A few months ago i installed a smaller Supercharger pulley (Jaguar XF Performance Supercharger Pulley for Jaguar NEW XKR) on my 09 XF ..
This week (after a few thousand miles) I got a check engine light which the dealer says is from a lean condition. So far, they have not found any vacuum leaks and i'm beginning to wonder if they may blame it on the supercharger pulley - is it possible/probable that the supercharger pulley could cause a lean condition ?

 

Higher boost levels do mean more fuel is needed when boosting. It's common for engine management to be reprogrammed to be able to provide more fuel and ignition map changes, and if the stock XF fuel mapping doesn't have programming to cover higher boost then yes, a lean condition could be caused. I'd be just as concerned about the ignition map being off, since higher boost increases the tendency to cause detonation, and if you're in California your gas is limited to 91 octane I believe...and not the best at preventing detonation.

Bruce

 

Just an upper pulley change doesn't bring you to the borders what the ecu/injectors can handle, so it is not the source of the issue.

 

Score: 1 yes, 1 no
Any tie breaker opinions ?

 

Maybe this helps; I speak from experience on our cars

 

Do European spec cars use 95 or 98 octane? North American cars must use our 91 octane which is European 95. I am not saying the pulley causes a lean situation but if it causes detonation the OBD II code may be interpreted as lean as that is the number one cause of detonation in an unmodified motor. Dealers over here sometimes just read the codes as OBD II generic codes rather than Jaguar specific codes especially if they only have one factory spec code reader.

With a smaller supercharger drive pulley you may, and probably are, touching or possibly exceeding the detonation limits of our gasoline, not of the ECU. Our gasoline can be very poor quality even if marked 91 and at sea level 91 can be marginal for highly boosted engines even if the gas is perfect. High ethanol fuels we use can change actual octane number while in the storage tank or if left too long in the car, low mileage for example.

I don't think it wise to assume the codes are incorrect in the sense that your engine is not running correctly and it may be due to the overboost capability of your modification. The way these mods usually work is by exploiting the margins for error left in by the manufacturer to accommodate manufacturing differences from engine to engine, for reliability purposes and occasionally so they can tune 'em up and charge extra themselves. We know Jaguar does this last on three levels now to these engines from the factory: supercharged, XFR and XKR S. Is the XFR S out yet?

 

@Jagular, Bruce,
Even at full boost, so open loop, you will stay within the marges with a mild upper pulley change.
The lean codes are set at closed loop (so part load, not WOT), another reason why it is not releated to the pulley change.

 

Well.. The car has been at the dealer now for 8 days. They have replaced some sort of fittings (brass?) and are now replacing all of the fuel-injectors, which apparently have to be shipped from England via Swallow.. And as we all know, a laden swallow cannot fly as fast as an unladen swallow..

..No mention of the Supercharger upper-pulley..

 

Another definite no!!!! Here
The biiger cause onthis engine is now lately becoming the oring behind that brass fitting for the brake booster pipe where it goes into the elbow before the SC under the throttle body. I just fixed 1 last week and we have been doing alot this year, and a suck **** job too.

 

There you go. The code is likely correct and pointing to an actual air leak which will be a warranty covered defect. It should be a simple matter for Brutal's idea to be checked and either fixed or eliminated as a possible cause.

 

Got the XF back after 11 days at the dealer. They replaced those brass fittings which apparently require that the engine be lifted from the car so they can get to them, and they put in all new fuel-injectors.

The Service Manager did mention that it is POSSIBLE that my performance exhaust and the K&N filters MAY have contributed to the lean-codes by allowing a small %% of more air into the system, but he reiterated that it in no way had anything to do with the failure of the fittings or fuel-injectors. he thinks it just may have made the codes show a bit sooner. Never said anything about the upper supercharger pulley...

 

Have you checked the air filters? Are they stock ? Are they seated correctly?
Here is an example. I put dual K&N filters in my AMG and after some time I was getting lean codes. I looked for leaks week after week. The dealer said it needed a manifold and it had to be leaking there. That was not the case. I put back the stock filters and made sure the airboxes were seated properly and the lean codes never came back.The codes were : system to lean bank1 and sometimes bank2.
I also hear the JAgs have this same issue with filters?