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Measures of good idle 
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QFP80 - Contributor
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Joined: Thu Jun 20, 2013 4:24 pm
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Check these three options with the following conditions
You have a good idle when ∆ rpm is < ±50 rpm
You have a fair idle when ∆ rpm is < ±150 rpm
You have a bad idle when ∆ rpm is > ±150 rpm

• free idle quality at all coolant temperatures starting with the lowest to the fully warm engine temperature
• at free idle first apply and then remove all possible external loads
• at free idle, engine warm or cold, press the break pedal with 1Hz
• at free idle, engine warm or cold with power assisted steering, turn steering wheel to full lock, release then apply full lock again
• at free idle, engine warm or cold, blip the throttle, reach various engine speeds then leave engine returning to idle
• previous point but with external loads

Check these three options with the following conditions
You have a good idle when ∆ rpm is < ±100 rpm
You have a fair idle when ∆ rpm is < ±200 rpm
You have a bad idle when ∆ rpm is > ±200 rpm

• from free idle, hot or cold engine, first and second gear, pull away with no throttle then abort pull away or de-clutch
• in idle drive, engine warm or cold, first and second gear (car should not feel incontrollable due to increasing engine speed)

Following conditions are time-dependent
• in idle drive, engine warm or cold, first and second gear, press brake to drop engine speed to 500 rpm then release, engine should not stall and recover quickly without overshoot, oscillations or surge
• at idle drive, engine warm or cold, apply external loads, there should be no disturbance
• in idle drive, engine warm or cold, after and while car parking manoeuvres engine should not stall and recover quickly without overshoot, oscillations or surge


Sat Jun 21, 2014 8:57 pm
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Your idea of a "good idle" and mine are VERY different.

Having said that, my pile of shit, which I consider to have a bad idle, has, according to your specification, a fair idle. With no idle air control at all, it will hold 900 RPM after just 30 seconds or so of holding it at 2k, and then it never exceeds 1200 while driving. I think this is terrible, personally, but falls into your +/- 150 spec. It also has a variable throttle closed position LOL. Hence the hot variance. If I fixed that it'd be totally stable outside of external loads. External loads don't change the hot RPM more than about 100 RPM anyway.

ruzki wrote:
at free idle, engine warm or cold with power assisted steering, turn steering wheel to full lock, release then apply full lock again

I'd also like to point out to those not so mechanically inclined that this is a fucking terrible idea and can/will damage your power steering pump. Do not do this.

Some of your specifications that say "good" to me say "horrible". You're WAY outside the realm of talking about an engine idling and instead talking about warranty avoidance measures. I highly recommend driving an old car some time, just for the experience :-)

Best idle, other than vibration, to me, comes from old fashioned diesels with mechanical pumps.

And worst? New diesels with electronic control and brain-dead software developers.

Fred.

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Sun Jun 22, 2014 12:11 am
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QFP80 - Contributor
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Fred wrote:
I'd also like to point out to those not so mechanically inclined that this is a fucking terrible idea and can/will damage your power steering pump. Do not do this.

Ahh Fred this is not true, if so every housewife would break the car every time she goes for shopping in the local market LOL :D
Systems like this always have a overpressure valve ..

Fred wrote:
Some of your specifications that say "good" to me say "horrible". You're WAY outside the realm of talking about an engine idling and instead talking about warranty avoidance measures.

This sentence is irrelevant because of no technical background
As well as the next ..
Fred wrote:
I highly recommend driving an old car some time, just for the experience :-)

Really ! are serious ! OK ! actually i do quite often .. but only russian ones LOL :lol2:
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aannnd
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Fred wrote:
Best idle, other than vibration, to me, comes from old fashioned diesels with mechanical pumps.

And worst? New diesels with electronic control and brain-dead software developers.

This is your opinion wich i do not share .. but i can accept it ..

Anyway as the free in FreeEms may suggest, should not every user have the possibility to adjust the idle as wanted ???
And should a FreeEms provide this possibility ??


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Sun Jun 22, 2014 1:34 am
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ruzki wrote:
Fred wrote:
I'd also like to point out to those not so mechanically inclined that this is a fucking terrible idea and can/will damage your power steering pump. Do not do this.
Ahh Fred this is not true, if so every housewife would break the car every time she goes for shopping in the local market LOL :D
Systems like this always have a overpressure valve ..

Yes, they all do have those. I bet I could seize your pump in under 5 minutes if you allow me the opportunity. I know exactly how they work and have killed one this way in under 3 minutes ;-)

It's true that it won't damage the pump for a short test. But it's still not wise, nor a nice thing to do to your pump. IF you care about it.

I might have some photos of what it did somewhere, but don't hold your breath waiting.

Once again, to the mechanically inept: DO NOT DO THIS! You've been warned.

Quote:
Fred wrote:
Some of your specifications that say "good" to me say "horrible". You're WAY outside the realm of talking about an engine idling and instead talking about warranty avoidance measures.
This sentence is irrelevant because of no technical background

What? I think some of the behaviours you described are HIGHLY undesirable and unpleasant for the driver. I totally agree with others, though. Your arbitrary thresholds of RPM tolerance are exactly that: arbitrary, but they're pretty reasonable, really. As for no technical background: It's easy to argue that the engine isn't actually idling at all when it's under accessory load. Just think ahead to a genset and reach the natural conclusion. It's just nomenclature at this point though.

Quote:
Fred wrote:
I highly recommend driving an old car some time, just for the experience :-)
Really ! are serious ! OK ! actually i do quite often .. but only russian ones LOL :lol2:

I was serious, however it looks like you just have a vastly different style and preference. So be it.

Quote:
Fred wrote:
Best idle, other than vibration, to me, comes from old fashioned diesels with mechanical pumps.

And worst? New diesels with electronic control and brain-dead software developers.
This is your opinion wich i do not share .. but i can accept it ..

I dislike vehicles that burn excess fuel while being lugged, and burn excess brakepad while being lugged, and worst, that try to launch you into the back of the car in front when you get off the brake because they're applying significant torque to your driveline to try to maintain that golden and irrelevant idle RPM. Modern diesels are HORRIBLE like this. I've experienced this in multiple brands, too. Maybe euro petrols are similar with their grossly oversized idle valves for the low engine displacement they tend to have? My old R32 Skyline was reasonable in this respect, though it tried to overcome your desire, it didn't try very hard, because the idle valve was sized appropriately and max air flow wasn't much. And yes, this was my opinion, OF COURSE, as yours is stated in the first post. Was there any statement from either side to suggest it was some sort of fact or gospel? No, just opinion. I accept yours as yours and you mine as mine. Cool.

Quote:
Anyway as the free in FreeEms may suggest, should not every user have the possibility to adjust the idle as wanted ???
And should a FreeEms provide this possibility ??

Free in FreeEMS means Libre, not Gratis. It means you're free to do with the source what you want within the terms of the GPL V3. It doesn't mean much more than that :-)

"Good" idle control will be available at some point. If it doesn't meet your needs, you're free to change it to suit. If "some point" is too far away, you're free to implement it to suit, too. As for every user as wanted, this implies keeping everyone happy, which is a fool's errand. I don't want to try and the result of trying is almost always a dirty mess. Please most of the people most of the time, and you're doing well for everyone.

Fred.

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Sun Jun 22, 2014 3:25 am
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QFP80 - Contributor
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Fred wrote:
I dislike vehicles that burn excess fuel while being lugged, and burn excess brakepad while being lugged

But that´s what the N-position is for !

Fred wrote:
and worst, that try to launch you into the back of the car in front when you get off the brake because they're applying significant torque to your driveline to try to maintain that golden and irrelevant idle RPM

Thats what i absolutely love the automatic transmission for .. it is great for driving in the city or when you sit in traffic .. it removes the delay out of the automatic transmission and your reaction. Otherwise you put your foot off the brake and put it on the gas pedal that needs one second then you push the gas pedal, now the transmission needs one second to launch ... a absolutely boring driving .. like a grandfather :lol:

https://www.youtube.com/watch?v=o8PCtB1SMvg

Fred wrote:
Please most of the people most of the time, and you're doing well for everyone.


I wonder what the others in this forum think ...


Sun Jun 22, 2014 1:12 pm
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ruzki wrote:
Fred wrote:
I dislike vehicles that burn excess fuel while being lugged, and burn excess brakepad while being lugged
But that´s what the N-position is for !

That's your opinion, and you're entitled to it, however I strongly disagree.

Quote:
Fred wrote:
and worst, that try to launch you into the back of the car in front when you get off the brake because they're applying significant torque to your driveline to try to maintain that golden and irrelevant idle RPM
Thats what i absolutely love the automatic transmission for

As a citizen of the EU you should be ashamed of your self for mentioning the A word :-p Besides, well behaved cars do not have this problem. Not even my old skyline with its perfect idle and closed loop idle control had this issue, really. But old and un-closed-loop controlled cars just behave better, period. PS, I don't just do this in 1st gear, I do it in other gears too!

Quote:
https://www.youtube.com/watch?v=o8PCtB1SMvg

ROFL :-)

ruzki wrote:
Fred wrote:
Please most of the people most of the time, and you're doing well for everyone.
I wonder what the others in this forum think ...

Probably that we're not pleasing anyone much any of the time? :-D Yet! I did some work last night for you. Will find some trusted testers before I publish it, though.

Fred.

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Sun Jun 22, 2014 8:40 pm
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QFP80 - Contributor
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for me a good idle is the when you reach the rpm +-40rpm and fair irdle +-70, otherwise than that is bad for me (as my M$1 closed loop system which sometimes varies around 100 rpm and I don't like and it's slow)

about the "resistance" to stunt the engine, I don't like as much as VAG tdi style, but I like a little of resistance.

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Tue Jun 24, 2014 11:06 pm
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Good to hear, Aitor! :-)

I personally believe that an engine under load should exhibit some signs that it's under load, and a lower than normal RPM is that sign. This doesn't apply to AC, though, which is too large of a load to reasonably handle without some help. Keeping it artificially high under load (eg flat battery post jump) seems to me a lot like sticking your fingers in your ears and singing la la la while someone is speaking to you :-)

Fred.

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FreeEMS.org - the open source engine management system
FreeEMS dev diary and its comments thread and my turbo truck!
n00bs, do NOT PM or email tech questions! Use the forum!
The ever growing list of FreeEMS success stories!


Wed Jun 25, 2014 12:28 am
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