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jetape

Recovery from quick throttle blips, bogs down

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This might be more of a jetski issue but maybe I can get some help on this.

When attempting to jump a wake and doing a quick throttle blip, letting go, landing and then quickly trying to ride out the motor falls on its face for couple of seconds.  It almost wants to stall.

It goes rich during the throttle blip, enrichment haven't really played with it, then RPM drops way below , 1800, idle close to 1000 upon landing and when quickly getting back on the throttle to continue it bogs down with AFR spiking.  My idle is mid 13s (this is normal)

Attached is an image, I have a log but it's 16mb I'm not sure how to reduce it after it's been downloaded.

 

 

blipissue.png

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The Lambda trace actually isn't in the correct position as the reading lags so I would say its going lean on a throttle blip, best way to see by how much the Lambda is lagging is to set a switch on a DI and when selected add 10% to the fuel map, hold it at 4k rpm and switch the DI on, by logging the DI and the Lambda you will see how long the lag is, you can then read the log better.

I would say if the fuel table is correct then you need to adjust  the accell Enrichment.

Logging TPS delta along with the TPS trace will help you work out whats going on.

Hope this helps.

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I think acceleration enrichment has something to do with it, a little hard and time consuming to play with that on a jetski.

I'm not sure about the lambda lag, the log above is messy since it was a bunch of very quick actions.  Here is a cleaner wot stab from idle, as you can see it goes way rich and the lean.

Also how my current accel enrichment is setup, what the basemap had which I don't have very much faith in.  This is a 3 cylinder 1.5L motor, inj events is most likely too high from what I've been reading in the help.

Going to watch the acceleration enrichment webinar on HPA later today.

 

launchlog.PNG

accenrich2.PNG

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I am afraid my best advice is to retune using TPS instead of MAP on the load axis of your fuel table.

Is the motor boosted, seems the map is configured for a boosted engine ?

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30 minutes ago, ClintBHP said:

I am afraid my best advice is to retune using TPS instead of MAP on the load axis of your fuel table.

Is the motor boosted, seems the map is configured for a boosted engine ?

Yes it's supercharged

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1 hour ago, ClintBHP said:

I thought so, I think you will find retuning with TPS as the load site on the fuel map will make it a lot better.

 

Did some searching on HPA and it seems TPS load is usually used for NA motors.  How would TPS load improve my issue?

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It’s used on any engines when MAP becomes an issue, using TPS as you load axis will give you demand based fuelling and not reactionary based fuelling (your throttle input is the demand and MAP is a reaction)

MGP on the load axis is great for slow revving car engines with high reciprocating mass but for jet skis I would always go TPS.

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Im with clint. 

Think about it like an ITB turbo car.  Most will use TPS as load on the fuel side for drivability and ease of tuning and simply run a 4d table to compensate for any inconsistencies in boost.

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I think I figured out why I was noticing a big bog down upon blip getting air and landing.  As the RPMs quickly drop down and cross 2400 my ignition idle control kicks in and drops timing to 5.5 from idle which is 12.  Right after that the AFR jumps to 17 which causes a noticeable stumble/bog down.  Haven't tested yet but seems logical.

My ignition idle must be too aggressive at the higher delta numbers.

 

 

blipissue2.png

ignidle.PNG

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5 hours ago, Steve said:

If you change the y axis from etc (which you really arent using anyway) to rpm roc you can fix the idle ignition going low when you dont want it to.

Interesting, what does ROC do?

I tried more gradual decline where the -250 column is 10, it seems to have helped from a quick test I did.

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ROC stands for Rate Of Change. Or dRPM (delta RPM)  if thats a more failiar term. Its a parameter that tells you how fast rpm is changing pr second. If it rises from 2000 to 3000 rpm in one second you have a value of 1000. Does it use 2 seconds to do the same ROC is 500. If rpm is dead stable ROC is 0.

In the attached picture you can see an example. Base timing in that is 12 degrees but when rpm drops when i clutch the car (it is usually more than -1000 dRPM)  timing is at about 22 degrees falling towards idle arget. Dropping as dRPM drops.

Thats not a screenshot from the link software but the same can be done there.

Idle ignition table.png

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Ah that would be helpful, RPM is falling very fast especially at the point when the ski regains contact with the water so if the idle ignition trim kicked in at the right (wrong) moment it could send it way below idle.  Will experiment with it, thanks :)

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Yourewelcome.
Sidenote. I am also using the same parameter on a idletarget offset table. Works sort of the same way. When dRPM drops more than -500 my idletarget increases by 500 rpm. This helps "catch" the engine and sets it down nice and slow. Havent seen a way to do something like that in the Link yet though. Could have done it with a 3D idletarget table but its not possible as of now...

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