OBD2 scanner set up

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jluthman
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OBD2 scanner set up

Post by jluthman » Wed Jul 10, 2019 5:51 pm

I punched in some data and I wanted to see if I have done it correctly. I have a 2014 Cayman S (981 S). I think the gear ratios are here: https://rennlist.com/forums/987-981-for ... st10580765

I'm not sure why but my tachometer/hp are clearly not right in this video: https://www.youtube.com/watch?v=pJ63AjNx-QU

The shift flash seems to working - at 90% it was too aggressive and at 95% it feels pretty comfortable.

Here are the screenshots of my config (Vehicle 1 is my Cayman): https://imgur.com/a/E4TUfWf

EDIT: Forgot to specify I'm using the OBDLink LX BT https://www.amazon.com/dp/B00H9S71LW
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Harry
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Re: OBD2 scanner set up

Post by Harry » Wed Jul 10, 2019 9:54 pm

The rpm values for max torque and power look wrong. They will not be the same and a typical value for max torque and the Porsche engines are in the 4tsds.

For the gear, please check the drive ratio.

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jluthman
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Re: OBD2 scanner set up

Post by jluthman » Thu Jul 11, 2019 2:11 pm

Harry wrote:
Wed Jul 10, 2019 9:54 pm
The rpm values for max torque and power look wrong. They will not be the same and a typical value for max torque and the Porsche engines are in the 4tsds.

For the gear, please check the drive ratio.

Harry
What should the graph look like?

Which gear? The drive ratio seems to be 3.89 which is what I have plugged in. This page compliments the forum post, too: https://www.edmunds.com/porsche/cayman/ ... pecs1.html
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Re: OBD2 scanner set up

Post by Harry » Thu Jul 11, 2019 3:21 pm

Looking into the last sheet, the rpm max torque is achieved is at 4500, and max power at 7400.

On the gear calculation: in case all of wheel specs, drive axle, gear and drive ratios are fine, you should see realistic speeds in the rpm / speed diagram. Please verify this. In case this is correct, the only other source of wrong gear values are invalid wheel speed or rpm values delivered by the OBD adapter. Please check whether you get clean values here and you do not have disconnects in between.

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jluthman
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Re: OBD2 scanner set up

Post by jluthman » Thu Jul 11, 2019 3:38 pm

The speed limits on LapTimer in each gear are off by a little bit, not all that much though. I'm not sure where to look for the mistake.

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I do know there's an issue with gear 6/7 where the max rpm are 6850/4825 but I don't see a place to specify that.
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Re: OBD2 scanner set up

Post by Harry » Mon Jul 15, 2019 3:54 pm

Max rpm is not relevant. What is relevant are gear and drive ratios, tire sizes, drive axle selection, OBD rpm and speeds.

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Re: OBD2 scanner set up

Post by jluthman » Mon Jul 15, 2019 4:22 pm

Harry wrote:
Mon Jul 15, 2019 3:54 pm
Max rpm is not relevant. What is relevant are gear and drive ratios, tire sizes, drive axle selection, OBD rpm and speeds.

Harry
I know you said max RPM isn't relevant, but the max speed of gear 6/7 are incorrect because of it. Is that an issue?
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Re: OBD2 scanner set up

Post by Harry » Tue Jul 16, 2019 2:46 pm

It is not incorrect, you just can’t reach it on flat surface. Find a road steep enough and you can reach any speed. :-)

The diagram is not made to understand top speed. In case you want to simulate this, please try Analysis / Drag Simulator. You can adjust the slope by using a drag feature. Make sure you specify all required vehicle data like Cd value or front surface.

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Re: OBD2 scanner set up

Post by jluthman » Tue Jul 16, 2019 4:24 pm

What I'm ultimately trying to figure out is why the throttle/braking graphs as well as the gear/rpm versus my drive line is so far off. It's clear from the G force I'm doing one thing but the tachometer is saying something different.
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