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Idle-to-throttle transition

Practical Standalone Tuning

Relevant Module: HPA 10 Step Process > Step 6: Idle Tuning > Idle Speed Control Settings

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I'm having trouble smoothing the transition from idle to throttle. It almost seems like my throttle response is too sensitive. Car idles quite rich ~.85lambda. When i touch the throttle for maybe 6-9% tps, it bogs a little and then rpm jumps to 2-3k.

Im tuning ecumaster black, Bmw m52tub25. Pretty much stock engine with m54b30 intake and diy cable throttle and stock idle valve. Car is driveable but always needs some pumping on the gas when i get going.



Is there a reason you are idling at .85 Lambda? That car should be just fine at Lambda 1.0.

Do you have any kind of progressive scroll pulley for your cable throttle. Often that is used to get reduced throttle angle response off of idle particularly needed for individual throttle bodies.

Somewhy it's been difficult to tune that idle ve table.. i do not have any pulley for the cable. It is routed that it at least feels really smooth. Maybe i should consider using some kinda pulley. Thought it would work

It may be how you've set up the mapping cells for position and/or rpm.

It's normal practice to concentrate them more at the lowest opening position and progressively spread them out as the throttle is opened - this is because at low throttle openings, such as just off idle, a degree of opening has a MUCH bigger change in airflow than the last degree at full opening.

I suspect your problem is the fuelling is not following the airmass entering the engine.

As David said, I would also expect a good, stable idle should be attainable at lambda 1.0, or even a little leaner.

You may also be suffering from a poor throttle linkage/alignment and/or sticking cable. For the latter, different folks have different remedies - I've had good success with removing the cable assembly and, with it suspended by one end, working the cable/sleeve up and down while slowly working a plastic-friendly (most use a nylon/plastic liner) electrical cleaner fluid through it then, when that's dry (blowing air through it can help), I use a dry, silicone or similar, lubricant worked through it.

It can make a significant improvement, especially with older cables.

So if you're not using a pulley for the throttle end, are you just using a simple arm? 80+ degrees of throttle travel will give you non-linear response for your few degrees of pedal travel (which will be almost linear). That's why wrapping the cable around a round pulley, will give the same motion angle wise as the pedal, and a scroll-type can allow it to be increasing with more throttle, which is what you want with individual throttles.


Thank you for your answers! I think i found the problem.. my idle valve was wired incorrectly. All i had to do was reverse the signal and with some fine tuning i managed to get the car response how it's supposed to. Also some tuning on the ve table at idle area was needed.. however it still makes me figure why did the car work all summer. Now that it got below freezing temperatures the car started acting up

Well, i guess you learn something everyday. It's only my first year tuning..


Colder air = More density = More fuel needed to start and run. It may be that the warmer temperatures allowed for the fuel to vapourise enough that it could run, along with the air being less dense so needed a lower fuel quantity to be injected to maintain the required lambda value for combustion. When it gets cooler, there is less fuel vapourisation so it stays in droplet form for longer, this is less prone to ignition and needs to be compensated for in your transient behavior.

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