OEM Cluster mod to make water temp and oil pressure gauges show actual values
02-24-2014, 11:55 AM
#26
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Having driven at least 30 different makes/models over the past decade with all my business travel and car rentals, plus the cars I have test driven, owned, etc... I can tell you that only 2 cars I have ever driven have fully sweeping coolant temp and oil pressure gauges. One was a 1993 RX-7, the other was a 1991 Miata.
MOST cars didn't even bother putting in even a dummy oil pressure gauge. Some cars the temperature gauge wasn't anything more than a "yes/no" light. MOST cars have had the exact same setup as the 8. The needle for the coolant temp swings upward as the car warms up, then hits a deadzone where coolant temp can change all it wants without any needle change.
Back in the 1990s, Mazda (among other manufacturers) had a problem with owners that see the needle a bit high or a bit low and panicking that something was wrong. They added the deadzone intentionally to stop hassle and warranty claims, etc... for the entire functional range that was considered "safe".
The part where they err'ed in doing this is that the upper limit of the deadzone is too high on most cars, AND they don't let the owners know how critically bad it is to let the needle move at all from that deadzone.
You won't find very many people on the forums that will disagree with you about wanting a fully functional gauge, but we are in the minority out there. And we take the easier route of just grabbing the data from OBD2 and ignoring the cluster gauge. Trying to hack the gauge cluster is lots of effort, unlikely to succeed, and there is an easier option available.
MOST cars didn't even bother putting in even a dummy oil pressure gauge. Some cars the temperature gauge wasn't anything more than a "yes/no" light. MOST cars have had the exact same setup as the 8. The needle for the coolant temp swings upward as the car warms up, then hits a deadzone where coolant temp can change all it wants without any needle change.
Back in the 1990s, Mazda (among other manufacturers) had a problem with owners that see the needle a bit high or a bit low and panicking that something was wrong. They added the deadzone intentionally to stop hassle and warranty claims, etc... for the entire functional range that was considered "safe".
The part where they err'ed in doing this is that the upper limit of the deadzone is too high on most cars, AND they don't let the owners know how critically bad it is to let the needle move at all from that deadzone.
You won't find very many people on the forums that will disagree with you about wanting a fully functional gauge, but we are in the minority out there. And we take the easier route of just grabbing the data from OBD2 and ignoring the cluster gauge. Trying to hack the gauge cluster is lots of effort, unlikely to succeed, and there is an easier option available.
02-24-2014, 12:13 PM
#27
Just wanted to add this as I posted it in another thread:
The circuitry in the dash cluster prevents the gauge from being dynamic. With a combination of a resistor and a diode you can control the analog hysteresis of the gauge. The reason manufacturing does this is because they don't want people calling the shops every other day wondering "why is this gauge moving above middle, is it bad, am i overheating, etc".
The way to "fix" this is to disassemble the cluster and essentially turn the parallel resistor-diode circuit after the input signal from the ECU and add an R2R ladder with a large resistor so that it creates a more linear output curve. Right now, the curve that is designed by the manufacturer is a sideways S curve if you will.
Its a fairly "common" process that is done. A similar setup (albiet slightly altered) for the fuel gauge (which is why you dont see the fuel gauge swing up and down with every bump in the road)
The way to "fix" this is to disassemble the cluster and essentially turn the parallel resistor-diode circuit after the input signal from the ECU and add an R2R ladder with a large resistor so that it creates a more linear output curve. Right now, the curve that is designed by the manufacturer is a sideways S curve if you will.
Its a fairly "common" process that is done. A similar setup (albiet slightly altered) for the fuel gauge (which is why you dont see the fuel gauge swing up and down with every bump in the road)
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