Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post

ecoxantia · 10-01-2008, 05:57 AM

Thanks for the reply dcb, having had a look at the code you have my utmost respect!!

Pressure - red line above- this is the pressure of a common rail - a foot long forged steel pipe in other words - some way from the injector itself. I wouldn't have thought its any kind of pwm, certainly not read about anything like that. Basically there's a 3 piston pump that provides the pressure and the pressure is as high as the pump can manage without wasting too many kw! More recent HDi engines apparently have even higher rail pressures.

So I think the blips are a pressure wave from the injector opening and closing. There's one for the pre-injection and one for the main injection - interesting but a "red herring" for my purposes.

20 volts was measuring away from the duino, in the engine bay!! 20V is the limit of my scope...

Thanks for the atmega on/off voltages - shame that the decay is quite slow (shallow slope) and I wonder if that's why at idle the us displayed varies quite a lot.

I agree that the duino does not seem to be measuring what I want. I'll try some signal conditioning and see what happens. It may only be measuring the pre injection, I don't think the scope always shows the rapid drop in signal.

I'm doing analogread on the red line, the rail pressure, by the way. I'll check that out on the bench with a power supply next.

10-01-2008, 05:57 AM	#41 (permalink)
ecoxantia EcoModding Apprentice Join Date: Aug 2008 Location: UK Posts: 104 Fizz - '06 Skoda Fabia Combi TEAM VW AUDI Group 90 day: 56.62 mpg (US) Thanks: 3 Thanked 9 Times in 7 Posts	Thanks for the reply dcb, having had a look at the code you have my utmost respect!! Pressure - red line above- this is the pressure of a common rail - a foot long forged steel pipe in other words - some way from the injector itself. I wouldn't have thought its any kind of pwm, certainly not read about anything like that. Basically there's a 3 piston pump that provides the pressure and the pressure is as high as the pump can manage without wasting too many kw! More recent HDi engines apparently have even higher rail pressures. So I think the blips are a pressure wave from the injector opening and closing. There's one for the pre-injection and one for the main injection - interesting but a "red herring" for my purposes. 20 volts was measuring away from the duino, in the engine bay!! 20V is the limit of my scope... Thanks for the atmega on/off voltages - shame that the decay is quite slow (shallow slope) and I wonder if that's why at idle the us displayed varies quite a lot. I agree that the duino does not seem to be measuring what I want. I'll try some signal conditioning and see what happens. It may only be measuring the pre injection, I don't think the scope always shows the rapid drop in signal. I'm doing analogread on the red line, the rail pressure, by the way. I'll check that out on the bench with a power supply next.