"So any thoughts about what this means for the Roadster (s)?"
It is very hard to find good solid info on choosing a plug for a modified car.
For most stock and mildly modified roadsters it seems the stock plug should be
good enough. Open the gap to recommended width for GB/DB electronic ignition
systems, or wider if you feel so inclined with an MSD, Jacobs, etc, system.
For the most part it seems, from what I've read, the fancy plugs, like the
wires, don't really "make" any more power than regular plugs, but they do last
longer, as long as they don't foul out. Having a SYSTEM that provides a
reliable spark is 90% of the job.
If you have a stereo, GPS, or other electronic devices in your roadster, as
pointed out already, you want the R (resistor) in the plug name for
suppression of noise and interference on those items.
I've been running the BPR6ES-11 (pregapped @ .043" ??) for several years with
no problems, but with the EFI and waste spark I thought it was time to
change.
Seems the things to watch for when choosing a plug are thread size, reach,
heat range and gap.
Thread size and reach are pretty straightforward.
Gap depends a lot on what size gap your ignition system is capable of
providing a reliable spark to jump that gap.
Good stock .032", GB/DB EI ~.043", MSD, Jacobs, etc .055" - .060" sometimes
more.
It used to be thought that a larger gap (with a capable system) would ignite
more fuel giving a better, more thorough burn of the air fuel mixture. Some
OEMs had as much as .080" gap.
Lately it seems most OEMs are still at or back to about .043" - .055",
sometimes as much as .060", gaps and high power inductive ignitions which give
a longer duration spark........I can only guess why....??? Does it work
better?
Heat Range is the one that stumps me. Stock for a stock or mildly modified
engine obviously.
But what happens when you modify the cooling system, combustion chamber shape,
increase compression, add a wasted spark ignition system, and efi????
Would a cooler or hotter plug be better?.....Stay the same??
I am guessing I could benefit from a hotter (??) and longer lasting plug. I am
giving the Bosch +2 a shot. #4303.
I believe it is equivalent to an NGK 5 heat range................
This is not a recommendation for any roadster. Just what I THINK might work
for mine.
Please correct me if you feel I've confused the
issues...............................
Cheers
Daryl
Subject: [Roadsters] Spark Plugs - General Info
In case someone else might be interested:
http://www.aa1car.com/library/2004/us30428.htm
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