Another spark plug thread

[dsiegel360]

I'm running a 3.4, EFI, twin plug, turbonetics, 1 bar- 1.3 bar adjustable, etc. My first gear is now taller, which sucks when stopped on a hill at a light. My wrench used a Bosch F2CS plug that proved fine on the track but the plugs fouled on the street.

Are there plugs designed specifically for turbo cars? Plugs that are hot off boost and cold on boost?

The mods allow me an 8000-8500 rpm redline, and at 1.3 bar boost (which I usually leave at 1 bar), the plugs need to have a broader range of purpose to not then foul below 3000 rpm. Sometimes I drive the car without hitting boost at all. I need a plug that will handle 600+ hp and stay clean while lumping around between stop lights.

Which plugs solve this problem? At what gaps?

Thanks guys.

[DonE]

Once you modify these motors like you have, you really need to experiment. I ended up with NGK BR9ES gapped at .025 and might be an interesting place to start. They are regular plugs - nothing fancy and cost about $1.90 each.

[dsiegel360]

Originally Posted by DonE

Once you modify these motors like you have, you really need to experiment. I ended up with NGK BR9ES gapped at .025 and might be an interesting place to start. They are regular plugs - nothing fancy and cost about $1.90 each.

Thanks. I was told that the Bosch F2CS is equal to an NGK 9. I'm guessing that a tall 1st gear creates a slightly more complicated challenge in traffic. The F2CS was gapped at .025. Do you think i should try a BR8ES? .025? Or a different gap for the NGK 9?

How does gap size affect combustion?

Do any of you guys switch up plugs for track days?

[GJF]

If the gap is too big the boost will blow out the spark. You aren't providing enough info to be able to further the diag. You say you are reving to 8500??? Your spec say SC cams? What are your AFR's at idle and low speeds and what are they on boost? Your motor should run just fine on 8's or even 9's on the right tune depending on ambient. When the motor is tuned right there is no need to change plugs for the track. Just pull them to see how the motor is running from time to time. The goal on a modified motor or any motor for the point is to find the plug that stays the most consistant temperature throughout the the whole range the combustion chamber see's.

[spuggy]

Originally Posted by dsiegel360

Are there plugs designed specifically for turbo cars? Plugs that are hot off boost and cold on boost?

Nope.

The upside of a cold plug is sharper throttle response, and not melting in the combustion chamber. The downside is that a plug that is too cold will foul quickly.

A hot plug won't foul, but throttle response won't be as "sharp", and they may overheat/glow/pre-ignite/melt in prolonged WOT use.

The factory selected the original Bosch plug for the homologation run, expecting most of the initial 500(?) run of cars to have the snot driven out of them on the track. And not expecting to build any more cars.

These went through the EPA emissions testing, and were not changed (which would have required a re-certification) until the 964 Turbo 2 was introduced - when they went about 4 grades hotter, IIRC.

Stock 930 equipment are some very, very, cold plugs. However, they don't foul on the street either, thanks to the use of platinum.

They're not platinum plated, the tip is made from platinum wire. And thus the reason many people use something else; the downside is the $15 a pop price.

I've not had one foul yet, my car sees plenty of street driving.

[dsiegel360]

Originally Posted by spuggy

Stock 930 equipment are some very, very, cold plugs. However, they don't foul on the street either, thanks to the use of platinum.

They're not platinum plated, the tip is made from platinum wire. And thus the reason many people use something else; the downside is the $15 a pop price.

I've not had one foul yet, my car sees plenty of street driving.

$15 bucks. Ouch!!! Will Iridium achieve similar results to Platinum?
Do you use the stock Bosch 3's?

[dsiegel360]

[QUOTE=GJF;4194042]You aren't providing enough info to be able to further the diag. What are your AFR's at idle and low speeds and what are they on boost?




The AFR's were fine...until plugs fouled. AFR at idle and low speeds were 13.7-14.7. Boost- 11.8-12.5. Perhaps traffic, a tall 1st gear, and lastly... a sticky parking brake made for a perfect mess.

I would have thought that a warmer plug would give better throttle response. Spuggy informed me otherwise. In cold weather, which is better, a warmer plug or colder plug?

[spuggy]

Originally Posted by dsiegel360

$15 bucks. Ouch!!! Will Iridium achieve similar results to Platinum?

According to the marketing folks, yes they will. If they're as good as they say, why are they so cheap?

But this guy says they work:

http://www.automedia.com/Iridium_Spark_Plugs/pht20010101ds/1

Oddly enough, I did find a patent for a multi-range spark plug:

http://www.freepatentsonline.com/3743877.html

I also found this to be of interest:

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

From http://www.minimania.com/web/DisplayID/1788/SCatagory/ELECTRICAL/DisplayType/Technical%20Information/ArticleV.cfm

Do you use the stock Bosch 3's?

Yup, stock equipment W3DPO's. I heard some folks save them for track work, but I've never had one foul.

[quote]I would have thought that a warmer plug would give better throttle response. Spuggy informed me otherwise. In cold weather, which is better, a warmer plug or colder plug?[/quote[

Actually, it's more accurate to say that you get the best performance with the correct plug... Go too cold and they foul.

You shouldn't have to switch plugs to account for the weather.

[jly535]

I have W5DPOs installed by Squire in my nonintercooled 77 930,no running issues in cold, but then again they were installed befor I bought car so I have nothing to compare to. I would think the 3s were exactly that, homologated plugs for racing environment, so I think it makes sense to go a bit hotter if not tracking. I will try 3s sometime to do a side by side comparison, but I hate to spend money on two sets of plugs. Any other feedback on this??? Jamie

[spuggy]

Originally Posted by jly535

I have W5DPOs installed by Squire in my nonintercooled 77 930,no running issues in cold, but then again they were installed befor I bought car so I have nothing to compare to. I would think the 3s were exactly that, homologated plugs for racing environment, so I think it makes sense to go a bit hotter if not tracking. I will try 3s sometime to do a side by side comparison, but I hate to spend money on two sets of plugs. Any other feedback on this??? Jamie

Non-intercooled? And a 3DLZ? I think if I were you, I'd be looking at this again:

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

Your intake charge temperature has to be well over 100 degrees hotter than mine (based on Kokeln's chart), and you're running plugs 2 heat ranges hotter to boot.

You wanna borrow a set of used 3's?

[jly535]

Originally Posted by spuggy

Non-intercooled? And a 3DLZ? I think if I were you, I'd be looking at this again:



Your intake charge temperature has to be well over 100 degrees hotter than mine (based on Kokeln's chart), and you're running plugs 2 heat ranges hotter to boot.

You wanna borrow a set of used 3's?

I am running a 7006 currently, soon to be 7200. I may take you up on borrowing the 3s to see the differnence. I haven't read much good feedback about the hotter plugs, but I just trust Squire knows what he is doing. I haven't had any pinging or running issues, and I drive pretty conservative.

[GJF]

In cold weather the hotter plug would be advised. That is nother question I had for you. When ambient drops drastically then the plugs will need to be changed to compensate. I'd try a NGK BPR8ES, they are only $1.50. I would hate to experiment with $15.00 plugs. There is nothing wrong with sticking to copper plugs either. Platinum was the in thing years ago but is being replaced by iridium. All NGK platinum plugs are now superseded to iridium plugs as iridiums is a better conductor than platinum. at the power you state I would think 7's would be too hot but then again how cool is it where you are?

[dsiegel360]

Got the NGK iridium 9's. Gapped at .026. Plugs are still getting dirty. Crap!

http://farm3.static.flickr.com/2340/2888361053_8c1e0a10ca_s.jpg

[dsiegel360]

[lucittm]

A NGK "9" is a very cold plug. Your photo was a little blurry. I could not tell if the black color on the insulator was "fluffy" or "matte" or "shiny".

If all your plugs look the same (I bet they do), I would go down two heat ranges to a "7" and try that.

In order to get a really good plug reading, some mechanics specify that you run your car at the desired RPM (maybe max HP or onset of boost, for example). Hold that RPM for 60 seconds. Then cut the ignition and depress the clutch at the same time WITHOUT changing the position of the throttle. This reduces vacuum-induced deposits.

Good Luck,
Mark

[iamchappy]

I've been using NGK BKR6Ek's for the street with good results. This is the plug Supertec recommended to me.
I assume that you would run a colder one for the track.

[dsiegel360]

Originally Posted by GJF

In cold weather the hotter plug would be advised. That is nother question I had for you. When ambient drops drastically then the plugs will need to be changed to compensate. I'd try a NGK BPR8ES, they are only $1.50. I would hate to experiment with $15.00 plugs. There is nothing wrong with sticking to copper plugs either. Platinum was the in thing years ago but is being replaced by iridium. All NGK platinum plugs are now superseded to iridium plugs as iridiums is a better conductor than platinum. at the power you state I would think 7's would be too hot but then again how cool is it where you are?

I just moved to Indiana from NY. It'll be about the same ass-biting cold during the winter. I'm living in Indianapolis where there are lots of stoplights but I'll often be south of here on the twisties of Brown county. Come spring, I'll hope to be frequenting the track. If possible, I need plugs that can withstand traffic and the racetrack.

Will spirited driving clean a sooty plug (if the plug is a hot enough heat range on boost?)


Spuggy, thanks for the links. Interesting patent. When you say that your W3's haven't fouled, does this mean that harder driving keeps them clean, or that traffic doesn't get them dirty...or both?

[lucittm]

Plugs work with engine temperature, not ambient temperature. The insulator and firing tip need to get hot enough (500 - 800 degrees Centigrade) to burn off carbon and other deposits. Your plugs are not getting hot enough. You need to find out if this is caused by a lower than optimum engine temperature or a too cold plug. The easiest way to do this is by obtaining an accurate plug reading. You can also accomplish this by trial and error, that is, try a hotter plug.

Spirited driving can help the plug stay clean only if it raises the engine temperature into the normal range as opposed to lugging the engine or keeping the RPMs low when the mixture is overly rich in the low range.

The design of the plug is what allows the heat to stay concentrated on the tip or conducted back into the head. You are looking for a chocolate brown color to indicate the proper heat range.

This is somewhat complicated by the mixture. Even if you have the proper heat range, an overly rich mixture will give the indications of a cold plug unless you really know what you're looking at. If you are sure your mixture is good and your plug is still sooty and black at normal operating temps, then your plug is too cold.

The Bosch W3 plugs use platinum on both firing tip and ground electrode. This is why they are $15.00. All the iridium plugs use a base metal (usually nickel) for the ground, except racing plugs which are another whole discussion.

Platinum is expensive and hard to weld onto the base metal but the fine wire gets really hot and burns off deposits and residue. They are worth the money in a turbocharged application for a number of reasons. One of these reasons is your desire to work well in both street and track applications. But, you still need the proper heat range...

Thanks,
Mark

[GJF]

Hey Doug,
While you did switch plugs you stated you were running Bosch F2CS. The NGK heat range 9 is the same as Bosch 2's. So unfortunetly you stayed at the same range.
Let me re-word this about ambient. Although the ambient air outside changes to what ever the temperature it is currently, it is in fact the temperature of the plug that is what's important as Mark stated. But the outside ambient WILL have an effect on the duration a given motor will reach it's operating temperature. So if your plugs are too cold to begin with and the ambiemt temp drops dramatically it will effect the engines overall operating temperature and affect the plugs as well. Once you reach the optimum plug heat range the ambient temp would be less of a factor. If it is fouling that fast then I would try a heat range of 7 now and as long as it stays clean watch it carefully when summer comes and inspect them to see how the combustion is with those plugs and go from there.

[dsiegel360]

Originally Posted by lucittm

The design of the plug is what allows the heat to stay concentrated on the tip or conducted back into the head. You are looking for a chocolate brown color to indicate the proper heat range.

This is somewhat complicated by the mixture. Even if you have the proper heat range, an overly rich mixture will give the indications of a cold plug unless you really know what you're looking at. If you are sure your mixture is good and your plug is still sooty and black at normal operating temps, then your plug is too cold.

The Bosch W3 plugs use platinum on both firing tip and ground electrode. This is why they are $15.00. All the iridium plugs use a base metal (usually nickel) for the ground, except racing plugs which are another whole discussion.


Thanks,
Mark

Mark,
Thanks for the help.

The F2CS is a racing plug. I've been trying to find out exactly what that means and exactly what the heck the F2CS is made of. I've not found a detailed description of this plug on the net. Can you tell me what a racing plug is?

My mechanic builds porsche race engines and does EFI conversions regularly. We spent much time tuning. First on the dyno, then at the track, and again about 4x on the street. He is not suggesting I change plugs, only clean them and gap at .028.

BTW, as per your question yesterday, the NGK iridium 9 now has a glossy brownish coating on the insulator.

A friend on this forum who has a high horsepower EFI car suggests 7's for street and 9's for track. From your explanation, it seems that Platinum Bosch might solve the problem (if the car is tuned correctly.)

Does anyone on this forum use W2's on the street without fouling?