GDI Injection timing

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Avdr
TwoWaves
TwoWaves
Posts: 157
Joined: Sun Jan 08, 2012 9:25 am

GDI Injection timing

Post by Avdr »

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

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

Re: GDI Injection timing

Post by 4d »

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

Carl

Avdr
TwoWaves
TwoWaves
Posts: 157
Joined: Sun Jan 08, 2012 9:25 am

Re: GDI Injection timing

Post by Avdr »

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

Wally
OneWave
OneWave
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Joined: Thu Jan 20, 2005 11:58 pm
Location: North Yorkshire Uk

Re: GDI Injection timing

Post by Wally »

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

taho

Re: GDI Injection timing

Post by taho »

GDI Mitsubishi Carisma 1,6 1998 year.
FLS + injector voltage
Attachments
x16   injector = 0.63 ms
x16 injector = 0.63 ms
738 RPM
738 RPM

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Autonerdz
TwoWaves
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Re: GDI Injection timing

Post by Autonerdz »

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

taho

Re: GDI Injection timing

Post by taho »

- 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
Curent injectors + signal fuel pressure
Curent injectors + signal fuel pressure

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