Turbo fitted, engine bay heat removal - I need VENTS!!!!
Discussion
Advice needed for my MX5 Mk3(NC) but this question could apply to any force induced petrol engine hence posted here!
HEAT! Lots of heat, not over heating but under the bonnet everything is warm, even the washer fluid. It could be ok or, in my view, the heat could reduce the longevity of various items found under the bonnet, maybe.
I have searched for options and have found that the general consensus is that bonnet vents are a good option to remove heat, (not air scoops, I have air in, I need air exit) I have also found a pressure differential bonnet map to show where on the bonnet the ideal place to put a vent, or pair.
This is where I need a little help. I have found a set of vents from racing beats for the MX5 but the cost is £245 delivered so they are expensive, large and look a little ‘non’ OE (riveted and BIG)
Have any of you chaps had a good experience with a generic set of vents, easy install and look good, as in no rivet's but which give a good flow of exit air, or am I hoping for too much?
I'm thinking Ford RS, Impreza etc
Thank you !
HEAT! Lots of heat, not over heating but under the bonnet everything is warm, even the washer fluid. It could be ok or, in my view, the heat could reduce the longevity of various items found under the bonnet, maybe.
I have searched for options and have found that the general consensus is that bonnet vents are a good option to remove heat, (not air scoops, I have air in, I need air exit) I have also found a pressure differential bonnet map to show where on the bonnet the ideal place to put a vent, or pair.
This is where I need a little help. I have found a set of vents from racing beats for the MX5 but the cost is £245 delivered so they are expensive, large and look a little ‘non’ OE (riveted and BIG)
Have any of you chaps had a good experience with a generic set of vents, easy install and look good, as in no rivet's but which give a good flow of exit air, or am I hoping for too much?
I'm thinking Ford RS, Impreza etc
Thank you !
Edited by knitware on Friday 17th June 14:33
vtecyo said:
Any vent will do the job. Hot air rises, so if there's a hole in the bonnet it'll get out.
Bonnet raisers are a bit marmite, but could do the job.
No, it really won't.Bonnet raisers are a bit marmite, but could do the job.
Heat might rise but the airflow over a bonnet is like so (MX5!):
That area of red will stop any heat from leaving. You need to have the vents in areas of low total pressure so the heat is sucked out.
Other options are:
- Fit Air Dam under front bumper to force air from behind radiator out bottom of the car
- Fit NACA duct undershield to push air up the rear section of the engine
GroundEffect said:
No, it really won't.
Heat might rise but the airflow over a bonnet is like so (MX5!):
That area of red will stop any heat from leaving. You need to have the vents in areas of low total pressure so the heat is sucked out.
Other options are:
So the best way is to have the vents inside of the cabin then?Heat might rise but the airflow over a bonnet is like so (MX5!):
That area of red will stop any heat from leaving. You need to have the vents in areas of low total pressure so the heat is sucked out.
Other options are:
- Fit Air Dam under front bumper to force air from behind radiator out bottom of the car
- Fit NACA duct undershield to push air up the rear section of the engine
Artey said:
GroundEffect said:
No, it really won't.
Heat might rise but the airflow over a bonnet is like so (MX5!):
That area of red will stop any heat from leaving. You need to have the vents in areas of low total pressure so the heat is sucked out.
Other options are:
So the best way is to have the vents inside of the cabin then?Heat might rise but the airflow over a bonnet is like so (MX5!):
That area of red will stop any heat from leaving. You need to have the vents in areas of low total pressure so the heat is sucked out.
Other options are:
- Fit Air Dam under front bumper to force air from behind radiator out bottom of the car
- Fit NACA duct undershield to push air up the rear section of the engine
knitware said:
Advice needed for my MX5 Mk3(NC) but this question could apply to any force induced petrol engine hence posted here!
HEAT! Lots of heat, not over heating but under the bonnet everything is warm, even the washer fluid.
How warm is warm? Measure the difference in temperature between the engine bay and ambient air when the car is moving and get back to us.HEAT! Lots of heat, not over heating but under the bonnet everything is warm, even the washer fluid.
Edited by knitware on Friday 17th June 14:33
When I had a supercharger in my Mk1, the engine bay was only 5-10'C hotter than ambient when moving. I removed the front grill when adding force induction. As long as the air comes in, it will find a way out.
I've now got a 240bhp rotary in there which has the efficiency of a steam engine and the engine bay never seems unusually hot.
GroundEffect said:
Artey said:
GroundEffect said:
No, it really won't.
Heat might rise but the airflow over a bonnet is like so (MX5!):
That area of red will stop any heat from leaving. You need to have the vents in areas of low total pressure so the heat is sucked out.
Other options are:
So the best way is to have the vents inside of the cabin then?Heat might rise but the airflow over a bonnet is like so (MX5!):
That area of red will stop any heat from leaving. You need to have the vents in areas of low total pressure so the heat is sucked out.
Other options are:
- Fit Air Dam under front bumper to force air from behind radiator out bottom of the car
- Fit NACA duct undershield to push air up the rear section of the engine
GroundEffect said:
No, it really won't.
Heat might rise but the airflow over a bonnet is like so (MX5!):
That area of red will stop any heat from leaving. You need to have the vents in areas of low total pressure so the heat is sucked out.
Other options are:
Don't understand that. Surely the red areas show the areas of fastest air movement, which will result in the lowest air pressure?Heat might rise but the airflow over a bonnet is like so (MX5!):
That area of red will stop any heat from leaving. You need to have the vents in areas of low total pressure so the heat is sucked out.
Other options are:
- Fit Air Dam under front bumper to force air from behind radiator out bottom of the car
- Fit NACA duct undershield to push air up the rear section of the engine
knitware said:
HEAT! Lots of heat, not over heating but under the bonnet everything is warm, even the washer fluid. It could be ok or, in my view, the heat could reduce the longevity of various items found under the bonnet, maybe.
Trust me, things under the bonnet of your car are fit to withstand much higher temps that you'll ever get in the temporate UK!For example, i've done cooling system and thermal signoffs on vehicles in Death Valley at 50degC and under the direct, cloudless sun of midday! On one occasion the clutch fluid of a Viper SRT-10 boiled and meant i had to drive out of the valley without a clutch.......
boyse7en said:
Don't understand that. Surely the red areas show the areas of fastest air movement, which will result in the lowest air pressure?
That'd be right. There is a zone of high-pressure air that forms at the base of the windscreen, which is why cars often have cabin air intakes there... and why bonnet risers don't work for getting air out of the back of the bonnet. There might be some side-suck going on though.How about this?
Apparently it only took a steady hand and something to cut the bonnet with - and maybe some tiny supports to stop them flapping.
Edited by wst on Friday 17th June 21:00
Op, you'll have a high pressure region across the windshield base but not the outside corners. If you're able to remove any of the sealing strip, outside air will enter the engine bay and flow downwards under the car sucking heat along with it. This worked well on my TR8 turbo.
You may have to consider the air intake for heater matrix though.
You may have to consider the air intake for heater matrix though.
boyse7en said:
GroundEffect said:
No, it really won't.
Heat might rise but the airflow over a bonnet is like so (MX5!):
That area of red will stop any heat from leaving. You need to have the vents in areas of low total pressure so the heat is sucked out.
Other options are:
Don't understand that. Surely the red areas show the areas of fastest air movement, which will result in the lowest air pressure?Heat might rise but the airflow over a bonnet is like so (MX5!):
That area of red will stop any heat from leaving. You need to have the vents in areas of low total pressure so the heat is sucked out.
Other options are:
- Fit Air Dam under front bumper to force air from behind radiator out bottom of the car
- Fit NACA duct undershield to push air up the rear section of the engine
There's always a pressure build-up at the base of the windscreen, and it's very low flow, which is why it's a nice, regulated area to have the cabin air intake. It's also why bonnet risers do absolutely sweet sod all, except ruin the look.
Much better to have mid-bonnet vents, and with the MX5 (with its sealed undertray) you need exit vents.
NACA look great, but aren't really suitable in exit form. I'd have a look at other manufacturer vents of FR cars and see how they've done it, they'll have spent the beans.
ETA: wst beat me to it!
These look rather nice from the X100 XKR, looks good on a curvy shape.
Edited by Krikkit on Friday 17th June 21:07
Boosted LS1 said:
Op, you'll have a high pressure region across the windshield base but not the outside corners. If you're able to remove any of the sealing strip, outside air will enter the engine bay and flow downwards under the car sucking heat along with it. This worked well on my TR8 turbo.
This sounds interesting, any images to help me see? Also, the sound insulator under the bonnet, is it worth removing that?knitware said:
Krikkit said:
These look rather nice from the X100 XKR, looks good on a curvy shape.
They do look good and should help. What does this mean - "NACA look great, but aren't really suitable in exit form" Are/is NACA a type of vent?Edited by Krikkit on Friday 17th June 21:07
Thanks!
knitware said:
They do look good and should help. What does this mean - "NACA look great, but aren't really suitable in exit form" Are/is NACA a type of vent?
Thanks!
NACA ducts are diverging ducts - they slow air down and increase the pressure to force air through the hole at the back (wide end) and they work best (maximum pressure differential) by having high-speed airflow going over them in the "diverging" direction.Thanks!
The air going into your car through a NACA duct is going at pretty high speed. Going the other way, trying to extract air - there is no movement of internal-air over the duct (even if you flipped it to have the duct on the inside, so the diverging shape would do something at all to the internal air) so they would work about as effectively as plain holes cut into the sheet metal would.
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