Setting ignition timing in MPEM on the 787

[GGuillot]

Ok, looking for someone who has experience with this, I was curious so I checked it, I have a timing light and a CANDOO PRO so why not. Here's what I found, in the factory settings in the MPEM, according to the Candoo the factory had it set to a correction of '5' which on the scale of 1 through 8 is a setting of retard timing of - 1 degree. Before changing things in the MPEM, I took a red marker and marked the PTO flywheel referencing top dead center from the mag cylinder. I used the little hole on the bracket as my reference point looking straight down with the timing light. Fired it up and according to the SM, at about 3500 I'm getting an advance in current form, to the right of the reference, maybe 3/4" to 1" but off the mark. So that means it needs ignition timing needs to be retarded a little.

I connected the Candoo, which is an excellent device by the way, tells me exact hours and minutes since the rebuild and total hours, easy to program keys, etc. So I selected setting '6' which is - 2 degrees retarding timing. Started it up, not much of a change, little bit of a change on settings 7 and 8 which is - 3 and - 4 degrees. On '8' at -4 degrees retard timing when I rev to about 5000 it lines up to the reference point. I ended writing to the MPEM with setting '6' which is -2 degrees.

I'm going to take it out on the water and see how it performs, but wondering if anybody has experience with tweaking these settings, there's also 8 settings for a 'curve' which I can't find a reference anywhere to verify how it changes things. Limiter settings I assume is the rev limit, both curve and limiter are set at 0.

 

[mikidymac]

@Matt Braley has messed with the different curves. It’s not common.

 

[Matt Braley]

I don't have the Candoo but the old dealership and racing programmers. There is no ")" setting on those the rev limit and timing curve are set to 1. I use the #5 curve normally on performance skis. I also advance the static timing a degree or two but I only run fresh high test fuel and I keep a close eye on cylinder temps via egt gauges.

 

[GGuillot]

I don't have the Candoo but the old dealership and racing programmers. There is no ")" setting on those the rev limit and timing curve are set to 1. I use the #5 curve normally on performance skis. I also advance the static timing a degree or two but I only run fresh high test fuel and I keep a close eye on cylinder temps via egt gauges.

On the settings 1 to 8 what is the curve change? does it go from mild to radical? with 5 being in the middle? does it mess with the timing? In stock form at 1 factory setting, it appears timing is advanced on the lower part of the powerband then flattens out at the 5000+ range. Least that's the way it appeared with the timing light.

I'm curious, because I thought of bumping it from 1 to either 2 or 3 and see how it performs. I already run WISECO pistons, which I know for a rec ski wasn't necessary.

 

[Matt Braley]

No some of curves don't fit the engine well at all. Normal dealers never had the ability to mess with that, just the initial (static) timing. The #5 curve is just about like a 717 curve and it is well known to be the answer for racing. If your a rec rider and have other race mods then too much timing risks detonating your engine unless your using a higher octane fuel. The #5 curve puts more timing in the mid range then the #1 curve that all stock 787's come with. At WOT I actually run a little cooler with the #5.

 

[GGuillot]

No some of curves don't fit the engine well at all. Normal dealers never had the ability to mess with that, just the initial (static) timing. The #5 curve is just about like a 717 curve and it is well known to be the answer for racing. If your a rec rider and have other race mods then too much timing risks detonating your engine unless your using a higher octane fuel. The #5 curve puts more timing in the mid range then the #1 curve that all stock 787's come with. At WOT I actually run a little cooler with the #5.

Noted on #5 curve and stock #1, but there's no information out there about the other curves?

 

[Matt Braley]

I've seen the chart but again it only went out to 8 Seadoo supported tuners 23 years ago. Candoo should not be letting folks alter that stuff. It's like Mikuni including the wrong weight springs and extra gaskets you don't need in the carb kits, only causes unnecessary trouble.

I see the info there on the screen, can you actually change it?

 

[GGuillot]

I've seen the chart but again it only went out to 8 Seadoo supported tuners 23 years ago. Candoo should not be letting folks alter that stuff. It's like Mikuni including the wrong weight springs and extra gaskets you don't need in the carb kits, only causes unnecessary trouble.

I see the info there on the screen, can you actually change it?

When I get home later tonight I'll check, I've been cautious to not change it and haven't tried. But I'll verify.

 

[GGuillot]

I've seen the chart but again it only went out to 8 Seadoo supported tuners 23 years ago. Candoo should not be letting folks alter that stuff. It's like Mikuni including the wrong weight springs and extra gaskets you don't need in the carb kits, only causes unnecessary trouble.

I see the info there on the screen, can you actually change it?

Yes, on the Candoo you can change it and write to the MPEM. I wish I had an idea of the 8 settings in curve to what it changes. If you have old contacts do an inquiry, I can't figure out why it's such a secret about these settings.

 

[Matt Braley]

Look up my thread on here "787 MPEM Manipulation" and on it there are pics of the fax that Seadoo Racing sent out in 95. As far as I know that is the best info out there available.

 

[GGuillot]

Look up my thread on here "787 MPEM Manipulation" and on it there are pics of the fax that Seadoo Racing sent out in 95. As far as I know that is the best info out there available.

Thanks Matt, I may start running 92-93 octane for a little while and do some experimenting myself and see what I can discover on the different settings. The consensus I'm hearing is setting 5 is the race setting for back in the day, the others nobody has any knowledge what they do.

I'm slightly rich on the HS needle, 1/2 mag and 3/4 pto, stock oil injection with 60:1 premix, and I run wiseco pistons but otherwise it's stock. Runs great, but I'm gonna proceed with caution if I decide to tweak the timing curve.