Engine temp vs timing vs gage

jberger · Samba Member Joined: November 17, 2003 Posts: 2476

Howdy,
I am in the process of dialing in my 79 Cali model after my rebuild. I installed a CHT gage and after calibration (65-70degrees off) proceeded to drive down the road and watched the gage climb to 350-375 (corrected) @ 55-60 mph. Going up any hill the gage just soars, it doesn't matter if it is in 1st 2nd 3rd or 4th gear it just keeps going. The spark plugs look leanish ( not scarey looking) and it seams to run fine, smooth and all. Any-hoo the timing is set 5deg atdc per california model with hoses connected, I decided to do a little experiment. With the retard hose connected I warmed the engine and drove it up a hill near my house in third gear floored holding 40-45 mph, the gage went from 350 to 425 (corrected) in about 4-5 seconds, ok, so then I disconnected the retard hose which should give me about another 12 degrees of advance right? Went up the same hill in the same manner and the gage went from 350 to 425 (corrected in about 4-5 seconds again, if the hill was longer I have no dought that it would have kept climing. I have no vaccume leaks, all cooling tin in place, timing set, still scarey temp readings, what do you think bad gage? Sorry to ramble this is just driving me nuts, and I would really hate to fry my new heads.

Thanks
Jason

Eaallred · Posted: Tue Apr 20, 2004 8:15 am Post subject:

The timing retard only takes effect at idle with the throttle completley closed. All other times, it's like it's not even there.
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Eric Allred

You have to remember something: Everybody pities the weak; Jealousy you have to earn.

jberger · Samba Member Joined: November 17, 2003 Posts: 2476

Eaallred · Posted: Tue Apr 20, 2004 8:56 am Post subject:

Double check your gauge in the kitchen oven. Check it every 50 degrees and make marks on the gauge face with a magic marker. It seems there's a bad batch of either senders or gauges latley. Mine is 50 degrees off at 300 degrees, and about 100 degrees off at 400 degrees. So you can't just double check it at one temperature and assume it's "x" degrees off throughout the readings.

Also, if you wanted, you could plug the port on the carb/intake for the vacuum retard, and put a loop in the hose from the retard port on the distributor to keep moisture out. Don't plug the port on the distributor, leave it open to the air. Voalia'. You have a normal distributor. Wink

_________________
Eric Allred

You have to remember something: Everybody pities the weak; Jealousy you have to earn.

jberger · Samba Member Joined: November 17, 2003 Posts: 2476

Randy in Maine · Posted: Tue Apr 20, 2004 9:26 am Post subject:

Jason,

I have the same 79 CA model you have. Recent overhaul with new square port heads. My CHT runs 325-350 (uncalibrated) all of the time and gets there in about 10 minutes of idling or driving about 5 minutes at 65 (3400). I am not sure how accurate it is. OT is usually in the range of 220-230 (also uncalibrated) but too high for my liking. I tried the same dizzy hose on - hose off thing you did with the same results. I know these were required to run lean to meet the 79 CARB requirements at the time, which would imply they would also run hot.

Question for you is what is the status of your cat converter? I have a theory that a partially clogged cat may keep head temps hotter than they need be. I have read here that others say that this engine was designed to run head temps "high" for emission requirements. My back up position is that perhaps the high head temps could be the result of a lame coil. I have a new CA only one ordered ($45) and will see if that helps. After that I may consider doing the "click richness adjustment" Eric speaks of in the AFM from earlier posts. Have you recently gone through an emissions test? Although I am not subject to testing here, I am going to run it through at the dealer to see what they say.

I am not convinced putting the gauge sending unit in boiling water water tells you anything that means anything. I would think that if you were going to put it anywhere you would put in a good 400* oven attached to some metal and then see what it read. Big difference between hot water (212*) and hot metal (400*).

The boiling water might work better for OT since they are around the same temp (212* vs 220*).

I have been studying the Probst FI Book but have gleaned very little with respect to the temp stuff.

Everybody out there is probably not as interested in this as we are, so you can PM if you would rather. I am becoming "consumed".

jberger · Samba Member Joined: November 17, 2003 Posts: 2476

Randy,
I guess this subject has been discussed to death, I will PM you.

Jason

Eaallred · Posted: Tue Apr 20, 2004 10:07 am Post subject:

With my gauge calibrated, my heads run under 300 idling at a traffic light, around 325 to 350 while driving around town, and around 375-400 on the highway at 70-75mph. 350 if i'm going downhill, and about 425 if i'm going uphill and pushing it. I really don't like temps over 400 myself. Makes me nervous on those long out of state drives.

I'm ready to tear my motor down and change out the cam to a Webcam 107i, put the deck to about .050", and set the dynamic CR to 7.5:1 to see what that will do for the head temps. Currently the motor is bone stock.
_________________
Eric Allred

You have to remember something: Everybody pities the weak; Jealousy you have to earn.

jberger · Samba Member Joined: November 17, 2003 Posts: 2476

Eaallred,
What kind of throttle possition do you have @ 70-75 mph?

Thanks
Jason

ratwell · Posted: Tue Apr 20, 2004 11:42 am Post subject:

Eaallred · Posted: Tue Apr 20, 2004 12:11 pm Post subject:

VWBusMan1 · Posted: Tue Apr 20, 2004 12:21 pm Post subject: Temperature calibration...

I have a CHT which I'd guess is about 100 degrees shy of where I guess my engine's running. Not a big deal if I keep that in mind. Also, just found a deep fat fryer temp guage at Big Lots for $1.99 that just happens to be about the exact length of my dipstick. Certainly, anything for less than 2 bucks has to be quality. I'll keep you posted once I get some readings from it. Good luck, Mark

Eaallred · Posted: Tue Apr 20, 2004 12:25 pm Post subject:

Randy in Maine · Posted: Tue Apr 20, 2004 12:52 pm Post subject:

Eric,

I just got off the phone with Tom the VDO tech support guy in PA 610-289-1390 x5. He told me that he doesn't know of any problems with the gauges or the sending units.

He just sent me the calibration charts for the gauges, but it is in 2 pdf files and I don't know how to get it to the samba.

I just sent it to ratwell. He can figure a way to get the file on here.

later,
Randy

Randy in Maine · Posted: Tue Apr 20, 2004 2:05 pm Post subject:

Well I have had a few minutes to re-look at the pdf files. Of limited help. I sent the VDO guy a request for some additional information. I will see what he sends back.

Sorry. My exuberance was premature.

Eaallred · Posted: Tue Apr 20, 2004 2:26 pm Post subject:

I've talked to a half dozen people with CHT gauges reading higher than what the real temp is in the last couple weeks. If VDO hasn't had any reports of faulty readings, my guess is they soon will.

I've tried different gauges with my sender, and they all read the exact same. I haven't tried using a different sender yet though.

I still like the VDO CHT gauge, it just looks like something funky happened.
_________________
Eric Allred

You have to remember something: Everybody pities the weak; Jealousy you have to earn.

ratwell · Posted: Tue Apr 20, 2004 3:08 pm Post subject:

I meant the senders. The gauges I have no issues with.
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'78 Westfalia CDN
'76 Doublecab
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jberger · Samba Member Joined: November 17, 2003 Posts: 2476

Is there a specific contact (at VDO) that all of us with questionable senders can e-mail? That would make for a bad day at the office.

westy78 · Posted: Tue Apr 20, 2004 5:07 pm Post subject:

Someone over on the Shop Talk Type 4rum just did the test in boiling water with pics. http://shoptalkforums.com/viewtopic.php?t=69332&postdays=0&postorder=asc&start=0

There is also some new info about driving in humid weather vs. dry weather that I have not seen before. Seems that the gauge will read higher when its raining Rolling Eyes

. I've given up getting mine accurate. I know that my engine runs great and my oil temps are good so I am going to just use the CHT temps I have now as a baseline for normal and watch for any strange fluctuations.

Your temps seem to be about what is normal for anyone with a stock engine from what I've been reading on the subject.
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Jasan C.
'78 Westy

VW Campmobile, it goes on vacation with you.


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