M35 Bonnet Lift - Heat Extraction

[DMM]

Good idea!

What is actually happening is air is being forced in

The M35s have the zero lift aero design which actually generates some reasonable vacuum under the car. Right at the base of the windscreen is a high pressure buffer area, which would force cleaner air into the engine bay. These two working in combination would be helping to draw some fresher air into the engine bay!

Good work!!

[Ben C34]

Maybe. Or the air being forced in the back makes it harder for air to go through the radiator.

Edited November 2, 2014 by Ben C34

[DMM]

Maybe. Or the air being forced the back in makes it harder for air to go through the radiator.

Fortunately not, the combined frontal positive pressure and combined undertray negative pressure is combined greater than the high pressure at the base of the windscreen. It will only stunt radiator flow a little bit, nothing worth worry about.

[Ben C34]

Fortunately not, the combined frontal positive pressure and combined undertray negative pressure is combined greater than the high pressure at the base of the windscreen. It will only stunt radiator flow a little bit, nothing worth worry about.

Maybe.

My only issue is that you are guessing.

[DMM]

Maybe.

My only issue is that you are guessing.

I've got a mechanical engineering degree and currently (slowly) studying for my masters.

[Ben C34]

I've got a mechanical engineering degree and currently (slowly) studying for my masters.

Ok.

Still guessing though.

[DMM]

Ok.

Still guessing though.

What brings you to this conclusion? If you have any CFD data on the stageas that would be awesome! Im not a wind tunnel expert but am well versed in fluid dynamics.

[Ben C34]

I don't need data to call you out for guessing though do I?

Here's a question for you .

How much cooling affect does an engine get from air generally blowing over it vs the actual radiator?

I don't know. But I would have a guess and say the air though the radiator is way more important.

[DMM]

I think maybe you misinterpreted my first post. Not trying to be argumentative here either.

I like his idea, I personally think it would work well as its removing heat from a critical area of the engine bay that sees very large amounts of heat saturation. This would have small benefits to hoses and component life in that area, as well as manifold heat soak would be brought down a little.

The reason it would work well in my opinion as its effects would only become valutive at higher road speeds when a reasonable pressure system can build at the windscreen base. At the time these speeds are achieved the radiator system at the front of the car is already achieving the maximum transfer of heat from air speeds. The only way the radiator system could become more efficient at this point is if the ambient air temperature was to become lower.

[Dan_J]

Thanks Dale. That is a pretty good temp compared to mine. I don't have a nismo thermostat as yet. I have got a 53mm aluminium radiator, except when i installed it i didnt trim enough of the shroud off so when driving it for the first time after the install, when i came off boost the engine lurched forward and plowed the clutch fan into the shroud and thus destroyed both...so i installed twin thermos in a sealed shroud i made up. So until i can get my hands on a decently priced shroud and clutch fan i have to live with the davies craig setup.

On another note: i put the undertray back on today for the first time since i bought the car. Water temp is between 90-93, so 1 deg higher on the lower running temp;same on the higher end. Intake temps were lower!!! I think this is due to more air being channeled into the cold air intake (ducting next to the I/C).

pics of shroud and how the thermos are mounted ?

there is a wrong way of mounting thermos which will block air flow

[Equilibrise]

Thanks for the input guys.

I have had the bonnet like this for a little while now and although it is drawing air in at the lifted point I am not experiencing any temperature rise in any driving situation. I am in fact experiencing a temperature loss and improved drivability. I am not recommending anyone else to or not to do this, I am merely posting my experiences, and as dale said earlier, it is just another version of whats been done before.

I am yet to get my hands on the appropriate equipment to monitor the pressures, but when i do i will post up the data.

To add to DMMs discusion points, before i lifted the bonnet i could not keep my hand on intake manifold at all. Now, after a spirited drive i can keep my hand on it as long as i want - still feels warm, but not nearly as scolding as before. So i'm guessing that the heat from the exhaust manifold that wraps around the back of the motor is being extracted rather than heating up the intake.

I'll take a pic of the shroud in the daylight, but i am still convinced that the clutch fan is a better option.