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Author Topic: rotax engine tuning?  (Read 4880 times)
k0mpresd
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« on: May 08, 2015, 10:07:48 PM »

anyone have experience with these? have a 900cc 3cyl n/a rotax in a seadoo.
bosch me17.8.5 ecu.
richest lambda on the stock map is .9219. i purchased a pretuned file off the ols server as a base starting point which has lambda request all the way down to .7344.
this just seems way too rich when stock isnt much far off 1.0.

is that how these little motors make power is run them pig rich?
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tjwasiak
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« Reply #1 on: May 08, 2015, 11:41:27 PM »

IMHO running them so rich kills them even faster.
The only way to found proper AFR and ignition setting is to tune at the dyno...
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gt-innovation
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« Reply #2 on: May 09, 2015, 06:58:25 AM »

anyone have experience with these? have a 900cc 3cyl n/a rotax in a seadoo.
bosch me17.8.5 ecu.
richest lambda on the stock map is .9219. i purchased a pretuned file off the ols server as a base starting point which has lambda request all the way down to .7344.
this just seems way too rich when stock isnt much far off 1.0.

is that how these little motors make power is run them pig rich?

No they do  not run like that for sure.

I have tuned some super and turbocharged ones and some with bigger compressors/injectors etc..I used a wideband for getting the stock afr first...Those engines are actually running a little bit richer (around 14.0 at idle) than a normal car engine but not with the lambda value you mentioned in full throttle . Both siemens(older ones) and bosch ecus are running at the same afr levels as stock.However all of the engines i did was 1500cc and not N/A but i am sure running that rich will never produce the amount of power that is needed.
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k0mpresd
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« Reply #3 on: May 09, 2015, 09:06:39 AM »

thanks for the feedback.
i was going to start with around a .8907 lambda at full throttle and work from there. sound reasonable?
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gt-innovation
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« Reply #4 on: May 12, 2015, 05:22:11 AM »

Yes 13ish sounds good .
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ddillenger
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« Reply #5 on: May 15, 2015, 12:39:27 PM »

Something I think that bears noting even if it seems like common sense:

These things run at wide open throttle, at redline for 90 percent of the time they're being used.

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