2.5L bonnet on zd30, would it help with temp?

hey guys,

the other day i felt the intake pipe going over the motor,
and it was hot as hell, i could leave my hand there for like a second before it hurt to much,
do you think if i had a bonnet scoop blowing cold air on it would reduce the tempreture on it?
and reduce the tempreture on the air going into the motor? cause it wouldn't be surrouned by a hot pipe?

if yes to the above would a bonnet off a new 2.5L navara fit the zd30 navara.
and would the bonnet scoop be actually be over the pipe?
can one of the guys with a 2.5L measure where the scoop is compared to the back of the engine bay?
cause im seriously thinking about swaping bonnets.
what do you guys reckon?

there is a D22 running around here with 2.5 bonnet so they do fit.
effect on intake air temps into the motor would be minor if any at all.
only advantage it would help with air flow through the raditator as air would excape through the bonnet scoop (yes even if its pointing the wrong way!) get a bit bbettetr engine cooling but thats all.

you really need to fit intercooler or possibly water/meth injection.
if you did a body lift you might fit a top mount IC but otherwise it would have to be front mount. i don't really like how low the intake pipes get when doing front mount.

water/meth is something i've been looking at for a while. biggest downside is the need for a large water tank.

tweak'e said:

it would help with air flow through the raditator as air would excape through the bonnet scoop (yes even if its pointing the wrong way!) get a bit bbettetr engine cooling but thats all.

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Tweak'e, I have to disagree with you there, the bonnet air scoop position is optimised for a mix between maximum air flow in and compliance with pedestrian safety requirements. The dynamic pressure on the surface of the bonnet is such that you'd never get air to travel out of the scoop facing forwards, pressure under the car is much, much lower so that's where engine bay air will flow out. Facing the scoop backwards, the low pressure region in the lee of the scoop is so minimal that the scoop will be largely useless.

On your intake pipe Kickars2, like Tweak'e said a bonnet scoop won't help. Consider air-water IC in addition to his suggestions.

Pro-Nav2.7TDi said:

Tweak'e, I have to disagree with you there, the bonnet air scoop position is optimised for a mix between maximum air flow in and compliance with pedestrian safety requirements. The dynamic pressure on the surface of the bonnet is such that you'd never get air to travel out of the scoop facing forwards, pressure under the car is much, much lower so that's where engine bay air will flow out. Facing the scoop backwards, the low pressure region in the lee of the scoop is so minimal that the scoop will be largely useless.

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you normally would think so but its not actually the case. the catch is the air flow under the bonnet. its easier to go out the top than under neath the vehicle.the air flow through the scoop has to fight against the airflow through the rad etc. so at low speeds air is actually going out the bonnet scoop rather than in.
some of the vehicles guys have tested found you had to be doing over 80km/h before the intercooler had ANY air flow going past it. hence why a lot fit fans on the IC (some have it factory fitted)
some found that with some bull bars and especially bonnet protectors they where not getting any air flow through the IC at any speed.

On your intake pipe Kickars2, like Tweak'e said a bonnet scoop won't help. Consider air-water IC in addition to his suggestions.

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air-water are very nice but good ones are horribly expencive.

tweak'e said:

you normally would think so but its not actually the case. the catch is the air flow under the bonnet. its easier to go out the top than under neath the vehicle.the air flow through the scoop has to fight against the airflow through the rad etc. so at low speeds air is actually going out the bonnet scoop rather than in.
some of the vehicles guys have tested found you had to be doing over 80km/h before the intercooler had ANY air flow going past it. hence why a lot fit fans on the IC (some have it factory fitted)
some found that with some bull bars and especially bonnet protectors they where not getting any air flow through the IC at any speed.

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How does it have to fight, you have two flows into the closed system, the intakes at the front and the bonnet scoop, and one big flow out through the bottom of the engine bay.

Flow direction depends largely on the siting of the scoop. Placing it further forward will induce flow out of the engine bay. Further back will induce flow in. Nissan have put the 2.5 scoop right in the middle, so it's largely ineffective as you've suggested. I concur that a fan will always be necessary at speeds below 80km/h.

With a bullbar or bonnet protector, you'd do well to site a vent to exhaust your engine bay at the very front of the bonnet. That would somewhat help your case Kickars2.

Pro-Nav2.7TDi said:

How does it have to fight, you have two flows into the closed system, the intakes at the front and the bonnet scoop, and one big flow out through the bottom of the engine bay.

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actually no, thats not always the case.

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hope the links work. i rough guide.
4x4 speed is a little different but gives you some idea on how things can be so different.

I don't think it would come out of the top either. I think air through the radiator and the bonnet scoop would work together to improve air flow through the engine bay.

Would love to see a vid of the 2.5 D22 in a wind tunnel with smoke injected.

tweak'e said:

actually no, thats not always the case.

4x4 speed is a little different but gives you some idea on how things can be so different.

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As it varies for each vehicle, I think I need to buy a manometer, test my D21, send it to someone with a D22, then someone with a D40, and establish for our vehicles the stock engine bay pressures and pressures at various points on the outside of the vehicle.

with the air pressure stuff i have fitted a bigger bash plate and it runs flat under the car. could this increase the pressure in the engine bay?

tweake when you say better air flow through the radiator how would that work?
cause i want a foward facing bonnet scoop wouldn't air get forced into the engine bay and help it exit at the bottom?

i want to try and reduce engine bay/ and intake temperture's.

cause im driving 30 mins to work on the highway every day and i wonder if it would help cool everything down.

Kickars2 said:

with the air pressure stuff i have fitted a bigger bash plate and it runs flat under the car. could this increase the pressure in the engine bay?

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Yes, think about where the air goes once it passes through the radiator and what restricts it.

Kickars2 said:

better air flow through the radiator how would that work?.

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Greater pressure difference (ie reduce the pressure in the engine bay) or wider opening grill area

Kickars2 said:

cause i want a foward facing bonnet scoop wouldn't air get forced into the engine bay and help it exit at the bottom?.

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Yes but only at higher speeds (+80km/h but varies for all cars)

Kickars2 said:

i want to try and reduce engine bay/ and intake temperture's..

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Intake temps can be brought down to below ambient with various (chemical) intercooling methods. Althougth the engine will still run at the same temp so under bonnet temps will stay pretty constant.

Kickars2 said:

cause im driving 30 mins to work on the highway every day and i wonder if it would help cool everything down.

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This is the best place an keep an engine cool. Idling is when they become the hottest. Thank about when the fan cuts in...

Kickars2 said:

cause im driving 30 mins to work on the highway every day and i wonder if it would help cool everything down.

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tommy222220_0 said:

This is the best place an keep an engine cool. Idling is when they become the hottest. Thank about when the fan cuts in...

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idle is one of the coolest running times for a diesel. unfortunatly lack of airflow (unless fan is running) means its not quite the coolest. hottest is full noise with big load at low speed. (ie going up steep hill).
hot while idling is more of a petrol problem (lack of fuel and air which does a lot of the internal cooling).

scoop may help engine temps a bit at speed but not much. mayby worth while is radiator is stuffed.
when parked it should aid cool down as hot air should rise up though the bonnet rather than being trapped.
over all i don't think it would be worth the $$$. better to spend the $$ on intercooling.

howdy all , just a little curious as to where the temp gage sits on the d22's ? mine sits just under half way ? is that normal? hope I haven't dragged you off topic,')

yep halfway is good.