About Cam Timing for LT1 engine.

[shinysun]

I am looking into Cam Timing table.

But I found what I couldn't understand clearly as I know basically the retard is more power at high rev.

20170623_095653.png

What is it meaning in the red circled? Why is there a lot of retardation at low~mid rev?

Thank you in advance.

[rbooth]

They retard the cam for fuel economy.

[Ben Charles]

That kills low end power too

[IARLLC]

Here is something I posted a few days ago on the exact subject. It makes a big difference:

Oh yeah, cam timing. You are correct about how it should be It actually is that way. Positive numbers represent cam retard. If I remember correctly the cam is advanced 8.5 degrees at rest (0)....so it idles 8.5 advanced. (Not counting the section I refer to as EGR over-retard in the low/mid cruise) the cam is gradually retarded as RPM rises starting around 3,000 on a GEN5 6.2. I am not sure exactly what the cam retard map looks like on a GEN5 5.3. I can tell you that on GEN4 and GEN5 I have had major improvements in responsiveness by making the high baro table look a bit more like the low baro table (in a general sense). I don't mean just cutting the low baro and pasting into the high. I actually log a lot of light throttle cruise to know exactly where on the map to leave alone then I blend out of the EGR over-retard from that level down. This raises cylinder pressure in those regions quite a lot so it is important to log and adjust variable cam spark afterwards. Some like to just 0 out the whole low RPM region and that is understandable but I try to leave the areas that are not hurting power alone. Of course this step won't gain you any full throttle power but it will make for more pleasant/responsive/predictable driving with little or no loss in fuel economy. As far as full throttle I expect that the tiny cam can use more retard up top (if it starts out advanced 8.5 (reads 0) and the top of the chart it is only retarded .5 degrees (reads 9)).....but I have not tested this so I cannot speak to it.

https://www.hptuners.com/forum/showt...in-limit-table