engine bay hoses 1.8 L Jet, colors, arrangements etc Options

[wonkipop]

this topic arose in the thread concerning hose colors for D Jet cars.

i've started a new topic so it does not mess the other thread.

first thing to say is that the factory manual is more scant on L-Jet information than for D-Jet. There are no hose schematics with the clarity of the D-Jet layouts for the L-Jet. Secondly some of the information on the L-Jet is misleading.

First thing.

car 1974 1.8.

Green vacuum line from Distributor.
Seems to be the same as the D-Jet cars.

There is a green vacuum (retard) line out of the distributor body to the throttle body.
I think i am right saying its the retard side (sometimes gets dyslexic on that).

The green line in this photo is an original vacuum line. Along with the crankcase vent hose these are the only two lines i did not replace on my car. The crankcase line is moulded to an S - shape and we decided to stay with the original. its still sealing ok.
Same with the distributor line. We checked and still pliable and it was sealing so it stayed. We cleaned it up a little. I also left the intake manifold seals on as we did not go that far in - requires disassembly of the intake manifold. They are still in good sealing condition though looking a little aged.

There is a black vacuum (advance) line out of the distributor to the throttle body.

The green line from the distributor was the only colored line still apparent on my car.

[wonkipop]

second bit of information is that hose layout for charcoal cannister evap vapor system is incorrect on some diagrams floating around.

i've come across this before.

i believe the arrangement and design of the charcoal cannister changes at some point -
possibly when the cannister is moved into the engine bay in the 1.8 cars.

earlier cars had a charcoal cannister up front near the fuel tank.
the earlier design has the fan blower hose connected to the end of cannister along with the small diam tank expansion/fume hose. the hose to the air cleaner connected at the opposite end of the cannister.

diagram from factory manual showing early layout.
the schematic shows the fan blower hose arrangement.







the schematics for the 1974 (and later) 1.8 (and 2.0 L as well?) are from the emission warranty i have. These show that the arrangement of the cannister hoses changes.
The fan blower hose now connects at the opposite end of the cannister to the expansion/fume hose from the fuel tank and the air cleaner hose. this conforms to the hose arrangement in my car which i have never altered and i believe remains original.
i have replaced the hoses last year and simply copied what was there.

I have a view on this. I believe the original design did not work and the cannisters failed to purge during open road cruise driving. the blower hose was too long to push fumes back into the air cleaner for burning off. there is no valve in this very simple system. the charcoal is the valve. once it becomes saturated the hydrocarbon fumes escape to the atmosphere (via the fan hose or via the air cleaner after passing through the filter - in fact i can smell it in mine at the moment because i am sure the charcoal filter is saturated and the car needs a good run to purge it).

the charcoal filter cannister is located on the rear engine bay firewall in my car. which is a jan 74 build. i think it was shifted one more time in 74 to just beside the battery and stayed there until the end of production. i think they did this progressively to shorten the fan hose to make this system work. the hose plumbing is the same in both positions in the engine bay. i've looked at a few engine bay images to confirm that.

The hoses were dark grey/black standard hose colors on my car.
They had faded and have been replaced with new dark grey/black hoses.

starbear has already amended the diagram shown below for the charcoal cannister hoses in the other thread.

[wonkipop]

an error in the factory manual.

this notated image in the factory manual identifies #5 as a pressure regulator.

it should be the decal (de-accelleration) valve.

the pressure regulator, or by its full name, the fuel pressure regulator looks similar to the decal valve but is on the lhs of the engine under the air cleaner.

[wonkipop]

the above error in the factory manual gets me to something that has been puzzling me since we re-newed most of the vacuum lines and hoses last year.

this "decal" valve was just floating around in the rhs of the engine bay of my car, not attached to anything. both i and my mechanic were a bit troubled by this as we could not believe either porsche or vw would do this. i've been looking at it ever since. its always been there like that since i bought the car 31 years ago and i had no real cause to think about it until the hose renewal work last year.

as part of the work we did on the car we also had to change the fuel pump as the original was kaput. i am attempting a rebuild of that original fuel pump but for now we have plumbed an in line 2 port pump replacement. we incorporated a high pressure fuel filter into the fuel system after the pump as that is good practice (porsche themselves began to do it on later cars like the 924). we mounted that fuel filter off a handy bracket just behind the battery mount tray which had a handy hole already in it.

i now realise that bracket and hole is where the desal valve should mount. and the desal valve itself has an inbuilt bracket. except the one i am looking at in my engine bay doesn't have a bracket and the more i look at it, the more it looks like a fuel pressure regulator that has been plumbed in there. i am going to try and get to the bottom of it today with my mechanic.

if it is a fuel pressure regulator it does not seem to affect the engine running or coming off revs. mystery for the moment.




i have noticed searching around on the web that in this image, showing at 2.0L motor there is a very similar looking valve installed as the one floating in my engine bay.

[wonkipop]

got to the bottom of the decal valve mystery.

pulled out the floating valve and found the part # still on it.
Bosch 0 280 160 200.

its a fuel pressure regulator valve subbed in for the decal valve.

not done by me so predates 1989 and by original owner or dealer/mechanic.

we thought about it.
we reckon its a clever emissions cheat from back in the day.

most people here, first thing they did with their 911s back then, was to block the small vacuum line of the decal valve with a ball bearing. or they just pulled it out and plugged it. owners hated the decal valve and the slow idle drop, not what you wanted cornering a 911 off and on throttle?
think it was done a lot in the USA too.

subbing in a fuel pressure reg valve does the same thing. plugs the small vac line.
but passes visual inspection on an emissions inspection if not looked at closely?

i think i will leave it in, its part of the history.
now i know what it is. we might have a bit more of a think about whether its doing anything - we don't think it does anything wrong?

car drives great, always has. comes off throttle nicely.
never had any serious backfire issues, just occasional pops and burbles out of the back.

will just mount it properly.
which i would have to do anyway even with reinstalled decal valve given new fuel filter.

[Van B]

I just stumbled onto this thread and now realized that my canister hoses are backward lol... thanks @wonkipop !

[Lockwodo]

I just stumbled onto this thread and now realized that my canister hoses are backward lol... thanks @wonkipop !

I'm just looking at this canister connection issue too. Just to confirm, does this mean the the diagram "Late-1974 Porsche 914 2.0L D Jet Fuel Injection Vacuum Hose Diagram" below attributed to Jeff Bowlsby is incorrect as regards the hoses hookup to the canister?

https://bowlsby.net/914/Classic/zTN_FI_Hose..._Late1974_A.jpg

[wonkipop]

I just stumbled onto this thread and now realized that my canister hoses are backward lol... thanks @wonkipop !

I'm just looking at this canister connection issue too. Just to confirm, does this mean the the diagram "Late-1974 Porsche 914 2.0L D Jet Fuel Injection Vacuum Hose Diagram" below attributed to Jeff Bowlsby is incorrect as regards the hoses hookup to the canister?

https://bowlsby.net/914/Classic/zTN_FI_Hose..._Late1974_A.jpg

no, it does not mean jeff's diagram is incorrect.
he knows his 2.0 L cars backwards.

it just means that the 1.8s are plumbed up the way discussed here.
only the 1.8 hose diagram that had been modified from an earlier 1.8 diagram was under discussion and "dispute".

its a grey area that has i think simply not been worked out with 100% certainty.

for sure there were two different practices in relation to plumbing these cans.
the VW schematic for all VW cars from 1969 onwards.
the porsche schematic for all porsche cars from 69 -73.

there is a couple of ways it could have panned out.

all that i know is that 74 1.8s with engine bay can got plumbed VW's way and from there all 1.8s to the end were plumbed VW's way.

i think you have to be careful assuming there was some kind of consistency to this across the entire range for the entire production period - esp when the two companies had contrary views on the plumbing arrangement for the can.

where it diverges, and where it changes, or if it changes, across the range of 914s over the years is the hard part and i don't think its fully known yet.

[JeffBowlsby]

Thanks Wonk. I have said before that your research on that emissions brochure is commendable and I have always appreciated your support and logical rationalization. Both hose routing methods function, so use whichever you prefer. But to my eye, the brochure solution is questionable in its functional effectiveness.

The hose configuration in the brochure results in a short circuit for fuel vapors, in that they enter the one end of the canister and are immediately 180'd back out the adjacent hose, propelled by positive air pressure from the other end of the charcoal can and the suction air from the engine intake so that the vapors do not travel through much charcoal media - with resultant limited effectiveness at cleansing the air path from fuel vapor - the entire intent of this system.

My diagram conforms to the 'early' configuration in that the positive pressure supply air input hose forces fuel vapors to travel through the entire charcoal media, which are propelled by both the positive airflow from the fan and the suction air from the engine intake. To my eye it works better at minimizing fuel odors and directing them back into the engine where they are combusted. This is also the hose configuration in my 50K mile 1974 2.0L that had original hoses when I acquired it about 20 years ago from the original owner.

[wonkipop]

yes jeff. (IMG:style_emoticons/default/smile.gif)

i think there was probably a similar kind of technical discussion going on between the two manufacturers as your summary above? otherwise why would they be different and still use the same basic can. the can is a VW part that porsche also used on 911s. a kind of "which way does this thing work best question" - with contrary decisions on final layout.

the more i think about it i believe that 2.0 L cars, being a porsche engineering led engine program to replace the 6, the more i think it 100% logical they stuck with the porsche layout as per your diagram on those particular cars. porsche don't change the 911 until 73 (which is the 74 model year). i believe there is no reason 73 and 74 914 2.0s would not have stuck with the porsche plumbing at porsche's insistence. explains that outlet on the tin on the lhs with a 2.0 engine. something i did not know about until recent thread in other section you pointed out. (i told you i know almost nothing about 2.0s! rarely see another 914 down in aus let alone peer into the engine compartment, only one i ever got to look at closely was my old mates and it was a euro spec crayfords car without any emissions gear).

the factory manuals seem to indicate the smaller base engine cars had the plumbing revised to the VW layout in august 71. (72 MY).


my own opinion is that neither system works well. (IMG:style_emoticons/default/smile.gif) no valve to the atmosphere. just charcoal absorbing (until it is saturated). they are both as deficient as each other? classic VW rudimentary thinking along "passive" lines. a bit like VW's pressurisation of the windscreen washers from the spare tyre? certainly the VW system relies on you driving the car frequently on the open road or freeway at cruise to purge it. otherwise it doesn't work too well at all.

the most interesting historical aspect of it all is that porsche engineering and vw engineering appeared to disagree with each other over such a small item. given that porsche had the "luxury" deal with VW to do a huge amount of their engineering R + D in the 1960s its a sign of what was to become a much bigger argument as soon as h nordoff died?

EDIT

a thought that has come to my mind since doing all that EC research and uncovering the details of the 73 VW emission cheat that was settled behind the scenes was that the EPA might have audited VW thoroughly. its possible they uncovered the differences to the two approaches between Porsche and VW using the same component and questions were asked. the move by porsche to adopt the VW plumbing in the 911 may have been nothing other than a paper work convenience and a bureaucratic decision rather than have the system probed into more closely by the EPA. remembering they were supposed to operate under warranty for 50,000 miles. VW had more at stake than porsche given the numbers of cars that were already on the road. its likely that porsches decision to alter the system had nothing to do with whether their layout worked better than VWs (which it well might have). a case of who had the most corporate muscle in an arm wrestle to get out of an awkward moment with a third party.

[Van B]

I rerouted my hoses and frankly it looks dumb and I hate it lol…. My first thought was exactly what Jeff said about poor vapor flow.

Also, the hose from my fan shroud to the canister is really old so, it may not be original route but the car has very likely spent most of it’s life with the logical set up.

I’ll be putting it back to the conventional arrangement tomorrow.

[wonkipop]

I rerouted my hoses and frankly it looks dumb and I hate it lol…. My first thought was exactly what Jeff said about poor vapor flow.

Also, the hose from my fan shroud to the canister is really old so, it may not be original route but the car has very likely spent most of it’s life with the logical set up.

I’ll be putting it back to the conventional arrangement tomorrow.

(IMG:style_emoticons/default/laugh.gif)

yes, you could never accuse the 1.8 of having a sano engine bay.
i kind of like the criss cross - general tangled look they seemed to be going for! if the vacuum hoses etc were a haircut it would be bob marley's. (IMG:style_emoticons/default/beer.gif)
i like showing off the engine bay to 356 dudes with their twin carbies and watch them roll their eyes in horror.

EDIT.
if i had to make an educated guess i would say that VW were concentrating on the static state of the can.
after the engine is switched off and the car is standing.
perhaps explains the logic of their plumbing.
max distance (and charcoal surface area) from fuel vapor line in and fan bleed blower line (unregulated opening to atmosphere)?

when the can is purging the hoses could go at either end. its an airflow through the can whether you think its pushing/pulling air/pressurizing. makes no practical difference to the can in the end. will work both ways?

thats the way i think of it when i look at the VW logic.
1) percolation flows at very low velocity.
2) drawn higher velocity flows at purge.

[Van B]

You’re probably right, but my pride and vanity obligate me to ignore your logic. (IMG:style_emoticons/default/bootyshake.gif)

[wonkipop]

You’re probably right, but my pride and vanity obligate me to ignore your logic. (IMG:style_emoticons/default/bootyshake.gif)

you got to remember my favourite plane is the wobbling goblin.
linear logic isn't one of my strengths. i get attracted to contrarian themes.
i'm the kind of a-hole that would have stood in front of a general and said, who cares if it doesn't fly - you can't see it on a radar mate......and then got a headache from trying to make my smart alec comment work later on, when the general would have said, ok.
make it fly---a-hole.
(IMG:style_emoticons/default/beer.gif)

mike pointed out to me why the original porsche design with the can in the front trunk couldn't work in the 914. see if you can pick it out. its different in the 914 from the 911 in terms of where the can ended up in relation to the fuel tank and expansion tank. condensation in the short vapor line has something to do with it.

our 1.8s don't have the short vapor line. classic design mate. another reason to slap yourself on the back for buying one. you can pack your wife's fur coat in the front trunk for a quick trip up to the snow for a romantic weekend of skiing and not have her complain about stinking of petrol fumes while wrapped up in it standing on the balcony.

meanwhile......its all set to go mental here in lygon street. next suburb across.
ferrari fans are descending like a horde of red ants. i can already hear revving engines and car horns blaring as they go blasting through my ghetto.

vegas is in for a treat if its still got an italian population like martin scorcese movies make out. and if ferrari are still on fire next year. walloped the opposition today. and its a good looking car too. (IMG:style_emoticons/default/beerchug.gif)