Getting the most out of your Apexi S-AFC= Stock MAF honeycomb removal

[Innovator]

Originally posted by Odin
Innovator: Nice find with the gutted MAS project, but I have a few questions for you.

I'm running 550cc injectors and get large amounts of knock at anything leaner than the settings I have right now. At -30% correction on 15 psi of boost, I saw a high of 28 knock. I richened it up about 5 percent after 2800rpm and now I have about 2 knock, which is perfectly acceptable in my eyes. it fluctuates between 0 and 2 counts of knock, nothing more. My AFC corrections SEEM to be very rich, an average of -25% at WOT, varying a bit throughout the RPM range. The weird part is I'm NOT running very rich at all. o2's show an average of .96 with some spikes to .98. Timing advance in the upper RPMs is in the low-mid 30's neighborhood. So what's the deal, why am I weird

Odin, the real question here is what is an acceptable level of knock, using the knock count as a guide

[shofear]

It sounds to me like you may be too rich or too lean

Well considering I tried settings from -5% (with fuel spitting outta the exhaust, rich as hell) all the way to -25% I think I pretty much covered running either to rich, lean, or in between. Over 3K with settings -20 reaching -26 to redline the car pulls real hard, but anything under 3K is crap acceleration, and driveability.

This mod just looks like it's not gonna work for me, oh well at least it was reversible and I tried it out.

[Innovator]

Odd.

I have the same year car and similar mods to yours.


The biggest difference between us is the IC's. I see no reason why it wouldn't work on yours perfectly.

I've done this to another 95 (AllEyesOnMyVR4) and his runs the same way mine does, as far as having no dead spots.. He has stock ICs.

I noticed that your fuel correction unit is an HKS. I wonder if that has anything to do with it

[duffman]

Originally posted by shofear
It sounds to me like you may be too rich or too lean

Well considering I tried settings from -5% (with fuel spitting outta the exhaust, rich as hell) all the way to -25% I think I pretty much covered running either to rich, lean, or in between. Over 3K with settings -20 reaching -26 to redline the car pulls real hard, but anything under 3K is crap acceleration, and driveability.

This mod just looks like it's not gonna work for me, oh well at least it was reversible and I tried it out.

Do you still have all of your cats?

[X-Man]

Originally posted by antero
Take a look at my signature.

This is weird man... no car is the other alike....

Wher your at 3,6k and -17 i´m at -28 and your 4,2k and -18 i´m at -29 and i´m still running rich as hell....

Why does my car run rich with my numbers?

[boostedVR4]

Originally posted by boostedVR4
My combs were glued very slightly. Nothing a little alchy and the back of a screw driver didn't take care of.

I have Denso 550cc injectors, Supra pump (hotwired) and the IPO dual feed fuel system. Right now, my AFC is set to around the -36 to the -37 range.

I have looked back on quite a few logs, and noticed one major detail about my knock. It ALWAYS, (and I mean always) starts at 33 degrees TA. I'de never really paid alot of attention to my timing before, now I am. Every single run, 02's are at .94 -.96, duel, all the way up to about 5k. My timing starts at about 18, then goes up. When it hits 33, (and this is each and every time) I get knock. Then down comes the timing. I'm talking knock over 10. You can see my log up a few posts. The only way I can stop the knock is to add fuel, which runs it rich.

So how can I stop the ECU from advancing the timing so much?? My base timing is right where it should be. I'm going to try this gutted MAF trick, mainly for the added flow/spool up. But if it lowers my timing enough to get it to stay below 33, that would be perfect.

I still don't see how this is going to effect the timing at all, but I'll try anything for fun.

Welp, I did it this morning. Unplugged the battery, installed my spare MAF with combs removed. Started the car, and of course it was a riot. Idled like a monster truck, revved like a 30 year old weed wacker. Anyway, it took me a total of about two mintues with my Pocketlogger to figure out how to smooth out the idle, smooth out the throttle response, and get the car into closed loop. I set my low throttle 1k to about +12, and 2k to about -5. Anyway, the low fuel trim after driving is 108, high is 102.

On for the high settings. I started out by adding 10% more fuel accross the board to be safe. Turns out, it was damn close to being perfect. As of now, I have it about 10-12% richer across the band than before, but its still a little lean for my tastes. I had to stop making passes when my brakes started to smell and stopped working....

Anyway, I got a log, 2k to redline, 02's start at .92, then go into .94 all the way to about 6500 rpm, where it goes .96. No knock, with 1.1 bar. (higher than my first log) BUT, the timing is still crazy high. (I'll post a log pic soon) It still gets into the upper 30's.

So, in conclusion, it took me about 45 min to change the MAF, tune the idle, then tune the high settings by making about 5 passes in 2nd gear. I still don't know about a 3rd gear run, it might be a tad lean yet. Its not like my VPC, but I like it. Throttle response is 100% normal, the car goes into closed loop just fine. Pretty much the car is EXACTLY the way it used to be, only it spools quicker, pulls a little harder, and holds a little more boost to redline. I'll be doing this mod to my friend's VR4. (Adler's old car)

Pros:
*easy and fast mod
*spooled quicker
*pulled slightly harder
*held a little more boost to redline
*using about 10-15% less of my S-AFC

Cons:
*didn't solve my timing mystery

[Multiades]

Originally posted by boostedVR4
Cons:
*didn't solve my timing mystery

Of course it didn't. This mod is not capable of solving advanced timing w/ larger injectors. Essentially the only way to "solve" that problem is to make more power -- in other words, come closer to maxing out the injectors you have.

-Chris

[BlackStealth]

When I review my runs with the pocketlogger, my timing is in the 20's. When I review the same log on the PL Viewer (on the PC), they are in the 30's. I don't know why they don't offer the "Stealth timing correction" on the PL Viewer. When people are reporting their timing what are they using as reference?

Also, my timing drop of -1 is generally between 3000->5500 rpms. After 5500 rpms they start to go back up again. I'm guessing this is because the ECU already knows torque falls off at around 5152 rpms and believes it needs to advance timing. Generally the ECU advances timing during lighter loads.

Incidently, last night I discovered a major boost leak that has been with my car ever since I installed 15G turbos. With that leak fixed, my car just roars after 5000rpms now.. wo ho! This probably explains why I'm running so rich up top. I'll have to do some more tuning again.

[Innovator]

Originally posted by Multiades
Of course it didn't. This mod is not capable of solving advanced timing w/ larger injectors. Essentially the only way to "solve" that problem is to make more power -- in other words, come closer to maxing out the injectors you have.

-Chris

My car must be the exception then perhaps the second gen optic sensor reacts a bit differently?

How would making more power solve the problem BTW? This mod does achieve that, but timing that is too advanced is timing that is too advanced.

[Multiades]

Originally posted by Innovator
How would making more power solve the problem BTW? This mod does achieve that, but timing that is too advanced is timing that is too advanced.

When you are getting closer to maxing out the injectors, you are showing the ECU very high airflow values. If you are able to show the ECU the same airflow values WITH the negative correction (for uprated injectors) that you were showing it with the stock injectors, you will run the stock timing.

If you add injectors that are 50% larger than stock (compensating with the AFC), then proceed to make 50% more power than stock, the ECU has no idea that there was any change at all.

Now with 50% larger injectors (550cc/min), you do not compensate with the AFC downwards 50% -- you compensate downwards somewhere around 34.54%. In other words the ECU will see:

(100% - 34.54%) = 65.46%

of the airflow going into the engine.

However, 50% more airflow (or 150% of 65.46%) equals approximately 100%, so the ECU will see the same airflow as before the injectors, and will actually be delivering 50% more fuel to the 50% more air coming in.

Hope that is a relatively clear explaination.

-Chris