I'm still trying to learn what people who have owned V8 Jaguars think of the design of the 3.0 V6 and whether it is a kludge or an intelligent re-engineering of an existing design.

If you were not aware the 3.0 shares the same engine block casting with the 4.2 and 5.0 V8s. The last two cylinders are simply plugged and the block was not shortened. Normally, when a V8 has been converted to a V6 (cough, Buick, cough...) the block has been shortened to remove a pair of cylinders. In case of Jaguar that was not done. The cylinder heads, on the other hand, are shorter than V8 heads.

Likewise, when a V8 is adapted for V6 use (cough, GM, cough...) the engine is either distinctly out of balance or balance shafts have eventually been used. The "optimal" configuration of a V8 uses 90 degree separation between banks while a V6 uses 60 degrees.

Jaguar being Jaguar, it was clear that an unbalanced engine would not be acceptable, but instead of using balance shafts, or designing a whole new engine, a "split-pin" crankshaft was used instead.

What I understand about "split-pin" is that the crank journal that connects to the bottom ends of a pair of side-by-side piston connecting rods has been "split so that the bottom ends are no longer linear with each other. They are now displaced along, what I expect is, a horizontal plane. That displacement is intended to correct the 30 degree cylinder bank difference between a V8 and V6 and to smooth out the engine.

So, I'm wondering, what do we V8-type folks think of what Jaguar has done to our engines to convert them into a V6? Is it good engineering or a kludge? Is this design a stop-gap that allows TATA more time to design a true V6? And if the 3.0 engine block is the same length as the V8, why did Jaguar go to the expense when a V8 would fit in both the new XF and the XE?

Thoughts?

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Are you asking about the AJ30 or the AJ126 engine?

 

OP, do you mean THIS V-8 block??

 

>Are you asking about the AJ30 or the AJ126 engine?

The AJ126 used in the XE, XF, F-Type.

But (you didn't say but I'll assume you were going to... ;-) when I look it up in Wiki I saw that it says: "The engine features a balance shaft to drive the oil pump and balance the crankshaft.", so I may have been wrong about not using balance shafts.

And while it is not an exact copy of the V8 block, it is still the same size, and is still at 90 degree design:

https://www.google.com/search?q=pict...1VAmzNcRL0xLM:

 

>OP, do you mean THIS V-8 block??

Nope, I meant this one:
How Jaguar Land Rover Cleverly Creates a V-6 from a V-8 ? Feature ? Car and Driver | Car and Driver Blog

 

Holy CRAP!!




Is that the same V-6 that's used in the XJ series??

 

Curious what sort of responses you get here. I had a theory but its pure speculation. Since they were introducing the start-stop feature, I assume required in many markets, that six cylinders at a 10.5:1 compression ratio might be quicker, smoother and require less energy to restart than eight cylinders at 11.5:1 and by adding the supercharger, they could get nearly the same power. But that's just a guess.

Being a DIY mechanic, buying pre-owned and maintaining my own cars, typically to advanced age, the mechanically much simpler na v8 would seem a better choice in the long run.

 

Interesting perspective, on the V-6, with respect to the start/stop deal!


And I whole heartedly agree with your comments about the NA V-8. I hate to keep crying over spilled milk, but that's even more reason for me to be "POed" at the dumbazz who rear-ended our 2012 XJ-L, totaling it. Yeah, the 2016 that replaced it is nice, but we truly miss the V-8 that our first one had...........

 

>Is that the same V-6 that's used in the XJ series??

Yup...

and the XF, and the XE, and the F-Type, and a bunch of Land/Range Rovers...

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Well my 2 cents is the engine sucks. It runs rough, shuts off like crap and gets not much better mileage then our XJR. Then again, having driven the 4 cylinder, it isn't the worst engine Jaguar sells now but it is a whole lot worse then the Duratec based 2.5 and 3.0.

 

YUCK!!


I'd expect that kind of "parts engineering" in a pedestrian ride, such as Ford or Chevrolet, but not a high end marque such as Jaguar...........

 

Its standard practice in luxury and niche marques. Its very expensive to develop a car from scratch and such extreme low volumes as the current XJ could never in a million years repay its development costs if every part were designed from scratch and unique to it. To see how extreme parts-bin manufacturing can go, study Lotus cars.

 

>Its very expensive to develop a MOTOR from scratch...

Then why did they feel the compulsion to stop producing the NA 5.0?
The 3.0 is inferior to that engine (for all the reasons discussed above) and doesn't provide any significant improvement on economy or emissions.

The V8 still fits all the cars, so why go to the effort of *******izing it into this V6?

I just don't understand.
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Current: '08 S-Type 4.2 "Satin Edition" (250.06 whp / 259.67 torque)
Past: '05 X-Type 3.0/auto Jaguar Racing Green

 

 

I think the EPA mileage ratings for the 3.0 are slightly better than the 5.0, and Jaguar needs every MPG to meet CAFE requirements. In practice though, there is very little difference. There is a 160 mile round trip that we do frequently in our XF 5.0. One time, we had an XF loaner with a V6 and made the trip in that car. Under the same conditions as usual, we got exactly 1 MPG more in the V6. Now that the 5.0 NA is gone, the best feature of the XF is history. I'm glad I got mine when it was available, but I won't be buying an XF V6.

 

We aren't seeing more than about a mpg better then our XJR (which is almost as bad as our motorhome). Granted the XF doesn't see a ton of highway so that tranny doesn't get to idle around at 65mph. In a CAFE test, I'm sure it gets what they claim. I'll stick with our XK8 that if I keep it under 70 or so I can see 28-29mpg on a trip.

 

Some engine snobbery going on here.

Yes, it was a cheap solution to blank off two cylinders.

However, you get the same block that makes 550+ hp in R and SVR trims.
This suggests that V6 SC has relatively robust build with good tuning potential.

Take a look at the Jaguar line and you will quickly realize why Jaguar uses it.

You can have 1 engine and 3 different trims. Base, S and new 400PS version. You just adjust the pressure. Can't do that with NA engine. It is lighter than a V8 and that aids weight distribution too. I am sure its emissions are better than NA V8.

As for the economy, I constantly get 28mpg + on the highway @ 65mph in XE AWD and 19mpg in very busy city driving with Start Stop ON. I think that is respectable for 3800lb AWD sedan with 340hp/450nm.

It is another added benefit that it can sound great. Albeit V8 can sound great too.

If you want to critique V6, talk about its length, heat management, and NVH. It is rough on idle and very long for V6.

 

I agree







But how much lighter is the V-6 version?? I realize that you remove 2 pistons, 2 connecting rods, 2 fuel injectors, and several valves. The cylinder head castings might be a few pounds lighter, too. HOWEVER, they then bolt a supercharger on top, to get back the lost power, but the V-6 is still down 40 HP, to the NA V-8. I understand that the V-6 cars are supposedly 200 pounds lighter than the earlier V-8 cars, but I highly doubt that weight loss comes from the engine. And if the V-6 block was a TRUE V-6 block, it would definitely be lighter, and also being shorter, it would improve the weight distribution of the car.


With respect to fuel mileage, yes our V-6 XJ-L is pretty good, for a full sized sedan, at least according to the onboard computer. However, our '09 V-8 powered XF will provide 27-28 MPG, at a steady 65 MPH.....pretty much the same as our '16 XJ-L.

 

Sounds like crap to me and I did critique it for its horrible idle, horrible shut down noise, horrible fuel mileage, poor performance compared to everything else we one. Heck I'd rather listen to our 454 with banks heads. I cringe every time my wife pulls that XF into the driveway and shuts it down. Even took it in hoping that it was a loose exhaust shielf but they said, they all sound that way and low and behold, the XE they used off the lot sounded just as bad.

 

I remember reading somewhere that there are many countries that place a "luxury" tax on any motor with an engine over 3.0 liters.

If you look at almost all of the automobile manufacturers, most sell a 3.0L.

I wonder if that is true and if it is, could be why so many sell a 3.0L.