Hi, I just finished the installation of a new, custom cold air intake upgrade on my '94. Given the stock intake necks down to 1.5 inches, but the throttle-body opening is 3", I used 3" as the minimum area throughout. I printed all these parts off my 3-D printer. I included a canister, K&N style filter (inside the metal can that you see in the pictures), which doubles the filter surface area of the stock filter. I also designed new intake mouths (on top of the radiator) to ensure no restrictions on the 3" area. I am super pumped with the results. The car sounds different - with the small intakes, it sounded a bit like a shop-vac when it was started, because its sucking so much air through that tiny hose; now its actually quieter


The car was noticeably more responsive, too. I have a spot where if I floor the car in Sport mode, I can just hit 60MPH between the intersection and a bridge. With this new intake, I hit 65MPH!!! - no joke. Over the next couple weeks, I'll monitor the MPGs to see if there is a measurable change there too. One of the best car mods I have done lately. If you have a 3D printer, I'm happy to share my designs and what I learned. Super fun project that cost probably about $150 in materials, including the two big air filters.

 

Very nice!
Am I right in thinking the later V12 had a more raised bonnet/hood in the centre, to accommodate where your cold air feeds get the cold air from?
Also what's the sensor on the RH front elbow?

 

Hi,
The original intake vent (the outer/front section) actually has sufficient area (i.e., if you calculate the frontal area, it is slightly greater than the area of a 3" diameter tube); this front vent is not a pinch point in the intake. So, I used the original front vent section, printed out a new back section that provides sufficient area to maintain unimpeded airflow, and screwed them together. Regarding the hood center, I'm not sure if its raised compared to older models or not. Its a snug fit, but all the new intake sections, and the new filter section, all fit under the side hood line, so you don't need to worry about height of these parts. To your point, if the center of the hood is lower, than those front vents may need to be widened to achieve the needed frontal area. I'll have to look at some more pictures of the earlier models to be sure. My front vent is about 45mm high and 135mm wide.

I hooked up all the original hoses and sensors in essentially the same spots. That driver's side sensor I believe is a mass-airflow sensor that is upstream of the filter on the driver side. There is a similar mass-airflow sensor downstream of the filter on the passenger side, but you can't see it in these pictures (its on the underside of that last section attached to the throttle-body).

 

Great mod, and it definitely does make a difference improving the intake path. I think that sensor is an air temperature sensor, it certainly is on the %.3 HE engine.
Asdrew: The later facelift V12 engined cars used the same bonnet as the pre-facelift 6 cylinder cars, which all had the hump in them to clear the nearly-upright 6 cylinder engine. On pre facelift V12s, this intake system cannot be fitted in unless the radiator top panel is very heavily modified, which is very hard to do with the standard cooling system purge layout.
5.3 litre owners have usually modded the intake through the front wheel, front wheelarch to an opening under the bumper.
In my view, the most cost and effort effective intake mod for the 5.3 is to fit larger trumpets to the OEM airbox, and replace the oEM filter with an ITG foam one:
https://www.itgairfilters.com/
If funds allow, the absolute best thing is AJ6's super enhanced ECU and large throttle body kit, which comes with all this done, and that REALLY wakes the 5.3 up. i have this, as do several friends and it is the business.
Cost Effective V12 Upgrades Guide | aj6 engineering

 

Hi Greg,
I'm waiting for my SE ECU.
To add the large throttles is quite a lot of money.
Do you have any experience with performance improvements with just the ECU?
I could be talked into the throttles if that's where most of the power lies.
Thanks,
Rob
planning an '89 XJS; ABS to non-ABS, 5 speed from Simply Performance, 3.54 diff. delete forward mufflers. SE ECU

 

Sorry, no. But on my car the two made a huge difference, from takeoff right up to top speed. Acceleration above 90 MPH was just electrifying compared with beforehand. Just starve for a bit and splurge! I have two friends who have done both and they to found the difference astonishing. Very highly recommended.

 

I've read the air flow on the oem throttles wasn't in impediment as they're sufficiently sized unless your planning to drag race. The ECU upgrade is well worth it, I plan to do it this year if possible.

 

FWIW I've twice used "SE" ECUs from AJ6 Engineering and they work as advertised.

As for throttle bodies.....

I'm looking at lower cost alternatives. I believe Grant has used original throttle bodies enlarged to accept XJ40 throttle blades and reports good results.

Cheers
DD

 

No reason why a fabrication shop couldnt enlarge the OEM ones and 'make' new butterfly flap thingies for it. I have a few sets if you want to try

 

Nvm I found better posts. So the xjs is 63mm. Xj40nis 71mm. And AJ 6 is bored out to 73mm. So even going to a 71mm would be decent. And enough for any normal 5.3l

Maybe ill looking a shop that can bore out. See what the costs are as the aj6 kit (tb and ecu) is about 1700cdn. Before shipping an dimport duties whereas the 71mm disks are only about 120 cdn dollars

 

Thats roughly 1.6 square inches different I would think even just air rams shunting cold air in by force would do more as far as volumn is concerned then 3.2 square inches total?

Again not an engineer but cost/benefit seems iffy? Or am i math'ing this wrong haha

 

Hence why u need a reprogrammed ECU to accommodate the increased airflow to add more fuel or it might run lean. I think anyways lol

 

Correct. But using XJ40 throttle bodies is a good substitute for the AJ6 items. You still need the ECU done by them of course, and you need better filters, which they also supply as part of the entire kit.

 

Is it the whole xj40 tb? Or jut the disc? And I've read some use the 3.6 and some use the 4.0 ones?

 

I don't know, but Grant does!

 

I tried ordering the disc's only and just got an email from sng saying Jaguar no longer supply part EAC4820.

 

Rescue
Grant got he TBs from a breaker, just used the butterflies and spindles, and then had a lathe guy bore out his XJS TBs.

 

Ya not to any breakers for anything jag related close to me at all. And with covid I can't go for a day drive. I think I know a place but it's 5hrs away and have been trying to get there for the past year lol.

 

I have a pair of XJ40 throttles, and a pair of V12 throttles, for sale, for $100 USD plus post, if that helps,
Rob