Re: Dyno Testing Q's

[Jason Renville <Jason_Renville@ccm.al.intel.com>]

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>Well here's what I know.  During my downhill travels I freewheel and
>use my brakes (CV's are shot and I reversed them so make ugly noises
>downshifting, so I don't).  When I do that the engine oil temp drops
>about 30 degrees.  As I sit in traffic and idle the oil temp rises.
>According to the above logic, if I sit in traffic and rev the engine
>my oil temp should drop!  I'm not willing to try it.  So my theory
>still applies, revving my engine up while on a dyno would overheat my
>engine as insufficient air is being scooped into the engine
>compartment.  Vehicle speed = better cooling. That's why later busses
>had outdented intakes, ie scoops.


   I have on many occasions dropped my VW into neutral at a drive through and 
revved it to cool it down.  It is not a 30 degree drop but a drop none the less.


  If you have no, or minimal holes leaking in the engine compartment then 
revving while stopped will cause the fan to pull in more air.  This incoming air
will be cooler than the air surrounding the engine because it is coming from 
outside the vehicle.  It will also be a higher volume of air than when sitting 
at idle.



  More air volume+ increased air velocity = more heat leaving cooling fins = 

cooler VEEDUB.  

Freewheeling down hill helps cool two ways.  Little combustion heat due to low 
rev's + more air forced past cooing hardware.

Revving the VW increases the combustion heat generated but also increase the 
cooling air to compensate.  The increase in cooling is more than the increase in
temp due to combustion.  

        This is exactly the reason you don't lug around in top gear on a hot 
day.(unless you want your motor to last only a short time).

     
                                Jason Renville
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I would rather attempt something great and 
Fail than attempt nothing and succeed.

Jason_Renville@ccm.al.intel.com
Portland, OR USA
69 Fastback second owner.
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