View Full Version : A/F ratios
suicidebomb
02-22-2008, 05:03 PM
How lean can one go and still not get into detanation in a N/A engine on methanol? For instance in my sbc 406 about 4.75/1 is as lean as i have tried. I still get quite a bit of oil dilution, so i assume I am still pretty rich, but I am afraid to go much leaner for fear of burning a hole in a piston. does anyone know if I can go, say 5/1 or maybe a little more 5.25/1 and still be safe, and maybe solve some of the dilution or at least cut back on it some.
johnracer
02-22-2008, 05:15 PM
I don't really know about a/f ratios, but, if it were mine. I'd tune it to run the best and quit worrying about it...
suicidebomb
02-22-2008, 06:43 PM
4.75/1 was its best E.T. and speed to date, and I would like to try it leaner, but I am worried about burning my engine down. However, I still appreciate your input, thanks.
zipper06
02-22-2008, 10:50 PM
4.75/1 was its best E.T. and speed to date, and I would like to try it leaner, but I am worried about burning my engine down. However, I still appreciate your input, thanks.
Where did you get these #'s from?, you need to run an EGT and keep the #'s around 1100 degrees on topend. if you go leaner than that you will burn something down.
JMO
Zip.
johnracer
02-23-2008, 03:15 AM
Don't be afraid to lean it out. You'd have to go really, REALLY lean to hurt it unless you're running nitrous or some sort of forced induction with a lot of boost....
johnracer
02-23-2008, 03:21 AM
Another thought, if you're injected, the oil delution could be the barrel valve adjustment, or running the engine too cold w/carb or injection...
Tod74
02-23-2008, 04:24 AM
Like ZIP said you need an EGT.
suicidebomb
02-23-2008, 04:35 AM
Where can I get an EGT?
Tod74
02-23-2008, 04:37 AM
http://www.ronsfuel.com/accessories.cfm
zipper06
02-23-2008, 08:41 AM
Also here for duel setup $300.00
Zip.
http://www.exhaustgas.com/ProductDetail.asp?ProductID=703&DepartmentID=14&CategoryID=71&BasketID=&MenuID=sub2&RepID=
johnracer
02-23-2008, 11:55 AM
I'm sure MANY will disagree with this statement, but egt's aren't of much use until you know what your combo likes. Probe location, tube diameter & length, port design etc will effect the egt numbers. No one can say " x degrees is perfect". Once you tune your combo for max performance, whatever egt you have then is yours. Until then, the numbers don't mean much....JMO
tyster
02-26-2008, 08:00 AM
I'm sure MANY will disagree with this statement, but egt's aren't of much use until you know what your combo likes. Probe location, tube diameter & length, port design etc will effect the egt numbers. No one can say " x degrees is perfect". Once you tune your combo for max performance, whatever egt you have then is yours. Until then, the numbers don't mean much....JMO
EXACTLY!!!!!! EGT's are just a reference point and NO two vehicles or Combo's will be the same. Tune for max Performance and see where the EGT's are.
I was a Diehard EGT man, gave the O2 a shot and love it! The EGT will read different from header to header and the O2 stays the same.
5/1 AFR is still on the fat side. FWIW mine likes 5.6/1 on Motor and 5.9/1 when i spray it. When I spray I enrich with Race Gas though.
Your best tool of all is you Plugs, reading them will tell you exactly where your at.
.........................Tyster