Using different widebands, one for street and another for dynojet inertial dyno, we are getting about a 0.3 AFR difference, with the dyno reading rich as compared to the road. Anyone else experience this? Is this to be expected due to the lower load with the dyno as compared to the street?

I have read threads on this forum about this topic but do not recall anyone mentioning the difference. Folks have mentioned to tune rich on the dyno and then expect it to run leaner on the street, looking for data.

 

This seems like a dumb suggestion, but why not eliminate a variable and use the same wideband on both?

Brian

 

Temperature can play a part in the differences if you are using the same wideband sensor. There is a correction map for temperature and barometric pressure.

Also, you tune rich so you take into consideration uncontrolled variables like different grades/quality of pump gas and temperature variations.

J

 

Thanks for the critique?

I was hoping for some data ...

 

Gordon,

You say you add fuel when intake temps go over 15 deg? My maps remove fuel as intake temps rise, ignition retards as well. I have been considering altering this logic a bit given the useless intake air temp sensor/location on the third gen. The sensor seems to measure intake manifold temp instead of intake air temp. Still debating relocating the sensor.

Kyle

 

For street tuning, nothing is going to be better than tuning on the street. Kinda hard to have a fan pushing 70-130mph winds! Providing you have all critical gauges like fuel pressure, oil pressure, water temp. and of course a nice wide band.

 

if you use the proper dyno it will make a huge difference. we use a dyno pack and it can simulate many different load situations unlike a roller dyno.

 

Another reason for the difference is that actual loading of the motor.

On the street will put more load on the motor hence making it run a bit leaner. Spool charactaristics will vary a bit too... with boost coming on sooner on the road than the dyno.

I'd say tune it on the dyno first... then the road. Keep a wideband in your car all the time for safety. Things change pretty dramatically from day to day... especially season to season.

 

I have to agree that aeaodynamic forces are missing from the dyno as well, but a dyno is nice for holding constants which is hard to do on the street, but it can be done, I am fortunate to have some very long hills climbs to drive up, thats where cruise control comes nice as well, set it at 3000, hit the hill and tune away, then hit it again at 3500, yada yada yada..
As for the discrepency, that could be anything from the supply voltage of the wideband controller, right down where the sensors were mounted, and what the intake air temps of the engine were..Max

 

...

 

Relocate the air sensor like Nocab and I did.