Oil Viscosity Effect On Oil Jet Cooling ....

[JSRT4]

Hi everyone, I have an 02 Honda S2000 which uses Oil jets at the bottom of the crankcase to spray oil under the pistons for extra cooling and lubrication. Apparently Honda changed the design of the jets as some vehicles exhibited oil related failures under hard driving conditions. My car is listed as not having the upgraded oil jet design, probably missing the part changeover VIN list by a few hundred vehicles. I've read that the upgraded oil jets have 4 holes instead of 2 holes, and the holes are smaller in size. I would think they would flow more oil and at higher pressure if the description of the design upgrade was correct.

I question the effect of a thicker oil viscosity on the spray patterns of oil jets. Honda lists a 10w30 oil and a 5w-40 viscosity that is suitable for our engine. I have made the choice to run the 5w-40 visc in Amsoil brand, I bought the oil and I won't change my mind on that. But I'm curious what people think about this viscosity and the spray pattern of oil jets. I would think the engine would have slightly higher oil pressure, which might exhibit a more forceful spray of oil out of the jets. Perhaps this may make up for the upgraded oil jet design that my car didn't get ?. Any opinions on this would be interesting. thanks for any replies.

 

[speedyswede]

Good question...this is something I've questioned as well.

My `93 240 has the B230 "L" squirter block...Volvo only used this engine in 240 series during the last year of production. I know the jet are triggered by pressure, but I don't know the exact specs. Volvo specs 10w30 for this engine, but I've been using 5w30 year round for several years now. Common sense tells me that the 5w would flow faster through the tiny jet passages, especially when cold, but I'm still uncertain.

 

[bepperb]

Lower viscosity will result in increased flow, which would be better for cooling assuming that the same percentage of oil from each was getting to the piston. But as you point out the higher pressure of a higher visc fluid through the same orifice will result in a longer spray. Impossible to say, in my opinion.

I really wouldn't worry about it outside of forced induction or some other serious track day use. I haven't seen many reports of failed F20/F22's, not that I'm some Honda guru but tales of unreliable Hondas tend to get passed around.

One thing also worth mention, is that an Esther based oil does have an increased heat capacity, trying to remember my highschool physics.... uh.... the same weight of an esther vs a petroleum based oil takes more enery to change it's temp. So, on air cooled engines there are reports of it making a difference. So, good choice with the AmsOil assuming it's not XL.

 

[JSRT4]

yes in one way thinner oil flow faster, but a slightly thicker oil may have a more forceful spray pattern, kinda like putting your finger on the end of a hose and changing the spray pattern. Not totally sure though.

 

[JSRT4]

Originally Posted By: bepperb
Lower viscosity will result in increased flow, which would be better for cooling assuming that the same percentage of oil from each was getting to the piston. But as you point out the higher pressure of a higher visc fluid through the same orifice will result in a longer spray. Impossible to say, in my opinion.

I really wouldn't worry about it outside of forced induction or some other serious track day use. I haven't seen many reports of failed F20/F22's, not that I'm some Honda guru but tales of unreliable Hondas tend to get passed around.


well yeah the reported engine failures were european cars running around 7000 rpms for long periods of high speed driving. I will never see that kind of use, and thus the need for upgraded oil jets is likely a non-issue. Just knowing that my car missed an upgraded part by just a few hundred engines is probably what irritates me the most. Thanks for the reply

 

[BuickGN]

I'm not up to date on the engine failures but I can't imagine a lubrication failure based on piston squirter design. These are usually used for cooling first, maybe a little secondary lube.

You can't really assume the 4 holes flow more or less oil than the two hole design. It really depends on the size of the holes.

At what point do things stay the same? More pressure with a thicker oil, less pressure with a thinner oil. You could end up with the same volume and pattern.

Is it possible the failures were due to cavitation issues?

Either way, you chose a good oil, I doubt you could do any better.

 

[jorton]

In some places oil is pretty cold and thick first thing in the morning. Sounds like a job for thin synthetic oil. How many minutes in to warm-up is the oil finally hot/thin enough for the squirters to function properly?

 

[SpitfireS]

Originally Posted By: BuickGN
Either way, you chose a good oil, I doubt you could do any better.

Well... Honda only recommends the 5W-40 for colder start-up temps.
In all other cases they recommend a 10w30.
It has been like that since 1999.
Today's 5w30 and 0w30 oils do both.
Both 30 weight, both flow well (better than most conventional 10w30 oils) when cold.

The oil jet bolts have their own spring loaded valve.
So it's not an "open hole", they need pressure to open.

 

[KW]

I think you made a good choice on the weight of oil to use.

It looks like the squirter is there to stopper when oil pressure is low to keep the rest of the engine lubed. So if the 5W40 gives you a little more oil pressure you should see more oil cooling on the pistons. That's only if oil pressure in an issue in your motor.

 

[Doug Hillary]

Hi,
Porsche "squirters" typically operated at 4bar (around 60psi) and above

 

[SpitfireS]

These open at 200 kPa (= 2 bar) = 29 psi.
Minimum oil pressure @ idle with 80C oil is 250 kPa according to spec so even at a hot idle they spray oil.

Highest oil pressure seen by owners with a gauge is 125 psi from 5000 rpm and up.
With a 40 weight, or better: a thicker than 30 weight oil, you'll reach this 125 psi a little sooner, meaning there is less oil flow into the engine at 5000 rpm. and above.
Is that what you really want?

Thinking that if the oil pressure is ok the oil flow must be ok as well is .. not right.

The F20C2/C1 and the F22's were designed around a 30 weight.
Yes: 5W-40 is named in the manual.
As an option for colder outside temps.

Oh well...

 

[mechtech2]

If Honda spent millions and could not figure out if the original oil jets were OK or not, how can any of us give an informed answer?

 

[SteveSRT8]

I own a Chrysler 6.1 and it also uses jets in the block aimed at the undersides of the piston crowns. This is a heat absorbing trick rarely used in naturally aspirated motors. Nice durability thing if you wail on it. But it does nothing for wrist pin lube as those are almost always pressure fed through the rod.

It does take a lot of volume/pressure to operate them properly. The 0W-40 is also my original spec, with a 15W-50 allowed for very hot climates.

I think you chose an excellent oil, the European formula meets a LOT of different foreign specs.

 

[GMorg]

In an oil distribution system, at a fixed pump RPM, the oil pressure is a function of the resistance to flow. More flow produces lower pressure. Since the distance and force of a "squirt" is determined by inertia when it leave the jet, the faster the flow, the further or more forceful the "squirt". So, you will always have a more forceful jet at a given RPM with a lower viscosity fluid.

 

[Gary Allan]

Quote:
More flow produces lower pressure.

 

[pcfxer]

It should read the other way. Lower pressure -> more flow.

 

[Gary Allan]

Originally Posted By: pcfxer
It should read the other way. Lower pressure -> more flow.

Are we qualifying that without saying "below the pump relief limit"? Even then I'm missing something.

 

[GMorg]

If the pump output volume is fixed (constant RPM), then the reason for high pressure it the resistance to flow. If the flow is high, at constant RPM, then the pressure will be low. Even if the relief valve is open due to high pressure, if the RPM is fixed, the flow beyond the pump (or beyond the relief valve) will be higher for a low viscosity fluid.

On the extremes of the flow circuit (very far from the pump) the situation can be different. A low viscosity fluid may have found short circuits and therefor not not reached the all points of lubrication. A higher viscosity fluid will not flow out of the short circuit routes as easily and will reach more distant lubrication points. However, it will not have greater flow rates. It will have gone further. At any point of escape, like a jet, the lower viscosity fluid will travel further due to its flow rate at the point of escape.

 

[Gary Allan]

Below the relief limit ..high or low ..the flow will be what the flow will be ..the pressure will be what the pressure will be. No two ways about it.

These jets are 29lb relief valves to the main gallery. They'll flow more the higher the pressure is above 29lbs. It will have to be somewhat variable depending on how much above 29lb you are. I can't see "full flow" @ 29.000001 as though it's an open tube at that point. It will have that index dictating total flow.

or so I reason.

 

[jmac]

Originally Posted By: Gary Allan
Below the relief limit ..high or low ..the flow will be what the flow will be ..the pressure will be what the pressure will be. No two ways about it.


That's ..... so ....... deepppp.