Nice 2 hour drive today and toured West Point . The security guys were great and loved the car. So to my question as I was driving back home and going up and down some pretty big hills I notice that the car does not really coast or free wheel while off of the accelerator doing 60-70 mph. Seems I get more engine braking then I would expect. I would have thought it would coast and pick up speed but it doesn't seem to do that. Just an observation

 

Not quite sure what you mean. I would assume you don't have the cruise control on.

You take your foot off the accelerator and the car slows down?

I would think if this is the case, everything is normal. I have never come across a situation that when you take your foot off the gas pedal the car continues to coast at present speed. For me, the car has always started a slow process of slowing down in speed.

Perhaps you can explain a bit better what is happening. I don't think you can expect the car to maintain a constant speed. Interior weight, incline or decline in road conditions would also be a factor in the car slowing or maintaining some type of speed.

 

No, the gearbox stays engaged - if you drop the engine revs, you get engine braking. Back in the day, automatics were notorious for lacking engine braking, but they seem to have fixed that in the modern 'boxes. You'll find you get even more engine braking in 'S' mode.

 

OK maybe I didn't explain it right so let me try it this way. Once again I am going down a steep hill at around 60 mph not in CC and foot off of the gas. It just seems like it does not speed up much while going down the hill. As an example my Lexus while doing the same continues to speed up and also the rpm's drop too which the Jag does not. I would expect the car to slow down lets say when on a flat and take my foot of the gas but it seems it slows faster then my other cars. Now mind you I don't think there is a problem but it seems the engine braking is more pronounced on this car. Just my seat of the pants feeling.

 

On the S-types, the transmission selects a lower gear to prevent the car from speeding up while going downhill. Possibly the XKs do the same thing. I like it.

 

OK thanks and I can buy that . I haven't tried it in S mode but I suspect it would do the same if not more. As i mentioned My Lexus would speed up faster and the transmission would drop out and the rev's would drop down to around 1200 rpm while the car is doing 70 mph. Almost like free wheeling .

 

The early XJ12Ls were notorious for just keeping going when one took their foot off the gas on level ground and actually sped up when going down hill.

 

Noticed that myself.

My 97XK8 had much less engine brake but I would expect that was do to 5spd vs 6spd.

Also the engine braking is more noticeable in sport mode due to the fact the engine maintains higher rpms so when you let your foot off the gas is does slow down faster. Not so if you use the paddle shifters as you control which gear your in and how many rpms the engine is pulling.

 

I think that's right. 6th isn't really an overdrive as such, it is a proper accelerating and decelerating gear, over 100kph or so. Though if I really wanted to accelerate or decelerate, I'd flick it into 5th

 

At full throttle, mine doesn't shift into 6th until it hits 177 mph.

DpezXK8, it's actually the other way 'round - in 'S', the transmission keeps the car in a lower gear, and that pushes the revs up. As you say, that leads to more braking effect when you come off the gas.

 

That's correct Ngarara, I think you just read it wrong as I didn't mention gear, just that the car runs at higher RPMs in sport mode, and that is because it is in a lower gear which causes more engine braking.

That's why you downshift to increase RPMs and engine brake force to slow down without applying the brake.

I really don't use my paddle shifters because the car can accelerate a lot quicker without interference from me. I do and did find it handy when driving in the mountains of galena territory when I went on a trip. The adaptive cruise doesn't work very well on hilly/curvy terrains which didn't bother me as I was having way to much fun with the shifters to maintain speed on steep grades and curves.

And lucky you that you can hit 177 mph, here in the states we are limited to 155 though I haven't gotten there yet. Mine goes into 6th at 55 on the expressway <why they call it that I have no idea at 55. Also not in sport mode, just drive.