fossumja

iTrader: (4)

For anyone using the MaxQ, what kind of numbers do you see from the HP calculation? Looking through numerous runs and a few accel tests, it seems like I never see much higher than about 135HP during acceleration runs. I recognize that the delivered power "at the Cg" will be lower than either the advertised HP or a chasis dyno due to aero drag, inertial losses etc. but these losses seem a bit excessive. Am I just down on power or is this typical?

All runs using 3050lbs, ~level, ~65F ambient, 2nd and 3rd gear runs. I've double checked the calculation, and it seems accurate.

chiketkd

iTrader: (5)

Jim,

My co-driver monitored our runs this year with his MaxQ syetm. Not sure if he's able to retroactively go back and use the horsepower function on previously gathered data. I imagine a pro solo course like Toledo (perfect flat surface) would be a good venue to get a hp reading. We were flat out in all of 1st and most of 2nd before braking for the first sweeper.

ULLLOSE

iTrader: (1)

I just went back and checked a few files, the most I saw in 131.2hp.

tpdrx8

Wow, I was really hoping Jim was doing something wrong . . .

ULLLOSE

iTrader: (1)

It is just GPS data, nothing like a dyno.

fossumja

iTrader: (4)

If you didn't run the HP signal in real time, you can back calculate it approximately from

hp=long G * MPH / .125

spike.spiegel

I'm running Chart 2.8c on my PDA, but don't see how to get the horsepower. Any hints?

mp5

There's a variable called "GPS Road Power" that you can select in Chart, but only if you chose to log that sensor when you recorded in Flight. You can configure your vehicle mass in the Setup program for the calculation to be correct.

The road power sensor is not part of the standard set of sensors to log, which I noticed I when I tried to check myself.

If you don't have it you can try to derive the HP from the acceleration numbers yourself.

ULLLOSE

iTrader: (1)

I don't recall ever setting that sensor to record. I just opened a couple of old runs and pulled that feature up on the menu.

spike.spiegel

Thanks mp5. I'm guessing they don't enable that sensor by default because it requires you to provide your vehicle mass, maybe? I set mine to 3050 and will see what I get at the next event.

This is an interesting topic to me; how accurate/useful is this information? It would be nice to know if my car is down or up on power relative to other B-Stock cars. The MaxQ is easier than going to a dyno, and would eliminate any dyno-specific discrepancies. I suppose weather conditions still might skew things a bit. Would it be better to use accel G's instead in order to get rid of the vehicle mass variable?

fossumja

iTrader: (4)

The number should be accurate, in the sense that it takes a certain amount of power to accelerate a given mass at a given rate and speed. As long as you have the right weight input, you will get a true measurement (although with 5Hz sampling, you need to use smoothing to get a good curve). However, the numbers will not give the true engine output or compare well with a chasis dyno. Just like rear wheel power will be lower than crakshaft power, the delivered acceleration power will be lower than power at the wheels because it includes rotational inertia, tire and air drag, and the effects of any incline.

What surprised me with the 8, is how much much lower this number is compared to the chasis dyno numbers I have heard quoted. It seems like about a 25% difference which I attribute largely to the inertia of the engine and drivetrain (and wheels/tires), at least in 1st/2nd gear. Out of curiosity, for those that have tested their cars on a chasis dyno, is the pull equivalent to a 2nd gear run (say 4-5 second long) or a high gear run (~10 sec long)? This will make a big differeence in how much of the torque/power is required to accelerate the engine and drivetrain.

ULLLOSE

iTrader: (1)

That was it... It did not have to be set to record on that run, but it did have to be enabled.

ULLLOSE

iTrader: (1)

Talking to guys in know that test cars for a living, 5Hz is to slow for any useful data. I am sure the numbers are way off because the autox run is in 2nd, and the dyno runs are typically done in a 1-1 gear (5th). I am about 50hp low on the GPS vs Dynojet.

spike.spiegel

Yeah, I assumed it was hopeless to try and get any meaningful HP numbers from this...I'm really only interested in the possibility of a metric that could be used to give an indication that my BS car is significantly down or up on power compared to other BS cars.

chiketkd

iTrader: (5)

Shawn never had this feature turned on before on his MaxQ, but it's now on and we will report back with the numbers we obtain from our last autocross of the season this coming weekend.

chiketkd

iTrader: (5)

Shawn and I had our final autocross of the season today -- his MaxQ showed a sustained 140hp on one of my runs for just over 1 second (peak of 145hp). FWIW, I installed new NGK's right before Nats and it was ~50F today. We were also running our still fresh Nats V710's on a decently grippy asphalt surface (VMP in Petersburg, VA -- site used for pro solos in the early 2000's).

KevinDietz

Just thought I'd make a quick post here.

When using the Hp feature on the MaxQData its important to have long hard pulls to get good hp numbers. Just like when you make a Dyno pull. Most AutoX courses don't have a section in them that would really give you good hp numbers. The best is to find a level section of road and accelerate from a rolling start all the way thru third gear without lifting. This will give you much better and consistent HP numbers.

Look for the new MaxQData video suite coming soon. Product Launch at the PRI Show in Orlando next Month. Video is fully integrated with Chart to display Data and Video together for analysis. Overlays video with data as it records. Scrolling thru chart data also scrolls video Data forward and back even in Slow motion. Compare two Autox Runs side by side with data and video.

Fyi

kevin

nmarz77

Where did you get the weight from? Did you actually measure the car with yourself in it? Because the curb weight of the car is around 3,050 lbs. That's the car with full fluids minus passangers and cargo. So did you not add your body weight in maybe? If so that would give you a lower reading.

mp5

He probably got it from real life, rather than from magazines and stuff. A base model in B-stock trim with typical autox fuel levels can get to low 2800s. See the numbers from the 2007 Nationals: https://www.rx8club.com/attachment.p...0&d=1198093499

3050 seems high for curb weight even for the fat GT model.

chiketkd

iTrader: (5)

I've weighed my car multiple times throughout this season - so I have a good idea of what it weighs in race trim and just added the my body weight to that.

nmarz77

Really.....hmmmm.

spike.spiegel

Just did a run out on the street. I saw 138-142 over the course of a second (56-62mph). Set vehicle mass to 3050 lbs, ~65f ambient, stock wheels/exhaust, about 50 pounds of equipment in the trunk.