[T2] ECU and larger displacement

[Sami Dakhlia]

Chris,
Yes, a methodical checklist is what I need. Now I had double and triple
checked the timing and set it to about 7.5 btdc. (It's a newish svda
043-905-205.) Used a simple strobe light pointed at an aftermarket laser
engraved aluminum  timing scale from busdepot. Better than the plastic ones
that sag.
But let me check total advance and adjust by a few degrees forward and
backward with test drives in between.
Cheers,
Sami

On Wednesday, 10 August 2016, c.dreike <c.dreike at verizon.net> wrote:

> Sami,
> We also did not check the timing. Sorry I didn't think about that. I do
> have a timing light.
> Next time.
> We need a check list.
>
> Chris
>
>
> On 8/9/2016 11:01 PM, Sami Dakhlia wrote:
>
>> 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=776
>>>>>>>> 1&sid=26d79b8f4581a7c3219fbb1581ad5523
>>>>>>>>
>>>>>>>> Thoughts?
>>>>>>>>
>>>>>>>> Sami
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>>>>>>>>
>>>>>>>
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