Reading the forums here has a lot of good ideas for a real cold air intake while still keeping the stock look.
Here is my attempt.
I looked all over for a thinwall tube and not much luck. I took an empty spray paint can and cut off both ends and perfect 2.5 inch dia tube.
I then connected it between a 2.5 inch dia hole I cut in the bottom of the air box to a 2.5 dia hole I cut in the plastic trim strip directly behind the rh headlight. This opening has connections to the radiator opening grill area and fender well so should be no shortage of air.
I slid the tube from inside the airbox into the hole in the trim panel and then glued in place with silicone sealant and let dry.
I will paint black and probably wrap tube and area in heat shield reflective foam to complete the installation.
I included pics with during construction as the colors make it easy to see what was added and how. I will pop in a K& N airfilter and see if I can detect any difference.
Even if it only SOUNDS better..........
(I did remove the air horns/baffles on the intake also as I noticed the later models deleted them.

 

By the way, it is a 2000 XKR with 48k miles. Runs strong. I just think it is a tiny bit too civilized, and just want a bit better breathing and to hear a bit more of the supercharger whine.

 

What problem is it that you are trying to solve with this?

 

Being on this site for many years, I have seen that most folks will tell you this will give you little gain in the power dept. These cars as folks have said are so tuned to the T from the factory that you can't do much to them beyond the factory set unlike other cars out there.

 

Yours is the 4.0 xkr. On my 4.2 xkr, there is a second opening in the airbox that open at full throttle. ---it's still hardly any intake sound!

 

I was also going to ask about that missing second opening with the servo actuated door. I didn't realize that it must have been a new feature for our 4.2 SC engines.

 

Sorry to wake a sleeping thread...
I also have a 4.0 XKR. I am interested in the second door in the filter box that the 4.2 guys have. Could one of you 4.2 owners post some pics of said second airbox intake?

 

That second door is opened with an electrical actuator. I believe it gets its signal from either the ECU or the fuel pressure regulator. I don't think you can just put our air box on an SC 4.0 or NA 4.2 and get it to work. At the least, I've never heard of it being done

 

makes you wonder if that thing works or not.. you know? How would you test it? I agree I miss the intake sound - I had a cone filter on my miata and you could really hear the hiss and growl from under the hood.. I might me scared to try that on a Jaguar though with all the error codes and computer.

 

Solenoid-activated. If it doesn't open you'd be way down on power (lack of air means can't create power).

Easy ways to check:
1. very thin line of something easy to break (whisker of glue?) and see if it does break (not my way - see below)
2. OBD and see if you get nice big MAF readings
3. dyno

#2 suits me, though I reckon you'd easily tell it was way down on power.

 

I know I've seen cold air kits (actually "hot" air kits) for our cars. Any one of those would get you the sound you're after. Although the SC engine does sound enticing when WOT, it would be hard for me to believe that the little second hole in the airbox makes that much extra noise.

 

It's the SC itself I reckon, spinning so fast. (And it doesn't care how it gets the air.)

 

Yeh - Our sound is definitely more mechanical / gear-whirring-ish. It's not the roar of a Ferrari V12 with open Webers, or the screaming Jet Engine whine I had with an X-1/9 at 8,000 RPM.

 

I think there is definately some gain to be had by improving the airflow into the box. At 6000 rpm even a normally aspirated XK8 would be pulling 450-500 CFM. (I think...)
Pulling what I know about airflow, static pressure losses would be significant.
Static pressure is developed from the friction of the tube (or duct) wall. Small eddies (vortices) form at the boundary layer as the air trips and stubles due to friction, shape etc. When two walls are close together (as in an oval) the eddies coming off the opposing surfaces can interact to create further reduction to flow that increases the closer they are. If two ducts have the same area and one is oval, the oval duct will at best only flow 80% of the volume of air at a given static pressure. Similar concept when you look at two round 3 inch ducts and a single round 4-1/4 inch duct. The 2 three inch ducts combined have the same area as the 4-1/4 but since the walls of the 4 are further away from each other the flow is less turbulent. The single 4-1/4 inch will flow considerably more air.


On a 4.0 XKR, I measured the area of the snorkel to the airbox at 6.3 square inches. The small end of the MAF was 6.1. I didnt measure but believe our throttle bodies (TB) are 75MM which = 6.8 Sq. inches.
It might appear that the TB flows significantly more than the rest of the system. However I believe its flow to be greatly limited. Since it is sandwiched between two hard 90 degree turns the TB flow potential is probably close to the MAF's straight line flow.
The door on the airbox that the 4.2 owners have is telling. At first glance the 6.3 sq inches of the snorkel may look adequate. However, since it is oval, at the same static pressure it likely flows like a round duct of 5 square inchs in area. Hence the door on the 4.2's.
I plan to make a small fiberglass snorkel similar in shape to the existing one but with a minimum of 10 square inches of area (targeted size).
I dont like the accordion portion of the duct either. Considering the friction losses, if I can keep the transitions smooth I believe that moving up to 3.5 inch diameter might be good even with the 2.8 inch diameter MAF. Why? friction loss. The MAF flow is relatively straight...not a lot of flow loss. A 90 degree bend will not flow like a straight tube. Since there two 90's and a 30 degree turn, bumping the diameter should make up for the turn losses.

 

Great technical discussion, Knowsnot! (says, the aero engineer - lol).


One last thing to consider though. The flow improvements will only manifest themselves at WOT or close to it. How often are you at WOT? If the answer is "DAILY!", then knock yourself out and enjoy. However, if the answer is, "I can't remember the last time I was WOT", the effort will be for naught.


Power improvement pursuits always spawn that question for me.

 

Hello Scardini1, I admit it..People have questioned my effort to reward ratio before !!
When I was thinking about this I gravitated to the CFM of a normally aspirated engine. It was easier to calculate.. For an XK8 I think that the mod may be overkill from a performance standpoint. Aesthetically?
For an XKR, when you consider the parasitic loss of a blower (especially with a pulley mod) then it might be of benefit at lower throttle positions then one might think.

 

Adding to the technical discussion by knowsnot:

An engine, any engine, needs approximately 2.2 CFM per HP. Also a straight, smooth, round pipe will flow 115 CFM.

With the 4.0 XKR peak of 370 HP you need to flow 2.2 * 370 = 814 CFM. A normally apirated 4.0 XK8 needs only 2.2 * 290 = 638 CFM.

To flow the 814 CFM for a 4.0 XKR if all pipes were round, smooth and straight you would need 814 / 115 = ~7.1 sq in. To this add additional area to account for bends, accordians, etc. If your measurements are correct that means that the snorkel, MAF and throttlebody may be restricting the upper end.

For a normally aspirated 4.0 XK8 you need only 638 / 115 = ~5.55 sq. in. It appears that everything was sized for a normally aspirated XK8 properly but maybe not the R's. Dunno.

And, of course, everything needs to be a bit bigger again for the 4.2 engines.

 

True - the blower really only creates a "delta pressure". So the easier it is to get air to it, the more boost it can provide. Theoretically, I guess, that could take place throughout the power band.


I wouldn't fret the "effort to reward ratio" thing too much; especially with ME. On the '68 Triumph Retro-Mod I built (drivable, but still not quite finished) people will ask me why I did this, or why I did that. And sometimes the answers are no more complicated than, "Because I wanted to", "Because I could", or "Because I like the way it looks".


I'd rather keep Kitty stock, but if others want to treat their XKs as I did my Triumph, .... Well BRAVO and GOOD LUCK!!!

 

WAFlowers, I agree..designed it for the xk8 and aside from the resonators on the intake tube they left it alone on the XKR. On the Airflow vs horsepower on an XKR, the airflow will be even higher due to the significant parasidic drag of the blower. Definately an undersized intake in that instance. One of the threads talks about boring out the TB to 80MM (7.25 inches?) that and 3.5 inch tube would help but MAF is still tight



scardini1, I agree on the keeping it stock. I like the look of stock and all parts will be kept safe for later use. My intake design/plan involves a factory look (flat black) and use of the factory airbox..Although the snorkel mod might have me making a new box anyway..Function and design outweigh flash and bling for me.


Only other change would be removing the overaxle segment of the exhaust and using the Adamesh over-axle piece.
Slight improvement on air going in and slight improvement on air coming out..
Improve on what exists vs upper/lower pulleys etc.


Like the triple Stromberg setup !!