Dyno runs- AFR
Thread Starter
Burning Brakes
Joined: Jul 2013
Posts: 1,139
Likes: 82
Dyno runs- AFR
Got the 454 on the dyno today, had a few questions and looking for input on timing and air fuel ratio.
This LS5 is fairly stock with some gasket matching-cleanup, small roller cam, about 9:1 compression and the stock Qjet.
We have only started the engine, looked for leaks, set timing, etc. The AFR was running about 15, probably too lean. On a street engine like this what kind of number (AFR)would you be looking for? Our timing currently is about 18 idle, 37 total, and all in by 3000rpm....running stock dist and vac advance.
How critical is the location of the wideband "bungs" on the dyno exhaust? How can I calculate the difference(AFR) in the dyno exhaust and mine which is stock? Is the AFR I am seeing on the dyno really a reflection to what my engine will see on the street?
Thanks, Kevin
This LS5 is fairly stock with some gasket matching-cleanup, small roller cam, about 9:1 compression and the stock Qjet.
We have only started the engine, looked for leaks, set timing, etc. The AFR was running about 15, probably too lean. On a street engine like this what kind of number (AFR)would you be looking for? Our timing currently is about 18 idle, 37 total, and all in by 3000rpm....running stock dist and vac advance.
How critical is the location of the wideband "bungs" on the dyno exhaust? How can I calculate the difference(AFR) in the dyno exhaust and mine which is stock? Is the AFR I am seeing on the dyno really a reflection to what my engine will see on the street?
Thanks, Kevin
Race Director
Joined: Sep 1999
Posts: 11,361
Likes: 383
From: Plano TX
Location for the wideband bung is not critical. There should be at least 1 ft of pipe behind the sensor to avoid fresh air contamination. Besides that, the only thing to keep in mind is that the further the sensor is from the engine, the longer the delay until it reads the current AFR.
If you will run a stock exhaust including stock manifolds, it will run richer due to the restriction.
If you will run a stock exhaust including stock manifolds, it will run richer due to the restriction.
Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
IMHO, 15 to one A/F ratio on light throttle highway cruise is not too lean. Should optimize your fuel consumption. Some engines are even happy with 15 1/2. Just check your plugs and make sure it's good for your engine.
You should see the A/F go to about 12 1/2 to 13 to one when the power valve opens; that is, under heavy or wide open throttle, and when the secondaries open.
You should see the A/F go to about 12 1/2 to 13 to one when the power valve opens; that is, under heavy or wide open throttle, and when the secondaries open.
