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Deletion Of The Throttle Body Heater


Deleting the warm up for the throttle body housing was my last attempt to lower the intake air heat. For some reason I was reluctant for years, to delete this BMW feature. I thought to myself, that there must be some reason for going through all the trouble of designing warm-up features into the throttle housing, as if this was a piston airplane engine that you turn the carb. heat on, mostly when you are coming in for landing to prevent the carburetor to ice up and consequently, you lose all power, with a possible bad or fatal ending. I remember when I was learning to fly that you had much less power, if you forgot to cut off the carb. heat, after touch and go. I read somewhere that BMW introduced this feature due to some possibly related accidents due to a throttle body ice-up under certain weather circumstances and therefore, consequently you might end up with an open full throttle, or more likely a closed throttle with no power and a panic attack.


Another hypothesis I have been rolling around in my head is; that most likely BMW introduced this to make a stable environment for the tuning of the ECU/engine, sins this would hold a steady and stable heat on the intake ambient air and smaller intake air heat variants. This would benefit the environment and lower emission sins the ECU is not coping with large swings in ambient air heat. On the other side, it bothers me that;  the MS41 ECU is a magnificent peace of computer programing and all the parameters are there, to cope with amongst other tings, a different intake heat and ambient heat, so why did the engineers at BMW do this? honestly, I have not found a definite answer to that question yet.     


Maybe it is different for an M52 intake manifold than the M50 sins the intake plenum are much narrower on the M52 and thereby it would create higher air velocity/venturi and colder intake air to the head, this is just a speculation on my behalf but the fact is; that venturi effect drastically reduces the ambient air temperature in a carburetor up to 70° sins it partly relies on ventuti effect, due to restrictions in the neck (that is where the icing occurs in conjunction with the butterfly) of the carburetor, but in our case there are considerably little restrictions in the throttle body itself exempt the butterfly but still, there is a possibility of icing happening if the circumstances are correct.


The initial tests after bypassing the water hoses leading to the throttle body and blocking of the holes show; that the water coolant, that had at times reach almost 99°c /210°f fell down to steady 87,7°c and could reach up to 88,4°c/189,9°f up to 191,1°f (that was mainly due to the oil cooler, has nothing to do with the heater bypass) and the intake temperature in the manifold fell drastically down also, from 43°c./109°f  down to 24°c/76°f (that was mainly due to bypassing the throttle body heat) at standstill and idling with outside temp. at 12°c/54°f, that is a reduction of approximately 61 to 65% from the start, without the oil cooler and air intake mods, when the manifold inside heat was at 62° - 70°c /144° - 158°f, with ambient temperature at 20°c/68°f.


The easiest way to do this bypass is simply; loosen both of the water hoses from the throttle body and also the shorter hose to from the metal pipe. Through away the shorter one and reconnect the remaining longer one, to the metal outlet pipe from the engine, job is done and the water circulates its natural way through the pipes bypassing the throttle body.


This heat reduction, gives me much more elbow room to tune the A/F ratio and timing amongst other parameters within the MS41.


You can read more about my tackle with heat, with "Engine Oil Cooler Final Setup_E39_M52b25"


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My 523i Conversions and Maintenance

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