jmecbr900

You mean set it to 8 NOT 4, right?

I would love to see the wiring diagram for the 400. That way when I hook it up, I'll have something to follow besides the book that APEX sends with the AFC.

BrokeGS: I would love to see the pics of the AFC too.

Guru

YOu know we have a great search function above. It would REALLY save you some time.

https://www.clublexus.com/forums/sho...highlight=safc

THat;s the diagram and set the cylinders to 4 not 8. Trust me.

jmecbr900

You da man!!!

It just doesn't work on 8 cyl setting? Which knock sensor wire did you decide to tap into after all?

Guru

Use 4 cylinder setting. I tapped into Knock sensor #1 but it doesn't really matter.

jmecbr900

Cool, thanks. I'll do that.

You wouldn't happen to have a pic of your install would you? As in where'd you put it?

How does your graph look after tuning? I suspect that I have an idea, but just wondering.

Guru

Depends on what mods you have on the car. If you have an intake you for sure have to add fuel at the bottom end and midrange. Remember this car is tuned PERFECTLY from the factory. You'll have to take out a little fuel up top. Keep an ear out for detonation. It's easy to make this car knock even with just an intake.

NoRyceGS4

what is happening when detonation / knock occurs?

Guru

If you have to ask that question definately have a tuner tune the car for you. It will be safer.

jmecbr900

There are a couple of different causes of "knocking". Low octane gas, heavy load, incorrect ignition timing, cylinder temperature, etc. When the engine knocks it is usually due to the mixture of gas/air being compressed pre-ignites. In other words, it explodes at the wrong time in the cycle. If the piston is on the way up compressing the mix and before it reaches the top, i.e. full compression, it is ignited....knocking. Lower octane gas has, I believe I read somewhere, a lower "flash" point than higher octane gas. So lower octane gas is more prone to knocking because the higher cylinder temps would make that mixture easier to detonate early, i.e. at the wrong time.

It's basically the engine not being as efficient as it should be. The danger of knocking while under boost is pretty obvious. If you start knocking while under boost, the additional exponentially higher cylinder pressures that make power can also break car parts like rods/pistons. If you are running any kind of boost, even nitrous, and you explode the mix (which will make the piston wanna go back down) while the piston is trying to push up......this is how we get a "thrown rod thru the block" scenario. This is why in older cars, people used to "retard" the ignition timing when running nitrous/boost to avoid detonation. Another way is to use very high octane race gas.

In our cars, the ecu (via readings from several sensors including the knock sensor) controls ignition timing. If it senses knocking, it will retard the ignition until the knocking stops. Unless you re-map the ecu, there is no way to externally control timing in our cars. Therefore, it is very important that when you are boosting and trying to make the ecu do the things YOU want it to do instead of stock....you stay away from knocking. Hence, the AFCII's ability to warn you when knocking occurs and thereby giving you the chance to either re-program less aggressive a fuel curve or shut down and find the problem BEFORE you blow something thru your hood.

I could go on and on, but I think you get the pic.

Mr Johnson

Just stumbled on this thread and I've got a couple of comments, FWIW.

*I* would run a bit richer than 13.1 in a boosted scenario perhaps closer to 12.5.

Depending on how your car shifts and/or how often you intend to hit the rev limiter under boost I would *add* fuel on the top end.

Obviously this all depends on how your fuel curve looks right now.

Guru

If you're running boost I'd probably never run leaner tha 12:1. On some WRX's I run them as rich as 10.8:1 depending on turbo sizing and other factors. If you have water injection or race fuel it's a different story.