V-Twin
Before I get the, "What throttle twitch?" questions from you lot, I better give you a short background story.

My 2016 Indian Chief Vintage with Stage 1 (S1) and High Flow Air Cleaner (AC) was smooth.  Then I had Stage 2 Cams (S2C) fitted at about 3,000kms and the 'very slight' throttle twitch emerged.  So what is a throttle twitch?

Best way to explain what I am talking about is to try it out on your own bike.

1/ Find a safe and quiet road where you can ride at slow speed. It would be best if the road is smooth.

2/ In 2nd gear, maintain 40kph as best you can as cruise control cannot be used.

3/ You may feel the throttle cutting off partially every few seconds.

I am naming this 'Throttle Twitch'. It happens at any speed in any gear but you might feel/notice more in lower gears/speed.

So what is the cause of this twitch?  Glad you asked.

The unlikely answer came when Power Vision CX (PVCX) was launched.  On the laptop with Power Vision software shows a 'Torque Table'.  On the PVCX website, the feature is listed as "Torque limiting functions reduced or eliminated".

On many other motorcycles (incl. Twin Cam Harleys), fly-by-throttle input is translated in percentage and that corresponding amount opens the butterfly inside the throttle body to let more air/fuel into the engine.  It may not be 1:1... that is, 25% throttle does not necessarily equal 25% butterfly opening.  Performance tune might be that 25% throttle equals 40% butterfly opening to give the feeling of responsiveness.  It would have been great if that is what Indian did...

Indian or rather Bosch Engine Control Unit (ECU) is VERY sophisticated and has something called 'Torque Table'.  Simply put, it is designed to limit the amount of torque our TS111 engines generate depending on several variables.  I can't recall exactly what they were but it was something like engine rpm, speed, gear, stuff like that.  So far, not many people have messed with it as it requires complex mathematical calculations.

Because of this torque table, I have witnessed another Indian TS111 on dyno (where the operator is trying to maintain a set speed, holding on to the throttle with two hands to prevent the accidental twist of wrist) which showed butterfly inside the throttle body twitch.  This was confirmed by the laptop hooked up to the bike.

I was incorrectly under the impression this 'throttle twitch' was due to cam profiles but it is in fact due to the ECU's torque table.  Could the torque table values be re-calculated and reprogrammed to smooth out the twitch?  Technically yes, but would anyone have the patience to do so?


UPDATE: 9 JANUARY 2017

After a feedback from a forum member, FaceOnHead, I tested my bike for the Throttle Twitching... it was gone.  I can only assume the latest Indian ECU software addressed this issue which had plagued me for many months.
Let's be kind to one another.
Melbourne, Victoria
Quote 1 0
charliebates

Hello V-Twin. I just installed the upgraded breather and V and Hines exhaust, then had the S2Cams dealer installed.

The engine performed perfectly through 1 tank of fuel until I installed the S2C and then I got all kinds of issues. Did a search last evening and you described my issues with absolute perfection.

In my case I expected the issue to be caused by the air cleaner because I designed and built it. To test I first did a ride without the breather outer cover and without the K7N air filter. It wasn't as bad.

 Next I installed the outer breather cover and ran without the K&N filter. Still an issue in fact a little worse.

 I placed my hand inside the air box while riding (no filter) and I felt the crank case ventilation pushing a rapid pulse of a lot of hot air.  That air was hot and was being pulled right into the throttle body intake and because the engine lopes at idle it was a pulse and I believe the on and off hot air was confusing the sensors and they were trying to compensate but resulted in the loping and jerking rhythm.  As a final test I pulled the crank case tube of the rocker cover and taped it up with black electrical tape, then installed the K&N and did the test ride. My issues are gone.  

 The engine ran perfect, no 2000-2100 rpm issues of loping and jerking and the idle works fine at 750 rpm. There's is a little irregular shake but that's to be expected with any upgraded cam.

 My issue is caused by the crankcase ventilation being too close to the throttle body intake.  I'll need to install an inner deflector cover to route it to fresh cool air on the inside of the breather backer plate. Once the hot air and cold air mix there shouldn't be a problem.  Or I can vent to the atmosphere directly using a filter.

You might want to check your location of the Crank case ventilation being too close to the throttle body intake.

IHTH John in Red Deer

 

Quote 2 0
crash
Very interesting.  I am going to try this at some point and see if I can replicate (my engine is stock)
Ulysses #30673
IMRG #AU100394
Current: RoadMaster (ebony and ivory)
Highett Victoria Australia
Quote 0 0
CHF10
[D35azEQ]
Live free or die!
Quote 1 0
V-Twin
I placed my hand inside the air box while riding (no filter) and I felt the crank case ventilation pushing a rapid pulse of a lot of hot air.  That air was hot and was being pulled right into the throttle body intake and because the engine lopes at idle it was a pulse and I believe the on and off hot air was confusing the sensors and they were trying to compensate but resulted in the loping and jerking rhythm.  As a final test I pulled the crank case tube of the rocker cover and taped it up with black electrical tape, then installed the K&N and did the test ride. My issues are gone.  
Hey John,

Awesome post mate and welcome to our forum.  What you describe makes perfect sense.  I always wondered what that black hose was doing behind the air cleaner.  I guess it needs filtered air as well... but the down side is, it is pumping the hot air in to the intake.  Very interesting!  Thanks for sharing your findings.

On my 2016 Vintage, with the latest factory tune from about 5 months ago (no new S2C tunes released in that time), my bike has been performing very well.  I haven’t tested this issue lately and have not come across a situation to replicate it so I cannot comment but good to know there is a possible fix.
Let's be kind to one another.
Melbourne, Victoria
Quote 0 0
CHF10
So what's described here makes perfect sense....... To some. But I have no idea what this is about. Should I be concerned about another issue with my bike? I don't have a clacker but am constantly worried my bike will turn into one. Now, should I be worried about it developing a twitchy throttle?

What the hell is a crank case tube and a rocker cover? (I know what black electrical tape and a K&N filter is) How the hell do you put you hand inside an airbox while riding? Won't it get sucked into the engine?
Live free or die!
Quote 2 0
V-Twin
CHF10 wrote:
Should I be concerned about another issue with my bike? I don't have a clacker but am constantly worried my bike will turn into one.
General comment re: clackering - if the noise bothers the owner, it is a problem.  If the noise does not bother them, it is not a problem.  Since both of my bikes clacked, I would say statistically speaking, a reasonable number of Indians probably clack but to varying degrees. 

Some engine builders tell us that piston slap will damage our engines over time, so who knows.  Is it better to not hear the sound or hear the sound and do something about it?  I guess that decision is up to the individuals.

When I first heard my bike clack, I didn't know anything about it (I have not read about it on any forum).  The noise was so out of place; it grabbed my attention.  Believe it or not, once you hear clacking, you cannot unhear it.

By comparison, throttle twitch is probably present on all, similarly configured bikes running the same tune?  Again, if other readers have not experienced this, it may be that their riding style or road condition does not take the bike into that zone required for this twitch to be experienced.  If you must test it, my original post lists how to conduct your own test.

CHF10 wrote:
What the hell is a crank case tube and a rocker cover?
Here is the picture of one.

breather-hose.jpg
Let's be kind to one another.
Melbourne, Victoria
Quote 1 0
Dr.Shifty
CHF10 wrote:
Now, should I be worried about it developing a twitchy throttle?

What the hell is a crank case tube and a rocker cover?


No, you shouldn't be worried.

The crank case breather tube vents pressure from underneath the pistons.

As the pistons rise and fall they rhythmically pressurize / depressurize the space below them. That space connects through the pushrod tubes (on right side of a TS111 motor) to the space above the valves at the top of the motor. The air in that space picks up a certain amount of oil vapour combined with any exhaust gas that creeps past the piston rings.

The rocker cover is the cover at the top of the motor where the tube comes out. The tube takes that polluted air and directs it into the stream of air going into the motor where it is burnt.

Air filter designs mostly include a 'still air box' where any turbulence in the air can calm down. This means the air flows evenly into the motor. Imagine a motor taking air directly from the outside but there is a gusty wind blowing into the motor. Gusty air speed changes would mean the motor is not getting air evenly and tuning etc would suffer. Modified and after-market filters often have no still air box and can be susceptible to fluctuations if there is too little enclosed air space.

The 1980s 4 cylinder Jap bikes were famous for not running well if the stock air filter was changed for four small individual cone filters.

What CharlieBates has described above is a pulsing air stream from the breather tube at low revs that badly effects the tuning. Moving that tube to a place where the pulsing has time and space to calm down is the fix.

It's not a problem at higher revs as the faster pulses lose themselves in the faster air flow.
Cheers, Kim.

From Woodrising (no, nobody else has heard of it either)
Rides a Springfield Dark Horse
Quote 2 0
CHF10
Ah OK. Thanks to both of you.

So if it's "waste" air, why is it being directed back into the air intake? Why doesn't it just get dumped? Furthermore, could this account for the low rev, low speed "lurching" every one of us experiences to varying degrees? Or is that simply a gearing and idle timing issue?
Live free or die!
Quote 0 0
Dr.Shifty
It's directed into the motor to burn because it's polluted with oil vapour etc. Older motors did vent it straight to the air.

My first car back in the 1960s had a straight out vent tube. They would often drip oil and as this became less acceptable they started piping it into the air filter flow. Some people vent it through a small dedicated filter, or a 'catch can' (popular with turbo sports car petrol heads), to catch any oil.

Old motors produce more oily air than newer motors because of piston ring design and build tolerance etc.

The low speed lurching is the anti-stall feature kicking in. The ECU doesn't like the revs to fall below certain limits at low speed as it thinks the motor is about to stall. So as the speed drops below it's inner limit the revs can actually increase. The answer is to change down or pull the clutch earlier. Some people tune it out of the ECU - another PVCX benefit.
Cheers, Kim.

From Woodrising (no, nobody else has heard of it either)
Rides a Springfield Dark Horse
Quote 2 0
CHF10
Yeah OK. Catch can time. I had catch cans on all my LS V8s.
Live free or die!
Quote 0 0
BigTone
CHF10 wrote:
[D35azEQ]

🤣🤣🤣
Cheers,
Tony
St. Kilda  Victoria
IMRG: 20380071
Current Ride: 2020 Dark Horse Challenger 
Previous Ride: 2015 Roadmaster
Quote 1 0
charliebates

V-Twin wrote:
General comment re: clackering - if the noise bothers the owner, it is a problem.  If the noise does not bother them, it is not a problem.  Since both of my bikes clacked, I would say statistically speaking, a reasonable number of Indians probably clack but to varying degrees. 

Some engine builders tell us that piston slap will damage our engines over time, so who knows.  Is it better to not hear the sound or hear the sound and do something about it?  I guess that decision is up to the individuals.

When I first heard my bike clack, I didn't know anything about it (I have not read about it on any forum).  The noise was so out of place; it grabbed my attention.  Believe it or not, once you hear clacking, you cannot unhear it.

By comparison, throttle twitch is probably present on all, similarly configured bikes running the same tune?  Again, if other readers have not experienced this, it may be that their riding style or road condition does not take the bike into that zone required for this twitch to be experienced.  If you must test it, my original post lists how to conduct your own test.

V-Twin wrote:
Here is the picture of one.

breather-hose.jpg
No automatic alt text available.Here's a picture to compare. My design pipes the crankcase discharge right beside the throttle body intake where as the Indian design is set way back and has distance for the hot air to mix with the fresh air.

 I'll need to install a diverter cover to send that hot air up front so it can mix properly.

Quote 1 0
charliebates

  For those interested here's a picture of the 02 Gilroy Chief War-bonnet Teardrop Breather installed on the 2014 Chieftain. I had to mount it 2 inches ahead  to get clearance at my knee and leg.

 I can post the build pictures it anyone is interested. I love building this stuff.

 Safe rides Mates!!!

No automatic alt text available.

Quote 2 0
V-Twin
I can post the build pictures it anyone is interested. I love building this stuff.
Of course, we would love to see your build pictures.  The air cleaner looks perfectly centred between two cylinders and makes the bike more unique.  Great work Charlie! 👍
Let's be kind to one another.
Melbourne, Victoria
Quote 1 0
CHF10
What's the wingnut on the floorboard for?
Live free or die!
Quote 1 0
BigTone
CHF10 wrote:
What's the wingnut on the floorboard for?

Looks? ðŸ˜…
Cheers,
Tony
St. Kilda  Victoria
IMRG: 20380071
Current Ride: 2020 Dark Horse Challenger 
Previous Ride: 2015 Roadmaster
Quote 1 0