Rev limiter Fuel

[hkshooper]

I have a tts and my question is when the Harley EFI hits the rev limiter does it pull fuel or does it change timing.

[rbabos]

I have a tts and my question is when the Harley EFI hits the rev limiter does it pull fuel or does it change timing.

Fuel
Ron

[whittlebeast]

Be careful asking questions and thinking thru the Harley rev limiter logic.  If you consider what happens when you shut off fuel to one cylinder in a Y intake manifold when injector the other is spraying at close to 80% duty cycle, what happens to that fuel and what cylinder does it end up in?

People may start using caps lock when replying for even asking  the question.

Just thinking out loud.....

Andy

[KE5RBD]

I know it cuts the spark intermittently as much as necessary to maintain the rpms at the rev limit.  i think it will cut the injector at same time.  The injector sprays directly at the valve so very little fuel would get into the skipfire cylinder.  I know the rev limiter on carbed auto engines can only cut fire and they would pop really bad.  The Harley doesn't really pop when it hits rev limiter.  It just jumps and jerks. I try not to hit it. You can set your rev limit lower and run a Data log and see what all it shuts off.   

[Gwaxley]

is the rev limiter set at a lower value on a new bike? and harley will set it higher at the 1000 mile service?

[whittlebeast]

It has been a long time since it messed with Harleys so I am going to go from memory here...  look at the pulse width of the front cylinder compared to the rear cylinder.  Something like 60 percent of the fuel comes out of one injector.  I am fairly sure 60% of the power does not come out of one cylinder.  The fuel gets shared in a big way in the intake.

Watch both of the O2s when you hit the rev limiter.  Now try the experiment with pc5 data logging what yo have 60 samples per sec on a pair of wideands.  It is the AFRs in the cylinder that is still making power I worried about.

Andy

[joe_lyons]

is the rev limiter set at a lower value on a new bike? and harley will set it higher at the 1000 mile service?

Nope, 5750 for a stock flash.

[Gwaxley]

is the rev limiter set at a lower value on a new bike? and harley will set it higher at the 1000 mile service?

Nope, 5750 for a stock flash.

darn it...think i remember hitting it by accident before 1000mile service...wasn't looking at tach...apparently it didn't hurt anything, just curious, thanks joe..

[hkshooper]

Reason i asked is i was looking at log and when it gets to rev limit it cuts fuel, but isn't dropping timing like every rev limiter i know. It is adding a bunch of timing and it scared the crap out it.

[glens]

It's probably cutting fuel because there's no spark at times.  I'm sure it's not merely limiting fuel as a means of speed control.  Think about it.  How lean would that burn if it got lit?

Compared to the number of sparks (or not, as the case may be) going on, the data rate of the log file is so low you'd have to be pretty lucky to catch much of it happening anyway.

[FLTRI]

It's probably cutting fuel because there's no spark at times.  I'm sure it's not merely limiting fuel as a means of speed control.  Think about it.  How lean would that burn if it got lit?

Compared to the number of sparks (or not, as the case may be) going on, the data rate of the log file is so low you'd have to be pretty lucky to catch much of it happening anyway.

👍👍
Bob

[Admiral Akbar]

It's probably cutting fuel because there's no spark at times.  I'm sure it's not merely limiting fuel as a means of speed control.  Think about it.  How lean would that burn if it got lit?

Compared to the number of sparks (or not, as the case may be) going on, the data rate of the log file is so low you'd have to be pretty lucky to catch much of it happening anyway.

If it cuts the fuel completely, there is nothing to burn.. No reason to jest lean it out a little.. Since fuel is delivered specifically for each cycle, the PW is probably cut to 0 if over the rev limit and started back up to full fuel as some as the Rs are below the rev limit... Probably some hysteresis one the R where the events occur.

[glens]

... Probably some hysteresis ...

Yeah, it's funny how that works.   ( Hysterical hysteresis :-)

I don't know just how TTS does it, but do recall that, at least early on, the PowerVision would generate some interesting log files.  It seemed that the requested data "channels" did not each get updated for every time slice in the log file, instead arriving in sub-groups.  With last-known values being carried forward in the file it was not uncommon at all to find seemingly unlikely scenarios being presented.

There's simply not enough true resolution in this mechanism to get to the very bottom of some things.

[hrdtail78]

The vision and TTS have different strategies when it comes to logging data.  You can clearly see in this data log that it is cutting fuel.  I take every thing away and just show the trace for front  IPW, RPM, analog 1, and TPS%.  Right click and blow up just one WOT.

https://app.box.com/s/e5rrf326uwj1uzxy9uav7740dwwmoecz

[glens]

Cool.  Too bad it don't indicate spark event enable/disable...  (Not talking "advance" value - a different matter and /don't/ matter if a signal to the coil is entirely omitted.)

To be kind, I think I remember getting the impression that the PV was trying to be "faster" than the competition and that I didn't consider it to be very-well implemented.

[hrdtail78]

IMO, Dynojet marketing doesn't have a good track record, but that isn't a topic for this site.

The data stream and it's packages and how it all gets recorded is a very interesting topic.  CANbus is extremely fast.  There doesn't seem to be a reason to collect smaller packages of data.  Such as spark data in the 1850's.  The manufacture needs to decide what is important to update at 40 frames per second and what doesn't need that type of resolution.  Carrying forward engine temp, yes.  Spark event, no.

[Jamie Long]

I have a tts and my question is when the Harley EFI hits the rev limiter does it pull fuel or does it change timing.

Cant speak for how the company you are referring to does it specifically, however depending on the which specific HD-Delphi ECM and calibration level you are working with there around half a dozen tables for RPM limit strategy that affect fuel, spark, and throttle blade on TBW models

[Steve Cole]

I have a tts and my question is when the Harley EFI hits the rev limiter does it pull fuel or does it change timing.

Cant speak for how the company you are referring to does it specifically, however depending on the which specific HD-Delphi ECM and calibration level you are working with there around half a dozen tables for RPM limit strategy that affect fuel, spark, and throttle blade on TBW models

Boy, talking in circles again! Delphi is the one that controls the Rev Limiter operation, NOT TTS, DJ, SESPT or anyone else. Delphi ALWAYS cuts fuel for the Rev Limiter and has done it since the first Delphi HD ECM in 2001 to the current 2015 ECM's in ALL calibration levels. There are no tables for REV Limiter that control the throttle blade but there is torque management that does. If you have high speed data (like DataMaster data) you will also see that it ALWAYS cuts one cylinder first and then the second cylinder as necessary.

[glens]

Is it merely cutting fuel, or is it in conjunction with spark control?

[Admiral Akbar]

Is it merely cutting fuel, or is it in conjunction with spark control?

Why cut the spark?  Do you need to?  On a carbed bike, spark is the only way but EFI?

[glens]

Dunno.  Maybe some fuel might wind up in the chamber anyway?

The Pill works pretty good, and so does a vasectomy, together they're about as sure-fire as you'll get if you want to maintain your operational boundaries.

I'm just wondering, mostly.  I know if it were up to me I'd be cutting the spark first, then fuel too just to keep it elegant.

[hrdtail78]

You need Datamaster2 v3.0.0 to open the file I posted

I haven't seen where it is cutting spark in the logs I have reviewed.  I can see where keeping spark active might be a good idea to clean up the left over fuel and to prevent pop.  ??

[Admiral Akbar]

Dunno.  Maybe some fuel might wind up in the chamber anyway?

The Pill works pretty good, and so does a vasectomy, together they're about as sure-fire as you'll get if you want to maintain your operational boundaries.

I'm just wondering, mostly.  I know if it were up to me I'd be cutting the spark first, then fuel too just to keep it elegant.

If fuel is getting into the cylinder there is something wrong with the system... Leaky injector?  Why cut spark and dump fuel into the exhaust system.. Like the backfire when the sparks starts back up?

[glens]

Hence the mention of "elegance" in my post...

Leaky injector or a short shared intake?  Maybe just pulling fuel will suffice to nicely keep revs in check.  Pulling spark definitely will.  Then pulling fuel will keep things clean and quiet and that's all it needs to be depended upon for.

[Admiral Akbar]

Hence the mention of "elegance" in my post...

Leaky injector or a short shared intake?  Maybe just pulling fuel will suffice to nicely keep revs in check.  Pulling spark definitely will.  Then pulling fuel will keep things clean and quiet and that's all it needs to be depended upon for.

Why not cut the fuel to both injectors?