[v12-engine] Decelleration cut off

I can say that if the car has overrun valves and no fuel cutoff, it does
not slow down much when you take your foot of the accelerator. I find it
much more pleasant to drive with a cork fitted in each of the overrun valve
feed pipes.

Mike,
Tell me more. I have a 1981 S3 XJ12, should I try the same and see how it
drives, are their any side effects, what are the benefits. The feed pipes,
are these, the 1" dia. 3" long rubber tubes from the air cleaner to the
intake manifold.From: Mike Morrin mikem@southern.co.nz

At 10:40 am 21/04/99 +1200, Mark Price wrote:

I can say that if the car has overrun valves and no fuel cutoff, it does
not slow down much when you take your foot of the accelerator. I find it
much more pleasant to drive with a cork fitted in each of the overrun valve
feed pipes.
From: Mike Morrin <@Mike_Morrin1>

Mike,
Tell me more. I have a 1981 S3 XJ12, should I try the same and see how it
drives, are their any side effects, what are the benefits. The feed pipes,
are these, the 1" dia. 3" long rubber tubes from the air cleaner to the
intake manifold.

Yes. I just found some corks the correct size and pushed them in. Easily
reversable. If your car has a decelleration fuel cutoff, then plugging the
valves will not make much difference.

I think that the only purpose of the overrun valves is to reduce exhaust
emissions caused by oil being sucked past the piston rings and inlet valve
guide seals.

Mike

Mike Morrin wrote:

At 10:40 am 21/04/99 +1200, Mark Price wrote:

  From:   Mike Morrin <mikem@southern.co.nz>

I think that the only purpose of the overrun valves is to reduce exhaust
emissions caused by oil being sucked past the piston rings and inlet valve
guide seals.

Is this the main source of the oily substance running out of the throttle bodies?

Bob.>

Mike

  From:   Mike Morrin <mikem@southern.co.nz>

I think that the only purpose of the overrun valves is to reduce exhaust
emissions caused by oil being sucked past the piston rings and inlet valve
guide seals.

Negative. It’s to reduce hydrocarbon emissions caused by misfiring,
which often occurs at very high manifold vacuum. The EPA probably
presumes you have a working PCV system and good valve stem seals.

Incidentally, Bywater claims these valves are very important even
without concern for emissions, since the misfiring can result in
backfiring and blow your mufflers apart.

– Kirbert | Palm’s Postulate:
| If anything is to be accomplished,
| some rules must be broken.
| – Kirby Palm, 1979

Yes. I just found some corks the correct size and pushed them in. Easily
reversable.

Sounds good. Might be a good idea to check them every now and then
for deterioration.

If your car has a decelleration fuel cutoff, then plugging the
valves will not make much difference.

Hmmmm. I’m not so sure. I think perhaps that, with overrun cutoff,
having these valves working might just INCREASE deceleration
“compression”. After all, you’ll be pumping more air through the
engine, won’t you?

– Kirbert | Palm’s Postulate:
| If anything is to be accomplished,
| some rules must be broken.
| – Kirby Palm, 1979From: Mike Morrin mikem@southern.co.nz