The transmission on my 85 XJ6 was rebuilt about 18 months ago. To
remove the transmission they obviously removed at least some of the
exhaust system. I have had an exhaust leak since I have owned the car
(about 13 months) and finally decided to fix it. I found part of the
leak was that most of the exhaust manifold mounting nuts were not
completely tight. Tightning the nuts substantially inproved the leak but
there was additional leakage at the joint between the manifold and the
down pipe. I ordered new gaskets for that joint and what I got were two
soft metal rings about two inches in diameter, “C” shaped in cross
section and filled with a black substance. I have three of the brass
nuts removed (the fourth is stripped) and I find that there is nothing
like the recieved gaskets in place in the car. Before I fight further
with the stripped nut, did I get the correct gaskets or were they just
left out when the transmission repair was done?
nuts removed (the fourth is stripped) and I find that there is nothing
like the recieved gaskets in place in the car. Before I fight further
with the stripped nut, did I get the correct gaskets or were they just
left out when the transmission repair was done?
Thanks
Dick
Yes, they’re correct, and they probably were left off.
Henry Fok
XJ Web Admin
Cum catapultae proscriptae erunt tum soli proscripti catapultas habebunt------------------------------------------------------------------------
All your base are belong to us.
I am contemplating making the exhaust system on my 1986 series III
XJ6 true duals. My questions are how do I deal with the oxygen
sensor?Can it be eliminated? Should it be eliminated? AND, will
this be an improvement?
Thank-you
Dave Redline–
der
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
You need the oxygen sensor, and if you divorce the system you’d need two
sensors…and I don’t know how you’d make that work.
Or, run with one oxygen sensor measuring only half the exhaust. Not sure how
that would work either…might be OK if you were sure that the measured 3
cylinders were running the same as the unmeasured 3. Hmmm. Might be workable
but not ideal.
I have some doubts that splitting the system will make any more than a
slight improvement. The main restriction comes from the mufflers and, if
they are clogging up, cat converters.
Doug Dwyer
Longview Washington USA
1995 XJRFrom: “der” davidredli@aol.com
I am contemplating making the exhaust system on my 1986 series III
XJ6 true duals. My questions are how do I deal with the oxygen
sensor?Can it be eliminated? Should it be eliminated? AND, will
this be an improvement?
In reply to a message from Doug Dwyer sent Fri 2 Mar 2007:
David:
Doug knows thse cars better than I do. So, I can only opine on
about 60 years worth of fixing and abusing cars of most varieties.
Last count is 61 over the years and I think I missed a few!!
The old six cylinder Chevrolets did very nicely on a
split manifold. In that case, the split was nowhere near as ood as
the split on your car. The benefit was reduced back pressure by two
pipes and two mufflers. Also enhanced in most cases by straight
through mufflers in lieu of the restrictive OEM mufflers of the
time.
Therefore, I think you would gain enough to feel it in the seat.
The Thusly, the O2 sensor is the issue.
Use two, and a switching device auto or manual to transmit
readings from alternate units to the ECM.
Use two and connect them together so they would transmit a
composite signal to the ECM.
Use one on one pipe and hope the other cylinders are running
about the same.
I think either 2 or 3 is workable. Perhaps an electronic genius on
this list has other thoughts.
Carl–
The original message included these comments:
I have some doubts that splitting the system will make any more than a
slight improvement. The main restriction comes from the mufflers and, if
they are clogging up, cat converters.
I am contemplating making the exhaust system on my 1986 series III
XJ6 true duals. My questions are how do I deal with the oxygen
sensor?Can it be eliminated? Should it be eliminated? AND, will
this be an improvement?
In reply to a message from der sent Fri 2 Mar 2007:
Dave:
PS!
After thought.
You do need an O2 sensor signal.
There is such a thing as an electronic substitute that sends
data without benefit of exhaust temperatures or O2 content??
Carl–
The original message included these comments:
I am contemplating making the exhaust system on my 1986 series III
XJ6 true duals. My questions are how do I deal with the oxygen
sensor?Can it be eliminated? Should it be eliminated? AND, will
this be an improvement?
Hey, go like the Range Rover – an O2 sensor per cylinder – cost a friend
$1200 just to have new ones put in all 8 exhausts 'cause the dealer couldn’t
decide which were bad. (yeah, right)
:]–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.
Doug Dwyer wrote:
You need the oxygen sensor, and if you divorce the system you’d need two
sensors…and I don’t know how you’d make that work.
Or, run with one oxygen sensor measuring only half the exhaust. Not sure
how that would work either…might be OK if you were sure that the
measured 3 cylinders were running the same as the unmeasured 3. Hmmm.
Might be workable but not ideal.
I have some doubts that splitting the system will make any more than a
slight improvement. The main restriction comes from the mufflers and, if
they are clogging up, cat converters.
In reply to a message from Cannara sent Fri 2 Mar 2007:
Alex;
A Rover dealer with no multimeter or with no scruples?
Carl–
The original message included these comments:
Hey, go like the Range Rover – an O2 sensor per cylinder – cost a friend
$1200 just to have new ones put in all 8 exhausts 'cause the dealer couldn’t
decide which were bad. (yeah, right)
A customer with too much $!–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.
cadjag wrote:
In reply to a message from Cannara sent Fri 2 Mar 2007:
Alex;
A Rover dealer with no multimeter or with no scruples?
Carl
The original message included these comments:
Hey, go like the Range Rover – an O2 sensor per cylinder – cost a friend
$1200 just to have new ones put in all 8 exhausts 'cause the dealer couldn’t
decide which were bad. (yeah, right)
I am contemplating making the exhaust system on my 1986 series III
XJ6 true duals. My questions are how do I deal with the oxygen
sensor?Can it be eliminated? Should it be eliminated? AND, will
this be an improvement?
Thank-you
Dave Redline
I tend to agree with Doug on this one. There would be too many variables for
the computer to satisfy. If you have your heart set on modifying your
vehicle this way, get an aftermarket Engine management system that is can be
calibrated for dual exhaust systems, such as Electromotive’s TEC system
ttp://www.directignition.com/products/ (No affiliation). It is kind of
expensive, though, and involved. to install. The lies when the system enters
closed loop… I think it would definitely upset the fuelling, as Doug said.
In the old days when we wanted dual exhaust, we would fit both sides of our
newly bent exhaust on the car, enough so that the pipe exited past rear
bulkhead.feet past the collector (before it went around the rear
suspension). we painted the length of pipes after the collector with white
enamel, and ran it hard on the street (loud!) for about fifteen minutes. I
can hear the noise pollution Nazi’s coming out of the woodwork as I say
this, so be careful where you run! When the car was put back up on the lift
there would be scorch marks nearer to the collector end where the exhaust
gases impinge on the tube. Now the theory was that because the exhaust
pulses were more or less 180 degrees? out of phase, the scorchmarks would
never line up. The rarefaction pulse and the actual exhaust plug would could
be made to co-mingle however if a crossover pipe would bridge from where the
scorch mark started on one pipe to where it stopped on the other, looking
down towards the tail of the car. The difference in the location of these
spots would generally be some multiple of the length of stroke. Joining them
would in theory, cancel ‘some?’ of the sound pulse / pressure wave, and
would allow the car to run a much less restrictive exhaust system without
the obtrusive loudness associated with say cherry bombs or even open
exhaust. I’ve seen as much as 20 horse from doing this alone, and midrange
torque is usually upped a BUNCH. But with today’s catalysts, this method of
tuning becomes very difficult to do, as much of the exhaust energy is
dissipated in the converters.
In reply to a message from der sent Fri 2 Mar 2007:
Dave,
I’m not certain about the following, so I welcome comment.
Because O2 sensors are high-impedence devices, one should be able
to wire two (one for each exhaust) in parallel. Each sensor can be
modeled as a voltage source in series with a resistor. The two
resistors form a voltage divider. The output voltage of the two in
parallel is their numerical average (V1 + V2)/2 and should be
exactly the same as if one sensor sniffed the average 02 resulting
from 6 cylinders.–
The original message included these comments:
I am contemplating making the exhaust system on my 1986 series III
XJ6 true duals. My questions are how do I deal with the oxygen
sensor?Can it be eliminated? Should it be eliminated? AND, will
The problem is that their individual delta voltages are also halved, meaning
the ECU, even if the impedance change was ok for it, would see half the effect
of one side needing correction.
When I measured the O2 sensors some time back, they seem to be about 4000 Ohms
internally. If that’s what the ECU circuitry expects, because it’s measuring
a current flow, then having two in parallel would also increase the current
the ECU sees by about 30-50%. But, that all depends on what the ECU’s own
internal resistance is.
In any case, we wouldn’t get something for nothing, because the ECU’s
decisions affect all cylinders’ fuelling, yet 2 parallel O2 sensors can both
be saying “more fuel”, one saying so, or none saying it. Since the O2
sensor’s characteristic output voltage isn’t particularly linear with O2
concentration, combining two this way may well cuase the ECU to miss the
proper setting. Might be interesting to try, since the Lambda control circuit
is basically tick-tock (on-off-on…).–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.
Robert Wilkinson wrote:
In reply to a message from der sent Fri 2 Mar 2007:
Dave,
I’m not certain about the following, so I welcome comment.
Because O2 sensors are high-impedence devices, one should be able
to wire two (one for each exhaust) in parallel. Each sensor can be
modeled as a voltage source in series with a resistor. The two
resistors form a voltage divider. The output voltage of the two in
parallel is their numerical average (V1 + V2)/2 and should be
exactly the same as if one sensor sniffed the average 02 resulting
from 6 cylinders.
In reply to a message from der sent Fri 2 Mar 2007:
So if my '77 has no O2 sensor or Catalytic converter, would I
realize any NOTICEABLE increase in performance by splitting the
system?..–
345 DeSoto
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
In reply to a message from Doug Dwyer sent Sat 3 Mar 2007:
Why not have a custom collector made to handle the volumn of the
six cylinders,use one O2 sensor then split to two pipes. As long as
there is no restriction where the collector is you should be able
to exhaust more gas. The O2 sensor reads the exhaust gas from all
six cylinders thus reading an average for each not O2 for each as
on the Rover. Therefore you should be able to use a single O2
sensor but with a possibilty of slightly bad mixture. By the way,
our XJS V12 has two O2 sensors. Why not check out how that is done?
I’d offer some advice but I’m only starting to learn auto
electronics.
Stephen J. Niznik
86 XJ6 Cobalt Blue
86 XJ-SC V12
88 XJS V12 Coupe
88 mustang GT Conv.
The original post inquiered about splitting 4.2L 6 cyl. exhaust to
true duals.–
dizmando
jefferson hills PA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
I am contemplating making the exhaust system on my 1986 series III
XJ6 true duals. My questions are how do I deal with the oxygen
sensor?Can it be eliminated? Should it be eliminated? AND, will
this be an improvement?
The engine will run perfectly OK without the O2 sensor/Lambda system,
Dave - it’s a legal, not a mechanical, requirement…
Most of this talk of exhaust is about engineering the sound rather than
the performance. As it is, the exhaust from all six will blend into
mixed sound picture with basically fairly even pressure in the
manifolds. As the exhaust back pressure is part of engine tuning the
result of a split in itself is uncertain…
I don’t think it is worth while from the performance point of view, but
the sound is likely to be different. Personally; the less I hear from
the engine and exhaust the better - I know I’m going fast in a car with
performance to match without it…
The problem is that their individual delta voltages are also halved,
meaning the ECU, even if the impedance change was ok for it, would see
half the effect of one side needing correction.
When I measured the O2 sensors some time back, they seem to be about
4000 Ohms internally. If that’s what the ECU circuitry expects,
because it’s measuring a current flow, then having two in parallel
would also increase the current the ECU sees by about 30-50%. But,
that all depends on what the ECU’s own internal resistance is.
Hm, Alex, the O2 sensors do not work as resistances - they are actually
producing voltages to prod the ECU into proper actions. Coupled in
paralell the question is more if the ECU would lean out with one high,
or fatten according to one low…?
In case this is of any use, I split the system on our 4.2 series 2 about
150,000 km ago. Removing the front mufflers produced a note that I
considered a little too noisy, so I replaced them with a pair of small
stainless glasspacks. IMO the result is pleasing but restrained, especially
around 1500-2500rpm. I wouldn’t want to change it. And setting mixtures is
so much easier.
Power increase? Wouldn’t have a clue! Even if it were 10bhp, I can’t feel
a 10bhp difference. It runs sweetly, sounds good, gets 30mpg at 110kph
cruise in O/D, and that’s enough for me!
George
Doug writes
Given all the restriction from the mufflers I’m inclined to say “no”. But
I’ve never done it so I’m talking outta my hat.
For more power I’d change the muffler arrangement first and then split the
exhaust if you wanted the last few drops of improvement, so to speak.===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: Jag-lovers Forums - Jag-lovers
