1974 914 1.8, the mystery of the EC-A and EC-B Options

[wonkipop]

i'll be dropping the information we have gathered over Dec 2021 in with a set of posts.

the material was prompted by mr b ( @JeffBowlsby ) who observed that for the 74 MY there was an EC-A and an EC-B engine. mr b's thought was that the EC-A was a 49 states car and and EC-B was a californian car for emissions.

mr b's view was rational and reasoned. 73 EA engines are 49 states. 73 EB engines are california. 75 engines are documented in factory literature as EC-a (49 states) and EC-b (california). the logic should follow?

BUT

as per the mystery of the 914, the truth about 74 1.8s turns out stranger than fiction (or common sense?).

the material is not necessary to running a 1.8 or having fun with a 14. (IMG:style_emoticons/default/smile.gif)

its for historical purposes and as information to 74 1.8 owners to assist with restoration if they want it.

[JeffBowlsby]

Wonk,

You deserve an award for this charcoal can research, it’s well documented and clearly presented.

Can’t speak for others but changing the airflow direction thru the can, especially knowing how the can is actually constructed without the long internal supply tube as depicted in the booklets basically creates a short circuit nearly eliminating the intent and actual functional efficiency of the system.

Don’t understand the factory logic for the change. What did they know that is not obvious to us? Did they not see the internal plumbing within the can? I’m inclined to keep with the early air hose routing scheme because it seems like the best technical solution.

[wonkipop]

Wonk,

You deserve an award for this charcoal can research, it’s well documented and clearly presented.

Can’t speak for others but changing the airflow direction thru the can, especially knowing how the can is actually constructed without the long internal supply tube as depicted in the booklets basically creates a short circuit nearly eliminating the intent and actual functional efficiency of the system.

Don’t understand the factory logic for the change. What did they know that is not obvious to us? Did they not see the internal plumbing within the can? I’m inclined to keep with the early air hose routing scheme because it seems like the best technical solution.

somewhere in my research last year i did come across the details of the actual EPA test procedure for the evap emission system.

this is from memory but i could probably find it again.

but it went something like this.
drive the car for a prescribed period of time, it was a fairly long period of time and i think a certain number of miles were involved and it was a kind of simulation of a typical commute drive.

car then driven into special sealed room and switched off. the room contained hydrocarbon sensors. (70s primitive tech sensors?).

car left in there for prescribed period of time. something like an hour or two.

hydrocarbons detected in the atmosphere of room had to be under a certain threshold of x ppm.

pass or fail.

so the test was for the static phase of the operation of the canister system after switch off. the test was not for a dynamic phase (ie purge). manufacturers were expected to keep a fleet of test cars and monitor the system for 50,000 miles or 5 years. at the time the tests were introduced cars had not had the system installed for 5 years. so that was in the future. but if systems failed in the long term manufacturers would have been expected to replace faulty components under warranty. VW or porsches view would have been replace the canister.

i know how it works in my industry. anything required to be certified is designed to pass the test. nothing to do with the real world. ie a fire rated window that has to be certified to be 1/2 hour bushfire rated is that. if it lasts 31 minutes it passes. if it lasts 29 minutes it fails.

i think the canister is all about that. cobbling up a system, using shared universal parts, to get very different types of cars through the test.

getting a cabied 914/6 or 911 through the test would have been a nightmare? they would have exposed as much cross sectional area of charcoal as they could between the carb connected hose and the fan feed (atm vent) hose. so they plugged that carb hose line into the end of the can with the small plenum created by the spring - there is hot fuel in a carb bowl after switch off thats gassing like no tomorrow?

getting a fuel injected 914 or VW through would have been a breeze.
some fuel vapor coming down a tiny hose from the fuel tank which would have been far less heated or subject to heat after switch off. they would have positioned the open hose to atm (fan) with as much charcoal between it and tank vapor line as possible with a view to the long term life of the can as it would have walked through the EPA test. the hose to the air cleaner has the filter between it and the atmosphere to help it and to "seal" vapors in. the EFI cars just would not have been dumping in anything like the vapor load of a carb car at hot shutdown.

i think the early 4 cylinder 914s just got the system porsche tuned for the 914/6 by default? then someone at the factory woke up and said, hey we are not building 914/6s anymore and we can get the cans to last longer the other way around. one thing is for sure, VW had the penny counting overlords going over everything. they would never have missed a trick where a $ was concerned.

i think there is an element of cynicism involved? in the sense of getting through the certification process number 1 rather than necessarily operating well over 5 years.
and they were cynical.
everyone is.
thats why the EPA caught them out in 73?
and again more recently?

pollution gear is funny stuff. all about very specific govt. authority tests conducted within almost laboratory parameters.

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