Rev limiter Fuel

[glens]

Are you trying to kill the engine back to safe revs where it gets a flying re-start or instead keep it running but not gain any more speed?

[whittlebeast]

I wonder why they don't simply use the DBW and prediction to take care of the issue?   That would soften things right up.

[Admiral Akbar]

Are you trying to kill the engine back to safe revs where it gets a flying re-start or instead keep it running but not gain any more speed?

Well it's not a jet engine.Cutting feul ain't gonna require a restart.

[hrdtail78]

Are you trying to kill the engine back to safe revs where it gets a flying re-start or instead keep it running but not gain any more speed?

Well it's not a jet engine.Cutting feul ain't gonna require a restart.

Look at deceleration injector fuel cut off.

[FLTRI]

I wonder why they don't simply use the DBW and prediction to take care of the issue?   That would soften things right up.

Well, that would take software that would see acceleration rate and predict when and how much the throttle needed to be cut in order to keep the engine from going past the limit.
Way more easy to cut fuel a bit before the limit.
Bob

[whittlebeast]

Rev limiter logic is really fairly complicated.  Low cylinder counts makes the options fairly limited.  Prediction and torque limiting is often used.  Total misfire tends to be hard on cranks not to mention dropping 50% torque can upset the ballance of the vehicle.

One of the most difficult setups to learn to race is a motor that pulls hard right to an aggressive rev limiter.  It is impossible to time when you most need perfect timing.   I have run into instructing people with modified turbo STI race cars and it was a nightmare to keep the student from finding the rev limiter at the worst possible time.

When I am helping someone set up a new motor, I like to have the motor set up to rev about 1000 rpm above where the motor wants to pull hard.

Easy may not be the best option.

Andy

[whittlebeast]

Here is a plot showing both cylinder going dangerously lean as the motor bangs off the rev limiter.  Note that this pull was at 80% throttle.

One of the cylinders went way lean at 4500 RPM in the sweep.

http://www.nbs-stl.com/HarleyTuning/TTS%20Tune%2002.png

Have fun tuning

Andy

[Steve Cole]

Here is a plot showing both cylinder going dangerously lean as the motor bangs off the rev limiter.  Note that this pull was at 80% throttle.

One of the cylinders went way lean at 4500 RPM in the sweep.

http://www.nbs-stl.com/HarleyTuning/TTS%20Tune%2002.png

Have fun tuning

Andy

The only thing that is dangerous is your lack of understanding how the Rev Limiter works! What would you expect the mixture to be when the fuel is cut-off......... rich? Since the engine power is reduced there is nothing at all dangerous about it.

Not sure if your only purpose is to try and scare people but if your going to try and teach people you should learn how it works and understand it yourself, first.

As for working the ETC that is already done in bikes equipped with them, it's called Torque Management but there are plenty of bikes that are not equipped with ETC in the Harley world, let alone the automotive world in general and you need to make it work in all cases.

[whittlebeast]

How is the cylinder that is still getting some fuel not still attempting to make full power?

[FLTRI]

How is the cylinder that is still getting some fuel not still attempting to make full power?

I think the key word is "some" fuel...which would not produce hardly any power.
There are multiple ways to limit revs. Harley has used more than one over the years carbed bikes as well as EFI bikes.
Bob

[Admiral Akbar]

Here is a plot showing both cylinder going dangerously lean as the motor bangs off the rev limiter.  Note that this pull was at 80% throttle.

One of the cylinders went way lean at 4500 RPM in the sweep.

http://www.nbs-stl.com/HarleyTuning/TTS%20Tune%2002.png

Have fun tuning

Andy

The only thing that is dangerous is your lack of understanding how the Rev Limiter works! What would you expect the mixture to be when the fuel is cut-off......... rich? Since the engine power is reduced there is nothing at all dangerous about it.

Not sure if your only purpose is to try and scare people but if your going to try and teach people you should learn how it works and understand it yourself, first.

As for working the ETC that is already done in bikes equipped with them, it's called Torque Management but there are plenty of bikes that are not equipped with ETC in the Harley world, let alone the automotive world in general and you need to make it work in all cases.

[Admiral Akbar]

I wonder why they don't simply use the DBW and prediction to take care of the issue?   That would soften things right up.

Well, that would take software that would see acceleration rate and predict when and how much the throttle needed to be cut in order to keep the engine from going past the limit.
Way more easy to cut fuel a bit before the limit.
Bob

Steve,,

Might want to correct Bob on this one.. He seems to think that one fuel and spark are removed, the motor can continue to accelerate..

[FLTRI]

I wonder why they don't simply use the DBW and prediction to take care of the issue?   That would soften things right up.

Well, that would take software that would see acceleration rate and predict when and how much the throttle needed to be cut in order to keep the engine from going past the limit.
Way more easy to cut fuel a bit before the limit.
Bob

Steve,,

Might want to correct Bob on this one.. He seems to think that one fuel and spark are removed, the motor can continue to accelerate..

I'm pretty sure most Harley's have some sort of lead-in ignition retard or fuel cut in advance of the actual limit to try to keep the rpm overrun controlled to a minimum. At least that's what it looks like on the Dyno.
Hopefully Steve will share what he knows about what actually happens.
Bob

[whittlebeast]

Assuming that the logs are showing what is really happening at the injectors, MAP sensor, TPS and reporting the true spark advance......  All you have to do is to be willing to look at the data.

Have you guys tried logging a TTS with a Powervision or PC5/wideband/LCD-200 setup.

Have you tried looking at MAPxRPM vs MAF vs Duty Cycle off several hundred data logs off lots of systems?  The more I look, the more I learn.

Do you verify that the timing table matches whats happening in the log and matches what happens at the crankshaft with a timing light?  I see these issues all over the map as I tune.  I see discrepancies of 10 degrees on some systems.

Andy

[glens]

I wonder why they don't simply use the DBW and prediction to take care of the issue?   That would soften things right up.

Well, that would take software that would see acceleration rate and predict when and how much the throttle needed to be cut in order to keep the engine from going past the limit.
Way more easy to cut fuel a bit before the limit.
Bob

Steve,,

Might want to correct Bob on this one.. He seems to think that one fuel and spark are removed, the motor can continue to accelerate..

It can if you're looking at a PowerVision log...

[Steve Cole]

Assuming that the logs are showing what is really happening at the injectors, MAP sensor, TPS and reporting the true spark advance......  All you have to do is to be willing to look at the data.

Have you guys tried logging a TTS with a Powervision or PC5/wideband/LCD-200 setup.

Have you tried looking at MAPxRPM vs MAF vs Duty Cycle off several hundred data logs off lots of systems?  The more I look, the more I learn.

Do you verify that the timing table matches whats happening in the log and matches what happens at the crankshaft with a timing light?  I see these issues all over the map as I tune.  I see discrepancies of 10 degrees on some systems.

Andy

Again, learn how a HD works and get back with us. There has never been a MAF on any HD engine to-date! Just what do you expect to see when data is output as a secondary operation for ANY ECM? It's job (ECM) is to properly run an engine, any data it sends out is only there to help diagnose a problem. What you are not seeing is most cases is the problem and you need to learn to become smart enough to realize that this is what's happening. This has nothing at all to do with looking at the data and trying to plot it! You have to be smart enough to know your are NOT seeing what is really going on.

On a J1850 bike the data is no where fast enough for any of you to see what is going on. Last time I looked HD and PV were getting data at a rate of 2 frames per second from the ECM. At Rev Limit let's assume were at 6000 RPM so the engine is firing at 50 frames per second per cylinder. So you can only get 2 frames of the total of 100 that are happening per second. Does anyone think there might be a problem with the data captures?

Moving on to a HD-LAN bike, HD was still getting data at 2 frames per second and a capture posted by Whittlebeast showed PV running about 4 complete frames per second, so nothing has changed much and your never going to be able to see what's really going on at those rates.

You can plot it until the cows come home, with any plotting software you like, and you will never know/see what's really happening.

[whittlebeast]

I was looking at the data in post 13.  It looked like the data in that log was rather snappy base on the time stamp.

The data that comes off my PC5/wideband data logger setup is 66 samples per sec.

The Motec stuff I have been working on lately is more like 20 - 100 samples per sec depending what we are looking for.

Regarding a MAF, you may want to play with one on a few motors. I have already given you the keys to the kingdom.  All you need to do is open the door and look inside.

[Steve Cole]

I was looking at the data in post 13.  It looked like the data in that log was rather snappy base on the time stamp.

The data that comes off my PC5/wideband data logger setup is 66 samples per sec.

The Motec stuff I have been working on lately is more like 20 - 100 samples per sec depending what we are looking for.

Regarding a MAF, you may want to play with one on a few motors. I have already given you the keys to the kingdom.  All you need to do is open the door and look inside.

Andy

How about you Stop, Listen and Learn the HD before you come here and tell people things are dangerous. Automotive stuff does nothing here other than confuse HD owners. Start by learning what the sensor in question can and cannot do. If your looking at a sensor that has a response time of ~250 mS can you tell us how fast it can be accurately sampled and read?

As for you comment on a MAF I have been working with them since 1986, what would you like to know about them?

The data posted by Jason is from Vtune so I know how fast it comes in, while it is much faster than the others (typically 4X) it is still not fast enough to see what is happening at higher engine speeds.

[FLTRI]

Steve,,

Might want to correct Bob on this one.. He seems to think that one fuel and spark are removed, the motor can continue to accelerate..

So you feel the momentum the flywheels build during fast acceleration will dissipate to 0 at the split second the fuel is cut?
Did you ever do the WOT/accelleration/broken belt or chain test?
Again: 4th gear WOT @ 3500rpm - simulate broken chain/belt or missed shift by yanking in the clutch.
Come back and look at your rpm data log to see if the limit was exceeded?
Last time I offered this test you refused to try it...why?
Bob

[whittlebeast]

As a side note, in the race motors, we instantly loose all load on the motor at full power. 

We use prediction for rev limiting under normal acceleration.  Under instantaneous unloading, we exceed the programed rev limit by about 1000 RPM.  This happens about once a second in race conditions.  Ironic that you mentioned flywheels as keeping them bolted to the crank is real issue.

Rev limiter logic is a big deal over in that world.  The logic is all on a crank tooth by tooth basis over there.  Those motors have accel rates of about 38000 rpm/sec.

Have fun tuning

Andy

[Admiral Akbar]

Steve,,

Might want to correct Bob on this one.. He seems to think that one fuel and spark are removed, the motor can continue to accelerate..

So you feel the momentum the flywheels build during fast acceleration will dissipate to 0 at the split second the fuel is cut?
Did you ever do the WOT/accelleration/broken belt or chain test?
Again: 4th gear WOT @ 3500rpm - simulate broken chain/belt or missed shift by yanking in the clutch.
Come back and look at your rpm data log to see if the limit was exceeded?
Last time I offered this test you refused to try it...why?
Bob

I did do it.. Not sure where the run file is.. Did it a number of times without recording.. Limiter set to 6500.. Right now it looks to be set to 6400.. If I get time may try again...

[Steve Cole]

As a side note, in the race motors, we instantly loose all load on the motor at full power. 

We use prediction for rev limiting under normal acceleration.  Under instantaneous unloading, we exceed the programed rev limit by about 1000 RPM.  This happens about once a second in race conditions.  Ironic that you mentioned flywheels as keeping them bolted to the crank is real issue.

Rev limiter logic is a big deal over in that world.  The logic is all on a crank tooth by tooth basis over there.  Those motors have accel rates of about 38000 rpm/sec.

Have fun tuning

Andy

Andy

You skipped over answering the questions in  Reply #42, are you going to answer them?

Most all Rev limiters are handled off a crank position sensor if a engine is equipped with one and that is what Delphi is already doing in the HD case.

[whittlebeast]

Regarding tuning Harleys, it is easiest to look at the long term fuel trims.  Dynojet elects to not hide them.

Regarding MAFs, I am good there.  We use them fairly often. They get really fun as a data logging device when dialing in hyper motors.  All sorts of cool thing show up in the logs.

Andy

[Steve Cole]

Regarding tuning Harleys, it is easiest to look at the long term fuel trims.  Dynojet elects to not hide them.

Regarding MAFs, I am good there.  We use them fairly often. They get really fun as a data logging device when dialing in hyper motors.  All sorts of cool thing show up in the logs.

Andy

They are two really basic questions and yet you seem to not know how to answer them.

Since you cannot seem to answer them, you have no idea of how things work with an ECM and if you really think all one needs to do is look at long term fuel trims your sadly mistaken. So far all you have done is feed people a bunch of BS and when it comes right down to the HD Delphi system operation you really don't have a clue.

[whittlebeast]

I stand by all of my observations.

Andy