standard air box clearances, how much cold air really gets to it.

[Davezj]

These pictures are for illustrastion purposes only.
I am not trying to say block off the air with plastercine and channel only cold air to the snorkle.
what i am trying to show is how little the clearance is in the under bonnet area in front of the air box, which is the only area that allows cold air straingt to the box.

what did was put plastercine all round the airbox area and shut the bonnet. this made the shape you see here and the flat top of the plastercine shows where it touched the underside of the bonnet.

my snorkle is a bit cut up with the side flages removed and the top cut back also (not my doing).

see pics below

[Wodjno]

It's less than that Dave

As tou are not showing the Bonnet Stay blocking the gap also ..

And cut the centre tab out of the front grill in this pic

http://www.clubvr4.com/forum/attachm...2&d=1271177970

I have

And remove the bonnet stay

Cheers

Wodj

[Davezj]

i am not for one minute suggestion all the air that gets to the snorkel is cold air and it come directly from the little grill bit just above the VR4 badge. just how tight it is under there.

if you look at the height of the side bits just on the down slope of the snorkel you can see there is quite a bit of room in that area, so one would assume that the air entering the snorkel would take the path of least resistance, and would come in from the sides in the form of hot air from the engine bay.

and yes glen the bonnet stay is removed as i have gas struts holding the bonnet up. i have not got to the modification bit yet. i could put the bonnet stay back on to show the full blockage. i will do that tomorrow. and don't get me started on the big anti vibration bit of foam that is on the stay, that sits right in front of the snorkel as well.

[Davezj]

the cold air from the front of the car would also come in from the bonnet catch area, which i have blocked off just to show clearance height.

My real point i suppose, and there is a point, and i am going to get to it, eventually. Is............

there will be a lot of hot air going to the snorkel from under the bonnet, what would be the suggested fixes for this.

glens is noted and is a good one, i would also shave off the right hand side and just leave the mounting point i would also enlarge the grill bars in the bit above the VR4 badge so it went all the way across the right hand side of the grill.
this would be complimented with a larger area of blocking off and channeling of the cold air, with some thick foam tape instead of the plastercine. all the way from the left hand side of the bonnet catch opening in the grill top to roughly where the plastercine is on the right hand side so it was more like a funnel.

[Wodjno]

The Struts u got where u get them from and what pressure are they.. And is u got a Carbon bonnet or still the Mekkle 1 ?

Cheers

Wodj

PS.. I went 0.2 secs quicker on the 1/4 mile with the Bonnet stay removed

[AlanDITD]

consistently?

[Wodjno]

consistently?

Well i was consistently 0.2 secs slower upto the point i removed it /hmmm

[elnevio]

LOL!

The hot air problem is only a problem when stationary. Once you are moving through the air, the air in the engine bay is being replaced rather quickly by cold air from the front anyway.

[Turbo_Steve]

That's cos the bonnet stay is so heavy, Wodj....try taking the spoiler off!

If you really really want a nice, high pressure flow of air into the airbox, the best thing you could do is cut a hole in the bonnet in front of the snorkel.

However - I'm not sure where you've got the idea that hot air is getting in there - if the car is moving forward then there is a high pressure zone at the front of the bonnet which will be forcing air through any gap around the bonnet it can into the engine bay. The only time it'll be breathing warm air is when it's stationary, so I don't really see that as much of an issue.

Also, bear in mind that with a typical flow rate of well over 300cfm at full throttle, in one minute you've pretty much emptied the entire underbonnet space of warm air and are drawing in cold from wherever you can get it. As the car is now moving (after 1 minute at full throttle...fairly quickly! ) then theres about 2 billion million squillion square feet a minute of cold air being forced through the front grille, radiators, bonnet gaps, round the headlights etc etc

It's an extreme example, but once you're off a dyno, hot-air-induction is only a problem for about 3 seconds when you pull away from being sat idling for several minutes.

I do reckon you're onto something with the air-path, though - it's hardly ideal!

And the plasticine idea is just pure-fricken-genius: one of those "Why didn't I think of that?" moments. Rep your way for that one!

I guess I need to buy an FRP bonnet and cut a hole in it. I just can't find one I like

(edited to add) Damn you Nev!

[stuey]

I often thought the frontal area of intake and route into the snorkel was a bit small...

When you mean the bonnet catch, d'ya mean the whole metal mechanism on the left ?
I've thought before cutting away the upper section of the centre grille in front of the intake would let nice cold air in.. nobody tried this ?

[Wodjno]

I didn't think hot air was getting in!
My thoughts were on amount of airflow...

[Davezj]

I often thought the frontal area of intake and route into the snorkel was a bit small...

When you mean the bonnet catch, d'ya mean the whole metal mechanism on the left ?
I've thought before cutting away the upper section of the centre grille in front of the intake would let nice cold air in.. nobody tried this ?

yes bonnet catch the bit in the middle. i have added some more pics to an earlier post

[elnevio]

I didn't think hot air was getting in!
My thoughts were on amount of airflow...

[Wodjno]

I've thought before cutting away the upper section of the centre grille in front of the intake would let nice cold air in.. nobody tried this ?

I already did

[Davezj]

Well i was consistently 0.2 secs slower upto the point i removed it /hmmm

they were the one carlos got hold of in the group buy for about £40, but i did not pay that much as mine were second hand when i bought them and it is a metal bonnet.

[stuey]

Meant more air in general, cold would be a bonus..!

[Davezj]

i am not convinced about the hot only being a problem wen stationary, the front of the bonnet to the slam panel is quite well sealed when the bonnet is closed.
i think there is a good chance the air from the radiator which will be hot, will after leaving the back of the radiator will hit the front of the engine and either be push up or down depending on how high it is up the radiator it hits.
When the hot air gets pushed up i think it will hit the bonnet and roll forwards and backwards.
the hot air that rolls forwards will go into a sort of hoizontal vortex and roll straight in the snorkel as this is now sucking for england. This is why i think the inlet of the snorkel needs to be isolated from the rest of the engine bay.

If there was massive, massive amounts of air going in to the engine bay then i am sure after a spirited run out the strut brace and right hand intercooler pipe would not be too hot to touch after pulling over and immediately opening the bonnet. which mine always are, plus other metal bits around the engine bay.

this is just a theory but it is a theory. this theory does however fall down when you look at the intake air temps with evo scan. i don't seem to remember them being particularly high, but are they measured before or after the intercooler? is it measured in the MAF as part of the MASS Air Flow measurement.

[Turbo_Steve]

I didn't think hot air was getting in!

Sorry, didn't mean to infer you did, Wodj, it was general musings in Dave's direction


And yes, it WILL be breathing in hot air when stationary. But my point is that the SECOND you're NOT stationary, it's getting cold air, the intercooler is getting cooled and the inlet tract is getting cooled. It'll be picking up just as much heat through radiation as it will breathing in at a standstill.

And, of course, the harder you're accelerating, the faster you're going, and the faster you're going the more cold air you've got, and the higher the airspeed is, which means the faster it cools! (think in terms of sticking your hand out of the window at 30mpg and how cold it gets)

I'm not saying it's ideal - far from it, but in terms of performance limiting design issues with our engines heat ingress is extremely low down on the list. Getting that rear turbo to run cooler is a much bigger deal

[Davezj]

don't you want the turbos to run as hot as possible for the exhaust side anyway. but keep that heat away from the compressor side as much as possible.

really there should be a verticla heat sheild that runs down the center of the tubro to do this. to isolate exhaust from compressor. transferwell it would help with localised air heat transfer but obviously not the direct heat transfer through the catridge area of the turbo.



I do get you point about the lots of cold air thing steve and the evo scan logs of inlet air temp is undeniably a true picture of the facts.
bang goes my theory. but that is what a theory it for to pose a posibility or a point and then prove or disprove it. and in the imotal words of yes you guest it, and i don't need to tell you who................

BUSTED!

[bradc]

Lol Steve, I think you mean at 30mph which is a speed all VR-4's are capable of. It seems only some VR-4's are capable of 30mpg

I have been thinking for some time that running the airbox as it is with a panel filter inside and then a large pipe leading into the airbox that sucks air up from the foglight area might just be the best bet for those not wanting to cut a hole in their bonnet!