"Max Torque: RPM vs Gear" set to 1280 ft lbs???

[cptinjak]

Car: 2000 C5 with longtubes and a modified intake.

I was hoping someone could clear this up for me. In the "Max Torque: RPM vs Gear" table in my tune, the entire field is set to 1280 lbs. This is untouched since the car was stock. If you attempt to input any number in the field higher than 640, it will default back to 640 ft lbs.

Why is this field set so high when HPTuners states that its range is 0 to 640?



Also, I was wondering what the "Max Torque" field controls, and how the VCM is providing this information. Is it referencing predetermined torque numbers somewhere based on RPM increase vs time vs gear? And how does it control tq if the max value is determined to be met? ETC? Fuel? My car is making right around 350wtq with just bolt ons. Theoretically, if this number is calculated "at the flywheel" my car should be exceeding the 350 ft lbs maximum value, so I do not understand what the number is doing.

Could this value be holding me back? Would setting this to the 640 maximum be of value to me?

I have been searching here and ls1tech and have not come up with answers to these questions. Any insight would be greatly appreciated.



Thank you,

Jack

[cptinjak]

Bump. Can anyone shed some light on this for me?

Thank you,

Jack

[Pekka_Perkeles]

How do you know that the car has a stock calibration in it's PCM?

Is the owner of the car an original owner? If not, then you can't be really sure what's in a PCM.

Just check the CAGS disable TPS. How come it's 0%? Definitely not a factory value. CAGS enable speed: 200 mph. Really :-)

It probably has some handheld tune, which may explain some strange numbers. I've once seen a RPM limit of 11.700 rpm on an "unmodified" PCM...apparently it wasn't unmodified. Luckily the value didn't have any particular meaning in that PCM, but definitely not a factory value.

[Pekka_Perkeles]

Could this value be holding me back? Would setting this to the 640 maximum be of value to me?

Use the 640 as a value.

[cptinjak]

How do you know that the car has a stock calibration in it's PCM?

Is the owner of the car an original owner? If not, then you can't be really sure what's in a PCM.

Just check the CAGS disable TPS. How come it's 0%? Definitely not a factory value. CAGS enable speed: 200 mph. Really :-)

It probably has some handheld tune, which may explain some strange numbers. I've once seen a RPM limit of 11.700 rpm on an "unmodified" PCM...apparently it wasn't unmodified. Luckily the value didn't have any particular meaning in that PCM, but definitely not a factory value.

I have compared to stock files from the repository. These values are stock. I did the cags delete and ve/maf tuning myself, but have not touched the TM settings.

Jack

[cptinjak]

Use the 640 as a value.

I have seen this recommendation before, just hoping for some insight as to what it actually does and how it does it.

Jack

[Pekka_Perkeles]

I have seen this recommendation before, just hoping for some insight as to what it actually does and how it does it.

Jack

I've never bothered to find out the details, but HP Tuners help file may give you some insights (I just checked it).

To my understanding, based on either measured (such as MAF) or modeled (such as VE) airflow values, the PCM tries to calculate whatever is the torque output in certain situation. I think that the "torque output model" takes also account things like ignition advance as an input for the calculation.

You can actually log the calculated torque in the Scanner. It is called as "delivered engine torque" and can be found under Engine/Torque Management.

Now, the 350 lbs/ft is probably same as the max torque of LS1. I don't know, since in my home country we use different..how to put it in english...different way to express the torque (Nm).

If your engine is pushing more than 350 lbs/ft, it makes sense to change the max value. I think this would allow the "torque output model" to be not flat after the current 350 lbs/ft limit has been reached.

Makes sense, right?

[cptinjak]

That makes sense. I assume the stock values may not be too accurate, because my car makes ~350rwhp
At the moment, so flywheel hp is way above 350.

Jack

[Pekka_Perkeles]

That makes sense. I assume the stock values may not be too accurate, because my car makes ~350rwhp
At the moment, so flywheel hp is way above 350.

Note that the value in that field itself cannot change how much air flows into your engine.

However, when traction control or torque management is activated, then at least ignition retard is used to lower the engine output. Maybe the ETC as well. And this will lead to a lesser torq and hp. This is why the 640 value in tuned cars is always recommended..

It is a fact that your car can make more torq than stock. If tc disabled, it does not matter what's the number in max torq field, the engine will push as much as it can.

[cptinjak]

So the TC and the TM are interconnected? I did not think they had anything to do with each other.

Jack

[Pekka_Perkeles]

So the TC and the TM are interconnected? I did not think they had anything to do with each other.

Jack

Agree, most probably they are not connected. But I think they both will utilize the torque output model. How exactly, I don't know.

[cptinjak]

Agree, most probably they are not connected. But I think they both will utilize the torque output model. How exactly, I don't know.

The TC uses only wheelspeed sensors I believe. If not, then I am drastically misinformed.

Jack

[Pekka_Perkeles]

The TC uses only wheelspeed sensors I believe. If not, then I am drastically misinformed.

Jack

Well, I hope you don't take anything I say as a truth! :-)

As I said earlier, I've never spend too much with these values, I just max what I think is necessary.

Anyway, I hope you can now increase the max. torq table without hesitation.

[Pekka_Perkeles]

The TC uses only wheelspeed sensors I believe. If not, then I am drastically misinformed.

Jack

Ah, one more thing. It may be so, that the ABS box is primarily responsible of traction control and it is requesting PCM to do something when there's wheelspin. Depending on rpm's, there might be a need for small reduction or big reduction of ignition retard. And here the calculated torque model may have some value, i.e. the PCM would respond differently in different situations. But this is just a speculation.

[cptinjak]

Well the table is already set to 1280 across the board, which is twice as high as the highest value I can enter! Lol

Jack

[Pekka_Perkeles]

Well the table is already set to 1280 across the board, which is twice as high as the highest value I can enter! Lol

Jack

Well there you go. I must have a good memory but rather short...

But wait a minute...1280 is not in the "Max torque/max torque" -table but in the "max torque/RPM's vs. gear".

I don't know which one has more...umh..."weight" in this case. I mean, what's in the other table, or around. There's discreparency now, right?

[Bill@HPTuners]

When we created the master definition the os we used likely had it set to a max of 640 hence the 640 value. Any value of 640 is pretty much the max for that table anyway.

[cptinjak]

When we created the master definition the os we used likely had it set to a max of 640 hence the 640 value. Any value of 640 is pretty much the max for that table anyway.

Thanks for the knowledge Bill! So what is the effect of the entire table being set to 1280 in the stock tune? Does it just default down to 640?

Also, can you enlighten me as to what the Max Torque value does when exceeded? Does it affect Throttle Position, fuel, spark, or a combination of these? I do rememer one WOT throttle log where I saw 99% TPS at approximately 5900rpm. I will attach it. I thought it was just an anomaly or a result of poor resolution, but could this be TM interfering? Log attached.



Thanks,

Jack