I've searched and searched for Y2Kev's AFC "How2" thread, and can't find it. I found a thread that refers to it, but doesn't link it.

Basically, I'm trying to figure out if a SC'ed Max with a 3.25" Pulley is rich or lean at low end, and if i should be richening up with the AFC at 1000-3000 RPM or not.

I will be Dynoing in a week or two, but I'm also trying to figure out how they measure your A/F at low RPM with an Auto - are the numbers skewed like they are with power and tq for 1st and 2nd gear, or are they accurate?

If they are, should I tune it like so, looking at what my O2 wideband said from my last Dyno?

<Numbers are from last Dyno, richen = raise airflow on AFC, lean means lean airflow (+/- xx% on AFC)>

1000 - 14.79:1 - richen +17%
2000 - 13.85:1 - richen +10%
3000 - 14.12:1 - richen +12%
4000 - 13.37:1 - richen +6%
4500 - 12.21:1 - lean -4%
5000 - 12.35:1 - lean -2%
5500 - 12.50:1 - stay
6000 - 12.72:1 - richen +1%
6500 - 13.05:1 - richen +4%

The fuel ramp was tuned previously with a Cartech Adjustable FMU, but that only works under boost (which is why after I start boosting the curve looks much better)



If you want to look at the A/F Map, see:

http://66.235.8.219/dyno/airfuel1.jpg

Also, you can download the original Dyno and map it to the Dynojet software.

http://66.235.8.219/dyno/DYNORUN.026

Thanks!!

IanS

 

Wow, that's a nasty-looking A/F curve! Instead of using the "canned" rpm points of 2/3/4/5000/etc, I would set your rpm points to match exactly the nastiest peaks+valleys from your curve. That will allow you to precisely adjust your A/F at those rpms where it is needed the most. Otherwise, the S-AFC's averaging algorithm will simply take the average adjust value between two rpm points and you won't be able to precisely tune those peaks/valleys.

For example, I would choose rpms
1300
2800
3300
4200
4600 and
6400
(I think you get to choose 6 points, right?)

2800 is a nasty peak. You can richen that to where you want it. Between 1300 and 2800, the S-AFC will linearly adjust between those two values. At 3300 you will also set your adjustment value. Between 2800 and 3300 the S-AFC will linearly adjust between those two values. And so on and so forth. Since you can't specify your adjustments at every rpm but instead only have a limited # of rpm points you can specify, you'll get the most flexibility by setting your S-AFC this way.

 

I htink you can only set it in 500 RPM increments - I will check that when I get home.

My other quesiton is whether or not The graph is accurate, and what gears it is accurate in.

Since I'm Auto, I can't just pick a gear to tune.....therefore, I assume the RPM curve is an average of all 3 gears.

Anyone have insight into how this works on the Dyno with A/F? Am I looking at it right?

Thanks!
IanS

 

Adjustments can only be made in 500 increments. How in the world did you get A/F readings for 1000, 2000, and 3000 since your car is auto? It will downshift when you mash the pedal under 3k.

The only correct way to adjust the % is by dynoing. I've gone as much as leaning out over 20% at certain points (-17% was the lowest with the 2.87").

Also keep this in mind when dynoing... 12.5 may not give you the most hp. Try going richer because you may gain torque and/or hp.

Good luck.

 

I already tuned on the Cartech FMU, and I haven't changed it since - theoretically, what is in the picture above is exactly what I am now.

Is there another way besides above to measure the low end A/F on a Dyno? i'm going off Dyno graphs with the numbers above - how will more Dynoing help me? I have the numbers already.

I was planning to go off of that, but I can't figure out how to read the low RPM A/F!!!

I mean, I will still take it to the Dyno, but I don't see how it's going to help anymore than the Dyno files i already have will, unless they use some other Dynoing technique for tuning fuel I haven't heard of.

IanS

 

I still don't understand how you got readings for 1000-3000 in an auto unless you dynoed in 1st gear. How will dynoing help you? Let me ask you this... how do you know you can't eek out a few more hp's with precise tuning? The CarTech can't let you adjust A/F at, for example, 4000 like how the AFC can.


Low RPM in an auto isn't accurate since going WOT will just make the car downshift. Just tune from 3000 to 6500.


What's not going to help? Tuning with the AFC?

 

Nono - I have already Dynoed and read my A/F readings, and haven't changed any settings since. Therefor, I should be able to use my old Dyno A/F mapping to change my setting accordingly, and then go to the Dyno and be much closer to perfect than I am now, thereby spending less time tuning and saving $$$.

I thought only hp/tq were inaccurate in 1st/2nd gear, not A/F mixture - which would mean my averages on my graph from my last dyno would be correct for 1000 RPM.....doesn't matter what gear I was in at 1000 RPM, correct?

The Dyno Graph above was done from 1st to 3rd gear - to get power and tq readings correctly, I just only look at 4000+ RPMs.

But IF A/F doesn't matter what gear I'm in, the 1000-2000RPM should be a reading from 1st gear, since at WOT, I only hit 1000-2000 in 1st gear.....so once again, IF gearing doesn't matter, then I can tune it now, somewhat, then tune perfectly on the Dyno in fewer runs.

IanS

 

Bro you must do the AFC hack. This will allow you to tune once you start boosting and not by throttle %. Thus you can use the MAF for the load and MAP to do the fuel trim under boost.

http://www.sddsm.org/pages/cars/dave...MAP%20VFAQ.jpg
http://www.2gnt.com/www/corbin/foolafc.html

 

Hmmm.

i dunno about that yet - maybe a project for this summer.

The feeling I'm getting is that I shouldn't even bother tuning the AFC at below 3000 RPM.

That sucks because i was hoping to gain some low end power, even if it is only 5hp....My Auto is a dog before boost.

IanS

 

Yup, don't bother tuning below 3000 because the only time you will see that is during launch (you will probably be feathering the gas, thus not being in WOT).

If you really want to, use your theoretical numbers and guess tune the low end. Do one or two runs to see how close you are to 12.5.

Keep this in mind. 12.5 may not give you the best hp/tq. Mardi and I went down to 11.X at some points. I actually gained about 11 whp by doing so.

 

Ok, dince I will be richening out across the band anyway, I don't see any danger to my car as being theoretically possible.

So i will try the settings I have above, except for the "lean" settings, and see what happens.

I won't lean anything whatsoever until I get to the Dyno, and only if I need to.

i will also try a run or 2 at 11.5:1 and see what happens.

IanS

 

Our best results were between 12.5 and 11.5. After trying 11.5, try 11.8 and check if you see any gains. Just keep playing around and stick with the best result.

Keep in mind that if you change, for example, 4000... you will also affect the points before and after 4000.

 

Stupid quesiton, but i need to ask for a good reason:

Adding +10% RICHENS the mixture (more fuel)
Subtracting -10% LEANS (more air, less fuel)

Right?

The reason I ask is that I added +10 across the whole thing, and my EGT's got higher....Aren't EGT's, and the engine in general hotter when lean (less fuel, more air)?

Doesn't added fuel give a cooling effect?

IanS

 

You are correct.
+10% richens and -10% leans.

Yes, more fuel will give a cooling effect so I don't know why your EGT's were higher after adding more fuel.

 

Ok, now I have some stupid questions

I don't have the dyno sheet handy right now but I had a pretty flat a/f curve ranging from 12.6 to 13.0 - this is just with the 6:1 FMU... has anyone tried running closer to 14.7, as opposed to running richer? I figured running richer wouldn't really help matters much.

Somebody here is new to tuning boosted a/f curves I guess (yay me).

 

You don't want anywhere close to 14.7 if you're boosted or BOOM

 

Aie! I thought being stoich was a good thing! I think I'll just set the s-afc to increase by 50% and flood my engine with fuel