Ignorant question pertaining to load, TQ Based Decel while acclerating

[Quicksand Jesus]

Good day, everyone. I'm working on a 2019 S550 with the 3.8 Whipple, built motor, lockout cams, and more. I'm still in need of dialing in many things, but on the dyno, when I do a part throttle pull I am getting "TQ Based Decel" as the torque source. I believe it correlates with the major discrepancy between indicated vs. scheduled TQ and air vs. desired load. My question is, where have I missed the "limit" to allow the desired load to rise over 1? I've attached a screenshot, log, and current calibration.

As always, I appreciate this community very much, and any advice is always appreciated. Thank you!


ptproblems.png

[Pistol_91]

Did you rescale your torque inverse tables?

[Quicksand Jesus]

Thanks for the comment; yes, I did. I cranked them up pretty high. I'm sure I'm missing something simple. It appears since the load isn't moving high enough, it doesn't use the higher torque numbers in the inverse table. Don't hesitate to look at the file I've attached

[murfie]

MP14 for aircharge multiplier and maximum load under the speed density tab.
These limit the calculated load, which is where desired load comes from. Calculated load should be 100% at WOT, yours it currently limited to 35-40% of your maximum actual load from the MAF sensor. You may want to consider rescaling your MAF transfer as you are right at the peak of it, moe RPM or better weather air and you will run out of MAF curve.

[veeefour]

MP14 for aircharge multiplier and maximum load under the speed density tab.
These limit the calculated load, which is where desired load comes from. Calculated load should be 100% at WOT, yours it currently limited to 35-40% of your maximum actual load from the MAF sensor. You may want to consider rescaling your MAF transfer as you are right at the peak of it, moe RPM or better weather air and you will run out of MAF curve.

No, desired load comes straight from torque model. SD side can only cap it.

[murfie]

No, desired load comes straight from torque model. SD side can only cap it.

You must have miss read what I wrote, you said no, then agreed with what I said.

[veeefour]

You must have miss read what I wrote, you said no, then agreed with what I said.

You said: .
These limit the calculated load, which is where desired load comes from..

Well that is only partially correct, you can actually dont care about SD at all. You can completely ignore SD and still have Desired Load requesting a high number, not limiting anything.

[murfie]

You said: .
These limit the calculated load, which is where desired load comes from..

Well that is only partially correct, you can actually dont care about SD at all. You can completely ignore SD and still have Desired Load requesting a high number, not limiting anything.

I was just answering OPs question "where have I missed the "limit" to allow the desired load to rise over 1?"
Not telling him how to BS the numbers in the TTL and LTT to get around limits.

[veeefour]

All good m8, just me checking on you

That load limits are usually set to 1 even in factory F/I applications.
I found they really dont do much, definitely not what you think.

Id say this not a way to get around, id say this is practical and smart way.

[murfie]

You have to understand the difference between standard aircharge load and maximum trapped aircharge load. Airload and calculated load respectively.

MAP max delta above baro: defines how much of MAP is boost from the FI. in an NA application this is 0 at all RPMs. In FI its the max boost at the given RPM. This table is usually easy for people to understand. Some over simplfy it and cause idle issues.

MAP max vs airmass: Defines engine effeciency from its MAP and maximum trapped airmass. in an NA application this means all airmass comes from barometric pressure usually something like 29.92=.005lb. Airmass being ~3 times engine displacement and standard aircharge. In FI this is the table people struggle with defining as you have to define FIs effeciency effect on the engines effeciency both positive and negative. Airmasses less than the engines displacement will come from MAP higher than barometric, seems to be the part throttle issues others never can get rid of with out skewing the TB model or TTL/ LTT tables. The throttle body should always control the airflow and hence the trapped cylinder aircharge, no matter the position of the bypass valve. If a bypass valve shutting causes a boost spike, you can't tune that out and it would need to be physically fixed. The TTL/ LTT is an inverse relationship, and should always remain inverse.

[engineermike]

It looks like he brute-forced the map max delta above baro and map max vs airmass. I don't know if unreasonably high values here could cause these problems, but they can cause other problems as we know. The other SD model values seem reasonable.

The only thing that stands out to me as a possible cause is the IPC MAP and Torque tables. I don't know if these will limit desired load though, but worth a try to fix them.

Good to see you, murf.

[veeefour]

You have to understand the difference between standard aircharge load and maximum trapped aircharge load. Airload and calculated load respectively.

MAP max delta above baro: defines how much of MAP is boost from the FI. in an NA application this is 0 at all RPMs. In FI its the max boost at the given RPM. This table is usually easy for people to understand. Some over simplfy it and cause idle issues.

MAP max vs airmass: Defines engine effeciency from its MAP and maximum trapped airmass. in an NA application this means all airmass comes from barometric pressure usually something like 29.92=.005lb. Airmass being ~3 times engine displacement and standard aircharge. In FI this is the table people struggle with defining as you have to define FIs effeciency effect on the engines effeciency both positive and negative. Airmasses less than the engines displacement will come from MAP higher than barometric, seems to be the part throttle issues others never can get rid of with out skewing the TB model or TTL/ LTT tables. The throttle body should always control the airflow and hence the trapped cylinder aircharge, no matter the position of the bypass valve. If a bypass valve shutting causes a boost spike, you can't tune that out and it would need to be physically fixed. The TTL/ LTT is an inverse relationship, and should always remain inverse.

Well i know how the things works but we are talking about where do the Desired Load value comes from. Its has nothing to do with max load tables under SD - you can set them to 0 this is not going to affect Desired Load.

[Pistol_91]

Mike whenever I had map max delta above BP set unreasonably high I would get the wrench and limp mode at 6krpms every run. Too high is worse than too low I believe.

[engineermike]

Pistol, I’ve found that setting max map over bp too high will actually prevent the cam schedule from entering OP. I’ve had setting it too low limit torque demand. But I’ve had other osid’s not limit driver demand with max map set low, so I guess it depends on the logic or some hidden switches.

[Quicksand Jesus]

Thanks, everyone; I'll look when I return to the car. Just for the record, in that log, I was not at 100% throttle. I was at ~50%. It works fine when I go WOT. I'll adjust the number MP14 Maximum load, turn down the MAP Max Delta to 26PSI, and adjust the map max vs. airmass, as that's about what the current setup does. I appreciate the help and discussion.

[murfie]

Thanks, everyone; I'll look when I return to the car. Just for the record, in that log, I was not at 100% throttle. I was at ~50%. It works fine when I go WOT. I'll adjust the number MP14 Maximum load, turn down the MAP Max Delta to 26PSI, and adjust the map max vs. airmass, as that's about what the current setup does. I appreciate the help and discussion.

Your pedal was 35-50%, but your throttle body shot open around 45% and was WOT. Not ideal for drivability.

One MP and locked cams it should be easy to plot trapped airmass(lb) on an x axis against MAP(inHg) on the Y axis. I didn't see a MAP sensor in your logs, you are going to need to log the actual MAP with a sensor. Once you do that and filter by RPM regions, you'll see the MAP max vs airmass relationship easily. Its a bit harder when you have to see it across MP with the cams moving. I say inHg if you plan on regressing coefficients from this relationship.
Locked cams I would also look in to the bank to bank difference of the intake cams. Going from a poor memory, it was 10* different.

These airmass values that are less than engine displacement at the vaccum to boost transition are what you want to define in that MAP max vs airmass table, extended out to the max MAP and airmass you see. Of course with a MAP sensor and not the calculated MAP values, unless the calculated and sensor values agree.
Above the orange line is less than 100%VE, below it would be over 100% VE, kind of inversed to look at. the 100% VE area has shifted from baro MAP to 35-40 inHg MAP, Coyotes flow air very well and continue to do so even with forced airflow at partial throttle.

Vac to boost airmass.png

[Quicksand Jesus]

Your pedal was 35-50%, but your throttle body shot open around 45% and was WOT. Not ideal for drivability.

One MP and locked cams it should be easy to plot trapped airmass(lb) on an x axis against MAP(inHg) on the Y axis. I didn't see a MAP sensor in your logs, you are going to need to log the actual MAP with a sensor. Once you do that and filter by RPM regions, you'll see the MAP max vs airmass relationship easily. Its a bit harder when you have to see it across MP with the cams moving. I say inHg if you plan on regressing coefficients from this relationship.
Locked cams I would also look in to the bank to bank difference of the intake cams. Going from a poor memory, it was 10* different.

Thanks again! I think the reason it went to WOT is because the pedal WOT start was set to 50%; when I stay under that, it reports correctly and still does decel TQ. I'll take care of things before the car is delivered. These cars take a lot of time to do properly. You are correct. There isn't a MAP fitted, I can use my Mainline to hold a steady state and dial in the relationship.

The cam angles show off due to the fact that this engine was meticulously degreed. Many people are surprised by how far off some manufacturers' "centerlines" are once things are installed. Unfortunately, it's going to be a while before I get on this again, as one of the rotors on the Whipple moved out of its track and locked up the blower. The good news is that it happened at idle, and there is no engine damage. The bad news is this is the 4th Whipple I've had to send back for repair in the past 2 years.

[Pistol_91]

I was having trouble with the throttle opening up alot while slowly accelerating. Adjusted the SD models via the calculator and it fixed alot of my drivability issues.

[veeefour]

Max Load tables under SD have nothing to do with Desired Load, period with mic drop.

Stock 2020 Roush cal:
image.png

Stock 2019 Whipple stage 2:
image.png

Stock 2020 GT500:
image.png

All of those have no problem setting Desired Load high way above 2. The advise to raise those to get higher Desired Load is plain wrong.

[Pistol_91]

Mine are set to 1.0 currently and I get over 1.0 load desired and actual. So yeah you're right veefour