Spark plugs choice vs low compression and high boost

[Jeffer]

I'm wondering if I'm going to use different spark plugs with the 7,9:1 compression ratio........
I'd like to know what others think of this!

Cheers

[kwlw]

I'm wondering if I'm going to use different spark plugs with the 7,9:1 compression ratio........
I'd like to know what others think of this!

Cheers

Don't know if it's true, or bull**it, but there's something I've downloaded from web year ago. Maybe it will give you the direction for further search:

Here's some info I grabbed from AudiWorld. I showed Big D and he didn't believe it at the time. Suxor for him....now he has seen the light. :wink:
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After chipping my 03 1.8T the other day to a 1.5bar program, I noticed some problems.

1) Slight missfiring/blowouts at ~5000RPM on 4th gear
2) Slight Pinging (which leads to pre-ignition/detonation) at high boost
3) Loss of power past 5000RPM (due to the size of our K03's...as well as sparkplug gapping/etc)

So on Saturday morning, I pulled out my OEM plugs, and this is what I found:

1) Don't know about the 02's, but my 03 OEM plugs are actually "NGK"...model number BKR6QP (Defined as: B = 14mm thread diameter, K = 5/8" projected tip, R = Resistor plug, 6 = Heat Range 6, Q = 4-ground electrode, P = Platinum)
2) Sparkplug is actually UNDERGAPPED, where NGK states all their plugs that dont have a (-xx) gap number to it, they should all be factory gapped at 0.0315". My OEM plugs were gapped at 0.027"!!! (Probably lost a good 5hp from that alone)

With my many years of sparkplug tuning and fiddling, I went to a local Kragen, and purchased a COPPER plug with the same specs mentioned above: BKR6E-11. Same plug, just in a copper form, with a bigger 0.044" pregap.

I gapped the plugs from it's specs (0.027"?) to 0.032". The minute I fired up the car, the exhaust tone became a LOT deeper. So I took the car around the block, then on the fwy doing some 0-100MPH runs. The car became a LOT smoother. The powerband of the turbo will now make boost past 5000RPM, and the spoolup got a LOT quicker. The "Hesitation" at 5000RPM disappeared, and the idle became a lot smoother. Simply switching the plugs, I would say that my "***-Dyno" pretty much felt another 5-10hp difference in power. (will do a VAG-dyno soon.)

Now many would ask "Why use Copper when they sell Iridiums???" Well first of all, before my explanation, simply switching from platinums to standard coppers will lower your EGT temps anywhere from 30-40C Degrees!...read on:

Well, here is my explanation:

Personally, I think Platinums and Iridium plugs should be BANNED from all forced-induced cars (turbo/supercharged).

I have done sparkplug tuning for many years now (indexing/j-gapping), and I've found Platinums/Iridiums to be inferior to copper plugs in a turbocharged environment.

Platinum plugs (and Iridiums) were introduced to provide longevity (60k-100k+) to vehicles compared to copper plugs which foul after 3000-5000 miles, but they do NOT dissapate heat fast enough (which leads to pre-ignition/detonation) and do NOT provide a "better spark" like they have claimed...with their "fine-wire electrode" (which only causes problems).

Copper is one of the best conductors, but they just plain dont last. Using Platinum and Iridium plugs, the center electrode (fine-wire) thin, that under high boost, they get so hot, they will begin to "heat glow" and cause premature ignition in the combustion cycle (pre-ignition => detonation). This is a problem for all of us turbo guys. Copper on the other hand, has a much thicker center electrode, on top of that, the copper material is able to dissapate heat from the combustion chamber fast enough to keep the combustion temperatures lower.

Remember the TWO primary functions of a sparkplug:
1) To efficiently ignite the A/F mixture without missfires (gap..etc)
2) To pull heat from the combustion chamber into the head, where the cooling system should dissapate that heat. (Heat Range)

With those 2 in mind, coppers will work much better in these environments. For those thinking: "What If I just simple use a colder Platinum plug?" Well, for the kind of boost our A4's make w/ the Krispy-Kreme K03's (1.2 bar..and in my case... 1.5bar), we will reach EGT's of over 900C Degrees (keeping in mind that Pre-ignition occurs at around 870C). Once those colder platinums reach preignition temperature, it will take them FOREVER to dissapate that amount of heat (with the details about the material/design I mentioned above). A platinum/Iridium plug in a colder heat range usually runs just as hot as a copper in the standard heat range when under high stress. So many people will use a Platinum/Iridum plug TWO steps colder to counter that. But using a plug that is 2 steps colder, will lead to two things:
1) More prone to carbon-fouling on "normal driving" where EGT's are kept low. (Plugs must stay above 550C Deg to burn off excess carbon deposits to "self-clean")
2) As a result, loss of horsepower.

You need a plug that is actually "hot enough" to ignite the A/F mixture as hot as possible to get the most efficient combustion, as well as burn off carbon-deposits (~550C deg), and yet cold enough to prevent pre-ignition when compression is high (< 870C Deg).

With all that said, for those interested in going copper the "feel the difference themselves", I recommend the following plugs:

NGK: BKR6E, BKR6E-11 (-11 indicates a 0.044" pregap, which should be regapped anyways)

Denso: K21R, K21R-U11 (bigger pregap)

I have personally used a colder plug, because my chip is making 1.5 of INSANE boost, and I am personally using the following:

NGK: BKR7E (Part Number #6097), they are one heat range colder than stock (~80C degrees colder than our OEM platium plugs)

Well, here's my $0.02 (maybe $0.03) about this issue, feel free to comment or correct me if you have any concerns.

Happy Boosting

If you look at NGK or even DENSO's part number codings, they will indicate the pregap.

Example:
NGK BKR6E-11, the (-11) denotes a 1.1mm pregap. When part numbers are shown (ie: BKR6E) WITHOUT a -xx, then the default "should" be 0.0315" (you should ALWAYS check)

THUS: -11 = 1.1mm (0.044"), -8 = 0.8mm (0.032")...and so forth...

Every car has different specs that require different gaps. What is "optimum" on my car, may not be on yours.

As a general rule of thumb:
Always use the BIGGEST possible gap that will not break up or missfire. For every 50hp or so, I would drop the heat range about 0.004" or so. I do NOT know WHY Audi gapped 0.027"!!!... according to the part number to the OEM plug, it should be gapped to at least 0.0315"... Shieze!..hehe

But personally...I would use 0.032" as a reference point, either increase or decrease in 0.002" increments til you get it right.

As far as heat range goes, a heat range "#6" will be adequate. Remember, simply changing from platinums to coppers will lower your temps by about 30degrees!

[Doug_RS2]

I'm using standard plugs - with low compression - much the same as yours. I have some NGK iridium tipped ones to try but we haven't had any spark problems on standard ones, so I am just going to carry on using them.

I did have some spark problems at high boost >2Bar, but that was due to a coilpack going weak - changed that and all is fine.

[S2central.net]

Doug - with your EGT meter it would be *very* easy to test the statements above. Quite interesting thinking actually. I can't remember my physics enough to agree or disagree that Cu is a better conductor than Pl. Then you ask yourself where the extra heat goes ?

Can you test this with alternate plugs on your EGT widgit ?

Paul

[jameswkr]

KWLW - did history relate how often the copper plugs needed changing ? Has anybody tried copper plugs on the S2 ? My car did not even like the NGK alternative to the F5DPOR ! James.

[Pisobiker]

thet's interesting, kwlw.

And what about Bosch silver plugs?

[NoNonsense]

Doug - with your EGT meter it would be *very* easy to test the statements above. Quite interesting thinking actually. I can't remember my physics enough to agree or disagree that Cu is a better conductor than Pl. Then you ask yourself where the extra heat goes ?

Can you test this with alternate plugs on your EGT widgit ?

Paul

copper is, in fact, a better conductor than pl...actually, better than silver and most other metals...but copper plugs will require more frequent changes ( i think that was mentioned)

[Doug_RS2]

Can you test this with alternate plugs on your EGT widgit ?

I can give the plugs and the EGT meter to someone else to try - my car is getting garaged/taken off the road, this weekend

[kwlw]

KWLW - did history relate how often the copper plugs needed changing ? Has anybody tried copper plugs on the S2 ? My car did not even like the NGK alternative to the F5DPOR ! James.

As far I remember - you need to change coppers with oil. It means every 5000km or sooner. It of course depens on how hard you push. I think if boost is high, it would be wise to change spark plugs after every track day .

Sau

[Jamo]

Bringing this up from the dead, do people use different plugs when going above 450 bhp?

[Doug_RS2]

I wouldn't use anything but the bosch - and never had issues with them. Every turbod vag car gets these on a service here.

[EspenW]

We are seeing some pretty rapid plug erosion with F5DPOR on a petrol fed RS2 running approx. 355whp (so around 450hp crank). This is with the uprated ignition from 034.
That said, I had no problems with those running the same power on F5DPOR on petrol or with 50whp more on E85. I now run Bosch F3CS to reduce the risk of pre ignition with 2.1bar boost pressure.

More power means more heat in the chamber, and if this gets excessive, pre ignition and detonation will result, so a colder plug might help.

[S2central.net]

I had some thoughts on this before - wanted to try an F4CS - http://www.s2forum.com/forum/showthr...highlight=F4CS

[Doug_RS2]

700-800bhp RS4s are fine for 10k

650bhp rs4s 25k and still ok

500-600bhp gt35 S2s 2.3 bar to 2 bar ok after 10k

480bhp gt30s on S2s 2 bar to 1.7 are fine for 20k.

600-800bhp 996TT are ok for 10k - last better than any other plugs

I would be changing them after 10k anyway. All these cars don't run high egts.

I have had one failed plug in 4 years and i go through 200 ish every 2-3 months.

[EspenW]

Good info, Doug.
I suspect something is slightly off with the plug eating RS2 that I mentioned.