I'm still breaking in my car and I'm not a huge fan of launching the car, but I'm curious to know if the car would have better acceleration numbers if u start in 2nd gear vs 1st. What about dynamic stability control- on, track dsc, or off? Thanks

 

Research the car mags tests of your S, sometimes they mention how they got the best launch, maybe also check out the top gear episode for the S, they might have shown how they did it.

 

1st gear, roll on the throttle... i.e. it takes finesse

I hope they never install launch control, the industry is taking all the driving away from the driver. Then again I love the slushbox in this thing

 

I would think the best is in 2nd -- there's so much power on tap that it's easy to overwhelm the tires even in 2nd, let alone first. Mind you, I'm not a professional -- I don't even play one on TV! I've not really had a warm dry day to try it out on yet -- it's been wet since I got the car. O.o

 

Suggest a lot of track time. Practice makes perfect and I assume you aren't planning on any street racing or are you?

 

No street racing-too unpredictable and dangerous. I am looking forward to R driving academy- anyone here been ? What did u think?
I do have some experience in racing-bondurant, track days, auto cross, but I'm not planning on tracking the Xkr-s. I need a dedicated track car.

 

Octurbo,

I'd tell you to buy a Subaru (in jest, maybe too much of an inside joke), and advise you to launch from first gear. You have more horsepower than I do (2010 XKR coupe), but the same gearing. All my attempts at an optimal 0-60 have made it 100% clear that 1st is the only way. Yes, traction is a challenge, even more for you in the -S, but second gear launches aren't the answer. The crazy amount of torque makes second gear starts a possibility, but in no way optimal if you are really trying to nail 0-60 times.

People here more knowledgeable than I have suggested that (especially the supercharged 5.0's) suffer from lack of traction and are only capable of a mid 4 second 0-60 time. See thread on topic for details and a bunch of noise (much of it from me, in retrospect). In fact your results will be the PERFECT way to verify or negate this theory:

If traction is the gating issue, you'd expect your car and mine to turn close to the same times. If, on the other hand, you can turn in 0-60 runs significantly sub 4.4, then more power is helping and traction isn't an impediment to faster times if more power is present. That'd certainly get me interested I mods if you can turn significantly faster times (say flat 4 seconds or less) with an extra 50 or so horsepower...

Of course even if traction is an issue you'll turn a faster times, since when you DO hook up, you'll be able to put the power to use... How much faster will in my mind indicate whether traction is a hard stop to pushing for faster 0-60 times.

Short answer, launch from first for sure, feed as much power as grip will allow, then the consensus was a manual shift via paddle to 2nd gear at ~5-5.5krpm. I think that's what we concluded.

I haven't had the time or conditions to try and get better results, from posts here the best we have done on this platform is a 4.4 run to 60. Which, considering how blisteringly powerful the normal S5.0 feels, seems low to me.

It'd be cool to see what an XKR-S adds to the discussion and puzzle, so keep us posted.

Thanks,

Skeeter

 

Oh, a

Traction controls off, in dynamic mode, I get best results with everything off, in 'S' mode (transmission), shifts via paddle. Bit mix it up, maybe results will differ.

Good luck,

Skeeter

 

A recent dyno posted in the XJ (351) forum shows the stock 5L S/C peaking and holding power to redline...definitively making a 1st to 2nd shift at redline the optimal shift point. The XKR-S has a less restrictive exhaust which would increase the engine's volumetric efficiency in the mid and high rpm band, and make the higher rpm 550 bhp gains at or close to redline also.

I've never noticed, but what speed is first gear good to at redline?

Bruce

 

What in addition to the less restrictive exhaust gives the S not only the extra HP but more importantly the extra torque; I'd guess it's higher boost pressure. Was the trans reinforced to handle the additional 40 hp and 50 lb ft trq?

 

Jag states that the Xkr-s has changes to its engine mapping, which I also assume translates to increased boost. What is the boost on a Xkr?
There was no mention of any changes to the transmission

 

Don't know OC, I'm new to Jag.

Yes the remapping probably increased boost and fuel richness (to help with detonation from the higher boost pressure). It would be interesting to know how much of a gain the exhaust vs the boost is responsible for; I'd imagine the exhaust is good for 10-15 HP and the boost for the rest. I'd also venture to say the boost increase accounts for almost all the torque gain.

 

No boost increase on the S. Increased airflow from increased volumetric efficiency, and increased power from that airflow from more aggressive mapping of fuel and ignition. Your 2012 can even match it's hp and tq with just ECU tune also according to the recent ECU Tuning thread.

Bruce

 

Wow Bruce thanks for this. Hard to imagine though 50 lbs ft of trq increase just from fuel air and ign.

I've read the supercharger in the XKRS is the same as the one used in the ZR1, so is it safe to say the XKR has the same?

 

Word is that the only power difference comes from exhaust and software. Seems like a big gain, maybe the standard XKR is sandbagged a bit? Waiting to see some before and after Dyno results to back up the claim that an ecu tune gets the XKR to within 10-15 HP and lb.ft. of the XKR-S.

That's the claim, and looking through parts lists, all engine parts are identical as far as I can see. Same blower.

Skeeter

 

Yes, the blower the 5.0L engines have is the 4 lobe supercharger used in a number of currently shipping toys, including said monster Vette.

In fact, that supercharger was a big reason for me hunting down a 5.0L car. <wicked grin>

Actually, Car and Driver had a little blurb on it recently. Check here for a cutaway pic: Prime Cuts: Eaton TVS R1320 Supercharger - Feature - Car and Driver

 

Thanks for the info and article gents.

With such an easy way to for Jag to get the S's power increase I wonder what justifys the huge price difference between the R and RS? I realize the S has lighter suspension pieces and bigger brakes.

 

iirc the S also has an uprated torque converter, better exhaust and probable some more things here and there.

The extra power doesn't come from tuning ignition/fuel, but more from lifting power reductions that have been programmed in the ECU.

 

Power reduced by the fuel and ignition settings??

 

Power reduction is achieved via throttle control, much smoother...