My friend has a "Version 1" STi, ie, a 1994 STi...

Was looking at his engine, when I noticed that the bonnet vents on the sides were blocked off, by what appear to be oem type covers (from underneath)

Can anyone shed anymore light on this?

 

they are meant to blocked off from the factory, only remove if you want a, a ****ed maf b, a ****ed fuse box

 

I don't know why these vents are blocked, perhaps to stop water getting into the engine bay when the vehicle is stationary. Maybe someone knows the answer.

IMHO these vents should be unblocked to ensure good airflow into and out of the engine bay. These vents i'm sure will help to reduce those areas of high pressure in the engine bay either side of the radiator that stop or slow down incoming airflow.

Equally the way the vents are pointed should allow outside air to flow over the top of them creating a vacuum effect on the underside of the vents which in turn allows warm engine bay air to be sucked out through the vents.

Similar in concept to turning your bonnet scoop around. Air coming into the engine bay is allowed to escape via the rotated scoop creating low pressure areas for this to happen. Outside air passing over the scoop again helps to draw warm air out from the engine bay.

Sorry to be so long winded/wordy in the explanation but i can't do shorthand

 

I think that's probably unlikely because the MAF sensor is in effect sealed and pretty much weatherproof, and the fusebox is designed so that you would have to force water underneath it to cause a short. Even the MAF sensor connector is designed to be weatherproof and should stop water from either rain or a pressure washer barring a complete immersion.

I know lots of people that use a pressure/steam washer on their P&J's engine bay to get it nice and clean. I do the same with my car and i've never ever had an issue with either fuse boxes or MAF's or any other electrical connectors or wiring.

 

Ive been led to believe, when the blanking covers are removed it messes up the cooling effect under the bonnet.
Also it does **** up your maf when in a down pour, thats if you have an air cone fitted as it happened to me.

 

Clearly a cone filter would soak up the water and cause issues but those with an airbox would be fine, as would those running a cold air intake (much better!!)

The OP didn't mention if there was a cone filter involved. As for buggering up cooling effect...In which case, why are they there??

 

https://www.scoobynet.com/general-te...net-vents.html


read post 5

 

for homologation purposes..

Removing the covers is bad as it essentially turns that area into a chimney, and what you don't want is hot air trying to exit the engine bay above the filter.

It's not rocket science and the FHI R&D department spent millions making sure that they knew what they were doing....

 

A cone filter is not the only type of filter fitted to either classic or newage scoobs.

As well as the airbox which wouldn't be affected there is such a thing as cold air induction which IMHO is the better option to running a mushroom/cone type filter under the bonnet which frankly is a waste of time unless you have a proper air feed supplying cool air directly to it, otherwise all you'e going to get is warm air being sucked in directly from the engine bay which i guess applies to many of you.

The comments on that thread are interesting but there are equally as many people that haven't had issues with removing those back plates as those that have had problems.

Subaru and the WRC chaps seem to know a thing or two about their cars and have spent many millions on R&D to prove that point, so again IMHO if the rally boys put them there for a good reason, i.e. for cooler underbonnet temps, it is a good bet it may have a similar effect on our road cars. The only way to find out for sure is to check underbonnet temps for yourself with a suitable device while on the move, with vents and without.

If i am completely mistaken i wil go and suck on a lemon!!

 

I have done the test you speak of, with ic temp monitoring.
Inlet charge temp went UP 4degs C in my case and others have seen up to 7degs C
Enjoy your lemon

 

I didn't ask about inlet charge temps, i'm asking about underbonnet temps. Does opening up the vents reduce underbonnet temps?

In your case that's only proof that a cold air induction kit would do a better job of cooling your charge air temps. Presumably a cone filter being directly under the vents is subject to the vacuum affect of the open vents channeling more warm air past the cone filter hence a detrimental affect on charge air temps.

Again another good argument to either leave the airbox alone or fit cold air induction. Or perhaps the mushroom filter looks too good under the bonnet to be bothered about whether or not it's doing a good or bad job.

 

my bad, under bonnet temps not ic.

Either way, you're trying to reinvent the wheel when many have goone before you and explained their results as well.

Where do you propose that the CAI is housed?
in the wing?

 

Nobody is trying to reinvent the wheel, Subaru and their WRC car already did that and got the T-Shirt.

Yep....Inner wing is where CAI kits normally go. If you're going to go on about moisture and dirt entering the inner wheel well don't. Like mushroom filters why's and why not's that one's already been done to death. Let's agree to disagree. What works for one doesn't neccessarily work for another, but not always for technical reasons.

As for bonnet vents.....i'll stick with WRC thinking on that one although ultimately it's down to personal choice. I would run them unblocked you would run them blocked and never the twain shall meet.

 

Anyone got a n/s vent cover for my94 ?

Mine was removed before i brought it.

John

 

Anyone got a n/s vent cover for my94 ?

Mine was removed before i brought it.

John

 

My V4 RA had them unblocked when I bought it, but does run the oem airbox with cold air feed. In fact, judging by the look of them underneath I'm unsure as to whether it ever had them to be honest.

 

Hmmmm higher inlet temps, lower underbonnet temps..... hard choice considering that higher inlet temps do more damage

Its been said already why the vents are there, they are cosmetic on the road car, on the WRC car they make some difference, then again look under the bonnet of a WRC car and most of the bits on the road car aint under there
Of course you could also wonder why subaru didnt put those vents on the new age cars

Tony

 

Would these vents have anything to do with sump guards/under carriage guards on the WRC cars?

Say like the original design is for the air to go down the bell housing way with help from the air coming in through the scoop, if the WRC or Grp N cars have guards, the air needs a different way to escape?

Also, is the position of the turbo different on a WRC GC8?

 

so many sub fans yet no one knows this?

this is how they came from factory ...

unblocked for hot dry countries and blocked for european market due to frequent wet weather

so you can remove them on a dry day. but not when wet, can really feel the difference on a dry winter night . engine is fed very cold air when you floor it, can actually feel the difference

 

Post 8 tells you why
It is not a good idea to remove them on a road going car, higher inlet temps (bad thing) and all the electrics underneath them, now go have a look at a wrc engine, no electrics there and the engine bay layout is completely different.

Tony

 

IIRC Harvey did tests years ago, i think they are only worth it if you run a FMIC ?

I used to remove mine during the hottest summer months, but the majority of my cars life in its recent years, was spent in towns/driving to work etc etc.

 

IIRC the tests harvey did actually proved that the under bonnet temps actually raised with the covers removed

 

That's placebo at it's best....

 

I agree that WRC thinking revolves around WRC cars and engines.....there are many components they have our road cars don't. Completely different animals.....

And in any case- their engines only need to last one weekend! Lol.

 

can't find Harvey's original thread, it was a long-*** time ago...here is an abridged version

https://www.scoobynet.com/showpost.p...4&postcount=15

 

Correct, what happens is the heat gets pulled up over the filter area which raises inlet temps as well as under bonnet.

I remember Harveys test results and removing the vents increased temps.

 

They're not blocked as they have a small water exit hole in them. My car came with them deleted ie so that water could **** through the vents + hot air escape of course ... now put them back on so hopefully avoid any water damage issues albeit engine may now overheat

TX.

 

who put them back on

 

^^ FPMSL! No charge though

TX.

 

Mine were off when I bought the car, I decided to leave them off, the end result was damage to the relay and wiring to the injectors which stopped the injectors from working which led to two meltod pistons and a very expensive rebuild, remove at your peril