[xj] Air injection rail

Hi everyone,

A quick followup to my mystery water thread:

I removed the hose assembly from the air injection rail to
the air pump (which is non-operational in my car although
I’ve not yet removed it). I drove the car for a couple of
days with the inlet/outlet for the injection rail (where
that hose assembly had been) open just to see what happened.

There was never any splatter or water or dried coolant which
is what I was really concerned about. I had feared that
there could have been some sort of leak allowing coolant
into the combustion chamber and that that’s where the water
had been coming from. Apparently that wasn’t the case.

I had noted that when the car was running at full rev quite
a bit of smokey exhaust (read untreated by the cat not
smokey as in something odd) would come out of the outlet
with pretty decent force. Once I was sure nothing crazy was
being ejected out of the rail, I went down to Autozone and
purchased a 3/4’’ neoprene cap and a properly sized clamp.

With the inlet/outlet capped, I’ve noticed since that I’m
getting slightly better fuel economy. It’s not a huge
difference (maybe .5-1 mpg average over a couple of tanks
with it being mostly city driving). But, there is an
improvement.

This makes me wonder if more than just exhaust was being
wasted through that hole and more importantly it gets me
thinking about whether just having that rail on top of the
cylinder head is a good thing or not. Obviously although
it’s meant to inject air, it can also be a path for air to
go back through (as mine was clearly doing).

If these tubes and rail are an open path to each cylinder,
is it actually changing the physics of the combustion
chamber? As in providing a spot where things that should
normally be contained by the valves and pistons are being
pushed out into the pipe? And also, as they’re all
connected, could it have some sort of (good or bad) leveling
effect on the compression from cylinder to cylinder?

I believe someone on here posted about having fully removed
the rail and plugged the holes. I’d be interested in
knowing more about that.

Thanks–
Drew Ward – '87 XJ-6
New Orleans, United States
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As I recall the air injection tubes and passages don’t go directly to the
combustion chamber. They go to the exhaust ports, just behind the exhaust
valves. I don’t think you’ll find liquid splatter in that area even if
there was a coolant leak into the combustion chamber…unless perhaps it
was a very gross leak where actual pools of coolant were being pushed out.

My experience, FWIW, is that the tips of the spark plugs will discolor (to
green-ish) or actually show small droplets of coolant, though…especially
if you check them after the car has sat overnight

Cheers
Doug Dwyer
Longview Washington USA
1995 XJRFrom: “XKdreams” drew.ward@calleteach.org

I removed the hose assembly from the air injection rail to
the air pump

There was never any splatter or water or dried coolant which
is what I was really concerned about. I had feared that
there could have been some sort of leak allowing coolant
into the combustion chamber and that that’s where the water
had been coming from.

If these tubes and rail are an open path to each cylinder,
is it actually changing the physics of the combustion
chamber?

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: http://www.jag-lovers.org/lists/search.html

To remove yourself from this list, go to http://www.jag-lovers.org/cgi-bin/majordomo.

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In reply to a message from XKdreams sent Sun 1 May 2011:

I removed the air pump and all associated lines from my XJC
1976 and plugged the head. The car needed to be tuned as it
was then running alittle lean. But other than that it is
running great. There is a significant amount of info on this
subject in the archives.

Philip Prior
Adelaide, South Australia
2004 XJ8 X350
1966 S Type 3.4 ltr. Auto
1976 XJ6C Convertible (DHC)
www.myjaguarstory.com
�Life is too short not to own a Jaguar (or three)�–
The original message included these comments:

I believe someone on here posted about having fully removed
the rail and plugged the holes. I’d be interested in
knowing more about that.


Plutos
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: http://www.jag-lovers.org/lists/search.html

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