All You CHT Gauge Drivers Report Here

[dittrich]

makes me wish I had a lambda loop ECU...you can see how rich it goes as you let your foot off the throttle, wasting gas. I'd think the feedback loop would nip that in the bud a lot quicker.

How about a functional decel valve?
Colin

It's an automatic, so no decel valve 4 me I think that only helps burn up the extra gas for emissions though?

To save the gas it'd have to be something that detects rich & instantly cuts the injector open time or something. hey, wait a sec...that's what the vw engineers ended up doing in later models... so it goes. i'll now resist the urge to tinker & frankenstein my vanagon in an attempt to improve mileage.

Back on topic,(sorry) I have a type k thermocouple wire with a crimped on ring terminal under plug #3 connected to a $11 handheld thermometer taped to the dash. (That's right, I spare no expense). CHT's are in the 380-400 around town and rise up to about 420-430 on highway around 65...all on mildly hilly terrain. Engine has 25k & is a VW Canada rebuild from around 1998.

[SlowLane]

I have a type k thermocouple wire with a crimped on ring terminal under plug #3

Are you using k-type thermocouple wire for the entire run from ring terminal to gauge? If not, then you're introducing measurement errors at each junction of dissimilar metals.

connected to a $11 handheld thermometer taped to the dash.

A high-quality unit to be sure. At that price, I would question how good a job it does at temperature compensation.

Your temperatures, if they are accurate, are quite a bit on the high side.

[airkooledchris]

Colin and I spent the second half of our day together playing with the AFM settings on my 79 CA setup and were constantly confounded by how it reacted to changes.

Getting off the throttle completely/overrun and my mixture would hold steady at the same AF ratio as partial throttle was showing.

Maybe this was VW's way of keeping the cat on this setup happy?

If I had 11.7 partial throttle (yes we went that rich chasing down CHT's) and you completely let off the gas after starting a big long hill descent - it will stay at 11.7 as it cruised down the hill.

The O2 sensor is not connected, but that doesn't mean you still get full control over mixture by simply using the AFM. The computer is still putting a lot of it's own thoughts into this mixture process. After going somewhere in the neighborhood of 18 clicks towards rich with the black cog I think we ended up going 6 clicks lean from our starting point and then adjusting the silver wiper towards rich instead.

This is all in an effort to tame CHT's of course. I have a VERY strong engine that will pull all day long, but a light headwind, a small hill and loaded up for camping - the CHT's just climb crazy fast.

We got the temps into a reasonable range (the upper end of reasonable) by going crazy rich eventually. Im doing my own seat of the pants testing now without the LM-1 and using a spare AFM to see just how low I can get the temps and still be able to drive it. My goal is to get it so freakin rich that the temps stay cool during longer highway driving (and when loaded up with gear) - then weld an O2 bung in the exhaust and setup a switch at the dash to enable/disable the signal. For in town driving ill let the computer try and get 14:1 and then disconnect that signal and let my piggy AFM take over.

That - or im going to carbs. I like computers but not when you don't have a say in what they do and what they do isn't published anywhere.

[dittrich]

Are you using k-type thermocouple wire for the entire run from ring terminal to gauge? If not, then you're introducing measurement errors at each junction of dissimilar metals.

Yeah, it's type k the whole run.

A high-quality unit to be sure. At that price, I would question how good a job it does at temperature compensation.

As for the cheapo thermometer, I've done ice bath/boiling water/oven testing on it & it seems accurate enough. I've also measured my body temp in the 70F house & outside at 32F and it reads around 37C both places, so it's got CJC. It uses a (blobbed-over) IC to do the amplification and cold junction comp so it's either an AD595-type w/analog out or uses a digital chip like the MAX6675 or MAX31855. When you buy an expensive digital gauge like the DD, the cost is for the fancy display & container, not the circuitry. I'm actually just finishing up my replacement which i built with a MAX6675 ($7) and a MSP430 microcontroller ($5). Instead of a numeric display (which I stare at too much) it's just going to use a 10 segment LED bargraph ($1.50) & just display from 350F-450F.

Your temperatures, if they are accurate, are quite a bit on the high side.

Is that high for an AT aircooled vanagon westy? I thought that was about normal? C'mon man, don't make me paranoid...

I'll have my new gauge done soon so I'll be able to compare them...hopefully it's reading high, I guess

[dittrich]

Colin and I spent the second half of our day together playing with the AFM settings on my 79 CA setup and were constantly confounded by how it reacted to changes.

Getting off the throttle completely/overrun and my mixture would hold steady at the same AF ratio as partial throttle was showing.

Maybe this was VW's way of keeping the cat on this setup happy?

If I had 11.7 partial throttle (yes we went that rich chasing down CHT's) and you completely let off the gas after starting a big long hill descent - it will stay at 11.7 as it cruised down the hill.

The O2 sensor is not connected, but that doesn't mean you still get full control over mixture by simply using the AFM. The computer is still putting a lot of it's own thoughts into this mixture process. After going somewhere in the neighborhood of 18 clicks towards rich with the black cog I think we ended up going 6 clicks lean from our starting point and then adjusting the silver wiper towards rich instead.

This is all in an effort to tame CHT's of course. I have a VERY strong engine that will pull all day long, but a light headwind, a small hill and loaded up for camping - the CHT's just climb crazy fast.

We got the temps into a reasonable range (the upper end of reasonable) by going crazy rich eventually. Im doing my own seat of the pants testing now without the LM-1 and using a spare AFM to see just how low I can get the temps and still be able to drive it. My goal is to get it so freakin rich that the temps stay cool during longer highway driving (and when loaded up with gear) - then weld an O2 bung in the exhaust and setup a switch at the dash to enable/disable the signal. For in town driving ill let the computer try and get 14:1 and then disconnect that signal and let my piggy AFM take over.

That - or im going to carbs. I like computers but not when you don't have a say in what they do and what they do isn't published anywhere.

*sigh*

Well, thanks for the info. FWIW, I can't stand the mystery box either...but it explains the voodoo magic people swear by on these vehicles...crazyville.

y'know, I'm beginning to think people are right, that these gauges will drive you nuts...just keep the maint. up, do the dipstick heat test every once in a while & forget about it. i really need to quash my inner geek's desire to continually add sensors to this beast...

...after i finish my CHT

...of course, a datalogger for injector pulse frequency/duration vs. afm wiper position vs. throttle position vs. moon phase vs. stock market performance would be pretty cool & might yield some interesting results...

[airkooledchris]

it's the maintained CHT's at those numbers that are potentially dangerous. I think it is normal for an Aircooled Vanagon westy (I had one myself) - but it's not a good thing.

I don't completely doubt the accuracy of your gauge btw, but when comparing numbers with others it really helps to be using the same methods.

it's like the guys that JB weld the sender wire somewhere other than under the #3 spark plug - you can certainly use that to guide yourself, but you can't then compare the numbers to other people using the spark plug sender under the #3 and a Dakota Digital gauge.

[dittrich]

I don't completely doubt the accuracy of your gauge btw, but when comparing numbers with others it really helps to be using the same methods.

Right on. Since they blobbed over the chip on the PCB I can't really tell what they're using. I'm reading from #3 though & a working thermometer is a working thermometer. I'll double check once I finish my new gauge, but it would seem I'm now stuck with either blissfully ignoring the temps or going back over everything for the 1000th time in an effort to cool it down

poop.

[BumbleBus]

Dakota Digital on #3. At 65MPH on the highway my head temps will usually be around 400-410. Going up large inclines, especially in the summer in California, can put the head temperatures near 450 at times. This has always freaked me out, but it just seems to be the way it goes.

Also, I have a VDO oil temperature gauge with sender in the oil plug. At sustained highway speeds, the oil will usually stay around 220-230. Again, going up large inclines in the summer, I've had the oil temp up to 260, which seems pretty high to me.

Last weekend was my first camping trip with my new DD installed under #3 plug. I also have a VDO with "taco plate" install. '72 campmobile. CB000076 Type IV... barely 100s compression. Tired motor. Smells like mouse piss when it gets hot. Trying to save up for a rebuild. Heh, heh. Milking it through summer camping season. Anyway...

Ambient 90f. Climbed from 3,000ft to about 5,700ft to get to our campground. Strong head winds. CHTs were hitting the 450f flashing warning a LOT on the highway part at 55mph 3,200rpm max torque so naturally I was freaking out, but oil temps were 210ish so I kept on trucking and the bus seemed happy. Slowing down to 40-45 would lower temps to 400ish.

Then the climb started. 3,200rpm. 2nd gear. Grunt, grunt, grunt up the gravel road. CHTs flashing... oil temps slowing climbing... 210... 220... 230... 240... Just when I was about to pull over and let'r cool down a bit we hit the top and things cooled down nicely, but man-o-man was I thinking about it...

...bus seemed totally happy and drove great. Thinking of re-naming it Billy Goat. Hmm.

[airkooledchris]

...bus seemed totally happy and drove great. Thinking of re-naming it Billy Goat. Hmm.

that's where I ended up with my last engine in an 81 aircooled Vanagon. it could make any trip, but if you watched the CHT's along the way, you felt terrible for what you were assuming was torturing it.

I renamed that Vanagon "Rocky" for similar reasons to yours.

[Amskeptic]

...bus seemed totally happy and drove great. Thinking of re-naming it Billy Goat. Hmm.

that's where I ended up with my last engine in an 81 aircooled Vanagon. it could make any trip, but if you watched the CHT's along the way, you felt terrible for what you were assuming was torturing it.

I renamed that Vanagon "Rocky" for similar reasons to yours.

We need to aim for full-throttle enrichment that is transitory, this helps cooling, then try to find a reasonable compromise at part throttle (I know Chris that your CHTs get high at partial throttle, but I don't have your fuel map etched in my mind).
The BobD always cooled down at full throttle as the revs dropped. Above 3,000 feet, it was just bullet-proof never really hit 410 no matter the ambient temps. I would be leery of 450*. I could live with brief 430s - Dakota Digital that is, I never know what to think of VDO.
I am fearful of the stupid O2 program. But we have to remember! The cat engines *lived* at stochiometric and the O2 sensor made sure of that. We should be able to make a happy engine by unplugging the thing, and adjusting to the exhaust valves. Keep experimenting!
Colin

[Xelmon]

The spare AFM may need to come back out of the box for some testing on this, but id like to set my mixture to 12.0:1 at partial throttle (and as close to that at wot as possible) just to see how the engine likes it.

Try 12.5, which is max torque on the engine power curve. 12 is starting to actually fall off the power curve, and you are also wasting fuel at that point.

[Amskeptic]

]Try 12.5, which is max torque on the engine power curve. 12 is starting to actually fall off the power curve, and you are also wasting fuel at that point.

Been here. Discussed even. 12.5 is indeed good for power. 11.8 is good for cooling. Because it *changes* as the volumetric efficiency goes down, I shoot for 11.8 at torque peak and let it go up to 12.3 or higher as it revs on up to the horsepower peak.
Colin228milesofheadwindstoday@94*and 380*CHTmax1600sglport4kelevation

[reluctantartist]

Dakota Digital on #3. At 65MPH on the highway my head temps will usually be around 400-410. Going up large inclines, especially in the summer in California, can put the head temperatures near 450 at times. This has always freaked me out, but it just seems to be the way it goes.

Also, I have a VDO oil temperature gauge with sender in the oil plug. At sustained highway speeds, the oil will usually stay around 220-230. Again, going up large inclines in the summer, I've had the oil temp up to 260, which seems pretty high to me.

I have an 82 westy but it has the california electronic ignition. I have a VDO CHT and a thermometer near the CHT coupling in the engine compartment so I have an idea what the temp is to do the math...usually it is about 10 degrees warmer in the engine compartment than outside. My temps in town are around 325 -350 and 375 -390 on the highway. My oil temps are 190-220 at highway /interstate speed depending on the outside temperature; when it is over 85 it reaches 230 when I am at idle after sustained highway speed but is cooler when driving ( a ray tec confirms this too). I have taken great care to make sure the engine compartment is sealed very well and even removed the screen over the fan since I saw a post by Jack Raby stating he had something like >5 degree cooler temps without the screen. Is your compartment sealed including the licence plate flap? Do you know if you are running lean? Those temperatures seem high. I don't think the vanagon should really run any hotter than a bay.

[Amskeptic]

My temps in town are around 325 -350 and 375 -390 on the highway.
removed the screen over the fan since I saw a post by Jack Raby stating he had something like >5 degree cooler temps without the screen.

With those readings, put the damn screen back on.
Colin

[Jivermo]

DD on #3, 78 Westy-very recently tuned with the ITACM's visit. Ambient temp here in Miami is 88. X-way running in 4th at 65mph is around 370-355. Around the town is running 318-360. Like the responsiveness of the DD unit, which I installed last week. Temp home in the ashtray hole. Who can recommend a nice install point without chopping up the dash. Any good pics out there?