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998 Supercharged Ignition Timing


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#1 fatcatvera

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Posted 04 February 2022 - 11:05 AM

I'm building up a 998 with an M45 supercharger. It will be running a HIF44 which I am able to set up using a wideband and a camera looking at needle position; however I could do with some wiser peoples' knowledge regarding ignition timing....

 

As far as I can establish from loads of googling it seems that  the max ignition is likely to need to be around 24degrees. To achieve this I'll modifiy the max advance limit stop within a new 59d distributer so that I can run 10degrees static, advancing to 24degrees maximum. Obviously the curve in between isn't necessarily going to be ideal, but initially is this a sensible approach?

 

Is there anybody who can share what their ignition mapping is for a 998 supercharged engine? I'm fully aware that the spec of the engine will affect the finer detail, but some knowledge of what oithers have ended up with can only help

 

Thanks

 

Ray

 

Here are some pictures of the parts of the system I've made so far for those interested. Nearly finished..it'll be ready to start in a week or so:-

 

Attached File  20220110_172721767_iOS (1).jpg   50.55K   1 downloads

Attached File  20211205_191759142_iOS (1).jpg   102.07K   1 downloads

Attached File  20220110_172740187_iOS (1).jpg   89.91K   2 downloads

 



#2 MrE812

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Posted 04 February 2022 - 01:59 PM

Well, although mine is a 1293 I think the general guidelines are close enough.

I would recommend fitting a AFR/lambda gauge to ensure you aren't running the engine too lean (ask me how I know).

Needle profile will also be a factor but best to tackle this using a rolling road.

I've based my setup (MED DTAfast S40  ECU) on the following info and set my max total advance to 26 deg at and above 4000rpm.

Mucking around with the advance changed the way the car picked up revs but the AFR readings remained good so I believe this is a safe value to be able to start tuning the car.

 

Suggested settings

6-10 Deg at idle   (I set mine to  8 deg)

20-26 Deg advance at 4000 rpm

 

"Metro turbo dizzy centrifugal advance at 5000rpm is 18 to 22 degrees, Metro dizzy centrifugal advance is 24 to 28 degrees.
Add the quoted initial advance of 7 degrees (not the 6 people suggest above, and total advance with the Turbo dizzy is 25 to 29 degrees and for the Standard dizzy 31 to 35 degrees."

 

"Only figure I've got is 7 degrees at 1500rpm (without vac advance).
It would be sensible to keep the total advance always below 25 degrees at least until you've got it set up half decent and then on make small changes with lots of testing."

 

"For supercharged engines your will want your AFR 20% richer. If you are on gasoline then you will target 11.72 AFR. It is critical on a supercharged engine to not run lean."

 

Hope this is helpful in someway - check other sources in case I'm talking out ma arse.:-)



#3 fatcatvera

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Posted 04 February 2022 - 02:53 PM

Thanks for the info…tallies with all I have read and very useful that you’ve shared your ignition figures.
I’ve got a lambda meter and have used it in the past in conjunction with a camera with great success to set up SUs using the road as a dyno. Ignition is more challenging to get right though!




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