916 Electric problem! HELP (ignition system explained)

[CipiVTS]

Hi all,

I have a Ducati 916, 1995.

2 weeks ago i was driving my Ducati and suddenly it started to misfire, wouldn't rev over 3000rpm and finaly engine stopped.

checked at service and noticed that a connector from the 2 wired alternator to the regulator was melted, so it didn't charge and finally the battery was drained.

Fixed the wires and it went ok.

I remembered in the last weeks before the incident the bike's acceleration was poor/harsh (seemed like the spark was not strong enough to ignite all the mixture). Finally realized why.

So after fixing the wires we checked the voltage of the alternator and it was really bellow the standard data:

1500rpm 25V instead of min 35V
3000rpm 50v instead of min 75v
and 6000rpm 85V instead of min 140V

Also the regulated voltage was bellow 13V (recommened is between 13.5V and 15.5V)
With the main light on the voltage went bellow 12V

So the next day i changed the battery with a new one and the readings improved a bit, but still bellow accepted ones.

I also realized the misfire while accelerating was not so strong as before and the engine reved smoother throught the range.

WE measured the stator's resistance and we noticed both yellow wires ahd resistance with the ground (so something must have been wrong with the stator)

Replaced the stator with another used one, and checked the readings again.

Nor ground resistance so the stator must have been ok, but the alternative voltage reading are pretty much the same with the previous one. The only thing that changed was the regulated voltage which is now 13.6V at idle and 14.0 V while revving. The rev increase is realy smooth in all gears and the bike runs very well in all gears.

The only problem is when i turn the main beam on and suddenly the regulated voltage (measured at the battery) drops to 12.3V. If the fan starts it even goes bello 12v. If i rev it a bit it jumps to 13.3v

Driving with the lights you can really feel a differnce vs without. Harshness and misfire appears again while accelerating.

So in this case, can anybody give me any advice what do i have to replace?

Is this normal to have this regulated low voltage? Is because of the regulator unit being faulty? Or is it because of the generator's stator or rotor being damaged ?(and that's why the low alternative voltage readings)

Please help... 1 generator costs ~400 EUR and 1 Regulator is ~220 EUR. Is it worth it that i should buy both?

Thanks

Please hel

[KeefyB]

It does sound as if the regulator could be faulty.:(

[CipiVTS]

This would be great...

But couldn't also be the alternator that is performing under minimum requirements and because of that the regulator cannot hold the current with the lights on?

what do you think of an aftermarket regulator like Electrix?

Can i fit the newer 916/748 3 way alternator to this engine (newer stator/rotor, newer left engine cover) + the newer regulator?

[nelly]

check also the rest of the wiring near the regulator. The two yellow wires are the common culprits, but the small loom that sits down there could be toast to.

[CipiVTS]

Sorry it was Electrex http://www.electrexworld.co.uk/

I checked the wiring in that area and it seems fine. What can be the symptom of a damadged loom, current loss?

[skidlids]

As Nelly says check the two yellow wires futher back, on my 748 I spent a bit of time choping the bullet connectors off the wiring from the engine and replacing them as well as replacing the two yellow wires that run between them and the plastic block connector that connects them to the reg/rec.

Also consider replacing the fuel filter if it hasn't been done for a while, as when it starts to block up it loads the fuel pump more which then draws more current and with the single phase alternator models their is only so much current to go around.

[keith_mann1959]

Hi CipiVTS
I have a Genuine ( later version )2 wire regulator thats never been used, had it as a spare for years.
£45 if that helps you.
U2U if interested

[chrisw]

This article might help

http://www.buschandbusch.com/ducatisuite/wiring.html

[KeefyB]

Was'nt there something on early bikes where the rubber clips that held the relays near the battery actually conducted electricity?
Just a thought.

[crm250]

Hmmm this is an area i am well versed in with 2 failures of the same in 3 years and 20k miles.
Firstly i put money on the rectifier being toast.
Secondly, the 2 wires that run across the motor between the gene and rectifier i also put money on are brown and brittle
Thirdly i also bet the sub loom near the rectifier is also not exactly Y reg if you catch my drift.

The sub loom is cheap drom ducati / nelly etc etc, around 30 quid if i remember last time i bought one

The 2 wires from the gene, best way to do this is to remove the gene and get tested, and then upgrade the wiring from the gene itself with a heavier cable, or at least 1 more length of the same.

Snip the bullets off between, and either use a high quality connector block which is not only tight (loose fittings increase heat and cause failure) but also capable of handling extra current draw, and same on the new sub loom. or better still solder them together.

I ride all the time with my lights on, and i could be wrong here but little things like lower wattage indicators, and LED tail lights will help matters just a tad and could make all the difference.

[Shazaam!]

http://ducatisportingclub.com/control/boards/viewthread.php?tid=2042

The likely reason that it ran rough is that the lower voltage being supplied to the coils was inadequate to fire the plug gaps, causing one cylinder to drop out. You could need new plug wires but check the plug gaps first.


DUCATI IGNITION SYSTEMS

A good ignition system needs to be able to ignite the combustion chamber fuel-air mixture with as few misfires as possible (there’s always a few.) When you reduce the number of missed combustion events, you improve overall power, fuel economy, and particularly, throttle response. Generally, missed ignition events are most likely to occur during throttle transitions when the fuel-air mixtures are changing rapidly. This is usually described as “poor throttle response”, the inability to respond rapidly to throttle inputs.

You can reduce these misfires if you can increase the size of the plug gap and still reliably maintain the intensity and duration of the electrical arc across the gap. A highly-compressed fuel-air mixture is difficult to ignite, so a larger gap increases the opportunity for fuel molecules to enter the gap and a longer duration, more intense spark allows for a wider window of time for, and likelihood of ignition.

But, increasing the plug gap places higher demands on the sparkplug wires and ignition coils because it takes a higher voltage to fire a larger gap. The coils need to robust enough to supply an adequate spark kernel and the plug wires need to be able to transmit this electrical energy at the higher voltages needed without failure of the conductor or insulation.


Spark Plug Wires

The stock spark plug wires are constructed with a stranded core covered with an EPDM insulating jacket. Like most wires, the conductor itself will last a long time, but the insulation will start to degrade after a couple of years from engine heat which is why most quality aftermarket wire is insulated with silicone rubber.

If a spark plug wire with old insulation is too close to adjacent conducting components, the wire will arc across the insulation at a voltage lower than that needed to fire the plug gap and a misfire occurs. This is more likely to occur in damp weather since moisture in the air is a good electrical conductor.

So the first step in upgrading your ignition system is new spark plug wires.

For street bikes, you should use carbon core wires, preferably carbon wires with a spiral wrap center conductor. Straight, multi-stranded, unshielded wire conductors offer theoretical performance gains, but unfortunately produce lots of electromagnetic interference (EMI).

EMI can interfere with the computer used on fuel injected bikes and corrupt internal signals which can affect engine operation. This concern also extends to non-resistor plugs. Theoretically, straight-wire components can provide more power, but the reality is that the EMI produced can and does corrupt computer sensor signals and computer operation itself. It also raises hell with the radio in the car next to you.

When the time comes, usually after a couple of years, I recommend replacing the stock sparkplug wires with a set of Magnecor wires. Magnecor #2549 wires for a Ducati superbike cost $67, but other aftermarket suppliers also offer quality EMI suppression wires.


Ignition Coils

Ducati’s use an inductive ignition where coils are charged with 12 volts and then apply a high voltage to the sparkplugs when signaled by the igniter. The typical firing voltage is 8–10,000 volts, with higher firing voltages needed for a high compression engine. Once the spark jumps the gap, it only requires several hundred volts to maintain the electric arc while the coil discharges.

The main advantage in using an inductive system is that you get a relatively high current, long duration spark (2,000 microseconds) that works very well for low speed, lean mixtures and partial throttle applications. The main disadvantage is that because it takes a finite amount of time to charge a coil, and at very high rpms there isn’t enough time to fully charge the coil between firings. Fortunately, Ducati street bikes don’t rev high enough for this to be a concern.

Stock coils on early Ducatis can be improved upon by installing aftermarket coils such as those made by Dyna, Accel, or Nology. Their primary advantage is that due to the larger physical size of the coils, the duration of the spark is longer. An intrinsic limitation of aftermarket coils with more windings is that they take longer to charge and discharge, so they have less and less time to cycle as rpm increases. Therefore, their available secondary voltage drops (faster than small coils) as rpm increases.

Fortunately, the newer stock Ducati coils are quite good given that they’ll fire a 0.044 inch plug gap even though the factory recommended gap for standard plugs is around 0.024 inch. Consequently, there’s no demand for aftermarket coils for superbikes.


Ignition Amplifiers

Another way to fire a larger plug gap is to increase the operating voltage of the stock coil.

One product, the Evoluzione ignition amplifier increases the primary voltage to the stock Ducati coils from 12 volts to either 16 volts or 18 volts (user selectable). The way a coil works is that if you put in 12 volts (primary) and get out, say, 12,000 volts (secondary), then if you put in 18 volts you will get out 18,000 volts. Again, this requires coils and wires in good condition.

Evoluzione recommends for best results that you run a 0.060-inch (!) plug gap instead of a 0.024 stock gap on a superbike, the larger gap being the key to getting a stronger spark and increasing the overall likelihood of a combustion event.

One reservation that I have about ignition amplifiers is that they could cause overheating and premature failure of the stock coils or wires. This reliability consideration has to be balanced against improved performance. An independent test by Road Racing World magazine on a GSXR 1000 saw only about a 0.2 HP improvement. Again, the main benefit here is throttle response.


Spark Plug Gaps

So, if you’ve got good plug wires and coils (and maybe an ignition amplifier) then you can fire a larger plug gap.

If you use conventional sparkplugs, start with the recommended gap and try opening the gap up in 0.002 inch increments. You should note a progressively smoother throttle response if not more power. When the bike begins to lose power (misfires), go back 0.001 - 0.002 inch and this will be your optimum gap.

As a good rule-of-thumb, if you go more than 0.008 inch over the out-of-the-box gap you won’t maintain parallel surfaces between ground and the center electrodes. So if you reach that point, change to a plug that starts at a higher gap. The NGK dash 9 series starts at a 0.9mm (0.035 inch gap), for example.


Platinum and Iridium Spark Plugs

The initial reason this type of plug was developed was to extend plug life due to US EPA-mandated exhaust emission system low maintenance requirements, not because they offered any improved performance over conventional electrodes. They incorporate electrodes made of harder materials that erode more slowly and consequently don’t need to regapped as often.

The big benefit to having platinum or iridium as an electrode material is that the harder material erodes more slowly and consequently allows you to reduce the size of the center electrode and still have a long-lifetime plug.

But remember, a smaller electrode will initiate an arc at a lower voltage.

Consequently, you should NOT run these plugs at the factory recommended gaps. If your coils and wires are weak then a smaller gap will reduce misfires, but should be applied only as an interim measure.

NGK and Denso pre-gap their Ducati application iridium plugs to 0.035 inch. This should be considered a MINIMUM gap for this kind of plug. Their smaller electrodes fire this larger gap at about the same voltage as a conventional plug fires the factory recommended gap - with one added benefit - a strong spark kernel across a larger plug gap = improved throttle response.

Consequently, dyno testing shows a performance gain with specialty plugs only when their intrinsically lower arc-over voltage has allowed users to increase the plug gap above that possible with conventional steel electrode plugs. Try increasing the gap beyond 0.035 inch for further improvements. You should be able to go to 0.040 inch on a new superbike.

Said another way, platinum or iridium plugs in your Ducati will give you worse performance than a conventional plug unless you use a larger gap than is recommended for the steel electrode plug equivalent. I have seen repeated examples of poor Ducati running and throttle response problems cured by replacing platinum or iridium plugs that were gapped too small (i.e. at the 0.024 in. Ducati recommends for conventional plugs.)

[CipiVTS]

Hi,

Thank you all for your posts and thanks shazaam for the long and very interesting explanation.

So in my case i did the following test in orders to check if there is a short in the lighting system.

With the lights off and the engine at idle and regulator putting ~13.9V i connected an H4 55w lamp directly to the battery. The readout dropped exactly like before ~12.5V (perhaps not so much because with the lights on there's also the number plate light, front an tail lights + instrument panel). So practically the issue is not in the electrical system, it should be in the current output.

The regulator fitted my 916 by the previous owner is a SH673-12 that i checked that was originaly fitted to the 996 2000 model. It was initially a 3 phase system regulator, but mine has the middle yellow wire completely removed (not by someone, but it looks like it has been removed when it was built). Has Ducati offered these regulators to change the bad old ones???

I have another SH579B-11 3 phase regulator from a 2000 748 and i put it on the bike.

With the lights on it gave exactly the same value as before (12.3), but with the lights off it didn't increase over 13.7v. I revved it all the way through the range and never increased a bit.

So, judging both cases i assumed there's a probelm with the alternator that is not functioning ok and therefore i ordered a new stator/rotor for 160 pounds from Electrex.

It should arrive next week and i'll get it fitted asap. I still stayed with the current regulator (SH673-12), but i will change it if it doesn't make the desired current.

I will change all the wiring from the stator to the regulator with the 10 gauge type just in case.

I also have to add that i did this test with the fuel filter replaced 2 days ago.

Do you have other ideas in this case? What else should i do?