From what I have learned with the benchmark work we have done on V-Twin engines at work for other bike makers...

The cam timing that is used with EFI combined with the higher idle used to feed the TC engine with enough oil pressure to live at idle are the biggest reasons for the HD sound change.

The older engines could tolerate a 650 RPM idle and survive darn near on splash oiling. The new ones won't take it.

But you are correct, the two things you assumed should give the potato sound based on design alone. But on a factory bike, due to EPA regs, the loss of the sound is a by product of the things I mentioned. New cams and some EFI tuning and I bet even the oldest of carb tuners would be happy with the sound. JUST DON'T TURN THE IDLE DOWN ALONE FOR THE SAKE OF THE SOUND! You'll hurt the cams.

 

Hey beagle while were on the subject what is the lowest you would want to go with an 06s idle speed. And thanks for al the good reading so far.

 

I've got 2 FI bikes and 2 carb bikes. I'm with ride99, gravity ain't broke down since they invented it. FI is OK on my touring bikes and OK on crotch rockets. But when it comes to my WG and ST, gimme' some taters with my meat, I ain't on no low carb, no carb diet.

 

Talked to the guys at work that ran the TC 88 efi engine. They said they has a spec of 8 psi minimum at idle, that was using the factory 950 RPM idle spec. They never got below 10 psi.

So for a crude method, you could install a manual gauge and decrease your idle until it is about 8 psi...I'd do this with old very hot oil just before a change. Then you'd have a little comfort zone, but plenty of pressure with new oil. Keep in mind that you need to only adjust the cells in the tables that coorespond to the temp you are at (engine operating temp). If you "flat mapped" the whole thing -XX% you would have hard start issues, mainly cold, and then would have to tweak the IAC table.

Personally, I only dropped mine to 850 RPM, all I was comfortable with before today's new found info. But I may do what I suggested above next year when it gets hot outside again.

I also got an education on the TC 88 oil system. There still is some misting and splash involved. But the area of concern with low idle oil pressure at idle (if I remember what they told me) is the cam thrust plates?

I will admit I AM NOT AN HD engine guru by any means. So please, no one take any info I give as gospel. I will almost always share what I have been told if it's from a positive source, and I also will share what I personally have done or experienced. You should never read something from me that "I heard from someone with a buddy who has a cousin with a friend that did this or that". I can built the crap out of a 2 stroke or a car engine, turbo or not. I am still learning the inner workings of the HDs, but at least for now I have a source for info at times.

 

How come the idle is set so high stock, i think mine was 1150 or 1200 before i installed the sert. If memory serves me right i believe that 987 was the lowset the sert would let me go, but i am a complete beginer with tunning.

 

Is that at the right temp? 1248 RPM is warm up speed. Someone missed the cal at the factory if you were over 950 RPM at full temp. Or you had a vacuum leak.

You should be able to get to at least down to 800 RPM at full temp with the Idle Table, then lower with the IAC table. Make sure you are in advanced mode though. NOT ALL CAL FILES ALLOW THIS though. It depends on the file for the Model/Year.

 

Thats the warmed up idle im talking about. When i played with it last i dropped the warm up idle down a bit and i took my idle down to 1008. Ive got an 06 fxdbi. I will plug the sert in tonight and see.

 

What's not to like!

 

E-mail me your cal file and where you have problems. Me & my dyno buddies can have a look for things that don't seem right.

1008 RPM is to high from the factory. You may have a manifold leak if you have commanded in the SERT to the lowest idle and it can not achieve it.

 

I just checked and from what i can tell the lowest rpm is 904 at 196 degrees, i havnt touched this map it was given to me by another HDF member.