A Green Bus In Portland

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pickledBus
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A Green Bus In Portland

Post by pickledBus » Sat Jul 20, 2019 9:21 am

While looking through my maintenance log I realized it has been five years since Colin was last here. Time really goes by quickly...

(Sorry in advance for no pictures, hopefully Colin will post some but I was too busy to ever take out my phone the whole time)

We started off the visit with the mandatory coffee and sat down to discuss the plan for the day but quickly got sidetracked into the trials and tribulations of achieving AFM nirvana. In the end we are left with some questions to ponder:
1. With an injection every other spark, which two cylinders are the happiest by getting an injection on the exhaust stroke and which are left to suffer with older fuel?
2. What black magic is the ECU doing to determine the pulse width of the injectors? How does RPM balance against airflow?
3. If you are on the edge of lean power loss does the excess air act as a heat exchanger to carry heat away during exhaust much like excess fuel would. Or is it just smaller explosion equals smaller heat generated?

Eventually we got around to the main "enjoyable" task of the day which was to disassemble, assess and repack the front wheel bearings. The passenger side presented with throughly cooked grease and a washer that was completely loose. So loose that the outer bearing had actually beaten a substantial groove into it that had to be sanded down flush. Luckily the bearings themselves along with their races in the hubs did not look to have substantial wear and the remainder was a straightforward repack and reassemble. Outer bearing was "German, made in Spain", the inner was a "Timken".

The driver side was a similar situation but with the added discoloration of rust from water intrusion through the speedometer cutout in the dust cap. The dust cap that Colin took one look at and declared "That is unacceptable." While I proceeded with the cleaning and packing I could hear sounds of expertise in ball pean hammer usage being applied to misshapen dust caps coming from the other side of the bus. When assembly time comes Colin returns my dust cap with its new hammered finish, one of a kind you know, and looks on expectantly for me to complete the reassembly. It was at this point that it all went wrong. For you see the speedometer cable has a square end which fits into a square hole in the dust cap and thus can count the revolutions of the wheel. The new hammered finish had turn this square into something decidedly un-square. After assessing what tools we had to re machine the hole a set of small diamond grinders for a dremel was picked. The thinnest one was chosen to discourage accidental rounding of the now trapezoid. After a number of fitting iterations the trapezoid was made square once again and further assembly finished without issue.

The remainder of the visit was spent on fixing some misrouted vacuum lines and a fairly severe vacuum leak from the bore of the piston in my "blocked off" EGR. All in all I look forward to future visits because, for me, the misadventures, experimentation, breaking things and then fixing them is all a part of the fun of working on these vehicles.

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Amskeptic
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Re: A Green Bus In Portland

Post by Amskeptic » Sat Jul 20, 2019 9:13 pm

pickledBus wrote:
Sat Jul 20, 2019 9:21 am
Time really goes by quickly...

pickledBus wrote:
Sat Jul 20, 2019 9:21 am
We started off the visit with the mandatory coffee and sat down to discuss the plan for the day but quickly got sidetracked into the trials and tribulations of achieving AFM nirvana. In the end we are left with some questions to ponder:
1. With an injection every other spark, which two cylinders are the happiest by getting an injection on the exhaust stroke and which are left to suffer with older fuel?
2. What black magic is the ECU doing to determine the pulse width of the injectors? How does RPM balance against airflow?
3. If you are on the edge of lean power loss does the excess air act as a heat exchanger to carry heat away during exhaust much like excess fuel would. Or is it just smaller explosion equals smaller heat generated?
This was brain food. This was good fun. This was my chance to see that you are very intuitive.

Image


I have had a day of screwing things up as I continue to experiment.
However ...
I can now replicate some outcomes. Today, my fuel economy log went 19.1 17.9 16.7 15.4 14.7 and that means I have control! Now we are back to 15.4 and good head temps.

1. We do not know which cylinder pairs trigger the injector pulse. We have to ask the ECU.
2. Books make it sound simple, but there is some elementary logic in there that I think we are not privvy to. WhoHowWhat leans the mixture at a steady idle rpm signal even as I ratchet the wiper to pig rich??
3. I say no. VW used air injection in 1973/74 to oxidize all hydrocarbons in the exhaust stream, that excess air will find something to burn. I think the low quantity of injected fuel just doesn't have enough calories to heat things up. I like that thought.

Image

pickledBus wrote:
Sat Jul 20, 2019 9:21 am
Colin returns my dust cap with its new hammered finish, one of a kind you know, and looks on expectantly for me to complete the reassembly. It was at this point that it all went wrong. For you see the speedometer cable has a square end which fits into a square hole in the dust cap and thus can count the revolutions of the wheel. The new hammered finish had turn this square into something decidedly un-square. After assessing what tools we had to re machine the hole a set of small diamond grinders for a dremel was picked. The thinnest one was chosen to discourage accidental rounding of the now trapezoid. After a number of fitting iterations the trapezoid was made square once again and further assembly finished without issue.
Yes, yes, yes, that was a "1" in the pantheon of disastrous detours.

pickledBus wrote:
Sat Jul 20, 2019 9:21 am
for me, the misadventures, experimentation, breaking things and then fixing them is all a part of the fun of working on these vehicles.
It IS fun, and you have a family, a little one, to share the results with ...
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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