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Old 11-18-2008, 03:54 PM   #21 (permalink)
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Plug erosion?

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Originally Posted by OfficeLinebacker View Post
Yeah but it's going to be the "best" path. If the "preferred" anode experiences wear, there are three others waiting to take up the slack.

I think it's more of a durability thing. I don't know if the path of least resistance is necessarily the best path in terms of combustion.
IMHO, this spark plug "thing" is out-of-control !
For example, plug indexing. Lots of talk about the gaps facing where? And, how much gap? what shape the gap?
Then we have tip types, tip material? Tip shapes? Booster gaps? Resistor gaps? Plasma ? Extended tip? Surface gap? Wow!

Let's start with indexing ... as long as the gaps all point the same way, we're half-way home. But which way? There are as many answers as Carter has pills ( a matter of opinion ). Rather than discuss ( ad infinitum) thread starting points on the heads or plugs, or both - let's just make them all the same, following the directions. For those cars with manifold hassles, start with the worst case ( plug access ), letting this plug dictate which way the other plug gaps must point. THEN, we must power-time, to get the max from the engine. In the case of OBD-II ignition systems, this system will power-time for you...constantly! All driving conditions, all parameters.

I love plug indexing washers! Mr. Gasket Co. sells 'em...as do most car parts stores (NAPA). Just follow the directions...and don't worry about power-
timing ( unless you've got an earlier engine). Make all the gaps point the same way...and let power-timing wake up the engine. Power-timing is the secret behind most mods.

The other stuff? I'll do another post....


Last edited by whitevette; 11-18-2008 at 04:04 PM..
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Old 11-19-2008, 01:55 AM   #22 (permalink)
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Wait.

On many V8's, pointing all the plug gaps in the same direction will actually mean that they are pointed in different directions relative to the I&E valves in different cylinders.

Also, there's still no conclusive evidence that one orientation is best for all engine types.

How accurate is the "point the gap towards the exhaust valve" rule of thumb?

I also do feel that the indexing washers do have the issue of making the spark plug protrude less into the cylinder. I'm not so much worried about the compression ratio. It's more that the spark starts say 1/8" closer to the edge, and therefore in a less central location.

IF I were to go to the trouble of indexing, buying a whole bunch of plugs would be the way to go. However, based on so many unknowns, unless I have weeks of time and unlimited access to sensitive measuring equipment, I'm not even sure if, for any given application, one orientation is better than any other.

That all said, check out Summit or Jeg's for indexing washers, if that's the way you want to go.
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Old 11-19-2008, 01:58 AM   #23 (permalink)
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stillen did a back to back dyno test run on 3 different vehicles at a meet I went to about plug indexing and it showed on average about a 3hp gain on
a V8 and right around 1hp gain on a inline 4..

this was when I lived in CA..

I too brought up the thing about the compresion ratio with shims, ect..
they said it wouldn't change the cc's at all and if any change were made,
the indexed plugs would more than make up for the ever so slight change..

point the plug gaps to the exhaust..
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Old 01-24-2009, 07:43 PM   #24 (permalink)
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Bumping an old thread, but I'm curious about the theory behind the spark plug orientation. If they all face the same way, this should allow a more identical burn between cylinders, right? But what's the reason for having them face the exhaust valves?

Honda was nice enough to post a video of the R18 engine found in 2006+ Civics. You get a nice view of the spark plugs from about 0:43-0:45. The plug gaps are all facing the intake valves. Maybe this is just a marketing video, and I shouldn't read too much into the plug orientation?

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Old 01-24-2009, 10:19 PM   #25 (permalink)
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Quote:
Originally Posted by fanamingo View Post
Bumping an old thread, but I'm curious about the theory behind the spark plug orientation. If they all face the same way, this should allow a more identical burn between cylinders, right? But what's the reason for having them face the exhaust valves?

Honda was nice enough to post a video of the R18 engine found in 2006+ Civics. You get a nice view of the spark plugs from about 0:43-0:45. The plug gaps are all facing the intake valves. Maybe this is just a marketing video, and I shouldn't read too much into the plug orientation?

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It has to do with flame kernel propagation. There's an ideal positioning of the ground electrode in terms of optimum combustion efficiency.
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Old 01-25-2009, 09:56 PM   #26 (permalink)
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the little arm of the spark plug blocks the incomming air/fuel
from directly contacting the section of the plug causing the spark..

less likely to foul the plug this way..

I think I explained that right
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Old 01-25-2009, 10:05 PM   #27 (permalink)
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Fouling is not an issue. Remember, it's a fairly homogeneous mixture of finely atomized fuel in air.

Now just HOW homogeneous, etc is up for debate, but the mixture is ignited no matter what--otherwise the engine would miss.
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Old 01-25-2009, 10:11 PM   #28 (permalink)
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I know its not about fowling, it was just an example..


if anything it just goes with the flow..

i wonder if any gain could be had with a knife edged spark plug arm facing the intake?
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Old 01-25-2009, 10:20 PM   #29 (permalink)
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very VERY rough mockup..

I'm no MS Paint artist
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Old 01-25-2009, 10:26 PM   #30 (permalink)
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While the spark plug washers don't offset compression enough to worry about, they DO offset compression, period. Then again, just moving your plugs around to get the proper torque offsets compression... and just RUNNING your engine offsets compression for each stroke... so maybe we shouldn't worry about such small, inconsequential things?

When indexing spark plugs, the rule is generally to point the plugs toward the intake valves on plug-in-center engines, and toward the exhaust valves on plug-on-side engines.

I wonder where to put them on a Wankel?

I doubt knife-edging a spark plug would do much, but I have heard of gains from "clipping" the plugs for high RPM use. (removing the part of the electrode after the bend, and gapping the plug from the side of the one sparkey thing to the inside of what's left of the electrode.)

Generally, just measuring your cylinder depth through the spark plug hole at TDC and getting a plug that is 1/2 that depth will also be beneficial, since they're not always set up that way from the OEM.

Checking/setting gap based on your engine, not your owner's manual... when's the last time your owner's manual was experiencing high-speed glazing?

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