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LYNCHSTAR
23-04-2010, 19:44
can anyone tell me the afr on a piper 285 cam with standard carb.
Adey aka Ewok
23-04-2010, 20:03
same as you would want on a stock cam?
raj
23-04-2010, 20:18
what figures should the afr ideally be seeing.?
at idle? part throttle? full throttle?


now my 5 isnt set up yet, as i cant get it out on the road just yet, but at idle w.o.t when warm the afr gauge fluctuates from 10.7 - 11.1 :scratch:

when i blip the throttle and hold it at 2k it shows around 12.4 if i recall:scratch:

i need a better understanding regarding afr's to be honest
SCHWARTZ
23-04-2010, 20:30
http://www.rtoc.org/boards/showthread.php?t=4761 have a look at this :D
Rob@Backyardracing
23-04-2010, 20:31
Idle: 14.7
part throttle: around 14-13.5 depends..
WOT: 12.1 is a nice number i like to see at say 20psi, up to 12.5 for lesser boost (eg bar)..

Raj, unsure what you mean by "at idle WOT"....
HULK
23-04-2010, 20:35
Raj I have the same problem. Afrs on idle, normal driving and wot of between 9 and 11

so stripped the carb and overhauled it, cleaned it new gaskets etc... Put the carb back on and guess what??? Yep exactly the same.:cry:

but....... I have removed the idle jet, ( which looks fine and have cleaned it a million times) and fitted a different idle jet from another carb and amazingly the afrs are much better. Idle is now around 14 but normal driving is still a little rich giving me between 10 and 12s

carbs are very very complex pain in the bums
raj
23-04-2010, 21:13
Idle: 14.7
part throttle: around 14-13.5 depends..
WOT: 12.1 is a nice number i like to see at say 20psi, up to 12.5 for lesser boost (eg bar)..

Raj, unsure what you mean by "at idle WOT"....

sorry "at idle WOT" i was stating "with out throttle". i know:crap:, abit confusing when WOT is more commonly wide open throttle:cartman:
raj
23-04-2010, 21:37
so whats the best way to adjust afr's, where do i start? tweeking the mixture screw?
HULK
23-04-2010, 23:38
Mixture screw will change afrs at idle only. Wind it further in to make it leaner
raj
24-04-2010, 09:42
so basically a leaner idle is best and the afr should also get richer as the rpms rise? yes?
Nayls
24-04-2010, 09:42
i used to set my idle between 13.9 & 14.3 without any problems
TrixNFlix
24-04-2010, 10:00
so basically a leaner idle is best and the afr should also get richer as the rpms rise? yes?

:agree: I think scoff said somewhere that an idle afr of 13.9 gives about 1.5 % co2 on the emissions which is bang on, like nayls's idle.
HULK
24-04-2010, 10:13
Running mega rich at idle will make the spark plugs rather black and soggy