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MG MGF Technical - Oil too cold?

I don't think my oil gets hot enough. I know you sholdn't rev a cold engine and I don't go above 3k revs until the oil temp reads 60 at least but reading on my Truimph web site (bikes) there is a thread discussing oil temp and it says that oil is not at its optimum temp until it reaches about 224 degrees F (about 95 degrees C).

On some journeys home, especially in the cold and a slow journey, the oil does not reach 90 degrees C.

Is the above correct? am I causing damage to my engine? do I need an oil heater in the winter?

I find it a real pain as I get overtaken by all sorts of vehicles and I resist going fast on a cold engine but it means I can't go above 70 mph (3k revs) on the whole journey home - am I being too cautious or does no one else care about their engines? or know any different?
Kevin s

Kevin,

I wouldn't rely on the accuracy of the oil temp gauge.

Sam
Sam Murray

.... but you are right to give the oil a few minutes to warm up and circulate.

Brian

Kevin,

Cold starting is when most wear occurs, to reduce this to a minimum the flow of oil and using esters in oil, as they cling and do not drain back, help.

The oil is also thicker at low temperatures and usually oil coolers are set at 80c so I would wait to 90c before adding revs. Anti wear additives also need heat to work properly. Oil is slower to warm up than water and then usually runs above water temp, so water reaching operating temp. is a guide the oil is nearly at right temp.

A mineral oil is usually ok for temps between 90-110c and synths 90 -125c

A oil/water cooler would help warm oil.

With a K engine its worth waiting to all up to temp.

Paul
Paul

1) 224 degF = 105degC (not 95)

2) unless you push the car, it won't generate the heat to get the oil up to temperature - it's a catch-22 situation.

I would not worry so much about the rule of 'dont use more that 3k until the oil shows 60deg'; It's a useful guideline and no more.
I'd argue that the last 5 miles or so, and the cooling-down period are perhaps more significant
Steve

I'd say that the answer is all of the above Kevin! LOL

Yes, the oil temperature gauge is probably not all that accurate - I've not measured the oil temperature with a calibrated instrument to know what the temperature actually is when the gauge shows 60C. Moreover you have to consider the position of the oil temperature sender - it may not be giving a true indication of what the temperature of the oil is in those critical areas.

The optimal working range of the oil is going to be a function of the oil being used. Using a fully synthetic 0-40 will have a far broader temperature operating range than a semi-synthetic 10-40 for example.

But keeping to the "KISS" principle - keep revs below 3000rpm until you see at least 60C on the temp gauge still applies.

If the temp remains low-ish, then there still isn't a problem - under the conditions you describe, "they all do that sir" - the only 'fix' for this is the use of a water/oil heat exchanger (as fitted to the VVC 160 engines as standard, for example). Whether you consider the expense of fitting one reasonable is something that you need to decide, but these do operate as an oil cooler as well as an oil warmer, so IMO are worth fitting if you plan partaking in frequent track days :o)
Rob Bell

Hi,

Funny, I was musing on this topic whilst in bed this morning! Can an oil be too cold if it is capable of circulating freely?

Anyway, the 3000 rpm self-imposed limit is not only difficult to keep to, but can be damaging to the engine. From my house I travel about a quarter of a mile to a crossing, and then pull away up a moderate hill. I have to exceed 3000 rpm to stop the engine slogging. I always give the engine some 10 to 20 seconds of fast tickover after cold starts, then drive moderately for a few miles (and slightluy less moderately after).

I read a book about camshafts some years ago (yes, I've always been sad), by Piper cams I think, and they said always take the engine up to at least 2500 rpm immediately after starting, to reduce the stress on the cams. The worst thing you could do was to turn the engine over slowly by hand.

So you've had it whatever method you chose. Just keep the engine turning over happily and all will be OK.

Just go to Longbridge and see the cars being driven off the production line. You will have no fear of revving the engine any more!

Regards, Kes.
Kes

>> Funny, I was musing on this topic whilst in bed this morning!<<

Hilarious!!!!.

:o)
Mark.L

http://www.gi.alaska.edu/ScienceForum/ASF7/747.html
Paul

>>>>unless you push the car, it won't generate the heat to get the oil up to temperature
===surely if you push the car the oil will *never* warm up ;-)
David S

Kevin,

I think your coolant thermostat may be broken ? (always open).

The same is with my MGF currently.
Verify by touching the radiator hoses just a few minutes after start from cold.
If the warm up early, then the thermostat doesn't do what it should.

HTH
Dieter
Dieter K.

"and they said always take the engine up to at least 2500 rpm immediately after starting, to reduce the stress on the cams."

I'm not saying this is wrong or trying to wind you up but surely there is very low lubrication at the top of the engine at this very occasion? I would have thought that the stress on cams is proportional to the speed so is higher at higher revs. If this 2500 rpm thing is good why don't the car makers program the ECU to do it?

If you want to be nice to your car let the engine have the heat for the first couple of mins rather than putting the heater on full blast - probably takes the conviction of a monk on a morning like this though :)

Tony

that's an interesting technical note about the VVC, with the water/oil heat exchanger. All the other engines can upgrade to W30 oil except the VVC which must have W40. What about the historical incidence of HGF on the VVC?
Gary

Thanks for all of your answers.

I will certainly consider the oil/water cooler (heater?). Where does it fit? I know the normal air oil coolers mount at the front of the car.

On a similar vein, I know I need to fit a new rad, but if I fit an uprated one from Mike Satur, won't the extra cooling capacity/ability make the situation worse in the winter?

I can see benefits in the summer or when "using the performance to the full, Officer" but surely more cooling means the engine will stay colder in the winter?
Kevins

Gary, the historical incidence of HGF in MPi versus VVC is about equal - see http://www.shame.4mg.com/

Kevin, the oil/water heat exchanger/cooler is located on the back of the block under the inlet manifold. Dave's had this fitted on his VVC - I'm sure that he can fill in more of the details than I can. It is quite a straightforward fit, in that the coils have to be relocated, but it is entirely possible...

An alternative solution would be to fit a Mocal Laminova 180mm oil/water cooler - www.eliseparts.com do a fitting kit for the Elise that could be easily adapted for the MGF. The advantages are the far superior heat handling capacity, plus you can mount it just about anywhere you want to.
Rob Bell

>On a similar vein, I know I need to fit a new rad, but
>if I fit an uprated one from Mike Satur, won't the extra
>cooling capacity/ability make the situation worse in the winter?

Nope, if the thermostat is working right then there will be no diffrence to the engine

>I can see benefits in the summer or when "using the
>performance to the full, Officer" but surely more
>cooling means the engine will stay colder in the winter?

the oil/water cooler is a heat exchanger. Most of the heat in the engine is generated in the head, with less on the liners and very little in the bearings. The oil cools the bearings but to reach the bearings for the cam has to run through the head. The water/oil cooler give a much larger surface for the water and oil to exchange heat over - so the oil should cool to the water temp in high oil temp conditions and heat to the water temp in low temp conditions
Will Munns

Hi,

Tony, I dunno, I'm only repeating what I remember from the book. I think the theory is that grinding the cam/follower surface together at very low speed with full spring pressure is bad, better to get a little inertia going so that the cam lobes are spared this sufferring. I think that the more gentle lift of the cam ramps is OK, it's up against the lobes where the damage occurs.

There is a certain speed and cam lift combination at about half lift where the valve is no longer being pushed open by the cam (it's already hurtling hell-bent into the cylinder), but the valve spring is attempting to hold the valve against it's inertia back against the cam profile. So the only pressure at this point is the excess capacity of the spring. If there's insignificant inertia then the cam/follower gets very high rubbing pressure. (Sorry Dieter, this is difficult enough to explain in English!)

Or this might be all theoretical cobblers.

Regards, Kes.
Kes

"Or this might be all theoretical cobblers" :)

I see what you mean - once on their way the valves offer a bit less resistance than being slowly and gratingly pushed.

Tony
Tony

Sounds like it could be right for the cam, but compleatly disregarding the effect on the rest of the engine (as you might expect for a cam shaft maker)
Will Munns

But don't these instructions apply to the first build of the engine, rather than the day to day useage thereafter? In any case, 2,500rpm is not particularly excessive...
Rob Bell

The cam wear issue probably has more to do with the fact that at low speeds a hydro-dynamic oil film is not built up between the moving parts as occurs in a normal crank bearing at speed. When spinning the crank is rotating in a sea of oil, having been lifted away from the surface of the bearing by the aformentioned hydro-dynamic oil pressure. Clearly at almost zero relative rotational speed there can be virtually no hydro-dynamic oil pressure and the two metals can actually come into intimate contact and wear. This would be especially true in a new engine before all the hills and valleys have levelled off during the running-in period.
This all sounds very good and plausible...........I wonder if it is correct or merely the rantings of a frustrated engineer.

Regards....David
d mottram

WRT the contact force between the surface of the cam and the cam follower and how it relates to the speed of the engine:

It would seem to me that the force results from two quite distinct functions performed by the camshaft.

Firstly it has to compress the spring. The force it sees from this is a force increasing as lift increases and then decreaseing as lift diminishes. It is purely a function of the amount of lift and not the rate at which that change of lift occurs. Thus it would be independent of RPM.

Secondly the cam has to move the actual valve and its assoctiated paraphenalia (and to a smaller extent the centre of mass of the compressing spring. The force it sees from this function depends upon how rapidly it changes the speed of the valve ie the rate of acceleration of the valve. For a given camshaft this acceleration is dependent upon the time during which the rotation of the cam and hence lift of the valve takes place. Thus it depends very much on how fast the engine is turning. As to whether the function is linear or to some power only the engineers can attest , but I suspect it would be to a higher power than one (linear); and hence big revs would really punish the cam/follower interface. This has been my experience at least. Clearly a different cam with a steeper ramp would accelerate the valve more quickly and thus suffer bigger forces, and heavier valves offer more inertia and hence need more force etc.

As I said earlier.....seems logical!

Regards...David
d mottram

Advice on break in but note engine needs to be up to temp

http://www.mototuneusa.com/break_in_secrets.htm

Cams can be broken in at 2-3k revs then varied

Once up to temp "drive your new car like you stole it"!

IMO until warm (Oil 85c) the car should be driven not to idle labour or over rev.

If you have too much cooling you can block part of airflow to rad in winter, as at speed the cold air is very effective at cooling, and this will help keep oil and water temp up.

Ester based oils with 10-30% ester will form a protective oil film, no metal to metal contact.

Paul
Paul

Going back to oil temperature - Kes asked 'Can an oil be too cold if it is capable of circulating freely?'

I would guess that it doesn't matter,as long as it gets hot enough to burn off condensation. With the MGF, I think it's more a point of making sure the head and block are up to temperature - which shouldn't be too long after water temp stabilises.
After that, thermostat action is probably more critcal than oil temp - and the driver has no real control over that.

Aircraft (piston) engines need to work very hard soon after startup-up to take-off and climb. Planes like the Lancaster carried some 38 gallons (170 litres) of oil in each engine nacelle. You can bet this wasn't up to temperature at the start of take-off / climb - which would need full power with a heavy bomb/fuel load.
Steve

<.. merely the rantings of a frustrated engineer ..>

Ah, you've sussed me!
Kes

Anyone mention Fawlty Towers

The Germans in WWII found that the oil of castorbeans made a synthetic lubricant, until it oxidized and then turned into crud. What they later discovered was that the castorbean contained a natural ester and glycerine; it was the glycerine that accelerated oxidation. When they separated the castor acid from the glycerine, and then reacted an alcohol with the acid, they came up with one of the first ester lubricants known to man. What they didn't know was that secretly, Standard Oil and Union Carbide were doing the same thing for the Allies and had made various synthetic lubricants before the Germans really needed them.

The oil temp in the engine will be a lot higher and the HTHS for an oil at 150c is of interest.

Paul
Paul

I presume this oil was Castrol R which smells so magnificent when burning in an engine?
d mottram

was it the Germans who found you could make some sort of really dodgy poison out of the beans as used by terrorists recently(probably got that wrong though - might need a bit more coffee!)
Tony

This thread was discussed between 30/11/2004 and 02/12/2004

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