Ram effect works when off boost. Ram effect also increases supercharger efficiency. The main advantage of Jaguars chosen location for air intake is intake temperatures which significantly affect power for supercharged engines. Indeed, bmep is limited by intake charge temperatures and the lower temperature you begin with the lower the intake charge temperature will be when the spark occurs. You have achieved the opposite effect.

I see you concede that your holes do not usefully affect CSA.

 

Any car develops a high pressure area at the grille when moving forwards. This effect begins as soon as you move forwards. The highest pressure will be just above the spoiler lip where much of the cooling air for the radiator actually flows into the engine compartment.

The engine air intakes are sited at the top of this area on road cars to minimize the risk of water ingress from wet roads, specifically puddles, or the intake snorkels would be much lower.

Some cars are equipped with hood scoops to exploit this effect, or Naca ducts which use airflow itself to increase airflow.

Whatever the positive effect may be (and you are just guessing, btw) you have eliminated it in search of more noise. .?????

 

So uh.... About that engine cover.

It sounds like removing the engine cover doesn't seem to have any discernible ill effect, and I really like the slight increase in growl and whine. I've had it that way for a few days and apparently the worst effect it has is on my gas mileage, since I keep wanting to hear it. I think I'll work on the resonator delete soon too. Thanks everybody for the input!

 

Oh ya- that!

 

Perhaps you could leave the cover on and drill some holes in the airbox?

 

Jagular, i'll ask again, whats your background in engineering???

And with regards to drilling holes into the airbox, i really do NOT understand how you don't get that this increases the intake size to the airfilter.........i give up on that one, i guess you need more stars on ones badge to grasp this......

and with regards to the location of the air intake on road cars being high (a huge generalisation) i guess the famed Jag engineers got it wrong on the 2010 XKR i had...........they were at the bottom of the bumper in front of the wheel arches, no ram effect there and guess what!!! They make the same power as an XFR and the intake on these is as large as the filter itself.......so detrimental.......i think not. I achieved my goal of more charger whine.

over and out, i rest my case.

 

I don't understand why nobody has thought to shoot holes through the airbox. If it sucks hot air, we can shoot through the hood too! As an American, I've found that all things can be solved with enough bullets.

/sarcasmandlightheartedhumorpleasedonttakeseriously

 

I think I saw a post elsewhere where they were talking about ducting from the wheel wells for a CAI. Considering the vents are already there, I suppose it would probably work - you'd just have to take into account the dirt and mud (and snow in my case) being slung around there.

 

I have a CAI on my HUMMER and it is ducted from the wheel well...But in this case the wheel well has an inner liner on and all the road dirt/water and dust the tires sling is mostly deflected from being ingested and if memory serves me right, the XF does too......But the point is to not suck in hot engine compartment air with a CAI.

 

You may be confused because I am not saying what you seem to think I am saying.

Removing the bottom of the airbox entirely would not increase the intake size to the air filter because the maximum pressure the air filter can benefit from is atmospheric pressure, disregarding ram effects which you suggest are minimal anyway. As long as the size of the intake to the airbox is at least the same size as the exit to the airbox cutting more holes in the upstream or intake side of the airbox can have no effect on airflow through the filter.

The effective CSA of the air filter itself is many times the area of the intake and exit ports.

Siting the air intake snorkel in front of a front wheel exploits the highest pressure area at the front of the car while reducing the risk of unwanted water ingress, as I previously suggested it might by pointing out that the maximum air pressure at the front of the car will be found just above the lip spoiler. There most definitely is a ram effect from siting air intakes directly in front of the front wheels and my SAAB Aero exploits this also, and it is a very high pressure turbo engine. The challenge is to exploit this effect while not restricting cooling flow to the radiator and front brakes.

On the V8 and V6 supercharged XF the twin air intakes are located above the top of the radiator and draw ambient temperature air from the top of the area feeding cool air to the radiator. There will be a ram effect from the resistance to airflow presented by the radiator matrix. It is a very clever design because the sealing around the radiator will also enhance airflow into the engine. Drilling holes in the bottom of the air filter boxes will reduce power by reducing this effect (possibly drawing air from a slight negative pressure area in fact) and drawing heated air from behind the radiator. Not a clever idea.

Not only that but it is obvious that the effective CSA of the intake side of the air filter boxes is already somewhat larger than the CSA of the exit ducts.

These are very simple concepts even an engineer can follow without much training.

 

If the liner is vented at the front, as it is on an Audi S4 for example, there's another source of higher pressure for ram effects: the rotating front wheel jams air into the leading half of the fender.

 

Those vents in the front of the wheel well, are for air to travel over the Brakes...I don't know what school of physics you went to, but you better get your money back if you paid for it...The tire rotates from top to front and that DOES NOT jam air up into the wheel well at the front( I better add, that this is when driving forward, but then again, you may drive in reverse all the time and that would explain your contrary point of view again)., but simple aerodynamics says it won't happen.

 

I understand perfectly what is being said its just that its incorrect, i can only guess its from ill informed google searches.........(other search engines are available! )

DPK is bang on with his statement and the area you mention in front of the wheel will actually be in vacum when the wheel is rotating......if there air filter like you seem to think draws air up stream of this point it would be trying to draw in air against the air flow..........holes in wheel arch liners here i would say are most likely to aid brake cooling.

Again as i previously mentioned the additional itake holes i have are not on the engine side.........in fact the factory intake is!!! Have you ever felt how hot these pipes get!!! They are situated above the wheel arch where there exists nice cool air......the air that goes through the bumper vents.

i have a fellow forum member on a UK site that works for a tuning company and is currently designing a custom intake tract with a choice of either standard air boxes or open mushroom intakes. He will be doing several dyno runs with an XFR to look at the effects of his design.........i'll see if he can drill some holes in his standard airbox.......i'll go with the Jagular recomended 46mm to see the effects..........watch this space...........well a new thread anyway.....

 

You'll have to tell all those race engineers what you've discovered. They'll be so pleased.

Please explain those simple aerodynamics. Pretend I'm in grade 6, that'll be easy for you.

Tip, how do you throw a curve ball? Or, if you're not a baseball fan, what makes a golf ball slice or hook?

 

I'm thunderstruck.

 

I thought there was high pressure inside the wheel wells? Which is why the sports car teams run vents on top of the wheel arches now? Or are we talking about something different? Is there a vacuum in front of the wheel and the high pressure area is at the top?

"... Louvers are used over the fenders of sportscars to relive high pressure that builds up from the fast spinning tire, and from the complex interaction of air flowing in, out, and through the wheel arch.

The general rule is the more air you can extract from the wheel well, the better. On street courses, prototype teams will usually sport the biggest, longest, and most aggressive forms of louvers to vent air and create downforce. Another aspect of most louvers is their taller height (to give air a ‘chimney’ to flow out from) – that extra height adds more volume to the outer profile of the car—making a bigger hole for the passing air to go over and thus reducing straightline speed. ..."

 

Need to pretend youre in grade 1!!! These physics laws do npt apply in the same way as to a wheel which generally has a friggin great big bumper blocking the air path........come on even you with you 5 stars on your chest ( Just assuming what you do as youre reluctant to say!!) Must get this.

 

I'm just glad automakers didn't put baseballs or golfballs on instead of tires...

 

There maybe some truth to your theory, but mainly the upper vents are for equalizing lift by allowing air to travel from underneath to the top at high speeds to prevent the front end from lifting...otherwise the car's shape acts like a wing with negative pressure on top.

 

Ha ha ha........could make an interesting styling accesorie!!!

Boiler.......agree with youre points and the pic of the car.....what a car!!! My understanding is that vents on top of the wheel arch will serve two primary purposes.....one relieving high pressure at the TOP of the arch and also aiding cooling for the brakes with the air being sucked out of those vents as the car moves forward...........secondary function is they look frikkin cool!!

The area in front of the arch will be being sucked out by the forward motion of the car.......i believe someone believes this is a good place for an intake......well it is not, even in grade 6 or flipping bugers with 5 stars on your chest you'll get this.....there again i'm damn sure some really fecking irratating google keyboard warrior will come back with a response.......cos they sure a hell aint down the pub having a laugh with their friends!!!