Fuel Cut Torque Ratio Questions

[06300CSRT8]

Anyone ever play with these? Just want to verify how changing them would work. The description is:

[ECM] 44775 - Fuel Cut Torque Ratio vs. Requestor: A torque ratio above this is allowed to use fuel enleanment to reduce torque. Below this value, only fuel cut can be used.

The part that confuses me is "enleanment" which to me sounds like pulling fuel, but then says below the value ONLY fuel cut can be used. Arent enleanment and fuel cut the same thing??

And I assume the "Torque Ratio" calculation is ETC Commanded torque versus Actual Torque output?

[06300CSRT8]

Based on the Ford VCM Editor page, these are further defined as follows:

Fuel Cut Torque Ratio vs. Requestor: If the Torque Ratio Request is below this value then cylinder fuel cut will be used instead of spark or ETC torque reduction methods. Set to 0.0 to disable cylinder fuel cut.

Spark Torque Ratio Limit vs. Requestor: Torque Reduction via spark retard will not go below this Torque Ratio, set to 1.0 to disable spark retard torque reduction.

Based on the above, to achieve my goal of having a spark only (no fuel cut) rev limiter, I should set the Fuel Cut Torque Ratio for "Engine Speed Limit" to 0.00 (currently 1.0 in my tune) and set the Spark Only Torque Ratio for the same "Engine Speed Limit" to 0.0 (currently already 0.00)

Every other post in this thread contradicts itself, 3 posts say a 1.0 in the Fuel Cut Torque Ratio table will disable, other 3 posts say a 0.00 disabled it.

https://www.hptuners.com/forum/showt...ue-Ratio/page2

[Plimmer]

Hope we get a clear answer to this, I've also fiddled with 0 and 1's but that doesn't seem to give a reliable "on" or "disabled" type outcome

[murfie]

Torque ratio vs requestor and how its used by the monitoring algorithm logic that can intervene in engine torque production (e.g., shuts off fuel to cylinders) is described in the patents for CLIP torque. ADD torque is also good to read about for understanding its effect on pedal feel. Both CLIP and ADD are there to improve pedal feel, something that a fuel, spark, or throttle cut can have a big impact on. This is the main difference between fuel cut and enleanment is the magnitude of the effect the driver feels. Enleanment would be a small change in fuel like the fuel imbalance monitor tables to a large but gradual change like DFCO. Cutoff is a abrupt stop to fuel flow.

CLIP torque
https://www.google.com/patents/US6705286
ADD torque
https://www.google.com/patents/US6246951

[Plimmer]

Torque ratio vs requestor and how its used by the monitoring algorithm logic that can intervene in engine torque production (e.g., shuts off fuel to cylinders) is described in the patents for CLIP torque. ADD torque is also good to read about for understanding its effect on pedal feel. Both CLIP and ADD are there to improve pedal feel, something that a fuel, spark, or throttle cut can have a big impact on. This is the main difference between fuel cut and enleanment is the magnitude of the effect the driver feels. Enleanment would be a small change in fuel like the fuel imbalance monitor tables to a large but gradual change like DFCO. Cutoff is a abrupt stop to fuel flow.

CLIP torque
https://www.google.com/patents/US6705286
ADD torque
https://www.google.com/patents/US6246951

Thanks that is helpful. I disabled CLIP/ADD and that seemed to band aid a bunch of problems like unexplained torque intervention and spark cut. Happy to leave it disabled until I figure out what else need editing

[Steven@HPTuners]

A small crash course in Ford's torque ratio system.
The overall system is known as "SAI" torque control, for "Spark, A/F Ratio, Injectors", and that's the order it prefers to reduce torque in.

First, a note: The system has existed in some form since EEC-V went out the door. It used to be the only system for torque reduction on EEC-V because of cable throttle. Anything that has DBW has this system, but also has the ability to reduce torque via throttle as well. In these systems, there are two tracked torques: A Base torque, for long term torque, which controls the throttle position, and an Instantaneous Torque, which is used for fast torque control and feeds the torque ratio torque reduction system.

Torque ratio is simply a ratio of current or desired brake torque vs torque at indicated conditions (MBT, Stoich, standard environment, etc.)
So now, how it works is every torque source has a configuration setup that basically tells the SAI system what is allowed for that torque source:
- Is spark torque reduction allowed?
- Can I ignore combustion stability clips (i.e. if you retard spark too far the engine starts to lose combustion stability)?
All sources are assumed to allow fuel/injector cut.

So, lets say we get a reduction request, spark reduction IS allowed.
Our desired torque ratio is say 0.7.

First, the system checks if it is allowed to do a spark cut for that torque source, if it is, it checks to see if its allowed to cut via spark only using the Spark Only Torque Ratio vs. Requester table:
g2smv2U.png

If our desired torque ratio is GREATER than this table, torque will only be reduced by spark if possible. If its below, we're guaranteed to have fuel intervention. Like previously mentioned however, there are clips to how much spark authority you can have before combustion instability happens, so even having something set to 0.0 doesn't guarantee ONLY spark will be used. As well, things like catalyst overtemp disable spark reduction entirely.

If we are lower, the system will use some form of fuel control.
Exactly what that control is depends on the Fuel Cut Torque Ratio.
BEAl6dh.png

If your desired reduction via fuel methods is GREATER than this value, it attempts to use A/F enleanment to reduce torque, using the vehicles calibrated A/F Ratio to Torque multiplier. Typically the authority you have here is only a few percent so enleanment is rarely enough on its own. Any left over reduction will need to be satisfied by cutting 1 or more injectors. I recently updated the description of this table to clear up something the old description led people to believe: Fuel cut may not be avoidable even if you set this to 0, because enleanment and spark can only do so much.

Most factory calibrations you will notice have the fuel cut torque ratio set to 1.0, meaning any kind of of fuel torque reduction must happen with injector cutout only.

This should make it pretty obvious how somethings like DFSO work. DFSO calculates its own torque ratio that it ramps (using the ramp on rate variable) down. Above 0.75 torque ratio, its using spark only. Below that it starts cutting injectors until ultimately you're at 0 Torque Ratio and all injectors are cut. This is part of what makes DFSO a smooth operation, as the TR continually decreases, the engine pulls power first with just simple spark, and then 1 injector, 2 injectors, etc.

As well, I should note some things do have special bypasses around this logic. I.e. Engine Speed Limit. Spark only set at 0 would lead you to believe it isn't allowed to cut fuel (Spark only!), but it bypasses this requirement. Fuel cut for engine speed limiting for example is always a possibility, no values you put in will make it use just spark or enleanment, etc. If your RPM goes over the fuel cut limit, it happens regardless.

Hopefully that clears up how you can set these tables up to achieve what you want.

[06300CSRT8]

Thanks very much, very very helpful.

What seems strange to me though is that ETC isn't part of one the methods to control RPM? Maybe I am just too new to this, but I had great luck with just spark cut leading to throttle closing to limit RPMs, never needed fuel cut, especially in a boosted application, 7500rpms and 1.2 lambda to cut power seems really really dangerous? Fueling would stay in line, as the MAF decreases, fuel demand would decrease but all the while maintaining your commanded lambda, never leaning it out.

[Steven@HPTuners]

Thanks very much, very very helpful.

What seems strange to me though is that ETC isn't part of one the methods to control RPM? Maybe I am just too new to this, but I had great luck with just spark cut leading to throttle closing to limit RPMs, never needed fuel cut, especially in a boosted application, 7500rpms and 1.2 lambda to cut power seems really really dangerous? Fueling would stay in line, as the MAF decreases, fuel demand would decrease but all the while maintaining your commanded lambda, never leaning it out.

Oh it still is there to control it. Spark into ETC is the normal route for that, I was just specifically leaving out the ETC portion of the system as that works through an entirely different mechanism. The fuel cut feature isnt normally activated unless you raise your rev limit without raising the fuel cut one, except in cases of things like 3->2 downshifts when you meant 3->4.

[06300CSRT8]

Makes sense, I dont see a rev limit outside of the fuel cut limit. Only what is visible in the Fuel>Cutoff, DFCO>RPM Limits. There I see "Cutoff RPM" and "Neutral Cutoff"

I am dealing with an issue with the Whipple calibration specifically, they have an rpm limit set through the BCM i believe, which I cannot modify via HP Tuners. At 7500 (their limit) it cuts fuel on me. In HP Tuners, the Cutoff RPM and Neutral Cutoff are both set to 7800rpms, yet at 7500 i get fuel cutoff.

[06300CSRT8]

I am wondering if I give the Fuel>Open & Closed Loop>Base Fuel>Fuel Cyl Cutoff table a row for say 1.5 load and set that row to be the same as my WOT commanded lambda, this way even when cutoff is triggered the fueling stays the same?

[Steven@HPTuners]

Makes sense, I dont see a rev limit outside of the fuel cut limit. Only what is visible in the Fuel>Cutoff, DFCO>RPM Limits. There I see "Cutoff RPM" and "Neutral Cutoff"

I am dealing with an issue with the Whipple calibration specifically, they have an rpm limit set through the BCM i believe, which I cannot modify via HP Tuners. At 7500 (their limit) it cuts fuel on me. In HP Tuners, the Cutoff RPM and Neutral Cutoff are both set to 7800rpms, yet at 7500 i get fuel cutoff.

Whipple calibrations are done differently, with custom OS setups. We'll have to take a look and see if we can find how this is done.
As to rev-limit for fuel cut vs soft cut, the ones labelled Cutoff are fuel cuts (i.e. the Neutral and normal Cutoff),
the soft cut is typically vs temperature, so you should have an RPM Limit vs. Temp table (25415) for that.

I am wondering if I give the Fuel>Open & Closed Loop>Base Fuel>Fuel Cyl Cutoff table a row for say 1.5 load and set that row to be the same as my WOT commanded lambda, this way even when cutoff is triggered the fueling stays the same?

Not exactly, engine speed limiting in specific uses a cutoff mode that just straight up cuts all injectors, no way around it. The Fuel Cyl Cutoff is used during cutoff as the leanest a cylinder can be targeted during fuel enleanment. If you cut injectors, you need to target lean of stoich to prevent catalyst heating. However, you can only go so lean before misfire happens as well, so this logic is designed specifically to prevent that scenario.

[15PSI]

This is a helpful explanation of Fuel Cut Torque ratio. In the event, if anyone should want to have a document for reference of this discussion, I have assembled the posts into an MSWord doc for future use. If you find it helpful, keep it. If not, trash it.

Fuel Cut Torque Ratio Explanation Discussion.doc

[06300CSRT8]

Whipple calibrations are done differently, with custom OS setups. We'll have to take a look and see if we can find how this is done.
As to rev-limit for fuel cut vs soft cut, the ones labelled Cutoff are fuel cuts (i.e. the Neutral and normal Cutoff),
the soft cut is typically vs temperature, so you should have an RPM Limit vs. Temp table (25415) for that.

On this note, it is strange then that Whipple sets up the soft limits 200rpms higher than the fuel cut limits.

They have the following in stock form for a manual car:
Cutoff RPM: 7600
Neutral Cutoff RPM: 7000
First column of Engine Speed Limit vs (EOT, ECT, TOT): 7800

Yet with the above settings from Whipple, I get full fuel cut at around 7500.

[Steven@HPTuners]

On this note, it is strange then that Whipple sets up the soft limits 200rpms higher than the fuel cut limits.

They have the following in stock form for a manual car:
Cutoff RPM: 7600
Neutral Cutoff RPM: 7000
First column of Engine Speed Limit vs (EOT, ECT, TOT): 7800

Yet with the above settings from Whipple, I get full fuel cut at around 7500.

Doing this effectively disables the soft fuel cut and prefers the hard cut instead. Why they do that, you'd have to ask their calibrators unfortunately.

[06300CSRT8]

My question though is around how they are commanding ANOTHER rev limiter outside of all three of these tables.

Here were the scenarios where I hit their rev limiter...

Test1:
Cutoff RPM: 7600
Neutral Cutoff RPM: 7000
First column of Engine Speed Limit vs (EOT, ECT, TOT): 7800
Flare Tool RPM Limit: Normal (they say this will be 7500)

Result: Got fuel cutoff at 7500

Test2:
Cutoff RPM: 7800
Neutral Cutoff RPM: 7800
First column of Engine Speed Limit vs (EOT, ECT, TOT): 8000
Flare Tool RPM Limit: Normal (they say this will be 7500)

Result: Got fuel cutoff at 7500 (confirms they have a separate fuel cut rev limit in their OS, none of my changes mattered)

Test3:
Cutoff RPM: 7800
Neutral Cutoff RPM: 7800
First column of Engine Speed Limit vs (EOT, ECT, TOT): 8000
Flare Tool RPM Limit: Max (they say this will be 7800)

Result: Got fuel cutoff at 7500 (now makes me think the Flare tool isn't working now that I have tweaked the tune via HP Tuners)

Seems like nothing is actually functioning as expected.

[GrannySShifting]

My question though is around how they are commanding ANOTHER rev limiter outside of all three of these tables.

Here were the scenarios where I hit their rev limiter...

Test1:
Cutoff RPM: 7600
Neutral Cutoff RPM: 7000
First column of Engine Speed Limit vs (EOT, ECT, TOT): 7800
Flare Tool RPM Limit: Normal (they say this will be 7500)

Result: Got fuel cutoff at 7500

Test2:
Cutoff RPM: 7800
Neutral Cutoff RPM: 7800
First column of Engine Speed Limit vs (EOT, ECT, TOT): 8000
Flare Tool RPM Limit: Normal (they say this will be 7500)

Result: Got fuel cutoff at 7500 (confirms they have a separate fuel cut rev limit in their OS, none of my changes mattered)

Test3:
Cutoff RPM: 7800
Neutral Cutoff RPM: 7800
First column of Engine Speed Limit vs (EOT, ECT, TOT): 8000
Flare Tool RPM Limit: Max (they say this will be 7800)

Result: Got fuel cutoff at 7500 (now makes me think the Flare tool isn't working now that I have tweaked the tune via HP Tuners)

Seems like nothing is actually functioning as expected.

Welcome to Coyote tuning, where it seems no one really knows LOL. I just posted same thing, my cut is at 7300, the Limit vs temps at 7500, and i get cut at 6600 or 6900 depending on what gear Im in

[Carlyle_Eric]

GrannySShifting.... I am having the same issue. ALL limiters are set to 7500. Yet when tuning on the dyno in 7th gear, I get fuel cut at 6900rpm. This is a 2018 A10 car. So I am starting to dig through the trans tables to see if something pops up. We need to figure this out.

[DVR IMP]

Carlyle_Eric might look in trans>general and see if maybe there is an OSS max rpm that needs to be raised for your 7th gear ratio.

[CCS86]

A small crash course in Ford's torque ratio system.
The overall system is known as "SAI" torque control, for "Spark, A/F Ratio, Injectors", and that's the order it prefers to reduce torque in.

First, a note: The system has existed in some form since EEC-V went out the door. It used to be the only system for torque reduction on EEC-V because of cable throttle. Anything that has DBW has this system, but also has the ability to reduce torque via throttle as well. In these systems, there are two tracked torques: A Base torque, for long term torque, which controls the throttle position, and an Instantaneous Torque, which is used for fast torque control and feeds the torque ratio torque reduction system.

Torque ratio is simply a ratio of current or desired brake torque vs torque at indicated conditions (MBT, Stoich, standard environment, etc.)
So now, how it works is every torque source has a configuration setup that basically tells the SAI system what is allowed for that torque source:
- Is spark torque reduction allowed?
- Can I ignore combustion stability clips (i.e. if you retard spark too far the engine starts to lose combustion stability)?
All sources are assumed to allow fuel/injector cut.

So, lets say we get a reduction request, spark reduction IS allowed.
Our desired torque ratio is say 0.7.

First, the system checks if it is allowed to do a spark cut for that torque source, if it is, it checks to see if its allowed to cut via spark only using the Spark Only Torque Ratio vs. Requester table:
g2smv2U.png

If our desired torque ratio is GREATER than this table, torque will only be reduced by spark if possible. If its below, we're guaranteed to have fuel intervention. Like previously mentioned however, there are clips to how much spark authority you can have before combustion instability happens, so even having something set to 0.0 doesn't guarantee ONLY spark will be used. As well, things like catalyst overtemp disable spark reduction entirely.

If we are lower, the system will use some form of fuel control.
Exactly what that control is depends on the Fuel Cut Torque Ratio.
BEAl6dh.png

If your desired reduction via fuel methods is GREATER than this value, it attempts to use A/F enleanment to reduce torque, using the vehicles calibrated A/F Ratio to Torque multiplier. Typically the authority you have here is only a few percent so enleanment is rarely enough on its own. Any left over reduction will need to be satisfied by cutting 1 or more injectors. I recently updated the description of this table to clear up something the old description led people to believe: Fuel cut may not be avoidable even if you set this to 0, because enleanment and spark can only do so much.

Most factory calibrations you will notice have the fuel cut torque ratio set to 1.0, meaning any kind of of fuel torque reduction must happen with injector cutout only.

This should make it pretty obvious how somethings like DFSO work. DFSO calculates its own torque ratio that it ramps (using the ramp on rate variable) down. Above 0.75 torque ratio, its using spark only. Below that it starts cutting injectors until ultimately you're at 0 Torque Ratio and all injectors are cut. This is part of what makes DFSO a smooth operation, as the TR continually decreases, the engine pulls power first with just simple spark, and then 1 injector, 2 injectors, etc.

As well, I should note some things do have special bypasses around this logic. I.e. Engine Speed Limit. Spark only set at 0 would lead you to believe it isn't allowed to cut fuel (Spark only!), but it bypasses this requirement. Fuel cut for engine speed limiting for example is always a possibility, no values you put in will make it use just spark or enleanment, etc. If your RPM goes over the fuel cut limit, it happens regardless.

Hopefully that clears up how you can set these tables up to achieve what you want.

Hi Steven, thank you for the explanation!

Yet again, this seems to conflict with LaSota's explanation of the table (Fuel Cut Torque Ratio). He first tells you to change just the Driver Demand entry from 0.95 to 1, and you are done.

Then, 40 pages later, he comes back to the same table and says to zero out every single entry. Citing that "0=no torque reduction, and 1=100% torque reduction".

It sounds like you disagree entirely with this view. Would you recommend leaving this table alone, making slight modifications, or zeroing it out?

[CCS86]

Even the description in Editor doesn't seem to match your description:

[ECM] 44775 - Fuel Cut Torque Ratio vs. Requestor: A torque ratio above this is allowed to use fuel enleanment to reduce torque. Below this value, only fuel cut can be used. If the torque reduction ratio request is below this value then a cylinder fuel cut will be used instead of spark or ETC torque reduction methods. Set the value for the corresponding torque source to 0.0 to disable cylinder fuel cut torque reductions. A value of 1.0 means that up to 100% of torque can be reduced via fuel cut, a value of 0.5 means that up to 50% of torque can be reduced via fuel cut.