8 replies to this topic

[Nev]

Hi guys,

 

Does anyone know which way the oil flows through the VXT water/oil heat exhange matrix? In other words, does the hot oil coming from the engine pump enter the left end or the right end (when looking at it from the boot)?

 

The reason I ask is that I am thinking of drilling and tapping an oil sender into one of those huge banjo bolts that feed the heat exhange matrix. Natually I'd like to put the sensor on the inlet (to see the temps before they oil is cooled (not that the cooler does a huge amount I am sure!)).

 

Thanks in advance.

 

N+N.

Edited by Nev, 30 March 2016 - 11:27 AM.

[Zoobeef]

Done a bit of go ogling and can't see anywhere that says. 

One way is to undo both banjos and put the pipe ends in bottles or bags. Then turn it over on the starter. (Coilpack unplugged)

[fezzasus]

Personally, I would instrument both ends, then you can see how efficient the oil cooler is, or (depending how you look at it) how much heat the engine is putting into the oil.

 

*note, while it's entirely dependent on oil cooler design, oil tends to follow water temperature very closely which implies most oil coolers are sufficient.

[Nev]

Done a bit of go ogling and can't see anywhere that says. 

One way is to undo both banjos and put the pipe ends in bottles or bags. Then turn it over on the starter. (Coilpack unplugged)

 

Thanks Mark, was hoping to avoid this, as access is very poor to 1 of the banjo (the right hand side) and am not so keen on 50 PSI of shooting about unless it vital.

[Arno]

From this picture off of an Astra I'd say that the left banjo on the oil filter housing is the return from the cooler and the right banjo is the feed.

 

When the oil is cold the thermostat is open and oil is allowed to flow directly to the filter, bypassing the cooler. Once the oil heats up the thermostat closes the bypass and the cooler gets the main flow.

 

 

Bye, Arno.

[Nev]

Personally, I would instrument both ends, then you can see how efficient the oil cooler is, or (depending how you look at it) how much heat the engine is putting into the oil.

 

*note, while it's entirely dependent on oil cooler design, oil tends to follow water temperature very closely which implies most oil coolers are sufficient.

 

I imagine the temp drop accross the matrix is barely even a couple of degrees once warmed up, and I hope you are right about the water + oil temps being roughly parallel. However I do have a slight reason to think my oil might be getting rather hot.  

[fezzasus]

 

Personally, I would instrument both ends, then you can see how efficient the oil cooler is, or (depending how you look at it) how much heat the engine is putting into the oil.

 

*note, while it's entirely dependent on oil cooler design, oil tends to follow water temperature very closely which implies most oil coolers are sufficient.

 

I imagine the temp drop accross the matrix is barely even a couple of degrees once warmed up, and I hope you are right about the water + oil temps being roughly parallel. However I do have a slight reason to think my oil might be getting rather hot.  

 

 

This is based on seeing hundreds of instrumented oil approval engine test results - they all have the same trend - bulk oil temperature is limited by coolant temperature.

 

However, don't think of the impact of temperature on bulk oil. Sump oil sampling shows that the bulk oil degrades very little. It's the small amount of oil residing in the piston groove and turbocharger bearings which is really at risk.

[Nev]

It's the small amount of oil residing in the piston groove and turbocharger bearings which is really at risk.

 

 

I can imagine when oil gets trapped in the piston grooves for even 5 secs it will see some very high local temps, maybe even 500 degree ?  

[fezzasus]

 

It's the small amount of oil residing in the piston groove and turbocharger bearings which is really at risk.

 

 

I can imagine when oil gets trapped in the piston grooves for even 5 secs it will see some very high local temps, maybe even 500 degree ?  

 

 

Typically 250-300 for the top groove depending on the engine, fuel and operating conditions. Residence time is around 60 seconds but that's very sensitive to the technique applied to measure it (usually they add a material to the sump and sample the ring groove to measure time to equilibrium) and interpretation of residence time - i've seen values as high as 26 minutes when they assume maximum residence time rather than average.

 

These measurements formed the basis of the TEOST oil oxidation tests used in american oil claims - you can describe the oil as sitting in two reactors; one high volume, low temperature (sump), one low volume very high temperature (piston or TC). Unfortunately the resulting tests aren't particularly useful, however the thought process is relatively sound, just over simplified.

Edited by fezzasus, 30 March 2016 - 02:20 PM.