ignition timing

I was wondering if anybody with a service manual could tell me what the
specified timing is for a 99 sl1. I have an odbII reader and it reads
that it is 20 btdc. This seems early.
Thank you
SFH

 

That is about right at a idle. On my duaghters 97 DOHC, it ranges from
20 to 40 BTDC depending on RPM and load and tempature.

 

Dosen't that seem early? I grew up on V8's and eighties toyota four
cylinders, but i have never seen anything exceeding 15 btdc. You have
seen 40? That is amazing, what is the advantage of such an extreme
advance? I thought that at that level of advance, there would be risk
of serious damage. Maybe that is why saturns ping, and get over
carboned easily.
Thank you
SHF

 

I have seen over 40 on a 1.9 DOHC engine. When you compare timing with
older engines, you are talking static timing at a idle not as RPM
increases or vacum advance is aplied. 30 to 40 degrees is quite
normal at times and needed for good fuel economy too. The actual amout
of advance will very with RPM and throttle setting unlike a old
tractor motor that strictly had mechanical advance only and timing was
predictable at various RPM's. It is a lot more complex on a modern
car. Above 45 degrees or so you can start to get missfire at part
throttle and at full throttle it would run poorly and/or knock with
that much advance. Most new eninge idle around 20 to 25 degress
advance when warmed up.