ignition timing

[seth]

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

 

[SnoMan]

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.

 

[seth]

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

 

[SnoMan]

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.