Forum » General Tuning Discussion » Throttle stab fuel cell tuning

Throttle stab fuel cell tuning

General Tuning Discussion

Discuss all things tuning in this section. News, products, problems and results. 

Page 1

Hi guys,

When stabbing the throttle from idle to wot the cells which are hit in the ve table are totally different than when doing a more gradual acceleration. Do you still have to tune those fast passing cells? This is on a supercharged jetski so all of it takes less than a second, hard to say just how accurate AFR readings are during theses times. I want to make sure before I start adjusting accel enrichment so that I'm not chasing my tail.

Also, the RPM varies very quickly on a jetski, it can go from idle to 9k in fraction of a second, would it be better to tune VE for TPS vs RPM or MAP vs RPM.


You're kind of covering too aspects here. The fuelling requirements during throttle transients are different to what we need during steady state. The complexity though is that to have any hope of the transient tuning being correct, the underlying VE values also need to be correct as the transient fuelling basically acts as a multiplier of the base fuel values. This can be tricky if you're tuning the ski on the water as you can't really access all of the cells in the table. Have a look in our webinar archive and search for 'acceleration'. We've done a few on transient enrichment. Here's one example:

Thank you for the reply.

I actually watched your accel enrichment video the other day. What you are saying is I actually have to adjust the transient cells that get hit during the split second a throttle stab happens?

I'm not sure how accurate the data is during this short period of time. I believe my LC-2 logs lambda at 20Hz and in PCLink I have logging at 40Hz. Looking at the log, RPM goes from idle ~1800 to close to 9k in just under 1 second. It shows 1psi of boost at 2.5k RPM which it can't be since the chargers on these skis start making boost at 6k where the log shows already 7psi.

Attached is a screen shot, I'm pretty sure accel enrichment is set too high. Adjusting the wild transient cells in these short throttle blips will be tricky.

Attached Files

I spent some time with a tablet on the water adjusting accel enrichment, it seems these Rotax 1.5L don't need much if any at all. I pretty much turned it off, down to 2% clamp and that got the rich spike from mid 9s to mid 11s AFR.

Takes off great, now just to keep off the RPM limiter which it instantly hits.

Attached Files