Mods, A/F Ratios, and what to do...?

[Bravnik]

9:1 is way too rich, by the way.

My car with 18PSI, Test Pipe, CAI, BCD still dips into the mid 9's at WOT. Stock MS3's break into the 8's as I have witnessed at a Dyno day here in CA the other day. The MS3 runs pig rich. This is good and bad. Bad for gas but good for future modding as we have a TON of room to work with

 

[Bravnik]

LOL I posted a reply and my reply posted at the top of this thread - WTF?

 

[AutoXRacer]

I finally got some data logging off my MS3 and I've noticed my A/F ratios dip in the 10s and occasionally in the 9s.

My first question is ideal A/F ratios...?
11s...? At which point does it become critical; 10s, 9s...? Am I causing damage to the engine dipping this low...?

My current breathing mods are a MS CAI and a CP-E catted DP. I'm planning to install my ETS 3.25 TMIC this weekend and I'm assuming thats just going to worsen the problem...?

Will installing a high-flow fuel pump resolve this issue? Laloosh, Haltech, Driver311, any others...?

Thanks for the help!! (2thumbs)

 

[Sacrilicious]

i have no experience in this, but i don't think running rich like that would damage the engine. the reason it runs rich is to protect your engine from getting cooked to a crisp. the leaner you run, the hotter it's going to be there, and since we're using force induction, they have to step back on the AFR in order to maintain reasonable operating temps.

the only problem you really have to worry about is maintaining the rich AFR as your revs go up. if your fuel pump can't keep up, you're going to be toast.

 

[SuperStretch18]

Higher numbers are more of a concern in terms of detonation and actually blowing up the engine. xx:1 refers to the proportion of air:fuel. More air means less gas in the mix, means more lean, means more volatile mix that burns at higher temps. People are blowing engines when they go higher than about 11.5:1 (someone else may be able to correct me with the actual number)...

 

[Mid_Life_Crisis]

Very odd. I haven't seen anybody post a ratio as rich as 9:1 yet.
I would expect that if there was any change due to the mods you have, the mix would have gotten leaner, not richer.

 

[AutoXRacer]

I thought 10:1, 9:1 were lean numbers and 11:1, 12:1, etc were richer...?
(huh) can anyone clear me up here...?

There are a few accelerations I did on the highway. I couldn't get a clean single run do to traffic and roads not being available at the time. In a one or two of those plots I hit 9s...

I graphed RPM, Vac/Boost, A/F Ratio, and Fuel Pressure. Did I need anything else?

I am planning to do a clean 1-4th gear run asap...

See what you guys can decipher from all this... Do I have something to worry about? I need/want to learn this stuff; its pretty interesting... (2thumbs)

Please bare with me, it was my first time data logging with the DashHawk.
I'm still unfamiliar with the unit and all its settings.

Thanks for the help guys!!! (2thumbs)

 

[Sacrilicious]

the "lower" the number, the richer it is. it's Air/Fuel ratio, so the more air there is in the mixture, the higher the number will be.

 

[Sacrilicious]

the shape of your AFR curves look pretty reasonable. it begins to run richer when you boost, so that's a good thing. as for the exact numbers you see there, i really have 0 qualifications to tell you about their validity.

 

[AutoXRacer]

the "lower" the number, the richer it is. it's Air/Fuel ratio, so the more air there is in the mixture, the higher the number will be.

So then I have no issues...? If I'm hitting 10:1s and 9:1s then I'm good...
So why is 14.7:1 ideal...? So anything above 14.7...15:1, 16:1, etc is lean...?

Damn, I had this whole thing backwards.

Now that you mention it, I have seen my A/F dip in the 15:1 during idle...

OK so, during WOT, what is a bad A/F Ratio is you were setting up a warning alarm...? There has to be a bad range, yet safe to wear your engine is not going to blow up...

Thanks again guys... Obviously, there is a lot to learn... (crazy)

 

[Mid_Life_Crisis]

I thought 10:1, 9:1 were lean numbers and 11:1, 12:1, etc were richer...?
(huh) can anyone clear me up here...?

SuperStretch already answered this, but here goes.
In an air/fuel mix, there is a lot more air than fuel. In a theoretically perfect mix (in a laboratory where every last bit of fuel and air get burned) it is about 14 parts air to 1 part gasoline, or 14:1.
Rich or lean is in reference to how much fuel (gasoline) there is in relation to the "perfect" mix. A lower first number (12:1 as compared to 14:1) means less air to the one part of fuel, so it is a richer mix. A higher first number is more air to the one part of fuel, so it is leaner.
Extra unburned fuel actually has a cooling effect in the cylinder, so we want it a little rich. Too lean and the engine runs hot and starts to experience knocking, which if left uncontrolled is a death knell for any engine, but especially a turbocharged one.

I hope that helped.

EDIT: Damn! Three posts while I was typing...

 

[happy and angry]

My first question is ideal A/F ratios...?
11s...? At which point does it become critical; 10s, 9s...? Am I causing damage to the engine dipping this low...?

The thing with this question is there isn't one single ideal A/F ratio (although people will argue that there is). You'll see slight variations in our car, tending towards running rich rather than lean, through each gear and the range of RPM.

The problem is this: the heat, power and fuel economy needs changed based on use, and the time available to burn your charge changes as you accelerate (more time to manage combustion at 1,000 rpm than at 6,000 rpm, for example). At each gear, at different loads, during different points in the RPM range, a different A/F ratio will better meet the needs of the motor in terms of these competing needs. We run rich as a rule to keep things a bit cooler, but that's not the ideal mix for power. It keeps temperatures down, however, which is good for engine wear and tear. It really does depend on what you want.

 

[AutoXRacer]

Wow, that really clears up things... I was familiar with the whole rich and lean conditions and what happens to engines, but I was reading the A/F ratios backwards...(encourage

OK, so I'm in the clear then... Hewww, I was sweating there for a moment.

(2thumbs) Great!!! Now I can install the TMIC with no worries!!! (2thumbs)


(freak) Sorry for being such a retard...(stooges)

 

[Mid_Life_Crisis]

So then I have no issues...? If I'm hitting 10:1s and 9:1s then I'm good...
So why is 14.7:1 ideal...? So anything above 14.7...15:1, 16:1, etc is lean...?

It isn't ideal in a car. In a lab it is theoretically perfect, but it doesn't work well in real life.
You'll see huge numbers of posts here discussing how to lean the mix a little. This is in relation to the stock settings, not the theoretical ideal. The car seems to hit about 10.5:1 or so stock. We want it leaner than this (11.5:1) because while a little extra fuel is a good thing, you get to the "point of diminishing return" where you add so much extra that you are just wasting fuel and the mix is so rich that it doesn't burn properly, which robs us of horsepower.
The extremely rich factory setting is a safety level so if something happens to unintentionally lean the mix, it won't go too lean and blow something up.
Most of us would be willing to live without that safety net to get a little more efficiency and power from our cars. 9:1 is way too rich, by the way.

 

[Sacrilicious]

The thing with this question is there isn't one single ideal A/F ratio (although people will argue that there is). You'll see slight variations in our car, tending towards running rich rather than lean, through each gear and the range of RPM.

The problem is this: the heat, power and fuel economy needs changed based on use, and the time available to burn your charge changes as you accelerate (more time to manage combustion at 1,000 rpm than at 6,000 rpm, for example). At each gear, at different loads, during different points in the RPM range, a different A/F ratio will better meet the needs of the motor in terms of these competing needs. We run rich as a rule to keep things a bit cooler, but that's not the ideal mix for power. It keeps temperatures down, however, which is good for engine wear and tear. It really does depend on what you want.

+1

you really need to study up to figure out exactly what you should shoot for when it comes to this kinda thing...+_+;

 

[happy and angry]

So then I have no issues...? If I'm hitting 10:1s and 9:1s then I'm good...
So why is 14.7:1 ideal...? So anything above 14.7...15:1, 16:1, etc is lean...?

Damn, I had this whole thing backwards.

Now that you mention it, I have seen my A/F dip in the 15:1 during idle...

OK so, during WOT, what is a bad A/F Ratio is you were setting up a warning alarm...? There has to be a bad range, yet safe to wear your engine is not going to blow up...

Thanks again guys... Obviously, there is a lot to learn... (crazy)

There are no clearcut answers for you. The last 100 years of combustion engine development has been in large part about figuring out the ideal A/F ratios at different engine speeds and loads. I don't suggest playing around with your A/F too much, and if you do, be careful. Mazda has a team of engineers using incredibly expensive computer sims modeling engine performance to figure out A/F ratios, and there is an incredibly complex real-time computer adjusting A/F on the fly based on fairly complex parameters to make sure your engine runs well and safely. If you're on here asking questions like this, I can only guess you want to play with A/F ratios. I'm not sure you really should. Honestly, changing the ratio a 1 or 2 tenths one way or the other could mean the difference between running a bit rich and suddenly running too hot and hitting detonation.

Read:

http://en.wikipedia.org/wiki/A/f_ratio

http://en.wikipedia.org/wiki/Engine_knocking

Good starters, some resources linked at the bottom. Follow up on your own questions and make sure you understand what you're doing before you play around.

 

[Mid_Life_Crisis]

make sure you understand what you're doing before you play around.

+100000000000000000 keep adding zeroes. This cannot be overstressed.

 

[AutoXRacer]

I'm not planning on adjusting A/Fs or anything like that.
I've been modding the car (breathing mods) and right up until last Friday I had no clue what my boost or my A/Fs were...

So over the weekend I tracked my boost and A/Fs and noticed my A/Fs were a solid 10:1 with occasional dips into the 9:1s... And my boost spikes occasionally into the 19-20s...

I though the lower the number, the leaner the condition; so I started to get worried.
But you guys cleared that up for me!!! (2thumbs)

No worries here... I'm definitely not changing anything in the tuning. All I'm doing is bolt-ons... I'll leave the tuning to the ECU; I'll just keep an eye on it... (lol2)

Thanks guys!!! (thumb)