How much faith do you put into the S-AFC II Knocking Sensor. With my settings I will occasionally get a spike up to 170-180 with the hotter weather (I live in Phoenix area). My settings which were tuned with a wideband 02 are 4000 -2%, 4600 -4%, 5200 -7%, 5800 -11%, 6400 -13%, 7000 - 14%. Hi Lo is 60/30. He tuned it to reach AFR of 11.3-11.5 range. My EGTs on WOT are usually around 750-800 Cels (1382-1472 F) and will taper off at 800 Cels (1500 F). My max boost is set at 19.5 psi.

Now since it has gotten hotter outside, I have cut my fuel numbers in half to be more conservative. Same NE points but 50% less. Knock spikes still occur, but less often and about 140-50 range. My buddy who is a DSM mechanic says I am just being too paranoid, that the ECU will retard timing if serious knocking occurs and I should be able to feel the power decrease, but I really have not felt any power loss during the indicated knock spikes. He personally does not place alot of value in the AFC2 knock sensor.

What do you guys think?

 

The AFC knock sensor is a POS..... It relies on manual calibration which is never going to be perfect and is extremely hard to get set to a figure which will be accurate... When I had my AFC i'd calibrate it and a few hours later i'd see knock at stupid points like 2500 or something... Or during cruising... If you really want a knock sensor i'd so go out and actually install a reliable one or take a look at your timing curve...

 

did you follow the directions to set the "knock count"? I'm getting a little knock now that its warmer... but its only in the 10-15 range...

 

If it works similar to the previous gen AFC's blue wire mod, I wouldn't trust it for any FI car. For NA, it's okay since it takes A LOT to blow it up. For TC, you have such a narrow and expensive window.

 

i would have to agree that its not very accurate... i hardly get knock...and it only registers when i've pushed the car hard and then i'm idling at a light or something.

 

Yes. It stays 0 for the most part unless it is idling when it is hot and has been driven for awhile 11-13 range or when the spikes occassionally occur on WOTs.

 

Thanks to other posts. You guys share the same idea what I have been tossing around. My EGTs are still cool and not spiking up badly during WOTS, so I guess that says I am still OK. I will try to get a MUT or a pocket logger to see what the ECU is doing to the timing. BTW, what I heard these ECUs are really the best gauge of knock.

Take care guys.

 

Hi,

I was also getting occasional spiking to 120+ with the warmer weather, but it's usually when I shift at or near redline at wot in the upper gears. I can do a pull in the same gears and it won't spike in the same rpm ranges. After the car has been running for awhile, I may get counts of 10-15 at idle or a little blip to 20-40 under accel, but I don't think these readings under 50 are an issue. I just calibrated to a count of 180 at 1500 and 3500 rpm. These 120+ counts were a little troubling though.

I did the same thing as you, and tried to richen up my settings. I had just installed my RT HF cat and thought I may need more fuel. I have also recently put in denso 1 range colder plugs and a walbro pump. Anyway, I still got some the 120+ spiking under WOT shifts in upper gears. Next I tried leaning it out to where it was before up top and I don't get the high knock counts anymore. Could it have been rich and on the shift the unburned fuel ignited to trigger the knock sensor?

It kind of seems backwards to me, since when it's cold, I need to lean out more at ~4500 to avoid a fuel cut. If it's cold, there is more air and should require more fuel, but the MAF reads too much and you get fuel cut. Now that it's hot, you may think you need more fuel to keep it cool, but of course when it's hot there is less 02 per unit of air, so you may need less fuel? When people were posting their cold weather fuel cut issues, some people posted that they richened in that rpm range and other posted that they leaned it out there to avoid the fuel cut.

Does all of this make sense?

My current settings with little or no knock activity are:

35/65 low/high throttle

high throttle:
2800 +0%
3200 +1%
3600 +2%
4000 +1 %
4400 0%
4800 -2%
5200 -3%
5800 -5%
6200 -7%
6600 -8%
7000 -9%
7400 -10%

low throttle are flat but +1% between ~3500-4500

Take care,

FB

 

Yes. Your observations make alot of sense. My spikes appear to be around 4000-5500k range. I was going to call the person that helped me tune with his wideband and ask what my lower AFRs were and try to add some fuel in those range. In addition my EGTs start to creep up in low throttle between 3500 area so I was going to add a little fuel in that area, but I will need the wideband again to tune again. Looks like our mods are very similar, but I do not have Walboro FP, which may be next.

Thanks for the posts guys. Sounds like our experiences are similar.

 

I get knocks of up to 190-200 on normal day and same on hot days it does not vary. I dont trust the s-afc for knock reading!!! It is a POS for a knock sensor. As long as your egt's are not above 950 C you will be ok. Just make sure you check your O2 with a wideband to ensure you are in the 11.5-11.8 reigon on pump gas. I was getting around 140-150 before my 272's went in and now I get 200 knock on occasion roughly in the 5000-5500 rpm range. But my egt (2nd runner 6 in from header) read about 825C at its highest point throughout the rpm range. I am running about 10.5-11 on the O2 side(pig rich).
When the car pulls timing you will be able to feel it, it will drop power off quick. Your setting are very conservative IMO. Before I did my injectors and cams my highest Ne pt was at -17 tuned buy a O2 to 11.8 . But it varies dependent on your mods. I wouldnt worry about the s-afc knock sensor. If you are rely worried you should buy the Tuboxs tuning box I want one sooo bad!! Mods for me are pretty much like buschur stage 4 with some other mods.

 

Thanks for the feedback.

Hopefully AZ will pass that law so we can quit using this bad gas MTBE (91 oct is the highest we have, unless you want race gas).

BTW, my EGT probe is mounted 4.5 inches from the block in runner #1 (passenger side). Highest they have ever reached is about 815C, that's only because I was cruising for awhile at 80mph and then got on it.

Take care.