and my regulators shagged to the point the regulate 1V too low?
Julien
Julien
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