GDI Injection timing

Ask for and share advice on using the PicoScope kit to fix vehicles here.

GDI Injection timing

Postby Avdr » Fri Dec 14, 2012 5:21 pm

Hi all,

I was thinking a couple of days ago about GDI, and started to wonder what the timings would look like in terms of injection, with respect to ignition and TDC. Has anybody worked on such a system?

I haven't got a specific problem or anything, just curiosity.

Thanks
Avdr
Guru
Guru
 
Posts: 156
Joined: Sun Jan 08, 2012 9:25 am

Re: GDI Injection timing

Postby 4d » Mon Dec 17, 2012 8:42 pm

Do you mean the 2 different modes of injection i.e stratified and homogenous?

Carl
4d
Newbie
 
Posts: 7
Joined: Wed Jan 28, 2009 5:44 pm

Re: GDI Injection timing

Postby Avdr » Tue Dec 18, 2012 5:42 pm

I hadn't even thought that far into it to be honest, I was meaning more generally, say at what amount of degress BTDC would injection commence?

With indirect injection the mixture must spend a relatively long time doing no work - as a result of the fact fuel must be injected before the inlet valve closes.
With GDI this is ofcourse not a factor, and fuel could be injected at any time during the inlet or compression stroke; allowing for valve overlap and providing injection was complete before combustion chamber pressure became too high.
So whats the average point of injection in such a set-up?

Thanks
Avdr
Guru
Guru
 
Posts: 156
Joined: Sun Jan 08, 2012 9:25 am

Re: GDI Injection timing

Postby Wally » Tue Dec 18, 2012 11:16 pm

It would be Interesting to know about the GDI.
I have done a bit of work on a 4.6 quad cam with an after market race ECU that was fully programable. We found on the rolling road that the point of injection did not make much differance to the running of the engine but it was a little more economical when the fuel was injected onto the back of the closed inlet valve and had a few more bhp when it was injected after the valve had opened on the inlet stroke. The only thing we did notice was how much smoother the engine was at idle when the ecu was on sequential injection compared to a batch fire mode, at revs you could not tell without the rolling road.
This ecu also had the degrees before tdc for the end of injection, so in effect the longer the injection duration (as you put your foot down) the sooner it started, and the higher the revs the sooner it started as the engine would have rotated further during the same injection period.

Wally
Wally
User
User
 
Posts: 18
Joined: Thu Jan 20, 2005 11:58 pm
Location: North Yorkshire Uk

Re: GDI Injection timing

Postby taho » Wed Dec 19, 2012 1:10 am

GDI Mitsubishi Carisma 1,6 1998 year.
FLS + injector voltage
Attachments
Mits_car_03.gif
x16 injector = 0.63 ms
Mits_car_01.gif
738 RPM
taho
User
User
 
Posts: 33
Joined: Sat Jun 12, 2010 11:49 pm
Location: Ukraine, Kiev

Re: GDI Injection timing

Postby Autonerdz » Wed Dec 19, 2012 6:04 pm

Just some words of caution when hooking up to these....

Many manipulate both sides of the injector with high voltage. Make sure any and all grounds are attached to battery negative. This is essential at all times but especially when you are using attenuators. The scope must be grounded for the attenuators to be effective and offer any protection.

Placing a channel input like A on positive and B on negative of the injector will then allow you to deploy a math channel A-B to see the voltage drop across the injector so you can really see what it is doing. At no time place a channel ground on the injector.
Tom Roberts
(The Picotologist)
Autonerdz
User avatar
Autonerdz
Zen Master
Zen Master
 
Posts: 272
Joined: Wed Nov 20, 2002 4:19 pm
Location: Washington State USA

Re: GDI Injection timing

Postby taho » Fri Dec 21, 2012 2:26 am

- it will be necessary to take a good way on "arms". But at the moment of measurements was only Pico4223. The channel A, it was not connected to any wires. It completely agree that such measurements should be spent with full comprehension of carried out actions and great attention to safety. (As sometimes speak - do not repeat all that you have seen on the screen TV) :)
...
26.12.2012 Has corrected an error in calculations :?
Attachments
21-12-2012 3-41-09.jpg
Curent injectors + signal fuel pressure
taho
User
User
 
Posts: 33
Joined: Sat Jun 12, 2010 11:49 pm
Location: Ukraine, Kiev


Return to Diagnostic discussion

Who is online

Users browsing this forum: No registered users and 0 guests