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Old Member
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2,896 Posts
Discussion Starter #1
Why do harley efi's have to idle at around 1100 rpm's ?
What would happen if you dropped it to around 7-800...
 

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COB
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1,984 Posts
Why not? My old 76 FLH idled so slow you would swear it would die, no oil pressure problems. Is this something specific with the Twin Cam? I know it is not with the Evolution and I though the Twin Cam got the good oil pump. I tried to set my idle lower on my vrod and it did not like to run. One thing I did not like about my 05 FXSTI was the high idle. Just doesn't sound as good.
 

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2007 Ultra Classic
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1,285 Posts
The new engines with the EFI don't like it.

I used to idle down the older carb bikes for the true potato, potato sound, but the new ones are going to be a problem.
 

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Registered
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411 Posts
It is not an oil pressure related issue whatsoever!!!

Its a charging issue - the fuel injection system and ECM require a good strong supply of 12.8V min. Long periods of low idle can cause battery voltage to drop below this, and not supply the necessary power to the system. Hence the higher idle to ensure constant and consistent higher voltage from the charging system.
 

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Just passing thru
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6,636 Posts
It is not an oil pressure related issue whatsoever!!!

Its a charging issue - the fuel injection system and ECM require a good strong supply of 12.8V min. Long periods of low idle can cause battery voltage to drop below this, and not supply the necessary power to the system. Hence the higher idle to ensure constant and consistent higher voltage from the charging system.
Makes perfect sense. Now is there a way to get more voltage at a lower RPM? After market something or other?
 

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Old Member
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2,896 Posts
Discussion Starter #7
My friends victory vegas is fuel injected and idles at around 700 RPM and he never has any problems with his bike ??????
 

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On a ride
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4,996 Posts
It is not an oil pressure related issue whatsoever!!!

Its a charging issue - the fuel injection system and ECM require a good strong supply of 12.8V min. Long periods of low idle can cause battery voltage to drop below this, and not supply the necessary power to the system. Hence the higher idle to ensure constant and consistent higher voltage from the charging system.
Never knew this!
 

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Registered
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411 Posts
The idle can be lowered to around 700-800rpm, I think thats about the limit predetermined in the ECM programming.

This lower idle shouldnt create any issues - other than the battery voltage getting low at longer periods of idle.
 

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COB
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1,984 Posts
The bike must be taken to the dealer and put on the HD "Scanalyzer".
I can do it with my SERT. There is an "idle" setting. But when you do it runs like crap and will stall off the line more. Dunno why.
 

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I {Heart} Hookers.
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31,321 Posts
It is not an oil pressure related issue whatsoever!!!

Its a charging issue - the fuel injection system and ECM require a good strong supply of 12.8V min. Long periods of low idle can cause battery voltage to drop below this, and not supply the necessary power to the system. Hence the higher idle to ensure constant and consistent higher voltage from the charging system.

Correct....for Fuel injected bikes only. Carbed can be run as low as 850-900.

Delphi EFI needs 1000 rpm +- a few to properly run, especially to keep up the necessary fuel PSI to run the bike, via the electric fuel pump. Anything less than 900 rpms, the battery begins to discharge because the electrical system is now based on RPMs AND electric needed, unlike my 1995, which produces 100% all the time, and bleeds the rest off from the regulator.

The new electrical system (199* or newer) causes longer regulator life, and frees up 2-3 horsepower due to reduced drag......

HOWEVER... The proper idle speed for Big Twin engines is 900-1000 RPMs.

EVO oiling systems need better than 700 RPM to work properly. It may sound good, at a lower idle, but improper oiling will contribute to engine overheating while idling in traffic and premature engine failures as it creates low oil scavenging issues with a stock oil pump.

Since 1999, the sump has been redesigned to reduce pressure buildup from the movement of the larger pistons. Reduced pressure buildup reduces the chances of oil being pushed through a loose base gasket. And the new oil pump puts a pressurized spray onto the bottom of the pistons. Along with lubrication, this also provides a more even cooling. No more hot running rear cylinder.
 

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I dropped my RPM's on my 99' Glide classic down to 800 a while back, didnt like dropping into first and "clunking" so hard. So far so good, I agree, long periods of idle would not be good for the system. Good thing I dont spend too much time showing off, and plenty of time ridin' !!
 

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EFFE
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501 Posts
Any tips on how to adjust it, or a website to go to?
 

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I {Heart} Hookers.
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31,321 Posts
Any tips on how to adjust it, or a website to go to?
Google it. Or....wait till morning and ask Schmidty. He's good with the MM EFI bikes.
 

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Retired citizen
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24,076 Posts
To properly setup the Magneti-Marelli EFI a Scanalyzer or Digital Technician and breakout box is needed . I've seen the systems so badly misadjusted that it took a couple hours to get them corrected . On some occasions it's not even the throttle body that's out of adjustment , one or more sensors out of parameters can affect the system .
The Delphi EFI systems have to be adjusted with a Scanalyzer or Digital Tech. . The idles are set electronically . 950 RPMs minimum and (I think ) 1150 max . Also only adjustable when the engine has reached operating temp. .
 
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