How much will false knock hurt performance..
Thread Starter
Burning Brakes
Joined: Sep 1999
Posts: 848
Likes: 4
From: Tulsa,Ok
How much will false knock hurt performance..
To be exact,my total timing is 37 degrees,but I keep picking up false knock,and its staying at 31-32 total.How much is that hurting performance.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: How much will false knock hurt performance.. (gears)
When I had a similar problem at WOT near the shift point it cost me several MPH at the traps! Essentially you're igniting the mix too late and losing some ponies.
Former Vendor
Joined: Jun 2001
Posts: 7,204
Likes: 6
From: St Marys PA
Re: How much will false knock hurt performance.. (Nathan Plemons)
Yes they are right! You should actually be able to feel it. It should feel like something is dragging the car down then releasing.
The knock sensor is a great idea, but the algorithm works like this. It hears the knock, pulls some timing, if still there it seems to pull a ton too much out. In other words with the first onset of knock the computer may pull out 1.5* were 2* is the correct amount to pull. Then becuase there is still knock it will pull 4 more, for a total of 3.5 too much. This is what hurts you.
In your case with "false" knock. It will pulling out needed timing right off the bat.
I must ask how do you know it will false? Recheck your base timing. I would imagine you have a scanner hooked up to see the counts. If your base timing is off then whatever the displayed value, say 37 is skewed my the difference from 6* base timing. For example: If you have the base timing at 10* instead of 6* then you are actually running 41*. There is absolutely no need to run more than 6* base timing for a "stock" car.
[Modified by ski_dwn_it, 2:19 PM 9/14/2002]
The knock sensor is a great idea, but the algorithm works like this. It hears the knock, pulls some timing, if still there it seems to pull a ton too much out. In other words with the first onset of knock the computer may pull out 1.5* were 2* is the correct amount to pull. Then becuase there is still knock it will pull 4 more, for a total of 3.5 too much. This is what hurts you.
In your case with "false" knock. It will pulling out needed timing right off the bat.
I must ask how do you know it will false? Recheck your base timing. I would imagine you have a scanner hooked up to see the counts. If your base timing is off then whatever the displayed value, say 37 is skewed my the difference from 6* base timing. For example: If you have the base timing at 10* instead of 6* then you are actually running 41*. There is absolutely no need to run more than 6* base timing for a "stock" car.
[Modified by ski_dwn_it, 2:19 PM 9/14/2002]
Le Mans Master
Joined: Aug 1999
Posts: 7,339
Likes: 137
From: WilkesBarre PA
Re: How much will false knock hurt performance.. (ski_dwn_it)
On a 95 you can change the Knock module in your computer to a 96LT4 module. It is less sensitive than the factor LT1 module. It only takes 5 min to change, and only cost around $30 from GM.
Thread Starter
Burning Brakes
Joined: Sep 1999
Posts: 848
Likes: 4
From: Tulsa,Ok
Re: How much will false knock hurt performance.. (gears)
I already have the LT4 km.The reason I believe its false is because on the street from a roll,it gets no retard.but at the track,i get some wheel spin and bang the gears alot harder,it takes out 5-6 degrees,and never recovers it all the rest the way.
Former Vendor
Joined: Jun 2001
Posts: 7,204
Likes: 6
From: St Marys PA
Re: How much will false knock hurt performance.. (gears)
I would not trust that theory. When you are at a track you are hammering on it much harder than on the street. The car experiences MUCH more loading on a track. That is why Things usually break at the track were as on the street you can get away with more.
Here is what you could do, its a simple little test. Back your timing down to say 0*. See if the knock goes away. If it does than its real. If still there back it down even more just to make sure. The car will probably run like crap, but for experimental purposes it will do just fine.
Good luck!
Here is what you could do, its a simple little test. Back your timing down to say 0*. See if the knock goes away. If it does than its real. If still there back it down even more just to make sure. The car will probably run like crap, but for experimental purposes it will do just fine.
Good luck!
Drifting
Joined: Jun 1999
Posts: 1,874
Likes: 1
From: Garden Grove CA
Re: How much will false knock hurt performance.. (gears)
On my Rocket, on the dyno, when the knock sensors went all the way off I have seen as much as ~ 50 hp lost! Currently I have max WOT advance at 41 degrees. There was however a weird tuning problem causing low rpm knock retard upon WOT. it seemed like sudden low rpm throttle tip in would set off knock retard. All I did to eliminate this was to retard low rpm WOT advance from 33 degrees to 31 degrees and the problem disapeared.
Thomas
Thomas
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Thread Starter
Burning Brakes
Joined: Sep 1999
Posts: 848
Likes: 4
From: Tulsa,Ok
Re: How much will false knock hurt performance.. (The Green Rocket)
Hey Green rocket,I was just curious as to what kinda gas you run.They have 93 octane here where Im at.41 degree total seems like alot,unless you run race gas.
Instructor
Joined: Apr 2002
Posts: 243
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From: Hockessin DE
Re: How much will false knock hurt performance.. (ski_dwn_it)
so your saying when my scan tool reads spark advace at WOT as 31*, i have to add the base timing number (6*) to get my total advance (which would make it 37*)?
Drifting
Joined: Jun 1999
Posts: 1,874
Likes: 1
From: Garden Grove CA
Re: How much will false knock hurt performance.. (gears)
No race gas. The 41 degrees is with that fabulous 91 octane oxygenated gas that is the max commonly available in Cali. I have in the past used 100 octane unleaded, but it didn't add anything for me. I do still have the factory catalytic converters in place.
Oxygenated gasoline is weird, I too would have thought that to be a lot of advance for 91 octane, but my knock sensors, which are properly functioning, have not detected any knock (they did until the fuel and spark curves were reworked). The answer I will again attribute to LT1Edit, which has allowed me to do on the spot computer tuning. In addition to the 1/2 day of chassis dyno tuning time, I also spent some on the road doing part throttle tuning before the chassis dyno pulls. I cannot suggest that everyone would benefit from the same advance curve that I have. In addition to the ~ 11:1 compression that I have, my heads have also had some port and chamber work that have affected this engines advance curve requirements.
Thomas
Oxygenated gasoline is weird, I too would have thought that to be a lot of advance for 91 octane, but my knock sensors, which are properly functioning, have not detected any knock (they did until the fuel and spark curves were reworked). The answer I will again attribute to LT1Edit, which has allowed me to do on the spot computer tuning. In addition to the 1/2 day of chassis dyno tuning time, I also spent some on the road doing part throttle tuning before the chassis dyno pulls. I cannot suggest that everyone would benefit from the same advance curve that I have. In addition to the ~ 11:1 compression that I have, my heads have also had some port and chamber work that have affected this engines advance curve requirements.
Thomas
