what are better spark plugs, for the money. denso bosch or ngk
and what is an ideal gap for them, if i get the bosch 4 i know i do not have to gap them, has anybody seen a real improvemnet with them, power, fuel mileage or a fireball resulting in the car being engulfed in flames.

 

Everyone seems to say that the NGK v-power copper plugs offer the best performance, much improved over stock. I have a set myself that I need to install soon. Copper should give better performance than platinum, but they don't last nearly as long. According to the NGK master catalog, the correct gap is .044. Also, I'm assuming you don't have a WRX; or else you wouldn't be in the N/A forum.

 

Most folks believe copper plugs are best for performance, they just need frequent changing. In a comuter type car, go with the Bosch platinums, you may never need to change them. I have NGK coppers ($1.19 at Kragen! w00t!) in the RS and Bosch platinum in my daily driver 280ZX.

 

do they impove milage?

 

Nah, not much you can do to improve mileage.

 

Spark plugs won't give you better GM unless your old ones were bad.

Myself I use copper NGK and change them very spring.


From here:

http://www.ngksparkplugs.com/techinf...200&country=US

Q: How much of a performance improvement can I expect from changing plugs?

A: A common misconception is that changing spark plugs will result in a large power increase. In most cases, removing even seriously worn out spark plugs will only result in very modest power gains, typically about 1-2% of total engine output. This could be even less for computer-controlled vehicles, primarily because most newer vehicles have more powerful ignition systems and the vehicle's computer can make adjustments so that vehicle operation seems smoother and more seamless.

Many people think that simply supplying more spark to the firing tip can and will combust more fuel. What they don't understand is that most newer cars' engines are so efficient that they are already burning all of the available fuel. Simply adding more spark voltage can't burn more fuel because there is no more fuel to burn.

When a stock or near-stock engine is given a fresh set of spark plugs, peak efficiency is restored. The power gains that come from this restored state of tune are usually minimal. Any company that tells you that their spark plug will provide significant gains in power in a stock or near-stock engine is making blanket statements that may not be supportable.

 

hey thanks, i was looking at the bosch so that is what i think i will go with then.

 

I was talking about standard Bosch Platinums, not the +4s. the +4s are a gimmick, but the single electrode platinums are awesome when you don't need every last ounce of performance. They last a LONG time on a not-so-powerful car, and the pre-gap is usually very good. I do still agree with Peaty, NGK coppers are the best for your Impreza, but your 'other' car will be well served with the BP's.