How good is Jscan!?

[Jay Gatsby]

I also use it to raise idle for winching, or using the JT to jump start another vehicle.

School me on the jump start thing please.

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[ShadowsPapa]

School me on the jump start thing please.

Even in the early 1970s, I was taught to bring the idle up on the vehicle doing the jumping to the dead car/truck to help handle the load instead of all from the battery.
So when I jump start anything from one of my vehicles, I run the idle up, make the connections, let it sit a while (potentially to help recharge the dead car's battery), and then try to start it.
The increased idle allows the alternator to bring the voltage up, and the wait time allows the dead battery to perhaps recover a bit so the donor isn't pushing to a totally dead battery while you try to start it.
With carburetors it was simple - run the throttle up on the choke's fast idle cam.
Today, you have to do it electronically - tazer and jscan have the high idle speed feature to handle loads while running a winch. Works for jump starting, too.
Make the jumper cable connections, sit back a few minutes, then try to start it.

 

[Jay Gatsby]

…tazer and jscan have the high idle speed feature to handle loads while running a winch. Works for jump starting, too.

Thank you

 

[Sigz]

BIG BUMP:

Decided to play around with JSCAN. I have Toyo Open County At3s 12.5x50x17 that have a manufactuer diameter of 34.5.

I remember after getting the tires, I had JSCAN set to 34.75 to get the most accurate JEEP odometer vs GPS odometer.

Today having a free day off, for some reason I decided to skim the forums and another JSCAN/tire size came up - so I went down a rabbit hole.

I followed JSCAN's guide to measure the tire from the ground to a the bottom part of a level on top of the tire - which my tire measured at 34.25.

I drove around and got these results: (GPS was NOT connected to the Jeep, it was cell service only)

Jeep odometer: 9.7mi / Stride GPS: 9.93
------the scale factor: 9.93 ÷ 9.7 = 1.0237

So then I changed JSCAN tire size to 34.5 and took another drive:

Jeep odometer: 10mi / Stride GPS: 10.26
------the scale factor: 10.26 ÷ 10.00 = 1.026


So now, I will go back to 34.75in into JSCAN, but it feels so wrong.

Results:
Jeep Odometer: 10.1 / Stride GPS: 10.25
------ The scale factor: 10.25 ÷ 10.10 = 1.0149

Do I go up to 35in in JSCAN?


EDIT:

Okay I went up to 35 in JSCAN.
Jeep odometer: 10.20 mi / GPS distance: 10.25 mi
----- The scale factor10.25 ÷ 10.20 = 1.0049


CLOSE ENOUGH!

But still weird. I don't understand why a tire measuring at 34.25 needs an input of 35 to match Jeep trip odometer and GPS odometer.

Hopefully I can take a longer trip in the next day or so to verify at longer distances.

 

[MaximusTX]

BIG BUMP:

Decided to play around with JSCAN. I have Toyo Open County At3s 12.5x50x17 that have a manufactuer diameter of 34.5.

I remember after getting the tires, I had JSCAN set to 34.75 to get the most accurate JEEP odometer vs GPS odometer.

Today having a free day off, for some reason I decided to skim the forums and another JSCAN/tire size came up - so I went down a rabbit hole.

I followed JSCAN's guide to measure the tire from the ground to a the bottom part of a level on top of the tire - which my tire measured at 34.25.

I drove around and got these results: (GPS was NOT connected to the Jeep, it was cell service only)

Jeep odometer: 9.7mi / Stride GPS: 9.93
------the scale factor: 9.93 ÷ 9.7 = 1.0237

So then I changed JSCAN tire size to 34.5 and took another drive:

Jeep odometer: 10mi / Stride GPS: 10.26
------the scale factor: 10.26 ÷ 10.00 = 1.026


So now, I will go back to 34.75in into JSCAN, but it feels so wrong.

Results:
Jeep Odometer: 10.1 / Stride GPS: 10.25
------ The scale factor: 10.25 ÷ 10.10 = 1.0149

Do I go up to 35in in JSCAN?


EDIT:

Okay I went up to 35 in JSCAN.
Jeep odometer: 10.20 mi / GPS distance: 10.25 mi
----- The scale factor10.25 ÷ 10.20 = 1.0049


CLOSE ENOUGH!

But still weird. I don't understand why a tire measuring at 34.25 needs an input of 35 to match Jeep trip odometer and GPS odometer.

Hopefully I can take a longer trip in the next day or so to verify at longer distances.

It is probably because it does the calculations for you. Just like the Tazer you enter 35 and it will do the calculations for the actual tire size. I would guess that they don't expect people to go out and actually measure the tire and will just enter the number on the sidewall of the tire IE 35 when most tires are not actually the size printed on the sidewall.

 

[Sigz]

It is probably because it does the calculations for you. Just like the Tazer you enter 35 and it will do the calculations for the actual tire size. I would guess that they don't expect people to go out and actually measure the tire and will just enter the number on the sidewall of the tire IE 35 when most tires are not actually the size printed on the sidewall.

But I did measure per their instructions and it wasn’t even close.

 

[Hootbro]

I did the tape measure thing just to get me in the ballpark and then played with the settings up/down against GPS speed until it sync and called it good.

 

[Sigz]

I did the tape measure thing just to get me in the ballpark and then played with the settings up/down against GPS speed until it sync and called it good.

Do you remember which way you went?

And did you verify JT distance traveled vs gps distanced traveled?

It still seems odd to me that in order to get JT odometer to match a GPS odometer - I have to make the tire size (34.25in under load / 34.5 manufactures spec) go UP to 35in. Usually, it seems that the JSCAN tire input is LESS then manufacturers spec.

I also saw a post of yours a while back talking about the speed tolerance % and how you may need to change it. Mine was at 0% and the speeds matched up. I believe some vehicle manufactures set it around 3%.

 

[Hootbro]

Do you remember which way you went?

No, I do not remember. I just went in 1/2" increments and if I over or under shot, backed off to the nearest next increment.

And did you verify JT distance traveled vs gps distanced traveled?

Actually I did and it was like within two tenths of a mile over 30 miles IIRC.

It still seems odd to me that in order to get JT odometer to match a GPS odometer - I have to make the tire size (34.25in under load / 34.5 manufactures spec) go UP to 35in. Usually, it seems that the JSCAN tire input is LESS then manufacturers spec.

Tire manufacturers stretch the truth on their published tire size. The size is based on the maximum tire pressure on the sidewall and not normal vehicle recommended pressure. So think like 80 PSI vs. 37 PSI will make a bit of a difference.

I also saw a post of yours a while back talking about the speed tolerance % and how you may need to change it. Mine was at 0% and the speeds matched up. I believe some vehicle manufactures set it around 3%.

My understanding is 3% is the maximum allowable tolerance at time of manufacture.

 

[JTGuy]

so put a mark on the tire sidewall and on the ground. Then rotate it 1 rev and measure the distance. Then divide that number by 3.14, that is the true tire height.

 

[EXTORTION]

I really like my JScan. Ive used it on several Jeeps flawlessly.

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