SlowestS4Here

Hi all,

I'm trying to get a better fix on how concerned I really should be when I see correction factors that are saturated at 15.

I owned a stage 3 (homebrew kit) S4 and used lemmmiwinks to tweak/tune the X-chip. I got that car up to around 400whp on stock IC's (with race gas).

Regardless of the fuel I was tweaking for, the results were always the same: My correction factors would saturate to 15 WELL before my knock voltages got to levels that I consider worry-worthy (>15-20V).

Unfortunately that car was totalled out, and I have recently purchased a bone stock Casa White 01.5 6spd S4 w/60k miles.....yippee!

I've been tweaking the stock S4 with some lemmitweaking of the timing and fueling. Stock, the car started off pulling 6.5sec FATS times, and now the car is pulling ~4.8s FATS times with 93octane @75F. This is with about 5% extra primary fuel and 13.5deg timing advance (and some other minor tweaks). The boost is peaking at 15psi (which seems a little high for stock), but tapers to 10psi at redline.

My timing at redline is consistently ~20-25deg.

The same theme rings true with this S4 in that the correction factors shoot through the roof before the knock sensors get to dangerous levels. I'm definitely not hearing any audible pinging, and the engine seems happy and runs strong.

I keep reading about how some of you guys are able to get 20-25 deg of timing at redline, with knock sensors that are below 20V, and correction factors below 10. How do your CF's stay so low?

In order to push the engine hard enough to make the knock sensors raise to above 10V, my correction factors are already saturated at 15!

I've been keeping the octane at 93-95 with toluene addition to 91 octane.

Any ideas what other variables could be increasing the correction factor without having an effect on the knock voltages?

I'm a bit confused here because, like I said, the car is running pretty well (20-25deg timing at redline & 4.8FATS times with 100% stock components), but at the expense of saturated correction factors.

Can any of you make some sense of this?

PSmalls::DoggieStyle

I can't believe you are pulling 4.8 FATS times on 100% stock components. Your boost curve would indicate that you are actually chipped, but you know your car better than me. Also, sorry to hear about your other car getting totalled. As for the correction factors saturating at 15, I'd pull back some timing if it were me.

Ochlockonee

In my car with Apr V5.0 I get CFs of around 10. If I put in the MTM software with a)more boost, and b) an average of 10 degrees more timing under boost than APR, my CFs go down to about 8.
IIRC my knock sensors are at about 13 volts w/APR and at least 20 W/mtm. O2 sensors read the same under WOT for both ecus.
Knock voltage is not something that I log anymore since I can't do anything about it short of unscrewing my knock sensors or just jacking up my timing past my ecu's ability to retard timing from knock.

PSmalls::DoggieStyle

2nd. I never log KVs anymore, just CFs.

Captain Matt, I be

ME7.1 uses to determine when to pull timing.

SlowestS4Here

Plus, it seems as though the CF's are dictated by the software, which is exactly why the knock sensors are more important to track than the CF's IMHO. Since CF is a variable that is set arbitrarily (by the software), and the knock voltages tell you what is actually going on in the engine, wouldn't you track the knock voltages more religiously than the CF's??

PSmalls::DoggieStyle

I disagree completely on the KV vs CF thing. As I understand it, KVs are used to find CFs. CFs is the end result of everything. It tells you how much timing is being pulled. The ECU can only pull so much timing, so you want to keep it low enough in xxx weather so that in extreme weather the ECU can pull back more as necessary. If you are already pulling back the max in, for example, 50F...what do you think will happen when you are in 90+F weather? Just my 2 cents.

Captain Matt, I be

if you keep advancing timing once you hit the limit of 15 degrees of retard, you remove one of the safety measures built into the car.

If for whatever reason you start detonating, your ECU will not be able to pull timing to prevent engine damage.

JasonS4+Festicle

stuff. Maybe now we know the CF seem better but many, many people made tweaks using KVs only and never blew anything up (that I know of) - myself being one of them.

It seems either these motors are pretty tough or we don't know exactly what all this stuff (CF, KV, etc...) means yet - probably a little of both.

PSmalls::DoggieStyle

only max in extreme weather conditions.