boost limiting in lower gears puzzles me, how is it limited? if by pcm control, how does it know what gear its in?

The engine control unit will know what gear the vehicle is in by looking at road speed from the gearbox sensor that feeds the speedo in the dash and the engine crank sensor for RPM.

I thought thats how it did, my mazda had multiple sensors on gearbox to know what gear I was in , but the ib5 box doesnt.

I thought thats how it did, my mazda had multiple sensors on gearbox to know what gear I was in , but the ib5 box doesnt.

Probably doesn't need to know directly. The system sees what the car is doing as seen by ABS wheel sensors, ESP inertia sensors and so forth and it is power that gets rationed. The gear isn't relevant to that. For any given value of power and road speed, torque (which links to boost) simply depend on which gear you're in.

As my mazda knew what gear it was in , I was able to apply boost target figures for each gear, factory default was limiting boost in 1,2and 3 from what I remember, steering angle also limited throttle output. Remap set all gears to same boost curve. Driver input was required more when 320hp on tap in front wheel drive

As my mazda knew what gear it was in , I was able to apply boost target figures for each gear, factory default was limiting boost in 1,2and 3 from what I remember, steering angle also limited throttle output. Remap set all gears to same boost curve. Driver input was required more when 320hp on tap in front wheel drive

Looks like having taken the restriction away - presumably all done on a dyno, so tyre road interface wasn't in the way - you then had to do the equivalent action with your foot. I don't know what the weight of your car was but if say 1200kg, presumably you got wheelspin to about 60mph or more?

just over 1500kg, if you just floored it then wheel spin in 1st and second ,and sometimes in 3rd in damp conditions, wasnt a wise move to be honest, should have left it alone in lower gears.

left it as it was and used throttle accordingly to progress quickly without spinning up.

not got that issue now with 1.0 ecooboost. lol

The maths says that even the 100 Eco should get wheelspin in 1st in the dry if unrestricted so whether a restriction is built in or done by traction control the result should be much the same.

Hi 🙂 

came across this thread through google  😄 so I decided to share with you my experience 🙂 

mine is fiesta mk8 100ps automatic, all stock, using an OBD adaptor and a relevant app I monitored boost pressure , my boost pressure reached 1.2 bar at maximum, never gone anywhere above 🙂 thats about 17psi , I managed to get that boost starting from 3rd gear, but on the first and second gears its less than 1 bar , too much for a stock 1.0 ecoboost that is only 100ps 🙂 

1.25 - 18 psi bar maximum - 1.3 bar overboost stock (first picture).

1.4-1.6 around 20.5-22.5 psi modified (second picture).