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 Post subject: Inflated numbers from VirtualDyno?
PostPosted: Tue Nov 12, 2019 6:02 am 
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RomRaider Donator

Joined: Mon Jun 08, 2015 4:52 am
Posts: 144
Hi all,

i've been using VirtualDyno for quite some time now, but i always had the feeling it's reading far too high.
Right now i have detuned for the winter, set for 0.7 to 0.8 bar boost and (imho) conservative timing and afr (11:1). Yet, VirtualDyno shows ~340 whp and ~420Nm on a 4th gear pull.

Attachment:
File comment: VirtualDyno plot
v57_4g.png
v57_4g.png [ 207.23 KiB | Viewed 3003 times ]


I'd love to believe this, but it seems unrealistic to me.

Car is a "stage 2.52" 08 WRX with built engine and downpipe, all else stock.
For logging i use BtSsm.
The car is in the VirtualDyno database and i have not modified anything in the profile, just entered SAE correction and weight values shown. Tires are stock size (205/50/17).

Could there be something i'm missing?


Attachments:
File comment: Log
BtSsm_20191110_155121.csv [13.75 KiB]
Downloaded 212 times
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 Post subject: Re: Inflated numbers from VirtualDyno?
PostPosted: Tue Nov 12, 2019 8:53 am 
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RomRaider Donator

Joined: Fri Sep 02, 2016 4:42 am
Posts: 504
Location: Riga, Latvia
Is it on stock gearbox?
Is the road going downhill?


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 Post subject: Re: Inflated numbers from VirtualDyno?
PostPosted: Tue Nov 12, 2019 9:03 am 
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RomRaider Donator

Joined: Mon Jun 08, 2015 4:52 am
Posts: 144
Stock gearbox, and the road is pretty straight.
I did get this kind of reading over a multitude of runs on many different (straight) pieces of road on many different days. This one is just the most recent example. (Other logs also dont show that hump, so ignore that please)


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 Post subject: Re: Inflated numbers from VirtualDyno?
PostPosted: Tue Nov 12, 2019 9:17 am 
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RomRaider Donator

Joined: Fri Sep 02, 2016 4:42 am
Posts: 504
Location: Riga, Latvia
I plugged the `08 wrx gearbox data and kmh from the log in a gear calculator and it seems off.

On stock gearbox with 3.9 final drive the speed at 6k rpm 4th gear should be around 190kmh, you have 163kmh instead.

If I leave the stock gear ratio for 4th gear, but change the final drive to 4.444, then the calculator spits out 166kmh which seems in line with your log.

If I plug that final drive in virtual dyno, I get ~237whp (ignoring the bump) which seems about right for your car and logged maf.

Attachment:
gear.PNG
gear.PNG [ 123.08 KiB | Viewed 2981 times ]


Attachment:
dyno.png
dyno.png [ 39.9 KiB | Viewed 2981 times ]


EDIT: Might be you have forester xt tranny + diff in there. You could check that by logging 3rd gear pull with rpm and kmh and then checking against calculator. Foz xt has different 3rd gear ratio than wrx.
Here's tranny data source: https://www.xcceleration.com/gear_ratios.html
Here's calculator: https://legacypic.uk/transmission/graph.php
Or.. maybe you can reach and read the tranny sticker part number - it might save you the hassle.


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 Post subject: Re: Inflated numbers from VirtualDyno?
PostPosted: Tue Nov 12, 2019 10:38 am 
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RomRaider Donator

Joined: Mon Jun 08, 2015 4:52 am
Posts: 144
Interesting find.
You're right, results look a lot more reasonable assuming a 4.444 final drive.
To my knowledge the gearbox is stock though, so i wonder where this might come from. Maybe EDM WRX had a different gearbox than US? Need to investigate.

Thanks for your help!


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 Post subject: Re: Inflated numbers from VirtualDyno?
PostPosted: Tue Nov 12, 2019 10:56 am 
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RomRaider Donator

Joined: Fri Sep 02, 2016 4:42 am
Posts: 504
Location: Riga, Latvia
So it is EDM wrx 08.
Yes, they have different numbers:
USDM - TY758VW1AA
EDM - TY758VE1AA

USDM one is for sure 3.9 final drive but the EDM transmission appears to be indeed a 4.44 final drive box judging by the scarce info on internet (found some info in Russian forums). Not sure if there aren't more differences in gear ratios. Those you could check empirically with the calculator though.

EDIT:
These might be the gear ratios for TY758VE1AA
1 - 3.166
2 - 1.822
3 - 1.296
4 - 0.972
5 - 0.738
R - 3.333

Looks the same as for the US box.


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 Post subject: Re: Inflated numbers from VirtualDyno?
PostPosted: Tue Nov 12, 2019 11:18 am 
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RomRaider Donator

Joined: Mon Jun 08, 2015 4:52 am
Posts: 144
Again good info trez0r!

I checked a 3rd gear log, and it shows 130kph at 6400 rpm, which, assuming 4.444 final drive, would mean ~1.33 ratio for 3rd gear.

If i want to get more precise gear ratios i should use GPS speed values though, right?
The speedometer is off by about 10-12%. (Which happens to match the 4.444/3.9 ratio pretty closely :roll: )


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