Anyone Tuned An FI Setup To 12.5 AFR WOT?

I need an opinion or example if I can get it.

We have a 2005 Silverado Z71 RCSB Radix Blown L33 5.3 tuned to 12.5 WOT. We are getting some flack on it supposedly being too lean.

The only mods are the blower,Corsa Catback, and a CAI.

It has 42# injectors and a 8.1 marine fuel pump. 5.4 pulley.

At WOT:
Boost is "6.9-7" psi.
Spark is "18.3".
Knock retard shows "0" at all times.

Pics of factory iridium plugs @45k miles. Three back to back WOT runs were made and gently driven 1/4 mile to the garage to remove them.

Some fear it's too lean and bound for injury. Your opinions please.

http://alcphoto.net/radix/12.5_plugs.jpg

Do you have more pics (especially a 45° view close up of the tip)...?

Other comment: what is that gap, looks too big...?

Will get more pics. Gap is .040.

Thanks

Other comment (and I'm no expert): my understanding is that for boost an AFR in the low-mid 11's is recommended.

12.5 is suitable for NA, but is not sufficient for FI.

The reason is that the extra fuel keeps the combustion temperature safe... but your plugs seem to show no signs of elevated temps nor detonation.

Interesting topic.....

Motors NA motors don't melty down at 14.7 AFR at WOT they just don't make any power. Look at pickup trucks that don't allow PE for 120 seconds plus under WOT.....

Now, FI motors like a richer mixture for the cooling effect a richer mixture provides. This doesn't mean you will make more power. The more power a car makes (higher boost pressures or higher cylinder pressure events) do require richer mixtures to help against knock limits. You take a stock Ford 2V 4.6L with 7 psig and they don't make any power in the low to mid elevens as its just too much cooling for the cylinder event. We run those at 12.0-12.2 all day long.

If you have a real efficient combustion chamber the motor will respond better to a leaner mixture. Of course this is a fine combination with spark advance as well (not to mention fuel types).

It also depends where in the boost curve that peak cylinder filling (highest VE) is taking place. I might run 12.5 off the bottom, bring it to 11.5-11.6 at peak torque and then lean out to 12.0 to redline in some applications.

Run a LSX motor at 12.5 and you won't kill it (unless you have serious knock) but power could be flat.....every combo is different.

Howard

OK, Thanks,
I tell you its all french to me being why I'm asking. I will say the L33 has the LS6 heads originally developed for earlier model Z06 motors and I hope it helps here.

Its just that my tune shop asked for the vehicle to be dropped off overnight so they could get into it without me pacing around and upon pickup announced what they did and I am in no place to argue because I only know what I hear so I drove off.

The darned thing runs better than it ever has and not a hint of detonation, and believe me I have been looking of it.

Looking at my plugs and numbers would you guys continue driving this truck as is?

What heat range are the plugs? Stock? Switch to a colder plug if so. At least one heat range, maybe two.

You'll get a lot more life out of the plug, and the motor will run proper.

When I build my motor, I'm thinking of using an NGK TR6 plug. They offer several specific heat ranges. I know the Supra guys run the NGK TR6 and specifically two heat ranges colder than stock when going above 6-700 horsepower.

I'm not sure if 12.5 is too lean. I think the EGT will tell the story there. Fuel cools.

The Supra guys (again), normally tune to 11.5. Pentroof style combustion chamber, and 4 valve heads. Most are 500-800 horsepower at the crank I'd say.

How is the power on 18 degrees of timing? A rocketship? Switch those plugs colder and watch power climb dramatically if the plugs are too hot.

So I guess 12.5 right now is not something to panic about?

The plugs are the stockers.

Here is a LINK to my dyno chart when the WOT AFR was 11.1 a few weeks ago. The chart reflects Stock, Magnuson Supplied SuperChips Tune & 3.5" pulley, and the 11.1 with a 3.4" pulley.

Something happened to the tune (long story) and it lost its mind timing wise, detonated, went to 10.5 WOT AFR. This is why she went in this time.

Now it runs better than it ever has in the summers past.

Quote:

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Originally Posted by Redline Motorsports

Interesting topic.....

Motors NA motors don't melty down at 14.7 AFR at WOT they just don't make any power. Look at pickup trucks that don't allow PE for 120 seconds plus under WOT.....

Now, FI motors like a richer mixture for the cooling effect a richer mixture provides. This doesn't mean you will make more power. The more power a car makes (higher boost pressures or higher cylinder pressure events) do require richer mixtures to help against knock limits. You take a stock Ford 2V 4.6L with 7 psig and they don't make any power in the low to mid elevens as its just too much cooling for the cylinder event. We run those at 12.0-12.2 all day long.

If you have a real efficient combustion chamber the motor will respond better to a leaner mixture. Of course this is a fine combination with spark advance as well (not to mention fuel types).

It also depends where in the boost curve that peak cylinder filling (highest VE) is taking place. I might run 12.5 off the bottom, bring it to 11.5-11.6 at peak torque and then lean out to 12.0 to redline in some applications.

Run a LSX motor at 12.5 and you won't kill it (unless you have serious knock) but power could be flat.....every combo is different.

Howard

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very Interesting topic.

btw. nice write up howard ...

I may try and get my tuner to bring it down a bit I guess. It just touches 12.5 a couple times on the way up and is a little richer at the top between 12.2 & 11.8 breifely but will blink a 12.5 there. Never any leaner.

I notice in the cooler mornings it will do 11.8 @ WOT pretty steadily.

If you guys were to go in and richen the tune would you mess with timing or just touch the AFR max?
I ask because I'm about to get EFILive and being a total noob I may post my tune and get you folks to look at it and help me adjust it? Is that a normal thing here?

Will it richen on it's own in the winter?

One more, Has anyone done comparisons on the PLX wide band AFR systems to Dyno AFR wide bands? Just wondering if perhaps they are known to under or over rate the mixtures by nature.

Thanks Guys