Knocking the S-AFC2
Knocking the S-AFC2
Does anyone have experience with reading the Knock sensor monitor on the S-AFC II? I have done some searching, but nobody really seems to know what readings are normal and which are dangerous. I am currently using conservative settings for my afc, but would feel better if I could verify little/no knock. The manual only states how to set up the knock monitor, which I have already done. It would me nice to hear from someone who knows more about safc knock readings and a 4G63. Thanks.
By the way I just set up the knock sensor today and it was reading 0 on the way to work. I couldn't really open it up on the highway due to traffic, but I did notice the reading jump quickly to 8 and then back to 0 on WOT. When I pulled into work the knock monitor was 3. I have no idea what any of this means.
By the way I just set up the knock sensor today and it was reading 0 on the way to work. I couldn't really open it up on the highway due to traffic, but I did notice the reading jump quickly to 8 and then back to 0 on WOT. When I pulled into work the knock monitor was 3. I have no idea what any of this means.
Last edited by 95GSXtoEVO8; Dec 1, 2003 at 03:22 PM.
OK, well I haven't gotten any responses, but I will still post my own information. I stopped at an industrial park near my house on the way to picking up dinner and made 3 runs. These are my results:
Boost is set at 19psi to redline, gas 93 shell, all runs made from a roll 2nd gear to redline. I used the digital readout for the knock sensor, set to display the peak value.
1. stock settings - 29 knock (.92-.93 factory o2, i made 2 runs stock)
2. conservative settings using vendor settings - 154 knock
3. vendor settings - 110 knock
My conservative settings were just the vendor settings richened up a bit. I guess they weren't to conservative afterall. Again i only made 3 runs so maybe these knock results vary.
I really wish someone who has had a custom tune could try this and let us know what their peak knock settings are.
Boost is set at 19psi to redline, gas 93 shell, all runs made from a roll 2nd gear to redline. I used the digital readout for the knock sensor, set to display the peak value.
1. stock settings - 29 knock (.92-.93 factory o2, i made 2 runs stock)
2. conservative settings using vendor settings - 154 knock
3. vendor settings - 110 knock
My conservative settings were just the vendor settings richened up a bit. I guess they weren't to conservative afterall. Again i only made 3 runs so maybe these knock results vary.
I really wish someone who has had a custom tune could try this and let us know what their peak knock settings are.
Last edited by 95GSXtoEVO8; Dec 1, 2003 at 06:40 PM.
BTW someone else told me that while running aggressive settings, he felt what he thought was the ECU pulling the timing. His peak knock reading was ~180. He doesn't know conclusively that the the timing was being pulled, but so far this is my best example regarding this issue.
On another note, doesn't the ECU use the same readings from the knock sensor to determine whether or not to pull timing? If so, then wouldn't this knock reading be a decent way to see if the timing is being pulled, w/o using a datalogger that is. For those of us without a datalogger but with an safc2, why hasn't this been explored more?
On another note, doesn't the ECU use the same readings from the knock sensor to determine whether or not to pull timing? If so, then wouldn't this knock reading be a decent way to see if the timing is being pulled, w/o using a datalogger that is. For those of us without a datalogger but with an safc2, why hasn't this been explored more?
Last edited by 95GSXtoEVO8; Dec 1, 2003 at 05:33 PM.
I have researched a few things on this as well. From what I have gatherd what Apexi says is that 50 or less is pure normal but over that is true knock that the engine hears. From dyno results datalogging and testing it seems that the stock ECU pulls timing at about the 150 mark from what I can tell and the answers that I get from manuals and mechanics. If you run anykind of tuned setup you all know this is a easy mark to hit if you rev to redline. Also if you bounce off of the revlimiter it seemed to add a small amount of knock as well just looking at it from a numbers perspective. Hopefully dynoflash or someone with a little more knowledge will ring in to this topic.
I wish I could be more help on this subject. I looked this over and talked it over with Tym.
The AFC knock monitoring just doesn't seem to be consistent enough to give a good answer, that is the problem.
I wish every unit sent out of here and installed gave the same base numbers, then we would have an idea. Problem is every single guy that buys one and calls us tells us his base numbers are different.
This makes it hard for me to tell you that if you see 150 on the monitor that you have too much knock, say you started out with 68 and someone started out with only 20.
The AFC is VERY consistent in fuel tuning and is making tons of power for us and others. It is a GREAT tuning tool.
The knock monitoring in it is accurate too, we are fairly sure of that. The problem is each car is giving different readings and that makes it tought to say what is safe for everyone. There are differences in the raw engine noise that each engine makes, that is where it is suppose to draw its base from, then you have the differences in the knock sensors themselves. Get an engine with more raw noise and then a sensitive sensor and you could see a ton of false knock.
The only way to actually get hard numbers so you can use the AFC for reference is to have a really good fast reading datalogger. You could then watch to see when timing starts to get pulled and use this as a reference against what the AFC is showing you.
One other thing to point out is we did A LOT of street tuning on 94 pump gas with the car. We used a wide band 02 sensor to do it. We set the AFR's up in the 11.8-12.0 range. This is VERY safe for you car. We are not setting them up at the limit.
What I would suggest if you are using our tuning and seeing what you are uncomfortable with in knock numbers to turn the boost down a bit. This is also a way to find out what gas station sells gas that works the best in your car. Believe me 93 from one station will perform differently than 93 from another.
Hope this helps.
David Buschur
www.buschurracing.com
The AFC knock monitoring just doesn't seem to be consistent enough to give a good answer, that is the problem.
I wish every unit sent out of here and installed gave the same base numbers, then we would have an idea. Problem is every single guy that buys one and calls us tells us his base numbers are different.
This makes it hard for me to tell you that if you see 150 on the monitor that you have too much knock, say you started out with 68 and someone started out with only 20.
The AFC is VERY consistent in fuel tuning and is making tons of power for us and others. It is a GREAT tuning tool.
The knock monitoring in it is accurate too, we are fairly sure of that. The problem is each car is giving different readings and that makes it tought to say what is safe for everyone. There are differences in the raw engine noise that each engine makes, that is where it is suppose to draw its base from, then you have the differences in the knock sensors themselves. Get an engine with more raw noise and then a sensitive sensor and you could see a ton of false knock.
The only way to actually get hard numbers so you can use the AFC for reference is to have a really good fast reading datalogger. You could then watch to see when timing starts to get pulled and use this as a reference against what the AFC is showing you.
One other thing to point out is we did A LOT of street tuning on 94 pump gas with the car. We used a wide band 02 sensor to do it. We set the AFR's up in the 11.8-12.0 range. This is VERY safe for you car. We are not setting them up at the limit.
What I would suggest if you are using our tuning and seeing what you are uncomfortable with in knock numbers to turn the boost down a bit. This is also a way to find out what gas station sells gas that works the best in your car. Believe me 93 from one station will perform differently than 93 from another.
Hope this helps.
David Buschur
www.buschurracing.com
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Hi,
Well I drove my car for a few days, and after some tweaking it seems to be running well. I seem to have found a setting for the current weather where I don't hit fuel cut and I don't get excessive knock.
At first, I would see knock on the AFC, then richen it up at that point, then hit fuel cut there, doh!
Anyway, it may help to share baseline knock calibration settings. At 900 rpm I see about 75 knk. At ~1500 I have about 90 knk. At ~3500 rpm I see about 120 knk. Really drive the car around to get it fully warmed up, since the numbers change as it warms up.
In normal driving, I'll get 0 knk, or single digit readings. With WOT runs through gears and punching it from ~4000 rpm to redline in 1 gear I'll see little spikes of ~20-50. Once in awhile, I may hit 100 knk or so. I don't feel sudden loss in power or anything, so it seems pretty good. I'm sure I'm leaving power on the table, but I'll wait until I can get on a dyno with wideband to tune it more aggressively. I have a set of Denso iridiums so I may check and possibly swap plugs soon. They are 1 range colder so it may reduce knock and let me get a little more aggressive.
To tune, I would try to watch rpm and knk at WOT, and if I saw a higher number, I would add a little fuel around that range (or lean it out less). Crude, but I think it runs better now. Of course, I don't have objective dyno numbers or 1/4 mile times to prove this. Also, I had the SAFC wired wrong for a few days and I thought it was making a difference, so what do I know, lol.
Take care,
FB
Well I drove my car for a few days, and after some tweaking it seems to be running well. I seem to have found a setting for the current weather where I don't hit fuel cut and I don't get excessive knock.
At first, I would see knock on the AFC, then richen it up at that point, then hit fuel cut there, doh!
Anyway, it may help to share baseline knock calibration settings. At 900 rpm I see about 75 knk. At ~1500 I have about 90 knk. At ~3500 rpm I see about 120 knk. Really drive the car around to get it fully warmed up, since the numbers change as it warms up.
In normal driving, I'll get 0 knk, or single digit readings. With WOT runs through gears and punching it from ~4000 rpm to redline in 1 gear I'll see little spikes of ~20-50. Once in awhile, I may hit 100 knk or so. I don't feel sudden loss in power or anything, so it seems pretty good. I'm sure I'm leaving power on the table, but I'll wait until I can get on a dyno with wideband to tune it more aggressively. I have a set of Denso iridiums so I may check and possibly swap plugs soon. They are 1 range colder so it may reduce knock and let me get a little more aggressive.
To tune, I would try to watch rpm and knk at WOT, and if I saw a higher number, I would add a little fuel around that range (or lean it out less). Crude, but I think it runs better now. Of course, I don't have objective dyno numbers or 1/4 mile times to prove this. Also, I had the SAFC wired wrong for a few days and I thought it was making a difference, so what do I know, lol.
Take care,
FB
Guys, I cannot emphasize this enough. When you set the knock setting, make sure the car is FULLY WARMED UP. The engine has to be loud and twisting and really cranking it before you set your knock settings. If you do this, then the sensor will only report knock when it is truly knock, and not just the engine twisting around in the bay.
My knock settings are in the neighborhood of 200+ - my knock numbers only go off when I overboost (21-22psi) or after some really hard driving. Even then, the numbers I see at knock are under 10.
If you have your knock setting done correctly, it should ideally read 0 in daily driving. The only time you should ever really see numbers are continuous WOT runs, or after a track/autox session.
My knock settings are in the neighborhood of 200+ - my knock numbers only go off when I overboost (21-22psi) or after some really hard driving. Even then, the numbers I see at knock are under 10.
If you have your knock setting done correctly, it should ideally read 0 in daily driving. The only time you should ever really see numbers are continuous WOT runs, or after a track/autox session.
