[T2] ECU and larger displacement

[c.dreike]

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
>>>>> _______________________________________________
>>>>> type2 mailing list
>>>>> type2 at type2.com
>>>>> https://www.type2.com/lists/type2/listinfo
>>>>
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