[v12-engine] Emission classes

Hello!

Does anyone know what the differences between emission
classes regarding the V12 engine did mean?

As I understand the 5.3 A and 5.3 C were for the low
emission US, Canadian and Japanese market and the 5.3 B was
for the UK market. But then there were 5.3 D, 5.3 E and 5.3
F, as well.

What were the specifications for these last three emission
classes? Were they the same as 5.3 B?

Best regards
Per-Johan–
pengie1
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Does anyone know what the differences between emission
classes regarding the V12 engine did mean?

As I understand the 5.3 A and 5.3 C were for the low
emission US, Canadian and Japanese market and the 5.3 B was
for the UK market. But then there were 5.3 D, 5.3 E and 5.3
F, as well.

I’ve found the Haynes manual, believe it or not, was better in this
regard up through the 1985 models when the book was copyrighted. In
the “Supplement” in the back of the book, page 349, there’s a
paragraph titled “Emission system identification”. It lists:

A North America
B UK, Europe
C Japan
D Australia.

Vacuum diagrams are provided for these four classes. The Australian
model is the only one with a vacuum retard.

Of interest: there are two diagrams for North American models, pre
1983 and post 1983. My car was a 1983 and was fitted with the post
scheme. The difference between those two is that the post 1983 has a
vacuum regulator while the pre 1983 does not. Based on this, one
would conclude that both schemes are called “A”.

I presume E and F came after 1985, hence not covered in the Haynes.

– Kirbert

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !On 5 Oct 2014 at 13:13, pengie1 wrote:

In reply to a message from Kirbert sent Mon 6 Oct 2014:

Thank you very much for the answer, Kirbert. You are a true
expert.

For me not being an expert on hardly anything, what does
vacuum retard mean? Does it have an effect on the 217kW?–
The original message included these comments:

I’ve found the Haynes manual, believe it or not, was better in this
regard up through the 1985 models when the book was copyrighted. In
D Australia.
I presume E and F came after 1985, hence not covered in the Haynes.
– Kirbert


pengie1
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For me not being an expert on hardly anything, what does
vacuum retard mean?

It means there’s a vacuum connection to the vac capsule that, when
vacuum is applied, will retard the timing. To be clear, the ones in
the Aussie-spec XJ-S also have vacuum advance in the same capsule.

Optimum ignition timing is readily determined in a test stand,
running various speeds and loads and dialling the timing around to
see what works best. Building a distributor that faithfully follows
that optimum is a challenge, though, and emission requirements just
make the job that much harder. Roger Bywater wrote up a description
of how vacuum retard can be used to allow an optimum advance curve
and then only retard that timing when necessary, and it makes perfect
sense – but owners still don’t like the idea of retarding the timing
and often disable the thing.

Does it have an effect on the 217kW?

Not when it’s working correctly. IIRC, it only retards the timing at
idle, but it’s been a while since I read up on it.

– Kirbert

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !On 6 Oct 2014 at 12:38, pengie1 wrote:

In reply to a message from Kirbert sent Mon 6 Oct 2014:

At idle AND under a certain temp IIRC. So if the engine is
already very hot it won’t retard and make things hotter.
That was on my carbed E-type 5.3 anyhow. Didn’t think they
ever had vac retard on injection V12s.–
The original message included these comments:

Not when it’s working correctly. IIRC, it only retards the timing at
idle, but it’s been a while since I read up on it.


1E75339 66 D, 1R27190 70 FHC, 79 S2 XJ12L
Gaithersburg, Maryland, United States
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In reply to a message from PeterCrespin sent Tue 7 Oct 2014:

Great,thank you for the answers.

Best
Per-Johan
XJS-86–
pengie1
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