stevebez

Ok so gone with the one step colder plugs and story goes it should reduce EGT by up to 100deg!

What I am wondering is why is this good? If EGT is lower is all the fuel bring burnt? Is it burning faster ?

Che?

e55amgrocket

the reason a colder plug will help reduce egt's is because i colder plug has a faster heat transfer to the tip and begins its cooling faster, the more power you add to an engine the higher the cylinder temp gets so by running a colder plug it lowers those temps and makes for better heat transfer accross the combustion chamber. Colder plugs are also much more likely to foul out than a hotter plug so always remember that.

shardul

iTrader: (1)

Detonation will actually cause EGTs to drop. This behavior has fooled a lot of people because they will watch the EGT and think that it is in a low enough range to be safe, the only reason it is low is because the engine is detonating.

The only way you know what is actually happening is to be very familiar with your specific engine EGT readings as calibrations and probe locations vary. If, for example, you normally run 1500 degrees at a given MAP setting and you suddenly see 1125 after picking up a fresh load of fuel you should be alert to possible or incipient detonation.

skratch77

What plugs do you run Shardul?My car is close to 60k and has original plugs and would running a colder plug help our top end at all?

bassn_07

Detonation is caused by excessive heat and/or pressure for the fuel being run. The excessive heat, if that is the case, can be caused by a lean condition. Or, the detonation can be caused by a fuel with too low an octane rating for the amount of heat and/or pressure in the combustion chamber. Low octane fuel burns hotter and has less ability to resist detonation. Octane is, after all, just a measure of a fuels ability to resist detonation.

I've found that the EGT is the best way to detect detonation. A fuel that is detonating will show lower EGT readings than one that is not.

IMO lower EGT's will always be better than hotter at WOT


A lot of modded guys here run NGK iridium LFR7AIX. A one step colder plug will only help your top end if you're detonating.

I would recommend going with new wires and one step colder plugs. I changed both at 50k and couldn't be happier. You track your car often and IMO worth the peace of mind.

BTW...Here's some FAQ's from NGK's website http://www.ngksparkplugs.com/tech_su...x.asp?mode=nml.

skratch77

Ill be going with those plugs on my next tune up for sure.

AgSilver

First and always remember: Gas is far cheaper than valves and pistons. That said, an AFM resulting in an EGT of 150F - 125F degrees below the peak EGT (peak EGT being measured on the rich side AFM) will provide your best power. Be careful! Whomever does the mapping really needs to know what they are doing and have the proper equipment. I am only familiar with it being done on an engine dyno. One mistake (or a bad injector) and you can do some serious damage in a hurry.

A further comment about EGT's: As the AFM is leaned, EGT's will rise to a point and then flatten out and with continued leaning of the AFM the EGT's will decrease - - - this is not where you want to be as it is the prelude to catastrophe.

NGK plugs, to the best of my knowledge, still have the widest operating heat range and came standard in the E55 (not Bosch as in most MB's). Unless you are seeing signs of overheating on the plugs I would stay with the standard heat range.

shardul

iTrader: (1)

Alex i think you are referring to pre-ignition, i maybe wrong

shardul

iTrader: (1)

NGK step colder plugs in heat range 7. I think stock are in the 6 heat range

stevebez

So the answer to the Question "why are lower EGT's better?" is not very clear then???