Race Engine Forum UK

Silly or clever?


Hello all,

I've just been putting together the top end of the engine on my integrale road car and have a question over the positioning of the oil feed pipe to the turbo.
As standard the oil leaves by the oil filter housing and passes by very close to and is actually fixed to the exhaust manifold, this will have the effect of heating the oil before it gets to the turbo bearings, and there is the question: Silly or clever?

Clever:
Nothing runs well on cold oil, particularly turbos, If anyone has tried accelerating hard (shame on you) from cold with a standard type turbo (IE not BB) you will know that it just doesn't want to know until it has warmed up, likewise for the engine, but then of course it is a stupid thing to do. What heats up quickest on an engine but also cools down quickest? Of course, the exhaust, in particular, the manifold, so this has not only the effect of heating up the turbo oil quicker, but keeping it very hot under normal running conditions.
Thinner oil = Quicker spool up time.

Silly:
On the other hand, have Fiat/Lancia been very lazy with the design and overlooked a potential problem area here? Will the oil cook in the pipe after a hot run? Of course, really, you should go for a cooling off period on an old turbo motor such as this before shutting it down, but still....

I'm favouring 'Clever' at this moment in time, but what do you think?
I have, at the moment, the chance to pull the pipe clear (as you can see I have a non standard manifold fitted too so have lost the fixing point) Will I make things better or worse?

Martin.

I doubt Fiat/Lancia have made a mistake. My only concern is the use of thin oils. Thin oils go even thinner when hot, and cause "Shear Wear" when metal to metal contacts.
Your very right about warm up before reving and cool off after. Companies like Turbo Technics make a very nice living out of cooked Turbos. Have you noticed how many of the new high powered Diesel Turbos are failing due to faulty Turbos? Seems to effect most of the variable vaned Turbos! And they are not reconditionable due to the delicate vanes.

Andy.

Given that the pipe used (if it is anything like the ones used on the smaller engines) is rather lightweight (flimsy even) I would say that the proximity to the exhaust manifold doesn't really make an awful lot of difference. The very fact that it is attached to the turbo itself means it is going to get very hot indeed, the thermal exchange between the manifold and the pipe by comparison is going to be almost irrelevant.

The pipe will heat and cool very quickly by itself, the oil travelling through it will provide a large thermal delta from one end of the pipe to the other (from the ambient oil temperature towards peak while passing through the turbo housing), warming as it passes along it. All the manifold will do is increase the delta value a bit at one end of the pipe and reduce it at the other.

The "clever" point will still stand - it will warm the oil that little bit more but I don't believe it would cook the oil significantly more than it would if the pipe were re-routed.

A most interesting little thread!

I look forward to some more observations on this issue.

GC

Actually following on from my thoughts earlier I have a question of my own about those pipes.

The repeated heat cycle tends to anneal the pipework and while this isn't too much of an issue for day-to-day running it does become a serious issue for maintenance as the pipework nearly always shears off as soon as you try to remove it.

Not being a metallurgist I don't have too much to go when looking to solve the problem but I am guessing that some metals would be more suitable for the job - the problem is that I have no idea which. If it were for a road car I probably wouldn't bother worrying about it but for racing purposes (where I have this kind of setup) it can be a real pain.

Anyone have any ideas?

I heard from a guy who has some experience with these engines that the pipe carrier connected to the exhaust manifold gets heated so much it burns oil and can clog the pipe, reducing it's diameter with time... Can this be the case?

In the warm-up phase, I seriously doubt that there is enough radiant heat from the cast-iron ex manifold to heat up that small oil feed pipe. The oil is likely to achieve a good circulation temperature (40 deg C plus) much faster than the manifold.

My concern would centre around what happens to and in the pipe when the engine is hot, that's another matter altogether.

Kenlow engine heaters are a great way of warming up the engine by the way.

GC

The cooking of the oil is probably down to the turbo running very hot and not letting it cool down, so on turn off , the oil tends to cook and then clog pipes due to heat soak.

It also could be the type of oil used. If the viscosity is breaking down quicky, the oil will soon turn gloopy and clog.

Maybe an underbonnet "stick-on" thermometor is needed to find the temp of the pipe when running and on turn off. This will indicate if the pipe is heating up after running too by using a second thermometor.

Andy.

Thanks all for your replies, they make interesting reading, I'll give it some more thought before making a better informed decision.

Martin.

Make cevlar/alu around the pipe.

That would just make things worse Acki. The pipe connects directly to the turbo housing which gets hotter than the rest of the manifold. Convection along the pipe would make it hotter *with* lagging than without since there is very little energy lost to the atmosphere.

Cold fluids become faster hot!
The pipe will be colder than the turbine housing because of the oil!
The pipe don't have 1000‚°C when the housing it have!

http://www.sandtler.de/katalogangebote/ ... schutz.htm

Leaving aside for now - all the good arguments about pipes - I imagine roller bearing turbos run up faster on colder oil, am I right?

GC

But the efficiency will be lower ;)

Howdy!

thought, heat flows like water conducting from THigh to TLow according to heat transfer theory. So that pipe should conduct heat from, OIL, Header - via Air, Turbo.

It will transfer heat to the lowest temperature medium in the area: Oil, Air and that cooler portion of the metal tube which is the stainless flexhose.

Should you consider making a larger diameter rigid stainless tube and connect weld to a stainless flange for the turbo attachment? Certainly the Stainless has to be of proper spec as well as the welding.

Perhaps the output hole could be enlarged going to the turbo as long as the bearing surface is not comprimised, like what one may do to crank oil passages...

Grounded Sheilding not attached to the tube nor to the Turbo/Header.

Would it be reasonable to consider re-route via custom stainless tube and slightly longer hose?

If starvation is an issue, have a reserve cansiter gravity feed
If cold oil is an issue on startup, I suppose you could have fabricated a custom Key-On/Toggle thermostatic oil warmer/ reserve tank, however, I have to say that may be a bit of overkill.

Oil, I guess something has to flow and not burn easily, 10/50 full synth depending on application and ambient temprature from Time0 to Timef.

Seems like a very interesting subject for which I need to learn more.
I may just be blowing gas in the wind....


I am really enjoying learning from these posts- thanks!

Paul