Really nice work. Check your hp using Vbox Dyno. Here is my best quarter mile back when I first bought the car compared to one of my most recent. Both were on shell 93 octane and not done on a drag strip.

Looks like all the mods I have done added around 100whp on average. The exhaust was already on the car when I got it. Pretty cool tool.

 

Very cool feature. I'll go and test it out on my single vBox run for my 991 when I get back home.

Looks like the result (avg wheel HP) are spot on with a load Mustang dyno.

 

Here was my M5 with a Dinan Exhaust, then with Dinan Exhaust and Stage 1 tune and downpipes from Noelle. The last one is with an update to Dinan Stage 2.

That last one shows more horsepower at the wheels than the 991 but of course the car is so heavy, the ET is over a second slower, not to mention the 60ft times are worse because of the RWD.

 

I spent some time with Pencilgeek tonight and there are three variables that he is changing for 991 Turbo.


The frontal area is 22.281 square feet (vs default 20)
The coefficient of drag is 0.31 and 0.32 for the aerokit (vs default 0.25)
The tire weight is 29 pounds for the stock PZero tire (vs default 25 lbs)


He is updating the database and should be finished in a few hours/days, but for the time being why don't you resubmit using these figures as your numbers should increase by maybe 20-25.


He also said to use the default "uncorrected" value in the Horsepower Correction section of the Weather Conditions.

 

Here's my one and (so far) only ever vBox run with my 991 TTS. Only mod is and off the shelf GIAC tune. I had over 3/4 tank of gas ~ 90 pounds: 10+ gallons of pump 91 was mixed with a couple gallons of e85. GIAC tune was set to race mode.


The three aforementioned default values in my post above were modified in my submission. I also added the extra point in the coefficient of drag as I have the aerokit.


I don't remember the weather but conditions were good with negative density altitude (roughly -23 feet as calc'd by this program).


Results are over 600 average wheel HP. Which seems unbelievably high for a tune-only car but DA was very low that morning and the tune really liked the exact gasoline mixture I tried that day. And this is GIAC's latest OTS tune which has been perfected from over 3 years of development (GIAC had the ECU before the 991 TT was even for sale).


Here's the 60-130 thread I posted back in February:


https://www.6speedonline.com/forums/...0-5-slope.html


And here's my dyno graph:

 

One other observation: you will get a higher average HP number if you submit a vBox run from a roll rather than from a standing start. Reason being is that wheel spin causes effective HP to drop so if you look at the first couple of seconds on your graphs, you are losing average HP there. But your results from the changes in mods is perfect, since both were from a dig. See if you have files from a roll to compare also. Would be interesting to see.

 

Thanks guys, let me briefly explain what Adam and I talked about tonight.

The first time you use the vBox Dyno, it uses the edmunds.com vehicle database lookup. More than 50% of the time it will have the drag coefficient, but unfortunately less than 10% of the time, it will have the car frontal area. These are both very important to get accurate results. I intentionally give conservative results in the absence of valid results from edmunds.com.

Usually within 24-48 hours of somebody entering a new car, I will look up the actual frontal area, drag coefficient, and tire weight and replace the default values with the real ones. So I recommend you coming back 48 hours later and run your files through again because you will usually gain about 25 whp with the correct frontal area, drag, and tire weight.

wrs, depending on when you ran yours, you might want to re-run to see if you pick up a little more whp from the program.

Enjoy

/PG

 

OK I will give them another run through, I like the tool and the increases in hp are really what I was looking for i.e. mod vs. no mod. I did the ones for my M5 and could see how each component made a difference. I will also go back and submit some of my files with the FVD piggy back instead of the AP tune and see how those look too.

Anyway, just right off the bat the numbers look pretty good. My car is a 9/13 build so I expected it to be lesser powered compared to the newer models. Even though it's a 2014, it was a launch car. I think they have been getting stronger each year, that is certainly how it worked out with the M5.

I could probably use some of my files from COTA for data from the roll.

 

The first is a roll at COTA and the second is a quarter mile from SAR a couple days before that. Both were in February but what is interesting to me is that the quarter mile with 104 gas at the drag strip gives a lower hp than the 93 gas did about a month earlier on the county road.

 

Actually it looks like on your 100-200kph roll that the ecu was pulling timing between the 4-7 second mark as your HP is dropping rather significantly.

On your 1/4 mile run, the HP seems much more stabilized through the run which would be an indication that the ecu was happy and likely not pulling timing.

 

There are two places at COTA where I can do a 100-200kph run and those are on the back straight and the grandstand straight. The back straight has a change in elevation from down to up, basically a big dip and so the DA is changing on that stretch. That is where the 100-200 was taken. On the grandstand stretch it's all uphill but the elevation change is very gradual until you get to the big rise into turn 1 but by that time I am slowing down anyway. So I went back and got my best 60-130 that was going uphill from the grandstand stretch and it's more stable. There is still a drop in there and I think that is due to gearshifts. When the car shifts gears the RPMs drop and the HP goes down while the torque goes up. The higher horsepower is on the higher RPM end of the dyno curve. The gear shifts are at roughly 70, 105 and 135mph. The other thing too is that the darker curve is smoothed. However, I would defer to Pencil Geek to weigh in on this as it's an interesting speculation but your car also shows the big dips at gearshifts as well. I annotated the gearshifts. Maybe PencilGeek can tell us about the calcs. I think it's really cool that he went to the trouble to account for all the factors and come up with these graphs. Kudos to you Robert.

 

Am I reading that right, and your average WHP is higher than your peak WHP? Hmmmm.

 

Probably a bug that needs working out. That's not the case on the previous charts. Good observation though.

 

That's the peak average HP. It's like that on my chart as well. Agree it's confusing and probably should be fixed to show the actual average hp.

No way my car was making 630 avg wheel hp on that run or at any time. If you at the HP line it's in the high 500's to low 600's. Probably averages to around 600.

 

Let me explain "average" whp. It's not actually an average; it's a polynomial best fit equation using "least squares fit" algorithm. I'm using the same math formula for this curve as if you plot the data in Excel when you select "polynomial" fit. Excel will let you select up to 6th degree polynomial. But sometimes 6th degree isn't accurate enough and needs higher.

I calculate a poly-fit from 3rd, 4th, -- up to 8th degree polynomial. There's another math equation that calculates the "goodness" of the fit. I select the poly fit curve that has the best "goodness" of fit.

But because it's a polynomial equation that produces a best fit curve, it's possible that you can end up with higher "average" whp than peak whp. It's rare, but yes that can happen. Bottom line, it's not a bug but just the way poly-fit curves turn out sometimes.

The alternatives are to rename "avg whp" to something else. I toyed with this idea, but it's a little too geeky to call it "poly fit whp" -- and I don't think anybody would understand what that means anyways. You would never want to calculate a true average whp anyways because unless you have a flat whp curve, then your lower whp output will always dominate the higher whp output. The resulting average would be way too low.

When I developed the poly-fit, I did use Excel spreadsheets with all the data from the vBox Dyno. It was pretty cool to see the vBox Dyno poly-fit perfectly mirror the Excel poly-fit graph.