To better understand the nature of this platform and test my A/C theory I monitored a long freeway drive last night. Road was pretty empty so there's not many variables other than long gently rolling hills; figured it'd be a prime opportunity to spot some trends and get my geek on.
Spent about 150 miles on cruise, set at 74mph (around 2400 RPM).
Ambient temperature was a steady 73 degrees.
Watched oil temp on the cluster readout and the following gauges on my JB4: boost, timing, IAT, and water temperature.
Oil temperature was rock solid at 217F the whole time. Pretty sure this is accurate and the monitor is good because I generally watch this all the time when I'm driving and it changes as I'd expect it to.
The car mostly used timing to adjust for load as the hills rolled, keeping boost fairly steady at 1psi. Every now and again boost would drop as low as 0.7 or as high as 1.3 but generally hovered between 1.0 and 1.1 pounds.
Timing would go as low as 12.5 on the steeper inclines and as high as 21 degrees on the downhills.
Water temps varied from 204F to 208F. Getting higher on the way up a hill as expected because the engine is having to work harder and produces more heat. And dropping quite quickly as soon as the hill crested and we headed back down.
The most interesting thing for me is that IAT followed timing and was more or less unaffected by other things, most notably water temps. I expected the radiator to have some impact, but maybe with constant airflow across the front it's minimal; probably a different story at lower speeds and/or in traffic.
IAT on the inclines (12.5 degrees of timing) would generally get down to about 86 but climbed as high as 96 on the declines (21 degrees of timing). I figure it's air flow (cruise control was modulating the throttle, in retrospect I wish I had watched that as well). Just cause there's a consistent 1psi of boost doesn't mean the air moving at the same speed. Maybe it's exhaust temps causing the turbo to heat the air more?
Last trend of note, I turned the A/C off for a little while (had it running most of the trip). It took about 10 minutes, but IAT dropped about 5-6 degrees across the board. Where IAT was bouncing between 86 and 96 as mentioned above, they changed to 80-91 after about ten minutes with the A/C off. I don't know how much the impact is on full throttle runs and extended aggressive driving but I bet it's significant. I will try and get some logs in similar conditions with the A/C running and with it off.
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Spent about 150 miles on cruise, set at 74mph (around 2400 RPM).
Ambient temperature was a steady 73 degrees.
Watched oil temp on the cluster readout and the following gauges on my JB4: boost, timing, IAT, and water temperature.
Oil temperature was rock solid at 217F the whole time. Pretty sure this is accurate and the monitor is good because I generally watch this all the time when I'm driving and it changes as I'd expect it to.
The car mostly used timing to adjust for load as the hills rolled, keeping boost fairly steady at 1psi. Every now and again boost would drop as low as 0.7 or as high as 1.3 but generally hovered between 1.0 and 1.1 pounds.
Timing would go as low as 12.5 on the steeper inclines and as high as 21 degrees on the downhills.
Water temps varied from 204F to 208F. Getting higher on the way up a hill as expected because the engine is having to work harder and produces more heat. And dropping quite quickly as soon as the hill crested and we headed back down.
The most interesting thing for me is that IAT followed timing and was more or less unaffected by other things, most notably water temps. I expected the radiator to have some impact, but maybe with constant airflow across the front it's minimal; probably a different story at lower speeds and/or in traffic.
IAT on the inclines (12.5 degrees of timing) would generally get down to about 86 but climbed as high as 96 on the declines (21 degrees of timing). I figure it's air flow (cruise control was modulating the throttle, in retrospect I wish I had watched that as well). Just cause there's a consistent 1psi of boost doesn't mean the air moving at the same speed. Maybe it's exhaust temps causing the turbo to heat the air more?
Last trend of note, I turned the A/C off for a little while (had it running most of the trip). It took about 10 minutes, but IAT dropped about 5-6 degrees across the board. Where IAT was bouncing between 86 and 96 as mentioned above, they changed to 80-91 after about ten minutes with the A/C off. I don't know how much the impact is on full throttle runs and extended aggressive driving but I bet it's significant. I will try and get some logs in similar conditions with the A/C running and with it off.
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