All You CHT Gauge Drivers Report Here

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Trexco
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Re: All You CHT Gauge Drivers Report Here

Post by Trexco » Wed Mar 16, 2016 9:53 pm

hi Aircooledchris,
Are you thinking because the tires are larger that the engine is lugging in the lower rpm bracket and not achieving sufficient RPMs to properly cool the engine ? I know that 4th gear will lose speed even on the mildest of inclines when running at 55 or 60, but does seem to hold better when running 65. Could this be because we are getting into the power band of the engine more ? Really need to get a tach in the cabin to better diagnose this... what is the power band of the 2.0L ?
1982 Westfalia 2.0L AC running 16in tires with Dakota digital cht. Stock FI

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SlowLane
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Re: All You CHT Gauge Drivers Report Here

Post by SlowLane » Fri Mar 18, 2016 11:25 am

Trexco wrote:Yes I would like to replace the distributor with a vacuum advance tried to do it once before but the drive was different. The centrifugal one has the drive notch off center where the new distributor appears to be centered on the drive bar.
AFAIK, all VW aircooled engine distributors have the offset drive tang. The distributor is one of the very few pieces with a common design for both the type I and the type !V engines. Could you post a picture of the distributor with the centered drive tang?
I realize these are not a speed demon, but I would think that I should be able to get 60-65 on level ground and stay under 400 on cht. I read on here several people that have achieved this, and are running 70. Had a 78 or 79 yellow vw westfalia blow by me on the interstate Sunday when I was running 60. Admittedly I don't know what engine he was running but it was impressive.
I can't speak for other people's experiences. Personally I can't whip my van at 65+ mph for any length of time without the CHTs creeping up into what I consider to be the abuse zone. I just drive with the expectation that I won't be able to keep up to modern traffic and so don't try to.
Sorry not sure what CR stands for, I am assuming that it has to do with fuel mixture. No Tach mounted in cab so unsure about rpms on the road. I usually shift 3rd to 4th around 50mph as third is pretty much wound out by then if that gives any indication. Have a handheld meter that reads rpm when working on engine..
CR stands for compression ratio, the ratio of cylinder volume when the piston is at BDC to the volume when at TDC.
If you shift at the marks inscribed on your speedometer, then your engine should be happy.
It is possible to install the factory tachometer provided on the later Vanagons into your aircooled beastie. I did this so many years ago that I forgot the details. I seem to recall that there was some instructions for doing this on the Old Volks Home website.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett

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Amskeptic
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Re: All You CHT Gauge Drivers Report Here

Post by Amskeptic » Sat Mar 19, 2016 8:05 am

Trexco wrote:hi Aircooledchris,
Are you thinking because the tires are larger that the engine is lugging in the lower rpm bracket and not achieving sufficient RPMs to properly cool the engine ? I know that 4th gear will lose speed even on the mildest of inclines when running at 55 or 60, but does seem to hold better when running 65. Could this be because we are getting into the power band of the engine more ? Really need to get a tach in the cabin to better diagnose this... what is the power band of the 2.0L ?
It pulls well from about 2,500 rpm to 4,300 rpm. That means you shift at 55 mph from 3rd to 4th for best acceleration.
The horsepower peak in 4th gear is right at 75 mph, but aerodynamic drag is approaching the "homeostasis point". You really need factory ratios and factory tire sizes for the best balance of "power" and engine longevity.

When you drive a 2.0 that has proper power output, you can feel the engine pull right on past 55 mph in 3rd. If there is a timing/mixture/breathing issue, it will feel winded.
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

Jivermo
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Re: All You CHT Gauge Drivers Report Here

Post by Jivermo » Sat Mar 19, 2016 11:18 am

"Homeostasis"! Really?

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asiab3
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Re: All You CHT Gauge Drivers Report Here

Post by asiab3 » Sat Mar 19, 2016 3:46 pm

Jivermo wrote:"Homeostasis"! Really?
Yeah homeostasis! It's that point about half an hour into the freeway flog that the power, speed, oil temperatures/pressures, cylinder head temps, and driver attitude all level out with the classic jams from the radio. It has been known to last as long as fifteen gallons of gas get me, and the stock Type 4 bus setup definitely does it well to boot. 8)
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

Trexco
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Re: All You CHT Gauge Drivers Report Here

Post by Trexco » Sun Mar 20, 2016 9:14 pm

Hello all,
I put together a spread sheet to approx. rpm to speed. I installed a new transmission last year and the paper work gave all the ratios.
axle gear 4.57
1st 3.78
2nd 2.06
3rd 1.26
4th .89

I looked up the diameter on the tires that I am running (26.2) and calculated it out from there. With this size tires 55mph = approx. 4063 rpms in 3rd. Seems to be inline with what Colin was saying about the shift point. The tires make about a 13% diff in mileage, odometer registers less than gps and about a 3-4 mph diff on indicated speed (slower) than the actual on the GPS. shifting into 4th would bring rpm down to approx. 2870 at 55 and 3131 at 60.

Running at 60 with 85 ambient and approx. 400 lbs load I see 410-415 on cht on level ground. I read in a previous post by Colin CHTs that were under 400 with similar conditions (except unsure on his tire size and gear ratios). So working on trying to get under 400. DD CHT gauge currently set to flash at 410, might push it back to 420 with the Hoffman Heads.
When you drive a 2.0 that has proper power output, you can feel the engine pull right on past 55 mph in 3rd. If there is a timing/mixture/breathing issue, it will feel winded.
I can get 55 but that is pushing pretty hard in 3rd.

Rex
1982 Westfalia 2.0L AC running 16in tires with Dakota digital cht. Stock FI

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Amskeptic
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Re: All You CHT Gauge Drivers Report Here

Post by Amskeptic » Wed Mar 23, 2016 7:10 pm

Trexco wrote: axle gear 4.57
55mph = approx. 4063 rpms in 3rd.
4th 2870 at 55 and 3131 at 60.

Running at 60 with 85 ambient and approx. 400 lbs load I see 410-415 on cht on level ground.
working on trying to get under 400.

I can get 55 but that is pushing pretty hard in 3rd.

Rex
Those numbers suggest that your tires are only a small part of the problem, but part of the problem none-the-less.

Define "pushing hard" as it relates to 55 in 3rd. What is pushing hard?
Can you hit 18 in 1st gear? 34 in 2nd gear? 75 in 4th?
They are all equivalents to your "pushing hard" in 3rd.

For fun, go check your Dakota ring terminal on the spark plug. Has it given you the famous pulled oval that allows combustion blowby? Do you see any burn/scorch on the ring?
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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jimbear
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Re: All You CHT Gauge Drivers Report Here

Post by jimbear » Mon May 23, 2016 8:17 am

Questions--
I am going to buy a DD CHT gauge. Which one should I get and what length of wire should I get? 14'? \

Anyone have a used one they want to part with?
'74 Hardtop Westy
Pretty much stock engine setup

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Amskeptic
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Re: All You CHT Gauge Drivers Report Here

Post by Amskeptic » Mon May 23, 2016 6:40 pm

jimbear wrote:Questions--
I am going to buy a DD CHT gauge. Which one should I get and what length of wire should I get? 14'? \

Anyone have a used one they want to part with?
I like the classic blahblah 10 blue with the annoying shiny glass.
The other one, a blahblahblahblah 11 is less reflective and greenish.

I think there is a bus-specific 18' wire. Ask them. Get it. Get a spare thermocouple terminal now, might as well.
ColinInNewHampshah
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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Randy in Maine
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Re: All You CHT Gauge Drivers Report Here

Post by Randy in Maine » Tue May 24, 2016 7:03 am

Keep in mind that I am the keeper of the Phil's 3 gauge mounting template for mounting gauges under the radio.

PM me if you want to borrow it.
79 VW Bus

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jimbear
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Re: All You CHT Gauge Drivers Report Here

Post by jimbear » Wed May 25, 2016 6:26 am

Randy in Maine wrote:Keep in mind that I am the keeper of the Phil's 3 gauge mounting template for mounting gauges under the radio.

PM me if you want to borrow it.
Do you have a pic of what this set-up looks like Randy?
'74 Hardtop Westy
Pretty much stock engine setup

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Randy in Maine
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Re: All You CHT Gauge Drivers Report Here

Post by Randy in Maine » Wed May 25, 2016 6:59 am

Go here and scroll down to the post by whip618....

http://www.thesamba.com/vw/forum/viewto ... ight=gauge
79 VW Bus

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Happyfolk
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Re: All You CHT Gauge Drivers Report Here

Post by Happyfolk » Thu Jun 09, 2016 6:06 pm

OK, I just ditched the ring under the spark plug on my Dakota Digital CHT sender. I bent it when brand new per Colin's instructions and was careful to hold it stationary when tightening the plug. It would be fine at first but I always quickly developed signs of combustion gasses leaking. High readings up to 420 on hill climbs, poor power, etc. Every time I pulled the plug the sender ring would be elongated by the wire crimp with signs of leakage.
I finally cut the ring off and wedged the remaining crimp with the thermocouple wires down between a couple of cooling fins next to the spark plug, getting it tight down against the head. I was thinking about using JB Weld to adhere it to the head as others have done but read in a Samba thread where another guy wedged it between fins and that seemed like a good way to try out without doing anything necessarily permanent. Totally different story now. It hits 250* just as fast as before but now maxes out at about 312 and now gets the highest readings just after slowing down or stopping instead of always getting the highest readings while moving. Seems to make more sense since airflow at speed should help cool things down. I still wrestle with not having it installed per design, but was it designed to go under the spark plug just to make it easier to install, or is that location really better? I've heard horror stories of stripped plug threads in these aluminum heads and having the ring under the plug just seems too problematic. I have better power up the hills now, and can quit pulling the #3 plug repeatedly to see what's going on. No matter how accurate it is now it still will let me know if something unusual is happening if I get higher readings than normal. The ring on the sender always seemed too loose on the plug even when brand new, and too thin from inside to outside.
79 CA FI Westy
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"Sandy"

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Amskeptic
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Re: All You CHT Gauge Drivers Report Here

Post by Amskeptic » Tue Jun 14, 2016 5:42 am

Happyfolk wrote:OK, I just ditched the ring under the spark plug on my Dakota Digital CHT sender. I bent it when brand new per Colin's instructions and was careful to hold it stationary when tightening the plug. It would be fine at first but I always quickly developed signs of combustion gasses leaking. High readings up to 420 on hill climbs, poor power, etc. Every time I pulled the plug the sender ring would be elongated by the wire crimp with signs of leakage.
I finally cut the ring off and wedged the remaining crimp with the thermocouple wires down between a couple of cooling fins next to the spark plug, getting it tight down against the head. I was thinking about using JB Weld to adhere it to the head as others have done but read in a Samba thread where another guy wedged it between fins and that seemed like a good way to try out without doing anything necessarily permanent. Totally different story now. It hits 250* just as fast as before but now maxes out at about 312 and now gets the highest readings just after slowing down or stopping instead of always getting the highest readings while moving. Seems to make more sense since airflow at speed should help cool things down. I still wrestle with not having it installed per design, but was it designed to go under the spark plug just to make it easier to install, or is that location really better? I've heard horror stories of stripped plug threads in these aluminum heads and having the ring under the plug just seems too problematic. I have better power up the hills now, and can quit pulling the #3 plug repeatedly to see what's going on. No matter how accurate it is now it still will let me know if something unusual is happening if I get higher readings than normal. The ring on the sender always seemed too loose on the plug even when brand new, and too thin from inside to outside.
Get anothe ring terminal, pronto, and you and I will install it when I get there. Your numbers are not useable.

The tip-off to this unuseability is the spike after slowing down. That is way down stream "heat soak" on the aluminum of the head as air flow drops.
You want your gauge to read instantaneous combustion temps and it will drop immediately as you release the accelerator pedal.
ColinYouCanDOThis
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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THall
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Re: All You CHT Gauge Drivers Report Here

Post by THall » Tue Jun 14, 2016 5:43 pm

Mike, I have a spare terminal if you need one.
'78 Westy 2.0 FI

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