Ok Let’s talk about the XJ-S,
I was wondering, will a typical XJ-S trip computer work in my 1985 3.6 liter
XJ-S. My old one looks the same but the milage function tells me I’m alway
getting 255.9 miles per gallon. everything else works fine.
Mike Hoffman
I always new the 6 got better mileage.-----Original Message-----
Ok Let’s talk about the XJ-S,
I was wondering, will a typical XJ-S trip computer work in my 1985 3.6 liter
XJ-S. My old one looks the same but the milage function tells me I’m alway
getting 255.9 miles per gallon. everything else works fine.
Mike Hoffman
My parts book says they have different numbers but look the same so there
must be an internal difference.
Paul Weston
1989 XJ-S UK spec>From: “Mike Hoffman” mhoffman1@neo.rr.com
To: “Robison John (AdW/QAM5)” John.Robison@us.bosch.com, “Xj-S”
xj-s@jag-lovers.org
Subject: Re: [xj-s] XJ-S
Date: Mon, 11 Mar 2002 15:39:00 -0500Ok Let’s talk about the XJ-S,
I was wondering, will a typical XJ-S trip computer work in my 1985 3.6
liter
XJ-S. My old one looks the same but the milage function tells me I’m alway
getting 255.9 miles per gallon. everything else works fine.
Mike Hoffman
5.3 litre (US) DAC4296
5.3 litre (UK) DAC4295
3.6 litre DAC4452
Mind you, if it’s doing 260mpg, I’d be tempted to leave it alone…
Andrew 1989 3.6 manual coupe UK-----Original Message-----
From: owner-xj-s@jag-lovers.org [mailto:owner-xj-s@jag-lovers.org] On
Behalf Of Paul Weston
Sent: 12 March 2002 09:53
To: xj-s@jag-lovers.org
Subject: Re: [xj-s] XJ-S
My parts book says they have different numbers but look the same so
there
must be an internal difference.
Paul Weston
1989 XJ-S UK spec
From: “Mike Hoffman” mhoffman1@neo.rr.com
To: “Robison John (AdW/QAM5)” John.Robison@us.bosch.com, “Xj-S”
xj-s@jag-lovers.org
Subject: Re: [xj-s] XJ-S
Date: Mon, 11 Mar 2002 15:39:00 -0500Ok Let’s talk about the XJ-S,
I was wondering, will a typical XJ-S trip computer work in my 1985 3.6
liter
XJ-S. My old one looks the same but the milage function tells me I’m
alway
getting 255.9 miles per gallon. everything else works fine.
Mike Hoffman
List,
I wanted to thank everyone for the info on the trip computer. I don’t
understand how something that looks so small and simple can be so expensive!
I have one more question concerning the pre HE trigger unit mounted in the
ditributor. That damn thing is so expensive is there anything I can do or
install to replace this that would be cheaper. I Know the digital P
injection just reads a pulse from I believe the negative coil wire? Could
the D jetronic system be set up to do the same thing. Would the crane cams
ign system replace the trigger unit?
Thank You,
Mike hoffman
At 12:48 PM 12-03-02 -0500, you wrote:>List,
I wanted to thank everyone for the info on the trip computer. I don’t
understand how something that looks so small and simple can be so expensive!
I have one more question concerning the pre HE trigger unit mounted in the
ditributor. That damn thing is so expensive is there anything I can do or
install to replace this that would be cheaper. I Know the digital P
injection just reads a pulse from I believe the negative coil wire? Could
the D jetronic system be set up to do the same thing. Would the crane cams
ign system replace the trigger unit?
Thank You,
Mike hoffman
The pre HE dizzy has a coil type pickup for ignition and a trigger board
with a pair of epoxy covered reed switches for triggering the injector pulse
cycle.
The coil should be easily available from Jag wreckers, must be many around
as they do not wear out. The reed switch has a limited life.
I still have my original dizzy coil & reed switch ( both good ) but now have
a Crane cams ignition and an aftermarket EFI so do not use the original
dizzy parts but plan to keep them.
You may be lucky and get a second hand reed switch unit from a wrecker but I
have heard they are hard to find ( true or false ? ). You can actually buy
reed switches for a
few dollars each, starting point being Radio Shack who will have the
cheapest they can buy in. If you can get suitable reed switches you can
fab a board to mount them on. This is not a sophisticated device.
Maybe somebody has tried this before, could be in the archives.
Anything that gives two pulses per dizzy rev can do the trick, and there are
other ways of doing it that may be in the archives. It has to be a pulse
suitable for the ECU, which will eliminate some methods.
As you mention, you could count ignition coil pulses and divide them down to
get the equivalent pulses needed to trigger the injectors.
That would be more sophisticated and would not trigger in the same part of
the cycle as before unless synched with a spark plug event, but that might
not matter much.
Easy to make after spending a fair bit of R&D to get the first one right.
Good luck !
Richard Dowling, Melbourne, Australia, '79 XJ-S & '85 XJ6.
“Subject: Re: [xj-s] XJ-S”
Hey, guys. I have to jump in to say that using the “Subject: XJ-S” on the
XJ-S List makes no sense at all and plays hell with the Archives. At least
put an add-on of ‘Trip Computer’ or something if you’re going to continue
this thread. PLEASE!
Jay Gilmour
At 06:33 2002-03-13 +1100, Richard Dowling wrote:
The pre HE dizzy has a coil type pickup for ignition and a trigger board
with a pair of epoxy covered reed switches for triggering the injector pulse
cycle.
Neither of my V-12’s are Pre-HE, but it seems to me that you could
faciliate replacing the reed switches using an optical trigger (which is
fairly popular with most of the aftermarket ignitons, such as Crane).
You’d fashion a shutter wheel to go onto the distributor shaft (or mount
underneath the rotor - if you screw it into the rotor you should use nylon
screws), then run two IR Emitter/detector pairs (one each for A and B bank).
You could either mount the IR hardware 180’ out from each other, and put
ONE hole in the shutter disc, or you could mount them above and below one
another and put two holes the shutter disc above each other (the IR
hardware would need appropriate blinders to make sure that you’re not
picking up pulses intended for the OTHER bank.
The IR emitters would just be wired to ignition power (through an
appropriate current-limiting resistor as you would for any other LED), and
the pickup sensors would probably have to be wired through a transistor for
appropriate signal amplification for the ECU.
+V on all of the LED and sensors could be a single shared line, with the
emitters going to ground (inside the distributor), and each of the sensors
having a trigger output wire exiting the distributor (whether that runs to
an external box with the amplifying transistors or if they’re on a little
board inside the distributor itself is a judgement call) - external makes
them easier to test and allows you to relocate them somewhere less harsh,
internal makes the whole thing more transparent to inspection, where some
state inspector is more likely to say “this ignition mod isn’t approved by
the state board of whatevernot”).
Your biggest issues will be space in the distributor and your own
fabrication skill.
I suspect you could contact Crane and order up some of the component parts
to do this, as “replacements” for a regular Crane ignition pickup. You’d
need a shutter wheel, but as long as you can find one that mounts, it
doesn’t matter if it is for a 4, 6, or 8 cylinder application (you’ll blank
off the holes/slots that aren’t needed).
Of course, just finding a suitable replacement reed switch (the component
part, not the whole Jaguar assembly) would be cheaper and easier, but if
they fail all that often, replacing the trigger with a non-mechanical one
could be better in the long run.
other ways of doing it that may be in the archives. It has to be a pulse
suitable for the ECU, which will eliminate some methods.
Perhaps someone with a scope will consider capturing the stock signal and
post it on snapshots?
As you mention, you could count ignition coil pulses and divide them down to
get the equivalent pulses needed to trigger the injectors.
That would be more sophisticated and would not trigger in the same part of
the cycle as before unless synched with a spark plug event, but that might
not matter much.
Triggering a little too early or a little too late could affect the
completeness of the burn (due to “stale” fuel atomization), but within a
couple of degrees, I doubt you are going to experience a significant
difference.
Keep in mind that the same engine is found in the E-Type and earlier XJ12
models with carbureators on it - accuracy of the injection timing won’t
keep your engine from running - in fact, it shouldn’t even affect the fuel
econony. Why is that? Because what you’d really be doing is just moving
the burn efficiency from one set of cylinders to a different set within
each bank - at any point, you have a cylinder on the bank which is going to
fire 180’ out from another one in that same bank - to take the A bank for
example A1 and A6 fire at the same point within the crank revolution, but
are 180’ distributor degrees out from one another. If you fired the
injectors for the A bank just before the intake valve for A1 opened, then
the fuel atomization would be at it’s lowest efficiency by the time 4A
opened (the last cylinder on the A bank to fire in the order). If you
changed the injection by 180’, then 6A would be the most efficient and 3A
would be the least. Delay by 60’, 5A becomes the most efficient and 1A the
least, etc. This is why sequential multiport is superior - the fuelling
for each cylinder is equally as efficient because the fuel is being sprayed
at the same time relative to each ignition event.
The injectors are operated on separate banks only because the EFI regulates
fuelling separately (in response to O2 feedback), not because of any
believed gain in fuelling efficiency. The timing of the injector events
should not be very critical, so long as it is only occurring once per rev.
Therefore, while I’d be hesitant to use an inductive lead on a plug for
fuel triggering (that one plug misfires and the whole bank goes out), using
a counter circuit on the ignition could work - after all, isn’t that what
the later EFI does anyway? You could take your signal from the ignition
pickup, removing the need to fashion an optical assembly in the
distributor. Of course, that requires a little more sophistication on the
part of the triggering apparatus, but it can’t be too complicated. If you
wanted to precisely mimic the relative timing of the injector bank-fires to
the ignition to appear the same as the stock config, that’d be a different
matter - but as I explained above, I doubt it is an issue to worry about.
— http://jaguar.professional.org/
Sean Straw '88 Jaguar XJSC 5.3L V12 (LHD) ‘Black Cat’ 65K
Marin County, California '85 Jaguar XJS 5.3L V12 (LHD) ‘Bad Kitty’ 210K
'69 Buick GranSport 455 V8 324K
From Sean:>Neither of my V-12’s are Pre-HE, but it seems to me that you could
faciliate replacing the reed switches using an optical trigger (which is
fairly popular with most of the aftermarket ignitons, such as Crane).You’d fashion a shutter wheel to go onto the distributor shaft (or mount
underneath the rotor - if you screw it into the rotor you should use nylon
screws), then run two IR Emitter/detector pairs (one each for A and B bank).
a) I have just overhauled my original dizzy and bought 2 spare HE units,
one complete and one less cap and rotor.
I was going to do what you suggest to provide a synch signal to the new
Motec EFI if ever I went for sequential injection. I judge it a fairly
difficult thing to stuff another shutter wheel in there plus sundry other
parts to go with it. Just getting the standard Crane Cams parts in there
for ignition is no joke but it is possible.
If needed I would go to some trouble to find decent reed switches, my
originals have done 130,000km and 23 years so they are not as fragile and/or
life limited as other things.
b) The original reed switches may not have switched to ground or +12V, so
you have to be careful if substituting a transistor switch. My experience
is Lucas engineers had a penchant for dreaming up weird circuits for ECUs -
well for everything, really. I once put my scope on the vacuum bellows
manifold sensor used in the early EFI systems to check it. It was full of
spikes and peaks and troughs. How the thing worked is beyond me, but it did
work. Could have been made on Mars, or on Venus, and I would be none the
wiser.
Perhaps someone with a scope will consider capturing the stock signal and
post it on snapshots?
Good idea. My original EFI is taken out and I never had to scope the trigger
board, so can’t help.
Triggering a little too early or a little too late could affect the
completeness of the burn (due to “stale” fuel atomization), but within a
couple of degrees, I doubt you are going to experience a significant
difference.
I had some talk with the Motec founder on the subject of sequential
injection before buying his EFI. I got a base model which is not
sequential. He said that for street use it was hardly worth the effort,
what you might gain in some load/rev situations you could lose elsewhere.
For highly tuned engines it is a different story. He mentioned that
intuitively you expect the injector, mounted on top of the inlet valve,
should squirt fuel right into the cylinder as the valve opens. Well, quite
often that does not allow full atomisation and mixing and the results are
not good. He claims some sequential injection systems squirt onto the back
of a closed hot valve and get better atomisation and hence better results.
This subject is probably a can of worms, I am only repeating what I was told.
If true it is of little consequence when the injector pulses are triggered,
they are going to fire at different parts of the cycle for various cylinders
in a V12 if not a sequential system.
Richard Dowling, Melbourne, Australia, '79 XJ-S & '85 XJ6.
Richard Dowling wrote:
He
mentioned that intuitively you expect the injector, mounted on top of
the inlet valve, should squirt fuel right into the cylinder as the
valve opens. Well, quite often that does not allow full atomisation
and mixing and the results are not good. He claims some sequential
injection systems squirt onto the back of a closed hot valve and get
better atomisation and hence better results.
If you have sequential injection, it might even be worth thinking
about exactly where in the cycle you want to inject. Perhaps the
intake valve is hotter during or after the combustion stroke than
during the compression stroke. Perhaps injecting too early can
result in good atomization followed by the fuel just condensing back
out on the walls of the intake manifold. Just thoughts. Ideally, I
guess, you’d want to be able to vary it, and trial-and-error to see
when injection works best.
Many years ago I was visiting a buddy who works in a race garage. He
was showing me the innards of a race car he was working on, and we
were noting the injectors. The latest fad at the time was to turn
the injectors around and aim them UPSTREAM in the inlet tract. So,
everyone had had to design or buy new intake manifolds for their race
cars. The theory, though, was apparently that it would atomize
better that way.
– Kirbert
I am chasing one of these for my 3.6 litre Lynx Eventer
3.6 litre DAC4452
Can anyone point me in the right direction.
Is there anything else required?
ie new fascia nael other electronics?
thanks terry
tmcgrath@bigpond.com