Boost Limiting By Gear - JB4

[corbs09]

Hi guys,

For those of you using the JB4 and Bluetooth app, do you have boost reduction in first gear? This is specific to the BT app, and not using the dash controls.

I am trying to figure out what value to put in the app, and if the value I should be putting is the boost target I want (i.e 18), or the amount of PSI I want the boost target reduced by(i.e 3psi).

I am also looking for the limitations of this, so how many # of boost can I reduce the total number by?

Thank you!

[Mike@N54Tuning.com]

You enter the boost cap for that gear. So 15 would limit boost in that gear to 15psi. The JB4 is set not to allow you to limit boost below stock levels, currently. So if you enter 15psi and the DME wants 18psi, you still get 18psi.

Mike

[Patrón]

Originally Posted by Mike@N54Tuning.com

You enter the boost cap for that gear. So 15 would limit boost in that gear to 15psi. The JB4 is set not to allow you to limit boost below stock levels, currently. So if you enter 15psi and the DME wants 18psi, you still get 18psi.

Mike

do you happen to have stock peak boost figures for 1st gear and 2nd gear?
asking for a friend.

[blackbeast06]

How do you set the boost limits with the gauges on the in dash menu? What would the tachometer need to be set at to have stock boost levels for 1st gear?

[Fast4d]

stock boost in 1st and 2nd gear.no limit in 3rd.

[Mike@N54Tuning.com]

Originally Posted by blackbeast06

How do you set the boost limits with the gauges on the in dash menu? What would the tachometer need to be set at to have stock boost levels for 1st gear?

Should be 0-5000rpm is a 0-20psi cap. I think in the newest firmware though they made it 0-5000rpm is a 0-25psi cap.

Mike

[FriedPiston]

With R-compound tires or better, there is usually no need to set a boost limiter beyond 1st gear at 8-10 psi. Over the last 30+ logs I've collected, I always see the actual Boost values shooting over Target Boost with the JB4.

For example, if I set the boost limiter to 8 psi, the actual boost value will be somewhere between 10-12 psi... Actual boost values eventually stabilize as soon as wheel spin is eliminated.

[corbs09]

nars3000 thats odd as it was referenced above that it will not go below the DME target boost, which should be well above 8 in first. I set mine at 18.1 yesterday at the 1/8 mile track and was able to hit 1.7x 60 foot on street tires using lc.

[FriedPiston]

Originally Posted by corbs09

nars3000 thats odd as it was referenced above that it will not go below the DME target boost, which should be well above 8 in first. I set mine at 18.1 yesterday at the 1/8 mile track and was able to hit 1.7x 60 foot on street tires using lc.

That's an excellent launch on street tires! Either the track was prepped extremely well, or your tires are running low on tread, or a combination of both.

Mike is 100% correct, and as confirmed by Terry and the BMS gang here: https://goo.gl/vB2fKT

I got the DME_BT mixed up with actual boost values. See example below with 1st gear boost limit set to 10 psi: