So I took my Z in my sig out last night (first time in 19 months). I made sure it got an oil change, new gas, and had been running properly before opening it up.

When I did open it up I made sure my meth injection was working, and I paid close attention to the wideband AFR gauge to make sure I wasn't running lean.

I believe it was tuned to have around 11.5 on the AFR at WOT. And for the most part that it where it was. However, there were times it dipped down to 11.1 and I saw it hit 10.9 once momentarily.

What is the ideal AFR? At what point would it be dangerously lean where I would need to get out of the throttle?

 

Your dips to 10.9 shows that you're going richer, not leaner.

 

The 11.5 to 11.8 ballpark is about ideal when under boost at WOT. Over 12 is getting a bit lean and doesn't really net anything. Keep in mind that the displayed AFR is an average reading of the cylinders. If for example if you have a 10% variance among cylinders, one or more might actually be running dangerously lean.

Also your vehicle should be tuned to safely run max boost without methanol. Using methanol for 'extra fuel' is very dangerous and a bad idea. It should only be used for its air charge cooling properties, higher octane, and richer overall AFR. In the event that your methanol system should fail or run out, you don't want to run lean.

 

Yeah, I did state that wrong.

It's a matter of opinion. I see how it can be viewed as "un-safe", but I don't necissarily see it that way. Tuning it on the meth means more boost, more timing, and more power. It seems wastefull not to have it tuned on meth. Not to mention I don't see how having it tuned off meth, and then adding meth would be any kind of efficient. It would seem it would run rich as all getup without having it tuned on it.

There are fail-safe's that people never seem to take into consideration. Snow Performance offers a "safe injection" that bleeds off boost in the event that the pump isn't working. Not to mention I have a bright green light whenever the meth pump kicks on to let me know I am safe, and the obvious wideband 02 right in front of me. I suppose if all that were to fail at once, and I was dumb enough to stay in WOT, then I deserve to have it run lean and blow up.

 

lol, well said.

 

When I'm in boost I don't want to be looking at a gauge

Just remember that stoich is lower for meth - so if you are using it for additional fuel you need to figure how much is done by meth and that will lower your target. If you are 12.0 on a bunch of meth you are possibly lean - 10.9 may be spot on depending on how much meth.

You can usually go leaner on the wideband with meth - just remember it skews the numbers a little bit.

 

Like jsetzer said, do you really want to be looking at gauges and lights and such when yer on the street in full boost and a car pulls out in front of you, like that never happens in south florida. And I can tell you from exp., it doesnt always take long to do damage when u run lean. The pump, a fuse, clogged nozzle, damaged feed line, etc could happen an in the blink of an eye could cause damage through detonation because you were tuned spot on with the meth and it went lean w/o it. Its better to be spot on w/o the meth as the meth isn't really adding much fuel and like stated, a 10.5 AF with meth isnt really 10.5:1, so its not like it would be pig rich, and unless yer racing for money, would you really want to chance a moments mishap and destroy an engine?

 

Like I said it is a matter of opinion. Do I look at the guage every time I am at WOT in the boost? No. Who would want to do that? Do I feel confident that I am safe running on a tune with meth? Absolutely.

Theres more than just the gauge (as already stated). The gauge is there simply to let you know where you are at if you are looking. Its a great way to verify things are where they should be. I don't rely on that alone to keep me safe. The bright green light that comes on only when the meth is flowing how it should lets me know I can stay in the gas. That light is in clear periphial view. I can look at the road, my tach, whatever I am used to looking at while driving WOT and I can still see when it is on and I am safe to stay in the gas. Still not enough? Thats were Snow Perfromance's safe injection comes in and will bleed off boost in the event the pump doesn't come on to keep you safe should you decide to stay in WOT. These safety measures, along with good maintenance both in the meth injection system, and the car in general will keep you running safe.

If you don't feel like you are safe running with a meth injection tune, then don't. You can always spend the big bucks and run race gas instead. Or if its still a concern you might break something you can always stay N/A. Or if you are still worried, leave it stock. Still concerned? Trade it in for a Honda. Still not enough? Try walking... I think you get my idea.

Everyone is different on thier risk assessment when it comes to their car. I don't mind mentioning that my Z in my sig cost me over many years (more than a decade) $60,000+. There is no way I would drive it and go WOT if I had a concern that I might blow the engine. I feel over confident I took the right safety precautions when I had the engine built, added the supporting mods including the meth injection kit, and had it tuned. It has been through countless WOT runs for years all while just grinning asking for more.

 

I think you missed the rest of what I said, so this is the last time I will say it. Meth does not have the same stoich as gas. I could care less if your run meth or not, but tune it for what your run. If your wideband is calibrated for a gas stoich of 14.7, then 11.5 may not be ideal when on meth. 10.9 may still be ok depending on the amount of meth. I can't read minds to know how much of your fueling is meth.

- Lack of sleep here -

 

The car was tuned at 11.5 AFR with the meth. 10.9 would be more rich, and it only happens momentarily as I have a progressive system that adds more meth as the boost increases. It later leans back out to the tuned 11.5

In other words, it is safe where it is.

 

Just saying be careful because your readings are skewed... 11.5 may be safe just figure how much is meth if that is the way you tune it. Sorry if I came off like a ***** - I work at a local news station and it has been 36 hours of weather now. Damn tornadoes.

 

My readings are from my wideband 02. Which as the car was tuned was spot on with the AFR the tuner used as well. Not sure if you are familiar with Bryan Herter from PCM's for less or not, but IMO he is the best tuner available in the world for FI LT1's (and other applications as well). The tune was put on the safe side, and my internals are way above and beyond what most would do for a bullet proof build, and I have multiple fail-safe's already mentioned numerous times. It is probably the safest setup one can have using what FI, meth, and engine setup I have.

Could it still blow up? Anything can. But it is safe as can be made.

 

Confessions of a meth addict:

I was (I think anyway) one of the first to jump on the meth bandwagon years ago. Julio at Alkycontrol put together a kit for me back in 02. I have a non intercooled kit first with an S trim then a T trim and a single HP Racetronix fuel pump kit. The meth was used as a chemical intercooler that became a fuel supliment over time.

Towards the end of this last motors life I was drasticaly taking out fuel and tuning for 11.5 which always worked for me. I have had LT1 edit since 2000 and use a wideband and logging. 11.5 works. With a maxed out S, then T the dual nozzle kit had a hard time keeoing IATs in check.

There have been a few times it went lean--alternator gave out right in the middle of a WOT tuning session on the hiway and voltage dropped off the charts but the motor survived. It is (was) a cheap Scat cast crank, Eagle SIR rods and SRP pistons. It went 8 years with those internals and they didn't owe me a thing. Some hate these parts, I would do it again if staying under 11psi.

Anyway, failures do happen. In my case it happened twice. Both times the vacuum line that goes from the intake to the MAP sensor (which activates the system) popped off. Even when I zip tied them tight. The motor survived the first time but not the second. I've got the lights etc but when banging gears at the track my eyes are pointed straight ahead.

IMO 11.5 is the way to go. It cools the charge and acts like race gas. Sure it can fail, so can an alternator of fuel pump or oli pump or whatever.

 

How does the alky kit bleed off boost if the pump doesnt run? Ive never seen/heard of this and id like to know more.

Secondly, does your little light tell you that power has been applied to the pump, or is it the setup that lights up if the pump isnt drawing the current? Because a light that tells you the wire is hot wont tell you the pump isnt pumping. Thats my biggest fear with the meth, and I have good reason since I had a meth line meltdown failure and it took out my head gaskets as a result of detonation.

 

You can get a device that actually plugs into the feed line and detects flow.

They can be pretty safe. I'm shopping them now. Can't make up my mind - either run corn or do meth.