Turbo Diesel vs EO(ff)C
 

Hi,

I've tried EOC a couple of times to get used to the idea. Inflating tyres to the sidewall limit makes the steering usable so thats fine.

One question which struck me though is turbo temps. One thing advised to Turbo drivers including diesel, is to let the engine idle when stopping from high speeds - for example taking a break on the motorway. This was to allow cooller oil to circulate through the turbo and prevent heat soak doing nasty things to the seals.

My question is would EOC do the same thing, leave the hot oil sitting in the turbo ? There is airflow of course but the turbo is buried behind the engine, under a cover and just above the exhaust. Also with a grill block it isn't going to get much flow.

I had some suspected turbo issues recently and new ones are very spendy - luckily I just had a leaky boost pipe fixed with some gaffer tape for now.

Thanks.

A.

I wouldn't recommend a lot of EOC to turboed engine users for that reason. That, or you have an electric oil pump that continues to run after the engine has been shut down.

You might be able to get away with it more if you used synthetic oil, but I'd gather more info on it before trying it out.

I don't agree with letting your turbo cool down by idling with a diesel when getting off the highway. Up to 70 mph my turbo is not even pushing 5 psi. Just the time you spend getting off the highway till you can actually park is plenty of time for the turbo to cool down.

That being said, I would not pulse and glide with EOC in my TDI on a regular basis. I don't like the fact of requesting max boost for ~10 secs and then immediately have the oil sit in the turbo. I do however EOC if I've been driving lightly in the previous minute or so.

If EOC is any top tips then it may be worth adding this caveat.

+1

I have to let my yaris idle for about 4 to 5 seconds before moving off due to some weird lack of power after i start it. It's a bit of a pain when i get caught short at a light that unexpectedly goes green. Perhaps my oil pump is getting tired and takes a little longer to get up to pressure......oh dear....spendy, as they say!

ollie

Does the Yaris have a turbo? your description would fit a turbo that hasn't spooled up yet, which would be cured with a bit of revving in neutral.

As some one who has coked up turbos in the past I may have some insight.

Below are my ***understandings***

1) PSI is not what is going to cause failures (preventable with a turbo timer), center housing temps are (which are largely dependent on EGT's. ("we" are cooking the oil in the turbo after shutdown, which leads to coking, which leads to poor lubrication then failure)

2) Synthetic oils ability to withstand much much higher temps is a huge asset here.

3) If we are running our center housings (turbo oil temperatures) up near/ above coking point, then we will have very quick oil breakdown (another god point for doing Used Oil analysis).

4) if the center housing is not at/ near the varnish/ slugging/ coking point then the heat soak from exaust should not push the center housing up too much farther.

5) even the worst oil available today is better than almost any oil available 20 years ago.

Anybody interested should go hang out on Bobistheoilguy, not so much for opinions, as for information.

If any of my understandings are wrong, please correct me.

If the Yaris has VVT then it may be an oil pressure issue, I think (maybe wrongly) the VVT system uses oil pressure to make its adjustments. Maybe a non-return filter may help.

dremd - you may be right. A lot of VRS owners have put down turbo failure to not allowing the turbo to cool - kind of you hammer down the motorway at 70-90, stop for a pee and shut the engine off in the rest area / services straight away. Do it enough times and the oil in the turbo stays there happily cooking.

Not sure about coking, the issue reported is that the seals start to fail rather allowing oil into the turbo and lots of blue smoke, rather than the bearings failing which would be poor oil supply due to it coking.

Of course I could be wrong too. I feed mine the VW spec 505.x (I think thats the spec) synthetic oil and at the moment it uses non between changes which is why my I looked elsewhere for my recent turbo smoke than worn parts. Luckily my gaffer tape / turbo boost pipe fix seems to have cured it.

You are correct about oil pressure, I've had a few Toyota VVTI motors apart before.

To be honest, I forgot about turbo seals :confused:

Is your VRX a PD? I'm not up to date with Euro TDi years/ motors.

MY ALH TDI used just over 1 cup in the last 60,000 miles (last drain), I thought I was burning a little bit, but an astute friend noted that that is about the amount that I have sent off for sampling.

I suspect the smoke you were seeing was as result of lost boost pressure--the boost pipe you fixed was on the pressurized side, correct? Assuming that, the smoke was likely unspent fuel the engine injected while expecting full boost pressure. Hence the reason naturally aspirated diesels tend to be a bit smoky; the extra air helps to burn all the fuel.

The Rover VVC uses the same method, hence my thought. Worth a look at the non return type filter or is this the wrong tree I'm woofing at ?

The VRS uses the 130 PD engine, either the ASZ or BLT engine codes, mine is the ASZ one. I did monitor the oil when I got is (24K miles) as I noted the replaced turbo warranty paperwork but it didn't and hasn't used any between refills since.

Being an old BL/BMC A-series user I'm kind of used to engines using a bit of oil. I did have a small leak which in retrospect was the oil film leaking from the joint in the turbo pipe and making its way down to the floor when I parked on my sloping drive.

Thats pretty much it. I shall monitor the gaffer tape (for survival in rain etc) and renew as needed. At the next service I may go for the uprated ones those who have remaps go for but they cost a lot, or a dogleash fix as described on TDI forums but modified my leak is on the join halfway down and not at the turbo at the back of the engine.

A guy at work who is into boosting his MINI a lot suggests single piece uprated 'chav' (aka 'ricer') style ones but it will need some flex in it as the engine moves but the intercooler stays still.

I'm glad you started this thread, Arragonis, as I'm EOCing my HDi more often lately.

As for the turbine/oil problem, would having a small electric oil pump solve the problem? It would keep oil circulating either when the key is turned to the ignition position, or when the oil temperature is too high - sort of like the radiator fan, which can keep going even after parking the car. This pump would also increase the oil circulation speed when the engine is on and under load.

I did briefly look at electric pumps but a lot seem for race use, so not sure about using them long term on the road. I have seen some people claim 10-20K miles on one alone with no issues. It would be expensive though and it would take a long time to recoup the cost on EO(ff)C vs EO(n)C.

I'm sure someone on here will have done 100K in a TDi with EO(ff)C with no effects, we just need them to step forward and we'll all believe them... :rolleyes:

EDIT - The ones I saw were also more for bikes that cars.

Well, you only need the pump on while the engine is off. So, you'd need a circuit to do this. That would greatly extend the life of the pump so you could probably use some cheapo pump and be fine.

Cruising, even at 90 mph, isn't putting that much load on the engine. The calculator shows about 42 hp required. Most likely, you'd be pulling a vacuum rather than boost. (I was generous with all the inputs, so many cars would need less)

I can see a problem with P&G type driving, though.

Well, the fact of the matter that our cars make bost at idle with no load prety much shoots this one out the window.

At 90 I believe 5 PSI is fairly normal for a 1.9 TDI.
I make 3.x at 65~75 MPH

It doesn't matter how much boost you're running. It matters how much fuel you're burning and how hot the exhaust manifold/turbo is getting.

I thought EGT was roughly correlated to boost level. Can someone with an EGT gauge clarify what conditions lead to high EGT?

Edit: some internet reading tells me that EGT is related to the amount of FUEL used, more than boost.

In my experience from listening to the whistle boost varies more with throttle that speed. I can do 90 mph downhill with no boost, and 60 uphill on full. Mine whistles at under 1.5K when setting off and short shifting.

What are those issues please ?

Not doubting but wondering as I don't have an SG or similar yet, how does it go into vacuum with no throttle ?

The Civic boosts from very low revs so avoiding it entirely would be tricky.

I would be willing to blame a faulty boost gauge on that one.

IIRC EGT indicates temperature of the exhaust. I know, that's making it awful simplistic, lol. But for a high EGT, think lots of air and lot of fuel that is kept close to stoichiometric, whatever that would be for a diesel. One method some hotrodders use on the dragstrip with their diesels is turn up the fuel: it creates a ton of smoke, but that extra fuel lowers the EGT and keeps it in the happy place. Keep the engine from smoking and it requires a computer control to keep it close to the burn off the manifold temp.

Higher boost would raise the egt, especially if not accompanied with increased fuel injection. I'm no expert, so correct me if I'm wrong.

I do know higher EGTs spell death for a diesel engine, so it's best to avoid that scenario.

I recently read an article on start&stop systems (which are expected to be present in 70% of new cars in Europe within a few years) and one of the problems to be overcome (beside the battery and starter) was the turbo. Since start/stop systems are usually added to "eco" versions of existing models, they are usually paired with an already efficient turbodiesel. To overcome the problem, turbines are now built to withstand being shut down while hot, much better than a few years ago. One company (Mitsubishi, I think) has an extra pump for lubing the turbo after shutdown.

i take it my petrol turbo would see similar issues regarding fried turbos or seals..
The low pressure turbo setup on my saab is weird as it drives like a tdi.. Lots of low end boost!

What is a guideline % increase from engine OFF cruising vs engine ON?
I doubt it'd cover the £600+ for a new turbo..

Higher boost lowers EGTs when not accompanied with increased fuel. The reason is that there is more air to heat in the cylinder with the same amount of fuel. Note that a diesel doesn't get hot when running lean like a gas engine.