john banks

Does anyone know what duty cycle is typical at full held boost of about 13-14PSI with the standard ECU and 1.2mm restrictor at various engine speeds? I don't have the equipment to measure it and wanted an initial target to play with.

I am guessing about 70% at 3500rpm.

I believe our 2 port solenoids are closed when not under power. What maximum duty cycle do you think it would handle? 95%, 100%? I might reduce restrictor size to avoid wild duty cycles on my forthcoming setup.

[Edited by john banks - 1/13/2002 11:40:51 PM]

EMS

John,

I haven“t measure it, but I think it will be about 70% - 75% max. duty cycle.

Please note: the std. MY99 and MY00 boost solenoid produces very high voltage spikes if switched off, look out for that designing the driver for the boost solenoid! (I blew up a few Unichip boost controlers due to that reason)

Mark Verhoeven.

john banks

I would put in a diode anyway to stop the reverse EMF, but do you know what the Unichip boost controller uses?

I have my development board now, and it will convert 0-5V through its six channel ADC without any additional components - the input impedance is 10Mohms which is fine for all the Scooby sensors, so that saves me a lot of work with op amps and buffering. So all I need to do is make up a wiring harness, finish the code and make a solenoid driver circuit and then start testing.

James_PowerMad

You could measure the Duty cycle without any fancy test gear...

I would stick a potential divider across the feed to the solenoid to cut the voltage down to somewhere just below a volt (perhaps 1k and 47 ohms).

Then AC couple the signal out of the divider using a capacitor (say 10uF). It may be a good idea to put a very small capacitor in parallel with the divider output - just incase there is any small residual spike from the solenoid (definitely forget the whole idea if there is no diode across the solenoid).

Then plumb this signal straight into the Line input on yer Minidisc recorder / tape recorder / laptop.

Record the signal, and transfer to a PC. Then you can measure the relative timings of the transitions using something like Wavestudio / Goldwave etc.

Obviously you would not see the actual PWM waveform on the PC, cos' its got a DC component, but you should see where the switching edges are.

*** Note that it is probably not a good idea to power the device that is doing the recording from the cars battery!! - Just to be totally safe.