Itinerant Air-Cooled

Too many fascinating observations...
If you have a D.D. CHT gauge or a VDO gauge, please share your observations. If you do not tell us which gauge you have at the beginning of your post, a pox on your poor valves.

DD Gauge on Pickle. 1979 FI Solids Raby Camper Special. Been driving in very temperate weather on the way to Maupin. Highest I saw over Mt. Hood was 371.. cooled off to 310's at idle. Actually got fairly decent mileage.. I'd say 17 or so. At cruise at 65 was running about 350 maybe a tad less.

DD gauge on Charlie Brown 1979 FI Hydraulic rebuild stock. Running in 70 degree weather at 65 runs about 360-380.

IFBwax wrote:DD Gauge on Pickle. 1979 FI Solids Raby Camper Special. Been driving in very temperate weather on the way to Maupin. Highest I saw over Mt. Hood was 371.. cooled off to 310's at idle. Actually got fairly decent mileage.. I'd say 17 or so. At cruise at 65 was running about 350 maybe a tad less.

DD gauge on Charlie Brown 1979 FI Hydraulic rebuild stock. Running in 70 degree weather at 65 runs about 360-380.

What did you see on long pulls? Temps go up? Stay the same? Go down? Downshifts? Temps go up? Stay the same?

Cold day readings? Hot day readings?
ColinSorryIMissedMaupin

See, that's what gauges do, to some. Enough to make ya mad. Others enjoy the useful data.

On long pulls.. temps gradually go up.. higher rpms doesn't stop them from going up but will slow them as they creep up.. however I noticed that high rpms will raise my Oil temps faster than moderate rpms on an incline.. although that's a whole other matter.

Interesting. It makes sense to not thrash out yer engine; I can't believe that max. RPMs can be totally healthy for everything on long grades. Especially in the summer. Seems like there is a compromise in there somewhere....

IFBwax wrote:On long pulls.. temps gradually go up.. higher rpms doesn't stop them from going up but will slow them as they creep up.. however I noticed that high rpms will raise my Oil temps faster than moderate rpms on an incline.. although that's a whole other matter.

I discovered today especially, that the CHTs drop under full throttle as the rpms drop under the load of a hill that beckons a downshift. I did about 7 miles at full throttle in 4th at 42-45 mph at 6,000-7,000 feet and watched disbelievingly as my CHTs went from 404 to 397 at 10.4 on the LM-1.

Somebody on theSamba had mentioned frequency of combustion events/unit of time as a load on cooling, and you know what? Spot on.

Once again, my earliest childhood intuitions are being verified, that a nice calm climb in 4th with an engine still pulling in the upper 2Ks and low 3Ks is actually the happier engine. I will test and retest these hypotheses I am developing, but it looks like the cooling system gets ahead of combustion heat at lower rpms!
Hambone, follow your intuition.
Colin

79 FI Hydraulic, and running on the rich side probably...
DD under the #3, and my head temps hover between 360 and 380 at light load and around 55+ MPH

on the way TO Maupin, during the loooong slow climbs I could lug it slowly and climb in 4th at 40+45 for a while and head temps and oil would be still in check, with head temps climbing slowly to 400 on the nose...

when downshifting and running up really long and very steep climbs - 3rd gear and 3600 RPM for a long time and the head temps dropped to 380 while the oil would eventually rocket to 260.... the head temps were quick to recover where the oil took longer to get back into a nice range.

on the interstate, slight incline and just maintaining 65-70 my heads would stick right around 400-415 max, and the oil would push again closer to 260 if I maintained that speed.

on the way TO Maupin I saw around 15MPG, and on the way back it was 17.5MPG.

Interesting observations.

I wonder if the large charges of relatively cool fuel contributes to this? At WOT, the fuel volume in the intake stream would be maximized, at part throttle there'd be less fuel, less evaporative cooling.

From my air-cooled vanagon a couple of years ago. Head temps are F from a Dakota Digital. Oil temps are C. from a Volvo VDO gauge, sender was in the taco plate.

Thus:

"I have a confession to make: sometimes, I think Colin might be lying to me. Oh, not about the little stuff, like the nature of man, or the importance of socialized health care, but the big stuff, like whether an air-cooled vanagon can cruise around at 70 mph without overheating and risking death by thrown rod or seized engine.

Now, there are are conflicting data here; on the one hand, Colin is a master at the air-cooled art, and can spot a crappy rebuild at 30 yards; he can see through your lies about constant care, and fix crappy running with a single screwdriver. Therefore, he should know.

On the other hand, there is my vanagon, which has never done anything to suggest that what Colin claims is possible is actually possible.

So: after Colin's visit a couple of weeks ago, the van seemed to be running as well as it ever has, I decided to give it a stress-test; unlike government stress-tests mine was real and actually measured performance. I woke up early and drove to Vegas and back on the same day, starting at 7am and returning around midnight (I blew a couple of hundred bucks in the afternoon while waiting for evening). Here are some observations from that trip:

AM ~ running reasonably in the 380's on the way to east Riverside. Heat up the pass, ran at 400-410 going up hill, cooled way down on the backside. Oil temp stayed happily in the 110 C. range. (to convert C. to F. just double for approx value.) Speed on this section was 60-65 until the hill.

Ran from 390-410 across the desert, oil temp again happily in the 110C. range. I attributed the higher range to higher ambient temps. Not too hot that day, mid-90's or so at the world's largest (non-working) thermometer. Speed on this section was 55-60. Mostly 55.

I waited at Baker and had tacos for lunch, allowing the engine to cool before the big pass. Whoa baby! I had to drive 30mph in 3rd or sometimes second to keep the head temps under 430 F.! Oil temp an unhappy 128-130 C. all the way up.

Cooled off during the run down into Vegas, ran at 400/120 C. in traffic in Vegas.

I started the return trip at 6:30pm, by which temperatures had just started to cool. My question was: "will cooler ambient temps at night affect running temperature"? Answer = no. The same or higher on the return trip. Driving 55-60 kept the head temp at 410-430 all the way back, regardless of speed (during this section I discovered that the head temps would drop 6 degrees per 5 mph drop in speed). Higher for uphill, lower for downhill (headtemps in the 265 range on the downhill into Baker!). Oil temp stayed at 110 C if it was relatively flat, jumped to 120-130 C. going uphill. The later it got, the more stable oil temp was at around 110."

Original thread for context is here:

http://itinerant-air-cooled.com/viewtop ... 3&start=15

Mike

VDO gauge hooked up to #3

300-310 at warm idle.
375 on the streets
390-410 on the freeway
Can get up to 450 on hills in 3rd at 3500RPM
Temps increase quickly if I try to go over 65 unless I'm on perfectly flat land.

Lanval wrote:From my air-cooled vanagon a couple of years ago. Head temps are F from a Dakota Digital. Oil temps are C. from a Volvo VDO gauge, sender was in the taco plate.

Thus:

"I have a confession to make: sometimes, I think Colin might be lying to me. Oh, not about the little stuff, like the nature of man, or the importance of socialized health care, but the big stuff, like whether an air-cooled vanagon can cruise around at 70 mph without overheating and risking death by thrown rod or seized engine.

Now, there are are conflicting data here; on the one hand, Colin is a master at the air-cooled art, and can spot a crappy rebuild at 30 yards; he can see through your lies about constant care, and fix crappy running with a single screwdriver. Therefore, he should know.

On the other hand, there is my vanagon, which has never done anything to suggest that what Colin claims is possible is actually possible.

So: after Colin's visit a couple of weeks ago, the van seemed to be running as well as it ever has, I decided to give it a stress-test; unlike government stress-tests mine was real and actually measured performance. I woke up early and drove to Vegas and back on the same day, starting at 7am and returning around midnight (I blew a couple of hundred bucks in the afternoon while waiting for evening). Here are some observations from that trip:

AM ~ running reasonably in the 380's on the way to east Riverside. Heat up the pass, ran at 400-410 going up hill, cooled way down on the backside. Oil temp stayed happily in the 110 C. range. (to convert C. to F. just double for approx value.) Speed on this section was 60-65 until the hill.

Ran from 390-410 across the desert, oil temp again happily in the 110C. range. I attributed the higher range to higher ambient temps. Not too hot that day, mid-90's or so at the world's largest (non-working) thermometer. Speed on this section was 55-60. Mostly 55.

I waited at Baker and had tacos for lunch, allowing the engine to cool before the big pass. Whoa baby! I had to drive 30mph in 3rd or sometimes second to keep the head temps under 430 F.! Oil temp an unhappy 128-130 C. all the way up.

Cooled off during the run down into Vegas, ran at 400/120 C. in traffic in Vegas.

I started the return trip at 6:30pm, by which temperatures had just started to cool. My question was: "will cooler ambient temps at night affect running temperature"? Answer = no. The same or higher on the return trip. Driving 55-60 kept the head temp at 410-430 all the way back, regardless of speed (during this section I discovered that the head temps would drop 6 degrees per 5 mph drop in speed). Higher for uphill, lower for downhill (headtemps in the 265 range on the downhill into Baker!). Oil temp stayed at 110 C if it was relatively flat, jumped to 120-130 C. going uphill. The later it got, the more stable oil temp was at around 110."

Original thread for context is here:

http://itinerant-air-cooled.com/viewtop ... 3&start=15

Mike

So Mike . . . did it ever drop a valve, recede a seat, throw a rod?
Colin
( I ran 217* CHT down the pass from Jackson WY to Victor ID. No wonder the engineers were having trouble with air-cooled engines)

To and from Maupin I was running 355F at 70mph...tops going up loooong steep hills was 387F following IBX at 3/4 throttle in 4th. Downshifting to 3rd dropped the temps to 365-370F still climbing the long hills. Oil temps stayed at 220F all the time...even though we were fighting the wind the whole way back. I got about 17mpg leaving Maupin to Portland and 13mpg coming down to Portland fighting a headwind at 75mph.
DD on #3

Bleyseng wrote:To and from Maupin I was running 355F at 70mph...tops going up loooong steep hills was 387F following IBX at 3/4 throttle in 4th. Downshifting to 3rd dropped the temps to 365-370F still climbing the long hills. Oil temps stayed at 220F all the time...even though we were fighting the wind the whole way back. I got about 17mpg leaving Maupin to Portland and 13mpg coming down to Portland fighting a headwind at 75mph.
DD on #3

I re-confirmed yesterday on I-15 that holding in 4th dropped my CHTs, when I down-shifted, they stayed at the lower reading. This is all very interesting to me.
I am discovering that I have been "over-thinking" the hell out of all of this, and the engine deals with load and ambient temperatures according to its own dictates. No driving technique makes a whit of difference. The conclusion I am rapidly arriving at is:
Just Drive

Amskeptic wrote: So Mike . . . did it ever drop a valve, recede a seat, throw a rod?
Colin

No, Colin, the engine ran along until it stopped for some other reason around the time I sent it to the recycler.

My experience seems to suggest something similar to your conclusion. The engine does what it does; "technique" didn't seem to have much effect.

Mike