Boost by speed ?

[efi265]

Hi guys i have a old style h partern gearbox,so no gear position. Could we do boost by speed i have setup a driveshaft speed sensor working in the ecu .or am  best to setup an undriven wheel sensor and do slip control instead cheers would you have a generic setup i could use for setup thank 

Link g4+ extreme

cheers 

Ross

[Adamw]

You can do boost by speed or gear.  Boost by gear would be preferable since you have a driven wheel speed sensor.  The maximum engine torque that the tyre can transmit is directly proportional to gear ratio as that is a torque multiplier, so gear makes the most sense for most applications.  

With boost by speed the typical strategy is to increase boost at higher speeds, but the problem with using driven wheel speed for this is if you get wheel spin the ecu will increase boost which will make it worse.    Non-driven wheel speed is better for boost by speed. 

[efi265]

Ok so if i use the dyno or log some runs and check for slip at a given duty cycle i can limit boost and add it to the boost by gear map ? 

[Adamw]

I dont see how a dyno will help, the limitation is generally the tyre to road interface - ie how much grip you have, this varies with road surface and environmental conditions. 

What I was trying to explain about gear ratio being a torque multiplier may be clearer with a basic example.  Lets say your engine makes a max of 100Nm, in top gear with a 1:1 ratio and say a 3:1 diff ratio, you will have 300Nm at the wheel.  In contrast say 1st gear is 3:1 ratio, then you will have 900Nm at the wheel in first gear. 

How much you need to reduce torque by in lower gears to maintain maximum acceleration with adequate control is really only determinable by experimentation, it will vary a lot with conditions, but generally a compromise can be found that makes the car easier to drive in a wide range of conditions.  

 

[efi265]

Ok thanks i get that