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Discussion Starter #1
During dyno-testing heat-soaking is a problem. Has evaporative water-cooling been tested on the M5? Results?

I think spraying a fine water-mist from a garden hoose onto the engine, radiator and MAFs might help lower the temperatures. Haven´t tried it yet.

Thoughts and input would be appreciated.

David
 

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Question is WHY would you do that? - to get a bigger number... for the sake of a bigger number...

what benefit would that provide you in tuning a car?

The large fan running simulates tha car moving at a high rate of speed... leaving the hood open also takes a little heat out of the car... so not 100% a re-creation of a car traveling at speed... but close
 

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Its a natural phenomenon that air temperature within a confined space is higher than outside's fresh air!!!
 

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Discussion Starter #4 (Edited)
Thanks for the input so far!

The purpose would be to get conditions as close as possible to on-the-road, and to get better reproducibility. As it is now, each dyno run is different. First the numbers get higher as the oil heats up, then the numbers get lower as the engine gets heat-soaked. Keeping the engine at a constant temperature would make tuning a lot easier, I think.

David
 

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last time i checked my fire dept was using water to put fires out.
 

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And a car tht has been running on the road for high rates of speed (or idling for that matter) does NOT suffer from this?
 

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Discussion Starter #7
marinakorp said:
And a car tht has been running on the road for high rates of speed (or idling for that matter) does NOT suffer from this?
When the car stands still parked, after the engine has been run hard, the intake air temperature (as measured by the MAF temperature probe) goes up to 120 deg C. When you drive off it takes about 30 s to get the temperature sensor to measure the actual air temperature, and not the heat conducted from the mounting hardware. (This is why people buy the IAT relocation kits, which move the point of measurement outside the hot zone of engine compartment.)

When the car is driven fast, there is a lot of air flowing out from the engine compartment under the car. This airstream cools the engine air intake system very effectively. The engine compartment does not get heat-soaked until the car stops.

With the car stationary on the dyno machine there is no such airstream even with a very big fan applied.

I speculate that it is easier to recreate road-like temperature conditions by spraying water than to build a huge wind-tunnel. I am also certain that reproducibility is key to successful tuning.

David
 

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Maybe one of the members here has a meat packing plant.And maybe another member has a dyno company.Why not put them together and have a dyno in a nice cold commercial fridge?:D
 

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David, I am not as technically oriented as yourself our other members of our forum, but from a laymens perspective I feel your idea has merit, and if I had a dyno or a research lab I would go ahead and try it out, with that in mind I dont know whats available too yourself or what you have going on, but I encourage you to test your theory and see where it leads, it definitaly sounds worth examining, Josh
 

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marinakorp said:
The large fan running simulates tha car moving at a high rate of speed... leaving the hood open also takes a little heat out of the car... so not 100% a re-creation of a car traveling at speed... but close
Actually, it is not close at all. The pressure drop between the stagnation point at the front of the car and the underside behind the front axle centerline is very large at speed creating substantial radiator airflow. Trying to recreate the airflow across the radiator on the dyno that even comes close to that achieved at 60mph on-road is impossible with the typical dyno fans. There is no way to simulate the low pressure condition on the back side of the radiator in the shop, and trying to create a higher pressure front side condition is very difficult due to spillage. This is the reason Dinan went to such extremes with their fan setup. The goal is to create a pressure drop across the radiator similar to on-road conditions.

To the question at hand, I think a fine misting of the radiator surface would go a long way to keeping temps in line. The M5 DME system will quickly pull spark advance and enrichen the mixture the second temps start to rise too far (about 1/2 way through the first pull ;) ). Anything to keep radiator temperatures in line will go a long way to help dyno consistency imo.
 

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CSBM5 said:
Actually, it is not close at all. The pressure drop between the stagnation point at the front of the car and the underside behind the front axle centerline is very large at speed creating substantial radiator airflow. Trying to recreate the airflow across the radiator on the dyno that even comes close to that achieved at 60mph on-road is impossible with the typical dyno fans. There is no way to simulate the low pressure condition on the back side of the radiator in the shop, and trying to create a higher pressure front side condition is very difficult due to spillage. This is the reason Dinan went to such extremes with their fan setup. The goal is to create a pressure drop across the radiator similar to on-road conditions.

To the question at hand, I think a fine misting of the radiator surface would go a long way to keeping temps in line. The M5 DME system will quickly pull spark advance and enrichen the mixture the second temps start to rise too far (about 1/2 way through the first pull ;) ). Anything to keep radiator temperatures in line will go a long way to help dyno consistency imo.
yes - BUT how is spraying a fine mist from a garden hose on to the engine going to allow for consistency in measurements... as was the question posted
 

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The goal is to hold the radiator temperature (coolant temp) below the threshold where timing gets pulled and the mixture is richened up a bunch. Spraying the fins with a mist of water can potentially greatly increase the convection coefficient through evaporation and/or conduction heat transfer from the fins into the water (which has the highest specific heat of just about any liquid). As long as the radiator coolant temp can be held in check, that is all that matters.
 
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