High oil temp and forensic engine investigation

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sgkent
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Re: High oil temp and forensic engine investigation

Post by sgkent » Mon Jul 10, 2017 1:27 pm

here is a comparison - I have a 1977 almost bone stock FI engine tuned to run as rich as it can and still pass smog tests cleanly. We went to Yosemite this weekend. Highway speeds 60 - 65 most of the time, RPM about 3400 at 60 mph, oil 220F and heads 350F. That was in ambient temps from 80 F to 105 F. climbing into Yosemite from essentially sea level to 6,000 feet the oil temps went to 260F tops after climbing to 4,000' however head temps were a constant 350 F to maybe 375 F. Normally head temps are about 400 F but I overfilled the oil a little and I suspect that helped with splash on the underside of the pistons, cooling them a little more resulting in cooler heads too. 20W - 50 oil. I also burned premium 91 octane this trip. It helped a little with MPG (19.6 instead of 18 mpg) and maybe combustion temps a tad by slowing the burn in the cylinders. That gives a slightly longer push on the pistons. I also noticed that the tailpipe was a little grayer than with 87 or 89 octane. Engine was very smooth. I know from calculating compression ratio it should be 7.3:1 which is stock but my cylinder pressures calculate more like 8.0:1 so either the compression gauge or my math is off. It is also possible that the piston rings and valves have finally fully bedded now that the engine has about 3500 miles on it, and I am seeing those results in the temps and exhaust color. It was just smogged a few months ago and that was very clean. The timing is closer to 32 BTDC full in than the usual 29 full in at this time (smog test looks for factory timing) so that actually should have raised the head temps but yielded better fuel economy - it is also why I used premium this trip.

Here is what I see in your notes - you should have 10 PSI oil pressure per 1000 RPM minimum. At 60 MPH you should be turning about 3400 RPM with stock tires if it is a late bay. That means you need a minimum of 34 PSI oil pressure to keep the engine happy at 60 mph. I see more like 50 - 55 PSI oil pressure at that temp and speed. When I stop at a stop light the engine is idling at 850 RPM +/-. When the oil is 260 F the oil pressure drops to 10 PSI and the VDO gauge turns the light on which is normal because the VDO dual sender turns the light on at 9 - 11 PSI. The stock sender can be as low as 3 PSI before the light comes on. If you are using 20W-50, there might be some concern about why your pressure is only 38 PSI at 60 MPH assuming the gauge is accurate. That seems 10 - 15 PSI low to me if you are running 20W-50 in the hot weather. My 1971 upright was about the same behavior as to RPM, oil. temp, and oil PSI.
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drober23
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Re: High oil temp and forensic engine investigation

Post by drober23 » Mon Jul 10, 2017 6:03 pm

Colin,
After warm up gauge read 214. Laser thermometer on sump read 218. Left rear corner of case read 227.

That said, it was in the 60s and rainy all day. On my drive to Lake Chautauqua I averaged CHT of about 385 and oil temp around 215. Much lowe than my normal 410 and 230 when it is 85 outside.

I'll keep driving it and see how it goes for now though.
DJ

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drober23
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Re: High oil temp and forensic engine investigation

Post by drober23 » Mon Jul 10, 2017 6:10 pm

SGKent,

I have put about 30k on this engine. After switching exhaust this year the CHT seem about the same, but oil temps are higher.

I have never gotten the kind of oil pressures you post with this engine though. It is a Raby built Camper special. I get about 36-38 psi at 60 mph when oil temps are in the 200-210 range. It drops from there as oil temps rise.
I was up to 225 a bit today and the gauge read 30 psi. The day I got worried, I had spikes up to 247 and the gauge dropped to 25 psi, which seemed really low.
DJ

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Re: High oil temp and forensic engine investigation

Post by Amskeptic » Thu Jul 13, 2017 9:03 am

drober23 wrote:
Mon Jul 10, 2017 6:10 pm
SGKent,

I have put about 30k on this engine. After switching exhaust this year the CHT seem about the same, but oil temps are higher.

I have never gotten the kind of oil pressures you post with this engine though. It is a Raby built Camper special. I get about 36-38 psi at 60 mph when oil temps are in the 200-210 range. It drops from there as oil temps rise.
I was up to 225 a bit today and the gauge read 30 psi. The day I got worried, I had spikes up to 247 and the gauge dropped to 25 psi, which seemed really low.


I have run into low oil pressures with Raby engines before. He is so good with main/rod bearing clearances, that I don't suspect them. End play is a tad generous, but I think the aftermarket oil pump indexing is a possible culprit. I also do not trust gauge numbers all that much. Too much crap out there, especially aftermarket VDO.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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sgkent
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Re: High oil temp and forensic engine investigation

Post by sgkent » Thu Jul 13, 2017 3:19 pm

he once said that he liked .008"+ on the end play. That will kill oil pressure some. I might start looking at end play next time the engine is out.
TBone208 wrote: "You ppl are such windbags. Go use your crystal ball to get rich & predict something meaningful. Nobody knows what's going to happen. How are we supposed to take ppl who don't know the definition of a recession & "woman" seriously?"

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Re: High oil temp and forensic engine investigation

Post by drober23 » Fri Jul 14, 2017 6:32 am

I just drove to Jamestown NY and back (about 300 miles each way).

For the most part, CHTs were excellent for me (380 - 390 for the most part with the occasional 410 on a long hill). Oil temps hung around 230, and at 230 the oil pressure at 60 mph started the trip home at about 30, but was down to 26 the last hour or so.

Next step is to replace the junk hose on my remote oil sender with something a bit more substantial. I have a 4-way T fitting with that has the DD sender, and the OG sender on it at the moment. I never grounded it, so my OG sender doesn't light the light... (I'll fix that too). I will add a mechanical gauge to the last open port on the T to let me compare the DD gauge's readings.

If it turns out the oil pressure readings are accurate, its time to plan what to do about it.

In unrelated, but nonetheless interesting to me news... Got the PLX Air/Fuel Ratio gauge re-installed. A nice gentleman at the Cummins plant I was teaching at this week welded the bung on the new tailpipe for me. Did an awesome job! I had been nervous about high CHT right after Colin left, so I bumped the AFM a bit richer.

Its running pretty rich right now. Idles at 13.8, cruises (60 mph, flat, no wind) at about 12.0, and goes down as low as 11.2 under part throttle acceleration. Odd thing though, when I am at full throttle, it goes back up to about 12.2. Hmmm... Averaged 15.8 mpg (down from close to 18 in the past) on the trip. But, my CHTs were as low as I ever remember them for a long trip. Not sure whether to change things or leave them be.
DJ

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In a time of chimpanzees I was a monkey

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sgkent
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Re: High oil temp and forensic engine investigation

Post by sgkent » Fri Jul 14, 2017 2:39 pm

just be aware that at that low an air to fuel ratio you are washing gasoline into the oil and tossing it out the tailpipe. Power is leaving with it. The extra fuel is cooling the engine but the richness is washing oil off the guides which will wear faster. I'd suggest a 60 - 65 MPH A/F ratio of 12.5:1 with it rising to 13.5 to 14.7 at 35 MPH. CO should be set at idle to the rich side of the factory spec.
TBone208 wrote: "You ppl are such windbags. Go use your crystal ball to get rich & predict something meaningful. Nobody knows what's going to happen. How are we supposed to take ppl who don't know the definition of a recession & "woman" seriously?"

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Re: High oil temp and forensic engine investigation

Post by Amskeptic » Tue Jul 18, 2017 9:47 am

drober23 wrote:
Fri Jul 14, 2017 6:32 am
I just drove to Jamestown NY and back (about 300 miles each way).
Averaged 15.8 mpg (down from close to 18 in the past) on the trip. But, my CHTs were as low as I ever remember them for a long trip. Not sure whether to change things or leave them be.

Did we monkey with the black cog? That is the only circumstance I can think of that would cause this "out of phase" progression of mixture, i.e. richer at partial throttle than full throttle. It is a pain to experimentally get yourself back in phase so that you have a proper progression. Out of phase also shows up when you are richer at off-throttle than on-throttle. I got the BobD to eventually shut off the fuel at high rpm throttle release and still give a "power circuit" richening at full throttle. Please note that if you maintain full throttle from about 55 mph to 70 mph, the mixture naturally leans out as you reach 70. This is as it should be. Be aware of mph and throttle position as you read your ratios. I get 11.2 at 55 that leans to 12 at 70.
Your numbers are not really "fuel washing the oil out of everything" so long as you have combustion. Check your plugs. If the insulators are white to light tan, relax.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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drober23
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Re: High oil temp and forensic engine investigation

Post by drober23 » Tue Jul 18, 2017 1:23 pm

After you left, I monkeyed with the inner (static) adjustment a fair bit. I did not touch the outer (dynamic) adjustment.

Since then, I realize that my brake booster repair has intermittent failures, actually ordered the rubber grommets to seal all those bits up properly. Once I have that all done, I will try to undo the static adjustment I made to return it to where you left it and see if it needs anything.
DJ

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Re: High oil temp and forensic engine investigation

Post by drober23 » Fri Jul 21, 2017 10:54 am

Ok....

Attached a physical oil pressure gauge. My digital gauge in the cabin appears to be correct.

If my oil temps are around 215-220, then I get about 36 psi at 60 mph (4th gear). This is what I was used to before this year. When the oil temp climbs into the 230s, the oil pressure drops, sometimes as low as 25 psi at 60 mph.

My guess is that nothing inside the engine has changed. Since I changed back to a stock exhaust, the engine oil temps are running higher, so I am noticing the low oil pressures at high engine oil temps more (because they happen a lot more). If I could drop 20° off oil temp, my pressures would be what I have been used to over the last 30,000 miles.

My choices seem to be:
a) Roll it and hope it doesn't die
b) Put the more open exhaust back on
c) Run an oil cooler
d) Tear it down and look for clues

Blerg!
DJ

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(plus more busses than sense)

In a time of chimpanzees I was a monkey

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Re: High oil temp and forensic engine investigation

Post by airkooledchris » Fri Jul 21, 2017 12:18 pm

Amskeptic wrote: Please note that if you maintain full throttle from about 55 mph to 70 mph, the mixture naturally leans out as you reach 70. This is as it should be. Be aware of mph and throttle position as you read your ratios. I get 11.2 at 55 that leans to 12 at 70.
That is unfortunate? Higher RPM's create more heat, where a richer tune would be more ideal at 3800 RPM than at 3000 RPM - even if you are at WOT in both cases.

For me once I hit my desired max speed, I am at part throttle only, but running 36/3800 RPM's. Ideally id love to control mixture based on RPM's moreso than at throttle position (once in 4th, as I don't think it would be useful to run rich while getting up to speed as much as once you get there.)
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Re: High oil temp and forensic engine investigation

Post by Amskeptic » Fri Jul 21, 2017 9:52 pm

drober23 wrote:
Fri Jul 21, 2017 10:54 am
Ok....

My choices seem to be:
a) Roll it and hope it doesn't die

20-50w yaah? Have you cleaned your cooler/crankcase fins?*
That dirt road of yours doesn't help.
Colin


* as in:

Image
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: High oil temp and forensic engine investigation

Post by drober23 » Tue Aug 29, 2017 5:35 pm

Time to add some closure to my end of this. I have about 5000 miles on the bus since Colin's visit.

I drove all the way from Carleton, MI to Tryon, Nebraska, then on to Estes Park, CO with the mixture enriched as I described above.

Cylinder Head temperatures were never a problem, stayed in the 380 - 390 range most of the time. Only occasionally ever broke 400 on the end of a long hill. Oil temps would climb to the low 230s and stay there until extra exertion was required. In the low 230s, the oil pressure would drop to about 26 psi and then stay there.

If I let it get over 240 the pressure would drop a bit more. This happened when I was driving 65 mph (actual, gauge said 68) through Nebraska on a day with the outside temp in the mid 80s. No particular wind. Dropping the actual speed to 60 put my temps back into the low 230s and I went happily on my way.

In the altitude, the bus was a mess and I had to lean things out some. I put the mark back where Colin had left it during his visit. The bus ran much better in the mountains. So I decided to keep it there and monitor it on the way home.

Has anyone else used the PLX air/fuel ratio sensor with their option for a bluetooth connection to their Multigauge app on your phone? I had gotten tired of futzing with the physical gauge because I only use this when I am tinkering with the fuel injection. Having the app on your phone is really nice! I can hang my phone from the ash tray with one of those "hold your phone thingamabobs" and connect up when I want. Then, when it is time to adjust something, I take the phone to the back of the bus with me. Makes it easy to see your changes as you reset things.

Anway, it was interesting to watch the average Air/Fuel ratio go down as my altitude dropped. The following are the average Air/Fuel ratio at 65 mph on level ground without wind or acceleration (hard to recreate all the time but I had LOTS of miles to get it right)

11.8 in Boulder
12.3 in Ogalalla, NE
12.5 in Davenport, IA
13.1 in Chicago and onward into Michigan

As I was driving through Colorado and Nebraska, I noticed that I was now limited more by high Cylinder Head Temps (makes me happier to keep them around 410 max, but not scared to go a bit above that on a long hill) than by Oil Temperature. All through Colorado and Nebraska I never got over 229 for oil temp, and averaged in the mid 220s. I figured that would change as the A/F ratio continued to climb, but it really didn't change much.

I had a dilemma at the Nebraskaland Truck Stop. I decided to stop there because the cute Sinclair Dinosaur makes me giggle. I have a Raby engine, and he always said to use premium gas in it. The Sinclair station did not have premium gas (!), only 87 octane. I, of course, heard Colin's voice in the back of my head saying that I should not need premium. So I filled up with the regular. It was fine... I have filled with regular the 1500 or so miles since.

The oil temps held steady in the upper 220s as I traveled the rest of the way home. I kept a consistent 65 - 70 mph and neither the cylinder head temps nor oil temps presented themselves as a problem very often. The highest readings I got were actually in the bit of highway I drive home from work on, where it sneaked up to 232 for a couple minutes. In retrospect, that little 20 mile stretch seems to be at a consistent incline. Not very steep, but pretty consistent.

So after all this, my cylinder head temps are acceptable, my oil temps are better, the oil pressure is better because the oil temps are better and my fuel injection settings are back where Colin left them. I cannot replicate the couple instances where my oil temps shot well into the 240s for no apparent reason (which is what scared me in the first place). So, I will leave things as they are FI wise.

The bus was a joy to drive, especially on the drive home. The leaner mixture was peppier in general than the mess I had created earlier. Fuel economy on the ride home was about 18 mpg, but I had a tail wind much of the time for that.

On the down side, I did notice a little oily moisture under the passenger side CV joint as it mates to the transmission. I'll keep it full of fluid and deal with the seals in the fall.
DJ

'75 Westfalia, '79 Deluxe
(plus more busses than sense)

In a time of chimpanzees I was a monkey

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Re: High oil temp and forensic engine investigation

Post by Heliconman » Fri Sep 01, 2017 6:11 pm

Thanks for sharing DJ,

Ill have to pick your brain this fall/winter on your engine monitoring setup. I'm finally finishing my CHT after only 2 years! Well the move and all the new house projects might have had a thing or two to do with it. Glad you made it back safe and sound.

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Amskeptic
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Re: High oil temp and forensic engine investigation

Post by Amskeptic » Mon Sep 04, 2017 9:24 am

drober23 wrote:
Tue Aug 29, 2017 5:35 pm
Time to add some closure.

Head temperatures stayed in the 380 - 390 range.
Oil temps 230s
pressure about 26 psi.

The bus was a joy to drive.
There you go then. Do you know what size your pump gears are (for real no guessing)?
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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