Just how accurate is the AP3 torque gauge?

[AMontgomery]

This is a two stage question:

First, just how accurate is the torque read out on the AccessPort? Is it a reliable judge of performance increases as it pulls from the same parameters each time, it should have consistent results, regardless of accuracy, it should show at least a relationship if all other conditions are similar.

Second, I've heard the stock ecu targets torque rather than boost, and I've seen a bit of a wall in some cases of around 250ft/lbs. I can only assume it retains that trait when reflashed. I've also read that it limits torque in the lower gears to aid traction. My own use of the AP3 on a mostly stock car shows lower numbers the lower the gear. Is this actually limited or just a function of how the AP3 judges torque?

This is my most recent pull. I got to these torque numbers going down the interstate in 6th gear. Previously, I would hit 230ft/lbs in spirited driving (lots of WOT).

Just trying to get a reason for my findings. The car is an absolute blast and I know the gauges are no replacement for an actual dyno, it would just satisfy some curiosity.

Thanks to everyone who reads and responds.

 

[_Hunter702]

Stage 1 ots map limits the torque to 250 ft/lbs.

 

[AMontgomery]

But does it limit it from hitting that number more so in the lower gears than in the higher ones?

 

[_Hunter702]

But does it limit it from hitting that number more so in the lower gears than in the higher ones?

The lower gears are shorter than the 5th and 6th so the numbers are gonna be different

 

[dyn085]

Nobody has done a dyno with a comparison, so there's no real way to know right now how close or far from accurate the reading is. While it seems like there have been fixes, there used to be wild spikes noted by members in the past. Best-case scenario is that it is giving you a close representation of what you might possibly see on an engine dyno.

I think there is a relationship, but just like using a dyno you will want to keep variables to a minimum when using it for a general comparison. Stay on a smooth and flat road for your pull and use one single gear for testing. You'll see differences based on the gear you're in, so do your pulls in third or fourth gear. Use it to quantify changes you think you may or may not feel with your butt-dyno.

Better yet, download Virtual Dyno (www.virtualdyno.net/) and use your data-logging feature to log actual charts to compare. It's not a real dyno either, but it is a bit more realistic and eventually someone will have actual dyno results to compare/contrast the results that we see. It's easy and free, and one you get through the learning curve it becomes a reliable tool to compare gains/losses through mods.

Finally, you'll want to try to limit going full-boost in sixth gear as it puts a huge strain on your engine/drivetrain.

 

[AMontgomery]

Thanks, that's exactly what I wanted to know. I was expecting as much, though it would be nice to see someone do a comparison at some point in the future.

I didn't realize that about the OD gears and harder pulls possibly damaging the drive train. Makes sense with the exponentially increased aerodynamic drag at higher speeds.

 

[dyn085]

It's less about aerodynamic drag than it is about the cylinder pressures. In lower gears that pressure is able to be transmitted to the drivetrain easier. The best way to visualize it is using all of your power to try and accelerate in a lower gear on a bicycle than the highest-you're using the same (roughly) amount of power, but the higher gearing makes it harder to transmit to the road. That additional stress loads up in the drivetrain and weakens everything in the process.

 

[AMontgomery]

That makes sense. Basically the engine and drivetrain are under more load and thus under more stress when power is applied.

That probably has something to do with the higher torque ratings in higher gears as well.

 

[dyn085]

That makes sense. Basically the engine and drivetrain are under more load and thus under more stress when power is applied.

That probably has something to do with the higher torque ratings in higher gears as well.

That is possible, though the estimated torque feature is simply based on whatever algorithm the engineers came up with. I will say that throughout my entire modification process I have watched the number grow and occasionally stay the same (dependent on mods, of course). It generally gives me a little extra in the morning when it's cooler and a little less when it's warm out, so I feel it's close enough for me when I'm not concerned with 'exact' figures.

Once I find a reputable shop with a dyno nearby, I intend on data-logging the pulls for comparison. I intend on including the estimated torque for comparison along with mph and most of the default pid's. This should be able to give me an accurate comparison of the dyno, estimated torque, and v-dyno.

 

[AMontgomery]

My thoughts exactly. When I have the time to take it in to a pro shop for a tune I'm going to jump on it. But I think I'll wait until I can have a few more mods, an FMIC and Downpipe at a minimum. Then I can have it tuned to match mods that I'll be sticking with for a while. But the AP3 and V-Dyno should be a good visual on progress in the meanwhile.

I kinda wonder if the AP3 is reading torque given the same parameters that the stock ecu uses. Meaning it's reading the same as the engine does when it decides to cut torque for more traction.

 

[COBB Tuning1]

The torque monitor is an estimation based on the calibrated torque to load and load to torque tables in the ECU. There are several compensations and modifiers that are integrated into the model, so it will only be as accurate as the model itself. Since there are so many other functions that rely on the accuracy of this model it can be challenging to maintain the accuracy without doing extensive calibration with the right tools. We've found that the stock model values work well on the stock turbo but will not be accurate on upgraded components. At that point it's better to ignore this value and tune the speed density system to ensure accurate fueling and load calculation.

Cheers,
Braden @COBB

 

[AMontgomery]

That makes a lot of sense. Especially with regards to higher torque numbers at higher loads present with higher speed pulls.

Thanks!