CHT EXPERIMENT
Posted: 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.
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.