How can I check to see if supercharger on 2006 4.2L XKR is working? If wish to hook up a mechanical boost gauge what exact line would I install a "T" in and where to hook up power for the gauge illumination? Pictures would be of great help as word in other posts have not been specific enough. I have used a Foxwell scan tool which tells in MAP (Manifold air pressure) but I do not know how this will relate to supercharger boost pressure.. No check engine light is on .Question arose as the acceleration seems less than would expect with 390HP but I have no reference point t know if this is "normal." Thank you.

 

One thing to consider ; the XKR is a heavy GT car, not a sports car like a much lighter Porsche. The XKR is good for high speed cruising, where it eats up the miles, less good at sports car acceleration and handling.


z.

 

Oct 20, 2024
Thank you Zray for taking time to respond. . I realize the XKR is heavy which can affect acceleration. Quoted 0-60 time howerver is in mid 5sec range I believe which should feel fast.. Do you have any more direct answer to my question specifically the supercharger? Thank you.

 

Hi audiodoc,

It is unlikely that your supercharger is "not working." It could be underperforming due to wear or pressure leaks. The supercharger outputs connect directly to the intake manifolds, so off the top of my head, there is not a convenient port where you could connect a boost gauge. But the MAP sensor readings should give you a good idea of what is going on. Here's a generic chart showing approximate MAP sensor readings for normally-aspirated and forced-induction engines. Note that if the supercharger was producing no boost, the readings would look like those for a normally-aspirated engine, and the MAP signal would remain at or below 0 psi even at high rpm.



It is quite possible that your engine needs a good tune-up, which would include new correct spark plugs, a new air filter, cleaning the MAFS, running a good fuel injector cleaner such as Techron Concentrate Plus through the tank (follow the instructions on the bottle), checking the accessory and supercharger drive belts, gently cleaning the throttle body taking care not to get cleaning fluid in the motor/position sensor, etc.

With the Foxwell, check your fuel trims to see if they are significantly rich or lean. Rich trims might suggest leaking fuel injectors, a stuck-open coolant thermostat or faulty coolant temperature sensor, etc. Lean trims often indicate unmetered air leaks or low fuel pressure.

It can also help to service the transmission with all new correct fluid (Ford Motorcraft Mercon SP or ZF Lifeguard 6), a new pan/filter (ZF/Filtran), new valve body bridge seal and tubular seals and electrical connector sleeve, setting the fluid level correctly at 40ºC per the ZF procedure. When your car was new, Jaguar and ZF claimed the transmission was "sealed for life," but ZF subsequently revised its claims and now recommends the fluid be changed every 80,000 to 120,000 km / 50,000 to 75,000 miles.

Also, do you keep the transmission in Sport Mode? And are your tires properly inflated?

Cheers,

Don

 

that sounds optimistic.

I wouldn’t put any credence in Auto Magazine test numbers. Those were / are routinely “adjusted” to match the manufacturer’s advertising revenue.

One very simple thing to try that does impact acceleration “feel” is the throttle cable adjustment . Often there is too much slack. When the throttle is all the way down the sensor should show 100%.

Z

 

Oct 20, 2024
Dear Don B.
Thank you for your detailed and very informative response. Since placing post , I took a drive and had passenger monitor live data on Foxwell scan tool. MAP went from 23-30 kPa to 80's when rpm over 2200 or so . This suggests boost is occurring and if convert kPa to PSI (about 6.9 to 1 ratio) is close to what graph you showed for boosted engine.
Re maintenance MAF and MAP both were cleaned as was throttle body using special cleaner for that purpose . Transmission fluid changed with ZF filter and Type 6 transmission fluid by professional. Air filter is K&N and is clean in a stock air box. Short term fuel trim Bank 1: zero, Bank 2: minus -1 Long term Bank 1: 13, Bank 2: 13%. Measured at idle in park. Spark plugs not changed yet but is on the agenda.. Mileage 61,000. Tire pressure checked.

Thank you very much Don for your detailed efforts to help.
Audiodoc

 

You've done lots of the right things.

Regarding the K&N filter, if it is the type that is oiled, there have been cases of the oil contaminating the MAFS. A dirty MAFS can cause the ECM to erroneously apply excess fueling, and your positive 13% LTFTs could be a clue that this has happened. K&N claims this doesn't happen, but there are lots and lots of owner accounts of it happening. What does the Foxwell show your MAFS is reading at idle? Is it around 5 grams-per-second? When you increase engine rpm, does the MAFS signal rise accordingly?

The next time you have the transmission serviced, don't neglect the valve body bridge seal and tubular seals. On every 6HP transmission I have serviced these seals have been hardened and compressed, which leads to suboptimal transmission performance and sometimes shifting problems.

The correct spark plugs are probably NGK IFR5N10 / 7866 Laser Iridiums. We find that Jaguars tend to run best on the OE plugs.

Cheers,

Don

 

Definitely try a regular paper filter and see if that and a MAF cleaning changes anything . At the same time do a hard reset of the electrical system and that will give you a reasonable baseline to use. The hard reset costs zero and a paper filter will only set you back $15 to $20 . Well worth it .

i was around when K&N filters were first introduced (in motor cycle racing). They were a godsend for dirt track racing. But their shortcomings became very obvious, glaringly so, when their marketing fixed upon the automotive market and cars began to have fuel injection and electronic ignition systems.

You will do yourself and the car a favor by using a paper filter.

Z

 

Oct 20, 2024
Thank you Don and Zray:
MAF flow is 5 g at idle and rises to 13g as rev to 2500 rpm or so. Spark plugs purchased but not installed are NGK Iridium.
Should I do a fuel injector treatment based on the 13% LTfuel trim on one bank and 10% on the other?
I do not know if K&N filter is an actual problem in my case but I will change to paper on your recommendation. Thank you.
Audiodoc

 

I've never measured my car but my XKR feels pretty quick when at full throttle. It does best once you are already up to speed because the rear end doesn't struggle so much. Even with very good modern rubber the rear end will loose traction very easily. From 40-155mph the car should just pull no problem. It doesn't take very long at all to get to 130mph. Might be a good idea to check the intercooler pump and make sure it actually has coolant in it. Might also want to make sure the supercharger oil has been changed. There is also a bypass solenoid hatch in the bottom of the air box which opens at full throttle, that might not be working? Although I'm not sure how much power you gain from that anyway.