***Official NV Chat Thread***
Aug 31, 2010, 11:22 PM
#3484
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Location: Vegas
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I have a question for you, this is something I have been wondering ever since I started modding and getting my car tuned.
When the car is on the dyno and they do the tuning, they do tunes for ~11.5.. the sniffer reads 11.5 and my wideband reads 11.5. I leave the shop and do some pull son the way home to see how the car feels on the road and the car ALWAYS run at least .5 ( half a point ) richer once the car is on the road. Now I have always assumed it was the difference in static air on the dyno vs actual moving air on the road, but as you state it is the same thing. Yes the dyno uses fans that are moving air at a contstant rate vs the car moving air at changing rates. But I am not an expert, can you please explain why I see the same differnce in the 10 different dyno sessions I have done with my car?
When the car is on the dyno and they do the tuning, they do tunes for ~11.5.. the sniffer reads 11.5 and my wideband reads 11.5. I leave the shop and do some pull son the way home to see how the car feels on the road and the car ALWAYS run at least .5 ( half a point ) richer once the car is on the road. Now I have always assumed it was the difference in static air on the dyno vs actual moving air on the road, but as you state it is the same thing. Yes the dyno uses fans that are moving air at a contstant rate vs the car moving air at changing rates. But I am not an expert, can you please explain why I see the same differnce in the 10 different dyno sessions I have done with my car?
Now most (if not all) load bearing dyno's have an adjustable ramp rate (DynaPak's are famous for theirs being too user friendly) and if not calibrated correctly, can cause a/f issues, or even as catastrophic as drivetrain failure, depending on the added load time. The key to being able to tune on a dyno and still being accurate on the street is calibration and setup. Although close, the factory settings are not always perfect from vehicle to vehicle. Anyone can start and stop a dyno run, so finding not only a facility but also an operator that knows their dyno is always best.
Hope that helps.
Sep 1, 2010, 08:43 PM
#3490
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I'll be there tomorrow, first time i've had thursday off in almost 6 months lol. Prolly have the clone in the car with me again too.
supertuner - I'm not really understanding your answer. I'm not sure how the dyno is going to change the reading coming out of the exhaust of the car. Both My wideband not connected ot the computer and the sniffer that is connected ot the computer are reading the same. The only difference in "ambient variables" would be the car actually moving and after 10 plus pulls its a little bit warmer in the building. Its a huge building with more than adequate venting.
supertuner - I'm not really understanding your answer. I'm not sure how the dyno is going to change the reading coming out of the exhaust of the car. Both My wideband not connected ot the computer and the sniffer that is connected ot the computer are reading the same. The only difference in "ambient variables" would be the car actually moving and after 10 plus pulls its a little bit warmer in the building. Its a huge building with more than adequate venting.
Sep 1, 2010, 09:39 PM
#3491
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I'll be there tomorrow, first time i've had thursday off in almost 6 months lol. Prolly have the clone in the car with me again too.
supertuner - I'm not really understanding your answer. I'm not sure how the dyno is going to change the reading coming out of the exhaust of the car. Both My wideband not connected ot the computer and the sniffer that is connected ot the computer are reading the same. The only difference in "ambient variables" would be the car actually moving and after 10 plus pulls its a little bit warmer in the building. Its a huge building with more than adequate venting.
supertuner - I'm not really understanding your answer. I'm not sure how the dyno is going to change the reading coming out of the exhaust of the car. Both My wideband not connected ot the computer and the sniffer that is connected ot the computer are reading the same. The only difference in "ambient variables" would be the car actually moving and after 10 plus pulls its a little bit warmer in the building. Its a huge building with more than adequate venting.
A Dyno Dynamics (even though it is an eddy current load bearing dyno) has aluminum rollers that are easier to spin than say steel rollers on a Mustang Dyno, and even though there is load being placed on the drivetrain, the ramp rate of acceleration is incorrect from the factory settings (which most people don't change), thus the in cylinder temp and egt are different, causing a slightly unburnt a/f mixture. The cooler egt has less of a scavenging effect which also leaves a bit more fuel in the cylinder discharge. Thus when on the dyno it will read slightly richer. Most Dynojet's don't incorporate the proper load (even when equipped with an eddy current) causing the same phenomenon.
Now most (if not all) load bearing dyno's have an adjustable ramp rate (DynaPak's are famous for theirs being too user friendly) and if not calibrated correctly, can cause a/f issues, or even as catastrophic as drivetrain failure, depending on the added load time. The key to being able to tune on a dyno and still being accurate on the street is calibration and setup.
Now most (if not all) load bearing dyno's have an adjustable ramp rate (DynaPak's are famous for theirs being too user friendly) and if not calibrated correctly, can cause a/f issues, or even as catastrophic as drivetrain failure, depending on the added load time. The key to being able to tune on a dyno and still being accurate on the street is calibration and setup.
wheres it at i wanna try