D22 Bonnet Aerodynamics

Hi Guys,

A while ago I read a thread where people were suggesting that the Aerodynamics of the D22 bonnet and scoop arrangement were poor resulting in bugger all airflow into the scoop more so with the bull bar and critically if there was a bonnet protector between the bullbar and bonnet.

A bit bored today so went and bought some wool and masking tape and set up an experiment to check the airflow over the bonnet around the scoop. I then took photos of the tufts of wool at varying speeds from 40 to 100km/hr.

The same pattern showed each time suggesting the airflow to the opening of the boonet scoop receives clean laminar flow of ambient air.





Told you I was bored :-(

Cheers,

DJ

wheres the pics

i would be surprised to see it gets flow with a bonnet protector.

Hi Deejay did you have any dramas re fitting snorkel - presume you have 2 batteries as std. Some say...yes you can fit.......others say no you cant and Nissan dont seem to know re the latest D22 with 2 batteries.

If you fit the Nissan snorkel (Airtec) and a Pirhana tray you will have no problems. Any aftermarket snorkel will not allow the battery to fit.

You were bored, cool experiment none the less.

My D22 is running a front mount, was the easiest option at the time. Works well and sounds like a truck which I like.

Dave.

Dave said:

You were bored, cool experiment none the less.

My D22 is running a front mount, was the easiest option at the time. Works well and sounds like a truck which I like.

Dave.

Click to expand...

how is the front mount making it sound like a truck?

I would be surprised if the turbulent zone downstream of the bonnet protector was big enough to detect with wool tufts. What that doesn't tell you is the pressure differential between the front of the scoop and the engine bay, the lack of which means inadequate flow across the intercooler. Buy a manometre and continue the experiment!

Firefly said:

Hi Deejay did you have any dramas re fitting snorkel - presume you have 2 batteries as std. Some say...yes you can fit.......others say no you cant and Nissan dont seem to know re the latest D22 with 2 batteries.

Click to expand...

Hi Firefly,

I had no trouble fitting the snorkel to the D22, it didn't create any problems with the battery at all. Apart from having to remove the battery to install the snorkel, it was all a piece of piss actually. Just a little time consuming.

Cheers,

DJ

maddogrc said:

how is the front mount making it sound like a truck?

Click to expand...

Induction sound is a little deeper, let off the accelerator and when the waste gate opens its louder.

Dave.

tweak'e said:

wheres the pics

i would be surprised to see it gets flow with a bonnet protector.

Click to expand...

WHY NOT !!!!!!! bullbar,, bonnet protector,, or kangaroo carcass stuck in front,, air is going to enter the scoop... i assume you travel at 300kph or over, then maybe the air flow would be redirected ..... NEXT TIME IT IS RAINING,, go for a drive and watch the beads of water travel up your bonnet, guess what they travel from front to back and guess what the faster your car goes the faster the air flows

Very very cool little experiment, I like it!

fourfoot64 said:

WHY NOT !!!!!!! bullbar,, bonnet protector,, or kangaroo carcass stuck in front,, air is going to enter the scoop... i assume you travel at 300kph or over, then maybe the air flow would be redirected ..... NEXT TIME IT IS RAINING,, go for a drive and watch the beads of water travel up your bonnet, guess what they travel from front to back and guess what the faster your car goes the faster the air flows

Click to expand...

bonnet protectors are designed to lift up and swirl the air so dirt etc doesn't land on your bonnet. on some vehicles the change in aerodynamics means the intercooler doesn't get proper airflow. one of the patrol versions is a well known and proven case of this. by memory there is no factory bonnet protector for it due to that.
a few toyotas also have the issue that im aware of and most likely other vehicles to.

simple logic here.... if bonnet protectors didn't change the airflow then they wouldn't keep the dirt off, it means it doesn't do its job, therefore no one would buy one. people would just buy the stone chip strips instead.

I always thought they were to stop small stones and pebbles chipping the paint on the bonnet curve, that is their primary role isn't it? I could be wrong, but someone will tell me,

raywise said:

I always thought they were to stop small stones and pebbles chipping the paint on the bonnet curve, that is their primary role isn't it? I could be wrong, but someone will tell me,

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thats what the plastic/rubber stick on strips are for.
get clear ones for the front of the bonnet and even thick clear ones to stink onto headlights.
with bonnet protectors the plastic sticks up right at the end to force air up.
similar to the little wings you can get for the rear of vans and station wagons. curves the air over to stop dust settling on the rear window.
ditto with trucks, have curve bit on the front corners to direct air flow past the doors to keep it clean.

tweak'e said:

bonnet protectors are designed to lift up and swirl the air so dirt etc doesn't land on your bonnet. on some vehicles the change in aerodynamics means the intercooler doesn't get proper airflow. one of the patrol versions is a well known and proven case of this. by memory there is no factory bonnet protector for it due to that.
a few toyotas also have the issue that im aware of and most likely other vehicles to.

simple logic here.... if bonnet protectors didn't change the airflow then they wouldn't keep the dirt off, it means it doesn't do its job, therefore no one would buy one. people would just buy the stone chip strips instead.

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mate you are getting mixed up with BUG DEFLECTORS on trucks they do push the air in different directions but that pissy little aerodynamic plastic bonnet protector is there to stop the stones from chipping the rolled edge of bonnet very unlikely it is going to affect airflow to scoop

This is what is being discussed? Nissan | Perfect Fit

These are what I know as stone deflectors, bonnet protectors etc.

fourfoot64 said:

mate you are getting mixed up with BUG DEFLECTORS on trucks they do push the air in different directions but that pissy little aerodynamic plastic bonnet protector is there to stop the stones from chipping the rolled edge of bonnet very unlikely it is going to affect airflow to scoop

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hes not confused mate...

those thin strips at the front of bonnets have enough curve on them to alter the window/air flow, and thats their design.

yes they also help with rock chips, but they also do deflect the air.

you dont need HUGE angle to cause a change in air flow, look at most modern cars, they're sleek and have soft curves to allow for best air flow, not like the trucks with the big bug deflectors, lol

a bug deflector on a car like the trucks use would probably make fuel economy worse by a bit as they stand up nearly vertical!

i've read all your posts you've made so far, all you seem to do is bag people out and make it so only your opinion is right

fourfoot64 said:

WHY NOT !!!!!!! bullbar,, bonnet protector,, or kangaroo carcass stuck in front,, air is going to enter the scoop... i assume you travel at 300kph or over, then maybe the air flow would be redirected ..... NEXT TIME IT IS RAINING,, go for a drive and watch the beads of water travel up your bonnet, guess what they travel from front to back and guess what the faster your car goes the faster the air flows

Click to expand...

oh yeah, not that i have a bonnet scoop, but.......

my landcruiser utes bonnet is mainly flat, and has a slight incline going up from the front of the car to the windscreen.

when it rains i have puddles of water just sitting there and not blowing towards the windscreen, even though its flat at which air should be BLOWING on it and pushing it up towards me.

you know why it doesnt? because the top of my bullbar sits just above the top of the front of the bonnet and DEFLECTS the wind so it doesnt go onto the bonnet.

yes on my windscreen water blows up and away at speed, but not on the bonnet.

i'll get a video if i have to...

maddogrc said:

hes not confused mate...

those thin strips at the front of bonnets have enough curve on them to alter the window/air flow, and thats their design.

yes they also help with rock chips, but they also do deflect the air.

you dont need HUGE angle to cause a change in air flow, look at most modern cars, they're sleek and have soft curves to allow for best air flow, not like the trucks with the big bug deflectors, lol

a bug deflector on a car like the trucks use would probably make fuel economy worse by a bit as they stand up nearly vertical!

i've read all your posts you've made so far, all you seem to do is bag people out and make it so only your opinion is right

Click to expand...

agree with that. i'm surprised he hasn't been given a holiday yet. hopefully it won't be long. for a supposed 54 year old he isn't very mature... in saying that, it is still school holidays isn't it..?

maddogrc said:

oh yeah, not that i have a bonnet scoop, but.......

my landcruiser utes bonnet is mainly flat, and has a slight incline going up from the front of the car to the windscreen.

when it rains i have puddles of water just sitting there and not blowing towards the windscreen, even though its flat at which air should be BLOWING on it and pushing it up towards me.

you know why it doesnt? because the top of my bullbar sits just above the top of the front of the bonnet and DEFLECTS the wind so it doesnt go onto the bonnet.

yes on my windscreen water blows up and away at speed, but not on the bonnet.

i'll get a video if i have to...

Click to expand...

i get the same on my mk patrol, but the bullbar doesn't go over the bonnet, it's mainly because the front end is shaped like a brick wall, lol. at least the front end of the navara bonnets are curved a bit to increase airflow