Understanding HTHS

[1JZ_E46]

Originally Posted By: Gokhan
As Shannow pointed out and CATERHAM empirically demonstrated, oil pressure (and flow) is also dictated by HTHSV, not KV100, as the flow through the bearing clearances is dictated by HTHSV, not KV100.


Agreed. I would say both KV100 and HTHS play a roll. For example, KV100 would be a better indicator as to the volume of oil pumped through the piston oil squirters for a given temperature.

 

[JAG]

Much good has already been posted. I will just point out that piston ring temperature in a warmed up engine are typically around 250C. Crazy hot.

 

[Gokhan]

This is how I see it:

HTHSV: Wear protection in bearings, fuel economy, and oil pressure/flow at normal operating temperature
KV100: Mostly irrelevant except for calculating other quantities, such as viscosity index
KV40: Cold flow, warm-up fuel economy
Base-oil viscosity (not disclosed but strongly correlated with x in xW-y): Wear protection in the valvetrain, timing chain, and piston rings
y in xW-y: Mostly irrelevant
x in xW-y: Correlates well with base-oil viscosity (wear protection in the valvetrain, timing chain, and piston rings), extreme-cold starts, correlates with cold fuel economy but not as much as KV40 and viscosity index
VI (viscosity index): Correlates with cold fuel economy and amount of VII (viscosity-index improver)
A_Harman index (calculated): Correlates with amount of VII but not an absolute determinant, as VII doesn't fully shear in HTHSV conditions and different VIIs shear differently
Amount of moly and other AW/EP/FM (antiwear/extreme pressure/friction modifier) additives: Wear protection in the valvetrain, timing chain, and piston rings, correlates with fuel economy

 

[Shannow]

Originally Posted By: 1JZ_E46
Agreed. I would say both KV100 and HTHS play a roll. For example, KV100 would be a better indicator as to the volume of oil pumped through the piston oil squirters for a given temperature.


Squirters are pressure/density, with limited viscosity impact.

Did a thread on that a while back, using some actual figures.

https://bobistheoilguy.com/forums/ubbthreads.php/topics/4175771/Re:_Nozzle_Flow_Versus_Pressur

Will have to fix the Photobucket mess-up over the weekend.

 

[BrocLuno]

Originally Posted By: robertcope
Soooo... I'm probably doing the smart thing running Red Line 10w30 (3.5 HTHS) in my S2K (9K RPM) and NSX (8500 RPM)? Technically they don't require anything special per Honda, ie 10w30 API SG Energy Conserving.

Is there ever any harm in running a higher HTHS than required, other than fuel economy?


Almost never any negatives other than fuel economy.

And if you're zinging that motor to 8,500 - I'd bet you are not to concerned by fuel economy

 

[Gokhan]

Originally Posted By: Shannow
Originally Posted By: 1JZ_E46
Agreed. I would say both KV100 and HTHS play a roll. For example, KV100 would be a better indicator as to the volume of oil pumped through the piston oil squirters for a given temperature.

Squirters are pressure/density, with limited viscosity impact.

Did a thread on that a while back, using some actual figures.

https://bobistheoilguy.com/forums/ubbthreads.php/topics/4175771/Re:_Nozzle_Flow_Versus_Pressur

Will have to fix the Photobucket mess-up over the weekend.

Photobucket has ruined the Internet for many. It's a shame.

I use Google Photos. Use a public album and append ?.jpg or ?.png etc. to the image link and you can then post the image here and other Web sites.

Yeah, since the laminar-flow rate through the nozzle goes as P_gauge/viscosity and P_gauge increases with viscosity for small to moderate RPMs in normal operating temperature, I would think that the nozzle flow would be roughly independent of the viscosity, as viscosity cancels out in numerator and denominator. However, the output nozzle speed will get a boost from the gauge pressure due to Bernoulli's principle: Output nozzle speed squared = Input nozzle speed squared + 2 x gauge pressure / density.

Quote:
Will have to fix the Photobucket mess-up over the weekend.

You mean you will pay the $400 ransom or you'll do what your Aussie pal Mel Gibson did in the so-named movie?

 

[ZeeOSix]

Originally Posted By: Gokhan
Quote:
Will have to fix the Photobucket mess-up over the weekend.

You mean you will pay the $400 ransom?

Just upload the same photos through the BITOG photo attachment tool. Then they reside on the BITOG server.

 

[Shannow]

Originally Posted By: Gokhan
You mean you will pay the $400 ransom or you'll do what your Aussie pal Mel Gibson did in the so-named movie?

No, never...

On an as needs basis, I grab the photos off PB if I don't have them on the hard drive, then upload through BITOG pics.

 

[CR94]

Originally Posted By: BrocLuno

... Is there ever any harm in running a higher HTHS than required, other than fuel economy? ...
1. The needless extra viscous drag that hurts fuel economy hurts power output similarly.
2. Slightly higher oil temperature, other things being equal.

 

[SonofJoe]

It's worth making the point that low HTHS oils, coupled with high sump temperatures does not axiomatically mean excessive bearing wear.

There are a couple of industry standard engine tests I used to run (the American Sequence IIIG test and the European Peugeot TU5 test) where the bulk oil temperature is artificially maintained at 150°C and the engine continuously thrashed within an inch of its life for a few days. Under such conditions, you would expect the oil temperature exiting the bearing to be wildly hot and the oil viscosity to be ridiculously low! I had many a test fail on oxidation & strip-related viscocity increase or oil loss but I never once lost an engine to bearing failure or excessive wear.

 

[ZeeOSix]

Originally Posted By: SonofJoe
It's worth making the point that low HTHS oils, coupled with high sump temperatures does not axiomatically mean excessive bearing wear.

There are a couple of industry standard engine tests I used to run (the American Sequence IIIG test and the European Peugeot TU5 test) where the bulk oil temperature is artificially maintained at 150°C and the engine continuously thrashed within an inch of its life for a few days. Under such conditions, you would expect the oil temperature exiting the bearing to be wildly hot and the oil viscosity to be ridiculously low! I had many a test fail on oxidation & strip-related viscocity increase or oil loss but I never once lost an engine to bearing failure or excessive wear.


How low of a HTHS oil was used in those engine thrashing tests?

 

[SonofJoe]

Originally Posted By: ZeeOSix
Originally Posted By: SonofJoe
It's worth making the point that low HTHS oils, coupled with high sump temperatures does not axiomatically mean excessive bearing wear.

There are a couple of industry standard engine tests I used to run (the American Sequence IIIG test and the European Peugeot TU5 test) where the bulk oil temperature is artificially maintained at 150°C and the engine continuously thrashed within an inch of its life for a few days. Under such conditions, you would expect the oil temperature exiting the bearing to be wildly hot and the oil viscosity to be ridiculously low! I had many a test fail on oxidation & strip-related viscocity increase or oil loss but I never once lost an engine to bearing failure or excessive wear.


How low of a HTHS oil was used in those engine thrashing tests?



Every oil on the market that claims API SN/GF-5 has successfully negotiated the IIIG. Every oil that carries any sort of ACEA claim has gone through the TU5. So that's all 20 weight oils and probably any 16 weights too.

 

[userfriendly]

With a 150C bulk oil temperature, the viscosity would be close to the published HTHS depending on its Harmon index which takes in density, if I'm reading this thread correctly.
With the oil thinned out from heat, normally we would see a drop in oil pressure. If the oil pressure was also kept artificially high, then the test does not represent real world conditions.

I would imagine that the flow through the bearing space would be high regardless of delivery pressure, and therefore oil temperature increase low.

 

[SonofJoe]

Originally Posted By: userfriendly
With a 150C bulk oil temperature, the viscosity would be close to the published HTHS depending on its Harmon index which takes in density, if I'm reading this thread correctly.
With the oil thinned out from heat, normally we would see a drop in oil pressure. If the oil pressure was also kept artificially high, then the test does not represent real world conditions.

I would imagine that the flow through the bearing space would be high regardless of delivery pressure, and therefore oil temperature increase low.



It's been a while now since I played the formulation game but my recollection was that the IIIG & TU5 oil delivery systems were absolutely stock. The oil pressure was what it was for the constant volume pump to chugg through whatever oil flow conditions dictated. Remember both of these tests are primarily focussed on oil viscosity INCREASE towards the end of test so any attempt to artificially 'boost' oil pressure could conceivably prematurely crash a very expensive test (to give you some idea, I've had IIIG tests where the end-of-test KV100 comes back from the lab as 'too viscous to measure' which usually means > 5000 cst!).

On a philosophical note, you can easily make the argument that ALL engine tests are so divorced from reality that they are utterly meaningless. However, the auto industry moves so quickly that no one has sufficient time to judge oil quality by wide ranging global field trials. So engine testing is where it's all at and probably always will be.

 

[ZeeOSix]

Originally Posted By: SonofJoe
It's been a while now since I played the formulation game but my recollection was that the IIIG & TU5 oil delivery systems were absolutely stock. The oil pressure was what it was for the constant volume pump to chugg through whatever oil flow conditions dictated. Remember both of these tests are primarily focussed on oil viscosity INCREASE towards the end of test so any attempt to artificially 'boost' oil pressure could conceivably prematurely crash a very expensive test (to give you some idea, I've had IIIG tests where the end-of-test KV100 comes back from the lab as 'too viscous to measure' which usually means > 5000 cst!).


Wow, if the oil thickened that much during the test the oil pressure would naturally rise due to the PD pump until its pressure relief valve started to open.

Were they using oil with high NOACK in those tests?

 

[userfriendly]

Were the engines loaded during the tests, or just running at high a RPM at an elevated temperature in an attempt to oxidize the oil?
It seems to me that an engine in front of an 8 or 10 speed automatic transmission could survive with lower HTHS than in front of a standard transmission with fewer speeds.

In the automatic example, there would be less RPM drop between shifts and human input eliminated.

 

[SonofJoe]

Originally Posted By: ZeeOSix
Originally Posted By: SonofJoe
It's been a while now since I played the formulation game but my recollection was that the IIIG & TU5 oil delivery systems were absolutely stock. The oil pressure was what it was for the constant volume pump to chugg through whatever oil flow conditions dictated. Remember both of these tests are primarily focussed on oil viscosity INCREASE towards the end of test so any attempt to artificially 'boost' oil pressure could conceivably prematurely crash a very expensive test (to give you some idea, I've had IIIG tests where the end-of-test KV100 comes back from the lab as 'too viscous to measure' which usually means > 5000 cst!).


Wow, if the oil thickened that much during the test the oil pressure would naturally rise due to the PD pump until its pressure relief valve started to open.

Were they using oil with high NOACK in those tests?



It's less a Noack thing and more of a 'trying to pass the IIIG using Group I mineral base oils' thing. Getting such oils to remain stable under IIIG conditions much beyond 80 hours is very hard work...and the IIIG runs for 100 hours. In that last few hours of the test, when all oxidation control goes out of the window, the oil's viscocity can rocket up at an exponential rate (as per Arrhenius's equation). I did pull the trick off a few times though...

 

[SonofJoe]

Originally Posted By: userfriendly
Were the engines loaded during the tests, or just running at high a RPM at an elevated temperature in an attempt to oxidize the oil?
It seems to me that an engine in front of an 8 or 10 speed automatic transmission could survive with lower HTHS than in front of a standard transmission with fewer speeds.

In the automatic example, there would be less RPM drop between shifts and human input eliminated.


These tests are all connected up to a dynamometer so that the engines run under high load. It's not enough to just whack the oil temperature up to 150°C. You need to load up the engine to get the high rate of very hot, reactive blow-by gas which is the stuff that does most to knacker your oil.

 

[Shannow]

Back when I was in Uni, I had access to the entire SAE papers on microfiche.

WRT to the "too viscous to measure", there were a couple of papers on the failure of 10W40 multigrades, where the engines failed on startup, and the oil had to be "cut" out of the sumps for analysis.

Presumably those engines were still operating at the point that they were shut down, as was the engine in the engine test operating at the time that the sample was taken, and cooled and become untestable.

If the viscosity is increasing, one wouldn't expect bearing failure

 

[SonofJoe]

Originally Posted By: Shannow
Back when I was in Uni, I had access to the entire SAE papers on microfiche.

WRT to the "too viscous to measure", there were a couple of papers on the failure of 10W40 multigrades, where the engines failed on startup, and the oil had to be "cut" out of the sumps for analysis.

Presumably those engines were still operating at the point that they were shut down, as was the engine in the engine test operating at the time that the sample was taken, and cooled and become untestable.

If the viscosity is increasing, one wouldn't expect bearing failure




It brings back ghastly memories of rock solid high ethylene VIIs having to be dug out of rail cars. Not my fault on that occasion but you try to look away because you know some poor schmuck in getting his love spuds put through the wringer as a result!

Regarding the IIIG, yes, as the oil's viscosity rises, as a result of oxidation, it mitigates against bearing failure. However, this is the exceptional, and more often that not, testing failing case.

To pass the IIIG to SN/GF-5, you have to get through the test with a maximum of 150% KV40 increase (KV100 percent increase is lower if memory serves). Most passing oils pass with nowhere near this level of vis increase. Even if the test pass is borderline it will be the result of a kick-up in the dying hours if the test.

The point of saying all this, is that all of those 0W20's & 5W20's that you find in the market place went through the the 100 hour/150°C/high speed/high load Sequence IIIG test and spent the bulk of the test time in their 'natural' unoxidised, low HTHS state...and STILL got through the entire test without the engine dropping dead and STILL meeting the test wear limits.

Like I said in the beginning, low HTHS isn't AUTOMATICALLY the killer of bearings that people fear it might be.