Are the mods worthwhile ?
 

I continue to see posts on mods with pulley , exhaust and tuner changes. I also don't see to many that do baseline data gathering to see improvements. HP increases seem to be about bragging rites as the performance data isn't much significant from stock. So what is the real benefit here . Doesn't everyone run before and after dyno results and then go and get actual strip times. Just by the shear questioning of the results there doesn't seem to be much of a payback. So is it worthwhile and if so why.

Unfortunately I live in an area where dynos are about as rare as the Dodo and very expensive to use. I did not get a good dyno after doing the pulley mod, but I have dyno graphs for before and after exhaust mods, PCM remaps & meth injection. So far the result is very low to no power gains after each mod and after spending thousands of dollars.

I've had the pulley, tune, and a slight exhaust mod done, and I'm not sure there is much noticeable or usable gain. It's not thousands of dollars, though. Several of the tuner companies have run specials for well under a $1000 dollars, and the X pipe addition with the center resonator removal cost me $280 including the X pipe and installation. So, altogether I spent about $1100.00. The X pipe/resonator removal mod produces a great, subtle growl and was certainly worthwhile. The rest is more about ego.

Spent so far about $1k for all exhaust mods, $1k for meth injection, $1k for PCM map, $1k for dyno time, $300 for pulley and another $1k for various diagnostic tools.

I could never get traction in the 5.0 SC anyway so I have to say that unless new suspension and tyres helped with that first, I couldnt see any benefit from more power from the engine.

I did the x pipe as a mod (which I think did add a little power) but I did it for the noise, as the coupe is a little too quiet inside. The x pipe is a cheap mod for the difference it makes.

So the 5.0 L XKR gets 4.6 sec 0-60 while the XKR-S does it in 4.2 with 40 extra HP. What do the times look like for the tuner cars?

The 2008 4.2 XKR according to Motor Trend did 0-60 in 4.3 and 1/4 in 12.9 @ 110 mph.

With the current map it definitely feels a lot more power even if the dyno does not show it, I have a Quaife LSD, lowered & uprated springs, aggressive alignment and Michelin PSS tires so it sticks to the pavement quite well. I have not been to a strip yet as I have been waiting on a better tuned map.

Please excuse my interjection;

Michelin PiSS

Sorry, I was compelled.
Anyway, a BIG factor at any track is how well the first 60 feet are prepared and how warm the tires got during the DRY burnout. That can make a HUGE difference on times.

Same here , two dynos avalable in this town , and thay are not cheep to use .
And generally I'm at work working when these are avalable .
There are some really good smart phone/tablet apps which use the exelerometers to gauge G force , and gps to gauge distance and speed , you just add your curb weight and the app calculates the out come ,
I use dinolishous , it's clever , simple to use , consistent , cheep and always with you .
I have done Bosch 010 intercooler pump , 4liter intercooler coolant capacity increase , de gunked the charge cooler and TB , powerhouse 1.5 pulley ,
Manafold back 2.5" free flow exhaust with xpipe . 3" intake j pipe . K&N high flow pod with mina cold air box . (Also EGR bypass and PCV catch can no power gains here though)
I did do before and after 0-100kph times ,and quarter times , the before times and HP results were embarrassing . And showed my car was unhealthy .
7-8sec 0-100kph before , which would worsen considerably with repeated runs . From heat soak , supposed to be 5.4sec . Now 5.8sec.
My best quarter mile time before was 15.8 but mostly in the 16's (never really wanted to publish that) dinolishous said I started with 260rwhp so a lot missing .
At the time it was a stock unmolested nearly 2tonn car with 150000km .
Each and every mod made an improvement some more noticable than others,
Now runs 13.8' if I get it real right of the mark I've fluked a 13.4 and 13.6
Which is better than factory , and keeping in mind my car has 170000km on it ,
Dinolishous naw says I'm making 360rwhp , and I get two or three extra runs back to back before heat soak thanks to the IC pump and tank .
I can't help but think if the car was brand new with the mods I've done it may well be a considerable improvement over stock 400bhp . The car does feel great now as I'm sure jaguar intended , but all in all it sounds amazing and that alone was worth the $ in mods .
Exhaust was around $2k , mina box & K&N around $400 ,
Pulley was $300 , coolant tank and Bosch pump was $600
plus some coolant piping $100
J pipe and fittings was around $120. And the dinolishous app $12.
I'm hopeing for a tune via Cambo as well to complement the work done .
I'd truly be happy if I can reach 420bhp with high km's to Match the xkr's output from the same era , and much like Cambo I'd be thrilled to get this old jag in the late 12sec runs.

The XKR-S has different suspension as well. The suspension makes a massive difference, I'm convinced that my V6S F type is quicker than the XKR 5.0 was. Weight and transmission is part of it, but traction is the big difference.

Just looking at car reviews it has the V6 380HP F-type at 4.9 0-60

I posted this in the other thread, seems like the right place to post it again, given the subject matter.

I had a chat about this exhaust/cats subject, with my ex-JLR friend who writes tunes.

Here's what he said;

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⁠⁠⁠Exhaust backpressure is very important on the torque based PCM's, i.e. the 2006 onward models like an X150, since this parameter is used to calculate engine VE (volumetric efficiency).

So, put in an x-pipe or remove the cats (or install 200cell, 100cell, etc) and the fuelling would be off, because the VE of the engine no longer matches the stock parameters, resulting in high LTFT/STFT %'s.

This would limit the perfomance somewhat and/or cause some hesitation in certain RPM/load regions.

VE, in turn, is used in the torque calculation (driver demand, calculated indicated torque, which are compared to the estimated torque table in the PCM). In HEAVY cases SOMETIMES it may even trigger limp mode (been there, done that).
-------------------------------

And this makes perfect sense to me now, since we had the experience of flashing the factory XKR-S tune into a standard R and it did not make good power. Yet we have also flashed the stock XKR-S tune into other cars that were fitted with the XKR-S exhaust (with the x-pipe) and it made great power.

There are dozens and dozens of maps/tables and factors in the PCM of the X150, even things like the supercharger pulley ratio are in there and can (must) be modified. So with an X150, any mechanical changes you make to the car, be it exhaust/cats, pulley's, intakes, they have to be acommodated for in a custom tune.

Yes the PCM will adapt somewhat, but it won't be perfect, and in some cases I guess you could even go backwards, if the tune is not matching the mechanical changes.

I guess I would have to ask why Jaguar went with 2 different exhaust systems on the same model car. My XKR has the stock performance active exhaust (X-Pipe) with just a back box while other XKR systems have the twin resonators and the back box . So what is the difference in power/performance between the 2 systems and do they tune each car differently. Will an R-S tune with a PAE give you the 40 HP improvement ? Do the PAE cars have more HP or do the non-PAE cars have less HP

Lots of reasons I think. Cost, sound, performance, marketing purposes, etc...

Which is the same exhaust as the XKR-S.

The PAE system obviously flows better. Also the x-pipe has a positive effect in that it compensates for the firing order of the engine, where two adjacent cylinders on each bank fire in succession. By "joining" the exhaust pipes of both banks, the build up of back pressure from the two adjacent cylinders is minimised. The x-pipe helps to bring power in the upper rev range. I will have to check about the factory tunes, I never thought about this earlier...

Yes, absolutely. Actually it's a little bit more than 40hp.

I don't know of anyone who has done back-to-back dyno's to confirm this, the only dyno i've seen was an XKR that was retrofitted with the PAE exhaust and flashed with the XKR-S tune, but they did not make a run with the PAE exhaust and the stock tune, only with the stock XKR exhaust beforehand...

a 12 XKR with factory tune and pulley got a Spires stage 3 in UK and was dyno'd at 531 HP. an XKRS on the same day on same dyno got 550. Seems the added exhaust is a nice gain in HP and a tremendous gain in FUN! lol

Lothar,

First, nice to meet you. Not sure how to message you direct but I live in Cincy and just bought a 2012 XKR and would love to connect with you as I am doing the spires stage 3. I was interested in the pulley and tune but wanted to know if you got that done up in Columbus and had any recommendations, etc. Also would love to pick your brain about the car, things to look out for, check, etc, etc.

Appreciate it.

Christian

NO

It would be worth doing - mainly for others than the owner!

The cost of the upgrades is quite high yet people don't do before & after dynos. Odd.

As far as I know I'm the first n/a xk 4.2 to run a 13.72 so yes in my opinion a free-flowing exhaust and a specific ecu tune has dropped my et by .8 and increase trap speed by 6mph so mods definitely work.

So, the question is, do these modifications actually do anything? Well I guess it depends on where you spend your money.

I haven't put my XKR on the dyno, it's cheaper for me to go to the track for the night, and the last time a dyno sheet was posted on this forum some genius tried to pick it apart, and he was wrong.

And we can't race dynos anyhow.

So let's look at my XKR, have the mods been "worth it" ? The numbers speak for themselves.

Not long after I got the car, gave it a big service and put on new tyres, i went to the track.

Did 13.184 @ 106.68mph, 1.950 60ft

Then I realised the cats were choked, so I changed the cats, put on the straight through exhaust with x-pipe, had the tune corrected to compensate for these changes.

Did 12.943 @ 111.57mph with a 1.998 60ft

Then I got the tune re-worked to squeeze a bit more out of it.

Did 12.646 @ 113.97mph with a 1.975 60ft

So i'd say the whole exercise has been worthwhile, it's been a lot of fun too, and we're not finished yet, I haven't touched the pulleys, or the intercooler...

Without wanting to start a war, not a single "mainstream tuner" has been able to get even close to the results i've gotten so far with the 4.2L XKR. They can post all the dyno sheets in the world, it's not the same thing as rubber on the road.

Ultimately, yes, it could probably be argued that certain mods or tunes from certain companies are not worthwhile. On the other hand, here's my XKR...