Racepak O2 sensor

[Willyracer]

Have added a single O2 sensor to a racepak sportmans unit.
It is mounted on the collector just after merge.
Running a BBC on C12. I know location is not the prime
Spot.

I am only taking values above 6000 for comparison since
The sensor is in the collector.
The "lowest" reading I very see is 13.8 and that is only in
High gear at higher rpm
What values should I see and does the motor load effect
The AF value. The 13.8 is lean correct? But plugs look
Ok. Haven't tried bigger jets let but will soon now tracks are
Opening up

Thanks
David

[FireSale]

13.8 is rich by around one point. Perfecto is 14.7.

[Glenn Briglio]

Originally Posted by Willyracer

Have added a single O2 sensor to a racepak sportmans unit.
It is mounted on the collector just after merge.
Running a BBC on C12. I know location is not the prime
Spot.

I am only taking values above 6000 for comparison since
The sensor is in the collector.
The "lowest" reading I very see is 13.8 and that is only in
High gear at higher rpm
What values should I see and does the motor load effect
The AF value. The 13.8 is lean correct? But plugs look
Ok. Haven't tried bigger jets let but will soon now tracks are
Opening up

Thanks
David

12.8 to 13.2 is usually ideal at WOT

[Dave Noll]

Originally Posted by FireSale

13.8 is rich by around one point. Perfecto is 14.7.

14.7:1 is only perfect for a street car on pump gas. It is a compromise that a few different factors meet @ to be stoichometric. (for emissions to make the catalytic converter work its best) USUALLY, when you mash the gas you want the AFR to drop to around 12:1 - 13:1. Different manufacturers and different cyl head designs, compression ratio's and probably several other factors determine where an engine makes its best power @.

18:1 works for mileage but sucks for power, if you can keep the fire lit.

https://x-engineer.org/wp-content/up...io-300x296.jpg

[FireSale]

Originally Posted by Dave Noll

14.7:1 is only perfect for a street car on pump gas. It is a compromise that a few different factors meet @ to be stoichometric. (for emissions to make the catalytic converter work its best) USUALLY, when you mash the gas you want the AFR to drop to around 12:1 - 13:1. Different manufacturers and different cyl head designs, compression ratio's and probably several other factors determine where an engine makes its best power @.

18:1 works for mileage but sucks for power, if you can keep the fire lit.

https://x-engineer.org/wp-content/up...io-300x296.jpg

Thanks. That got me to read more.
https://x-engineer.org/automotive-en...e-performance/

[Dave Noll]

Originally Posted by FireSale

Thanks. That got me to read more.

If you want to read more, try some of David Vizard's stuff.

[gmonde]

Originally Posted by Willyracer

Have added a single O2 sensor to a racepak sportmans unit.
It is mounted on the collector just after merge.
Running a BBC on C12. I know location is not the prime
Spot.

I am only taking values above 6000 for comparison since
The sensor is in the collector.
The "lowest" reading I very see is 13.8 and that is only in
High gear at higher rpm
What values should I see and does the motor load effect
The AF value. The 13.8 is lean correct? But plugs look
Ok. Haven't tried bigger jets let but will soon now tracks are
Opening up

Thanks
David

i have my o2,s in the collectors just at the merg and i shoot for the 13.50 in high gear @ 6000-7000 rpm ,off the line it drops to 11.0 past the 60' it climbs to11.50 -12.00,, collector readings will read leaner ,,eventually i plan to move up steam in to the leaner cylinders on each bank ,but its just a number to help you find your direction,, checking plugs will give you the best data

[Dave Noll]

Originally Posted by gmonde

i have my o2,s in the collectors just at the merg and i shoot for the 13.50 in high gear @ 6000-7000 rpm ,off the line it drops to 11.0 past the 60' it climbs to11.50 -12.00,, collector readings will read leaner ,,eventually i plan to move up steam in to the leaner cylinders on each bank ,but its just a number to help you find your direction,, checking plugs will give you the best data

The AFR trace that I get out of the Racepak in my Cougar sounds similar. Depending on the shooters that are in the carb it drops to 9:1 or 10.5:1 then goes right up to about 13:1 but then it looks like the RPM/Shift trace, its not level. Using cast iron intake manifolds and uneven length headers I'd love to have an o2 sensor in each primary header tube.OR get off my butt and build a good set of headers but then theres still the intake.

[Willyracer]

My plots look backward compare to what everybody
Is explaining The first plot was in 3500' air and the second
Was 300' air. No changes in the car at all.
The graph index for A/F is 10 to 15 at the top of the graph
The first plot has a 12.8 reading at top of 1-2 gear change
The second plot has a reading 12.1 at 1-2 gear change

Plots show lean in the worst air of the two. Am I looking
at correctly. [15 lean. 10 rich]. ? This is why I am confused by readings

Couldn't upload a higer resolution pictures

Thanks
David

[Adger Smith]

When you get tired of reading what all the experts say... Go to the track and tune your engine where it is happy.
Best ET and MPH in the conditions available.
Then hook up your gauge and let it tell you what the A/F ratio is.
Your dealing with arbitrary numbers and your engine combination may not be happy with them.
I loved it when I was dyno testing and had customers tell me the EGT and AF had to be certain numbers to make power.
Their engines usually told them something different.
When making power most engines accelerate when slightly rich at peak Tq and run up toward lean at peak HP.
In the car I like slightly rich at the gear change to produce Tq and pull off the gear.