That sounds right to my recollection. I recall thinking that the NA 5.0 was a bargain considering the performance. I drove an XJ so equipped and would not have sprung for the XFR had I been in that market at the time. That 5.0 is quick.

The other difference in the V6 SC is the flat torque curve. NA engines have torque curves that droop as rpm increases.

The V6 not only feels quicker than the 4.2 V8, it is quicker. Also, once the V6 gets off the line it is very quick, that 8 spd keeps the engine in that flat torque curve and the car just sprints.

I'd be very interested to compare the new V6 with the NA 5.0 V8 over say 40 mph to 70 mph, in full automatic mode, and see if the V6 is quicker. I think it would be.

 

On the contrary, once you get moving torque won't matter much.. It would be much easier for the car with more hp to outrun the one with less.

Torque is great at take off, once you get moving, hp is what you need.

The 5 liter engine has extra 40hp and 48lb-ft torque. That's a significant amount of power increase.

 

Though I think the 3.0 SC is a great engine, like Dan Quayle was told, "You're no Jack Kennedy" - and the "3.0 SC is no 5.0 V8". It will be behind, but not by much, any speed or quickness comparison with the NA 5.0. As far as a comparison of passing acceleration,

Car and Driver tested a 5.0 XF (2010) and a 2013 XJ 3.0 SC (rear wheel drive). Their curb weights were basically identical. The results (5.0/3.0): 30-50 mph - 2.6/3.2. 50-70 mph - 3.5/4.1. That's 23% quicker 30-50, and 17% quicker 50-70. The margin would be quite a bit wider with the 3.0 AWD version.

The fact that the 5.0 has 380lb-ft at 3500 RPM versus the 3.0 SC at 332 lb-ft between 3500-5000 means that there is an extremely wide band of RPMs where the 5.0 will have more torque, by a significant amount. The talk about the 3.0 being as quick or quicker than the 5.0 just isn't going to hold water. It's quick, but not that quick.

 

Not really, hp is just torque x 5250. In that sense torque is horsepower.

Torque is force which is why it has to be expressed as lb ft ( not ft lbs which is work, a different idea). Only force can accelerate. F= ma or a=F/m more usefully.

For acceleration the difference in torque developed by the engine as multiplied by the transmission yields the acceleration of a given mass. In the helpful post setting out the actual numbers achieved by Car and Driver the mass is considered to be identical (weight is proportional to mass by the acceleration of local gravity, denoted g in lateral accelerations for example, and may be used interchangeably at the same elevation and coordinates on the earth's surface) and given the 5.0 superior torque over the applicable rpm of the 6 spd compared to the torque of the V6 SC even with the 8 spd is sufficient to produce the superior roll on acceleration.

I'm a little surprised frankly, but numbers is numbers.

I cannot find those numbers, is there a link to the C&D article(s)?

 

It's X5252 to be exact.

2010 Jaguar XF 5.0 Premium Road Test – Review – Car and Driver

Car and Driver test results for 2010 XF are as it follows:

C/D TEST RESULTS:
Zero to 60 mph: 5.1 sec
Zero to 100 mph: 12.0 sec
Zero to 120 mph: 17.6 sec
Street start, 5–60 mph: 5.3 sec
Standing ¼-mile: 13.6 sec @ 106 mph


I was actually being conservative with my numbers. 0-60 is 5.1 as tested.

Will look for a test with the new V6SC model.

 

The only close to apples to near apples comparison was with a 2013 XJ 3.0 SC. The curb weights were within 5lbs, believe it or not, and the results were 5.2, 13.8 Quarter, 5.5 street start. So, pretty close, but the passing times were .6 slower than the XF. I think the trans kicks down faster for some reason on the 6 speed, though they mentioned on that particular 2010 XF, it seemed to bog at first under acceleration. I have seen 5.0 to 60 posted on C/D for the NA V8.

In any event, let's enjoy!

 

The new V6 SC won't be much lighter than the V8 NA because they use the same block and virtually the same sized crank. The six loses two pistons, rods and a journal, sort of, and adds balance shaft and supercharger.

 

Thanks, this is very close to what I recalled (I said 5.0 seconds). It might have been listed as 5.0 seconds on Jaguar's web site. That is the quickest car I've ever owned. Plus the total lack of any lag off the line makes it feel even quicker since the power is right there instantly when you put your foot down. I'm not knocking the 3.0SC, and 0-60 in 6.1 is nothing to sneeze at, but it's just not quicker. I'm sure if I had a 3.0SC, I would enjoy it thoroughly.

It seems Jaguar left the XF with a bit of a void now that the 5.0 non-SC is gone. In my opinion, the 5.0 non-SC gives you a lot of power, but not ridiculously so. Now, if you want a V8, you have to step up to the 5.0SC, which has way too much power for a sedan. If I were buying today, it would be a tough choice, especially considering the price difference between the V6 and V8 SC model ($53k vs. $68k). The 5.0 non-SC at around $60k, was right in between the two and hit the sweet spot in price and power.

 

Car and Driver uses very aggressive starts to get those numbers. They take the torque converter to stall speed and then launch. I think they even get a one foot rollout lopped off the number.

Jaguar's factory number is much more realistic.

Also, unless you are at sea level you'll not see those numbers on your stopwatch. The supercharged engine should get the same numbers at any elevation from sea level to at keast 10,000 ft. Which reminds me, I drive at 3,500 ft where I live so my V6 SC will accelerate much better than my 4.2, which is what I'm comparing it to, seat of the pants. I also have yet to floor it, 900 km to go before I do that. Air density at my house is only 90% of that at sea level. Drop 10% off those hp and torque numbers for the NA 5.0 and you'll see why my car feels quick when compared to the 5.0 driven at the same elevation.

 

Definitely at altitude, forced induction helps keep the power up. There are all kinds of discussions about super versus turbo charging and altitude in the web. I know there are a couple TFL reviews (from Boulder) - one is a comparison review of the 2012 Portfolio against the new GS350 (which is a really big step forward for Lexus on the driver involvement front). They both preferred the XF, though. Another segment was the 2013 3.0 AWD. Their numbers (at 6000 ft) showed the V8 at 6.6 to 60, and the AWD at just under 7.1, which would mean the non AWD 3.0 SC probably would be a bit quicker than the V8 at that altitude.

Anyway, it also shows that there is still loss at altitude for forced induction - just not as much. In the case of turbos, there is more lag as the density is lower and it take a little longer to get spooled up and have to turn at faster rpm to maintain the same boost. Superchargers don't suffer the lag issue, but since they rely directly on energy from the engine itself, the argument is that there is less energy from the engine, therefore less to turn the Roots blower... General rule of thumb is 3% loss of power per 1000 ft for non aspirated and half of that for forced induction. Maybe a little more than half for supercharged engines.

 

My SAAB Aero loses no power with elevation until you get over 10,000 ft. The reason is the type of boost pressure control. SAAB uses strictly detonation limited boost pressure curve profile. Only when the air gets too thin so as to be outside the optimal pressure capacity of the compressor does air pressure matter.

Lobe type superchargers are less efficient than centrifugal compressors but boost better at low "compressor" rpm. Centrifugal compressors tend to have fairly narrow efficiency ranges but as long as they remain within that efficiency band keep building boost as compressor rpm increases.

One big advantage to modern lobe superchargers is the ability to fit oversized "compressors" and modulate boost pressure by dump valving (bypass actually) using software and valving invented to control over boosting of turbos.

Lobe type superchargers aren't compressors, strictly speaking, but displacement type air pumps. The pressure rises in the intake pipe downstream of the supercharger, not in the supercharger itself. Turbos (and centrifugal superchargers like Vortex) actually compress the air inside the compressor snail. Mechanical lobe type superchargers cannot fully compensate for altitude or elevation effects as they just move air at the pressure it arrives at their intakes to the outlet of the supercharger, so less air to begin with means lower pressure built up at the output. Only by providing for, in effect, over boost can such superchargers adjust for elevation effects. The Jaguar V6 must have significant over boost capability to preserve power output with increasing elevation. That's certainly my impression.

 

Actually...
Horsepower = (Torque x RPM)/ 5252

One could say that Horsepower is a by product of torque and rpm as it literally is.

And what "Jagular" was getting at, in reference to the flat torque curve for the forced induction motor, is if you hold your torque for longer into the rpm band, will translate into more horsepower. This is what is commonly referred to as area under the curve, where instead of referencing peak values only, you reference total usable power.

0-60 are great indicators of a car's performance, a quarter mile test gives you that much more (not just the time, but the trap speed), and finally your 50 - 70, which some care reviews will provide, give you a definitive feel of passing/ overtaking power...

At the end of it all, chances are the older 5.0 n/a V8 was overall faster than the SC V6, but that's not saying the V6 is a slouch. and the V6 boasts much better fuel economy ratings...

 

Simply put: torque produces acceleration while horsepower produces speed.

Power states the capacity of the engine to perform work over time. Exert the torque for a specified period of time and the power number will indicate the ability of that engine to produce and maintain higher and higher speeds.

This is why high torque engines are valued in North America where high speeds are just not permitted in practice. In Europe high speeds may not be permitted legally but enforcement practices mean they are permitted in reality. Not so in North America where driving at European speeds will soon have you walking.

 

Why is the NA 5 speed limited in the usa to 120mph. It seems a waste to me as the car accelerates and seems to have a lot of torque left at 110mph ? I do not get that nor am i content that it limits at 120mph.

 

Well, she looks like she's about 29. Did you take here across the street to Krystals for her birthday dinner after that?