Anyone know the rpm operating range for the S197 4.6L 3v knock sensors?

[MrClean]

I think I read they operate up to 3000 rpm or so, but after that they're innefective due to engine vibrations. Anyone got the specifics on this?

 

[jbailer]

Knock sensors are a touchy subject. Once you start modifying, knock sensors can quickly become not only inefective but ineficient. Stock in the S197, the knock sensors are used through the entire RPM range. You add a supercharger, change anything in the rotating assembly or anything like that and you will most likely change the knock signature. That difference in signal characteristics measured by the knock sensor then interpreted by the ECU will most likely rob timing and possibly dump extra fuel to avoid what it interprets as a possibly lean knock condition. Since knock sensors were introduced the favorit thing to do with a built engine is to disable them. To avoid codes many would wrap them up in foam and zip tie them away from the engine. It's nice in our car, we can simply disable them. -Joe

 

[cekim]

Stock in the S197, the knock sensors are used through the entire RPM range. You add a supercharger, change anything in the rotating assembly or anything like that and you will most likely change the knock signature....

What he said... Stock tune uses them throughout the entire range. Stroking, boring, supercharging etc.. all have an impact on the knock sensors as they are essentially microphones.

 

[MrClean]

Thanks guys. So for my almost stock engine, running a Bama tune, I wonder if the knock sensor is disabled above 4K? Why, with a Bama tune would I get audible pinging? (ok, ok, so my ear is specifically "looking" for that sound when I test under WOT in 4th). I retard timind using the xCal, and add 2% WOT AFR, and it stops doing it. The problem is tyo keep it from pinging, I'm running a 91TQ tune with -4º (4k-63k), and -2º (2k-4k), and +2% WOT AFR, while running 93 Octane Shell gas (I started a separate thread on that).

 

[jbailer]

MrClean, you'll have to discuss that with your tuner (Doug?). It's probably not fair and pretty difficult to just guess why you are getting audible knock with that tune. I would ask questions like, "Are the knock sensors enabled? If so, through what frequency range?" I'm not familiar with the knock sensors in our car and how aggressive they are. I worked with a different appication before that didn't allow any knock at all. Of course that was at the expense of retarded timing and a little fuel dumping.

With no modifications to the rotating assembly and no FI (basically almost stock engine) you can go 2 ways. Leave the knock sensors enabled because they should still function fine or disable them and trust the tune. The benefit of leaving them enabled is the obvious safety factor. Disabling them will most likely yeild more power and if the tune is good you will be pretty safe. My personal preference is to tune it right and get rid of them. -Joe

 

[05mustang_TT_charged]

get gas from another station and try 89 octane to see if it goes away

 

[DirtyDogOfTheDesert]

Your tuner can also adjust the how much timing is pulled due the knock sensors. Rather than turning them off, just set it up so it pulls 2 or 4 degrees instead of 10 or more, or what ever they are currently set at.

 

[MrClean]

get gas from another station and try 89 octane to see if it goes away

Yes, that is the plan...the tune I ordered from Brenspeed is gonna take 5-7 days, in the mean time I'm swithcing to Chevron, and I'm gonna run the 87 octane...I was thinking last night that my car may just not tolerate the aggresive timing, so it may be a waste to be trying to run those tunes and buying that more expensive gas.
You see, I can get Doug's 87 Perf tune to work w/o pinging,: I add 2º below 4k rpm, and take 1º out above 4k rpm, and that works, but I sholdn't have to burn 93 to run an 87 tune (an 87 w/o "tweaking"), that's what bugs me.

Your tuner can also adjust the how much timing is pulled due the knock sensors. Rather than turning them off, just set it up so it pulls 2 or 4 degrees instead of 10 or more, or what ever they are currently set at.

That's an excellent point...I'm going to write Brent about that immdeiately so that he takes it into account, thanks!

BTW, does anyone know what the timing curve is for a stock GT? How many degrees at each rpm point?

 

[jbailer]

BTW, does anyone know what the timing curve is for a stock GT? How many degrees at each rpm point?

Unfortunately or fortunately depending on how you look at it, timing is not nearly that easy any more. Rather than a simple 2D table as in the past, there is a base spark table called the "Borderline Knock Table" that rather than a simple timing based on RPM is now a 3D timing based on RPM and load. This table is modified by at least 4 other tables like knock sensor, CHT, EGT and ACT. I can tell you under no load there is as high as 50* advance and under full load in the stock table there is a max of 17.5* @ 4,750 RPM and it goes down to 16* at 6,500 RPM. That would be max timing stock with no modification from any of the above listed tables. -Joe

 

[MrClean]

Unfortunately or fortunately depending on how you look at it, timing is not nearly that easy any more. Rather than a simple 2D table as in the past, there is a base spark table called the "Borderline Knock Table" that rather than a simple timing based on RPM is now a 3D timing based on RPM and load. This table is modified by at least 4 other tables like knock sensor, CHT, EGT and ACT. I can tell you under no load there is as high as 50* advance and under full load in the stock table there is a max of 17.5* @ 4,750 RPM and it goes down to 16* at 6,500 RPM. That would be max timing stock with no modification from any of the above listed tables. -Joe

Thanks, interesting information.

BTW, to get the degree sign (º), press the ALT key and at the same time on the number-pad, enter 167.

Got me some Seafoam, so I'm gonna put it in the tank then add ac ouple of gallons of (Chevron 93) fuel for good mixing, and see what that does.

Happy New Year!

 

[jbailer]

BTW, to get the degree sign (º), press the ALT key and at the same time on the number-pad, enter 167.

That's useful information if only I could remembr it. Maybe I can write that down on my keyboard. -Joe

 

[SixtySix]

Not everybody has a PC you know!

Alt + k for all you Mac lovers out there ;-)

 

[GIG4FUN]

That's useful information if only I could remembr it. Maybe I can write that down on my keyboard. -Joe

To help you there are a few sites out there (I have a sheet printed) and this site is likely the smallest amt. of info on any of them so it is quick to find help on it if you forget:

http://tlt.its.psu.edu/suggestions/international/accents/codealt.html#math

 

[jbailer]

To help you there are a few sites out there (I have a sheet printed) and this site is likely the smallest amt. of info on any of them so it is quick to find help on it if you forget:

http://tlt.its.psu.edu/suggestions/international/accents/codealt.html#math

Awesome! Bookmarked and I'll use it, thanks! -Joe

 

[marcspaz]

There are hundreds of shortcuts keys to special characters.
° ± ¼ © Ώ ‰ ™ → fi ∏
I am just lazy as shit and I am trying to type fewer key strokes, not more. So I just use * as my degrree symbol and +/- for my ±. People get the point