NGK: DPR8EA vs. D8EA?

[Brent Evered]

My wife's 450 rebel has (and is supposed to have) DPR8EA plugs in it. They
need replaced, and I have a big supply of D8EA plugs left over from a couple
of other bikes I've owned but have sold. In the past, if my memory is
holding up, I had a bike that called for D8EA in Canada, and DPR8EA in the
US (or vice versa?).
Any idea what the implication would be of using the D8EAs in the '86 450cc
Honda engine? I'm not overly concerned about the R (resistor) rating; more
the P (insulator) rating.
\thanks for any help with this
\brent

[FB]

Post by Brent Evered
My wife's 450 rebel has (and is supposed to have) DPR8EA plugs in it. They
need replaced, and I have a big supply of D8EA plugs left over from a couple
of other bikes I've owned but have sold. In the past, if my memory is
holding up, I had a bike that called for D8EA in Canada, and DPR8EA in the
US (or vice versa?).
Any idea what the implication would be of using the D8EAs in the '86 450cc
Honda engine? I'm not overly concerned about the R (resistor) rating; more
the P (insulator) rating.

DPR8EA is an extended tip plug that puts the flame kernel further into
the combustion chamber where swirl and turbulence will keep the plug
cleaner.

The engine will be more responsive to part throttle and low speed
running.

But, it may run so hot that the engine pings from a glowing ground
electrode.

Listen for tinkling sounds that sound like a loose valve when you run
extended tip plugs and look for the evidence of mild pinging, which
would be black specks that look like pepper burned onto the insulator.

If an engine is really lean and pings, you might see little silver
balls of melted aluminum on the insulator nose as excess heat tries to
burn a hole in the piston.

D8EA has a shorter insulator nose that doesn't extend as far into the
combustion chamber, it will run a little cooler and the voltage
required to jump a gap depends upon the temperature of the firing
points. The engine with D8EA's might feel like
it's cold blooded and the insulator nose's carbon indications might be
that the mixture is too lean, but richening the mixture doesn't seem to
help much.

That engine will run better at high RPM.

[OH-]

"FB" <***@yahoo.com> wrote in news:***@e56g2000cwe.googlegroups.com...
<snip>

Post by FB
D8EA has a shorter insulator nose that doesn't extend as far into the
combustion chamber, it will run a little cooler

<snip>

I might be a bit confused here, but are we not talking about two
plugs with the same heat number ?

[Mark Olson]

Post by OH-
<snip>

Post by FB
D8EA has a shorter insulator nose that doesn't extend as far into the
combustion chamber, it will run a little cooler

<snip>
I might be a bit confused here, but are we not talking about two
plugs with the same heat number ?

Yes, but positioning the tip of the plug in a different area of the
combustion chamber might well result in the plug attaining a higher
temperature, despite the thermal resistance of the two types of plugs
being the same, simply because that spot has a higher average temperature.
Or I may be talking a load of old cobblers.

[John Johnson]

Post by Mark Olson

Post by OH-
<snip>

Post by FB
D8EA has a shorter insulator nose that doesn't extend as far into the
combustion chamber, it will run a little cooler

<snip>
I might be a bit confused here, but are we not talking about two
plugs with the same heat number ?

Yes, but positioning the tip of the plug in a different area of the
combustion chamber might well result in the plug attaining a higher
temperature, despite the thermal resistance of the two types of plugs
being the same, simply because that spot has a higher average temperature.
Or I may be talking a load of old cobblers.

Mind, none of this answers the OP's question: is it ok to run the bike
on the other plugs?

Me, I'd stick with the recommended plugs. The OP could take that lot of
unused plugs and see about selling them or perhaps swapping someone for
the correct ones. I've heard that a shop here in town will swap NIB
plugs if they're of a brand and designation that they keep in stock, so
maybe the OP could try that.

OTOH, based on what's been said here so far, if the other plugs fit,
then they're unlikely to damage the engine though you might very well
find that the bike doesn't perform as well. Let me say, however, that I
really don't know what would happen because I don't have the relevant
experience.

[T Shadow]

Post by Brent Evered
My wife's 450 rebel has (and is supposed to have) DPR8EA plugs in it. They
need replaced, and I have a big supply of D8EA plugs left over from a couple
of other bikes I've owned but have sold. In the past, if my memory is
holding up, I had a bike that called for D8EA in Canada, and DPR8EA in the
US (or vice versa?).
Any idea what the implication would be of using the D8EAs in the '86 450cc
Honda engine? I'm not overly concerned about the R (resistor) rating; more
the P (insulator) rating.
\thanks for any help with this
\brent

***********************************************************************
the difference from one heat range to the next is the ability to remove
approximately 70°C to 100°C from the combustion chamber.A projected style
spark plug firing tip temperature is increased by 10°C to 20°C.
from:

http://www.ngksparkplugs.com/techinfo/spark_plugs/overviewp2.asp?nav=31000&country=
********************************************************************

The site also has a pdf file with a chart to decipher their plug
designations. The info is fairly easy to find.