About Plugs

Mike,

For spare plugs, I would stick with the NGK plugs. They are good plugs, and many around think they are of better quality than the Bosch plugs.

As for the differences in your plug deposits, I dunno. I would think they should all be pretty close in color if everything is running good. It could be the CA gas too. Maybe run a tank or two of 92 octane and then pull your plugs to see what they look like.

Good luck!

Dane

Mike Rocket J. Squirrel Elliott wrote:

The plugs in the engine are NGK BP5ES-A. I can't find the "-A" version available. They may be the same as vanilla-flavored BP5ES. Or maybe not. NGK also makes a "-11" version, which is presumably not the same as a plain BP5ES.

I reckon that this Puebla-built 1600's CR is probably low enough to permit usage of PEMEX's Magna Sin (87 octane) gasoline. Unlikely the average bus driver in Mexico would be able to count on finding Premium, which is not always available.

Premium,

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Coupla points:

As of 2002 the Puebla plant assembled two basic versions of the air-cooled flat four, one with dished pistons having a CR of 7.3:1 for the domestic market and one having flat-top pistons giving a CR of

7.7:1 for the export market. Either version may be ordered with hydraulic cam-followers, in which case it will also be fitted with a full-flow oil filtration system using a factory-built filter/pump adapter patterned after the Subaru. The MPFI flat-four installed in Mexican-built bugs used the dished pistons and was derated to 45bhp

Starting in 1992 all fuel sold in Baja California has been trucked in from the Signal Hill refinery (Chevron?) in Long Beach, California. Prior to that time gasoline arrived in Baja via tanker trucks carried over from the mainland on the FERRY. When a tanker was onboard they would not permit any other cars or trucks to use the same ferry. (Passengers were okay.) Fuel consumption in Baja eventually increased to the point where transporting fuel by ferry began to impact tourism and agriculture which also rely upon the ferrys to reach the mainland in a timely fashion.

This practice was still in place as of 1997 but may have changed since.

-Bob Hoover

The -11 version of NGK plugs have a longer ground electrode, specifically 1.1mm or .11cm, hence the "11". It permits gapping the plugs to .044" for those engines requiring the larger gap. That way, the ground electrode will still be parallel to the flat surface of the center electrode to promote longer plug life.

Yes, the -11's would be a good choice for you.

Raymond T. Lowe

-- E-mail=fullname,no >

That makes sense. When I opened the gap on these non -11 versions I could see how having a longer electrode would make it easier to get parallelism. Parallelity? Parallelocity?

I read on another newsgroup that platinum plugs make aircooled engines run hotter. That sounds completely daft. Can a plug affect the temperature of an engine?

I recall the marketing hype saying *the plugs* burned hotter so they essentially burned themselves clean.

This 12 year old memory brought to you by the letter B and the number 6!

Oh yeah, I know that plugs come in heat ranges. "Cold" plugs are built to transfer their heat quickly to the head so that their tips don't get so hot so as to cause pre-ignition in the combustion chamber (detonation). But if a plug runs too cool then deposits will build up on it and foul it. In that case you would want a hotter plug -- one that has more insulation between the tip and the threads so that it gets hot enough to stay clean. NGK plugs seem to come in three heat ranges. I guess that engine running conditions and construction determine the proper heat range that you want. I note that my Mexi 1600 DP has NGK's hot range plugs. In an aircooled engine I wonder why this would be a good choice.

Anyways, the statement I am questioning is that platinum plugs cause aircooled engines to run hotter. Which makes no sense at all and is, I betcha, a silly myth.

I dont know much about plugs.. but from the last couple of posts I would guess that a 'cold' plug that transfers its heat to the heads - would make the heads hotter ! Hot plugs would keep the heat to themselves .

Rich

A *too* hot plug would start to glow and cause detonation, which for sure will overheat the engine in a hurry. Pieces of the electrodes may actually melt off.

Jan

tricky wrote:

In the overall scheme of things I doubt that the increased transfer of a cold plug would affect the head temp much. The tip of the plug is pretty small compared with the mass of the head. This is probably something that Bob Hoover has written about maybe a thousand times. But Google ain't coming up with anything.

That's correct, but the reason that different engines need different heat range plugs is that different engines have different heads which can remove the heat from the plug body at different rates. The heat range of the plug actually only tells you what the thermal conductivity is between the center insulator (the exposed part in the chamber) and the plug body. The final temp depends on that, plus the rate at which the head can carry heat away from the plug body and the temp that the head runs at.

I agree with you. This just doesn't follow, and probably just comes from someone's misunderstanding of what heat ranges actually mean.

I've actually never heard that rumor. It must be some local thing in your area.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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Once the engine reaches equilibrium, almost all the heat into the plug eventually ends up in the head. So the amount of heat that gets to the head will actually be just about the same.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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This makes the whole heat range thing make sense. Thanks.

Mebbe. Heard it from a fellow on Type2.com's listserv. Also seen it on a few websites offering engine advice. Those sites tend to have a lot of misspellings, so I reckoned they were not written by the brightest stars in the sky.