Any value in OBDII app HP/TQ calculations? Poor Man's Dyno or inaccurate gimmick?

[InFiD3ViL]

Ok, first off, I want to clearly state that I know this is absolutely NOT a substitute for a real dynamometer measurement. My goal here is to simply establish if there is any validity to wheel horsepower and torque measurements that are calculated via OBDII apps for tablet and phone, ie. 'Torque' and 'Dashcommand'.

I will now establish why I think they are fairly accurate as long as all proper settings are established, ie. displacement, vehicle weight, transmission and final drive gearing, etc.

When I was still running my L99 I ran multiple HP/Tq measurements via the Dashcommand app for my Android head unit. What got me to think these are at the very least somewhat accurate is comparing other dyno'd cars with my exact or similar mods (SEE MY MOD LIST BELOW) and take a look at the first picture below. The app produced results very close to where I should have been for a nearly full bolt on L99. Coincidence? Possibly. But it is interesting to say the least.

The second picture is with the same exact mods (Except stock LS3 cam and milled .015 heads) but after I installed my LS3. This LS3 was freshly rebuilt with stock LS3 cam and new rings, bearings, springs, etc . and I had the heads milled .015. There is definitely an improvement over the L99 results, both felt and shown. Do I really think I am getting 413 rwhp/tq on a bolt on LS3 behind a 6l80e? No. But it does show that there were gains over the L99 results, which is really what I was after.

I have actually run the L99 and LS3 tests multiple times and the L99 always gave similar results with a max of 374 rwhp, but I didn't save that picture. The LS3 results shown below are the highest I have reached so far, although I did have an anomaly on the 3rd picture as I had a bit of wheel spin and the TQ value shows completely unrealistic for my mods. Both Dashcommand and the 'Torque' app state that you cannot have any wheel spin for accurate results. All pulls were done in 4th gear at or near 6200 rpm.

Before I get laughed out of the forum I just want to state that I do NOT take these results as anything more than what they are. I know if I want real numbers I need a real dyno, simple as that. Even then, this is only a tool for comparison's sake. I wanted to validate the feeling I had that my LS3 feels more powerful than my L99 did. But I do find it kind of cool that I am getting results that are fairly close to where I 'should' be for the mods listed below, although the LS3 results are a bit high in my opinion. Also, part of the settings in these apps requires exact vehicle weight. I was only able to go by the listed weight for the car, which of course does not include my fat ass or the weight difference of any of the modifications made to the car over the years, so that will skew accuracy as well. I would consider these more as ballpark figures, maybe a little bit better than guessing. But for checking gains after a part swap I think it will come in handy for others.

Mods: LS3 Swapped A6 (Stock LS3 cam) - Heads milled .015, Melling HV 10296 Pump, TSP Long tube Headers (Catless), X-Pipe, FM Outlaw Axle Back, Stage 2 Ported Throttle Body, Vararam OTR CAI, Mike Norris Gen 2 Catch Can + GM 1LE Clean Side Separator, Hinson Wires/NGK TR6IX Plugs, 160* Stat, DynoSteve/RDP Tuned

1st picture: L99, same mods but without milled heads and running stock L99 cam
2nd picture: LS3 + 6L80e + mods above & in signature
3rd picture: LS3 + 6L80e + mods above & in signature + TQ results skewed due to excessive wheel spin

[Greenhornet2]

Horsepower and torque are all just a number. Same car different dunno different number. If you can get steady results that are consistent i believe whatever you are using can show you gains in a reasonable fashion. It's kinda like my diablosport trinity i was running tests for 1/4 mile times. It's probably pretty accurate and gives me a good idea, at the track things would change if course, it's also a different environment. What would be fun is running my tuner 1/4 test at the track and see how accurate it really is so i could use it at home and know how accurate, or inaccurate it is.

[Moto-Mojo]

My observation of what you’ve done seems to be you did your homework. As electronically engaged as these cars are, it seems reasonable that you could get fairly accurate data from the OBD port. One thing’s probably certain, not many people who make a living at performing mods and dyno testing them are going to line up in support!

[SSkat]

I would assume based off the L99 and LS3 dyno threads that its probably pretty accurate. I think people with the SS sedan can get around that second number with bolt ons through the 6l80 so i wouldnt be shocked.

[InFiD3ViL]

Originally Posted by SSkat

I would assume based off the L99 and LS3 dyno threads that its probably pretty accurate. I think people with the SS sedan can get around that second number with bolt ons through the 6l80 so i wouldnt be shocked.

I would be very happy if I am over 400 rear wheel now. I figure it has to be close. I think the milling should help put me over the 400rwhp mark and calculated it should have brought me up to 11:1 CR. But that is exactly why I created this thread. No matter how many times I get favorable, repeatable results from the app, I would be hesitant to make the claim that I am at those numbers without running it on a real dyno.

[SSkat]

Originally Posted by InFiD3ViL

I would be very happy if I am over 400 rear wheel now. I figure it has to be close. I think the milling should help put me over the 400rwhp mark and calculated it should have brought me up to 11:1 CR. But that is exactly why I created this thread. No matter how many times I get favorable, repeatable results from the app, I would be hesitant to make the claim that I am at those numbers without running it on a real dyno.

time to get a baseline dyno then cam it!

[InFiD3ViL]

Originally Posted by SSkat

time to get a baseline dyno then cam it!

Yeah I know man. I think about that daily. Think I will gather all the parts to do it right, like converter and gears, and then do it all at once.

Believe me, it hurt swapping in that new LS3 with the stock cam. But money wasn't so freely flowing at the time.

[Greenhornet2]

Seriously, don't get wrapped up in numbers. They really are just numbers. Numbers that matter are time slips. A 900whp car can lose to a 700whp car.
My car ran 574whp when dynotuned at jannetty. At a dyno day at slowhawk it ran 595whp with no changes made so, cool i say i have 595hp but the car is the same as it was before lol. Funny thing is slowhawk also uses a mustang dyno, so maybe on a dynojet i'm at 620whp. Does it matter? Nope it's still the same car. Nobody knows what the true output is! They are used as tools to measure gains.

[InFiD3ViL]

Originally Posted by Greenhornet2

Seriously, don't get wrapped up in numbers. They really are just numbers. Numbers that matter are time slips. A 900whp car can lose to a 700whp car.
My car ran 574whp when dynotuned at jannetty. At a dyno day at slowhawk it ran 595whp with no changes made so, cool i say i have 595hp but the car is the same as it was before lol. Funny thing is slowhawk also uses a mustang dyno, so maybe on a dynojet i'm at 620whp. Does it matter? Nope it's still the same car. Nobody knows what the true output is! They are used as tools to measure gains.

Yeah, I know it. Part of me wants validation that I may have broke 400rwhp with the new engine behind the 6l80, but in reality it's not that important. It does run great and feels strong. Once I go with a cam I will get it dyno tuned and give up on guessing.