Vacuum hoses for a late 75 2.0l Porsche 914, Is it ok ? Options

[Villemi]

Hello

I have december 75 2.0l Porsche 94

My car is an US one and had a canister and air pump.

For late 74 diagram it was this one

(IMG:http://www.914world.com/bbs2/uploads_offsite/i48.servimg.com-23807-1640074350.1.jpg)
I don't have any more the canister and the air pump

My car has no anti flash back valve too.

Are you agree with the new diagram for my late 75 car ?

(IMG:http://www.914world.com/bbs2/uploads_offsite/i48.servimg.com-23807-1640039023.1.jpg)

It's difficult to understand when you have a 46years old !!!

[rjames]

You’re missing the decel valve. Isn’t necessary for the car to run, but it may prolong the life of your MPS.
It will also help with emissions by leaning out the mixture on deceleration.

[JeffBowlsby]

Please take my name off your modified diagram and retitle it for your purposes, as a courtesy to me. You can replace the diagram in the first post and delete the diagram posted. While I understand what his diagram is intended to do, it can take a life of its own if it gets circulated on the internet and its purpose is misunderstood.

I would not change a thing from diagram, as you describe your car. Find a flashback valve, decel valve and charcoal canister and hook them up. You will be glad you did.

[Villemi]

Hello Jeff,

Excuse me for using your diagram

I'm confused.

Thank you for your answer and help.

For the charcoal canister everything is out of the car.
My car had no flashback fire and no nipple on cylinder.

In Europe the 914 cars have not these parts.

[Villemi]

You’re missing the decel valve. Isn’t necessary for the car to run, but it may prolong the life of your MPS.
It will also help with emissions by leaning out the mixture on deceleration.

Can you explain to me how the decel valve is very ilmprtant for the MPS please.
I've seen somewhere that the decel valve was only for 1.7l and 1.8l 914.

[JeffBowlsby]

Hello Jeff,

Excuse me for using your diagram

I'm confused.

Thank you for your answer and help.

For the charcoal canister everything is out of the car.
My car had no flashback fire and no nipple on cylinder.

In Europe the 914 cars have not these parts.

Thank you Villemi. Please edit your first post to delete the first photo with my name on it. I am flattered by your use of may diagram to create your diagram, but you have edited it and my name is attached to it, where I have no control over your diagram.

As for the charcoal canister and flashback valve they are USA emissions requirements and may not be needed in Europe, but they do serve a good purpose. The charcoal canister reduces petrol fumes in the cabin and the flashback valve (spark arrestor) safely reduces crackcase pressures. Try and locate and install them to your benefit.

I further would not run the PCV valve hose to the filter box to prevent oil contamination of your air filter, put it on the intake planeum as my diagram shows.

[Villemi]

Hello Jeff,

Excuse me for using your diagram

I'm confused.

Thank you for your answer and help.

For the charcoal canister everything is out of the car.
My car had no flashback fire and no nipple on cylinder.

In Europe the 914 cars have not these parts.

Thank you Villemi. Please edit your first post to delete the first photo with my name on it. I am flattered by your use of may diagram to create your diagram, but you have edited it and my name is attached to it, where I have no control over your diagram.

As for the charcoal canister and flashback valve they are USA emissions requirements and may not be needed in Europe, but they do serve a good purpose. The charcoal canister reduces petrol fumes in the cabin and the flashback valve (spark arrestor) safely reduces crackcase pressures. Try and locate and install them to your benefit.

I further would not run the PCV valve hose to the filter box to prevent oil contamination of your air filter, put it on the intake planeum as my diagram shows.

And for the decel valve ? I have this part . Is it mandatory for the MPS healf ?

[BeatNavy]

The decel valve is not mandatory -- some people remove them, but it does help prevent the MPS diaphragm from blowing on hard overrun (very high manifold vacuum). The MPS under 'normal' driving conditions can have manifold vacuum anywhere from 0 psi in Hg (EDIT: corrected to in Hg) at wide open throttle to somewhere over 22 psi in Hg (EDIT: Corrected to in Hg) during overrun (downshifting). Vacuum pull significantly higher may damage or blow the diaphragm inside the MPS. The decel valve opens up to relieve the vacuum. You can adjust the level at which the decel valve opens. I can't recall where a stock decel valve is set to open -- maybe 20 in Hg?

Some people remove them completely as it brings RPM back to idle levels quickly and can enable faster shifting (e.g., for racing). If the devel valve is improperly adjusted you can get some strange behavior on shifting. Specifically, the idle RPM may hang too high for too long or drop too low or the engine may completely cut out.

Does that help, Villemi?

[Villemi]

The decel valve is not mandatory -- some people remove them, but it does help prevent the MPS diaphragm from blowing on hard overrun (very high manifold vacuum). The MPS under 'normal' driving conditions can have manifold vacuum anywhere from 0 psi/bar at wide open throttle to somewhere over 22 psi / 1.5 bar during overrun (downshifting). Vacuum pull significantly higher may damage or blow the diaphragm inside the MPS. The decel valve opens up to relieve the vacuum. You can adjust the level at which the decel valve opens. I can't recall where a stock decel valve is set to open -- maybe 20 psi?

Some people remove them completely as it brings RPM back to idle levels quickly and can enable faster shifting (e.g., for racing). If the devel valve is improperly adjusted you can get some strange behavior on shifting. Specifically, the idle RPM may hang too high for too long or drop too low or the engine may completely cut out.

Does that help, Villemi?

Yes thank you,

And for the fashback valve ? Mandatory ?
I don't understand where the hoses ar connected on the engine
Pics possible ?

[BeatNavy]

Flashback valve is another item that's not "mandatory" but is there for protection / prevention. Just like the decel valve, car will run fine without it, but I wouldn't recommend it. One hose from each head routes to it and then a third to the air cleaner.

It's supposed to relieve some crankcase pressure, provide some emissions control, and prevent a backfire flame from reaching the crankcase, IIRC. It's also called a "spark arrestor." Here's a pic (not mine). Two hoses on bottom -- one to each head, one on top to the air cleaner.

(IMG:http://www.914world.com/bbs2/uploads_offsite/forums.pelicanparts.com-17042-1640092632.1.jpg)

[StarBear]

The decel valve is not mandatory -- some people remove them, but it does help prevent the MPS diaphragm from blowing on hard overrun (very high manifold vacuum). The MPS under 'normal' driving conditions can have manifold vacuum anywhere from 0 psi/bar at wide open throttle to somewhere over 22 psi / 1.5 bar during overrun (downshifting). Vacuum pull significantly higher may damage or blow the diaphragm inside the MPS. The decel valve opens up to relieve the vacuum. You can adjust the level at which the decel valve opens. I can't recall where a stock decel valve is set to open -- maybe 20 psi?

Some people remove them completely as it brings RPM back to idle levels quickly and can enable faster shifting (e.g., for racing). If the devel valve is improperly adjusted you can get some strange behavior on shifting. Specifically, the idle RPM may hang too high for too long or drop too low or the engine may completely cut out.

Does that help, Villemi?

@BeatNavy 20 psi or 20 in Hg? I think I saw the latter recently on the 1.8L idle issue thread.

[BeatNavy]

The decel valve is not mandatory -- some people remove them, but it does help prevent the MPS diaphragm from blowing on hard overrun (very high manifold vacuum). The MPS under 'normal' driving conditions can have manifold vacuum anywhere from 0 psi/bar at wide open throttle to somewhere over 22 psi / 1.5 bar during overrun (downshifting). Vacuum pull significantly higher may damage or blow the diaphragm inside the MPS. The decel valve opens up to relieve the vacuum. You can adjust the level at which the decel valve opens. I can't recall where a stock decel valve is set to open -- maybe 20 psi?

Some people remove them completely as it brings RPM back to idle levels quickly and can enable faster shifting (e.g., for racing). If the devel valve is improperly adjusted you can get some strange behavior on shifting. Specifically, the idle RPM may hang too high for too long or drop too low or the engine may completely cut out.

Does that help, Villemi?

@BeatNavy 20 psi or 20 in Hg? I think I saw the latter recently on the 1.8L idle issue thread.

Correct, inches mercury. Sorry for confusion. So I guess 20 in HG converts to more like .7 bar. I corrected my original post.

[DRPHIL914]

The decel valve is not mandatory -- some people remove them, but it does help prevent the MPS diaphragm from blowing on hard overrun (very high manifold vacuum). The MPS under 'normal' driving conditions can have manifold vacuum anywhere from 0 psi/bar at wide open throttle to somewhere over 22 psi / 1.5 bar during overrun (downshifting). Vacuum pull significantly higher may damage or blow the diaphragm inside the MPS. The decel valve opens up to relieve the vacuum. You can adjust the level at which the decel valve opens. I can't recall where a stock decel valve is set to open -- maybe 20 psi?

Some people remove them completely as it brings RPM back to idle levels quickly and can enable faster shifting (e.g., for racing). If the devel valve is improperly adjusted you can get some strange behavior on shifting. Specifically, the idle RPM may hang too high for too long or drop too low or the engine may completely cut out.

Does that help, Villemi?

Yes thank you,

And for the fashback valve ? Mandatory ?
I don't understand where the hoses ar connected on the engine
Pics possible ?

@Villemi

in 1975-1976 the factory did not put head vents on these cars and therefore no antiflash back valve, futhermore if you look at the research on this by LN engineering, Len Hoffman and Jake Raby did they found it better NOT to vent the heads( i just found this out last week and read thru all their research and documentation they did)
- so you can follow the diagrams but if your heads are US heads with no vent then you will not hook up the anti-flash back valve.

ALSO 75-76 US cars did not have a PVC the factory deleted it. I would not use a PVC , the stack at the oil filler is different, but what i would do and oh i did do is i connected the crank case vent hose to a catch can and that to the air cleaner. That will keep the oil vaper out of your air filter like Jeff said. If you put the hose to the manifold like the early cars had you are going to have what will amount to a high idle due to pulling too much air , just like a vac leak.
- so - late cars had no PVC no head vents and no flash back valve.

Phil

[TX914]

I have a 76 and I'm in agreement with @DRPHIL914 . I also recommend running the decel valve.

[DRPHIL914]

I have a 76 and I'm in agreement with @DRPHIL914 . I also recommend running the decel valve.

(IMG:style_emoticons/default/agree.gif) i left that off but i think that is the general concensus that with Djet you should have the decel valve hooked up, to help prevent an issue with the MPS- i need to put mine back on.
one other issue is that in the US these cars had the smog pump too but those are long gone and i have never seen a car with one on that worked, so there would be that air injection port on the head at the exhaust port that would be plugged if all the smog stuff is removed.

[BeatNavy]

Phil is correct. Something else I didn't key on -- your heads likely don't have vents. Can't hook up a flashback valve if you don't have head vents.

And Phil's right, Len Hoffman recommends against the head venting. On the heads he did for my 2056 he plugged up the vent.

I'm full of all kinds of (mis) information today (IMG:style_emoticons/default/wink.gif)

[StarBear]

Phil is correct. Something else I didn't key on -- your heads likely don't have vents. Can't hook up a flashback valve if you don't have head vents.

And Phil's right, Len Hoffman recommends against the head venting. On the heads he did for my 2056 he plugged up the vent.

I'm full of all kinds of (mis) information today (IMG:style_emoticons/default/wink.gif)

Either not enough beer or too much, probably. Easy to correct if the first case. (IMG:style_emoticons/default/beerchug.gif)

[Villemi]

After this discuss do you validate my diagram ?

On my car I'have the decel valve, no charcoal ,no PCV, no air pump, no flashback valve.

(IMG:http://www.914world.com/bbs2/uploads_offsite/i48.servimg.com-23807-1640127282.1.jpg)

[Bleyseng]

That looks correct but you will have to plug the 13mm fitting at the stack nipple without the charcoal hose going to it.
Do you have a throttle body with 2 ports? If so you can hook uip the vacuum advance hose to one of them instead of it laying there underneath the runners.