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Brake pressure sensors.

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Hi,

Hoping to fit some brake pressure sensors and wondering what range people generally use. I have been meaning to sit down and work out a rough line pressure... but I have been lazy. It's for road/race car, with a booster. Tossing up between a 2000 or 3000 psi sensor.

Once I have the sensors, I would like to set up a channel on the my dash (motec c125) for a warning light to notify me when I am locking a wheel - unfortunately I don't have individual wheel speeds. I have never seen brake pressure data from a lock up before, I assume it just plateaus - would anyone have any feed back on this? Or an idea how to set up a warning channel?

I used 2000psi Honeywell sensors on my car. One for front and another for back. Come in handy when setting up brake bias on the pedal box.

I think we used 2000psi honeywell on the fsae car too. You really want wheel speed input for actual traction conditions, pressure won't tell you much other than driver response/consistency.

Thanks for the replies guys. I think we had 2000 psi on the fsae car too.

You're right about pressure and lock up. I reasoned it out a bit more after I posted the question and figured it would be very hard to be able to pick a lock up based off a pressure trace.... maybe I should move wheel speed up the priority list.

As you realised, you won't be able to discern lockup from the pressures - but as one chap mentioned, with a pressure guage, or two, you can quickly check and set brake balance. this SPA guage kit is expensive (main reason why I never bought it) but very good quality and can be set for pressure or balance - http://www.spa-uk.co.uk/Product/Brake%20Bias%20Gauge%20-%20Front%20and%20Rear%20(DG205)

I assume what made you think of this is the 'brake lockup warning light' that the Aussie race cars use? Many race series outlaw ABS but, as it is very important that wheel lockup is minimised for tyre life, many teams will use the ABS type wheel rings and senders to identify a non-rotating wheel and send a signal to a warning light, rather than an ABS servo' unit.

You may find, ir your aftermarket ECU has some form of traction control, it can be used to control a warning light - but that is conjecture and not something I have knowledge of - be interested if it is possible and has been done - anybody?

I'm sure you could trigger a digital out based on slip ratio out of bounds?

As mentioned i think you'll find it difficult to use solely brake pressure to trigger a lock up warning. However for brake pressure a 2000psi sensor should suffice.

Id use wheel speeds then a math's channels to generate FL Lock, FR Lock, RL Lock, RR Lock channels respectively.

Not sure how you configure the Motec dashes having never used their products, but i can assign each channel to a pop-up alarm on the dash, or to each corresponding warning LED on the side of the dash. The dash has 4 warning LED's on each side in addition to shift lights, so assign FL Lock to the top left one, RL Lock to the bottom left one and so on.

Once you have fitted front and rear pressure sensors, you can then do a simple maths channel to get your brake bias to show too.