CHT EXPERIMENT

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CarlosZ
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CHT EXPERIMENT

Post by CarlosZ » Fri Mar 23, 2018 5:42 pm

It was suggested that I experiment with CHT so I decided to play a little MYTH-BUSTERS. Finally installed the Dakota Digital gauge a few months ago. Made a 12.4 mile+/- round-trip drive to test the difference in CHT with and without the bottoms of the shroud blocked. This was at a steady 60mph in 4th gear.

FYI - I don't have a camper special or HAM heads.

Running the following setup:

2.0 Type 4
Engine rebuilt about 4,000 miles ago by Conemac in Canoga Park, CA.
Mahle P&Cs
Rebuilt VW heads
Web 73 w/solid lifters
Dual 40IDFs
Petronix/SVDA
J-Tubes
Running all tins except for the sled tins.
Dakota Digital on #3

Started on the top of a hill/mountain, Rocky Peak to Collins and back. Rocky Peak to Yosemite is a steep downhill and pretty level until Collins. Not sure the elevation or grade, but close to sea level. Outside temp was around 64°. Beginning CHT was at about 300°F at the beginning of every round. Keep in mind the return begins at Collins at 300° so there were four runs.

THE LAYOUT OF WHAT I'VE WRITTEN HAS COMPRESSED ONCE POSTING THE TOPIC.
FIRST CHT #S ARE GOING WESTBOUND. THE CHT #S THE THE RIGHT OF THOSE ARE FOR THE RETURN TRIP. SORRY FOR NOT PRESENTING ON EXCEL.

BEGIN * MILE MARKER * CHT TEMP * SHROUD HOLES CLOSED

Rocky Peak Rd * 0 * 300° * 395° * end return trip
Keuhner Rd 2.0 324° 356°
Yosemite Rd 2.9 348° 356°
Stearns Rd 3.6 356° 356°
Tapo Canyon Rd 5.1 365° 356°
Sycamore Rd 6.5 365° 355°
Erringer Rd 7.6 365° 342°
First St 8.6 365° 342°
Madera Rd 9.4 365° 346°
Collins 12.4 365° 300° begin return trip

There was a metallic ping just before Collins. It momentarily made the car lunge a bit and run much smoother. The bus was running real sluggish for some reason. I realized that I forgot to loosed the left rear brake stars. I was messing with the rear brakes to adjust the e-brake and gave up midway when the RR stars were frozen. Forgot to loosen the LR e-brake stars and it was dragging. The LR hubcap was real hot. The return from Collins ran about 10° cooler overall w/o the locked brake.

Now for the round trip with the shroud ends open. No locked e-brake

BEGIN * MILE MARKER * CHT TEMP * SHROUD OPEN

Rocky Peak Rd 0 300° 415° end return trip
Keuhner Rd 2.0 300° 369°
Yosemite Rd 2.9 346° 369°
Stearns Rd 3.6 360° 369°
Tapo Canyon Rd 5.1 370° 370°
Sycamore Rd 6.5 377° 380°
Erringer Rd 7.6 374° 377°
First St 8.6 370° 369°
Madera Rd 9.4 377° 373°
Collins 12.4 375° 300° begin return trip

The return trips from Collins to Rocky Peak are the better indicators as both were with no sticking LR brake. Only the first run from Rocky Peak to Collins has the locked brake. All others were brake free.

CHT seemed to level off after around 10 miles of driving on level ground.

Average with the shroud holes closed was around 356°
Average with the shroud holes open was around 370°

There was no noticeable vibration or turbulence with or without the shroud holes covered.
Driving up the hill from Keuhner to Rocky peak saw a 20° difference between open and closed. I felt more comfortable reaching the top of the hill at 395° than at 415°. OPEN SHROUD HOLES BEING BETTER FOR COOLING MYTH HAS BEEN BUSTED. CLOSED SHROUD HOLES RESULTED IN LOWER HEAD TEMPS, AT LEAST ON MY BUS. RESULTS MAY VARY.

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JLT
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Location: Sacramento CA
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Re: CHT EXPERIMENT

Post by JLT » Sat Mar 24, 2018 11:18 am

Thanks for writing up the experiment. I've always been meaning to do a similar experiment, not with a CHT gauge but one of those laser thermometers aimed at various parts of the heads and engine. Maybe this summer.
-- JLT
Sacramento CA

Present bus: '71 Dormobile Westie "George"
(sometimes towing a '65 Allstate single-wheel trailer)
Former buses: '61 17-window Deluxe "Pink Bus"
'70 Frankenwestie "Blunder Bus"
'71 Frankenwestie "Thunder Bus"

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Amskeptic
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Re: CHT EXPERIMENT

Post by Amskeptic » Sat Mar 24, 2018 8:38 pm

CarlosZ wrote:
Fri Mar 23, 2018 5:42 pm
Made a 12.4 mile+/- round-trip drive to test the difference in CHT with and without the bottoms of the shroud blocked.
Average with the shroud holes closed was around 356°
Average with the shroud holes open was around 370°

There was no noticeable vibration or turbulence with or without the shroud holes covered.
I'm sorry, I can't quite figure out what the experiment was. What shroud holes?
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 94,615 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,990 miles

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Bleyseng
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Re: CHT EXPERIMENT

Post by Bleyseng » Sun Mar 25, 2018 5:52 am

I think he was talking about the fan to heat exchanger duct holes. But he is running heat exchangers? Stock muffler? etc....more data.
Geoff
77 Sage Green Westy- CS 2.0L-160,000 miles
70 Ghia vert, black, stock 1600SP,- 139,000 miles,
76 914 2.1L-Nepal Orange- 160,000+ miles
http://bleysengaway.blogspot.com/

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Westy78
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Re: CHT EXPERIMENT

Post by Westy78 » Sun Mar 25, 2018 8:02 am

I took it as being the lower cooling tins that cover the pushrod tubes.
Chorizo, it's what's for breakfast.

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Amskeptic
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Re: CHT EXPERIMENT

Post by Amskeptic » Mon Mar 26, 2018 6:05 pm

Westy78 wrote:
Sun Mar 25, 2018 8:02 am
I took it as being the lower cooling tins that cover the pushrod tubes.

That is what I was originally thinking, but "holes" slowed me down.
Experiment with lower tins . . .
vs
Experiment without lower tins . . .

That, I get.
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 94,615 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,990 miles

CarlosZ
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Re: CHT EXPERIMENT

Post by CarlosZ » Sat Apr 14, 2018 8:01 am

You guys are killing me. Bleyseng got it right.

I’m talking about the two shroud to heat exchanger ports at the bottom of the shroud. The ones where the non-return flaps would connect to. The experiment had nothing to do with tins, though I didn’t have the sleds or thermostat installed. I’ll try a few runs with the sled tins to see if there is any difference. Do you think the sled tin is more effective at cooling the bottom half of the cylinders than the air flow generated while driving w/o the sled tins? Keep in mind I’ve no heat exchangers to enclose the bottom of the cylinders.

Running empi single exhaust that’s falling apart. No heat exchangers, just J-tubes.

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Amskeptic
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Re: CHT EXPERIMENT

Post by Amskeptic » Sun Apr 15, 2018 9:18 am

CarlosZ wrote:
Sat Apr 14, 2018 8:01 am
You guys are killing me. Bleyseng got it right.

I’m talking about the two shroud to heat exchanger ports at the bottom of the shroud. The ones where the non-return flaps would connect to. The experiment had nothing to do with tins, though I didn’t have the sleds or thermostat installed. I’ll try a few runs with the sled tins to see if there is any difference. Do you think the sled tin is more effective at cooling the bottom half of the cylinders than the air flow generated while driving w/o the sled tins? Keep in mind I’ve no heat exchangers to enclose the bottom of the cylinders.

Running empi single exhaust that’s falling apart. No heat exchangers, just J-tubes.
Well Bleyseng is brilliant . . .

You, Carlos, you really are over-thinking this. Driving without the sled tins does not provide the engine with any "cooling" from undercar airflow. It does provide opportunities for debris strikes that could screw up your push rod tubes. The sled tins also help the thermostat open at the correct time when you decide to install the thermostat to help your engine last longer.

I have been experimenting with these VW engines for decades now, flogging them on interstates in mid-summer southwest desert heat and climbing hills without end. My conclusion is basically that we have no idea of the physics involved, we have very little agency in determining engine temperatures, there is not a trick in the world that makes one driver keep his engine cooler than another driver. It all comes down to:

a) actual architecture of engine, i.e. compression ratio, cam profile, exhaust system
b) state of tune, timing and fuel mixture and absence of pesky little vacuum leaks
c) just drive

The unbelievable array of stories and theories and techniques you read about on the internet are so often damn close to nonsense, the variables utterly out-of-control, and there is very little real-world experience of driving these engines 2-10-12 hours at a time to actually arrive at a true "operating temperature".

Volkswagen knew all of this human nature when they sold these cars new . . . without gauges. They designed the cars to self-moderate by limiting the power/heat output. We second-guess them and declare that we can make our engines more powerful, but we seem not to realize that Volkswagen could have too. But they knew better. The relaxed "under-powered" VW is a perfect balancing act for best reliability and economy.
Colin
(p.s. you damage the "laminar"airflow in the fan housing when you block the exchanger outlets, causing turbulence that can affect the rest of the engine's cooling. Less of a problem with Type 4 fan housings than Type 1, but there you go, something else to muse about)
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 94,615 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,990 miles

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