|
The 4.7 is not an OHV engine, even though it is a 2 valve engine. It's a SOHC engine. If the cam lobe acts directly on a non-adjustable tappet and you run the engine hard, the risk of valve burning is high.
The 4.0l used hydraulic lifters so the problem is pretty much non-existent.
|
|
unthrottled
Interesting thoughts. I had not considered this and to be honest I would not need the extra power from the V8.
So it looks like my search is narrowing down to the 4.0L petrol vs the 2.7 diesel. A little closer to a decision.
|
|
|
|
|
To be honest I like the GC too. I know if you listen to Top Gear they would slate it and tell you to buy the X5, but at almost twice the used price that is just not an option.
I have heard the 3.1 is no good and have not even looked at them. I think I have pretty much settled for the GC but still have to decide on LPG or diesel.
|
|
Prins (a supplier of LPG systems) keep a database of cars with reported problems running on lPG.
www.amrautos.co.uk/database_problem_cars.pdf
Note that a lot of later models are suffering from excessive valve seat recession, a problem that was largely thought to have disappeared.
With more manufacturers using direct acting valvetrains with non adjustable tappets, combined with the move to the cheapest possible valve material that will get the job done, valve seat recession is no longer the straw man it once was.
The other thing to note is your normal usage. LPG converted vehicles often start on gasoline then switch to LPG as the engine warms up. (the cold start is the only time petrols produce much soot, which blows the "LPG is a clean fuel" argument right out of the water). So if you do short journeys you might not see a huge improvement in running costs..
|
To be honest I like the GC too. I know if you listen to Top Gear they would slate it and tell you to buy the X5, but at almost twice the used price that is just not an option.
To be honest I've never known Top Gear to like the X5 at all but they probably would run down the GC and tell you to buy a Range Rover.
Note that a lot of later models are suffering from excessive valve seat recession, a problem that was largely thought to have disappeared.
I'd favour one of the earlier models, maybe 99-01 with a good service history.
So if you do short journeys you might not see a huge improvement in running costs..
Then again if you mostly do short journies, 17mpg isnt going to matter too much. LPG usually takes over from petrol pretty quickly and even shortish trips can benefit.
Out of interest unthrottled, Grand Cherokee LPG conversions seem to vary between the multi-point injector system and the single point. What (if any) is the difference? Keep the reply in laymans or my interest will quickly evaporate.
|
Out of interest unthrottled, Grand Cherokee LPG conversions seem to vary between the multi-point injector system and the single point. What (if any) is the difference? Keep the reply in laymans or my interest will quickly evaporate.
Go into fine detail unthrottled to keep me interested.
|
Keep the reply in laymans or my interest will quickly evaporate.
Go into fine detail unthrottled to keep me interested.
This is analogous to the question: "have you stopped beating your wife?" Anser "yes" or "no".
It's a good question. LPG is introduced to the system as a gas, unlike petrol which is introduced as a liquid.
Theoretically, there should be no difference in performance at all, since a gas can work its way round corners-unlike petrol. This means that each cylinder receives the same air-fuel mixture-hence no reason for multi point injection.
The problem is that a single point injection system fills the entire manifold with a flammable air/LPG mixture. If you get a backfire into the intake manifold, it is going to cause damage. Plastic manifolds could be literally smashed. Even with an aluminium manifold, the fire inside the manifold would take out the MAP and MAF, rendering the engine inoperable.
So, basically, it is safety.
The issue is confused since a lot of single point systems are 'open loop' (ie they use preset maps and do not respond to engine data). All multi point systems are 'closed loop' and use engine data to fine tune the fuel trim. But this is a question of 'intelligent' vs 'dumb' system, and not multi vs single point. Hope that satisfies both of you!
|
|
Interesting Unthrottled many thanks.
Thankyou also for the link above to Prins' problem vehicle PDF file, i notice most of the reports are apparently from customers and only one or two of those problem cars mention 'flashlube', i would have thought almost all conversions have a flashlube system.
The 'customer' being the source of information is interesting, not sure why Prinz would itemise the source of complaint, is there something should be read between the lines so to speak?
Being the owner of an older MB E i was heartened that only the A and V class feature in the list of models suffering valve wear, the possibility was stalling my decision to convert.
The chap who converted mine was of the opinon that it wouldn't be a problem but always fits a flashlube with his conversions anyway...a kit is so cheap and so easily fitted it seems to me like spoiling the ship for a h'aporth of tar not to.
I can't offer any advice to the OP, other than even on MB forums the general feeling i gather is that ML is not highly regarded for its build or reliability, i like the GC and would consider, but am always drawn back to Toyota's extremely durable products in this market.
Edited by gordonbennet on 08/04/2012 at 08:13
|
|
The GC made by STYR in Austria and the ML made by DB in America probably the reason why the ML has build quality problems.
|
|
Reliability wise, JEEP products have improved massively, MB are still rather patchy, maybe not as bad as the late nineties early naughties low-point - but still not good enough.
|
Thankyou also for the link above to Prins' problem vehicle PDF file, i notice most of the reports are apparently from customers and only one or two of those problem cars mention 'flashlube'
Well, since no one but a car maker can afford to do accelerated 60,000 mile test cycles, then the source of most of the long term complaints will invariably be the customer!
Some installers don't recommend flashlube because they either think that it is pointless or that it will interfere with lambda sensors so a lot of people don't bother with it.
There's still a lot of controversy regarding the valve/seat problems that everyone agrees are more prevalent on lpg converted engines than on ones running straight petrol.
To be fair to be lpg, a lot of the conversions are bodge jobs (when Billy discovers that he can't afford to run his Range Rover V8 on petrol-doh!) and so the lowest cost option is selected, rather than the right one. So some of the problems are likely to be due to poorly calibrated systems.
There's still a lot of ignorance within the lpg conversion industry about how lpg differs from petrol. Exhaust valve burning is blamed on the fact that lpg burns hotter than petrol (it doesn't), or that lpg burns so cleanly that there are no deposits on the valve seats to inhibit microwelding. (Possble, but not very convincing)
The two big differences are that enrichment is totally useless in a vapur fuel engine-the only way to internally cool the engine is to run lean. The spark curve is also different from petrol, requiring more advance at low RPM, and less at high RPM, not just 10 degrees advance across the board. It could well be the later burning of lpg at high RPM gives rise to higher EGTs than petrol and this is why the exhaust valves burn.
It would also explain why some engines run many miles on lpg without a problem since a lot of drivers never see full power.
|
|
''Well, since no one but a car maker can afford to do accelerated 60,000 mile test cycles, then the source of most of the long term complaints will invariably be the customer!''
I suppose most customers finding faults will return to their usual mechanic, so the compliants will be customers version rather than an objective (if possible) evaluation from an expert.
'' so the lowest cost option is selected, rather than the right one. So some of the problems are likely to be due to poorly calibrated systems.''
Yes i would agree with that, my own installer wasn't the cheapest but one who came recommended, works on classic cars primarily, and has indeed as far as i can see fitted the whole system sympathetically, neatly and in keeping with the car, so far so good, whilst losing the urgent 'edge' from the performance the car will still do everything i ask of it and runs smoother on gas than petrol...the installer had me return for fine tuning after several hundred miles so he could evaluate readings, i have no complaints and wish i'd gone down this route years ago.
I see posts from people concerned at flashlube costs which is piffling in the grand scheme of things and cheap insurance, i bought 5 litres for around £65 IIRC, at present usage should last around 18 months to 2 years.
Thinking about it the system is due for a service.
|
|
|
To be honest I like the GC too. I know if you listen to Top Gear they would slate it and tell you to buy the X5, but at almost twice the used price that is just not an option.
There is a reason for this, mainly because the X5 is about a billion times better in every respect !!
|
|
But Top Gear hates the X5!
|
But Top Gear hates the X5!
Because it's a chav wagon!
|
|
The GC repeatly comes last in the annual climb a ski slope competition always won by a BMW except one year when a 4x4 panda won.
|
|
...when fitted with proper off road tyres, I'm sure that's true. However, all the X5s I've seen come equipped with wheels that look like they came from a Pacific class steam locomotive.
|
|
|
The GC repeatly comes last in the annual climb a ski slope competition always won by a BMW except one year when a 4x4 panda won.
Yeah because we all drive up ski slopes on our way to work all the time.
|
|
FYI it was meant as a reference taken to extreme a GC is pretty useless when taken of road due to its very limited auto box whereas the BMW is the bees knees.I personally think both are grotesque.
|
|
The X5 has ****** all ground clearance and is therefore useless off road, it might have reasonable traction fitted with the right tyres - but an off-roader it ain't. Perhaps all the poser skiing types buy BMWs hence the "wins" on the local slopes? (no decent competition).
|
|
With the exception of crawler gears for towing, I don't see how the gearbox really affects the ability of a vehicle to pull itself up a steep hill-especially with an automatic where the torque converter can slip/multiply torque quite happily.
The wheels 'see' only tractive effort and don't know (or care) what combination of engine torque and gear reduction created that tractive effort.
Aren't all these snow/sand/ice/steep hill settings just shiny toys for people who can't operate the throttle properly?
Edited by unthrottled on 09/04/2012 at 23:01
|
With the exception of crawler gears for towing, I don't see how the gearbox really affects the ability of a vehicle to pull itself up a steep hill-especially with an automatic where the torque converter can slip/multiply torque quite happily.
The wheels 'see' only tractive effort and don't know (or care) what combination of engine torque and gear reduction created that tractive effort.
Aren't all these snow/sand/ice/steep hill settings just shiny toys for people who can't operate the throttle properly?
What on earth are you towing that needs crawler gears? Automatics simply use the torque converter in 1st to get going, however steep.
|
What on earth are you towing that needs crawler gears?
A horsebox perhaps?!
A point was made previously that the GC came last in a ski slope climb because its transmission was no good. I just don't understand how.
I can see how excessive converter slip would overheat the transmission fluid and cause poor fuel economy and weak acceleration, but not failing to get up a hill.
Edited by unthrottled on 09/04/2012 at 23:16
|
|
It isn't for outright controllable pulling power that you need low range for, its being able to use engine power alone to control descent, in severe off road conditions you do not touch the brakes at all.
This is where some modern turbo Diesel vehicles fail unless they have very low range giving exceptionally low crawler and reverse gears, without the low range the engine revs will drop below turbo spool and the vehicle will simply come to a stop or be unable to control its own descent without braking, A Bad Thing.....
....i have experienced this with an ill specced rolonoff skip truck before leading to having to use excessive speed under full throttle to maintain progress in severe off road conditions, in turn leading to serious transmission and suspension damage....this problem only cured on the International Harvester engine used by increasing the fuelling to bring power in far lower down the rev range (a cheap simple remap if you will), oh and fully rebuilding and strengthening the double drive axle location fittings and location arms.
In auto form my Hilux displayed no steep hill retardation even with 4WD selected, but select low range and you could descend any angle you chose on tickover and the truck would simply control its own descent, without any form of electrical braking trickery, likely to fail expensively in due course.
I don't know much about GC's, do they not have low range?
I can;t see how an X5 would be any better, unless the GC's tyre choice was poor, any links to the article?
|
..i have experienced this with an ill specced rolonoff skip truck before leading to having to use excessive speed under full throttle to maintain progress in severe off road conditions,
But, Gordon this only applies to vehicles with a very low power/weight ratio like the truck you mentioned.
For any ordinary car/SUV, lack of engine braking/insufficient power at low revs is pretty much a non issue. That's why you don't see jake brakes on passenger cars!
I know that off-roaders don't like using their brakes to control steep descents-why is this? I'd rather use brakes than massive gearbox reduction to retard descent.
|
|
Unthrottled, the lack of power still applies to 4x4's too, especially if they are turbo Diesels with the current fashion for very high first gears (leading to expensive premature clutch wear in some cases), in very heavy off road conditions as drag forces the speed to descend the engine literally runs out of puff once the revs creep down to below turbo spool revs ,low range is normally low enough to enable tickover crawl up hills you couldn't stand on.
I always loaded 4x4's in low range, more control and kinder to the vehicle, the approach angles minor in comparison to off road, some wouldn't even make it up onto the top decks of some of the older transporters i had in high range.
Off roaders don't like using brakes on slippery surfaces because it will inevitably lock one or more wheels which can start to spin the vehicle around or end up in a full accelerating wheel locked plunge, half way down a slippery descent that is likely to end in getting fully sideways then you hit a bump and its literally all over, it is always safer to allow engine braking alone to control a steep descent in slippery conditions, this has to be in a gear low enough for the engine to have retard effect.
The latest all singing all dancing off roaders that never go off road do have hill descent control fitted, this does as far as i know utilise the brakes but the computer finely brake inputs to each wheel to provide stable progress....course this is just something else to go wrong rendering the vehicle useless for its job...kerching.
|
|
Interesting video.
Anybody got a clue what tyre requirements and standards were, as without some set standard the video is misleading, as these things often are.
|
|
Treat it as a bit of fun but if you must know the vehicles were fitted with the same manufacturer of standard winter tyres I believe it is sponsored by Continental could be wrong.
|
|
|
|
|
|
