Average opening duration Of MPI injector
Turbo Mini Forums

Hi folks I am having a bitch of a time problam solving on one of my own MPI's,

I need to know an avrage opening duration in mS for one injector on an MPI runing MEMS at normal operating temp,

I tryed to work it out from the data logs dave done but I cant figure what time scale he has done the log with

I worked it out to be 7mS +/- which seems totaly wrong ?

P.S. I know there is a PWM at some point during the opening but Im only concerened with the main event full open to full closed ?

regards,
Paul.

Edited by PaulH on 15th Dec, 2009.

7mS sounds about right.

At 6000rpm, the injectors have only a single rev to get all the fuel into the two cylinders on each port. At 6k a single rev is only 10mS.

I'm running 8-9 mS with four MPi injectors and 112hp and 12/13:1 AFR.

At idle it will be around 3-4mS.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

sorry Paul Like numpty I forgot to say at idel and 2000 rpm

It's more dependant on load than speed. As each cylinder needs roughly the same fuel each rev multiplied by the manifold absolute pressure.

So at 2000rpm sucking a good vacuum, it will be similar to idle.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

What's the opening time of std MPI 460cc injectors ? I'm talking about how many ms should I add to the spaying pulse time to get it right at say 14v.

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

I have my opening time set at 1mSec and it works OK. I'm not sure where the figure came from.

I've gone from two to four injectors, halved REQ_FUEL and did not have to make too many changes to the VE table, so it must be about right.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Thanks

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

Ahh!

that's a good nugget of info, I was looking at my PW's yesterday and was thinking they could become a problem on over run as I only have about 2mS @ idle.


anyway,

Dave has measured the MPi injectors.

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=9217

These Delphi injectors are quite fast despite high impedance coil. They exist in many flows from 400cc to about 900.

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

I don't suppose you know anything about the response time of marrelli IWP069 Pico's? i cant seem to find much on it.

Turbo Dave reckons the minimum effective opening time is 0.9ms, and I used this figure to model the injector in VEMS with a 0.3ms ramp time and 0.6ms opening time giving the 0.9ms effective opening time. Seems to work well. This is the minimum stable pulse width. Also consider that while the injector is closing, it is still flowing fuel. the ramp time is the time it takes for the injector to start to move its pintle, 0.3ms, then once the pintle is moving the injector starts to flow fuel. it takes 0.6ms to go from full closed to full open. When the injector closes, and for argument sake, it takes 0.6ms to close. the pulse width is the bit inbetween and the software calculates the fuel flow from the data configured as above, subtracting half the sum of the open and close time from the final PW calculation.

Probibly overly complicated for the question being asked

Edited by Sprocket on 30th Mar, 2010.

It's perfect Sprocket, I'm familiar with the MS way to estimate the opening time.
So this gives us 1.2ms at 14v I presume.
Would you have the numbers for 10v ?

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm