Spark plug position matching

[Tempest-Racing]

I have read that this is done in karting and on American V8's where the opening of the plug is positioned towards the exhaust valve. It is set to optimise the combustion, reduce EGT etc..

Anyone got any experience of this? Any dyno tests to prove this does work?

[RPD Motorsport]

The theory is to present the smallest cross section to the direction of the gass flow, i.e. from intake to exhaust side. Hovever in rolling road tests it has no mesurable differance (to within 0.1 bhp at the wheels). But an engine dyno would be needed to rule out everything.

Postioning your injectors correctly though... well, try it- its worthwhile in most cases.

[GORDON STREETER]

There was an article on this many moons ago in one of the comics playing about with spacing washers.
As RPD said it made no measurable difference, at least on the engines that were used at the time. Whether or not it would make a "gnat's knob" difference into the first corner of a "one make" series is anyone's guess

[zefarelly]

I've noticed in an old head the plug area being relieved, spacers are common to stop the plugs hiting the pistons and to get the plug in the right position, but electrde positioning is a new one to me. the reliefs I've seen are on the chamber floor, presumably to give a bit f breathing space should the electrode point towards the chamber floor.

[JohnD]

Recent thread on the TRR MsB, about the benefits of multi-electrode plugs.
I'm now 'contracted' to do a double blind test on my, yet to be built, new engine.
If multi-electrodes are so "marvelous", then the position of a single one must be irrelevant. Or is my scepticism showing?
http://www.tr-register.co.uk/forums/...1&#entry199362

JOhn

[Al Weyman]

Could the improvements on the old Triumphs be more down to the plugs working better with an ineffiecient points ignition system and maybe on something like my MSD souped up HEI GM system with 36 thou (recommended on race engines) plug gap would not make so much difference. Having said that if it improves an ineffiecient system then how bad, maybe FIA will the ban them for Histos!

[phoenix]

Maybe worth reading item 4 on this NGK website page:

http://www.ngksparkplugs.com/techinf...n.asp#indexing

[zefarelly]

articel makes sense . . . how long does a plug spark for on average ?

I'd imagine you want the spark to ignite fuel as quickly as possible, with minimal opportunity to get extinguished/blown out, so one might argue its dependant on cam timing and ignition timing ( can't think you'd trigger a spark with a valve open? )

[phoenix]

Originally Posted by zefarelly

articel makes sense . . . how long does a plug spark for on average ?

I'd imagine you want the spark to ignite fuel as quickly as possible, with minimal opportunity to get extinguished/blown out, so one might argue its dependant on cam timing and ignition timing ( can't think you'd trigger a spark with a valve open? )

Spark duration is normally between 1 and 2 milliseconds I believe. At 6000 rpm that's between 36 and 72 crank degrees if my maths is right.

If I remember correctly, a richer mixture is easier to ignite than a lean mixture. As the mixture inside the cylinder is unlikely to be 100% homogeneous - there will be areas of weak mixture and areas of rich mixture - conceivably 'indexing' might be beneficial in increasing the speed of ignition by pointing the spark towards an area of slightly richer mixture to get more accurate ignition timing and therefore maximise cylinder pressures and get a more complete burn?

The inlet valve and the exhaust valve will surely both be closed at the point of ignition, otherwise there would be no compression of the mixture, so cam timing can have little to do with it.

[Tempest-Racing]

We have in the last week had the engine on the dyno with our tuner who is based in France. The car is a Dallara F301 with a Toyota engine. ex Spanish F3 car. My tuner had spent several hours to determine the correct angle and found a 3 bhp increase but more interesting was the extra 7mn of torque. The car been used for the last 3 years competeing in spint and hill events in Algeria.

[phoenix]

Originally Posted by Tempest-Racing

We have in the last week had the engine on the dyno with our tuner who is based in France. The car is a Dallara F301 with a Toyota engine. ex Spanish F3 car. My tuner had spent several hours to determine the correct angle and found a 3 bhp increase but more interesting was the extra 7mn of torque. The car been used for the last 3 years competeing in spint and hill events in Algeria.

Can you tell us what the increases in BHP and torque are in percentage terms? I think that would be of greater interest than the actual gains in units.

[Tempest-Racing]

Originally Posted by phoenix

Can you tell us what the increases in BHP and torque are in percentage terms? I think that would be of greater interest than the actual gains in units.

1.4% for BHP

3% for the Torque

We did some more work last week on the dyno and we managed to increase that to 2.6% BHP and 4.7% Torque by changing to a different kind of plug.

Thanks

[zefarelly]

5% is worth having

never quite understood plug technology myself, or bothered to learn. . . runnig a pints system I may as well have a flint on the top of the piston and another on the head!