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[Willinot]

I currently run a 2002 WJ 2.7crd and get between 25-30mpg avg.

I was considering fitting a tuning box to improve the mpg a bit as the above figure requires some very careful driving.

Also looking at re-maps but would prefer the box if good one is available.

Really just looking for opinions, experiences and recommendations.

Also,  my jeep has 114k on the clock and is well maintained, are there any problems with adding such a mod with this milage.

All help and advice appreciated.

Thanks.

Paul.

[isle of man]

Paul,

Do the sums it will take you a coon's age to recover the cost!!!

[tim_aka_tim]

Read this http://www.birtydastards.com/frm/index.php?topic=11080.0
Then be happy you have a working engine. You have a heavy 4 wheel drive vehicle.
It's never going to get very good mpg, diesel or petrol.

[Dutch]

between 25-30mpg avg.
the above figure requires some very careful driving.

Tell me about it !!!.....velvet right foot comes to mind.   Aha...top tip last night on Top Gear.....NEVER BRAKE....

[Willinot]

Thanks guys,

Appreciate the informative prompt replies.

Some good advice and the post was interesting reading.  Think I'll stick with the velvet foot and minimal braking method.  

You mentioned to be glad it's working engine, are these generally regarded as being a fairly reliable or like my other 4x4 (freelander) service bill waiting to happen , as I've only just bought it and not scared to get the hands dirty if there is any preventative work I should look at doing or checking.

Does anyone publish a manual for them as I've only managed to find the petrol versions so far?

[Willinot]

Does anyone know the optimal crusing speed for mpg.

So far I found the following from driving. (speeds based on the speedo so may vary slightly)
At steady 35mph it changes up to 4th and remains.
At steady 45mph it changes up to 5th and remains.

Realise it's never gonna out preform a puris and love driving it but just want to try and get the best mpg out of it when not indulging in the growl and grunt of kick down........ Oh how I love that noise.
 

Paul.

[Dutch]

Paul,

I've got the identical sistership to yours with 112K on the clock.
Bought from a trader in Torquay 4 years ago @ 75K.
The truck is maintained at a general garage up the road (non-Jeep) and goes in for a once-over and MOT every March.

Only issues I've had :
- gearbox needed a software update to sort Jeep/Merc data communication. Yeah the yanks stopped talking to ze Germans    or the other way round.  (£35,- at dealer)
- At 105K nbr 5 injector washer started leaking. Yep the one you cannot get at.  Drop engine and had them all done.
It is a known glitch on the merc engine, and so far I heard from two other owners that they had the same issue at the same mileage.  (£450,- ish.)
- rear brake light switch fubar 2 months ago.

Last week-end I did a round trip from Kernow to Southampton via IOW and back to Kernow. Plenty of time so did not stress out about it. Kept it just under 2500 revs on the motorway which is 73 Mph.  Town driving in Soton and IOW and B-roads until you hit the A303 again at Honiton.   You're right that at 45/48 you hit 5th and with a velvet foot it stays there with 1400/1500 revs on the clock.  (the feckers that sit at 41 Mph piss me off because you just cant get it to go into 5th).

Got back to Kernow with 440 miles on the clock and fuel had not hit reserve yet (but close) so put 65 ltrs in to fill up.  So 14.29 Gall. = 30.79 MPG.  (while the trip comp. said 28.5 so this is a bit pessimistic)

I would imagine that if you sit in the inside lane @ 60 your tank of fuel would last you a bit longer but what is the point of going nowhere fast and looking like a plonker 

This is with 4 people in the car and the Mrs. does not do travelling light.

Compare this to bombing down to Folkestone in 4.5 hours @ 80/85 and this would show 28.5 Mpg

Around town/commuting locally I cannot make a tank of fuel last more than 350'ish (25 Mpg)


The moral of the story is : It is a fantastic tourer and at destination after 400 or more miles you jump out of the armchair feeling non the worse for the trip.  (oh.....and apparently it is not too bad off road either )
 

[tim_aka_tim]

You mentioned to be glad it's working engine, are these generally regarded as being a fairly reliable or like my other 4x4 (freelander) service bill waiting to happen ,

No, no. I worded my response badly. The 2.7 is a fine engine, and you should expect no trouble (just
don't chip it). Seen a few horror stories with the gearbox, which is treated as a sealed unit, but they're few
and far between.

[Dave69]

for fuel economy get a cheap small petrol car as a work hack

[Tank]

Tuning boxes are a waste of money,yes they seem to work as the car seems faster etc but all they normally do is overfuel and end up fooking the injectors up.Had one on the BMW and it seemed to make a difference,until i spoke to a guy about it all and he said avoid them because of the injectors,then later found that  low and behold one of my injectors is down,advice came too late

[Willinot]

Thanks for all the advice guys.  

Anyone recommend a good works manual that covers the crd?

Cheers.

Paul.

[daved]

Tuning boxes are a waste of money,yes they seem to work as the car seems faster etc but all they normally do is overfuel and end up fooking the injectors up.Had one on the BMW and it seemed to make a difference,until i spoke to a guy about it all and he said avoid them because of the injectors,then later found that  low and behold one of my injectors is down,advice came too late

Im intrigued, how does over fueling (to a relatively small degree) screw up the injector 

Perhaps soot it up a bit quicker than would normally happen but knacker it 

Also arent the injectors on these engines quite ...errr.......non robust as in replacing them is not unusual anyway?

Im only asking because i have a tuning box. It returns significantly more mpg if wound back and a lttle more than standard if set to a performance/economy balance.

More importantly, which thoroughly justifies the £80 i paid for it, the bottom end grunt especially with the caravan on the back is noticeably better.

more grunt for less fuel and no apparent downside over approx 2000 miles to date on a 98k engine is a no brainer to me but i am happy to be corrected 

I also knows several folk who have tunits and drive their trucks hard on a mixture of svo, bio and normal diesel. No reported problems attributable to the tunit 

[Tank]

No idea how,im just going by what a mechanic told me,and as for the injectors,well it seems they can take little time or all day if it wont come out according to the man at BM Oldbury thats now left there but did seem pretty clued up when it came to BM`s

[Bubba]

i worked as a tech in a landy dealership a few years back and whilst i am niether for or against chipping we did get problems with chipped vehicles and lpg vehicles................read voided warantys and huge expense

[daved]

i worked as a tech in a landy dealership a few years back and whilst i am niether for or against chipping we did get problems with chipped vehicles and lpg vehicles................read voided warantys and huge expense

First of all Im pleased to see youre over your green oval experience 

I agree with you re warranty vehicles. When i was working out remap vs tunit type box one of the drawbacks of the remap was a dealer or other suitably equipped techy would simple flash write over it if there was a problem to get to a basic starting position.

I do sometimes feel people se the tuning boxes to hide or compensate for underlying problems or stick em in as part of a tning program that has had zilch logic applied.

I run mine with a K&N to try and allow more air in too  seems to do the trick.

Its adjustable between 1 and 8 on the settings. Apparently 4 is usually a good blend of performance and economy. Ive had it on one and its miserly on the fuel but i have the uneasy feeling it may be uderfuelling at times, similarly if i set it on 7 or 8 it gulps the fuel,leaves a dirty grey cloud behind me but goes like stink.

I leave it on 5. Definite increase in power. Changes up to higher gear sooner unless youre kicking down. Best of all averaged out over several weeks 28 to 30 mpg without trying too hard, over 30 with a light right foot. On a run up the A1 @ 60mh 36mpg !!!!!!!  gob smacked so i did the trip again (airport run)  a couple of days later and t came out @ 34 without trying and acclerating a big harder.

Love my jeep