All You CHT Gauge Drivers Report Here

[airkooledchris]

The engine does what it does; "technique" didn't seem to have much effect.

and the engine doing what it does has more to do with how it was built (A) and maintained (B) over the course of it's life.

technique may help one from destroying their motor, but all the maintenance and technique in the world won't save someone from a shitty build, which is more likely the primary killer for premature engine expiration. (suffer from PEE? call today, Dr's are standing by.)

[iwantmybustorun]

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.
Colin

I have seen this too. On my trip this summer and back east. Always tried to avoid this though, because of what I have read.

( I ran 217* CHT down the pass from Jackson WY to Victor ID.)

I just did this today.
375 in 2nd up the pass and down to a record low 235 on the way down. I thought my engine had fallen out the back of the car and left the VDO sender flapping in the wind!!! I've never seen it so low.

[ruckman101]

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

When does technique become abuse?

Sitting around the campfire tonight with the Easter clan, I heard again tales of Cheryle's Dad's bus experiences, and I think his driving technique crossed that line.

1972 passenger bus, bought new, used to show potential buyers small vacation lots in a development next to Lake Merwin. Water skiing, park your camper, amenities, tennis courts, covered swimming pool, etc. He also made many a run to Seattle and back. So it crawled through barely developed steep hillside forest stuff (I've driven through the development, and even paved, those little roads are challenging), and made freeway runs to Seattle.

Under 10,000 original miles and it dropped a valve. "It wouldn't go over 70, and hills took it down to 50, 55, but you could hit 75 downhill, not much more." The freeway speed limit was 75 at the time. His first VW.

He said on his freeway runs to Seattle, he would put the accelerator pedal to the floor, and tuck the toe of his shoe under a flap of the air system to hold it there. I find it hard to believe he could only get 70 out of it, but....

I haven't had an opportunity to grill him on his break-in procedure or maintenance schedule, but I suspect it could be on the scanty side of paying attention to that that needed paying attention to with a spanking new engine etc.

He just drove it. And I think it was technique, not an inherent design flaw by VW that put the sour taste in his mouth for VWs. The '72 was replaced with a '73 model, and his experience was similar.


Uhh, sorry for the stray, back on topic. No gauges in Bertha. Just the warning light for oil pressure. If it flickers in a hard corner, getting low.

We've been using a tactile data collection system to gauge engine operating temperatures. It's tough to monitor trends, as the data collection window is very narrow. You can increase the frequency of data collection, but this also necessitates more frequent stops so you can open the engine hatch, and grab hold of the dip-stick. Too hot can't touch? Oh oh. Can get a grip on it, at least for a second or two, hopefully a bit more before it gets too hot to hold? In the range. Can power up five miles of a steep, twisty incline of a road in third, a few times even needing second and hop out at destination and really not even having to release my grip from the heat? Happy.


neal

[Bleyseng]

My 72 would go 75 no problem! I suspect that it died the same as many type 4 buses which was no paying attention to service intervals. My dad was the same way, he just drove cars and ignored servicing..

[Amskeptic]

My 72 would go 75 no problem! I suspect that it died the same as many type 4 buses which was no paying attention to service intervals. My dad was the same way, he just drove cars and ignored servicing..

1972 buses were very capable off the showroom floor. Top/cruising speed was 79 mph. A bus that is struggling to hit 65 is a Bus With A Problem.
Remember that these "new-fangled" Type 4 powered buses were a complex mystery to most mechanics at the time. We who have to follow the engineering of others must figure it out for ourselves much of the time. Even dealership mechanics had only their technical manuals to go by, and they were hamstrung by having to meet the current emissions regulations where even the engineers knew that the engines would suffer from the slightest error. Knowing the Bentley Manual as I do, I can tell you that the explanations and procedures do NOT wake up your intuition to the Whys Of It All. I used to follow the procedures religiously because I had NO point of reference, I could only blindly dumbly hope that if I followed the procedure religiously enough, the damn car would run.

A stupid split brake booster elbow or malfunctioning retard unit that wasn't caught when the engine was timed to 5*ATDC could easily mow down a brand new 1972 bus where the mechanic just compensated for a poor idle by richening that carburetor, the idle would improve but the highway running would melt an exhaust valve. The poor '73-'74 buses had far more complexity and were closer to the fine line of complete destruction and only bizarre behavior. Those gulp valves and air pumps were a ridiculous nightmare, a nightmare that I got to enjoy in all of its glory on the Road Warrior for a month until the air pump pulley grenaded in Brooklyn NY March of 1979. That was it for my experience of a fully functional emission system on a 1973 dual carbureted bus.
Colin

( I am currently leaning out my mixture in very small increments to find not the "lowest possible CHT numbers", but the best balance of temperature vs fuel economy. Like how some people who get so enamored of low oil temperatures that they forget that you want heat in the oil to evaporate moisture, I am not enamored of low CHTs for the sake of bragging rights, I want to self-clean the carbon out of the combustion chambers. Occasional CHTs in the 420-430 range on a hillpull do not freak me out. I sense that the absolute numbers are not as destructive as radical changes in temperatures across the same chunk of aluminum... that is where crack stresses may occur, like 85* fuel-chilled air rushing into an intake port not an inch away from an 800* blast of exhaust leaving through the exhaust port)

[Gypsie]

I am looking forward to posting in this thread now that I have a good starting point and 2 CHT's (#3 and #1) with VDO gauges.

[Bleyseng]

430-440 CHT's don't freak my out but they do "IF" I was still driving a bus with shoddy rebuild oem heads.....Colin, you have stock sweet oem heads not so crappy shit rebuilt 150k mile heads that tons of folks are driving on.
I don't sweat it at all with my AMC Len heads, I just drive and go fast, no 60 mph crap for me.

[Amskeptic]

430-440 CHT's don't freak me out but they do "IF" I was still driving a bus with shoddy rebuild oem heads.....Colin, you have stock sweet oem heads not so crappy shit rebuilt 150k mile heads that tons of folks are driving on.
I don't sweat it at all with my AMC Len heads, I just drive and go fast, no 60 mph crap for me.

Columbia River Gorge today! Headwinds! What a surprise! 92* at the I-282 to I-82 with many experiences of full throttle uphills. Once the engine reached full operating temperature, I witnessed a repeat of the surprise, CHTs go down as you stay in 4th and the vehicle speed drops from let's say 60-50 under full load. For me, that was 428* at 65 that dropped to 422* at 50. Once I had to downshift, the temps remained at the last observed 4th gear temp before the downshift so long as I remained at the downshift speed. If I accelerated to 50-55 in 3rd, the temps started going up again.

The good news is that once I knew the top of the temp curve, there was no exceeding it no matter how stupidly I drove.
Colin
(p.s. we cannot accept anything less than competent seat installations. I think I do prefer untouched seats in original heads more than advertised "we replace and stake seat inserts!" Next preference would be your Len Hoffman worked heads)

[poptop tom]

I have to wonder if my heads aren't running a tad too cool. 360 is the highest I've seen. DD CHT under #3 spark plug. I see the same thing Colin is describing above. A considerable drop in CHT's when letting out of the throttle some. Temp drops into the 275 range. That seems really low.

[vwbuff]

Well over here on the east coast and a wee bit north in Nova Scotia, I did a road
trip earlier this week.

1977 Rivera camper
2.0 L Boston Bob engine ( 21,000 miles )
Valves @ 1.5 turns pass zero lash
DD CHT
VDO oil & pressure
oil 15w40 Shell Rotella diesel

One thing I noticed that there has been no discussion on weight of the bus or
wind load on them.My bus has weighted in at 3950 lbs and the top is higher then a westy.
I would think this would affect our readings.
On my road trip this week the temp was 90 degrees,side wind gusty.At speed of 55-60mph
my CHT was 385 - 415, on the flat with small grades. On a steeper climb a couple of
times it peaked to 425, and like others downshifting and dropping my speed did not cause
a great drop in temp but did keep it from increasing.
My oil temps were higher then normal,peaked at 240 at one point for a bit,reducing speed did not seem to help.On the adverage it stays on 220 or slightly below.When stopping for gas or road work, heat soak was a big problem, even idling for 5-10 mins
did not decrease the oil temp.Of course the CHT dropped.
Just my observations with interest in thoughts on overall weight and height.

Wayne in Nova Scotia

[Amskeptic]

there has been no discussion on weight of the bus or wind load on them.
I would think this would affect our readings.
90 degrees,side wind gusty.At speed of 55-60mph
my CHT was 385 - 415, on the flat with small grades. On a steeper climb a couple of times it peaked to 425, and like others downshifting and dropping my speed did not cause a great drop in temp but did keep it from increasing.

Seems pretty normal for a stock bus. Weight and wind load fall under the heading of "work" and a VW engine knows it will be working out on the highway. The key for us is to set up the engine to be able to work at full load within acceptable temperature range. I am learning to go find the "ceiling" temperatures of whatever current environment I find myself. Once I have found the ceiling, I have noticed that the engine will absolutely not exceed it no matter what I do. My ceiling temperature is currently 430*

My oil temps were higher then normal,peaked at 240 at one point for a bit,reducing speed did not seem to help.On the adverage it stays on 220 or slightly below.When stopping for gas or road work, heat soak was a big problem, even idling for 5-10 mins
did not decrease the oil temp.

Oil temps, I noticed when borrowing RandyInMaine's VDO oil temp gauge, will not diminish when parked. They do go down when you get moving again. Those crankcase fins do their job.
Colin

[vwbuff]

Sounds like I'm seeing the same results then.Removed spark plugs
yesterday and they appear to be normal except very slightly on the
lean side, so I've been reading Colins AFM adjustment and may attempt to
enrich my mixture a wee bit.

[vdubyah73]

oil temps are more RPM related than work related. the higher the RPM the higher the oil temp goes. if you drop the RPM the oil temp will go down, it just takes time.

[72Hardtop]

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

When does technique become abuse?

Sitting around the campfire tonight with the Easter clan, I heard again tales of Cheryle's Dad's bus experiences, and I think his driving technique crossed that line.

1972 passenger bus, bought new, used to show potential buyers small vacation lots in a development next to Lake Merwin. Water skiing, park your camper, amenities, tennis courts, covered swimming pool, etc. He also made many a run to Seattle and back. So it crawled through barely developed steep hillside forest stuff (I've driven through the development, and even paved, those little roads are challenging), and made freeway runs to Seattle.

Under 10,000 original miles and it dropped a valve. "It wouldn't go over 70, and hills took it down to 50, 55, but you could hit 75 downhill, not much more." The freeway speed limit was 75 at the time. His first VW.

He said on his freeway runs to Seattle, he would put the accelerator pedal to the floor, and tuck the toe of his shoe under a flap of the air system to hold it there. I find it hard to believe he could only get 70 out of it, but....

I haven't had an opportunity to grill him on his break-in procedure or maintenance schedule, but I suspect it could be on the scanty side of paying attention to that that needed paying attention to with a spanking new engine etc.

He just drove it. And I think it was technique, not an inherent design flaw by VW that put the sour taste in his mouth for VWs. The '72 was replaced with a '73 model, and his experience was similar.


Uhh, sorry for the stray, back on topic. No gauges in Bertha. Just the warning light for oil pressure. If it flickers in a hard corner, getting low.

We've been using a tactile data collection system to gauge engine operating temperatures. It's tough to monitor trends, as the data collection window is very narrow. You can increase the frequency of data collection, but this also necessitates more frequent stops so you can open the engine hatch, and grab hold of the dip-stick. Too hot can't touch? Oh oh. Can get a grip on it, at least for a second or two, hopefully a bit more before it gets too hot to hold? In the range. Can power up five miles of a steep, twisty incline of a road in third, a few times even needing second and hop out at destination and really not even having to release my grip from the heat? Happy.


neal

A few things come into play here:

1. Most if not all owners back in the early days were very poor at their 'Service intervals' mainly the valve adjustments which is critical in these vehicles. Not to blame the owners but most just thought they were like any other car on the road. They aren't...not even close.

2. Points check. As you run them they degrade. As they degrade so does your optimum spark. As the spark degrades so does your optimum tune. One great thing with a 'Points replacement' is that the spark remains consistent no degradation.

3. The heads themselves. Over the past several decades a lot has been learned with respect to metallurgy. The seat material & interference fit as well as the other parts within the head such as keepers, springs, guides etc..The trick is finding the competent head builder who knows the correct way of rebuilding them and not skimping.

4. Head work coupled with a better than stock cam/exhaust (72-74HE) will yield better results.

5. None of this will do anyone any good if he/she chooses to ignore their service intervals and competent air-cooled engine builders. Which they're not many left.

[Amskeptic]

Around Town CHT readings:

Here in Portland Oregon where summer has not shown up (57* raining!) over the past few days, I am finding that stoplight-to-stoplight driving yields readings in the low 310-350 range.

I can see that VW would have difficulty getting these engines to pass smog with such sensitivity to over-cooling on throttle overrun and over-heating on long pulls.

I want to hook up the EGR down in California and see if CHTs react.
ColinRainPleaseStop