Spark plug indexing- which direction - Toyota 1ZZ-FE

[topcat]

As it is time for a plug change, I think I shall go the extra mile and index the plugs when I put them back in. (That is, have them face all the same way). But which way is correct? Gap towards the front of the car or gap towards the back. The engine is the Toyota 1ZZ-FE (2005 Celica) quite a common engine used on lots of Toyotas. NB the "FE" is short for fuel efficiency I am told.
The gains from indexing the plugs may be small, but they must be real, otherwise why would Honda do it as standard on the Insight.
The 1ZZ-FE has the intake manifold at the front of the car and the exhaust manifold at the rear.
See:
en.wikipedia.org/wiki/File:Toyota_1ZZ-FE_engine.jpg

Are any of you intelligent people familiar with this and able to offer a simple answer such as "place all the electrodes to the back, gaps at the front".
Thanks in advance.

[Daox]

I probably wouldn't bother indexing plugs with that engine (in fact, I had that engine and didn't bother in my '03 Matrix). The Honda lean burn engines like to index their plugs, but they're running them lean and relaible ignition is critical to them. The lean burn engines are also designed to take advantage of the indexed plugs. With a normal engine running stoichiometric air fuel ratios you aren't going to see the benefit that you would if you were running lean. You might get a fraction of an mpg boost, but I highly doubt it would be noticable.

[TheEnemy]

I agree with Daox, you probably wouldn't be able to measure a difference.

There are 2 schools of thought though as far as which way to index your plugs.

1. If the plug is off center index it towards the middle of the combustion chamber.

2. Index to favor the exhaust valve. Favoring the exhaust valve is supposed to help some with pinging, or detonation, it gets fuel burned in the more susceptible area first. This is probably only usefull if you have a tendency to have detonation otherwise it wouldn't make any difference.

However the diffenece in timing of the flame front is miniscule with a difference of 1-2mm for the flame to travel.

[EdKiefer]

you want the gap towards the open area of the head . Are the plugs directly in top, center of head like many foreign double over head cam heads ?

[honduh]

I would face the gap towards the incoming intake charge, so towards the intake manifold.

[topcat]

As far as I can tell, the plugs are central to the cylinder. I had heard that they should face the intake to allow longer burn time??? The returns may be minimal, but I am happy to spend an extra 10 mins to get a free 0.1 mpg!

[Daox]

Its not just a matter of time. You need copper washers to space the spark plugs so they tighten down at the right angle. Honda uses these and they come in a variety of thicknesses so you can get the angle right.

[Old Tele man]

...the Honda Insight uses indexed spark plugs, and Honda has four different spark numbers to achieve the correct plug orientation.

[darcane]

Originally Posted by topcat

The engine is the Toyota 1ZZ-FE (2005 Celica) quite a common engine used on lots of Toyotas. NB the "FE" is short for fuel efficiency I am told.

That is kinda right...

In Toyota terms
E means Electronic fuel injected.
G and F mean DOHC, G is more for performance, F is more for efficiency.

[EdKiefer]

http://locost7.info/files/engine/1zzfe.pdf