TIMSPEED

Using a $$$ Wideband O² Sensor borrowed from a fellow forum member, I took some numbers off my truck. Do these numbers look pretty good:
Idle in Drive (750rpm) = 14.2:1
45mph cruise (2200rpm) = 14.5:1
WOT (From a 55mph roll - 100mph; 3000rpm-5000rpm) = 11.3:1
Should I tune out my WOT fuel curve? I know this isn't a vette, but I feel better talking to you guys about this. (Since most of you know about this stuff.)
Motor:
-355cid .040 Block
-9:1 Cast Silvolite Pistons
-#882 Heads (Cleaned up)
-GM Cam (194/204 duation)
-Edelbrock Performer Intake
-Holley 600cfm 4160 Carb (Vacuum Secondaries/Electric Choke)
-Hedman 1 5/8 Headers with True Dual 2½" Exhaust
The motor is advertised to make 225rwhp/300rwtq.

65Z01

When I had my L98 on the dyno the operator told me that my 12.6:1 ratio just about right, so I think you could use an AFPR to lean out WOT mixture a bit.

TIMSPEED

Thanks for responding Jim :cheers:
It's not fuel injected though. :reddevil Gotta swap out the main jets for smaller ones. The other numbers look good though, yes?

Darkness

Yes the #'s look pretty good for a carbed motor, in fact, if you can put just a tad smaller jet to lean it out a little in the WOT you could see some surprising power increase. Going from 11.3 to about 12.5 you'd gain a lot actually.

Later

TIMSPEED

So, by just changing out the secondary jets, it will lean out my WOT A/F Ratio? If so, then that's the plan :D

Aaron's 87

The only way to know if 12.x-13.x:1 at WOT is better than 11.3:1 is to change your jets and timing accordingly then run the truck at the track. Different motors like different fueling. There is no magic number.


[Modified by Aaron's 87, 10:53 AM 6/17/2003]

tpi 421 vette

11.3:1 A/F ratio is pretty rich. Like Aaron said there is no magic number, but you want to be between 12.5-13.0, naturally aspirated. It will make noticibly more power.

jburnett

Naturally aspirated motors at WOT tend to like 12.8-13.0 at torque peak and 13.0-13.3 at horsepower peak. With a FAT 11.3 A/F at WOT you're leaving quite a bit on the table. Your part throttle and idle numbers are remarkably close for a carbed application. 14.7 is stoichiometric and is the industry ideal for idle and cruise. However, if you have a big cam a lot of times they don't really like idling that lean and will clean up if you add a little fuel in.
-Jeb


[Modified by jburnett, 7:58 PM 6/17/2003]

Aaron's 87

14.7:1 is ideal only for the cat. Each motor and driver will have a different ideal for idle, response, power, safety. Lean it out, time it accordingly, and you may not find as much difference as you think.

TIMSPEED

Thanks for all the replies guys! I'm gonna pull the carb off and pull the secondary fuel bowl and replace the jets (whatever size they are, I'm going down 2 sizes)
Yeah, I can't believe I got the idle and cruise tune so good! Freakin NAILED it @ 14.5:1!! There used to be a little hesitation off idle...well, come to find out..it's because it was idling at 18:1 A/F Ratio! :eek: The idle is gone now and it seems like it's much more reponsive. Hopefully when I tune that WOT A/F Ratio out, it even picks up a little more. (Seems to really die off up top)