My car is up for a respray in the next couple weeks. I think I've settled on Jaguar's Stratus Grey Metallic as far as color goes, but I have a spare bonnet I want to have a little fun with, originally I was thinking Louvers, but now I'm thinking NACA ducts might look better as shown on this lister

I've heard of people running into trouble by putting vents so far forward on the, but if I ran them directly to the intakes would I have a problem? Like, a sort of cold air intake that didn't quite connect to them, but almost did, both the intakes and the vents would have 3" pipe, I figure about half an inch apart. I'm also curious as to everyone's opinions on them vs. The Louvers near the rear of the bonnet. Thanks in advance.

 

A couple of threads ago Greg posted under bonnet temperatures and where a vacuume and a high pressure area is and what can be done... I would leave the bonnet as is... Simply because there is no reason to put any additional holes in it...

 

There are two different issues here:
The NACA ducts (which I really like) are (I believe) to encourage air to enter the duct. getting these connected somehow to the air intake would greatly benefit intake air temperature reduction by as much as 30 or more degrees C.


The addition of louvres would reduce under hood temperatures, particularly at low speeds, and also post switch-off. However I believe louvres would not do much, if anything for intake temperatures. But I am going to test for this before to long, I hope.


As for the connection between the NACA ducts and the intakes, you will, I think, need a positive join, or at least overlapping tubes. That should be doable though, as long as you do not mind cutting and shutting the inlet trumpets to somehow fit inside and overlap with the NACA ducts output tubes, or the other way round. The main thing is getting enough tolerance so any engine movement (of which there is quite a bit) does not rip out your lovely ducts from the bonnet!
Greg

 

The concept of connecting the NACA ducts to the intake is intriguing.


Other critters use a box-like air dam. Fixed up front in a front corner.
The hood/ bonnet forms the "lid' when closed. A bit foam seals it.


Engine movement can be accommodated with flexible tubes from the box to the intakes.


Room enough? Possibly not?


Carl

 

If the NACA ducts extended into a longish shallow box under the
sheetmetal, that box could mate with a similar shaped plenum
under and the mating surfaces could have suitable foam seals
installed. No idea if you have clearance to do this.

One of the most effective ways of venting engine heat to the
outside is through fender extractors. Something akin to the
fake fender louvers on the Portfolio editions of later models,
except that they are functional.

 

What are these fender extractors you speak of

 

look at the front fender just behind the wheel well of a third gen firebird transam

 

Polished alloy portfolio vents installed on my x350... They could have been functional (the wing moulding allowed for air flow) but the alloy vents don't..!

 

You can get preformed NACA ducts fairly cheap now in the aftermarket.
If you have any welding skills, you could cut out a rectangle from the top of the 'removable' half of the airbox (dirty side), weld on some plates to raise this opening to just below the bonnet where the NACA enters, & then put some thick (2 - 3cm or so) rubber edging all around the edge of this new opening, so it effectively seals against the underside of the bonnet when the bonnet is closed.
An old XJS boot seal might even work & be the correct profile.

I think they look cool & would certainly consider fitting a pair.

 

Fender-style air extractors are possible on the XJS, but,they would require a great deal of planning, cutting, and fabrication, because, of the footwells, and, inner fender structure, as well as the hardware housed in the enclosed areas behind the wheelwells.

My donor car has the front fenders removed, so, I could post a photo of this area, if anyone is interested.

 

I love the look of the NACA ducts, and while they could definitely help increase cold airflow to the intakes, theres only one problem: RAIN. If for whatever reason you find yourself driving in the rain, those ducts (if well sealed to the intakes) will turn your car into a v12 shop vac. All that water spray from the vehicle in front of you will be going straight into your airbox, and eventually your engine....

 

Apart from the NACA ducts that Lister bonnet has an exhaust vent at the aft end.