High Miles ex police xc70 - bad idea?

[Tannaton]

Originally Posted by FreshAir

Unless diesel technology has changed that much, then the basics of diesel fuel economy comes from its ability run at very lean mixtures. That is very high air to fuel ratio.

The higher fuel pressures since I studied this stuff improves economy by smaller droplet sizes, plus the ability to more accurately control the injection process.

The fundamentals of diesel economy still stand though, that is when running at very high air to fuel ratios they are very economical, if you drive very hard in a diesel you can get the economy down to petrol spark ignition levels (I managed 26mpg in a 1.6 diesel once on clear roads, whereas 55mpg was normal driving economy...).

Petrol spark ignition engines are generally constrained by the requirements of the catalytic converter to have an air to fuel ratio of around 14.7 to 1, so are actually way less economical then they would be if lean burn technologies had been allowed, but the catalytic converter producers were very wealthy and effective lobbyists back in the day. This is not as tightly constrained as it was but again generally it is the case, so it is not as easy to get possible to get as good economy or efficiency from petrol spark ignition engines.

I see what you are saying.... with diesel engines they are generally more efficient at lower power outputs as they always run at full throttle and hence maximum compression ratio. With petrol engines it's the other way around, a petrol engine on light throttle might only be running at a compression ratio of say 4:1. All of that to some extent goes out of the window with forced induction (turbo charging).

[FreshAir]

A petrol engine generally manages the power level at a given speed by throttling, that throttling causes pumping losses. Basically the engine is forced to suck in the air (and fuel depending on injection site) through a small gap - the throttle. So small amount of air sucked in, and small amount of fuel injected as the AFR (Air Fuel Ratio) needs to be maintained around 14.7:1 because of the catalytic converter, although the range cannot vary too much without one either.

A diesel on the other hand does not have that inlet restriction, unless there are swirl inducing devices in the inlet for low load situations, so there is much less restriction during this stroke of the cycle. This is because diesel runs over a massive AFR range - sucks in lots of air, then injects a little bit of fuel.

Where does a turbo fit into this? Increases air pressure so that more air can effectively go into the engine each cycle so more fuel can be injected for a given cylinder volume. So increased effective volume is achieved without the frictional losses which are generally the greatest hence greater efficiency is possible.

[tonys1966]

i owned this car and sold it to the seller a couple of years ago-approaching 200k
when i owned it i serviced it twice in the year or so i had the car
fitted genuine cam belt kit and volvo bolts etc
new aux tensioner and belt
couple of tyres
osf lower balljoint

body had a good few marks gear selection console had a bit of play
clutch/flywheel was done at decomission sale

was uber reliable,great to drive had full history-police and all the private services

i was myself thinking of buying it back but opted for a newer auto

time will tell if i have done the correct thing

[monkeh]

I've ignored the past 3 pages of responses to give you my opinion.
You know the d5 lump, It'll take the hammering of a pursuit. Being plod? I assume it'll be twin turbo'd.

Manual? As long as you have a bit of a hint that clutch and flywheel is good, go for it. Else set aside £1200. 9 hours labour to do that.
Also check for driveshaft leaks on front output shafts. I just got stung for a rebuilt m66awd box for £2600.
HOWEVER, Smooth as silk, Service the haldex and it'll not let you down. I have the Poverty spec SE model, If you're doing 25 miles each day, that'll be ok, Volvo's regenning system is good. If you get the "Soot filter full" time for a thrash.

Aside from the usual holes in various places, depends on how they decommissioned the car. Either they cut and tug, or its taken apart carefully. You might have a dose of rattly trim syndrome at the front. Rear, has fragile plastics, same as the p2.
Entertainment system should still work.

Mines 177k in, and still is as tight as a new car.
Even though it's been looked after by plod techs, set aside some time to clean out the emission system upstream, EGR and flaps and that.

[tonys1966]

The clutch/fly was only appx 20k old when i bought it-so figure on 60k ish now-the plod got 150/60k from it
Transmission as new,dry as a bone,no whines-nada

big front disc model-forgot i also did pads all round whilst i had it

interior was ok,tatty below the boot cover where you cant see-i re-routed the harness to tidy and removed some redundant wiring-it had an aftermarket towbar fitted also

The rear trailing arm bushes were a little squeaky when i sold it but i am sure the new owner had them done

my lad had also set the alignment up on the hunter not long before it went

and yes 205 twin turbo-probably in police tune so maybe 230bhp...

[Puffster]

Originally Posted by tonys1966

and yes 205 twin turbo-probably in police tune so maybe 230bhp...

ECU is the Polestar unit but called "Police"

[Puffster]

Originally Posted by Shortos

As a police officer with 22 years in, I would never buy an ex police car based on my knowledge of my constabulary only. They are generally serviced quite well but sometimes with reconditioned parts as the maintenance is contracted out to companies who are looking to make as much profit and charge the police as much as possible. Always driven hard from cold and bumped up and down kerbs, speed bumps etc. Plus I would want a replacement interior as god only knows who and what has been transported in them, and it is very rare that they are cleaned professionally

The Police/Emergency Services spec ones come with a very hard wearing half leather interior. My interior had been abused, seat-belts a bit frayed, bolsters worn & so on.

No idea what's been transported in them either but I did find a mug shot photo of some guy they must have been looking for and an iPhone 5SE stuffed under the seat - when I turned it on, it was in Icelandic so I imagine someone lifted it off a passenger at Stansted as mine was a Essex Police.

I bought a genuine load carrier cover and a centre console with the cubby & cup holders and swapped out. Other thing was re-connecting the front speaker wire that had been cut.

It still looks scruffy, where the holes in the roof were the paint is all discoloured and the trim doesn't line up from a couple of small knocks I guess. However, it is totally reliable and goes like stink, handles and stops very well indeed.

Not a show car, was very cheap to buy for comparable plate non Police even at same mileage but it does what I need it to, whenever. Love it