3.2 euro engine - spark plugs

[ysilvercs]

Hi Guys,

Trying to find out the correct model of spark plugs for my 1986 porsche 911 Carrera 3.2 Euro model.
You can find a lot of information regarding US 3.2 engines but could not find the required information for a ROW/Euro engine.

I prefer to use Bosch or NKG.

Thanks.

[ysilvercs]

Bump...

[IROC]

I think the NGK web site recommends the BPR7ES plugs. My engine is a US engine, but with the Euro Mahle 10.3:1 compression P&Cs. The PO of my engine ran the US-spec 6 heat range NGK plugs, but they looked way to "white" for my tastes. I switched to the 8s, but I think that went too far the other way. The BPR7ES plugs were just right.

[ysilvercs]

Great. Thanks.

[BER]

Porsche's Tech Specification booklet recommends Bosch WR4CC (gap 0.7mm) for the 930/20 engine. The type 930/20 is the RoW engine used in most of Europe.

BER

[jhoagg]

I just went through this and ended up where IROC is - NGK BP7ES (I went non-resistor which seems to work just fine). If Bosch WR4CC is the right plug for the 930/20, that equates to an NGK BR8ES - one heat range colder than IROC and I have. No big deal.

BUT...the Bosch WR4CC is a "non-projected" plug (no "P" in the part number) instead of a projected plug ("P" in the part number). See the difference in the pics below. Here is what NGK says about this difference:

"The projection of a spark plug is measured as the distance from the end of the metal shell to the tip of the centre electrode......A projected spark plug protrudes into the combustion chamber further and provides higher ignitability and improved performance. Simply this can be understood by representing the combustion chamber as a circle. A projected spark plug in effect produces a spark in the middle of the circle (or combustion chamber) allowing for an even flame spread. Conversely, a non-projected spark plug means the flame spread is not even."

So, is the non-projected just older technology? Or should we really be using a non projected plug in these engines? Or is this much ado about not much? Any expert opinions?

[BER]

I may be wrong, but the WR4CC and the WR4CP are the same plug. Only difference is one plug is a copper tip and the other is a Platinum tip. Keep in mind we are talking about 20+ year old Bosch nominclature.

I do not know the equivalent NGK plugs.

BER

[Josh D]

Originally Posted by jhoagg

I just went through this and ended up where IROC is - NGK BP7ES (I went non-resistor which seems to work just fine). If Bosch WR4CC is the right plug for the 930/20, that equates to an NGK BR8ES - one heat range colder than IROC and I have. No big deal.

BUT...the Bosch WR4CC is a "non-projected" plug (no "P" in the part number) instead of a projected plug ("P" in the part number). See the difference in the pics below. Here is what NGK says about this difference:

"The projection of a spark plug is measured as the distance from the end of the metal shell to the tip of the centre electrode......A projected spark plug protrudes into the combustion chamber further and provides higher ignitability and improved performance. Simply this can be understood by representing the combustion chamber as a circle. A projected spark plug in effect produces a spark in the middle of the circle (or combustion chamber) allowing for an even flame spread. Conversely, a non-projected spark plug means the flame spread is not even."

So, is the non-projected just older technology? Or should we really be using a non projected plug in these engines? Or is this much ado about not much? Any expert opinions?

The "projection" you describe determines the heat range. The further the electrode is projected into the combustion chamber, the hotter the plug. Vice versa for colder plug.

[jhoagg]

Josh,
I initially thought that as well, but that does not seem to be correct. NGK, for example, has many plugs with the same designated heat range, but the different configuration of electrode and insulator projection. And NGK itself does not equate heat range with degree of projection.

Just to name two examples: B7ES versus BP7ES. Same heat range, different amount of projection. B6ES versus BP6ES. Same heat range, different projection.

[Josh D]

I guess your right. Looks like the length of the insulator is the determining heat range factor, not the protrusion of the electrode:

NGK Spark Plugs USA

[jhoagg]

Josh
Yeah - that is how I understand that picture too.

My amateur guess is that back in the 80's when our Carreras were new, the benefits (?) of projecting the electrodes out a bit into the combustion chamber were not known. So Porsche specified "non-projected" plugs. I imagine those specifications are now outmoded, and, all else equal, we should use the "P" version "projected" plugs in these engines.

[Josh D]

Originally Posted by jhoagg

My amateur guess is that back in the 80's when our Carreras were new, the benefits (?) of projecting the electrodes out a bit into the combustion chamber were not known. So Porsche specified "non-projected" plugs. I imagine those specifications are now outmoded, and, all else equal, we should use the "P" version "projected" plugs in these engines.

Hard to say for sure, but by the '80s, Porsche had quite a bit of experience with the aircooled flat six in many configurations, including racing versions, so my guess is they had a reason. Might have something to do with the quality of gas at the time. My RoW calls for a very cold plug. It was supposed to run on low octane leaded gas that was available in Europe at the time. Now it runs on a regular diet of 91 octane unleaded swill. Who knows.

[scarceller]

I run iridium plugs in my Euro 3.2 'NGK 6637 BPR6EIX' (heat range 6) and they work real well.
Stock plug is a NGK BP7ES (heat range 7)

I've also found that you can increase the gap from stock 0.7-0.8mm to 0.9-1.0mm and this also helps idle a bit so long as you don't get any hesitation under load.

I highly recommend the iridium plugs as they tend to hold the gap for a very long time.

As for heat range it's simple: use the coolest plug possible so long as it does not dirty and foul. The hotter plug simply has more of the electrode exposed so that it self cleans by the amount of heat it absorbs compared to the cooler plug. So if you burn a tad of oil you should run slightly hotter plug. But heat range of 7 works well in the 3.2L cars.

[Drisump]

I have an 85 Euro 3.2 with little over 100k miles. I've been running Bosch WR7DC+ (iridium) and can say they seem to work fine. After pulling a couple of sets out after 15k miles, their colour and condition has been excellent. I have to say that I normally run Chevron 94 (no ethanol) when driving near home, on long trips I try to find as high an octane as possible but usually have to settle for ethanol tainted stuff. Cheers

[scarceller]

Originally Posted by Drisump

I have an 85 Euro 3.2 with little over 100k miles. I've been running Bosch WR7DC+ (iridium) and can say they seem to work fine. After pulling a couple of sets out after 15k miles, their colour and condition has been excellent. I have to say that I normally run Chevron 94 (no ethanol) when driving near home, on long trips I try to find as high an octane as possible but usually have to settle for ethanol tainted stuff. Cheers

Here's the deal on ethanol or any alcohol based fuel.

First the bad: it tends to bind easily with water and then separate from the gasoline fuel, you can't let it sit long. Then it also has corrosion issues on steel lines and components and our cars have a bit of steel in the fuel track.

Now the good: first google 'ethanol molecule structure' and you'll notice something very interesting and important. All ethanol and alcohol has a 'O2' molecule built into the fuel! What's needed for combustion? you need the fuel and the O2, with plain Gasoline it has no O2 in the fuel itself so all the O2 for combustion MUST gone from the intake air. This means that the charge only contains 21% O2 (what's in ambient air). But with 10% ethanol you have extra O2 built into the fuel, Bonus power! This is exactly why top fuelster drag cars run pure alcohol. Folks often say that ethanol fuel run rich at 7AFR 7 parts air to fuel compared to gasoline at 14.7AFR but this is not really the case, what's going on is that the fuel carries much of the O2 for combustion.

This means that the same motor tuned for gasoline and then tuned for E85 the later will produce considerably more HP and torque. I've seen as much as 25% or more!

Bottom line is that any engine burning ethanol yields more power, you just need to know the trade offs.

[Drisump]

With respect....I have noticed (after documenting) through many miles of operation (on several vehicles) less MPG and less power in a conventionally tuned car running on E85-E90. "Less power" is more "feel" than numbers since I haven't taken these cars to a dyno. Obviously O2 is good for combustion but there is measurably less energy in a litre of ethanol vs a litre of gasoline. So it's my assumption that the high performance use of ethanol overcomes the energy density deficit by simply pumping more of it. (ie. more complete combustion due to the presence of O2 but less power density per litre.) I've also had some fuel system issues on older vehicles that likely wouldn't have occurred without ethanol in the fuel. All those details considered, as long as I have non-ethanol available to me, I will run it in my 85. Cheers

[scarceller]

Originally Posted by Drisump

With respect....I have noticed (after documenting) through many miles of operation (on several vehicles) less MPG and less power in a conventionally tuned car running on E85-E90. "Less power" is more "feel" than numbers since I haven't taken these cars to a dyno. Obviously O2 is good for combustion but there is measurably less energy in a litre of ethanol vs a litre of gasoline. So it's my assumption that the high performance use of ethanol overcomes the energy density deficit by simply pumping more of it. (ie. more complete combustion due to the presence of O2 but less power density per litre.) I've also had some fuel system issues on older vehicles that likely wouldn't have occurred without ethanol in the fuel. All those details considered, as long as I have non-ethanol available to me, I will run it in my 85. Cheers

Clarification question: did you just run E85 but did not retune for E85? You can't just put E85 into an engine tuned for Gasoline it will run way to lean! You need a lot more E85 per gram of air compared to gasoline.

Your point about MPG is correct, you won't get better MPG but you will get more power. Bottom line is you'll consume more fuel and generate more power.

[Drisump]

No, I live in an area where at this time there are still options. What would you recommend? Getting a SW chip to use E85?

[scarceller]

Originally Posted by Drisump

No, I live in an area where at this time there are still options. What would you recommend? Getting a SW chip to use E85?

You can't just run E85 in the 3.2L car best you can do is E10. In order to run E85 you'd need some mods like larger injectors and larger fuel pump. With E85 you need more fuel flow per stroke and the stock injectors are not large enough and the stock FPump is also marginal. I did not mean to suggest that you should switch to E85 I just wanted to clarify that E85 is not a bad fuel, a lot of folks think otherwise and often assumptions have been made about it not being good for power and this simply is not true. It's not good for MPG but certainly is good for power.

If you run E10 in the 3.2L your MPG will slightly drop but your power should also go up slightly. And with E10 the stock setup is fine, injectors and fuel pump are just fine for E10. You ussually need to slightly richen the mixture for E10 to achieve the target lambda. But only very slight enrichment.