More false knock

[smokinzx14r]

Update: After swapping out my stock fuel pump for Sai Li and hooking back up I went from no knock with stock pump and BAP to 7 degrees with Sai Li and new tune. Swap stock pump back and back to old tune, zero issues. Take that for what you will. Pretty sure I have my answer. Will be going AED.

Kind was thinking the same thing ..

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[Tommy V]

U sure about that Mark and im only asking because im not sure myself.But when i first did my flexfuel tune i though that when they sent me the tune it was flex,well it was a 93 tune that i was suppose to log first.Anyway i put e85 in their and after about 20 miles a i had some codes come up.Two were from knock and i think a lean code,the sensors worked fine and all wiring good.They gave me a new tune and codes were gone.The voltage changes according to how the frequency changes correct???

 

[markmurfie]

I think we have siemens sensors but the flat responce transfer would be similar.
Output stays within ± 15 percent of average value at the limits of 1 to 18 kHz.
The Knock sensor signal drives a Transistor as an amplifier that uses a 5v reference circuit through a resistor. The ecu uses that signal as its knock signal.
That 5 volt circuit is what sets the CEL for high or low.

You would need a almost constant sound in that frequency range to dive the voltage high or low enough to set a CEL. An engine wouldn't last long if that were to happen from real knock and a CEL would basically be telling you that. With false knock its picking up signal intermittently, like in constant tapping, so the voltage never gets driven high or low for long enough to set a CEL. I don't know what the exact threshold is that sets off the CEL, but it probably pretty bad. I'm sure a source of false knock could get there, but logs would easily tell you its false as the sensors would never add and be positive almost constant.

 

[Tommy V]

I think we have siemens sensors but the flat responce transfer would be similar.
Output stays within ± 15 percent of average value at the limits of 1 to 18 kHz.
The Knock sensor signal drives a Transistor as an amplifier that uses a 5v reference circuit through a resistor. The ecu uses that signal as its knock signal.
That 5 volt circuit is what sets the CEL for high or low.

You would need a almost constant sound in that frequency range to dive the voltage high or low enough to set a CEL. An engine wouldn't last long if that were to happen from real knock and a CEL would basically be telling you that. With false knock its picking up signal intermittently, like in constant tapping, so the voltage never gets driven high or low for long enough to set a CEL. I don't know what the exact threshold is that sets off the CEL, but it probably pretty bad. I'm sure a source of false knock could get there, but logs would easily tell you its false as the sensors would never add and be positive almost constant.

Gotcha,good info,thats why its so important to look at these looks very carefully and not just look to see if u have knock,but seeing what is really going on.Also i was not sure if it was a certain threshold or a certain amount of knock events that turned on the cel.

 

[sigintel]

Wonder if the circuit can ground couple EMI?
Maybe draw of two pumps without enough wire guage and bypass caps causes excess noise on chassis ground?
Maybe try using heavy Aluminum duct tape wrapped loosely round knock leads and end with that tape w metal against metal at sensor?
Bad coil ground?
Damn, borrow an oscilloscope or bring it by?

Edit. New idea, is this common on centris?
Could there be enough harmonic noise from how centri is mounted to front cover? Front engine cove is like a piano sound board. Can you try bolting a heavy chunk of steel like a 10# gym weight to the mounting plate or bracket?

Edit, always possible it is real knock. Check in knock sensors were over torqued? or if sensor bodies are twisted to be touching at more than one point instead of free cantilevered out from mounting nut?

 

[Tommy V]

Wonder if the circuit can ground couple EMI?
Maybe draw of two pumps with hout enough wire guage and bypass caps causes excess noise on chassis ground?
Maybe try using heavy Aluminum duct tape wrapped loosely round knock leads and end with that tape w metal against metal at sensor?
Bad coil ground?
Damn, borrow an oscilloscope or bring it by?

Edit. New idea, is this common on centris?
Could there be enough harmonic noise from how centri is mounted to front cover? Front engine cove is like a piano sound board. Can you try bolting a heavy chunk of steel like a 10# gym weight to the mounting plate or bracket?

If thats the case wont everybody with a centri blower just turn off the knock sensors and call it a day.I know plenty of guys with centris that have o knock,wot,cruise,tip in.How many guys on here knw how to u use oscilloscope!!! and catch glitches?I know of 2 motors that went thst guys on hear that could not change a spare tire were hollering its false knock.

 

[Davepurp]

It seems most people myself included didnt always have Knock it came in after a recent upgrade, assuming its not tune related we should all be able to solve our own issues with time just takes a little patience I guess

Anyone else outside of an E85 service area consider running Meth Injection? IATS never get too high with the Procharger, just trying to think of other ways to add timing instead of the bottle of octane boost every fill up

 

[ProChargerTECH]

Update: After swapping out my stock fuel pump for Sai Li and hooking back up I went from no knock with stock pump and BAP to 7 degrees with Sai Li and new tune. Swap stock pump back and back to old tune, zero issues. Take that for what you will. Pretty sure I have my answer. Will be going AED.

Wait what?

A fuel pump swap caused your knock?

 

[TooSoonJunior]

Wait what?

A fuel pump swap caused your knock?

I think he is saying it was the new tune

 

[Davepurp]

I copied and pasted this from my other thread but I thought it would be helpful for a few people here and wanted to give credit where credit is due to Diablo Matts tune and revisions
Spent the weekend Tinkering around, cleaning up vaccuum lines, zip tying everything neat and tidy and the logs speak from themselves.

Same Fuel. Same Tune from [MENTION=20966]diablomatt[/MENTION] and knock is nearly gone completely.

1st Tune:
http://datazap.me/u/davepurp/mak-pipe-boss-302-pulls?log=0&data=12-20

Revised Tune False Knock
http://datazap.me/u/davepurp/boss-d-tune-highway-pulls?log=0&data=12-20

Revised Tune No Knock
http://datazap.me/u/davepurp/ngauge-low-wot-pulls-d-tune-boss-302?log=2&data=2-5

 

[venumous]

I think he is saying it was the new tune

Correct, I am left with no other reasonable conclusion. I hate to pay more for another tune but how else do you explain going from zero knock on stock fuel setup to knock on both 93 and E85! On new fuel system to no knock on stock fuel system? I don't think the knock is false. Do you guys recommend Shaun or Ken? I would be happy to use Matt but I don't want to buy a new tuner on top of tune. I've also been looking at lesser known localish guys like DGR who tuned mg 03 Cobra and DTP in VA who has tuned a friends setup.

 

[TooSoonJunior]

Did Sai Li use your base tune to come up with your new tune? Or was it entirely new? It should be pretty easy to modify any tune to accommodate a return style system, its literally 3 or 4 changes. It shouldn't have required a brand new from scratch tune.

 

[venumous]

It's a Lund tune. And he did provide a new base tune and insisted it necessary.

 

[moffetts]

It's a Lund tune. And he did provide a new base tune and insisted it necessary.

My buddy's Whippled 2012 killed its fuel pump and Lund had no problem updating his tune to accommodate the new return style system.

 

[venumous]

And I'm sure that's the case 99% of the time. In my case, clearly something is wrong with tune or FPR/GT350 Pump (highly unlikely as I've tested each pump independently on startup and idle).

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