I am sticking with the heat vent idea and we are not talking about other cars here just XKs.

@ Xeno The big difference you are noticing is between front bumper types, the reason the older XKs lift is becasue of the bumper design, you have a big high pressure area building up at the front lifting the car, with the later 05 cars the extra bit on the front with the enclosed undertray forces the air around and under the car, this creates low pressure. As the air rushes over your hood this is also a low pressure area until it hits your windshield which then creates a slightly higher pressure, which is why RAM air intakes were designed in this area, all this together gives you more down force.

Having bonnet vents would do very little but create turbulance, there is too much in the way, if you had big open areas under the hood I would say yes having hood vents would be benefitial, as above them is low pressure allowing the air to escape, also would take a fair amount of heat with it

 

The louvers can also direct heat towards the windshield and help keep it clear when one is driving in winter weather.

 

The only vents I can think of off the top of my head that were designed to provide down force are on the Ferrari F50. They were designed to work in concert with the front fascia and a set of fans inside the vents that sort of suck the car down.



I agree with the others who said the XKR vents are simply to extract heat.

 

I'd been meaning to ask this for months - you just reminded me!.

My car is is in excellent 'under hood' condition, and I'd like to keep it that way. What do you use on the valve covers? I tried silicone (as you'd use on interior plastic) and that didn't look good, so stopped after the first 'squirt'

-Steve

 

What I have found that works OK on cam covers and easily available is Back to Black, particularly if they are sun bleached, doesn't last forever but easy to do.

 

I took the car to the body shop this morning and we discussed the positioning of the louvers, cutting out the holes, the effects of doing these things on the hood, paint, etc...Then the shop manager goes outside for a few minutes and comes back in carrying a salvage XKR hood in both hands! (He's a big guy, lol) "I thought I had one of these..." he says. So we discuss the pro's and cons of using either hood (I favor the XKR hood, so did most of the shop), so he says he'll prepare estimates for both by this afternoon.

 

Replace the hood is the way to go

 

The vents have three functions:

1. allow the engine to cool a little more easily
2. allow excess air pressure in the engine bay at high speed to escape. They do not provide downforce, just reduce lift.
3. look cool (TBH, this is probably what they're really there for )

 

Definatly. Then the only question is what to do with the origional hood. I see one in very good condition just sold on ebay.

One of the guys in the shop suggested painting the louvers the charcol color of the trim and overriders. Might look cool.

 

I definitely would take flush over proud.

 

Sell your old hood, it will go against the cost,


I have seen different colour louvres on XKs before, it's a marmite moment, you either like it or hate it, but it will look effective on a Silver car

 

The shop manager called with the estimates, and they were both higher than I had hoped, so I'm questioning this whole idea and will put off this decision until after I get the drive shaft replaced early next week. That needs to get done asap, and I doubt the hood could get done by the end of this week.

At least I got the exhaust tips on today. Quite pleased with those.

 

Trade for a XKR and keep it real.

 

I like the normally aspirated types but I also like the XKR "added trim" features.

 

Could be worth a try. If I didn't like the color, just pop them out and repaint!

Are the screens you make for the louvers removable for cleaning, as in slide in and out or drop down?

 

Yes, but...


I actually read some factory literature that directly stated this was why they were installed. I tried searching to find it, but after about an hour I gave up.

All I'm saying is that is what official literature I read somewhere stated.

Believe it... or not!

 

I believe you, because I read it somewhere, too. Isn't it in the Thorley book on the XK8?

 

The only hood louver reference I could find in Thorley's book (page 55) mentions engine cooling, nothing about reducing lift.

 

The louvered panels are referred to in Nigel Thorley book, to aid airflow and keep under hood area cool. Strategically positioned for the best low pressure airflow. A small discrete spoiler also aided airflow, compensating the aerodynamics aspects being tested in a wind tunnel. So I would say both reasons are why they installed the louvers and don't forget about the spoiler which most people think is non functional. In other words your all right and they look cool.

 

I hate to paraphrase, but what I basically read was that "...the XK8 had really solid aerodynamics and the XKR only needed a few really minor tweaks for handling one being the louvers and the other being the spoiler," and it went on to mention that only the tiny spoiler was needed and not something huge or more flashy...

And it wasn't from some internet forum, it was in some official literature, interview from the design team or something of that sort. Information I actually digested as opposed to disregarding due to conjecture...

It really doesn't matter to me. What does is that the XKR does handle much better than an XK8, mostly due to having larger and wider wheels and a tighter suspension.