Indexed Spark Plugs -- Nice...

[DracoFelis]

After reading (on this site) about what spark plug indexing is, how easy it is to do, and that it can give you minor FE and performance bonuses, I decided it give it a try. Naturally, my independent mechanic took longer than expected to order the index washers (it wasn't an immediate/crisis thing, so it got low on the priority queue). However, he finally got those indexing washers in, and got around to indexing the spark plugs yesterday (he was already in to replace a faulty door closed switch that was triggering "door open" alarms in the car, so I had him complete the plug indexing at the same time).

While one day (without instrumentation) is far to little time to detect what (if any) FE gains I might get, I was surprised how noticeable other effects were. So far I've noticed the following:

The engine just seems to run "smoother" (not that it was bad to begin with, but...). In particular, the engine previously sounded/felt to me l (especially as low RPMs, such as idling), like the timing between the 4 cylinders wasn't quite "matched" (close, but not quite on). Not that this was enough of an issue to be a problem for me, but I none-the-less noticed it. OTOH this seems to have gone away today (hence the statement that the engine seemed to run "smoother").

I noticed a slight increase in power, in all gears (I have a 5-speed manual transmission, throttle body injected, Honda CRX). Not the the car ever had a problem with power (it always had good get up and go, relative to a lot of cars), but it still seemed like I had slightly more power when I tried (out of curiosity) heavy acceleration.

Surprisingly (at least to me), I found that I could use more throttle at slower speeds after the plug indexing (maybe due to the "smoother running engine", above?). This seemed to be true in all gears, but naturally it was most noticeable in high/5th gear. I was actually able to drive with light throttle/acceleration, going only 20MPH in high gear today WITHOUT any noticeable lugging while doing it (and no I was NOT coasting while doing this, but instead very lightly accelerating in 5th gear)! I suspect this feature is likely to save some fuel in the future, if only because it allows me to shift into a higher gear sooner...

It's too early to tell if the pattern will last, but it seems as if my car now gets to lower RPM idle quicker than it did before. If so, this will clearly be a minor FE savings, as higher RPM idle burns more fuel (at least during those times you are idling). Of course, when I thought about it, this behavior made sense, as my car's ECU is setup to adjust the idle speed to what it thinks is necessary to cleanly keep the engine going. So if the engine is running "smoother" (above), than it makes sense that a lower RPM could keep the engine running. And I wouldn't be a bit surprised if the car's ECU was picking up on that smoother firing/running engine, and lowering the RPM (for idle) more than it has in the past.


NOTE:
There was only two things done to that car yesterday, and only one of them (the spark plug indexing) should have any effect on how the car drives (the other "fix" was replacing a faulty "door open" switch, that was resulting in "door open" alarms going off). So, since nothing else was done to the car yesterday (we didn't even clean and regap the plugs, just pulled them out and indexed them as we put them back in), I attribute all of the changes to the spark plug indexing. And that surprised me, as I wasn't expecting that level of changes, just by indexing my plugs!