Testing Viper "ECU voltage flash"...

[Vilas]

One final safety note here. The type of capacitors we are discussing here are polarized and they store a large amount of energy. If they are installed backwards they go BOOM! Honest to goodness it sounds like a shotgun blast. So if you are going to do this, please be VERY careful to hook it up in the correct polarity. Also, these capacitors can store charge for years and can zap you (don't ask me why I know this). Much care needs to be exercised when using large capacitors. I would also recommend using capacitors with double the rating of the source voltage as a margin of safety. So we would want capacitors rated at 24 volts. They will only charge to the source voltage of 12, it is just a safety buffer.

 

[cannondale27]

The ECU does have capacitors but those are designed to stabilize the 12 volts due to small variations in operating conditions. Little capacitors can do nothing to offset giant current draws from something like a starter. Think of polarized capacitors in a circuit as trying to "maintain" a voltage. They use their stored electro-static charge to support the source voltage. So when the battery drops down to 10 volts, big capacitors will pick up the slack by discharging their stored energy and trying to maintain that 12 volts. The larger the demand, the larger the amount of capacitance needs to be. Let's say you install some big super capacitors to support the battery in your sled. The capacitors "charge up" to the same voltage as the 12 volt battery. Then once the starter is engaged, we are seeing a voltage drop which the capacitor tries to stabilize by dumping its stored energy back into the circuit. The more I talk here though, the more I'm wondering if we don't have seriously undersized cables to the starter? We should not be seeing such a big drop. The capacitor would help but it might be a band aid for the real problem which may be cabling.

Vilas I am no electrician and don't know the terms but we aren't seeing a drastic classic voltage drop in the Battery/starter circuit. The drop is at the ecu and other components. In this case IF that drop is causing the kickbacks and starting issues and in my opinion it is then bigger wire and better connections would actually make it worse since electricity is like water and travels the path of least resistance. Now bigger ecu wires to battery would be a easy thing to try. Is that what you mean?

 

[grizztracks]

Like I've been saying, the Voltage drop isn't anything that Yamaha sleds haven't experienced in the past and they've handled it without issues. It's the Cat's ECU's inability to process information during the start cycle due to a voltage drop below the ECU's designed threshold. There are plenty of engines out there that have even greater starter draws and their ECU's can handle it. I'm an electrical engineer and at one point taught a college course in Data Acquisition and Controls so I have the capability to make any measurement possible external to the ECU but I think it's a waist of time. The ECU is flawed internally and it's not a simple fix. I was going to do a comparison between my Viper and Nytro but after comparing the circuits it would be difficult to do because of significant differences in how each ECU handles external systems. For example, the Nytro powers the ignitions coils direct from the battery and the viper coils (and most other systems) are powered through the Cat ECU. The Nytro also has an active signal to the ECU that indicates a start cycle where the Cat ECU does not. I'm not sure how that signal is used but Yamaha's most likely included it for a good reason.

 

[Janne339]

Like I've been saying, the Voltage drop isn't anything that Yamaha sleds haven't experienced in the past and they've handled it without issues. It's the Cat's ECU's inability to process information during the start cycle due to a voltage drop below the ECU's designed threshold. There are plenty of engines out there that have even greater starter draws and their ECU's can handle it. I'm an electrical engineer and at one point taught a college course in Data Acquisition and Controls so I have the capability to make any measurement possible external to the ECU but I think it's a waist of time. The ECU is flawed internally and it's not a simple fix. I was going to do a comparison between my Viper and Nytro but after comparing the circuits it would be difficult to do because of significant differences in how each ECU handles external systems. For example, the Nytro powers the ignitions coils direct from the battery and the viper coils (and most other systems) are powered through the Cat ECU. The Nytro also has an active signal to the ECU that indicates a start cycle where the Cat ECU does not. I'm not sure how that signal is used but Yamaha's most likely included it for a good reason.

Ok, that makes sense. But is it something we can do to improve without replacing the Cat ECU?

 

[cannondale27]

Grizz if we isolate the Ecu and provide it enough Voltage to be happy during start will that not fix it or would introducing the additional components needed just cause more issues?

 

[cannondale27]

Janne this spring I will try using larger wire to ECU if even possible but if you agree based on Grizztracks analysis of the issue I am just going to live with it. I really think we should heed his advice and move on. Sad but its not often that a Engineer expresses as strong a analysis as he has. I am not a quitter but sometimes it is the best thing to do. We can always hope that Yamaha either finds a way or preferably just gives us a entire harness and different ECU programing to work with them.

 

[Janne339]

Janne this spring I will try using larger wire to ECU if even possible but if you agree based on Grizztracks analysis of the issue I am just going to live with it. I really think we should heed his advice and move on. Sad but its not often that a Engineer expresses as strong a analysis as he has. I am not a quitter but sometimes it is the best thing to do. We can always hope that Yamaha either finds a way or preferably just gives us a entire harness and different ECU programing to work with them.

I don't have the knowledge about the 12 volt electrical system so I agree with Grizztracks. Now begins the season as well so now I want to enjoy and running instead of having the sled standing in the garage.

Maybe we get some input during the season, otherwise we will take a look in spring when the season is over?

Thanks everyone!

 

[cannondale27]

That's what I am thinking too Janne. Thank You all those who have had contributed. Will definitely revisit this in future. Remind me this spring! Lets ride!

 

[grizztracks]

An ECU replacement may be possible but I think it would need to come with a wiring harness that replicates how the Nytro's system is powered and controlled. I don't see Yamaha doing that. The two start attempt procedure should work to prevent starter gear failures. I believe what Yamaha has done is protected the system from failure by shutting down the ECU if there isn't sufficient voltages detected during a start cycle. If all systems are working properly the first attempt develops enough charge in the electrical systems to overcome the start cycle load on the battery so the second attempt will normally be successful. This method is not new to powersports.

The two battery test seemed to correct the issue which reinforces my beliefs of what's going on here. I'm not sure if it's worth adding more devices to improve starting or to overcome the two attempt process. If it starts reliably and doesn't take out the starter gear I'd say just run it the way it is and move on down the trail.

 

[cannondale27]

Mine runs and starts great. 8000mi no starter or starter issues. Knowing what you do Should I get the flash? Thanks Griz!

 

[grizztracks]

My Viper hasn't had any issues with starting either so I'm going to wait to see if the new flash has any ill effects. If the flash proves to be reliable I will eventually do it.

 

[Vilas]

My Viper hasn't had any issues with starting either so I'm going to wait to see if the new flash has any ill effects. If the flash proves to be reliable I will eventually do it.

It's great to see an engineer on here. Grizztracks, do you think that the voltage drop could have anything to do with too small of grounding wire for the ECU or perhaps the 12 volt lead to the ECU? The reason I'm wondering is because if the gauge of the wires are right on the edge of being undersized, then a little bit of oxidation or a ground lug being not quite tight enough could put the ECU over the edge. I have been lucky with my sled but I also have redone the ground wires to the ECU and made sure they were touching fresh metal on the chassis. I also used lots of dialectric grease to keep oxidation off. Maybe larger gauge wires would be more forgiving of any small variances from sled to sled?

 

[RTX]

An ECU replacement may be possible but I think it would need to come with a wiring harness that replicates how the Nytro's system is powered and controlled. I don't see Yamaha doing that. The two start attempt procedure should work to prevent starter gear failures. I believe what Yamaha has done is protected the system from failure by shutting down the ECU if there isn't sufficient voltages detected during a start cycle. If all systems are working properly the first attempt develops enough charge in the electrical systems to overcome the start cycle load on the battery so the second attempt will normally be successful. This method is not new to powersports.

The two battery test seemed to correct the issue which reinforces my beliefs of what's going on here. I'm not sure if it's worth adding more devices to improve starting or to overcome the two attempt process. If it starts reliably and doesn't take out the starter gear I'd say just run it the way it is and move on down the trail.

I understand your statements, but unfortunately i think i am one of the few that will not be doing any more reflashes.
I had the hot start and cold start issues on my 14rtx.
I had it flashed to the 15 flash and it has now kicked back. It only happened once but it never did it on the original 14 flash.
Because of performance related issues and the kickback i decided to have evo do the stage 4 reflash my ecu.
It has only been started a few times since the reflash, but it definately starts and idles better.
Although there have been no known reports of failed starters with the evo flash yet, i still have fears of losing a starter.
Do you think anything posted in here (larger gauge wires, capacitors, etc,)would be beneficial to someone like me?

 

[grizztracks]

The variances from sled to sled is not a wire size or grounding issue. I think the variances lie within the electrically components being used in the system, ie. ECU, coils, starter motor and even the battery. Ever component is most likely within an acceptable tolerance but when assembled together the tolerance variations cause a boarder line acceptable condition in the circuit so from sled to sled there's going to be slight variations in these electrical systems. I believe the Cat ECU design is the direct cause of the start problem. It's circuitry wasn't designed to compensate for the start cycle drop in voltage on these Yamaha 4-stroke engines and with slight variations in the electrical system some are more prone to start issues . I agree that the wire size used from the battery to the ignition could have been bigger but it is sized properly for the distance and load it carries but if you still think it's an issue just parallel another wire from the battery to the ignition fuse to decrease the overall wire resistance.

There are a lot of assumptions on why the problem exists but from an engineering standpoint I haven't heard anything that would make me believe anything different. I think if it was a simple grounding issue or improperly sized wire Yamaha would have addressed that. Those fixes are on a dealer's level which has to be cheaper than a team of engineers trying to correct an ECU problem.

RTX, I believe the 2016 flash update, unlike the 15 flash will protect against kickback because it might be detecting the low voltage condition and shutting down the ECU to reduce the chance of internal failure. This is an assumptions but if the ECU struggles with processing during a start cycle it makes sense to abort a start attempt. The 2016 flash, if this is in fact what's happening may be the only protection you are going to get to insure it won't kick back. It's up to you on how to proceed.

 

[Vilas]

Thank you for this excellent response. This makes a lot of sense and will be helpful to everyone. Thanks !