A few days ago I installed a 1.5lb pulley and while I am seeing significantly increased acceleration, I am also now seeing MPG at around 13 versus about 19MPG prior to the install, even while driving like a little old lady on Sundays.

Any ideas?

 

Have you had the ECU tune done? I seem to recall you saying you'd been told it would over-fuel if the map wasn't changed. And if it has been changed, then it's probably optimised for performance, not frugality. Check if the pipes are black after a freeway run.

 

Haven't done the tune yet, just anxious to drive the car with the pulley. I know many here have done it but I did not think everyone had done a tune and was curious to see if others would comment on their experiences.

 

In that case, I'd guess you're running rich and your pipes have a nice black carbon coating.

 

I ran without a pulley and fake(read none) tune for four months and my fuel mileage sucked. It was in the 12-13 range. Keep in mind what its actually doing without a tune is spooling up to the maximum boost the stock tune allows which is 9LBS. So its using more fuel at lower RPMs as there is more air available sooner and the ECM is trying to keep the Air Fuel ratio within an acceptable range.

 

I am about to have my pulley mod done on 4.2 s/c. xkr. Not having the ecu tune done at this point. But may if the fuelling is off. I will have a before and after dyno done to see what's going on.

 

I was at around 19 city, 20s freeway before the pulley.

How long did you run with the pulley before getting the "real" tune from eurocharged?

Other than low mpg, any issues with running too rich? Fouled plugs, too much carbon build up?

 

Lets see I got the pulley in November I believe. I had no problems at all other then the car slowing down above 4k RPM as the boost limiter started to close the throttle body.

 

A few of the pulley sellers claim no tune is necessary (they probably mean gains will be had with the new pulley regardless of a tune) and don't warn of the increased richness of the AFR or indicate any dangers associated with an overly rich mix as indicated to me by Eurocharged. So other than some carbon on the tips and decreased MPG, is there anything wrong with running rich?

 

Just overall carbon buildup and decreased fuel mileage. I ran this way for months and had no ill effects.

 

My combined MPG at this time is 14.1. If you were averaging 19 MPG in the city, that is absolutely amazing.

Is there a chance you made a mistake? I think actual combined city and highway for the XKR is going to be around 13.5 to 16 MPG, depending on how heavy your foot is. The rating for the car is only 15 city / 22 hwy.

 

I did the pulley on the xjr and did not experience this. Following the change, I purposely disconnected the battery, and purposely 'decharged' the electrics (touching the negative lead to the positive terminal.) This allows the car to relearn appropriate driving patterns and tuning.

Incidentally, I didn't notice a significant improvement on road performance so I haven't bothered with the pulley upgrade on the xkr.

Cheers!

 

You absolutely have to have a tune as the stock pulley is capable of 9.5LBS but will get quickly cut back to a max of 9LBS. With a tune you will see 11LBS of max boost and a power curve that doesn't fall off over 5k.

Look at my pre and post dyno results, they are both with the same pulley.

 

19MPG was before the pulley. Even my supercharged XJ would get mid 20s MPG on the freeway.

After the pulley it is undeniably running richer. I don't care about consumption (it's not a daily driver of course) just concerned about screwing something up until I can get to do the tune.

 

I did not reset anything, but the pulley on this car has made a HUGE difference IMHO. I have not taken it to the freeway yet but have driven on some nice open stretches of road with little traffic and the difference is obvious in the low to mid range RPM.

I imagine after the tune it will be amazing.

 

The AFR readings are definitely too fat, without the tune. dialing that back nearer the high 12s, low 13s should greatly improve your response and fuel mileage.

 

This is how I felt after the pulley swap and faux tune. The car felt very strong down low as it should have but up top it was the same... Its just that when you already have 510HP of course it feel fast. When you get the tune look out!

 

There I was, thinking "OK, my 13 mpg around London is not too bad". Then I realised: my gallons are 20% bigger...

 

Just did my first freeway run, over 200 miles to Orlando and back and got 22MPG with aggressive pedal use. But still getting between 11 & 13MPG around town.

 

My 2013 XKR ,

I have the upgraded exhaust package (from dealer) , and i have put K&N filters, 1.5lb pulley, with the tune at the same time from ETG tunning group

ECU Tuning Group these guys

( so don't know the without tune vs with for the pulley )

my combined mpg sits around 18.5-19.5 and i do push it pretty hard,

I`ve seen it hit 26-28 on the freeway doing 70 mph with cruse on

never use D i am always on dynamic mode with S and use the paddles

i`m in utah, about 4200 FT elevation and it gets hot in summer, not sure how much hat effects the mpg

but overall i am really impressed with the MPG on this beast 13mpg seams

way off , running to rich.. possible as others have mentioned , if your

getting combined under 15-16 something is not right unless your doing a track day


-Tomspitfire