Tune up....iridium sparks

Archives of Posts to the NZ MX5 List back in 2005
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Okibi
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Posts: 94
Joined: Fri May 19, 2006 2:03 am

Tune up....iridium sparks

Post by Okibi » Fri Nov 11, 2005 11:33 am

I use iridiums, they work fantastically, don't know if I get any better
performance or economy but do all my own servicing so I can afford to spend
more on lubricants and parts.


Iridiums in Australia have dropped to about $18 AUD these days.


I'd defiantly change the fuel filter, if I didn't know what the previous
owner was like I'd also consider draining the fuel tank, some people buy
fuel from the dodgiest and cheapest service stations and they run their fuel
tanks to empty every time.


Once your tank is cleaned and you have whacked on a new fuel filter, I'd run
a bottle of injector cleaner through as well.


(Note (and legal disclaimer) : draining your fuel tank is dangerous please
use all possible safety precautions or if incapable; get a registered
mechanic to do it for you)


- Dave.
If you had access to a car like this, would you take it back right away? Neither would I.

DBM58
Keep calm, Forum Moderator here.
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Location: Auckland

Tune up....iridium sparks

Post by DBM58 » Fri Nov 11, 2005 11:54 am

I am sure that I read somewhere (after I had fitted irridium plugs) that there
is a technical reason why they cannot have any effect in an MX5 engine. Can
anyone confirm this?

Another word of caution - also learned after the event. There is a procedure
outlined in the Haynes manual for changing the fuel filter, and it includes
purging the line of fuel before the filter is disconnected. If you do not do
this and you are doing the change by lying under your car (safely jacked up
and held on axle stands) then the fuel remaining in the lines drains down your
arm, and it is very uncomfortable.


Thank you for your help

Best regards

David Moughtin
David

DBM58
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Tune up....iridium sparks

Post by DBM58 » Fri Nov 11, 2005 11:54 am

I am sure that I read somewhere (after I had fitted irridium plugs) that there
is a technical reason why they cannot have any effect in an MX5 engine. Can
anyone confirm this?

Another word of caution - also learned after the event. There is a procedure
outlined in the Haynes manual for changing the fuel filter, and it includes
purging the line of fuel before the filter is disconnected. If you do not do
this and you are doing the change by lying under your car (safely jacked up
and held on axle stands) then the fuel remaining in the lines drains down your
arm, and it is very uncomfortable.


Thank you for your help

Best regards

David Moughtin
David

Okibi
See my 5 and raise you.
See my 5 and raise you.
Posts: 94
Joined: Fri May 19, 2006 2:03 am

Tune up....iridium sparks

Post by Okibi » Fri Nov 11, 2005 9:15 pm

IIRC it's something about the wasted spark ignition setup running one
spark plug in each pair *backwards*, ie it's sparking not from the
small and pricey platinum/iridium centre electrode to the outside, but
the other way around.
But the outside of the spark plug is the ground, the whole engine is
grounded.

If it tried to fire "backwards" the engine becomes "live"

- Dave.
If you had access to a car like this, would you take it back right away? Neither would I.

Euen
I am quitting my job and going 5-ing
I am quitting my job and going 5-ing
Posts: 619
Joined: Tue May 23, 2006 9:42 am
Location: North Shore

Tune up....iridium sparks

Post by Euen » Fri Nov 11, 2005 9:45 pm

It sounds impossible if you apply traditional thinking but it works. It is achieved by using multiple isolated coils.

The spark is fired through one plug which is connected to the next plug through the head. The "earth" return is then via the plug lead on the second plug to the second coil. The electron flow is across the gap in the "correct" direction on one plug and in the "reverse" direction on the second plug.

Cheers
Euen
TG Sports, classic roadster - modern technology. NA1800, 99 head, 11:1 +2mm Wiseco pistons, Link LEM, Alloy f/wheel, JR headers.

Euen
I am quitting my job and going 5-ing
I am quitting my job and going 5-ing
Posts: 619
Joined: Tue May 23, 2006 9:42 am
Location: North Shore

Tune up....iridium sparks

Post by Euen » Fri Nov 11, 2005 9:45 pm

It sounds impossible if you apply traditional thinking but it works. It is achieved by using multiple isolated coils.

The spark is fired through one plug which is connected to the next plug through the head. The "earth" return is then via the plug lead on the second plug to the second coil. The electron flow is across the gap in the "correct" direction on one plug and in the "reverse" direction on the second plug.

Cheers
Euen
TG Sports, classic roadster - modern technology. NA1800, 99 head, 11:1 +2mm Wiseco pistons, Link LEM, Alloy f/wheel, JR headers.

EricW
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Location: Whangaparaoa

Tune up....iridium sparks

Post by EricW » Sun Nov 13, 2005 9:59 am

Hi Euen,

Ok, so I can understand how it works, what I can't see, is the advantage of
doing this, can you enlighten me?

Eric

EricW
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Tune up....iridium sparks

Post by EricW » Sun Nov 13, 2005 9:59 am

Hi Euen,

Ok, so I can understand how it works, what I can't see, is the advantage of
doing this, can you enlighten me?

Eric

Euen
I am quitting my job and going 5-ing
I am quitting my job and going 5-ing
Posts: 619
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Tune up....iridium sparks

Post by Euen » Sun Nov 13, 2005 4:35 pm

Hi Eric

For part of the reason I had to refer to Norman Garrett's Performance
Handbook where he says that the particular ignition system was chosen
because they did not have room at the back of the engiine for a conventional
distributor however I am sure there were other reasons for the choice of
"wasted spark".

I seem to recall reading somewhere else that the wasted spark also helps
with emission control by providing the second spark during the exhaust
stroke to provide secondary ignition of unburnt gases. Unfortunately I
can't remember the source but it may have been Miata.net.

Cheers
Euen
TG Sports, classic roadster - modern technology. NA1800, 99 head, 11:1 +2mm Wiseco pistons, Link LEM, Alloy f/wheel, JR headers.

Euen
I am quitting my job and going 5-ing
I am quitting my job and going 5-ing
Posts: 619
Joined: Tue May 23, 2006 9:42 am
Location: North Shore

Tune up....iridium sparks

Post by Euen » Sun Nov 13, 2005 4:35 pm

Hi Eric

For part of the reason I had to refer to Norman Garrett's Performance
Handbook where he says that the particular ignition system was chosen
because they did not have room at the back of the engiine for a conventional
distributor however I am sure there were other reasons for the choice of
"wasted spark".

I seem to recall reading somewhere else that the wasted spark also helps
with emission control by providing the second spark during the exhaust
stroke to provide secondary ignition of unburnt gases. Unfortunately I
can't remember the source but it may have been Miata.net.

Cheers
Euen
TG Sports, classic roadster - modern technology. NA1800, 99 head, 11:1 +2mm Wiseco pistons, Link LEM, Alloy f/wheel, JR headers.

EricW
See my 5 and raise you.
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Posts: 95
Joined: Wed May 24, 2006 7:07 pm
Location: Whangaparaoa

Tune up....iridium sparks

Post by EricW » Sun Nov 13, 2005 5:29 pm

Yes, now you mention it, I think I have heard the "emission control"
explanation before, but one would also think there would still be enough
heat in the exhaust gas to continue combustion for a short while after the
gas cleared the cylinder anyway.

Consider a jet afterburner, plenty of heat for combustion, but it only works
because they inject more fuel, there is not enough unburnt fuel otherwise.

The "lack of space" reason sounds more logical to me

Thanks

Eric

EricW
See my 5 and raise you.
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Posts: 95
Joined: Wed May 24, 2006 7:07 pm
Location: Whangaparaoa

Tune up....iridium sparks

Post by EricW » Sun Nov 13, 2005 5:29 pm

Yes, now you mention it, I think I have heard the "emission control"
explanation before, but one would also think there would still be enough
heat in the exhaust gas to continue combustion for a short while after the
gas cleared the cylinder anyway.

Consider a jet afterburner, plenty of heat for combustion, but it only works
because they inject more fuel, there is not enough unburnt fuel otherwise.

The "lack of space" reason sounds more logical to me

Thanks

Eric

zorruno
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Tune up....iridium sparks

Post by zorruno » Sun Nov 13, 2005 9:32 pm

Euen Burke wrote:
For part of the reason I had to refer to Norman Garrett's Performance
Handbook where he says that the particular ignition system was chosen
because they did not have room at the back of the engiine for a conventional
distributor however I am sure there were other reasons for the choice of
"wasted spark".

I seem to recall reading somewhere else that the wasted spark also helps
with emission control by providing the second spark during the exhaust
stroke to provide secondary ignition of unburnt gases. Unfortunately I
can't remember the source but it may have been Miata.net.
I'm sure it it as simple as only 1 dual coil pack needed (i.e. cost
saving). Slightly simpler for ECU and timing also. I doubt there is
any advantage at all in having a wasted spark system. Minimal
disadvantage however - apart from a small power loss with extra power
needed to charge coil pack...

cheers
H
(z)

zorruno
Black is the new black.
Black is the new black.
Posts: 601
Joined: Thu Apr 13, 2006 11:20 pm
Location: An Eastern Beach

Tune up....iridium sparks

Post by zorruno » Sun Nov 13, 2005 9:32 pm

Euen Burke wrote:
For part of the reason I had to refer to Norman Garrett's Performance
Handbook where he says that the particular ignition system was chosen
because they did not have room at the back of the engiine for a conventional
distributor however I am sure there were other reasons for the choice of
"wasted spark".

I seem to recall reading somewhere else that the wasted spark also helps
with emission control by providing the second spark during the exhaust
stroke to provide secondary ignition of unburnt gases. Unfortunately I
can't remember the source but it may have been Miata.net.
I'm sure it it as simple as only 1 dual coil pack needed (i.e. cost
saving). Slightly simpler for ECU and timing also. I doubt there is
any advantage at all in having a wasted spark system. Minimal
disadvantage however - apart from a small power loss with extra power
needed to charge coil pack...

cheers
H
(z)

poison
Keep calm, Forum Moderator here.
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Tune up....iridium sparks

Post by poison » Sun Nov 13, 2005 11:57 pm

I'm with zorruno on this one, many 2 cylinder, 2 stroke engines use this
method, one coil (in the case of a 2 cylinder) is less space and of course
less cost. You will also find that the fuel injectors fire two at a time,
not sure why this is though, probably cost, unlikely performance.

A 'backwards' firing plug like these iridium's may have a longer tip life
due to the direction of the arc, or possibly it's all just a gimmick to make
you spend many $$$$ to get 0.0001% increase in horsepower.

Gazza
"PO1SON"
:twisted: Gazda in the white HOT Mazda :twisted:

poison
Keep calm, Forum Moderator here.
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Posts: 530
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Tune up....iridium sparks

Post by poison » Sun Nov 13, 2005 11:57 pm

I'm with zorruno on this one, many 2 cylinder, 2 stroke engines use this
method, one coil (in the case of a 2 cylinder) is less space and of course
less cost. You will also find that the fuel injectors fire two at a time,
not sure why this is though, probably cost, unlikely performance.

A 'backwards' firing plug like these iridium's may have a longer tip life
due to the direction of the arc, or possibly it's all just a gimmick to make
you spend many $$$$ to get 0.0001% increase in horsepower.

Gazza
"PO1SON"
:twisted: Gazda in the white HOT Mazda :twisted:

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