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I know Velox has some airflow diagrams, but mainly showing the rear of the car for their diffuser.

Is there any airflow diagrams for this platform showing the front/leading edges of the car? Would like to take a look at the low pressure zones on the hood...for science.
 

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7/18 Ambient temp 100*F
Hood starting temp 138.5*F
Ending temp 130.2*F
This run no liner or rear seal.

Liner back on tomorrow, will repeat test. Shot the hood all over and recorded max temp.


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7/19
Ambient temp 98*F
Hood starting temp 137.3*F
Ending temp 114.9*F

This run with liner in no rear seal, same drive almost identical conditions.

Yes, the liner keeps engine heat from making it to the hood, that's very clear. The hood was able to get close to ambient temp much faster.

But in both cases, the hood started off just sitting in the sun hotter than it ended up. So this nonsense about discoloring your hood is FUD.

Will retest tomorrow with rear seal replaced.


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7/19
Ambient temp 98*F
Hood starting temp 137.3*F
Ending temp 114.9*F

This run with liner in no rear seal, same drive almost identical conditions.

Yes, the liner keeps engine heat from making it to the hood, that's very clear. The hood was able to get close to ambient temp much faster.

But in both cases, the hood started off just sitting in the sun hotter than it ended up. So this nonsense about discoloring your hood is FUD.

Will retest tomorrow with rear seal replaced.


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Thanks for doing these tests! This is probably the most useful information so far. I wonder what the temps would be 20-30 minutes after the engine is shut off? If that doesn't exceed the hood starting temp, I think that would really put this hood discoloration question to rest.


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Thanks for doing these tests! This is probably the most useful information so far. I wonder what the temps would be 20-30 minutes after the engine is shut off? If that doesn't exceed the hood starting temp, I think that would really put this hood discoloration question to rest.


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I'll test that tomorrow in round 3 just for kicks. Obviously can't go back in time for these first two..


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Thanks for doing these tests! This is probably the most useful information so far. I wonder what the temps would be 20-30 minutes after the engine is shut off? If that doesn't exceed the hood starting temp, I think that would really put this hood discoloration question to rest.


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It's been almost exactly an hour and the engine is still very warm (was putting rear seal back on). Shot the hood and saw max of 116.0*F. Not much of an increase due to soak. I wish I would have done this on round one, I may retest just to put it to bed.


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7/20
Ambient temp 98*F
Hood starting temp 148.4*F
Ending temp 118.5*F

This run with liner and rear seal back on.

Delta in starting temp due to trip after lunch. Car sat in identical parking spot all 3 days (full sun).

Conclusions:
The liner does keep heat from the engine bay off the hood, but in every case the hood starts off hotter in the sun than it does after a run parked in the garage.

The fact that the hood was hotter without the liner is not necessarily a bad thing. The heat the liner kept off the hood was probably retained in the engine bay. I don't have an AP to get accurate cooling temps.

If you want to pull the liner and are willing to deal with the vacuum noise (some actually prefer it) you can do so and not worry about ruining your hood. The damn thing gets hot just parked in the sun.

Also, pulling the rear seal didn't appear to have any impact at least on hood temp. I'll probably leave it on anyways just to keep water out.

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7/20
Ambient temp 98*F
Hood starting temp 148.4*F
Ending temp 118.5*F

This run with liner and rear seal back on.

Delta in starting temp due to trip after lunch. Car sat in identical parking spot all 3 days (full sun).

Conclusions:
The liner does keep heat from the engine bay off the hood, but in every case the hood starts off hotter in the sun than it does after a run parked in the garage.

The fact that the hood was hotter without the liner is not necessarily a bad thing. The heat the liner kept off the hood was probably retained in the engine bay. I don't have an AP to get accurate cooling temps.

If you want to pull the liner and are willing to deal with the vacuum noise (some actually prefer it) you can do so and not worry about ruining your hood. The damn thing gets hot just parked in the sun.

Also, pulling the rear seal didn't appear to have any impact at least on hood temp. I'll probably leave it on anyways just to keep water out.

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Thanks for compiling this data. I know it's a small sample size and stuff, but just seeing that direct sunlight is as bad (or worse) for heat transfer to the hood than driving without the liner makes me feel better about removing it. Planning to yank it off when I get home, hoping I can find a space in the storage shed to keep it and the engine cover "just in case".

Plus, with the liner gone, I can start figuring out my plan of attack for the hood vents!
 

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7/20
Ambient temp 98*F
Hood starting temp 148.4*F
Ending temp 118.5*F

This run with liner and rear seal back on.

Delta in starting temp due to trip after lunch. Car sat in identical parking spot all 3 days (full sun).

Conclusions:
The liner does keep heat from the engine bay off the hood, but in every case the hood starts off hotter in the sun than it does after a run parked in the garage.

The fact that the hood was hotter without the liner is not necessarily a bad thing. The heat the liner kept off the hood was probably retained in the engine bay. I don't have an AP to get accurate cooling temps.

If you want to pull the liner and are willing to deal with the vacuum noise (some actually prefer it) you can do so and not worry about ruining your hood. The damn thing gets hot just parked in the sun.

Also, pulling the rear seal didn't appear to have any impact at least on hood temp. I'll probably leave it on anyways just to keep water out.

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Thanks again for doing all these tests! Its settled for me, I enjoy that vacuum noise so I'm gonna go ahead and pull my liner


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I pulled mine as well to get a bit more engine noise along with the engine cover. I also pulled the rear hatch cover and cut into the foam under the rear carpet for the spare tire I put in. This also brings in a bit more exhaust noise for anyone looking to hear the car better with the windows up.
 

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Pulled the liner this weekend (already have had the cover off) and while there is definitely more induction noise, it's not nearly as "intake-y" as I thought it would be. More just like air rushing past a window, not throaty or performance-sounding.

What I DID get a lot of was that coke-bottle noise. Sweet tap-dancing Christ, that is so loud now! I have so far been skating by without a SSC, but I feel like I need one now if I plan to keep the liner off, since that's all that I can hear now. No wonder mountune suggests to remove the liner, it's to sell more SSC's!

DI injector noise is a bit more noticeable too, but nothing too annoying compared to the BRZ.

Still on the fence about what to do. Really want to get underhood temps down, but I feel like I'll need hood vents to make that happen. And that requires the liner to stay out, which means I'll need the SSC (and maybe the recirc valve, too?)... Maybe I'll just shove it all back in and run WMI lol
 

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I wanna put vents in, but 2 things are holding me back. I don't trust myself to do it, and don't trust just anyone else ether. And second.... I've yet to see a good solution for dealing with water. I don't want the engine bay looking like the car is 36 years old and constantly have to clean it from all the water, dirt and debris that get spattered in there. I would obviously put rear facing on it so at SPEED a lot of that crap would deflect off, but not when the car is stationary. I think all these cashgrab companies flipping out a quick vent for the "RS" would sell a lot more of them if they would sell a way to deal with the water.

So at this point it's not worth the hassle or cleaning the ensuing mess, or the steep learning curve of installation with high cost of making a mistake just for a few degrees temp drop and a atheisticly appealing look.
 

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For what little it's worth. I just put vents on my hood last week. Mostly for aesthetics, but I did take temp readings after a 2 hour drive.


Maxton Design Hood Vents by Aaron Frost, on Flickr


Maxton Design Hood Vents by Aaron Frost, on Flickr


Temperature Readings by Aaron Frost, on Flickr

And regarding water in the engine bay. It rained pretty hard last week while the car was sitting, and while I drove it. Very little actually got in. I have a closed airbox, so I'm not particularly concerned about it.
 

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Have just brought an under bonnet kit from these guys https://www.nkgroup.co.uk/product/car-underbonnet-kit/ they make a kit for Focus's

Had to remove my liner as I went for the Mountune option but still wanted some protection.

Product Description from there website.

Underbonnet Car Soundproofing covers the following areas:
Bonnet Lid (NoiseKiller Vibrasorb)
All engine bay parts use our waterproof Noise Killer Vibrasorb material. This is self adhesive with a damping sheet to reduce bonnet vibrations and an open cell Class “0” acoustic foam to absorb engine noise. The foil facing gives a wipe clean maintenance surface which also protects the bonnet lid against heat discolouring.
 

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Raising this thread from the dead lol

I took my hood liner off yesterday and it does make the intake louder. It's more audible when the window is down. The symposer drowns out the intake noise when I'm driving it with the windows up though.

Still not loud enough for me so I'm gonna try to install an AEM dryflow filter. If I'm not happy with it then I'll put the mountune high flow pipe on it.

Anyone else do similar mods?
 

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AEM dryflow and no liner was unbearable vacuum noise for me YMMV


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Oh so you've tried that already? Maybe I'll put the liner back on with the dryflow. Would that still be audible in the car with windows up?

I had a short ram intake on my previous car I didn't like it really... It was too loud.

Do you have experience in the mountune high flow induction kit? Maybe I'll keep the stock filter but upgrade only the pipes to hear it a little better lol
 

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I have stock air box and piping just the AEM dryflow. You can hear it with the liner on but not obnoxious. Liner off it was ridiculous. Would be worse with full intake


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I have stock air box and piping just the AEM dryflow. You can hear it with the liner on but not obnoxious. Liner off it was ridiculous. Would be worse with full intake


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Awesome. I think I'll go the same route. Thanks for doing all the test I'm sure lots of people will appreciate it!
 
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