cognyak

great info!

bhmax

iTrader: (2)

Do I have to do anything special to get boost to show up in the graph? I'm logging it but it's not showing up in VD.

Raptord

iTrader: (10)

You can add the column name manually in the settings.

mrboost05

iTrader: (25)

just wondering why when i use the gear change function it changes my hp/tq dramatically ? when i do a log in 3rd the reading seems spot on but if i change it to 4th gear it will display like 900whp lol here is a log i just did let me kno if i am on the right track.

Raptord

iTrader: (10)

If the log is in 3rd gear then it'll only display the correct numbers when you select 3rd gear in VD.

Look at it this way: The program calculates your horsepower based on how long it takes you to go from X rpm to Y rpm. If you go from X to Y in third gear it takes a Z amount of time. If you tell it you did that pull in 4th gear, it sees that you went from X to Y in Z time but on a much longer gear (4th instead of 3rd). To be able to go form X to Y in Z time in 4th gear takes a lot more power than going from X to Y in Z time in third gear.

Hope that's clear. It makes perfect sense in my head but sometimes that's harder to translate into written words.

mrboost05

iTrader: (25)

made perfect sense i am picking up what your dropping lol thanks

Boosted Tuning

iTrader: (12)

Updated post #2

tscompusa

iTrader: (31)

agreed 100% on the multiple runs overlay. even sometimes overlaid with the same power it can be off if going through the same road, but this at least shows there were no spikes or anomalies in the pulls.

it is best to do your pull uphill as opposed to downhill, or you may not perform as you should based on your power levels. remember guys, a lower HP car that performs exceptionally well looks better then a inflated hp/tq car that doesn't perform as well as it should.

MrSquirr3l

iTrader: (13)

love this thread. helped me get my numbers to be pretty dang close to what i put down on a real dyno. though took me awhile to searh up my gear ratios.

swampy

I've just started using Virtual Dyno and have a question.

How are tire diameter, final drive ratio and gear ratio used in the calculations?

Theoretically the power required to accelerate an object depends on the mass and acceleration of the object. The acceleration can be determined from a time series of speeds. That is a log containing time and speed. From this, knowing mass, the power can be calculated.

Additionally if you know the rpms you can convert power to torque.

So all we need is the mass and a log of time, speed, rpm.

Not sure where tire diameter, final drive ratio and gear ratio come into it.

However it must because when I changed my automatic's 3rd gear ratio from the theoretic of 1.33 to a more realistic 1.55 allowing for torque converter slip during acceleration, then the power result dropped.

Which leads to an additional question for an automatic, should one allow for TC slip in the gear ratios or not?

Many thanks.

ReaperX

iTrader: (5)

The answer is in your question, variations in tire diameter and gears will produce inaccurate results. Speed sensor calculates the speed of the vehicle based on how many revolutions your hub makes in a specified time. A tire that is taller or smaller than the factory size will affect how many revolutions the hub makes and will effect what the ecu reads as the speed. The same goes for final drive and gear ratio. Your actual speed will differ from the ecu's calculated speed and will through off your VD results. Entering those perameters into VD will correct for those variations.

swampy

Thanks for the reply.

That leads to a few more questions.

So if VD is calculating speed from gear ratio, diff ratio and tire diameter, then why is speed needed in the file? Does it use both, or just ignore the one in the file.

Should one enter the tire diameter calculated from the tire dimensions, or from the manufacturers revs/mile? The latter is about 3% lower, but maybe VD is allowing for that internally?

I'm using 3rd gear in my auto and the ratio is 3.3. But because of torque converter slip the actual ratio varies between 3.5 and 3.6 during the pull. So what number should I use? VD knows I have an auto say maybe it is making an allowance for TC slip.


Note that I have calibrated my VSS signal using GPS and road mile posts. I manipulate the log in Excel to apply any needed corrections before submitting it to the app.

Thanks again for the help.

swampy

Just another question while we are at it.

What is the difference between a "Car", as in Car Editor, and a Profile?

It seems like Car is being used when you set the conditions for a run. Where is Profile used?



And another note, when I try to edit the first Profile I entered I get an Unhandled Exception error. The Details are too large to post here but I could send them to anyone interested. Using V1.2.3.



And if anyone can tell me how to actually control zooming that would be very helpful.

Thanks again.

swampy

Here's my latest results.

Using weight of 2797 lb accurately measured on the scales at the dump,
and the theoretical tire diameter of 24.2",
and the 3rd gear ratio of 3.33 (which doesn't allow for TC slip),
and applying the SAE correction, but fudging the temperature a bit to allow for the high humidity of the day which VD doesn't seem to be concerned about,
and using IAT, not ambient, for the temperature,
and using "Mustang", the most pessimistic of the 3 dyno settings,

we get 121 WHP @ 6,320 rpm (with similar results fom 4 other logs that I've submitted to VD)


This seems realistic to me. Brian G. reports low 130s for stock MTs of 2007 vintage. Take of about 10 HP for the auto, and you have low 120s.

So now what if I mess with the gear ratio??


I changed the gear ratio to 1.5, which is about what it actually is with TC slip. I have arrived at this by calculating back from true vehicle speed using rpm, diff ratio, and Michelin's revs/mile (858) for the tire.

Anyways the result was 93 WHP.

By changing the dyno setting to DynoJet, the most optimistic, it raised to 107 WHP.


So I'm just hoping that the app is making an internal correction for the fact that I have an auto, and so I was in effect double applying it.




Any comments, suggestions?

Raptord

iTrader: (10)

You don't need to log speed for VD