Well, I just tried the Vectra with the 2.4 tb, and it worked straight away, with absolutely amazing pick-up... then it all went tits up and failed with a P1514 🙂
--- Sorry - big ramble ahead. It might be useful/interesting though.
From what I can find, P1514 really does seem to mean 'too much airflow for TB opening'... I guess it depends if it checks the airflow for WOT - it probably doesn't as when revving the engine hard everything was fine, so if there were some way to adjust the curve of TB opening then that might work. I think some stuff could be done with resistors between AC,AG,DH and DB but that may well end up throwing a code for a sensor 1/2 mismatch 🙁
I'm going to try messing with the MAP sensor next week (I need the car all this week and don't want to mess around with it too much!) and see if I can stop it giving the error. It looks like it doesn't need adjusting much, as it was obviously right on the edge of giving the failure, so there is some hope...
Does anyone know of any software for the ELM323-based OBDII readers that lets you access freeze-frame data? I've been using ScanTool - it has a button for it but nothing is implemented! It would be really useful to see what exact readings were causing the errors.
What I found out though:
Rough Inlet manifold pressures for 2.4L TB:
800 rpm = 33 kPa
2000 rpm = 25 kPa
3000 rpm = 24 kPa
4000 rpm = 24 kPa
5000 rpm = 28 kPa
Rough Inlet manifold pressures for 2.2L TB:
800 rpm = 32 kPa
2000 rpm = 23 kPa
3000 rpm = 25 kPa
4000 rpm = 22 kPa
5000 rpm = 25 kPa
They're all pretty rough as they're from OBDII and the scantool only updates once a second - what I need is some data logging software for the OBDII reader. Still, that shows that, as you'd expect, vacuum is higher with the 2.2tb, and the lower vacuum in the 2.4 is probably what triggers the fault.
The MAP sensor is supplied with 0v and 5v, and returns a voltage. When the engine is off the pressure is air pressure (101 kPa) and it measures 0.478v. On idle the pressure will be around 32kPa and it reads about 1.14v. It's probably not linear, but if we assume it is... We want to make it think the pressure is 4kPa less, which should be about 0.2v.
So... what we need to do is make the voltage 0.2v lower, which I reckon won't disturb the engine's map too much. The real problem is if we do it too much, before the engine starts it may think that atmospheric pressure is wrong and the sensor is broken. My knowledge of electronics isn't fantastic, but I'm pretty sure you can't drop a set voltage with resistors, and you can't get a 0.2v zener, so we probably need to use something powered. I have an idea about how to do it, but it involves 2 op-amps, resistors and a zener. There must be an easier way. Any ideas?
Does someone sell a box of tricks that's basically a programmable map? Something that you put a 0 -> 5v signal into, and it looks it up in a table and gives you that voltage out? It wouldn't be hard but surely someone must make one already??? That would solve a lot of problems.