temperature delta

[David Anderson]

What should be the temperature delta on our bus radiators from top vs bottom at thermostat full open.

I measured mine on the road the other day.  I have 180 t-stats

1st test, gauge showed 180.  Inlet pipe was 179-suction pipe was 157.    delta = 22 degrees
2nd test, gauge showed 190  Inlet pipe was 189-suction pipe was 179     delta = 10 degrees

Seems like I read somewhere that the delta should be 10 degrees. 

The 1st test I did was driving the bus leisurely and not hard.  I assume the t-stats were not quite fully open giving the water more contact time in the radiator, thus a lower temp.

The 2nd test I pushed hard up a hill and watched the temp climb, climb, climb.  I pulled over and shot the measurements with the temp gun. 

Can anyone verify that the delta at full flow is at best 10 degrees?

David

[Brian Diehl]

That was what I saw when I was out west earlier in July.  (96A3 with 6v92 at 100 degree temperatures)

[Burgermeister]

Brian,

If you think about what you observed, with a comment or two, you'll understand what you were seeing.

The Delta T isn't the significant point, it's the volume of coolant through the radiator ("stats' open wider in 2d test)

and the coolant's ability to extract the heat from the engine and rejected by the radiator.

In first "test" less coolant volume, more opportunity/ability to give off heat (to a point!)

Temp will climb, climb, climb as the heat rejection load increases.  You just don't want to exceed the capacity of the system.

Best measure of that is the overtemp shut down.

Limitation is mainly a result of air trapped in heads of DD 2 Strokes.  Approx 1 quart in each,  unless special measures are taken.

Marc Bourget

[Brian Diehl]

Hey Marc,
How do you get the air out of heads?  Is it worth doing?  Would it make a difference?
-Brian Diehl

[Burgermeister]

Yep,  it's worth it.

I'm be seeking the info from DD tech on Monday, if I can't get it from another source this weekend.

BTW, it's not only removing air from the heads, but what you do with it to insure it isn't pulled right back into the coolant stream.

More later . . !

Marc Bourget