I knew it – I heard it, I could see it if I looked in my rear-view mirror, and if I looked at the fuel consumption statistics – something was wrong.
My other (better) half would have said – “what, something wrong again, surely not!” – sarcasm is her first language 🙂
Let’s be clear here, my Audi A3 is a ’52 plate, 1.9TDi quattro sport – the PD130 lump, it’s got 227,500+ miles (yeah, proper miles, not those weird kilometer things!) on the clock – so safe to say, worn in a little bit, and with all things that age – and I’m going to use the Indiana Jones quote here “It’s not the years, it’s the milage honey” – this is ever the case with my A3.
My colleague at work, that has the same lump in his wife’s VW, also noticed the whistle, and the clouds of dark black smoke as I tootled out of the office car park every day – those same black clouds that I could see in my rear-view mirror pottering along at any speed – although interestingly enough, mostly about the 1700-1900 rpm range.
His wife’s car had had a failed intercooler, and had been dropping little bits of oil on the ground every now and then – just as Olivia had started to do some time ago.
Now, however, I’d got next to no power, acceleration from cold was non-existant until the turbo had *really* spun up, at 2500 rpm – so something was really wrong.
I’d also noticed that in addition to the lack of power, the funny whistling from under the bonnet, the black smoke, my fuel consumption had jumped drastically – all pointing to an effective “over-fueling” situation.
For those that don’t know much about turbos, whilst you might find a turbo on a high performance car (although my other car – RS4 is quite happy with ~420bhp naturally aspirated thank-you!) – a turbo, as pioneered by SAAB in the ’60’s and ’70’s, main use was increased economy – and mine was through the floor.
Turbos work by using the exhaust gases to spin a shaft, the other end of which is used to compress air in the intake side of the engine, which, due to the laws of physics, warms up, (not a good thing – you want cold air, for more oxygen per unit volume) so to cool it back down before it goes into the engine, passes through a radiator for air – the intercooler.
All this gas flow needs to go through lots of pipework, a failure at any point lets precious air out, and not into the engine where it’s needed at higher than atmospheric pressure.
Any loss in air, means that the car’s ECU probably hasn’t taken account of the loss, and thus sends fuel into the engine that it *thinks* has enough air to burn properly – which, clearly it doesn’t, and on a diesel, that’s reflected in a lot of smoke.
(Note: Diesel engines historically on cars used to use an over-fuelling condition to limit the engine revs – i.e. they’d dump fuel into cylinders knowing that it couldn’t burn, but it would kill any further performance that would lead to an increase in engine RPM – thus saving the engine from self-destroying!)
First things first – let’s create a little working area :
I’ve moved house – and it’s still all up to eyes and ears with “stuff” – mine and G/F’s – so – I “MacGyver” it – engineer a working fix with some stuff that is just lying around, and get on with the task in hand – in this case a workbench 🙂
Then – take off the front bumper, the intercooler lives behind that.
I’m not going to show any picture of removing the front bumper – it’s dead easy, and I can pretty much do that in my sleep now – 4 plastic pins under bonnet, the two rubber silencer strips above the headlights (one on each side) and then the screws attaching it to the front wings and wheel arch liners – and POP! It’s off.
Above: This shot shows the front bumper off, and the car on ramps.
I took the bumper off before driving it up onto ramps, as the lower lip of the bumper (spoiler bit) fouls the ramps 🙁
I’ve not got the tiniest hands, so access to the top bolts and the air pipework is under that right hand headlight – so to make life really easy, and avoid mashed knuckles – that headlight is coming out.
First – a little MacGyver style headlight alignment tool – I figure that if I mark the beam before I take it out, I can check against those marks when I put it back in – in this case thinking, and marking on the outside of the box !
Headlight out :
Left: on the bench (mines a ’52 plate, so that means it’s a facelift model hence the all-in one headlight unit)
Right: A nice hole where the headlight used to be – you can just about see the intercooler pipework.
Now, we’re moving along nicely.
The intercooler attaches to the pipes with quick-connect clips, which means we don’t have to mess around with any of the old-school jubilee clip nonsense – it makes things easier – in theory.
I find that you sometimes when you pop out the clip – it either pops off and drops out of reach on the floor, or you don’t pull it enough, and the hose still stays resolutely attached.
Right: nice shot of the dead intercooler. Look how nastily dirty it is at the bottom – that’s a thin (read thick) film of oil that is attracting all kinds of crap to it, leaves, plastic, birds, small children….
Bolts, unless their first name is Usain, they don’t go quick – especially when you get ones like this which rust themselves into the captive nut behind the panel.
Left: Rusty the bolt, captive nut behind the drop support nicely destroyed it’s cage,, just enough so that the cage has no grip on the nut to undo, but not enough that I can get a square spanner or wrench on it with enough purchase to stop it spinning around.
Remember me saying I’ve not long moved – so where are all my electric tools for cutting stuff – buggered if I know, so resorting to the old tried and trusted hacksaw method.
Right: Hacksaw time. Through the outer sheath, that was part of the old intercooler (use to have a rubber surround keeping it mounted to the intercooler)
So – once off, it’s a total doddle to put back on – and as these show show, a lovely clean new intercooler, all ready for the rest of the car to be put back together again.
(Note: The white bucket under car was supporting oil drain container, as was doing a standard service of air and oil filter, complete with a change of the oil)
Whilst I was doing this, I had the front bumper off, so a good time to “tie” up loose ends – almost literally.
Since I first took the front bumper off this time last year, I’ve had a loose cable, with a device attached to the end – and despite a couple of attempts, I’d not been able to identify what the device was, so, this time, I was going to make sure.
So I disconnected the cable from the device, and found my wire brush to clear off all the crap – and found a device with the VAG part number of 8Z0 820 535, so a quick Google search later revealed itself as the external ambient air temperature sensor.
It should fit somewhere on the metal arm that the horn is fitted on, but, having had the horn replaced more than once, the arm that is there at the moment, it doesn’t seem to have a hole that this would fit in – so out with a trusty blade from my Leatherman, a quick twist, a nice circular hole was “engineered” into the very bottom lip of the spoiler – and viola – perfect solution!
Once everything was bolted back into place, and a test run performed, no excess smoke ! That’s what I would call a success.
What is even more of a success, is that prior to this work, the fuel consumption had gone up to 36mpg – quite a horrendous figure for a diesel, and post work – it was back up to a way more respectable 43 mpg (based on the dash computer figures).
Let’s put this into context – the A3 has a tank capacity of 55 litres, which is 12(ish) gallons – so I could expect to get around 430 miles out of a tank at 36mpg (which is in practice, 400, as it’s not being run dry every time!) – HOWEVER – at 43mpg, that’s over 500.
(Actually – if you go by the odometer, it was around 410 miles from when I filled up, to when I put fuel back in, and around 520-530 miles post work)
So – a little bit of maths, that’s 100 miles per *TANK* difference – so in 4 tanks time, I’ve effectively saved a complete tank of fuel… at today’s prices for a full tank, the cost of the intercooler will have paid for itself between 4 and 5 tanks worth of fuel – that ain’t bad to my mind 🙂
