Mustang vs. Dynojet (not the usual question)
07-28-2005, 03:44 PM
#1
Mustang vs. Dynojet (not the usual question) My question relates to how the car runs with different loads on the tires.
My car was tuned on a mustang dyno and the a/f was about 12.6:1. Put it on a dynojet (different shop) a few days later and it was lean @ 14:1 . Put a wideband on the car on the street and it was 12.7:1.
If this is normal, how are people really dialing in a car on a dynojet? Does every car that is tuned on a dynojet run richer on the street than it did on the dyno? Or do professional tuners have a way of correcting for this?
I tried asking the dynojet operator about this but he didn't really know what I was talking about w/ different dynos. He said he could change the load w/ his and nascar uses dyojets so that's good enough for him, lol.
Craig
My car was tuned on a mustang dyno and the a/f was about 12.6:1. Put it on a dynojet (different shop) a few days later and it was lean @ 14:1 . Put a wideband on the car on the street and it was 12.7:1.
If this is normal, how are people really dialing in a car on a dynojet? Does every car that is tuned on a dynojet run richer on the street than it did on the dyno? Or do professional tuners have a way of correcting for this?
I tried asking the dynojet operator about this but he didn't really know what I was talking about w/ different dynos. He said he could change the load w/ his and nascar uses dyojets so that's good enough for him, lol.
Craig
07-30-2005, 10:01 AM
#3
On The Tree
This is the problem with some of the "inertia only" dynos. When you tune using a inertia only system, make sure you find out what the simulated inertia is. Some systems are in the 3600lb range, and some are much less. When you tune to lesser weight than the car, you typically end up too lean, and too much timing. The more weight the motor (and wind drag) has to pull, the higher the chamber temps. This is just one of the reasons a loading capable dyno with ROAD LOAD SIMULATION (Dynomite, Superflow, Mustang) is the only way to tune. You are tuning for the weight and drag of your car with you in it. Some people knock these dynos due to inconsistent results...(typically operator error) These type of dynos have an enormous learning curve that comes with operating them. As long as they repeat (consistent results whether it is high or low), they are the best for tuning. The next time you wind out 2nd, 3rd, or 4th, take notice to how long it takes you to run through the gear. When you get onto the dyno, compare the time (trying to match RPM as close as possible).
Another problem that can arise is not performing a "free air calibration" on the 02 sensor before the tuning session. All it would take is one "accidental" 02 calibration done with the sampling tube not in a "clean" air source to ruin your data.
Simple guide to follow is not to focus on the peak number. Try to focus on a consistent, accurate and repeatable test procedure. Match the load, fluid temps, tire pressures, tie down (straps) pressures and plenty of ventilation (you can never have enough fans). As long as the machine repeats, then tune looking for increases in performance. Then go to the track to hopefully confirm your work!
My 2 cents....
Another problem that can arise is not performing a "free air calibration" on the 02 sensor before the tuning session. All it would take is one "accidental" 02 calibration done with the sampling tube not in a "clean" air source to ruin your data.
Simple guide to follow is not to focus on the peak number. Try to focus on a consistent, accurate and repeatable test procedure. Match the load, fluid temps, tire pressures, tie down (straps) pressures and plenty of ventilation (you can never have enough fans). As long as the machine repeats, then tune looking for increases in performance. Then go to the track to hopefully confirm your work!
My 2 cents....
