Just about all of my knowledge of a/f ratios was learned from working on my Mustang. It has a Vortech, and keeping the a/f ratios "good" is very important, especially to maintaining the health of the head gaskets. At times, I have been very close to buying a wide-band O2 meter, but the $1,000 price tag is the problem.

When I see guys on here doing things like changing pullies without a chip, I would think that you could have some serious problems.

I'm guessing the only thing that is saving most of them is that the a/f ratio at WOT on the L is really, really rich, and when bumping the boost, it doesn't lean out enough to cause a problem.

Or, the computer is able to compensate for the added boost, and adds more fuel? This is the part I don't know. I do know that on the Fox Mustangs, the computer is not capable of this.

BTW, it's not sufficient to just try to listen for detonation. You could have it, but not be able to hear it.

What do we know about this topic on the L? Certainly the tuners should have some info.

 

There are boost pressure sensative fuel pressure regulators on these trucks. Every additional pound of boost yields one additional pound of fuel pressure. Raise the boost 3psi, you get 3psi additonal fuel pressure. Evidently, it's close enough not to worry about. Think about it, there can be a 2psi difference in boost in the summer time versus the winter time and the stock program handles this quite safely. The stock program is VERY RICH, just look at your exhaust tips.

 

My Mustang also has a boost sensitive pressure regulator, and it's not enough.

What I'm kind of getting at is that it seems that we don't have very much a/f ratio data. Looking at plugs, and listening for detonation is good, but it's far from telling the whole story. Without a wide band, we just don't know very much.

 

I agree with Topsy. I know the stock program on the Ls is very rich. I am guessing that most of the power increase for the aftermarket chips come from a leaner A/F ratio. You should also see a slight increase in MPG. It kinda sucks that my truck only gets 12-12.5 MPG, and a leaner AFR would not only reward me with more power, but also better MPG. Since I have decided to wait until the warranty is gone before getting a chip, I guess I am stuck with the rich program.

I have some experience with 5.0s and a '97 Cobra. There are mods you can make to the AIT sensors and MAF, some without costing any $$, that will allow you to tweak your A/F ratio. Does anyone know of any tricks that can be done to the Ls without getting a warranty-voiding chip?

 

I've kind of been wondering this as well. I haven't even seen this mentioned yet. I've got a Kirban 'boost senstive' FPR as well, but I make sure the a/f is 12.5:1 or less before I beat on the car. I wonder what a stock L's a/f is from the factory?

 

'01L:

Your a/f ratio at cruise (gauge showing vacuum, no boost) I'm assuming will be much leaner. Has to be to pass emissions.

The a/f ratio I'm concerned about is at WOT.

 

topsy,
Oh, ok...

My truck never sees WOT

 

Just my opinion, but having had a number a reburns in the past for detonation issues (that I could hear...) I believe the only true way of making sure that you're safe on the A/F is to have a custom tune peformed for your individual truck. The off-the-shelf chip programs may or may not be safe for your truck. Who has blown a motor after having a custom tune done?

 

I agree DB, that sounds the best way to go.

Since I don't live near any of the tuners, I'll have to mail order, dyno with a wide-band, and get a reburn if necessary.

 

A custom tune job won't help your engine if you're making too much HP.

 

Please expand upon what you are saying?

If you are referring to breaking a rod or something like that, then sure, you are right.

But you obviously can also do some real damage with a bad tune.

Anyway, if anyone has some a/f numbers, that would be great.

 

True. I would think that the internals would need to be upgraded in addition to a good tune if you are pushing a lot of additional hp via a big pulley or a bottle...that's the million dollar question, how many additional hp/tq can the stock motor take reliably? I guess that's a question best answered by the individual L owner and their tolerance for risk.

 

I having been thinking about this issue alot recently. So I think that I'm going to buy the Nordskog a/f guage. Its part # is NRD-D70141B for the white faced and is sold in Summit for $140. I like it alot better than the autometer b/c it has actual numbers instead of just lights. The dyno I go to also has a wideband sensor but I dont go after every mod, so I think that this guage would be a much better way to keep up w/ it.

 

That guage won't help very much, because the sensors are not wide band.

 

Oh, I guess I wont be getting it then. Thanks