Has anyone heard of irridium plugs improving HP. I currently went to a tunner shop who recommended a set that he claimed would add up to 7hp at the wheels. While I don't belive this is it possble to get any power from iridium plugs in our car.

 

The plugs in the Crossfire are sufficient. You might get a more intense spark from an irridium tipped plug resulting in a more complete burn, but 7rwhp seems like quite a stretch. I'd have to say that purchasing a set of these would just be a waste of money.

 

Sounds like a load to me. The Crossfire engine uses 2 plugs per cylinder as it is, I don't see how Iridium would help. I wouldn't be surprised if they were Iridium plugs to begin with.

 

I work for the world's largest automotive parts manufacturer, we've been making spark plugs for over 100 years. Yep, the founder of my company invented them. (Arthur Champion, AC spark plugs-AC Delco-Delco electronics-Delphi)

You won't notice the minute amount of horsepower gained from a spark plug,
and that gain is only if you were running fouled plugs to begin with.
Better starts, better fuel economy, smoother idle... sure!
7HP? Ask to see a dyno sheet. Not just the company's ad.

 

It sounded like a load

 

That reminds me! I was amazed when I first found the two plugs per cylinder set-up.
Can any knowledgeable dude out there explain the purpose of the two plugs (emphasis on "knowledgeable").
Sure to be some real advantage and purpose because it would be more costly to do this. It isn't somebody at Mercedes with a fantasy idea, I hope??

 

The two plugs per cylinder idea has been around for years and years...since the 1920's, I believe. The design was more commonly found on the European cars (Alfa Romeo liked to do this a lot), but found its way into the American lineup as well.

The idea behind it is that with twice the spark you'll get a quicker, more complete burn. Whether or not it produces more power is questionable, but you do get an increased throttle response. Additionally it aides in increasing fuel economy and reducing emissions.

Is it really necessary? Probably not. But we're talking Mercedes here and why charge for 6 plugs when you can charge for 12 instead?

 

Thanks TSaxMan, that makes some kind of sense. If the customer is going to pay upscale prices for luxury Mercedes, this added cost wouldn't matter. I would think the explanation of a more complete burn has merit if the plugs are strategically placed relative to the cylinder design. Not being familiar with the structure of the engine, I can only assume they got it right on that one.

 

You're welcome. I know some thought goes into the placement of the plugs, but I am unaware of the specifics.

 

I was really into the import scene 4 or 5 years back when Iridiums were first introduced on the market. A lot of people fell into the hype at the time, but I did read a bunch of reports on them that said they dont really do a thing. I'd stick with platinums which I am betting the xfire already comes with.

 

Check out the Alfa Romeo TwinSpark concept. They reckon they get the same power from a 2 valve per cylinder engine with twin plugs as other manufacturers with 4 valves per cylinder and a single plug.

Since I did Chem Eng for my degree, if the twin plugs are correctly timed you would expect more of the fuel to combust in the mixture. If your valves are smaller, then you lose out on the volumetric flow of fluids into and out of the engine. It is the overall package characteristics which you need to maximise together.

The best combination will depend on many factors which are not easy to vary. The timing of the camshaft(s) and their lifting characteristics etc all play a critical part.

One thing is certain - the XF engine with twin plugs will burn the air/fuel mix better than an XF engine with a single plug providing the plugs spark together.

 

Twin plugs make for a better burn and initial flame propegation across the top of the piston. It is especially functional on short stroke, large bore engines where an single plug on a multi-valve engine will have trouble with flame speed. Been used in Ferraris, Aston Martin DB4 GT and many others. In the modern era, it helps emmisions and keeps the converter in better shape by not dumping unburnt fuel out the exhaust valves.