Postby gslender » Mon Aug 04, 2014 2:06 pm
I've been logging a lot of daily drives and spirit sessions in my ITB setup and found the following.
1) Coolant engine temps rise quickly, but it is not until the radiator temp hits 90 that air temp rises - meaning water temp in the radiator is low until the thermo opens fully.
2) Once under bonnet air temps rise to 40-50 deg they stay about at that temp - meaning that for the most part of a 15 min trip, the air temps remain low, but then rise as if warm air is being introduced.
3) That driving slowly or hard doesn't seem to impact the under bonnet air temps - meaning that regardless of how hard I dare drive, the under bonnet air temps don't go nuts or climb above the ceiling I've seen when driving calmly (less heat/engine temps)
4) That under bonnet air temps oscillate in the same frequency as the coolant temps - ie they go up and down in a similar pattern to the coolant temps. This is the most interesting, as it shows (to me) that as the thermo opens, and puts hot water into the radiator, it then washes the engine bay with warmer air, then when it cools quickly and the thermo shuts, the warm air is reduced. I have nice graphs showing this oscillation that goes on for an entire trip lasting 30 mins of various driving conditions.
Based on 2, 3 and 4, I'm beginning to wonder if the under bonnet air temp is largely a factor of the radiator washing over the ITB cold side (where the sensor is located).
As such, as a cheap solution that wouldn't be too hard to test is building a thin metal shroud/diverter might help keep warm air away, and provide a separate path for cold/fresh air up over the radiator and bonnet.
I might start with a cardboard mock and then move to thin sheet metal to finalise and test.
G
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