Android and iPhone dyno!

[scarceller]

I've been using PerfExpert app for Android devices (also iPhones) and must say that this dyno tool is very accurate! I'm impressed, I don't think it's a replacement for a dyno but certainly is worthy tool to use for performance mods and quick testing.

You can get it here:
Home - PerfExpert

It's very important that you model the car correctly in the setup section. Things like gear ratios, weight, tire sizes, ... if you get this correct the tool is extremely accurate. It came within 2% of actual dyno runs for my setup!

Here's a run I did this weekend with my motor using stock AFM, custom injectors and a tuned chip I developed.
https://network.perfexpert-app.com/results/uaH1vrc6hH
The app even publishes the results to a private website as seen in the above link.

That torque curve looks nearly identical to my curve from my motor on a dynojet.
I highly recommend the app.
Very neat indeed.

[tirwin]

Nice find, Sal!

Thanks for sharing.

[scarceller]

The important parts to using and setting up this app:
1 - Model the car correctly in the setup section
2 - Find very straight and flat stretch of road and do all testing at the same site and leaving from the same spot
3 - Avoid windy conditions
4 - Avoid wheel spin, since testing is done in 2nd gear this should not be an issue for Normal Aspirated cars. You can also do 3rd gear pulls but I don't recommend those speeds on the streets.

It's amazing the technology we have available to us today!

[cwinters01]

Very cool, thanks for sharing!
cw

[KTL]

Sal,

Is the tire size you used correct- 245/50-16? Typically we use a 245/45-16 and the theoretical diameter, actual diameter and the rolling/loaded diameter are all different values.

[scarceller]

Yes, my car is a screw ball on the rear tires, PO installed 245/50/16s. I plan to remove those tires and replace with factory spec 225/50/16s at the rear. It's a early 84 widebody with 7 front and 8 rear rims.

Originally Posted by KTL

Sal,

Is the tire size you used correct- 245/50-16? Typically we use a 245/45-16 and the theoretical diameter, actual diameter and the rolling/loaded diameter are all different values.

[scarceller]

I also failed to mention that the app gets realtime weather data for the SAE corrections. Another cool feature.

[scarceller]

Here's an old dyno run from my setup with AFM, stock injectors and custom chip. You can compare how close this run is to the dyno app run I did this weekend.
https://network.perfexpert-app.com/results/uaH1vrc6hH
The torque curve looks very much correct. The blue lines are with stock chip, the red with perf chip.

The run online I did this weekend has a few more improvements at hi-RPMs so it pulled a bit better HP.

[cabmandone]

I'm going to have to try this out!
Do you think it would be adequate for the baseline you'd want for a custom chip or should I still bring it to a shop and have it dyno'd?

[scarceller]

Originally Posted by cabmando

I'm going to have to try this out!
Do you think it would be adequate for the baseline you'd want for a custom chip or should I still bring it to a shop and have it dyno'd?

I think it would work great for a chip baseline and then the after chip. Just be sure you use the same exact setup and run procedure. You should do the baseline run a few times on different days but from what I see so far I think this app will work well for baselines of before and after changes. I plan to do exactly this with the app soon. I plan to do a few comps:
1 - My engine with stock injectors and AFM with stock chip
2 - My custom 6 hole injectors with stock AFM and my matched chip (Already did this run)
3 - My full MAF system
I'd like to see those 3 test cases and graph them against each other.

[VFR750]

Where did the Cd*A number come from?

Looks like an interesting app.

[Tippy]

Originally Posted by tirwin

Nice find, Sal!

Thanks for sharing.

If Sal is confident, I'm confident.

Thanks for verifying an app, Sal!

[scarceller]

Cd*A is a coefficient of air drag based on frontal area of the car. I used the default for now but am discussing this with the Apps creator to better understand the number.

The docs say this about the number:
Frontal area in meters squared calculated by this Cd*A=Height*Width*0.82
Where height and width is in meters.
I don't really understand why they use a default of 0.57 as this seems way to small for any car? The 911 measures about 1.6m*1.2m*0.82=1.57 so I'm not sure about why they suggest a default of 0.57? I'm trying to get this answered. But with the default 0.57 the results do match real dyno results very closely. Will keep you posted on what I learn about Cd*A.

Originally Posted by VFR750

Where did the Cd*A number come from?

Looks like an interesting app.

[sleepy911]

Looks interesting. Are you anyway involved with this app? Besides an end user.

[VFR750]

Cd for our impact bumper cars is ~0.4 with spoiler and tail

So 1.57*.4 = .63

I'll use .63 verses the .57. Makes sense small car but poor drag coefficient.

[ganun]

Sal, How come the torque and hp curves don't cross at 5400 rpm, what am I missing?

[J-Mac]

Originally Posted by ganun

Sal, How come the torque and hp curves don't cross at 5400 rpm, what am I missing?

They do. check the scale on the right, power, versus the scale on the left, torque. Put your cursor at 5400 RPM.

[ganun]

Thanks, yes, offset scales l and r

[scarceller]

I'm just an end user.

Originally Posted by sleepy911

Looks interesting. Are you anyway involved with this app? Besides an end user.

[scarceller]

The author of the app looked up the wide body 911 84-89 and says to use 0.725 for Cd.A I changed to this value and it upped the numbers some but not that much. The important thing is once you pick this number stick with it so you can compare before and after changes.

Originally Posted by VFR750

Cd for our impact bumper cars is ~0.4 with spoiler and tail

So 1.57*.4 = .63

I'll use .63 verses the .57. Makes sense small car but poor drag coefficient.