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Jerky car at low speeds/loads
Posted: Tue Jul 18, 2023 11:27 am
by Flyingdutchman
Hi
I have a k20a in a Lotus. It was recently rebuilt to N/A and dyno tuned based of the std setting. The tuning did not solve a strong hesitation at low gears and low load but that was solved with the "Tip in retard gear multiplier". Now the car 'only' has a jerk at load loads. It can really get into a oscillation and because the car is only 860kg it can be felt. Anybody has an idea how to make this more smooth? Anything else in attached file that I could change?
Re: Jerky car at low speeds/loads
Posted: Tue Jul 18, 2023 11:50 am
by Spunkster
Without a datalog showing the issue it is hard to say what it could be.
Re: Jerky car at low speeds/loads
Posted: Tue Jul 18, 2023 1:28 pm
by Flyingdutchman
Will try make one.
Re: Jerky car at low speeds/loads
Posted: Wed Jul 19, 2023 2:30 am
by Flyingdutchman
Spunkster wrote: Tue Jul 18, 2023 11:50 am
Without a datalog showing the issue it is hard to say what it could be.
See attached. The manoeuvre is in second gear >2000rpm, then throttle off down to 1000-1200rpm, then slowly back on the throttle. Its most obvious here but I can also feel it in higher gears. Seems most obvious after a throttle off and then slowly back on again.
Re: Jerky car at low speeds/loads
Posted: Wed Jul 19, 2023 11:18 am
by MondeCruel
Is your tps calibrate good ?
Re: Jerky car at low speeds/loads
Posted: Wed Jul 19, 2023 12:00 pm
by Flyingdutchman
MondeCruel wrote: Wed Jul 19, 2023 11:18 am
Is your tps calibrate good ?
Think so. Did the max and min calibration routine...
Re: Jerky car at low speeds/loads
Posted: Wed Jul 19, 2023 12:27 pm
by Spunkster
It may be the fueling as it is showing quite high short term fuel trims. Without a wideband it is not possible to see what the actual AF is reading.
Re: Jerky car at low speeds/loads
Posted: Thu Jul 20, 2023 12:41 am
by Flyingdutchman
Spunkster wrote: Wed Jul 19, 2023 12:27 pm
It may be the fueling as it is showing quite high short term fuel trims. Without a wideband it is not possible to see what the actual AF is reading.
Would checking "Disable fuel over-run cutoff delay" help? (Read it in and old post here)
Is it safe to check "Disable ignition retard when the engine is cold" also (As the issue seems worse when engine is cold....
Re: Jerky car at low speeds/loads
Posted: Thu Jul 20, 2023 5:04 am
by Flyingdutchman
Flyingdutchman wrote: Thu Jul 20, 2023 12:41 am
Spunkster wrote: Wed Jul 19, 2023 12:27 pm
It may be the fueling as it is showing quite high short term fuel trims. Without a wideband it is not possible to see what the actual AF is reading.
Would checking "Disable fuel over-run cutoff delay" help? (Read it in and old post here)
Is it safe to check "Disable ignition retard when the engine is cold" also (As the issue seems worse when engine is cold....
Hell, I went and tried this. Even though the tendency to oscillate is still there is feels much more damped, lower amplitude and easier to control. Almost acceptable.