Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - What is the relationship between lean burn, timing and octane?

rmay635703 · 10-17-2015, 11:58 AM

After a long and unfruitful search for a 3d BSFC chart that includes AFR in it I have now turned my sights on a question I have long had.

What affect does running leaner than stoich have on timing and octane?

When I look on this subject I get conflicting information,

One article says timeing has to be advanced because of the slower flamefront, others say that it causes knock and needs to have timing retarded.
Maybe its both?

Odd afront to this is that many seem to believe lower octane fuel helps with lean burn but if you get knock how can this be true.

So what is it?

Thanx
Ryan

Interesting read

http://energy.gov/sites/prod/files/2...dge_2013_o.pdf

http://www.google.com/url?q=http://g...J5StsssBp-10_A

10-17-2015, 11:58 AM	#1 (permalink)
rmay635703 home of the odd vehicles Join Date: Jun 2008 Location: Somewhere in WI Posts: 3,891 Silver - '10 Chevy Cobalt XFE Thanks: 506 Thanked 867 Times in 654 Posts	What is the relationship between lean burn, timing and octane? After a long and unfruitful search for a 3d BSFC chart that includes AFR in it I have now turned my sights on a question I have long had. What affect does running leaner than stoich have on timing and octane? When I look on this subject I get conflicting information, One article says timeing has to be advanced because of the slower flamefront, others say that it causes knock and needs to have timing retarded. Maybe its both? Odd afront to this is that many seem to believe lower octane fuel helps with lean burn but if you get knock how can this be true. So what is it? Thanx Ryan Interesting read http://energy.gov/sites/prod/files/2...dge_2013_o.pdf http://www.google.com/url?q=http://g...J5StsssBp-10_A