A little while back l made up an aluminium undertray for my XKR.
No apparent change in vehicle operation or problems to date. I made no provision for access to sump plug or filter but it takes all of 5 minutes to remove or replace.
The transmission tray is fixed independent to the engine tray.
No apparent advantage in driving either, other than a cleaner look under car.
​​Any thoughts?

 

Did you pay attention to any MPG changes? Have you tried driving in high speeds?

I like it and think it’s a good idea.

 

I'm sure pedestrians will appreciate the vehicle can now glide smoothly over them although use of countersunk fixing bolts would prevent abrasions.

Neat job and a great improvement on plastic undertrays.

Graham

 

Very professional look -- well done....

 

Have not had a long enough drive for useful consumption figures as yet. Any high speed driving can only be an occasional happening these days, one really needs to be very careful of where and when to indulge.

 

I like it!
Toyed with the same idea.
Cleaning up air flow should make some changes in high(er) speed driving.
WJ

 

I like it. I think you need to incorporate a NACA duct to assist with the Alternator cooling (you may have shielded the air flow). I managed a curved one but it looks amateur. Yours would look great because its on a flat interface..

 

I’ll take one, with the duct for the alternator please.


Z

 

The large oblong opening is for alternator scoop. I did make up an actual scoop but testing with a laser thermo gun on alternator after a run without undertray, with undertray and scoop and with undertray as shown yielded the very same readings.

 

Interest results.

However, I keep coming back to the thought that Jaguar would not have spent good money for the stock alternator ductwork if it had not served a needed purpose.

Z

 

Good thinking to check Alternator temp delta.
I notice you have an XKR. The Bonnet vents create a negative pressure to promote updraft around the engine. It might be that your oblong opening is extra effective because you have blocked other air flow paths.

 

I dont know what was under your car originally but I would have thought all the aluminium would have restricted airflow around the engine and the gearbox...not a good idea.

 

Ideally all air entering the engine bay should enter through the radiator grill and any other opening in the nose. An undertray actually aids that entry and also the exit by reducing the entry of air from below as well as smoothing and speeding flow which lowers the air pressure in that region.

 

There is very little space around the engine for hot air to exit ( hence hood vents ?) so I dont see how a big slab of ali can help airflow . your car your decision.

 

Pistnbroke- ?

Have you seen the Undertray on a 2005 or 2006 XKR? They are made of Plastic and are almost as large as Baxtor's Undertray.....Beleive it or not...Air travels under the Car too! It certainly helps smooth-out the Air! Jaguar's cost for this piece of Plastic is around $300.00.! I think the Aluminum or Sheet Metal one is really a great idea!

Billy Clyde @ Cinco Ranch

 

BC price ..must make a note not to help you...The first example of unnecessary rudeness I have seen on this forum.

I did say I dont know what was under the car originally so if jag did it it must be OK though I suspect its more to do with damage to pedestrians than airflow.....tougher testing regime

 

PISTNBROKE,

Sorry you think I'm Rude! Just trying to point out that there's a large area under there that needs to be covered up with something and if you don't use what Jaguar put on there...Then what Mr. Baxtor used looks pretty good....I think so anyway.................. Sorry you are having a bad day! Also, remember to listen to older people.......

Billy Clyde @ Cinco Ranch

 

I think this guy knows his way around a brake/press, or whatever we call it. Looks good to me and I like it. TM
YMMV, not sold in AK, HI or CA. Always consult a professional before beginning.

 

Gentlemen:

Have you noticed that most of the High-Dollar Sports Cars have a "Belly-Pan" that covers most of the underside of the Car? I'm thinking Ferrari, etc.! The one Jaguar put on our Cars is very small compared to some of those that cover the entire Underside...Personally, I like the idea... as it has to smooth-out the Air-Flow underneath the Car....especially at High Speeds...!

Billy Clyde @ Cinco Ranch

...

 

An undertray is a great thing. Another thing to consider is that often a factory undertray is lined with an oil-absorbent material to capture any oil leakage which is a not only a nod to the environment, but also prevents embarrassment at parking your leaky, hi-end car in the driveway at the homes of friends and family who chided you for buying the thing in the first place.

Now you must design in a little bit of an air gap away from hot engine parts, but look into something called Pig Mat as that's essentially what the factory installs (tho Pig sells a couple dozen different varieties and I couldn't tell you which one is closest to what Jaguar uses). Some years ago I had a water pump catastrophy that completely saturated the mat in the XF and after a while the material was starting to disintegrate. Rather than buy a whole new undertray, I already had a package of Pig Mat sheets that I use around the shop for oil spills that seemed quite rugged so I just scraped the old oil-absorbent material out of the undertray, cleaned up the surface and glued in a couple sheets of that Pig Mat as a replacement. It's been in there a couple years now and seems to be holding up just fine, tho I haven't had any leaks to really test it.