Tune / Spark Plug Info / Opinion

[Dmb408]

So I trust my indy shop a lot and the techs there so I asked the Porsche Audi guy that works on my Porsche and RS6 what he thought of Iridium plugs (the top NGK plug, one above our OEM's) for a tune up. Below is his response (my car has OCT ecu/tcu, and full Milltek fyi).

the tune for this vehicle, regardless of the company who offers it,
doesn't change the CFM of your engine. even if you increased the volume
of forced induction with a boost controller, IE increasing the boost,
the CFM of the combustion chamber doesn't change. this all has to do
with the combustion chamber temperature.

for example. even when we boost an NA engine, unless we change the
engine's combustion chamber, IE port and polishing, hemi chamber
upgrade, multi angle valve job, the temperature of that combustion
chamber will not change.

iridium spark plugs run a lot hotter and may not keep the combustion
chamber cool enough, causing misfires.

all the tune does is it changes the timing, duty cycles of the fuel
injectors, and changes the thresholds of the monitoring sensors and
senders. also with the RS6 you get different shift points for the
different throttle response.

if you wish to experiment with iridium plugs you can. it won't cause
any damage. I recommend sticking with the NGK platinums

Cheers

[marklar182]

for example. even when we boost an NA engine, unless we change the
engine's combustion chamber, IE port and polishing, hemi chamber
upgrade, multi angle valve job, the temperature of that combustion
chamber will not change.....UM NO, it absolutely will! more pressure=more heat!

iridium spark plugs run a lot hotter and may not keep the combustion
chamber cool enough, causing misfires. Not misfires, DETONATION! Totally different.

all the tune does is it changes the timing, duty cycles of the fuel
injectors, and changes the thresholds of the monitoring sensors and
senders. .....And the Boost Pressure via the N75 duty cycle!

also with the RS6 you get different shift points for the
different throttle response.... IF you get a TCU tune. Not with an ECU upgrade.

Factory 7 range platinum plugs PFR7Q seem to run fine with a tune. 8 range are not available, and probably too cold.

I run Copper plugs BKR7E, they run a tad cooler, are super cheap, but last ~5k miles. They also will sacrifice themselves if you happen to get detonation, potentially saving your motor. Platinums and Iridiums will not!

[Dmb408]

Your first point was one of the reasons I posted this because I thought back to the ideal gas law(s) and my chemistry days. But here is where I am going to show I don't know terribly much about the engineering of an engine, the turbo is pushing in denser air due to higher boost pressure but your cylinder volume remains the same, again just with desner air? And no tune touches compression ratio right? So does denser air really equal more pressure thus creating higher temp? You're simply allowing more of a combustion to happen within the chamber but is it necessairly at a higher chamber temp? No one jump all over me, just trying to learn, thanks.

[Dmb408]

I read this:
http://www.turbobygarrett.com/turbob...g_rich_vs_lean

Wouldn't the last sentence of first paragraph below imply that the tune trys to adjust the AFR to keep temperature constant?
The turbocharger increases the density of the air resulting in a denser mixture. The denser mixture raises the peak cylinder pressure, therefore increasing the probability of knock. As the AFR is leaned out, the temperature of the burning gases increases, which also increases the probability of knock. This is why it is imperative to run richer AFR on a boosted engine at full load. Doing so will reduce the likelihood of knock, and will also keep temperatures under control.
There are actually three ways to reduce the probability of knock at full load on a turbocharged engine: reduce boost, adjust the AFR to richer mixture, and retard ignition timing. These three parameters need to be optimized together to yield the highest reliable power.

[Brav]

Any time you compress a gas, you excite the molecules, and create heat. Opposite is also true.. take a room temperature compressed gas, and as it expands to atmosphere, it will absorb heat (and cool). This is why aerosol cans get cold when you spray them..

more boost = lots more heat. AKA the whole reason we have intercoolers..

[hahnmgh63]

If you compress the air, i.e. higher boost, then you do get denser air which means more air (Oxygen & Nitrogen) molecules into the cylinder which means more air. You do get a higher airflow through the Mass flow sensors with a tune, up to the maximum the MAF's read which is just over 364g/s I believe. The ECU in conjunction with the O2's, EGT's, MAP, & MAF sensors will adjust the fuel accordingly. All this is done within limits of the tune & the Bosch maps which are in the ECU. A tune just lay's down some baseline maps which the computer has some leeway to adjust a little bit either way. Different atmospheric conditions, pressure, temp, humidity, etc... will cause the need for the ECU to adjust the basic tune to keep everything within parameters.
To make a long story long, I'm not sure if your mechanic was just wrong or mispoke but you do change the CFM with a tune. Yes the area does not change but air is compressible so you do compress more air into the same space. And the extra air along with the proper ignition & fuel is what were all looking for to get more power. Raising the Boost of a Turbo car is like raising the compression ratio of a Normally aspirated car. But with a Turbo it is like having a variable compression ratio when needed and not fixed as in a Normally aspirated car.
As Brav said, more Boost equals more heat. Most of it from the extra air & fuel and only partially from the higher compression factor. And yes, a higher performance car with higher compression ration or Boost, all other things being basically equal will use close to the same or a colder plug. The Iridium plugs are available in Colder & Hotter designs, nothing to do with the Iridium itself.

[Chase]

Does CFM mean cubic feet per minute (air volume) in this discussion?

[Dmb408]

So then the Iridium's I was specifically asking about, four our cars, on NGK's site ( http://www.ngksparkplugs.com/part_fi...?engineid=1535 ) are in what Jeg's (just as an example) says is a "medium heat range"

Mark, did you mean 50,000 miles on the BKR copper plugs? Because those are our stock plugs, you must mean more than 5K

[Dmb408]

Sorry Mark, you might be right on stock plugs, i swear the bentley says the ones you run though, i'll look when i'm home

[marklar182]

PFR7Q Are stock Plugs.

BKR7E Are Copper plugs, and yes, 5000miles is about all you get! I have stretched to 10K. Copper plugs perform very well, but eat themselves, and the gap opens over time. (they are $2 each, and give me peace of mind)

IMO the PFR7Q work fine for 99% of us on a normal aftermarket tune.

[hahnmgh63]

Stock plugs are the NGK PFR7Q's, I did jump on the Iridium craze a couple of years ago and tried the ND BKR7EIX Iridium plugs and found no noticeable difference in performance. I actually think they started to fall off in performance quicker than the OEM NGK's so I swapped back at my next plug change. One thing to think about is your coils which have been discussed here in depth a few years ago. The stock 01E coils made by Hitachi, not the BERU seemed to be the big following with the Audi tt performance guys who have more experience with them than we do. A lot more tt's out there, and a lot of them with a lot more mileage than we do. The stock 225bhp 1.8t Audi tt uses the same part # coil that our BCY engine does. It seems that the coils can get weak after time before they fail and just throw a weak spark that may or may not throw and intermittent misfire code. Better to replace them at every other plug change while your there, their relatively cheap.

[Dmb408]

hahn and mark, I wasn't going crazy, I remembered to look at the Bentley service manual last night, BKR's is what it lists in the spark plug table for the BCY