Injector Timing - Porsche 993 with V88

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Hi Guys,

Trying to get my head around the injector timing and have a couple of questions.  Firstly some specs for reference.

The engine is a custom 4.0l (up from 3.6l) 11.5:1 compression, Individual throttle bodies, Big Cams, ID1000 Injectors, Alpha-N, 

Cam:  

Intake - Duration 283, Opens at 33.5 BTDC, Closes at 69.5 ABDC,  Lift 12.82 mm

Exhaust - Duration 264, Opens at 60 BBDC, Closes at 24 ATDC, Lift 12.45 mm 

Overlap 57.5 Degrees with 108 Lobe Center.

Injectors: ID 1000

Current Settings for Injector Timing: Single Zone, End of Injection, 400 BTDC, Split Off.

 

I am trying to stabilize idle a little better, I understand these cams are quite large and that Idle will always be a struggle.  Because of the injector size I was thinking that I should be able to have the injectors fire right when the exhaust Valve closes (24 ATDC) as the duty cycle at Idles is around 3% and 2.5ms duration.  From my calculations, at my 1250 Idle, the pulse width of the injector will have the engine turn approx 18.8 Degrees so well within the opening of the valve.

So, what is the setting I need to put in the table to get my injectors to fire, while the Intake valve is open and the Exhaust valve is closed given the above.  Based on how I have read the help guide the setting should be approx 335 Degrees BTDC, Do I have this right?

 

Additionally, what sort of settings could I use in the rest of the table?

 

All thoughts, Ideas and help are greatly appreciated.

 

[Scott]

Hi, 

Can you confirm your cam numbers? I would have not expected your intake cam to open at 33.5 BTDC, as this is just before the engine reaches the top of the compression stroke.

Generally with injection timing you will want to adjust the timing until you see the richest lambda reading, this indicates that the air/fuel mix is burning most efficiently. You can then use the main fuel table to adjust the actual amount of fuel being injected so that the lambda reading matches the target. 

If you find you need a different value of injection timing for idle then you can use the Table injection timing mode.

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Thanks for the reply Scott.  

These numbers are directly from my Cam supplier.  These are relative to 0 Degrees being TDC between the Exhaust and Intake Stroke, rather than TDC being 0 between Comp/Power stroke.

So are the numbers in the Injection Timing table are relative to TDC Being 0 Between the Compression/Power stroke?

[Scott]

Ah yeah, that explains it. Yes, the injection timing in PCLink are BTDC, with TDC being between the compression and power strokes.

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Just so I am clear (I am a little slow sometimes  )

400 BTDC In the PCLink (comp/power) would be the same as 40 BDTC between Exhaust and Intake correct?

In this post http://forums.linkecu.com/index.php?/topic/647-injector-timing/ there was an Injection Timing diagram posted by Ray Hall, do you have that diagram so you can post it?

[Scott]

400 BTDC In the PCLink (comp/power) would be the same as 40 BDTC between Exhaust and Intake correct?

In this post http://forums.linkecu.com/index.php?/topic/647-injector-timing/ there was an Injection Timing diagram posted by Ray Hall, do you have that diagram so you can post it?

Yes, you are correct 400BTDC in PCLink will be the same as 40 BTDC between exhaust and intake - 360 degrees apart (one engine revolution).

I'm guessing the image was the one from PCLink help, it is attached to this post.

Scott.

injector timing.pdf

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Thanks again for everything Scott.  Much appreciated.