The results are in! (see attached if you don’t want to read the waffle below)

To recap, a catalyst failed on my ’07 XKR after I had spent the day thrashing around a race track which meant my check engine light was permanently on with code P0430 present. As it was just before Xmas and I expected to be using the car a lot over the Xmas break my mechanic suggested cutting both catalysts out and putting straight through pipes in their place. The car was unfortunately almost unusable after that because of how loud the exhaust became so I had to drive around with the exhaust valves in the rear silencer wired shut for a few weeks.

After the Xmas break we returned to the exhaust shop and came up with a solution that involved removing the mid exhaust dual resonators and replacing them with 4 custom ones plus an H pipe. This made the car quieter and more driveable with fuse 19 back in although it was still quite raucous under full throttle once the valves had opened.

While researching what to do about replacing my catalysts I had noticed that Cambo had made comments on a few threads about flashing the car with a tune that disabled the catalyst monitoring which would get rid of the check engine light. As my car also has a smaller supercharger pulley fitted and now less back pressure I was keen to get it tuned anyway to take advantage of that and he agreed to create a custom tune with the aid of his tuning guru.

When he sent the tune file through he mentioned that as part of their standard tune they adjust the exhaust valve opening profile so that they open earlier. I wasn’t aware that was possible but as I already found my new exhaust exhaust too loud at high revs asked if it could be modified to close above 1100 revs and stay closed at full throttle. That was turned around in a matter of hours and now that it has been applied makes the car a lot more pleasant to drive around town. I have also fitted a switch across fuse 19 so that I can cruise in hooligan mode if the mood takes and the rest of the time treat it as a bit of a sleeper.

The attached dyno graph shows the before and after results and while the car was on the dyno I got them to do a few runs with the exhaust valves permanently open as my butt dyno felt that there was more power with the valves closed and I was also able to get better 0-60 times with the valves closed as well. As you can see from the graph it turns out that I was wrong because there is slightly more power at the top end with the valves open so I suspect the issue with the 0-60 times was just traction and variations in the slope of the road and I only had a few attempts with the valves open anyway due to the excessive noise.

There have been some good gains mid-range and the car pulls like a train now. I don't know that I would want to put much more power through it as I can feel the rear end scrabbling for grip now, particularly under full throttle in the 70km/h to silly speeds range. I suspect it will also be a bit of a handful in the wet if I am not careful.

All in all I am very pleased with the tune and found Cambo and his tuning guru to be very responsive to my needs as they ended up producing 4 different tune files for me in the end so that we could get the car just right. They are able to tweak a lot of different parameters in the PCM including supercharger pulley sizing, exhaust back pressure, stopping the traction control cutting engine power, changing the cut in temperature and speed of the engine electric fan to aid cooling, removing various torque limits and a lot of things I don’t really understand!

I hope to get back to the drag strip in the next few months to see if there has been any improvement to the standing quarter times or terminal speed.

 

It'll be interesting to see how it translate to your trap times.

 

Someone somewhere is pulling a sneaky.......
Horsepower and Torque have the exact same value at 5252 RPM, no matter what. It's mathematically and physically impossible to NOT match at 5252 due to the way both are figured. If a dyno sheet shows otherwise, it is not correct.

 

Yes, an excellent point!

 

It's a chassis dyno, not an engine dyno, the numbers on the sheet are Newton Metres at the rear wheels which is after all the multipliers and losses of the torque converter, transmission (ZF has 1.143:1 4th gear), the diff, the wheels, etc...

Have a look here

http://www.mainlinedyno.com.au/image..._THE_TRUTH.pdf

"Now something to remember, the Motive Force or Torque
trace, has the exact same shape curve when compared on a similar Graph Scale. Also, the Derived Torque shape will be the same shape as Roller torque for a manual car, but can be quite different and more “manual” car looking for an Automatic car.
Another benefit of displaying Derived Torque, that is you are a Horsepower and Foot Pounds of Torque junky, instead of kW and Nm, the Derived Torque and Horsepower will cross at 5252rpm, (just like it does on an Engine Dyno).
Below are a couple of Graphs showing the differing ways in which Torque/Derived & Torque/Motive is displayed on a Mainline DynoLog Dynamometer.
These examples are the exact same runs, but showing the different displays of Power...."

So he didn't display the Derived Torque... big deal... the difference between the runs is what counts, not the outright numbers.

 

So didn't see the weird units. Dang non-American "english".
Mine, from my Street/Strip...

 

The curves cross at 5252rpm if and only if it is units of hp and ft-lb, the axis are the same scale and type (i.e. both @ wheels or both @ flywheel estimate)

If units are mixed then they will cross at a different rpm, or not cross at all if the range of the graph is not equal.

Also some dynos give wheel torque but its not true derived torque its roller torque (the roller spins at different rpm to wheels unless they are by chance the same diameter) so there are all sorts of things that are then open to misinterpretation.

So thanks for taking a dump on this thread, and the results. This is pretty much why nobody shares their experiences anymore, too many experts heckling from the sideline.

 

I had real issues with traction off the line the last time I tried and my tyres are 3 years more worn now. The car didn't have the smaller supercharger pulley then either and I have seen others find their terminal speed lower after fitting those so I am not expecting great things but it will be interesting to see regardless.

 

This.

Great to see somebody actually doing something with their car! I noticed the stock ECU runs pretty rich. Probably for protection. I wonder how much is to be gained just with leaning it out. I picked up 22hp on a 2.0 turbo motor when I got the AFR's from 9.5 to 11.5. Still well within safe levels.

I'd love to see the two maps side by side to see what parameters were changed and by how much.

Has anyone ever used a Buhtt Dyno? Accurate results by simply comparing the size of the graphs. I'd post my results from my first XKR drive but you wouldn't want to see the print out.

 

Going to a dyno tomorrow and possibly do a custom tune while at it .. Will be interesting to compare the results

 

Not a tuner in world would open his book like that

But to give you a rundown of what is changed in the tune;

Supercharger pulley ratio (to compensate for different pulley combinations)
Exhaust backpressure value (for different exhaust set ups, with/without cats, x-pipe, etc)
(both the pulley ratio and exhaust backpressure are used for the Volumetric Efficiency calculation in the ECU, how it calculates torque)

Closed loop fuel map (normal fuel delivery, part load)
Open loop AFR target & WOT enrichment (the AFR at full throttle)

Closed loop spark advance (normal spark advance, part load)
Open loop spark advance (at full throttle)
IAT2 spark retardation (how much timing is pulled due to air temps out of the chargecooler)

Traction control torque request (the traction control won't close the throttle, only works the rear brakes instead)
Engine maximum torque limit (won't close the throttle because of too much torque produced)
TCM torque reduction request (less of a pause during shifts because of the throttle closing less)

Altered throttle map (that you actually get full throttle when the pedal is to the floor)
Maximum manifold pressure (won't pull back the throttle because of too much boost)
Active exhaust opening/closing table (change when the valves open/close)
Raditator fan lower limits raised (fan starts earlier and spins faster to help cooling of the intercooler circuit)

There's probably something else i've forgotten... but that's the major stuff.

 

Here are my disappointing tune results from the dyno https://www.jaguarforums.com/forum/x...3/#post1633603

 

I am not surprised one little bit , after my mail order tune I felt no improvement at all so I took it to my tuner who put a custom tune through it where we managed to gain 25whp and reduce my e.t by .5

 

Yes seems like it. Shocker that it is such a reputable company too.

 

Wow, that's worse than I expected...

Well my offer still stands to get the tune in your car, just need to get it organised with the dealer guys...

 

Pending on how the dyno was done, you will have variations in results, so just 2 pulls isn't representative and for correct interpretation more info is required.

One (of many actually) underestimated variable is the coolant temp for the intercoolers. The higher this temperature which is measured by the iat#2 sensor after the intercooler, the more ignition retard by the ECU. The intercooler circuit will not just be heated from high power runs but also via residual engine heat after you have turned off the engine.

Check it yourself, you can put your hands on the intercooler directly after a drive, but after about 15 minutes or so with the engine turned off they will be hot!

To get better comparable dyno results I always have the car run on the dyno for a while (with a good fan in front) and turn the airco on as that will turn on the engine cooling fans which helps quickly in bringing the intercooler temps down to just above ambient, or at least has the same temps (can easily be checked with heat ir guns) as previous runs.

Anyway, a more comprehensive tune, so more than just ignition advance will deliver more hp of course, however with just the ignition advance on earlier models should have given already about 15 rwhp (still not really noticeable of course).

 

This is the kind of thing that is most valuable for a DIY owner like myself. The experience of doing a temperature check by hand seems to have multiple uses. For Example, if the intercooler radiator fluid pump has failed, it might never get hot.

Thanks!!

 

Well, actually the intercoolers will get hot if the pump has failed as they are not cooled anymore, at most they should feel warm. A simple way to check if there is flow is to close a intercooler tube with our fingers, you will instantly feel if there is flow.

 

And on the later cars if it's failed you can get (hope for) a P2601. (I suspect not on the earlier cars.)

 

I managed to get back to the drag strip today. My last outing was around three years ago when the car was stock and my best standing quarter time was 13.501 and the best terminal speed was 109.89.

Today I had a best standing quarter of 13.132 and the best terminal speed was 113.19 so a combination of smaller supercharger pulley, no cats and a tune from Cambo seems to have made a reasonable difference.

Traction was the biggest issue again so with an LSD and/or a bit of practice I would hope to break in to the 12's.