vettenuts
December 7th, 2008, 12:25 PM
Recently dynoed my car and there were several variables so a comparison to my old setup isn't possible. Not only was there a new head/cam combination but I also had switched the gear ratio and clutch. The other major factor was the old setup was on a Dynojet and the new one was on a Mustang. I am running a DTE rear end with 3.90's vs. the old setup which was stock. DTE requires the use of 75W-140 gear oil. My old setup used Amsoil 75W-90.
Here is my question. On the day the car was tuned, it was very cool out (low 40's) and the car sat in the parking lot for 90 minutes before the tuning session. There was a road tune for about an hour and then onto the dyno which took time to set up, etc. Three pulls, about 10 minutes between pulls. If I use the outside ambient temperature between my last dyno session (70 degrees) and this one (40 degrees) I find the gear oil viscosity this time was about five times higher than the last time I dynoed the car. Even assuming that the gear oil temperature was the same and hot between the two dyno sessions, the viscosity would still be twice as much.
Does anyone have any rear world data/experience on what affect the gear oil viscosity has on the dyno results?
Here is my question. On the day the car was tuned, it was very cool out (low 40's) and the car sat in the parking lot for 90 minutes before the tuning session. There was a road tune for about an hour and then onto the dyno which took time to set up, etc. Three pulls, about 10 minutes between pulls. If I use the outside ambient temperature between my last dyno session (70 degrees) and this one (40 degrees) I find the gear oil viscosity this time was about five times higher than the last time I dynoed the car. Even assuming that the gear oil temperature was the same and hot between the two dyno sessions, the viscosity would still be twice as much.
Does anyone have any rear world data/experience on what affect the gear oil viscosity has on the dyno results?