Autosport Labs

I've got an AEM 2000psi pressure sensor wired into my car, but I'm confused about how to get it reading correctly.

I've read the sensors page and it shows to set up the table with just a pure linear calibration table (0.5v, 4.5v). I've done that. But the question is what "mode" should the sensor be using?

RaceCapture 1.9, RCP Pro Mk2 with latest firmware.
Channel name: Brake
Units: PSI
Precision: 0
Min/Max: 0/2000

If I select Raw (0-5v), then the value of the channel when shown in the dashboard is basically either 0 or 1

If I select Linear, the display essentially starts at ~900psi no matter what I set the calibration table ot.

If I select Mapped, I get a weird range (0-300)

My calibration table (Volt/Scaled) looks like the following currently:

2/0 4.5/2000 4.5/2000 4.5/2000 4.5/2000

Any thoughts here? Is it possible to observe the raw voltage output of the sensor somehow? Is that what Raw is doing?

OK... Raw does appear to be the pure voltage that the Mk2 is detecting. If I alter that to show with 2 digits of precision, I see 0.45v (brake pedal not depressed) and up to about 1.1v (pedal pressed hard).

I really don't believe that my brake master cylinder is only generating 300psi of pressure. I do have some hokey line stuff going on, but I'd expect to see at least 500psi if not more -- probably more like 1000psi when pressed as hard as I can.

So, the question is -- is there some kind of wiring issue perhaps? Some other way to see if the sensor itself is unhealthy?

I think your problem is the scale. try this:
0.5v/0
4.5v/2000
4.5v/2000
4.5v/2000

with channel mode = mapped

PS14 wrote:I think your problem is the scale. try this:
0.5v/0
4.5v/2000
4.5v/2000
4.5v/2000

with channel mode = mapped

I updated the scale back to that. I think the sensor is potentially faulty or something else weird is going on. I verified a simple pot and was able to view full scale. So... I'll keep digging.

You can also simulate with a potentiometer, sweeping between 0-5v. Let us know what you find out!

brentp wrote:You can also simulate with a potentiometer, sweeping between 0-5v. Let us know what you find out!

Yeah, the potentiometer part worked. The question is what's going on with the sensor.

I was just thinking about this the other day. It's still all wired up, I just haven't focused on it because it was low on the importance scale. Getting all the CAN sorted and other things were far more important. I'll probably get back to this as soon as the transmission is repaired

a thought on what you expect to see when pushing the brake pedal. line pressure generated depends on bore, pedal ratio and input pressure. if its a race application like dual master w/bias bar I would expect to see about 250-300 psi with a firm leg push (with bias centered). Joes Racing Products has a Master Cylinder Math tech page that describes all the math in detail.

PS14 wrote:a thought on what you expect to see when pushing the brake pedal. line pressure generated depends on bore, pedal ratio and input pressure. if its a race application like dual master w/bias bar I would expect to see about 250-300 psi with a firm leg push (with bias centered). Joes Racing Products has a Master Cylinder Math tech page that describes all the math in detail.

When I initially did the testing it was using a stock master cylinder and booster on a non-running car. I have yet to do any testing with the car running at vacuum. I also may need to double check that I have a proper check valve in the booster vacuum feed, especially as my car is turbocharged. But that's an entirely different situation.

Thanks for the update!