[T2] ECU and larger displacement

[Sami Dakhlia]

Hi Chris,

Yes, it would be wise to check the gauge before I do anything else.
This being said, when I first turned the ignition key on the cold
engine, the CHT read 75 F, i.e., it correctly displayed the ambient
temperature.

CHT at idle seems about right to me, given that my cooling flaps
should be operating properly (new thermostat).

Best,
Sami

On Tue, Aug 9, 2016 at 7:26 PM, c.dreike <c.dreike at verizon.net> wrote:
> One other possibility is a poor calibration on the CHT gage/thermocouple.
> Next year drop the thermocouple into a pot of boiling water and see if you
> read 212F. Will have to look up the temp of boiling water at your altitude.
> Idle temp after 10-15 minutes should top out at around 280. Odd that its so
> close to cruising temp.
>
> Cheers,
> Chris
>
>
>
> On 8/9/2016 6:27 PM, Sami Dakhlia wrote:
>>
>> Quick update:
>> I relocated the thermocouple, wedging it quite firmly between two
>> fins. See photo:
>> https://drive.google.com/open?id=0B3JXI3RTjfDCamQybXVXTHA3anM
>> (ring-shaped connector is cut off)
>> I think it's close enough to the spark plug hole and it will have to do.
>>
>> Took the bus on a 25-mile test drive from Topanga to Malibu and back.
>> Here is an elevation map for the outbound journey:
>> https://drive.google.com/open?id=0B3JXI3RTjfDCN3hKb2lLdjhoM0k
>> [Start altitude: 420 metres, End altitude: 71 metres, Maximum
>> altitude: 420 metres, Minimum altitude: 1 metres, Distance: 31.3 km,
>> Total ascent: 236 metres, Total descent: 585 metres]
>> (BTW, the elevation map was created at
>> https://www.doogal.co.uk/RouteElevation.php)
>>
>> Pleasant 75 F ocean breeze.
>> Idle CHT: 365 F
>> Easy cruising at 45 mph CHT: 370-380 F
>> Slight 7 deg. incline at 40 mph, 4th gear: 395 F
>> Same in 3rd gear: 380 F
>> Return trip, climbing up Topanga: 410 at 30-35 mph, 3rd gear 3-5 deg
>> incline.
>> 390-414 F in 1st and 2nd gear at 5-15 mph on 10-20 deg incline.
>> Throughout, oil temp gauge showed 210-220 F, went up to 240 during the
>> last half mile up the steep hill.
>>
>> So it's still running hot. That's all for now. Leaving California in a
>> couple of days, so further troubleshooting will have to wait until
>> next year.
>>
>> Cheers,
>> Sami
>>
>> On Tue, Aug 9, 2016 at 12:15 AM, Sami Dakhlia <sami.dakhlia at gmail.com>
>> wrote:
>>>
>>> Hi,
>>>
>>> Fellow list member Chris Dreike offered more than a helping hand
>>> today. He pulled his wideband O2 sender and gauge from his magnificent
>>> DD bus and clamped the sender on my bus's '75 exhaust pipe; then sat
>>> in the backseat, holding the gauge, while I cruised up and down I-405.
>>>
>>> The readings' range was between 11.5 and 12.5, even at WOT,
>>> invalidating my hypothesis that the engine might be running lean. On
>>> the contrary, it might be running a tad rich.
>>>
>>> This also means that there is no pressing need to replace the ECU for
>>> an early '76 one. The '75 FI system designed for a 1.8-liter engine
>>> appears to adequately cope with a 2-liter engine, i.e., not cause a
>>> lean-running condition at WOT.
>>>
>>> It appears that I was misled by a poorly installed CHT sender.
>>>
>>> Thank you, Chris! Many thanks also to Bob, who offered to send me a
>>> later-model ECU from his stash. And to Jon, Syd, and Dennis for
>>> offline conversations and advice. I shall henceforth strive to worry
>>> less and just enjoy the ride!
>>>
>>> Cheers,
>>> Sami
>>>
>>> On Wed, Aug 3, 2016 at 2:15 PM, Sami Dakhlia <sami.dakhlia at gmail.com>
>>> wrote:
>>>>
>>>> Hi Dennis,
>>>> I had removed the crush washer to adjust for the presence of the
>>>> sensor ring. Did not hear any unusual noises and did not see tell-tale
>>>> marks around the hole. :-( Too bad, because I really wanted to believe
>>>> in the escaping hot gases story...
>>>>
>>>> The injectors are the same for the various years. So I'm still
>>>> thinking it could be the ECU. I wonder if with a 1976 ECU (only the
>>>> displacement changed between '75 and '76, the AFM did not -- and in
>>>> particular was of the 6-prong type without air temp sensor, so
>>>> compatibility with the rest of FI system is more likely), the
>>>> injectors would fire more often for a given AFM position?
>>>>
>>>> With a ECU swap, the AFM would then need to be re-adjusted (adjust
>>>> spring to make it stiffer), effectively increasing the air flow rate
>>>> at which the AFM reaches the full open position. In other words, just
>>>> swapping the ECU would not be enough. And together with the stiffer
>>>> AFM, the ECU would get meaningful information as the AFM reacts to
>>>> WOT.
>>>>
>>>> Good idea to do a dyno test, perhaps I'll be able to do that on my
>>>> next trip. A proper diagnostic would make a lot of sense before I
>>>> concoct more hypotheses!
>>>>
>>>> Thanks again,
>>>> Sami
>>>>
>>>> On Wed, Aug 3, 2016 at 1:46 PM, Dennis Gentry <dennis.gentry at gmail.com>
>>>> wrote:
>>>>>
>>>>> Did you use a crush washer plus the sensor ring, or just the sensor
>>>>> ring?
>>>>> If you left off the crush washer, the plug might extend into the
>>>>> cylinder a
>>>>> tiny bit more, making it run hotter?  If hot gases were escaping, you
>>>>> should
>>>>> have been able to hear it, plus it would leave tell-tale marks around
>>>>> the
>>>>> hole.  (Try running with a spark plug only screwed in a couple of turns
>>>>> to
>>>>> see what I mean. :)
>>>>>
>>>>> I like your hypothesis about it running lean, since too lean will
>>>>> definitely
>>>>> cause high CHT.  Are you thinking that the injectors meant for a 1.8 L
>>>>> engine are failing to keep up with 2 liters of displacement at high
>>>>> RPMs?  I
>>>>> don't think that's the cause, since (I think) the injectors were the
>>>>> same
>>>>> from 1975 through 1979, when the stock engines became 2.0 L in 1978 or
>>>>> so.
>>>>> You could check for too-lean and for reasonable vs. too-low power
>>>>> output by
>>>>> putting it on a dyno and measuring the CO/O2 levels in the exhaust, but
>>>>> I
>>>>> imagine there is an easier way to do it that I'm not thinking of right
>>>>> now.
>>>>>
>>>>> Good Luck!
>>>>> Dennis
>>>>>
>>>>>
>>>>>
>>>>> On Wed, Aug 3, 2016 at 11:46 AM, Sami Dakhlia <sami.dakhlia at gmail.com>
>>>>> wrote:
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> I'm back in California for the month, my annual pilgrimage to the US
>>>>>> to work on my '75 bus (and see family, too :)
>>>>>>
>>>>>> I must admit that I'm just not enjoying the bus as much as I used to;
>>>>>> it's just a big headache. Too much time spent on fixing things, not
>>>>>> enough time spent traveling. Last year I installed a Dakota Digital
>>>>>> head temperature gauge and the temp readings went through the roof!
>>>>>>
>>>>>> We suspected that the O-ring crimped on the thermo-couple didn't allow
>>>>>> for a proper seal of the sparkplug, allowing hot gases to escape and
>>>>>> cause the high temp readings. I've now relocated the sender, wedging
>>>>>> it between the fins, not under the sparkplug. Not perfect, but a
>>>>>> better solution will have to wait until the day I have to pull the
>>>>>> engine.
>>>>>>
>>>>>> While the temp readings are no longer outrageous, they're still north
>>>>>> of what's acceptable, sometimes above 380 F. And the engine is lacking
>>>>>> power, even by vw bus standards.
>>>>>>
>>>>>> Which brings me to a new hypothesis: the engine is running lean when
>>>>>> pushed to the limit (highway driving at 60mph, or climbing hills).
>>>>>> It's a '75 model and came stock with a 1.8 liter engine. I have since
>>>>>> "upgraded" to a 2 liter engine. I have so far assumed that the AFM
>>>>>> would properly compensate for the extra displacement, but now I'm
>>>>>> wondering.
>>>>>>
>>>>>> BTW, I also adjusted the AFM following the instructions at
>>>>>>
>>>>>>
>>>>>> http://www.itinerant-air-cooled.com/viewtopic.php?f=50&t=7761&sid=26d79b8f4581a7c3219fbb1581ad5523
>>>>>>
>>>>>> Thoughts?
>>>>>>
>>>>>> Sami
>>>>>> _______________________________________________
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>>>>>
>>>>>
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