MPG What to Expect

[J44EAG]

Robs comments about EDT and also those expressed by Paul when we last met (PTJS1) have peaked my interest greatly.

As said previously, I`ve had the Terraclean process carried out on my XJR around 10k miles ago. That took care of the fuel system and also released a fair amount of combustion chamber gunk which has continued to be absorbed by the engine oil. In addition to that, I installed a methanol/water system which has again increased the flushing effect. I`ve increased my oil change regime which to date has always included use of Wynns Engine Cleaner during oil changes which now figure every 5-6k miles. Good as that is, I`d still like to further improve oil quality control. Having carried out an oil change, I`ll often cut open the used filter having first punched a small hole in it to drain out the remains of the old oil. Cutting the filter open often then reveals a quantity of rather more viscous and treacle like goo. That is disconcerting to say the least. Yes, its trapped in the filter but I rather not see it there at all.

EDT offers the opportunity to have the engine oil thoroughly flushed out with contaminate being grabbed by an external filter during the process. Fitting a new engine filter and fresh engine oil gets the engine internals back to an as new condition. Further use of the car obviously restarts the potential for sludging again, but that is to be expected and perhaps dealt with again at a later date. I can only see this process as being highly desirable.

My local EDT depot is at Bexley Heath on the A2 west of Dartford. Presently, at my current location, that is around a twenty minute drive me along the eastern section of the M25. Time to get the existing oil nice and hot in preparation for the EDT treatment. BM Sport at Lion Road, Bexley Heath are the local franchise holders for the process. Phone 020 8304 9797. They appear closed over this post Christmas period but I`ll be making a booking for J44 as soon as they are open again in the New Year. I`ll try and get photographs and material for a magazine article when I take the car over to them probably the week after next.

Seems a good idea, eh?

Mike

[Manbearpig]

A Jag Indy will have IDS/SDD dealer level gear to diagnose the car to a greater depth than is possible with either the Torque app or indeed our favourite iCarsoft 930i units many of us here use. He should have no problem itemising whether you have a cat or Lambda issue or a combination of both.

Although I'm a newby owner the Indy inspires confidence and is booked for weeks ahead solid which I take as a good sign. He diagnosed the faults for free and was not chasing work, so if he says both cats are out I'll go alomng with that for now on faith, I'm just gobsmacked at 2 Cats goind simulatneously unless of coutrse it has been run on one failed for some time by the feckless PO and the other just joined in, the reason for the trade in I expect.

Regarding MPG I'm bringing forward the service and spending my Christmas money on a K&N on the basis it can't hurt! Son goes back to uni in a few days which will be a nice long cruise to see what a motorway only figure will be.

[J44EAG]

I`ll put my money on a dicky Lambda sensor before a cat failure. I`d be asking the Indy to look closely at Lambda performance before buying cats.

If cats are needed, get a quote from Longlife Exhaust or similar local exhaust specialist. They will be rather less costly than buying OE cats. You could de-restrict the exhaust at the same time by fitting sports cats. Got two fitted myself in the old cat cases by Longlife.

Mike

[J44EAG]

A bit more on XJR economy.

A trip down from Swanley in Kent on the M25 this evening to the Caterham/Godstone in Surrey junction in moderate traffic at between 60-70mph shows fuel consumption as 33.3mpg. Quite pleased with that as the fuel consumption has improved by about 3mpg when compared to when the car was OE ex-factory spec. I put this down to cleaned injectors, a fair amount of internal carbon removal by the water methanol system, probably a very slight improvement in compression and a de-restricted inlet and exhaust system.

PTJS 1 and I have my XJR and Pauls XJS booked in at Ashford on Monday 5th February to receive EDT oil decontamination treatments. I`ll again record MPG down to Ashford before cleaning and MPG achieved on the return trip. We both have loads of Wynns Engine Flush and appropriate 5w30 fully synthetic and part synthetics oils in boxes in our boots which will be used before and after the EDT treatment. Greatly looking forward to the cleaning sessions and being able to see how much gunk might be removed from our engines.

More on the EDT after it occurs. Probably in a new thread.

Mike

[irishjag]

Some more on my 2003 XJR MPG as a comparison
Had a 240 mile run to Cork and back today.
Drove like a nun.
Not motorway but the equivalent of A roads in the UK, with a few climbs and falls into and out of the coastal towns on the way. Between 60 and 70 mph apart from a bit of 35 mph though the towns on the way.
Zeroed the trip computer before I started and achieved 24.8 mpg when I arrived home.
I honestly could not envisage how I could get this up to over 30.
??

[J44EAG]

MPG plummets dramatically as soon as you get to drive up hill and down dale with lots of stops and starts. Lots of throttle opening and closing, acceleration through the gears and sixth over drive gear not happening until about 50mph has been achieved ruins a fuel use curve.

Remember my 33mpg achieved for the first time ever was on the M25 around the eastern quarter around London. I was able to travel in sixth gear at a gentle 60-70 using minimal throttle and keeping speed as even as I could. I was in cruise mode and there was no point in trying to bludgeon my way down the outside lane. So I just quietly let the car run at the general speed of the traffic.

Coming off the M25 right at the southern most junction for Caterham, my mpg deteriorated as I sat at two sets of traffic lights on the roundabout under the motorway. I had to do another start from stationary and immediately climb a steep section of the A22 up towards the North Downs passing Caterham towards the old Battle of Britain Kenley fighter station. A very steep climb up a B -road using low gears and lots of throttle followed as I headed for my current home at Warlingham towards Biggin Hill. That five mile hike from the motorway to Warlingham caused my fuel consumption to drop to 26mpg for that part of the trip.

In local driving with cold starts and short journeys, I can watch fuel being consumed at a rate of 17mpg.

These cars are really designed for optimum performance and economy achieved on the motorway at around 56mph. Use of the full performance will cause the XJR to guzzle fuel at a great rate! My blasts up Test Hill at Brooklands last summer saw me achieve my lowest mpg ever. An eye watering 9mpg plus use of water/methanol cocktail!!

My car runs about a 10% extra boost potential over and above a standard car in all situations. Around 2.5 extra PSI are produced by the smaller charger pulley and supercharger ease of breathing due to radical porting and polishing go hand in hand with the faster flowing sports cats and the modified ecu. Inlet and exhaust "blockages" have been greatly reduced and the result is a less strangled situation. Power and torque are rather higher than an unmodified car which means grunt is produced more easily by the engine but without constant throttle pedal inputs which can cause injectors to pulse more and inject more fuel to create the action. Not having to work the car so hard on the loud pedal transmits as fuel savings. The big Bosch inter-cooler pump also add greatly to the increased torque of the car even around town. What has occurred during my development journey has been to maximise torque production potential and get that charger working sooner and rather further down the power curve.

When I first owned the car, I did a trip on the A3 from Portsmouth to Putney, south of London. I achieved 31mpg at similar speeds of today. To achieve that I really had togo easy on the throttle. Today, I didn`t really have to do that. The car bowled along on a wiff of throttle with the cruise control doing most of the thinking. Cruise control also saves fuel and is vastly more intelligent in application than me!

[irishjag]

Thanks Mike, as ever a very comprehensive reply.
So following the trip yesterday I filled the tank this morning and noted the trip computer which was zeroed when I filled the day before.
So I'd traveled 266.3 miles and added 42.25 liters to top off the tank.
I make that 9.51 UK gallons
This gives an mpg of 266.3/9.51 which is 28 mpg. This seems to more where my fuel consumption should be based on peoples comments.
The trip computer showed 24.7 mpg after the 266.3 miles.
So there appears to be a big discrepancy between the trip mpg and that calculated based on the amount of fuel going into the tank.
I wonder if this has anything to do with my crazy fuel gauge? (See post on fuel system forum section)

[J44EAG]

I think probably, not, Chris.

In my experience with the Jags I have owned, odometers and speedo instruments always over read. In other words miles recorded always accumulate faster than a point to point GPS says is the case. Similarly, the speedo always reads faster speeds than are actually the case. It is the same on my current XJR. My 33.3mpg is probable more like a true figure of 30mpg. By the same token an odometer showing 100k miles in truth is likely to be more like 95k covered.

Mike

[Manbearpig]

How did you clean your injectors, insitu or on a balancing rig?

[J44EAG]

Injectors cleaned in situe without any dismantling by Terraclean. The second can on the service machine helped removal of combustion chamber gunk. It made a big difference on standing start and willingness of the car to progress more easily in town. On the open road, it felt as if I was softer on the throttle. The cost was around £150 which compares well to paying someone to remove the injectors, clean on a rig and then replace. Terraclean is a lot less bovver!

Mike

[EDTAUTOMOTIVELTD]

Chris,

Glad to have been of help. Cataclean really does work well.

Mike

we have had real world reports of up to 26% fuel savings after an EDT deep engine clean !! removal of all contaminates down to 1 micron works
wonders.
David H
CEO EDT Automotive ltd

[J44EAG]

Thanks to David for that.

I shall be meeting up with David together with Paul Sinnott to have my XJR and Paul`s XJS given the EDT treatment on the 5th February 2018 in Ashford, Kent. In preparation for the event, I`ve been adding Liqui Moly fuel injector cleaner to the fuel tank for the last couple of weeks or so. I`ve also recently run with Oxy Cat in the fuel to really get the cats as clean as I can after I experienced a near side, rear Lambda sensor failure. The upper Lambda sensor was removed a couple of weeks ago just to ensure it wasn`t caked solid with carbon due to a touch of over-fuelling caused by the failing rear sensor. It was certainly a bit mucky so received a good clean up.

The XJR will be presented to David with mileage around 93,400 miles, with the last oil and filter change taking place around 2,500 miles earlier. Once at Ashford for the treatment, I`ll be adding a can of my Wynns Engine Flush additive to get as much gunk out of the sump as possible by manual means before the treatment. So the EDT challenge is to see just how much more gunk can then be extracted by Davids` machine. It`s going to be a most interesting morning.

Current fuel mpg currently stands at 33.4 mpg at between 60-70mph on the M25 between Swanley and Caterham recently.

Today the car again did quite well. Warlingham near Caterham, M25 to Leatherhead, Chessington, slow traffic through town to Surbiton on the A3, then A3 to Putney. Back down the A3 to the Wisley turn on the M25, then onto the M23 to Brighton. Return from Brighton, slow traffic in town to the M 25 Crawley/East Grinstead turn, B roads via Outwood to Bletchingly on the A25, north up the A23 back to Warlingham. 28.6mpg at 70 on the motorways and rather slower on the A and B roads. Not bad at all, in my opinion considering the throttle is pumped more heavily in this A and B road type use.

Mileage will again be recorded for the run to Ashford next week and again for the return trip in what I hope will be similar driving conditions. I`m looking forward to seeing if mpg improves after the EDT flush.

My eldest daughter was well impressed by the XJR. She commented on its ride quality, seat comfort, and lack of noise together with its ability to get a move on when required. It certainly gobbles the miles without effort and bearing in mind its size, large capacity engine and not insignificant profile, achieves pretty respectable mpg on longer runs. Around town and in stop/start conditions, that`s when economy starts to deteriorate. What else do we expect?

Mike