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 Post subject: Rough idle
PostPosted: Wed Jun 19, 2019 5:08 pm 
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Joined: Mon Jan 16, 2012 1:39 pm
Posts: 119
ECU Model: S40 Pro
Firmware Version: 58
i have notice in some engines not all of them that when the engine is cold and the weather also cold lets say 10 degrees water 5 degrees air temp, the engine fires up and runs but in some cases it runs rough, the same engine with warmer weather it runs fine...

i am pretty sure that cold intake runners make gasoline droplets and thats why it runs rough like old days with carburattors that they used heat from exhaust manifold, can i do something to fix it because the same engine but with the OEM ecu works fine...any ideas ?


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 Post subject: Re: Rough idle
PostPosted: Thu Jun 20, 2019 11:58 am 
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Joined: Tue Aug 02, 2011 12:08 pm
Posts: 2987
Location: Norn Iron
ECU Model: No ECU
Tune it better ?

Often they run better when cold because they'll be a little richer.

But without knowing what you're doing with tuning or the build when cold vs when hot....hard to advise how to correct it.


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 Post subject: Re: Rough idle
PostPosted: Thu Jun 20, 2019 12:59 pm 
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Joined: Thu Jul 28, 2011 4:10 am
Posts: 928
ECU Model: S100 Pro
Distributor: None-Coil On Plug :)
Need to know more about your set up.
I use idle by ignition and works very well even sub zero starts.
If your hot idle is Bob on, use a knobs box to fine tune the warm up enrichment as it moves through the turns table


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 Post subject: Re: Rough idle
PostPosted: Fri Jun 21, 2019 3:44 am 
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Joined: Mon Jan 16, 2012 1:39 pm
Posts: 119
ECU Model: S40 Pro
Firmware Version: 58
its very good tuned at least at idle, i use advance for idle too...i did not explain it very well, idle is stable...engine sounds rough when its really cold that why i am pretty sure that gasoline droplets on cold intake runners has something to do also the very light bottom end make things worse, its 12kg lighter than stock...thanks both of you


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 Post subject: Re: Rough idle
PostPosted: Sat Jun 22, 2019 4:49 am 
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Joined: Sun Jan 27, 2013 6:08 pm
Posts: 284
ECU Model: S60 Pro
Firmware Version: 29
A light flywheel / clutch is never going to idle as smoothly as a heavy one - period. If the gas speed is low enough to allow condensation on the inlet runners i'd increase the 'cold' idle speed just like the 'old skool' choke mechanism with carbs - this can then decay against ET back to normal idle at running temps?


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 Post subject: Re: Rough idle
PostPosted: Sat Jun 22, 2019 4:40 pm 
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Joined: Mon Jan 16, 2012 1:39 pm
Posts: 119
ECU Model: S40 Pro
Firmware Version: 58
i am glad hearing that because the only thing i found to make it better is to have 1200rpm cold idle and when water temp goes over 60 drop it at 1000rpm, below 1000rpm its really bumpy even engine is hot...it has not aggressive cams at all, it has a fast road cam with 221 degrees at 1mm lift...so the bumpy effect is from the very light bottom end


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 Post subject: Re: Rough idle
PostPosted: Sun Jun 23, 2019 3:33 am 
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Joined: Thu Jul 28, 2011 4:10 am
Posts: 928
ECU Model: S100 Pro
Distributor: None-Coil On Plug :)
But you said it is fine on the OEM ecu


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 Post subject: Re: Rough idle
PostPosted: Sun Jun 23, 2019 5:21 am 
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Joined: Mon Jan 16, 2012 1:39 pm
Posts: 119
ECU Model: S40 Pro
Firmware Version: 58
yes thats true...but then i remember that the oem ecu has the oem crankshaft and flywheel that is 12kg more in weight that the ones that is installed now on the engine...so i have not try the the oem ecu with 12kg less rotating mass


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 Post subject: Re: Rough idle
PostPosted: Sun Jun 23, 2019 6:38 am 
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Joined: Sun Jan 27, 2013 6:08 pm
Posts: 284
ECU Model: S60 Pro
Firmware Version: 29
Also the idle timing could be a little too advanced so building more cylinder pressure than the light flywheel can compensate for?


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 Post subject: Re: Rough idle
PostPosted: Sun Jun 23, 2019 10:43 am 
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Joined: Mon Jan 16, 2012 1:39 pm
Posts: 119
ECU Model: S40 Pro
Firmware Version: 58
the problem is not the stable idle, the problem is that the engine sounds running rough on really cold weather at start up, something that is not happening on warm weather, thats why i believe that gasoline droplets on cold intake runners make that rough engine sound as it stops sounds like that when the engine becomes hotter...and yes more advance timing and more rpm at cold start up help a lot...

also something i notice 20ms injector start pulse are a lot on hot weather but fine for cold weather..it could be very helpful the ability to have more settings on start pulse via degrees (cold/hot)


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