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I have the Durametric. It reports actual engine torque in % Maximum. What is that maximum torque in N-m or ft-lb? I have scoured Rennlist and the Internet and can't find any reference to this.
I have the Durametric. It reports actual engine torque in % Maximum. What is that maximum torque in N-m or ft-lb? I have scoured Rennlist and the Internet and can't find any reference to this.
I'm not sure (or trust) how Durametric calculates torque, but the 3.4 engine is 350nm/258ft lb torque, and the 3.6 engine is 370nm/273 ft lb torque..
I'm not sure (or trust) how Durametric calculates torque, but the 3.4 engine is 350nm/258ft lb torque, and the 3.6 engine is 370nm/273 ft lb torque..
Since it is labeled "actual engine torque" I am hoping that there is actually a torque sensor on the driveshaft. This could be acquired by measuring the angular twist of the shaft under load and knowing its diameter and the shear modulus of the steel.
Since it is labeled "actual engine torque" I am hoping that there is actually a torque sensor on the driveshaft. This could be acquired by measuring the angular twist of the shaft under load and knowing its diameter and the shear modulus of the steel.
Yea..... but there is no such sensor there or anywhere else, and the DME doesn't put out a torque value, so , the Durametric is taking MAF, RPM, throttle angle, ect. to do it's own calculations...
Since it is labeled "actual engine torque" I am hoping that there is actually a torque sensor on the driveshaft. This could be acquired by measuring the angular twist of the shaft under load and knowing its diameter and the shear modulus of the steel.
There is definitely not a sensor for torque. Even if there was a sensor to measure the physical torsion of the shaft, that torsion would be a function of the engine input torque vs the load on the shaft. Load is a variable as it would depend on drivetrain losses, the exact car weight (uphill/downhill), passengers, gas level, wind, air temp, etc. Most of those apps have you input the car type, and it uses either an approximation, or an actual value for weight of the car that you enter. Then it will calculate the engine 'force' based on the car mass and acceleration (F=ma) using the measured change in speed vs time. It converts to torque from linear force (using rpm), but that's just one more step. Sampling time will really matter here too, calculating a derivative (acceleration) from velocity vs time of 5-10Hz or so results in acceleration at 2-5Hz, and can be very noisy. So, the apps will apply some smoothing, which can have huge effects on the 'peak' value. Also HP/Torque calculations taken while driving should be with a grain of salt, because like I said, it will depend on the road slope, wind direction/speed (resistance), air temperature (density), road resistance, speedometer accuracy (tire size and wear), and other factors, all of which can have an enough of an effect to throw off the data. They sound minor, but 1% error (which each of those things can contribute) is already 3HP.
It can be interesting to use programs like VirtualDyno, etc. from OBD WOT drive data, but one must only compare the same car/setup to itself, don't expect the HP/Torque numbers to mean anything real, and record runs that are as exactly consistent as humanly possible. And still expect error comparing runs.
BTW. Thanks for resurrecting this thread! I had missed it, and I love good data. I like the proposed use of MAF data (plus IAT, rpm, altitude(air density)) because measuring and tracking how well the engine is breathing is a pretty fundamental measurement that removes alot of outside noise. My car is in pieces right now for a UAOS install and some other work, but when it's running, I look forward to collecting consistent MAF data. (and a new set of AOS vacuum / Blow-by pressure data: https://rennlist.com/forums/996-foru...w-by-test.html)
Hey Josh, every thing you just posted is spot on !! You have your head wrapped around the Physics and Dynamics of Automotive Performance very well as seen from this post and others,and have been a pleasure to work with on your UAOS !
Just curious as to what you are doing for a living, and hopefully it's in the Automotive Industry somewhere..Glad you enjoyed this old thread, it didn't get a lot of participation, but did provide a lot of "late night reading" for quite a few people..The Bluetooth OBDII Guages available in this thread are really sweet and nice to have to monitor your engine..
Thanks. A PhD in Physics helps; I'm not working in the automotive industry though, this is just the hobby.
Actually, I've done much more data and analysis on my daily driver than I've managed on my 996. For some strange reason when driving the 996, I tend to forget about logging data (Bluetooth OBDII to TorquePro) and I come back home having collected nothing but a stupid grin.
Thanks. A PhD in Physics helps; I'm not working in the automotive industry though, this is just the hobby.
Actually, I've done much more data and analysis on my daily driver than I've managed on my 996. For some strange reason when driving the 996, I tend to forget about logging data (Bluetooth OBDII to TorquePro) and I come back home having collected nothing but a stupid grin.
lol,, I know the feeling, my radio stopped working for a couple of months then just came back on by it's self, and I didn't even care !!
Had time to read the thread and collect the data. I didn't make entries for the conversion from mass air flow (i.e. chemical horsepower potential) to estimated mechanical HP (Porschetech3's 0.75 efficiency number), nor did I enter the Motorsports Standard Atmosphere conversion values. Maybe in the next version, but here's what's been provided so far, grouped by engine size:
And here's SI units, if you're into that sort of thing... (which I usually am):
I can post the text/xls if anyone is actually interested.
When it's possible to do so (aka when the snow melts) I'll do some pulls in my 996 Turbo. Obviously forced induction gives a volumetric efficiency of much greater than 100%. I actually have some Durametric logs already without the MAF signal though.
12-16-2020, 09:05 PM
