Underbonnet/intake air temperatures [Archive] - SaabCentral Forums

: Underbonnet/intake air temperatures

14th October 2004, 08:14 AM
Firstly, I need to apologise to Adrian W.........

Secondly, I eventually got some thermocouples sorted out to be able to measure intake air temperature (post-intercooler) and underbonnet temperature (adjacent to top intake pipe)

I had expected to see intake temperature much higher than underbonnet temperature, especially in chilly N. England.

Measuring on a day when the ambient was +12degC I found, once warmed up the underbonnet temps ranged from about 70degC
(v.low speed) to just below 40degC. This lowest temp of 38degC was when I was travelling at a steady 65mph, almost off the throttle.

At the same ambient, the intake air temperatures ranged from about 15degC upwards. Driving in traffic with limited space to use the power, I was getting to only 20-25degC. On finding space and giving it full throttle through 1,2,3rd gears, I only got to 35degC. The intake temp dropped almost instantly on getting off the throttle. Only on giving it full throttle through 1,2,3,4th (test track only :cheesy: ) did I get intake temperature up to 48degC, the only time it was above the COOLEST temp under the bonnet.

I have to concur, insulating the intake pipe probably is a benefit. As to why Saab don't bother, I will dig out my old chemical engineering textbooks and calculate (estimate) the heat transferred in this 'single tube heat exchanger'

I suspect it may prove to be not a very siginficant amount, but every little counts!

Does anyone have an idea of the VE of a B235R, to estimate the flowrate and velocity of the air in the intake pipe?

Chris 9-5
14th October 2004, 05:58 PM
Cant answer your question but thanks for the info, really interesting stuff :wink: