VTEC Oil Pressure Switch Enabled

[Gernby]

I can't find any information about this option in the help files, but it is available in the S2000 and '12+ Civic Si FlashPros. I have always just left this box checked, but don't really know what it does. My assumption was that it would enable or disable a safety feature that would prevent VTEC engaging while oil pressure is below a threshold. Could you please provide more information about it?

[Spunkster]

You are correct, that is what it is for.

[Gernby]

Well, it seems that it might not be working for the S2000. I've attached my calibration, datalog, and dyno plots from last Friday when I spun a bearing. Everything was great on the first pull, but it clearly lost power most of the way through the 2nd pull. I thought it must have been due to heat build up or something, so I had the dyno operator wait a bit before doing the 3rd pull. However, the 3rd pull was a disaster. As you can see, the ECU thought VTEC was engaged, but it really wasn't. As you would probably guess, the motor is toast.

[Gernby]

Here is the datalog

[Gernby]

I realized today that my post might have come across as if I thought a FlashPro defect CAUSED my engine failure, so I want to clarify that I don't think that at all. I actually believe the root cause for my engine failure is that I've done literally THOUSANDS of these while developing this (patented) and more recently completed development on a DBW ITB setup. Another big contributor is that I really haven't paid enough attention to regular maintenance, since I view my S2000 much like a "work truck".

The reason why I posted this thread is because this is my 2nd motor to fail in this manner, and I really don't want to blow a 3rd. Once I replace this motor, I want to make sure I have whatever safety measures are necessary to insure that I catch the problem in time (oil pressure gauges, warning lights, etc.). If there is a code bug related to the VTEC oil pressure switch, then I just want to know that a fix might help me achieve that goal.

[Spunkster]

The oil pressure sensor does not tell the ECU how much oil pressure there is. It is a simple on or off switch that is activated at a set pressure. It will still activate with lower than normal oil pressure. There is no defect in the software. Many VTEC engines from other parts of the world do not have this pressure sensor.

[Gernby]

I figured the sensor was just an ON/OFF sort of thing, but I assumed that the threshold for the switch would be above the minimum pressure required to engage the VTEC locking pins. Basically, if it takes 40 PSI to lock the pins, then it seems that the VTEC oil pressure switch would only be ON when pressure is something above 40 PSI. However, both times that I spun bearings in this car, the VTEC pins would engage / disengage sporadically throughout the RPM range but the datalogs showed VTC engaged the whole time.

Either way, would it be possible to "enhance" this feature by replacing the VTEC oil pressure switch with an aftermarket unit that is "smart"? For example, if I used a simple microcontroller to monitor the oil pressure from a real sensor, and connect an output to the ECU's oil pressure switch input, would that allow me to dial in more safety?

[shind3]

It would be great to be able to wire in a GM oil pressure sensor that outputs 0-5v, then have the ECU monitor that against engine RPM. If the pressure per RPM falls below a set threshold, it could cut fuel until it looks good again and recover after a set set delay.

I am assuming the VTEC oil pressure switch input to the ECU is probably more of a binary thing and can't be routed through the ADC to measure 0-5V. So are there other 0-5V inputs that can be re-purposed?

[Spunkster]

No, this is not possible.