Forum for competition engine enthusiasts. RIP Guy Croft 09/11/2020 - This forum will continue both as a source of information and as a memorial to Guy.
Before I start, this isnt just theory just a question of existing evidence.
Does anyone have any data to support that the positioning of a spark plug (ie which way it faces) effects the flow in the combustion chamber?
To explain my thinking:
I saw this and thought if the spark was more exposed by having the prong going round the back of the combustion chamber this would make a better burn?
I know spark plugs do strange things under compression and all plugs act differently however surely if all chambers were equal and spark was in the best postion then the ideal burn would happen, let alone flow during the squish process.
No harm in asking but position has no effect at all on burn and kits for 'indexing' plugs, are, frankly, snake oil, just another 'gizmo' to lighten your wallet.
Plugs don't respond to indexing of electrode position because the whole nose region is drenched in a rapidly compressing and thus highly turbulent fuel/air mixture cloud at time of firing.
Now, about my plug 'n play 'intake air molecule exciter' that adds 1-2% power for less than $50...
I'm sorry but I wasn't aware of a product on the market, it was just a thought purely from that picture...
Thank you for putting that one to rest though.
Cristian.
In my opinion the only difference is that the fuel/air mixture which flows through the inlet valves faces less resistance.So at the same time the cylinder is filled with more fuel/air mixture than it would be if the spark plugs where placed with their electrode's back facing the inlet ports.
Sorry, but this is a complete myth.
There has been numerous Dyno tests trying various tricks including lining up the electrodes, and it adds nothing to the flow. Last one i saw was on an Alfa Twin Spark, and it did nothing.
If it did add something to the flow, then it would be common practice today. All you need to worry about is to make sure the plug hole is free of debris and seals tight but not overtightened. Overtightening i see so often.
Maybe you are right..But this is something that i have also read it in one of the most famous(in my opinion the most accurate & serious) car tuning magazines here in Greece (if someone wants it's name i can send him a message).Of course i don't have the means to verify that applying S.P.I on motor affects the fuel/air mixture input through the inlet valves .I will be glad if through our conversation i come to a final conclusion.
What is written in Tuning Magazines i am afraid is largely fiction or not too near the truth. Most are kept going by the advertisers, so they print stories of how good a certain thing is if added to your car. Its all Snake Oil or proven on a Rolling Road not to work.
If you have a 16V engine, how can you position the electrode for the valves?
There is an argument over using multi electrodes over a single one. I believe a single electrode gives a "fatter spark".
What you need to look at is how much is the valve and spark plug shrouded. And make sure the flow under the valve is flowing well so you cram in as much air as you can to get a big explosion. This will depend on chamber shape.
There are so many variants to worry about then electrode position. Get the head to flow correctly. Use the right induction and exhaust along side correct Cam[s], compression and properly sorted bottom end. Alter one of these variants, and you alter the characteristics of the engine.
sumplug wrote:
If you have a 16V engine, how can you position the electrode for the valves?
What do you mean?I don't think that is difficult to position the electrode's back facing the outlet port.I own a 16V 1.4lt sporting punto and i use single electrode spark plugs (the 1.2 16V MK2 as far as i know uses twin electrode).
About the magazines ,i don't disagree but i have read many articles/opinions over the web ,without advertising any products.Just theory :)
Konstantinos
Last edited by P.A.D.R.C on July 9th, 2007, 1:57 pm, edited 1 time in total.
Theory is just that. Its some ones opinion. Without proof of working, it means nothing. So many people today buy goods from so called "tuning experts", only for the things not to work. I have lost the countless times, people have spent good money for the engine to show no real gains over standard on the rollers. Yet they could be into a few thousand pounds spent .
Some Theory is about formulation, which is about physics. An engine will only make power, if you can get the gasses out of the cylinders quicker then you can fill them. The current trend to fit the biggest OD exhaust to a car, only slows the gas speed up and so robs the engine of power/torque.
If you do a search on here, there are a number of theories with proof to back it up that prove certain mods work and some do not. Read Guys Engine prep, and that gives you plenty of theory with flow bench results that count in the real world.
Incidentally, some of the drag and sprint cars in Greece and Cyprus are putting out outrageous power.
As for the Fiat 1.4 16v head, it cannot be gas flowed due to its inherent design. All you can do, is reprofile the inlet cam back edge, thats it.
sumplug wrote:
As for the Fiat 1.4 16v head, it cannot be gas flowed due to its inherent design. All you can do, is reprofile the inlet cam back edge, thats it.
Andy.
What do you mean by saying "cannot be gas flowed" ?
Konstantinos
P.S i think we have been distracted from our initial disgussion..
You need to see a head off the car. The hydraulic tappets cannot be altered or solid ones fitted. No other cams can be used. This head was built for a purpose and is not for tuning.
The limiting factor for the engine is block strength, pistons, flywheel weight, and induction and exhaust.
sumplug wrote:You need to see a head off the car. The hydraulic tappets cannot be altered or solid ones fitted. No other cams can be used. This head was built for a purpose and is not for tuning.
The limiting factor for the engine is block strength, pistons, flywheel weight, and induction and exhaust.
Andy.
Are you sure you know this engine???C&B for example has 2 pairs of cams..
Yes. these heads have been cut apart to investigate the ports, but due to the hydraulic tappets which are impossible to change, its just a waste of time, trust me. But you can still get 130+bhp out of one if these engines if the build is right using throttle bodies and forged pistons with after market management. But it isn't straight forward.
Way forward for this engine, is to use the 8V head on the 16V block.
