Thread: RPM rate of change factor
11-09-2010, 06:42 AM #1
RPM rate of change factor
Hi Pete and Motec gang,
Thanks for Rips imput on this subject, Pete us rough water/surf jumpers put alot of stress on our skis and bodies .Nothing better than ripping around in the whitewash full throttle.
Trying get get my ski as reliable as I can, 90% of my riding is out in heavy surf so unhooking is always happening.
I am running my ski with the stock wheel at the moment after blowing 2 clutches out in the surf with a 13pd wheel in. I will put it back in after I am confident the clutch issues are worked out.
I am running my Motec with 2 maps and GaryW has kindley taught me launch control and DBW throttle positions so I can fine tune my "surf map" for my riding style. I then switch over to the higher RPM map for the flat water ride home.
My surf map has the limiter set to 7700 which is about 100rpm higher than my 7600 flat water rpm limit running this tune with 80% actual throttle set into the DBW. I find this is ideal for the surf jumping I do. I was trying to get my flat water RPM and unhooking limiter close as possible for the surf riding.
So whats the "RPM rate of change setting"? I understand that its set to 0 in my maps so the limiter just cuts spark,right?
If I change it 1 on my surf map what will it do? will it sort of sense that I am blasting up a wave face and start limiting just before I unhook and get air?
This might keep my motor a little bit safer would it not?
So do you need to do anything else or just set it to 1 (enable) in the RPM menue?
Cheers for the feed back, goes to show these Motecs are not just meant for full flat water speed runs that most people are trying to get out of their skis.
11-11-2010, 01:02 AM #2
11-11-2010, 04:01 AM #3
I have an answer for you but I want to get some more tecnical info from our inhouse genoiuses before I write back
Its a good question and the info is going to be valueable.
RPM limiting as a subject is huge for jet ski's
bump it again if I havent replied by tuesday next week,
11-11-2010, 06:30 AM #4
11-16-2010, 03:38 PM #5
- Join Date
- Oct 2007
- Brisbane, Australia
How's it going Pete? I know you would be flat chat but...............
Coldspace has just about perfected the holeshot verses position translation side of things on his stock FZS. It flicks out of the water like a rubber band and not a spec of cavitation.
Now it's time to slow that motor down from spinning too fast.
We're aiming for a max rev limit of around 8000rpm (absolute) with a flat water limit of around 7700 using the prop pitch to hold it back. He has found that the stock wheel has a little bit of an advantage over the low boost wheels between 5500 to 7000. This will be good when gaining momentum up the face of the waves for jumping which is the primary role of this ski.
Hope to catch you soon,
Last edited by Gunna; 11-16-2010 at 10:01 PM. Reason: More detail.
11-18-2010, 04:16 PM #6
- Join Date
- Oct 2007
- Brisbane, Australia
11-19-2010, 07:11 AM #7
Pete if I just enable (set to 1 from 0) my rate of change factor will the ecu sense that my ski is accelerating very fast upto the limit and start pulling power a little earlier?
Is it going to mess with anything if I change it and take it for a spin out in the surf this weekend or is there more to it?
11-22-2010, 01:00 AM #8
Sorry for the delay
Work is just balistic at the moment and I can usually catch up at home on this stuff but same story there at the moment.
ok the deal here is
Previous to version 3.52P the ECU would automatically detect an excessive rate of change happening close to the RPM limit
If it calculted the the RPM limit would be exceeded within 1 cycle it started invoking the RPM limit, the trouble with this is that when a racing ski hits the limiter it takes a certain amount of recovery time each time the coils have to fire back up again, this makes for slower speed in the chop.
So for CC racing you never, in reality, want to hit the limiter. In an ideal world the ski would come out of the water and begin to over rev but before revs got too high it would land back in the water again, when it does this, and if the rpm limiter has not been hit the engine recovers instantly and powers on through the chop.
So predictive RPM limiting is not useful in this instance.
Wave jumping is another thing altogether, in this case you would want the predictive cut on and this is why the feature was exposed in version 3.52P
So by all means turn it on, you wont do any harm.
I would set your limiter to zero control range and set it 100 rpm above your clean water rpm
You could also experiment with the RPM limit table
You could change your rpm limit proportional to throttle position.
So at say 100% throttle you run 8000 limit and at 50% you run 7400.
The ECU will interpolate between the 2 automatically
thats it for now
11-22-2010, 04:45 AM #9
Hope thats what you mean and if so where do we find this feature?
Another question, I know you wouldn't want any of this for serious racing but for rec guys who want to run up into the mid 8000 region this feature would be best left on wouldn't it to help keep some of the over revs down a little if riding hard through the usual choppy water and to keep a bigger saftey margin on stock internals wouldn't it?
I have just set my surf map to enable and my fast flatish water map to enable as well with the limiter set to 8300 which is 100 higher than my flat water rpms.
Will help us rough water guys keep check of the internals .Thanks again.
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