Another spark plug thread
 

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.

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?

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.

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.

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

[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?

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:

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

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.

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:

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.

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?

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

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

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.

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?

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

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.

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?

Rather than welding the multiple ground electrodes onto a steel shell, the entire outer shell and ground electrodes on racing plugs are machined from a single piece of steel. That is really the only difference besides them being hand made. I am running W3CS plugs now with no fouling even idling at 12.5 AFR. Dark dry brown ceramic insulators.

F= 14mm X 1.25 pitch thread and a 16mm hex
2= heat range
C= Reach 19mm
S= Silver

W=14mm X 1.25 pitch thread and 21mm hex
3= heat range
C= Reach 19mm
S= Silver

Thanks GJF. Should the electrode and everything else at the top of the plug be brown too?
Do you run the w3's at the track? What kind of HP are they supporting?

I prefer the insulator to be mocha brown and the strap should see a slight dis-coloration at the end to the bend and then stay consistant to the base of the plug. Some may like it cleaner than that but I am safe and I like the cruise to be in the high 13's and on boost in the extreme low 12's. On my car I have a EFI 3.4 with twin Garretts, big valves and ported heads running a little over 770HP @1.5 and typically run a hair over 650HP @ 1 bar.

Holy Mother Of God! :eek:

Thanks. I'm with you. Run a bit richer and keep it safe.

Here is a link to the reference data provided by GJF:
http://www.boschautoparts.com/NR/rdonlyres/C77B3446-232B-4AEC-AFA9-AD05F2A0A2AD/0/DesignationCodes.pdf

As he mentioned, his AFRs are spot on and his plug heat range is perfect for his application. Your application is different and the plug characteristics will not be the same so the comparison is for information only.

Your mechanic has recommended 7's for street. I think that is a good start.

You mentioned "track". What does this mean? If you are speaking about autocross, I would stay with 7's. If you are talking the 24 hrs of Le Mans, then 9's are appropriate.

BTW, Spuggy was right about the history of Porsche turbo plugs. They spec'd Bosch WR3DP0 for the 930. It is an ice cold plug. The thought was that it is better to use a top grade cold plug than a lesser grade warm plug because, after all, we are just silly American drivers.

For the 964 turbo introduction in 1991, they spec'd the Bosch WR6DP0. This is the plug that should have been in the 930. It is expensive, but it will not foul except in the worst conditions and it will outlast standard plugs in the turbo application.

As you can see the WR6DP0 breaks down as:
W= 14mm X 1.25 thread pitch and a 21mm hex
R= Resistor type
6= Mid range in the heat scale
D= 19mm reach and 3mm tip projection
P= Platinum electrode and ground
0= No deviations from original design

Thanks,
Mark

If the plug is sparking, it's not fouled (although it might be dirty). If it's fouled, there's no flame path to clean it, because the motor isn't running on that cylinder.

Raising the temperature of the flame path can perhaps clean a plug that's borderline dirty and going to get fouled if you don't do something with it.

But that's a plug that's too cold and has no tolerance for running out of the temperature range.

Whilst I'd love to tell you that my daily driver gets wound up at full throttle to redline in at least 2 gears every time I take it out, that would just be a fantasy.

Traffic and short (15-20 miles) journeys with a maximum speed limit of 35 tend to preclude winding out 930's.

And weather. With 255/40/17's out back, I've noticed that damp conditions make abrupt throttle opening quite pointless. So now I just drive like there's a brown paper bag full of doggy-do on the throttle pedal in the wet.

I will tell you that I've driven the car in (re-)freezing slush, and on mornings where I had to use an ice chisel on the windshield to get the frost off before de-icing the door locks and using the demister to the point where I could see through it before driving off.

Car had no thermotime switch connected (and thus no CSV operation) during this time, but always started well, and, despite sometimes months of being driven with a healthy amount of respect (read: fear) for the lack of traction available, has never fouled a factory W3.

In 30 years of motoring, I've never changed the heat range of a set of plugs because ambient temps changed. The combustion temperature is kind of fixed by physics, in my view. YMMV.

Higher Compression Ratios/Forced Induction
will elevate spark plug tip and in-cylinder temperatures!

Compression can be increased by performing any one of the following modifications:

a) reducing combustion chamber volume (i.e.: domed pistons, smaller chamber heads, milling heads, etc.)
b) adding forced induction (Nitrous, Turbo charging or Supercharging)
c) camshaft change

As compression increases, a colder heat range plug, higher fuel octane, and careful attention to ignition timing and air/fuel ratios are necessary. Failure to select a colder spark plug can lead to spark plug/engine damage!


Advancing Ignition Timing

Advancing ignition timing by 10° causes tip temperature to increase by approx. 70°-100° C


Engine Speed and Load

Increases in firing-end temperature are proportional to engine speed and load. When traveling at a consistent high rate of speed, or carrying/pushing very heavy loads, a colder heat range spark plug should be installed


Ambient Air Temperature

As air temperature falls, air density/air volume becomes greater, resulting in leaner air/fuel mixtures.

This creates higher cylinder pressures/temperatures and causes an increase in the spark plug's tip temperature. So, fuel delivery should be increased.

As temperature increases, air density decreases, as does intake volume, and fuel delivery should be decreased


Humidity

As humidity increases, air intake volume decreases

Result is lower combustion pressures and temperatures, causing a decrease in the spark plug's temperature and a reduction in available power.

Air/fuel mixture should be leaner, depending upon ambient temperature.


Barometric Pressure/Altitude
Also affects the spark plug's tip temperature
The higher the altitude, the lower cylinder pressure becomes. As the cylinder temperature de-creases, so does the plug tip temperature

Many mechanics attempt to "chase" tuning by changing spark plug heat ranges

The real answer is to adjust jetting or air/fuel mixtures in an effort to put more air back into the engine

But to add to this it is also recommended to use the manufactures base line spark plug. From there for every 100HP over stock it is recommended to change 1 heat range. It all depends on the particular engine combination. I think if you have a factory car with modifications the spark plugs used would be close to the factory recommended. But when you create a engine with drastic performance modifications that is creating twice or even three times the original power output. The requirements will change for that combination.

Hi Doug,

Great thread about plugs for turbo engines. I think the biggest problem here is lugging this engine. I believe a slightly hotter plug would only help in this particular situation.

I wish the car was still here in NY.

Bill

I think you have to be careful when you check the plugs. If you just dawdled over to your mechanics(or house) in low speed traffic in a bogged down rich running turbo car, I think they will always look like crap. Try checking them after the normal spirited driving that you probably usually do. I bet if you pulled over after a nice highway run, they would look much better and much of the crud would be burned off???

Thanks gang. This has been the most informative plug thread I've seen. I'll post results soon.

ressurecting an awesome info-packed thread.

Here's some more info:

On my supercharged 3.2 race car running 11 lbs, twin-plug, 98RON and EFI I have been fouling plugs. We did quite a lot of troubleshooting on the car today for a non-starting issue and it was indeed fouled plugs.

I have NGK9EIX on the tops and NGK8EIX on the bottoms. Both fouled.

I am replaceing these with NGKBRES tomorrow (hotter on the tops and same at bottoms but both sets standard-type rather than Iridium) and hope to overcome the fouling issue. Will tell more tomorrow.

Subscribing

Japanese plugs know when they are in a German car, they get uncomfortable. They start talking to each other whispering from #4 to #5 "Hey how cold are you?" And then #1 chimes in from the other side "Man it's fricken' cold in here, let's foul out and get outa here!"

Fouling is the carbon trail from the tip, down the insulator, to the base where the spark is grounded. Wire brushing makes the plugs worse. The only thing I found to fix some of these plugs is sandblasting. But it damages the soft platinum, so there you go.

Put in some Bosch plugs, I recommend WR6DP0, and you should have no more fouling problems. There IS something about that platinum stuff.

Unless your AFRs are out to lunch this should help. (You didn't say what your AFRs were.)

Good Luck,
Mark

What about ignition? Would a weak ignition cause fouling problems as well?

John, what ignition system are you running?

We popped an oscilliscope on the coil grounds, the coil is definately trying to fire but actual spark is intermittent. We then pulled each lead individually and verified each of the 12 leads will fire a clean, new plug.

I am running 2x Accel EDIS-6 coils (new) by a pair of Haltech triple-channel ignitors. Driven by Adaptronic ECU.

John:

I only have experience with NGK's and can tell you this: NGK 9:s are really cold "snowmobile" plugs which are 99% overkill on the street and will foul quickly. I would start with 7:s and maybe go up to 8:s if driven on the track. (Don't mix up NGK and Bosch numbers, they aren't compatible).

I haven't experience any drastic improvements with rare-metal plugs over ordinary ones, so I still run with 2$ NGK's and they work fine. There is probably difference in longevity though.
I switched from 2$ NGK's to 15$ platinum Bosch's on my Audi S4 and there wasn't any discernable difference.

Also, wastefire EDIS coils aren't powerful and will be sensitive to plug gap.