iridium plugs
08-10-2004, 09:08 AM
#11
Does conductivity make much of a difference?
Are we not more interested in what happens between the gap? I'm not convinced that the conductivity of a small portion of this circuit (the plug, itself) makes a difference, especially when the important area (the gap) isn't terribly conductive
(under normal conditions), after all.
I'm sure that I'm wrong, however.
(under normal conditions), after all.
I'm sure that I'm wrong, however.
08-10-2004, 10:00 AM
#14
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Hmm, Bosch in Europe makes a Silver Plug! (and other stuff they don't have in the states) link.>
<center><img src="http://www.boschautoparts.co.uk/images/product/pcPlug/pcPlug1.jpg"></center><p>"In racing, Silver is always the winner.
These plugs were designed to deliver critical requirements and handle the extreme pressures that exist today in high performance motor sports.
Not only do these plugs protect against misfires, but they ignite more easily, giving peak power output for motorcycles, speedboats and sports cars."
Interesting... I know they have different Platium plugs in Europe, the Platin plugs is different than th Bosch American Plugs, but I didn't know they have whole line of plugs that aren't sold here at all like Yttrium, unless that is iridium... Don't think it's the same??? Anyone know more?<ul><li><a href="http://www.boschautoparts.co.uk/pcPlug5.asp?c=2&d=1">http://www.boschautoparts.co.uk/pcPlug5.asp?c=2&d=1</a</li></ul>
These plugs were designed to deliver critical requirements and handle the extreme pressures that exist today in high performance motor sports.
Not only do these plugs protect against misfires, but they ignite more easily, giving peak power output for motorcycles, speedboats and sports cars."
Interesting... I know they have different Platium plugs in Europe, the Platin plugs is different than th Bosch American Plugs, but I didn't know they have whole line of plugs that aren't sold here at all like Yttrium, unless that is iridium... Don't think it's the same??? Anyone know more?<ul><li><a href="http://www.boschautoparts.co.uk/pcPlug5.asp?c=2&d=1">http://www.boschautoparts.co.uk/pcPlug5.asp?c=2&d=1</a</li></ul>
08-10-2004, 06:19 PM
#18
AudiWorld Senior Member
Here's latest from Road & Track on plugs:
Sep 04 issue, Tech Correspondence, answering a question about validity of platinum plugs:
"Given today's arc welder ignitions, getting a sparkplug to fire is not such a struggle as you've demonstrated. But sparking a suitably large flame kernel, and keeping it lit, in today's often dynamic, high pressure and lean cylinders is still a good trick. So, yes, sparkplug electrode material does not play a direct role in spark intensity. However, platinum and iridium electrodes can be much smaller, notably reducing misfiring becasue they result in more robust flame kernels. This is because the smaller electrodes are less of a shroud, exposing more mixture to the flame front.
An unusually dramatic illustration of this is with aftermarket supercharged engines running high boost. Such engines often falter terribly at high boost and high rpm due to ignition failure. Simply screwing in iridium-tipped sparkplugs typically eliminates the misfiring and allows the engine to rev to its power peak. In practice, this means a simple plug change is worth 30 bhp simply because the new plugs allow the engine to reach its designed redline."
so---it's not the conductivity of the base material, it's the mechanics of the spark/flame front that makes the difference. Sounds logical to me... Esp in the high pressures of our compression ratio and boost.
Fig
"Given today's arc welder ignitions, getting a sparkplug to fire is not such a struggle as you've demonstrated. But sparking a suitably large flame kernel, and keeping it lit, in today's often dynamic, high pressure and lean cylinders is still a good trick. So, yes, sparkplug electrode material does not play a direct role in spark intensity. However, platinum and iridium electrodes can be much smaller, notably reducing misfiring becasue they result in more robust flame kernels. This is because the smaller electrodes are less of a shroud, exposing more mixture to the flame front.
An unusually dramatic illustration of this is with aftermarket supercharged engines running high boost. Such engines often falter terribly at high boost and high rpm due to ignition failure. Simply screwing in iridium-tipped sparkplugs typically eliminates the misfiring and allows the engine to rev to its power peak. In practice, this means a simple plug change is worth 30 bhp simply because the new plugs allow the engine to reach its designed redline."
so---it's not the conductivity of the base material, it's the mechanics of the spark/flame front that makes the difference. Sounds logical to me... Esp in the high pressures of our compression ratio and boost.
Fig
08-10-2004, 07:31 PM
#19
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IK22 iridium plugs are excellent for Stage 1, and Stage 2 but..
The BMEP and effective cylinder pressures in a modified TT are higher relative to stock pressure. The higher pressure places a higher load on the ignition system, in that a higher voltage is required to jump the stock gap in modified TTs. This results in an increase in failed coilpacks for those who have an over-gapped or degraded plug/s. While a slight reduction in gap to account for higher cylinder pressures and colder plugs to reduce detonation are warranted for modified TTs, the relative merits of plug choice are very specific to the mod level. I would not recommend a gap change unless you have a tuner dyno 'plug' the car.
I have direct experience of misfires as a result of coilpack degradation. Coilpack degradation can be accelerated and associated with unsuitable, over-gapped or degraded plug/s. Coilpack failures related to the defective coilpacks are more even more immediate with over-gapped or degraded plug/s. Use a vagcom to look for misfire counts, and if you have misfires, look at plugs, gap and coilpacks.
Here is what I've learned:
Coilpacks can be degraded and the car will still run...but in high states of tune they will fail faster. Get a vagcom if your TT is modified and watch your misfire counts on each cylinder. If the misfire counts are there take out the coilpack and look at the plugs for signs of detonation, as well as look at the paint if it is flaking off of the nose of the coilpack versus the others. Some flaking is normal, but a lot of flaking is a sure sign of coilpack overloading because of unsuitability of plug or gap.
Stock
Denso IK20s (stock)
Stage 1 & 2:
IK22s (stage 2/93 octane or stage 1/91 octane) are an excellent plug provided that the gap is checked to be no larger than stock and after install you do a vagcom to check for misfires.
Stage 3:
It is likely that a stage 3 TT will need a plug change from IK22s. The rationale for switching from IK22 is related to the additional voltage loading related to the high pressures in combination with higher resistance of iridium electrode in IK22s and increase risk of detonation induced by the smaller electrodes. While iridium has a higher melting point versus platinum or copper the finer electrode has been associated with detonation in some setups as higher melting point does not always translate to cooler as platinum and iridium have poorer thermal conductivity. Many cars may do just fine with IK22s and stage 3 mods...you need to 'dyno plug' the car to several plugs and find out what works best.
... This is consistent with recommendations given in Graham Bell's excellent book: "Forced Induction Performance Tuning", on pg. 313. Only the tuner should recommend Stage 3 plugs as the effects of detonation are accelerated in high states of boost. A vagcom, as well as a 4w dyno, are the best tools to check for plug suitability.
ALSO...if the TT is nitrous modded...DO not use platinum, palladium or yttrium plugs as these rare earth metals accelerate detonation.
...for those stage 3 cars in California the use of street legal 100 octane is warranted...the only gasoline that HAS NOT GONE UP IN PRICE in the last three years!!! ($4.19-4.39) Go figure...
I have direct experience of misfires as a result of coilpack degradation. Coilpack degradation can be accelerated and associated with unsuitable, over-gapped or degraded plug/s. Coilpack failures related to the defective coilpacks are more even more immediate with over-gapped or degraded plug/s. Use a vagcom to look for misfire counts, and if you have misfires, look at plugs, gap and coilpacks.
Here is what I've learned:
Coilpacks can be degraded and the car will still run...but in high states of tune they will fail faster. Get a vagcom if your TT is modified and watch your misfire counts on each cylinder. If the misfire counts are there take out the coilpack and look at the plugs for signs of detonation, as well as look at the paint if it is flaking off of the nose of the coilpack versus the others. Some flaking is normal, but a lot of flaking is a sure sign of coilpack overloading because of unsuitability of plug or gap.
Stock
Denso IK20s (stock)
Stage 1 & 2:
IK22s (stage 2/93 octane or stage 1/91 octane) are an excellent plug provided that the gap is checked to be no larger than stock and after install you do a vagcom to check for misfires.
Stage 3:
It is likely that a stage 3 TT will need a plug change from IK22s. The rationale for switching from IK22 is related to the additional voltage loading related to the high pressures in combination with higher resistance of iridium electrode in IK22s and increase risk of detonation induced by the smaller electrodes. While iridium has a higher melting point versus platinum or copper the finer electrode has been associated with detonation in some setups as higher melting point does not always translate to cooler as platinum and iridium have poorer thermal conductivity. Many cars may do just fine with IK22s and stage 3 mods...you need to 'dyno plug' the car to several plugs and find out what works best.
... This is consistent with recommendations given in Graham Bell's excellent book: "Forced Induction Performance Tuning", on pg. 313. Only the tuner should recommend Stage 3 plugs as the effects of detonation are accelerated in high states of boost. A vagcom, as well as a 4w dyno, are the best tools to check for plug suitability.
ALSO...if the TT is nitrous modded...DO not use platinum, palladium or yttrium plugs as these rare earth metals accelerate detonation.
...for those stage 3 cars in California the use of street legal 100 octane is warranted...the only gasoline that HAS NOT GONE UP IN PRICE in the last three years!!! ($4.19-4.39) Go figure...