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Spark Plugs


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In the past there has been discussion of what plug to use and some concerns were mentioned about the Bosch Platinum +4 (part number 4417). I ran these in my car (1998 Boxster) for the last 30K miles after having run the stock Beru plugs for the first 30K miles. I have attached pictures of both plugs. I did not have any problems with the Bosch plugs. They appear pretty much what I would expect them to look like after 30K miles. YMMV.

post-676-1125769882_thumb.jpg

post-676-1125769899_thumb.jpg

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Does not the 7 in 4417 mean heat range 7?  The Bosch site lists the 4417 and the FR7LDC4 (the stock plug) as equivalent.

The 7 in 4417 does not represent the heat range. The Bosch Platinum +2 that's called out for the Boxster is #4303, but the last 3 is not for the heat range. The 4417 fits as far as size goes, but it's not the same plug as or equal to the OEM FR7LDC4. The OEM FR7LDC4 plugs are copper, not platinum. The 4 digit numbered plugs are just an easy lookup number for the end user at an auto shop for the plugs sold retail and have no real meaning.

The FR7LDC4 means:

F=Seat (16mm), Threads (M14x1.25)

R=Version (With suppression resistor)

7=Heat range (7)

L=Thread lenghth (19mm) spark position (5mm)

D=Electrode version (2 electrodes)

C=Electrode material (Copper)

4=Version (Extended insulator nose)

I've had the same comments as MNBoxster's on the Boxster and on the 928 so that's why I'll be sticking with OEM type plugs and no longer try other plugs.....just in case.

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Hi,

A few pointers about sparkplugs:

The advantage of using a Platinum Plug isn't one of Performance, they add nothing, zero, nada over the OEM plugs.

The advantage of using Platinum Plugs is that the electrode tip can withstand higher heat and so last longer and the Service Interval is increased.

A spark plug's Heat Range has no relationship on the actual voltage transferred through the spark plug. Rather, the Heat Range is a measure of the spark plug's ability to remove heat from the combustion chamber. The heat range measurement is determined by several factors:

The length of the ceramic center insulator nose

The insulator nose's ability to absorb and transfer combustion heat

The material composition of the insulator

The material composition of the center electrode

The longer the insulator nose, a larger surface area is exposed to combustion gasses and heat is dissipated slowly. This also means the firing end heats up more quickly. That is, the exposed ceramic length, not extended tip length.

The insulator nose length is the distance from the firing tip of the insulator to the point where the insulator meets the metal shell. Since the insulator tip is the hottest part of the spark plug, the tip temperature is a primary factor in pre-ignition and fouling. No matter what the plugs are installed in, be it a lawnmower, a boat, your daily driver or your race car, the spark plug tip temperature must remain between 450°C to 850°C. If the tip temperature is lower than 450°C, the insulator area surrounding the center electrode will not be hot enough to deter fouling and carbon deposit build-ups, causing misfires. If the tip temperature exceeds 850°C, the spark plug will overheat which can cause the ceramic around the the center electrode to blister as well as the electrodes will begin to melt. This may lead to pre-ignition/detonation and expensive engine damage.

In identical spark plugs, the differences from one heat range to the next is the ability to remove approximately 70°C to 100°C from the combustion chamber.

The firing end appearance also depends on the spark plug tip temperature. There are three basic diagnostic criteria for spark plugs: good, fouled, and overheated. The borderline between the fouling and optimum operating regions (450°C) is called the spark plug self-cleaning temperature. This is the temperature point where the accumulated carbon and combustion deposits are burned off automatically.

Bearing in mind that the insulator nose length is a determining factor in the heat range of a spark plug, the longer the insulator nose, the less heat is absorbed, and the further the heat must travel into the cylinder head water journals and to the ambient engine compartment air. This means that the plug has a higher internal temperature, and is said to be a "Hot" plug. A hot spark plug maintains a higher internal operating temperature to burn off oil and carbon deposits, and has no relationship to spark quality, intensity, or performance.

Conversely, a "Cold" spark plug has a shorter insulator nose and absorbs more combustion chamber heat. This heat travels a shorter distance, and allows the plug to operate at a lower internal temperature. A colder heat range can be necessary when an engine is modified for performance, subjected to heavy loads, or it is run at high RPMs for significant periods of time. The higher cylinder pressures developed by high compression, large camshafts, blowers and nitrous oxide, not to mention the RPM ranges we run our engines at while racing, make colder plugs mandatory to eliminate plug overheating and engine damage. The colder type plug removes heat more quickly, and will reduce the chance of pre-ignition/detonation and burn-out of the firing end. (Engine temperatures can affect the spark plug's operating temperature, but not the spark plug's heat range).

But, back on point, considering that changing the sparkplugs is possibly the cheapest, and one of the easiest maintenance tasks you can do to a car, why would you want to keep the same plugs for 50k miles? For only $10-$20 you can change the plugs regularly to insure everything is in top tune. If on the other hand, you increase the Service Interval, a failed plug can go unoticed (due to a cracked Insulator or broken electrode, etc.) for tens of thousands of miles!

I change the plugs on all my Fun cars annually at the start of the season. This means they are replaced at about 5k mi. It's easy and cheap, why not be sure they're always in Top Form!

Happy Motoring!...Jim'99

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      But, back on point, considering that changing the sparkplugs is possibly the cheapest, and one of the easiest maintenance tasks you can do to a car, why would you want to keep the same plugs for 50k miles? For only $10-$20 you can change the plugs regularly to insure everything is in top tune.  If on the other hand, you increase the Service Interval, a failed plug can go unoticed (due to a cracked Insulator or broken electrode, etc.) for tens of thousands of miles!

I change the plugs on all my Fun cars annually at the start of the season. This means they are replaced at about 5k mi. It's easy and cheap, why not be sure they're always in Top Form!

Happy Motoring!...Jim'99

I do not know where you get your plugs but they are $6-$10 each from the dealer. Not that I am advocating an extended service interval but every 5K miles seems wasteful. If the failed plug is "unnoticed" i.e. you cannot detect any change in performance then why would a new plug make any difference?

My original intent for this thread was to "refute" the less than favorable press about the 4417s. I appear to have gotten 30K miles out of them without anything falling off of them or any other ill effects. YMMV

If the 7 does not indicate the heat range what is the heat range for the 4417 and 4403? I cannot find that info on the Bosch website and the plug only has 4417 stamped on it. As Bosch recommends these plugs along with the FR7LDC4 it seems logical to me that they are also heat range 7. It would be nice if someone could reference a source of more definitive information.

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I do not know where you get your plugs but they are $6-$10 each from the dealer. 

      I don't know why anybody would buy something as mundane and universally available from a Dealer and pay their markup. I just bought a set for @$2.

Not that I am advocating an extended service interval but every 5K miles seems wasteful.

      Of course the 5k mi. change interval may be considered wasteful (that's subjective). I change them annually, it's most convenient for me at the start of the season (I live in Mpls. and the cars are run only 5-6 mos./yr.).  Winter can be especially demanding on a sparkplug which has to repeatedly withstand temperature swings of as much as from say 0°F - 850°F. In my view, going 30k mi. on a set of plugs may be as bad or worse.

From the FAQ at Bosch USA site: As a rule, Bosch recommends that you follow the replacement interval listed in your vehicle owners manual, however we highly recommend that you inspect (read) your spark plugs annually and replace as required, to insure optimum engine performance.

If the failed plug is "unnoticed" i.e. you cannot detect any change in performance then why would a new plug make any difference?

      You cannot be serious. The damage caused by non-combusted fuel to the O² Sensors and Catalytic Converter is Progressive and can take some time to manifest itself.  Also, given the rising cost of fuel today it doesn't take long to recover the cost of 6 sparkplugs.

     

My original intent for this thread was to "refute" the less than favorable press about the 4417s.  I appear to have gotten 30K miles out of them without anything falling off of them or any other ill effects.  YMMV

      Again, that you know of.  But, as I said, the plugs (Bosche) did not have the proper color for a correct 14:1 Air/Fuel ratio (this is a very static indicator and doesn't change one plug for the other, or one engine for the other for that matter). You claim to have experienced some trouble codes - cause and effect?

If the 7 does not indicate the heat range what is the heat range for the 4417 and 4403?  I cannot find that info on the Bosch website and the plug only has 4417 stamped on it.  As Bosch recommends these plugs along with the FR7LDC4 it seems logical to me that they are also heat range 7.  It would be nice if someone could reference a source of more definitive information.

I have included the Bosch designation code(s), but the Platinum +4 and +2 don't follow these guides, as you mention. I have sent an email to their Technical Dept. and will report back on their reply. See attached.

Happy Motoring!...Jim'99

post-6437-1126103545_thumb.jpg

Edited by MNBoxster
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I do not know where you get your plugs but they are $6-$10 each from the dealer. 

      I don't know why anybody would buy something as mundane and universally available from a Dealer and pay their markup. I just bought a set for @$2.

--------------

In California I have not been able to find the plug at any retail outlet (Napa, Kragen).  Napa does not list it as available.  Kragen say they might be able to order it and the price is $7.50 each.  What is the name of the store that you buy them at (FR7LDC4) and what is their telephone number so that I can order a bunch at $2 each?

--------------

Not that I am advocating an extended service interval but every 5K miles seems wasteful.

      Of course the 5k mi. change interval may be considered wasteful (that's subjective). I change them annually, it's most convenient for me at the start of the season (I live in Mpls. and the cars are run only 5-6 mos./yr.).  Winter can be especially demanding on a sparkplug which has to repeatedly withstand temperature swings of as much as from say 0°F - 850°F. In my view, going 30k mi. on a set of plugs may be as bad or worse.

-----------------

You cannot tell me that the temp swing from 0-850 F is any worse for the plug than 40-850 F that we have here in California.  Also plugs do not run at 850 F, they run somewhere between 500-900 degrees Celsius according to the Bosch website.  Other things like lack of fuel vaporization when cold may make life harder for the plug on startup but once operating temperature is achieved colder outdoor temps should not make any difference to the spark plug.

-----------------

From the FAQ at Bosch USA site: As a rule, Bosch recommends that you follow the replacement interval listed in your vehicle owners manual, however we highly recommend that you inspect (read) your spark plugs annually and replace as required, to insure optimum engine performance.

If the failed plug is "unnoticed" i.e. you cannot detect any change in performance then why would a new plug make any difference?

      You cannot be serious. The damage caused by non-combusted fuel to the O² Sensors and Catalytic Converter is Progressive and can take some time to manifest itself.  Also, given the rising cost of fuel today it doesn't take long to recover the cost of 6 sparkplugs.

     

--------------------

You cannot be serious.  If that much non-combusted fuel were making it out the exhaust with today's emission controls you would throw a CEL faster than you could stop the car.

--------------------

My original intent for this thread was to "refute" the less than favorable press about the 4417s.  I appear to have gotten 30K miles out of them without anything falling off of them or any other ill effects.  YMMV

      Again, that you know of.  But, as I said, the plugs (Bosche) did not have the proper color for a correct 14:1 Air/Fuel ratio (this is a very static indicator and doesn't change one plug for the other, or one engine for the other for that matter). You claim to have experienced some trouble codes - cause and effect?

------------------------

1) The trouble code was caused by a bad MAF.  It is hard to conceive how a "bad" spark plug could cause the MAF to deteriorate. 2) After the MAF was replaced the CEL was gone and engine operating parameters returned to normal.  So after 30K miles there does not appear to be any problems caused by the 4417 plugs.

------------------------

If the 7 does not indicate the heat range what is the heat range for the 4417 and 4403?  I cannot find that info on the Bosch website and the plug only has 4417 stamped on it.  As Bosch recommends these plugs along with the FR7LDC4 it seems logical to me that they are also heat range 7.  It would be nice if someone could reference a source of more definitive information.

I have included the Bosch designation code(s), but the Platinum +4 and +2 don't follow these guides, as you mention. I have sent an email to their Technical Dept. and will report back on their reply. See attached.

-------------------------

From the Bosch website:

A. To ensure optimal performance in your car, Bosch has tested each vehicle model and the various engines available for that model listed in the Spark Plug catalog or our web-page. Using a special spark plug with a thermocouple built in, Bosch engineers find the hottest cylinder in an engine and then test various spark plugs in that cylinder until the ideal plug is found. This ensures that you will always get the best performance possible.

Taken at its face value it would seem that the 4403 and 4417 plugs have been tested and found to be the correct plugs i.e. the correct heat range.

---------------------------

Happy Motoring!...Jim'99

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Hi,

Not to start Flame Wars, but we can go on Point-Counterpoint all day.

The fact is you have made a claim that using the 4417 plugs for 30k mi. had no ill effects.

I stated that the plugs do not have the correct color for proper combustion, an ill effect in my book.

Granted a sparkplug is a Snapshot in time, but this is the picture you have. Does the CEL issue explain it away? Plugs take on the effect of the A/F mixture near instantaneously and will change as the conditions do. If the CEL issue was corrected, this should be immediately seen in the plugs (within 5-10 miles).

All I know from the pic is that they are running Hot, perhaps due to a lean condition, perhaps due to improper Heat Range, or both. Plugs have basically 3 classifications: Good, Fouled (Cool), or Hot . Neither you nor I can say that the plugs weren't that way all along.

Also, I am somewhat disconcerted that Porsche specifies a Heat Range for the various Models, Markets, Engines, etc., but Bosch seems to spec this plug to run the whole gamut, including many other engines and makes. I don't agree with letting the plugs go 30k mi., but that is debatable.

So far as my source for the plugs, I'll dig out my receipt and forward the info to you offline. I think it was at Pep Boys.

Happy Motoring!...Jim'99

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Hi,

      Not to start Flame Wars, but we can go on Point-Counterpoint all day.

      The fact is you have made a claim that using the 4417 plugs for 30k mi. had no ill effects.

      I stated that the plugs do not have the correct color for proper combustion, an ill effect in my book.

      Granted a sparkplug is a Snapshot in time, but this is the picture you have. Does the CEL issue explain it away? Plugs take on the effect of the A/F mixture near instantaneously and will change as the conditions do. If the CEL issue was corrected, this should be immediately seen in the plugs (within 5-10 miles). 

      All I know from the pic is that they are running Hot, perhaps due to a lean condition, perhaps due to improper Heat Range, or both.  Plugs have basically 3 classifications: Good, Fouled (Cool), or Hot . Neither you nor I can say that the plugs weren't that way all along.

------------------------

As I stated in an earlier post the car was running lean when the plugs were taken out and before the MAF was replaced.  Now that the MAF is fixed I suppose I can put the 4417s back in to see if the color changes.

------------------------

      Also, I am somewhat disconcerted that Porsche specifies a Heat Range for the various Models, Markets, Engines, etc., but Bosch seems to spec this plug to run the whole gamut, including many other engines and makes. I don't agree with letting the plugs go 30k mi., but that is debatable.

---------------------------

Then you must really disagree with the current plug change interval of 60K miles.

---------------------------

      So far as my source for the plugs, I'll dig out my receipt and forward the info to you offline. I think it was at Pep Boys.

-------------------------

Called Pep Boys.  They do not carry the FR7LDC4 either.

-------------------------

Happy Motoring!...Jim'99

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