Greetings fellow motorheads:
I've been searching the forums for any info on this topic, but I haven't found anything. So I'm starting a new thread to see if I can learn why Jaguar chose a displacement of 3 liters for their V6?
I know it's been a good engine, with plenty of power and torque, but why not a 3.8??
If you do the math, you will see that lopping off the front 2 cylinders from the 5 liter V8 gives a 3.75 liter V6. If the factory bored the cylinders .010 over, this should give the all-important displacement of 3.8 liters.
Isn't that what the factory did for the '03 XK8, when they turned their attention to addressing some issues with the 4.0 V8? While tending to the timing chain tensioners, etc. they close to bump the displacement up to 4.2 liters. One would think they should have gone up to at least a 10% increase in size, but we all know how important that 4.2 number is to the Jaguar brand!
So, can anyone explain why the factory didn't use the equally famous 3.8 displacement for their excellent V6 engine?
Thanks in advance to anyone who may shed some light on this subject!
Curious in Pa.

 

Not sure if you'll get an answer from this, but I remember some details being in it when I watched it a few days ago.

 

It's actually the back two cylinders they lost!

 

I am not sure how much this mattered to Jaguar/Land Rover, but there are countries with vehicle tax structures based on displacement. This is the reason many engines, the Jag AJ126 3.0 V6 included, are just slightly BELOW their rated displacement. In this case, 2995cc. Since the engine was used in other vehicles such as the XE, XJ, XF and Range Rover, it makes sense.

There is another factor, 500cc cylinders are considered ideal by many, with regard to efficiency and emissions.

Smaller displacement V6's are absolutely smoother and more pleasant engines. The Ford 3.5L Ecoboost groans like a UPS delivery truck. The Ford 2.7L V6 Ecoboost sounds like a racecar.

A bit off topic, but the most interesting of all V6 designs is probably the ideal 120º V6 design. Audi made a racing 120º Diesel, and McLaren may be making this "Hot Vee":





https://images.cdn.circlesix.co/imag...7da62631a9.jpg




Audi racing 120º Diesel

 

I blame climate change!
Seriously, cujet is right, it was all about "emissions", engine capacity and Euro tax brackets.
And it's not just the bore, the stroke was reduced over the V8 as well.

 

Interestingly, after a few early teething problems, the V6 has turned out to be a stunningly good engine. Not only far better than the unusual configuration would suggest, but truly great, with a world class 133HP per Liter of displacement in it's highest output OEM form, despite modest boost levels. It's tough, holding up to racing use without difficulty, and handles significant performance enhancements without difficulty. VAP tunes these V6's to 550HP with E85 and pulleys.

The other aspect is the fantastic exhaust note. There are very, very few engines that sound as good and are as playful. Absolutely zero lag, instead, you get glorious instant response.

From a performance point of view, While the V6 falls quite short of the blisteringly fast 200mph V8 SVR, the F-Type with the V6 is at least reasonably competitive with other mid level six cylinder sports cars. With it's 170MPH top speed and mid-high 4 second 0-60. Hell, the best V6 versions can break into the 12 second 1/4 mile range at about 110mph with good tires and superb fuel.

Here is a stock V6 reaching the 171mph speed limiter.

 

Certainly there's room to put a 6-cyl under the hood that was more than 3L. As you noted, the AJ126 was derived from the 8-cyl AJ133. But, doing that allowed Jaguar to utilize the same base design vs developing one from scratch. And, being a small scale manufacturer, that was an important consideration.
The Jaguar 3.8L is an in-line 6 and too tall for the F-Type's snout.