Oil cooler and thermostat
Discussion
Sparked by a thread in the Tuscan section, has anyone fitted a thermostatic bypass on their oil cooler?
Would this lead to dramatically reduced oil warm up times? On the face of it I reckon it would as presently all the oil passes through the cooler (which is fed from the cold radiator outlet) at all times, irrespective oil temperature.
Would this lead to dramatically reduced oil warm up times? On the face of it I reckon it would as presently all the oil passes through the cooler (which is fed from the cold radiator outlet) at all times, irrespective oil temperature.
Dave i have been looking at this the main problem is the oil cooler is in a crap space with very little room for a stat i dont think Dom's argument stands up too well as the stat would bypass the cooler not cause a restriction also the large bore oil hoses are fitted to the cooler with reducers so the cooler forms a restriction.
Ian
Ian
Also, not so sure that I agree with the "restriction" argument either.
I'm pretty sure that an oilstat could be fitted in somewhere nearby quite easily. They're not big after all. You might need a couple of custom hoses made, but they're not difficult to source. You'd have to make sure that the stat bypass circuit had the same size restrictor plates in as on the cooler though so as not to alter the lub system performance.
Not only would the oil warm quicker, it would maintain the oil >80degC which would improve the oil perfomance in colder weather. Driving in the winter regularly sees the oil struggle to get above 50 degC, which is not good for the engine at all.
More info on them here
I'm pretty sure that an oilstat could be fitted in somewhere nearby quite easily. They're not big after all. You might need a couple of custom hoses made, but they're not difficult to source. You'd have to make sure that the stat bypass circuit had the same size restrictor plates in as on the cooler though so as not to alter the lub system performance.
Not only would the oil warm quicker, it would maintain the oil >80degC which would improve the oil perfomance in colder weather. Driving in the winter regularly sees the oil struggle to get above 50 degC, which is not good for the engine at all.
More info on them here
Edited by dvs_dave on Thursday 29th October 21:43
I would definitely think it's not a complicated job mechanically. I worry though and perhaps I need setting straight here, that the oil pressure would be affected in the engine. The way I see that happening is if you imagine the engine is rather like a shower head. If you block up some holes, other holes get higher pressure, but if you enlarge some holes the pressure to the others reduces.
I don't really know whether the oil circuit is a series of branch 'T's off a single line. Or whether there is a distribution and division point after the pump. I suspect the latter. In which case altering the pressure in any way will affect the entire engine I think.
I also suspect that the pressure switch is after or near the pump, but others will know. In which case you would still get the same readings, but the altered pressures (which I keep banging on about
) would still be there and potentially wrecking the engine without any obvious indication.
It's just the same principal as balancing radiators on a central heating system. AFAIK. Except in this case without lock-shield valves we’re dependent on the dear designer to ensure the pressures are equalised throughout.
I hope to be wrong because in that case, I am 100% in - I think it's a really sensible plan for all the reasons you guys have given.
I don't really know whether the oil circuit is a series of branch 'T's off a single line. Or whether there is a distribution and division point after the pump. I suspect the latter. In which case altering the pressure in any way will affect the entire engine I think.
I also suspect that the pressure switch is after or near the pump, but others will know. In which case you would still get the same readings, but the altered pressures (which I keep banging on about
) would still be there and potentially wrecking the engine without any obvious indication.It's just the same principal as balancing radiators on a central heating system. AFAIK. Except in this case without lock-shield valves we’re dependent on the dear designer to ensure the pressures are equalised throughout.
I hope to be wrong because in that case, I am 100% in - I think it's a really sensible plan for all the reasons you guys have given.
dvs_dave said:
You'd have to make sure that the stat bypass circuit had the same size restrictor plates in as on the cooler though so as not to alter the lub system performance.
I'm struggling to think of any good reason for deliberately restricting the flow through the oil cooler. I assume it's a full flow cooler so this is restricting the oil supply to the whole engine. If so, that seems fundamentally daft and I'm curious to know what is the thinking behind it.GreenV8S - I don't think that's what was meant. The idea was to add a thermostatic bypass circuit so that the oil would only flow through the oil cooler when a given temperature was reached. Before that temperature was reached the oil would circulate round the feed and return to the cooler via the propsed thermostatic bypass.
The problem and the unknown factor really is what resistance to flow should the bypass circuit needs to offer to "match" the resistance to flow offered by the cooler. Thereby not upsetting pressures elsewhere. If someone had the right equipment to measure the current volume passing through the cooler; then that value could be acheived in the bypass loop. With that approach, I can't see an issue with this mod in principal.
Can you?
The problem and the unknown factor really is what resistance to flow should the bypass circuit needs to offer to "match" the resistance to flow offered by the cooler. Thereby not upsetting pressures elsewhere. If someone had the right equipment to measure the current volume passing through the cooler; then that value could be acheived in the bypass loop. With that approach, I can't see an issue with this mod in principal.
Can you?
AG Tuscan II S said:
GreenV8S - I don't think that's what was meant. The idea was to add a thermostatic bypass circuit so that the oil would only flow through the oil cooler when a given temperature was reached. Before that temperature was reached the oil would circulate round the feed and return to the cooler via the propsed thermostatic bypass.
The problem and the unknown factor really is what resistance to flow should the bypass circuit needs to offer to "match" the resistance to flow offered by the cooler. Thereby not upsetting pressures elsewhere. If someone had the right equipment to measure the current volume passing through the cooler; then that value could be acheived in the bypass loop. With that approach, I can't see an issue with this mod in principal.
Can you?
Upsetting the flow elsewhere is only an issue if the oil cooler is in parallel with [part of] the engine circuit, which would be a very strange way to design it. The conventional approach is to have pump->filter->cooler->engine or pump->cooler->filter->engine, with a pressure relief valve somewhere between the pump and the engine. In that conventional approach, I can't think of any reason for deliberately restricting the flow at any point. Perhaps there is a good reason I haven't thought of, I'm open to suggestions.The problem and the unknown factor really is what resistance to flow should the bypass circuit needs to offer to "match" the resistance to flow offered by the cooler. Thereby not upsetting pressures elsewhere. If someone had the right equipment to measure the current volume passing through the cooler; then that value could be acheived in the bypass loop. With that approach, I can't see an issue with this mod in principal.
Can you?
Just a thought, not too familiar with the pipework layout in the Tuscan engine bay (no doubt I'll venture in there someday) but as a compromise a thermostat on the water side of the oil cooler would at least let the oil roughly match the water temp. Maybe not ideal for racing etc but if it,s a simple mod it's better than the oil staying at 50 which mine does at this time of year.
Prepared to be shot down in flames on this one - comments please.
PS I think we need to nail down the ideal oil temp we are trying to achieve, some posts seem to thing 90 is high?
Prepared to be shot down in flames on this one - comments please.
PS I think we need to nail down the ideal oil temp we are trying to achieve, some posts seem to thing 90 is high?
The oil cooler is a full flow type for both the oil and coolant circuits. When the coolant temp is low, there's obviously no flow through the coolant side as the engine water thermostat is closed, so initially the oil isn't being cooled. The problem arises when the water thermostat opens allowing water flow through the cooler, it cools the oil too much so prolonging warm up (or it never getting there in cold weather).
It's generally regarded that ideal oil operating temperature is 80 to 100 deg C. The quicker you can get it there, and keep it in that range the better it is for your engine. The more I look into this, the more it makes me wonder what additional wear is occurring whilst the oil is below 80deg C, which for a lot of the time, especially on the motorway, it is!
Where in the oil circuit is the cooler located? AFAIK it goes Scavenge pump > oil reservoir > pressure pump > filter > engine, with the cooler somewhere in between. I would hazard a guess at it being between the pressure pump and the filter?
One of these units looks dead easy to install, and I can't see it having any adverse affects on the oil flow whatsoever, other than it either offering less restriction in bypass mode (good) or equalling the cooler resistance in cooling mode.
It's generally regarded that ideal oil operating temperature is 80 to 100 deg C. The quicker you can get it there, and keep it in that range the better it is for your engine. The more I look into this, the more it makes me wonder what additional wear is occurring whilst the oil is below 80deg C, which for a lot of the time, especially on the motorway, it is!
Where in the oil circuit is the cooler located? AFAIK it goes Scavenge pump > oil reservoir > pressure pump > filter > engine, with the cooler somewhere in between. I would hazard a guess at it being between the pressure pump and the filter?
One of these units looks dead easy to install, and I can't see it having any adverse affects on the oil flow whatsoever, other than it either offering less restriction in bypass mode (good) or equalling the cooler resistance in cooling mode.
Edited by dvs_dave on Monday 2nd November 13:53
dvs_dave said:
The oil cooler is a full flow type for both the oil and coolant circuits.
Is it an oil-to-water cooler? In that case it's probably improving the oil warm-up time since the water typically warms up a lot quicker than the oil. In that case you also would probably not need a thermostat since the coolant temp should be around 85-90C so the oil will not be cooled below that level, and that's a good temperature for the oil to be pulled down to.GreenV8S said:
dvs_dave said:
The oil cooler is a full flow type for both the oil and coolant circuits.
Is it an oil-to-water cooler? In that case it's probably improving the oil warm-up time since the water typically warms up a lot quicker than the oil. In that case you also would probably not need a thermostat since the coolant temp should be around 85-90C so the oil will not be cooled below that level, and that's a good temperature for the oil to be pulled down to.The oil thermostat would prevent the oil from going below the ideal minimum of 80degC which with the current design it doesn't, especially in colder weather.
I agree. On the face of it, it's a crap design and for the sake of a £50 oil thermostat a bit of a mystery as to why they weren't fitted at the factory. Especially when you consider that oil temp is known to be critical to Speed Six longevity.
Having googled the subject a fair bit, virtually every oil cooler application, OEM or aftermarket has a thermostat fitted.
Time for a modification me thinks.......
Dom,
Will this invalidate my engine warranty?
Having googled the subject a fair bit, virtually every oil cooler application, OEM or aftermarket has a thermostat fitted.
Time for a modification me thinks.......
Dom,
Will this invalidate my engine warranty?
dvs_dave said:
I agree. On the face of it, it's a crap design and for the sake of a £50 oil thermostat a bit of a mystery as to why they weren't fitted at the factory. Especially when you consider that oil temp is known to be critical to Speed Six longevity.
Given that this is known, the oil-to-water cooler could be very valuable in improving oil warm-up times, if it was installed in the right place. Is there any prospect at all of plumbing it into the hot side of the rad instead? As it is, and without a stat, I'd be inclined to agree it's worse than useless.Think I might have been partially responsible for starting this debate 
on the Tuscan forum. If it wasn't on the cold side of the rad it would be a totally waste of time, 'cos the water would be hotter than the oil (depending upon the sensor positions) once warmed up and in traffic that's when you need the oil cooling by the fans operating on the water in the rad. No other way of cooling the engine oil as I see it, obviously eventually a state of equilibrium exists.
I quite like the idea of bypassing the cooler to aid warm up.... seem to make sense to me.... or am I being thick again.
on the Tuscan forum. If it wasn't on the cold side of the rad it would be a totally waste of time, 'cos the water would be hotter than the oil (depending upon the sensor positions) once warmed up and in traffic that's when you need the oil cooling by the fans operating on the water in the rad. No other way of cooling the engine oil as I see it, obviously eventually a state of equilibrium exists.I quite like the idea of bypassing the cooler to aid warm up.... seem to make sense to me.... or am I being thick again.
glow worm said:
Think I might have been partially responsible for starting this debate on the Tuscan forum. If it wasn't on the cold side of the rad it would be a totally waste of time, 'cos the water would be hotter than the oil (depending upon the sensor positions) once warmed up and in traffic that's when you need the oil cooling by the fans operating on the water in the rad. No other way of cooling the engine oil as I see it, obviously eventually a state of equilibrium exists.
I quite like the idea of bypassing the cooler to aid warm up.... seem to make sense to me.... or am I being thick again.
I disagree. You want to cool the oil down to roughly the water temperature. If you manage that, cooling it further is not just unnecessary, it's harmful. If you have an oil-to-water cooler, the top hose is the right place to put it. If you're trying to use an oil-to-water cooler to prevent the engine overheating at idle then you're barking completely up the wrong tree. on the Tuscan forum. If it wasn't on the cold side of the rad it would be a totally waste of time, 'cos the water would be hotter than the oil (depending upon the sensor positions) once warmed up and in traffic that's when you need the oil cooling by the fans operating on the water in the rad. No other way of cooling the engine oil as I see it, obviously eventually a state of equilibrium exists.I quite like the idea of bypassing the cooler to aid warm up.... seem to make sense to me.... or am I being thick again.
In normal running oil temp always shows 10 degrees LOWER than water, I assume the sensors are in similiar locations with respect to the engine. So the only point of an oil cooler is if it sits after water has been cooled by the radiator, so there's a temperature differential...that's the way I see it in normal running.... but I may be wrong. Am I right in assuming water is a better conductor of heat than oil, hence cools it more effectively ???
Warming up is a different issue.
Come on Dom help us out !!!
Warming up is a different issue.
Come on Dom help us out !!!
Edited by glow worm on Monday 2nd November 21:17
glow worm said:
In normal running oil temp always shows 10 degrees LOWER than water, I assume the sensors are in similiar locations with respect to the engine. So the only point of an oil cooler is if it sits after water has been cooled by the radiator, so there's a temperature differential...that's the way I see it in normal running.... but I may be wrong.
I suspect you're seeing that because in your setup the oil is being over-cooled because the cooler is on the rad return and there is no stat. It is certainly not normal to have the oil cooler than the coolant, and it's not desirable, and if for some bizarre reason you had it you certainly wouldn't be fitting an oil cooler to get the oil even colder.Gassing Station | Speed Six Engine | Top of Page | What's New | My Stuff