I remember reading, I thought on this site, about some people bypassing the knock sensor at the track for reduced e/t's using a relay and a toggle switch. Was wondering, who here has done this and if you are having any luck(at the track), also, I have done a search but with no luck. It seems that there are many ways to knock a tenth or two off the e/t, no front sway bar, drag shocks, locking up the convertor, lowering the crown nuts on your spring, to help with weight transfer(this gave me 3/th's at the track) Just trying to get the most out of my setup and come up with different ideas on reducing e/t's besides the mainstream ways. Thanks as always.

 

If you are not getting any knock counts, it will make ZERO difference. If you are, you'd best find out why before you disable the ESC.

RACE ON!!!

 

I couldn't agree more. This is one of the biggest advantages of electronic engine mamagement. It protects the engine from itself.... and you.

 

Hey CFI, as always appreciate your input and understand what your saying, what I'm referring to is false knock, maybe from an aftermarket cam, roller rockers or just headers. It seems a very popular mod for the 96 LT1's is to put in the LT4 knock module just for a roller rocker swap, it can cause false knock and pull out timing, which hurts the performance. I guess what I'm trying to say, is if you know you engine is up to snuff but think you could be suffering from false knock, how much of a benifit would this be to bypass the sensor, just for track use. Anyways just a thought.

 

Peope wir in a switch to lock up the conveter to gain a 10th. I know the GN people do it. Not good for the tranny, but its all the same with racing.

 

If you have determined you are getting false knock count and it is not real knock then yes it will and does work. If it were me i would use toggle Sw to toggle between a knock sensor, for everyday driving and a resistor for the track. This way you can get he performance when you need it with the saftey of a daily driver for the bad tank of gas every now and then.

 

Yes you can.

Jerris

 

If you think you could be suffering from false knock, why would you think that? are knock counts showing up early in the rpm band? Most of this stuff i'd think wouldn't cause any knock counts. as deep down in the side of the block the sensor is I'd think only maybe a loose fitting cold forged piston maybe would read false.

The GN guys rely heavily on the stock knock sensor setup to keep their grenades from blowing up.

 

im curious as well. what about a solid roller setup? Isnt that known to cause false knock?

 

The GN guys rely heavily on the stock knock sensor setup to keep their grenades from blowing up.[/QUOTE]

Spark knock on a boosted engine, my definition of living on the edge. Those pistons can "disassemble" themselves. You definitely lower cylinder pressure when a rod exits the block. My favorite is pieces of the block coming off with the pan. Nasty mess indeed.

I too love electronic spark timing.

dlmeyers 90 coupe zf6 3 speed shocks

 

No, I don't believe I'm suffering from false knock, although it's been awhile since I have datalogged my car. I have just been thinking about it since reading GMHightech this month, as they have a article about detonation and it was fresh in my MIND. Basically, as I mentioned above, I remember reading on one of the car forums of people bypassing the knock sensor at the track and gaining a few tenths, so I was just curious if anyone here has done it and had any luck, thanks.

 

I just run the LT4 knock module and haven't had any problems.

 

As you seem to know, when the ESC receives knock counts, it retards the timing. How much and for how long, depends on the quantity and volume of the knocks. Unfortunately, the ESC isn't a real sensitive closed loop device. Yes, after the knocking stops the timing will be restored, but the retarding isn't just barely enough, or for just long enough. The ESC overdoes it and any knock counts are to be avoided because the ESC over reacts to counts and exacts a higher toll than necessary.

If an engine, with the ESC disabled, is truly knocking it can destroy itself, if left unchecked. If an ESC receives false (or real) knock signals, the timing will be retarded. How much and to what degree the performance will be affected will depend in the severity of the signals (counts). Therefore, it is difficult to predict what the gains (if any) will come from disconnecting (or switching off) the knock sensor. In some cars, it will set a trouble code. If the ECM goes into the "limp home mode", performance may be further reduced.

Personally, my car was experiencing, verifiable false knock counts. Consequently, my knock sensor has been disconnected for about 5 years. Now, I detect knock the old fashioned way, I listen for it.

RACE ON!!!

 

Yes I agree, sometimes listening is the best route, but then again, sometimes the ear can be decieving, RACE ON

 

This may seem like a stupid question, but here goes anyway. Would open headers appear to the knock sensor as a knock? I am trying to decide on Hooker SC's, or TPiS's, but if opening the headers at the strip is going to cause such a huge problem, then I won't need flanges, like on the Hookers. I will get Random Tech high-flow cats w/true duals, and Flowmasters and tune it accordingly. TIA.

Rich K

 

There is a HUGE difference between knock and pre-ignition.

Most motors can live pretty long with occasional knock, however few will live long with the first onset of pre-igniton.

Knock is caused by pressure spikes in the combustion process caused by abnormal combustion, normal combustion happens in that the flame propoges from one side of the chamber to the other compressing the air/fuel ahead of it increasing pressure and temp in a "controlled" manner. When you get knock this flame propogatoin becomes unstable and the air/fuel ahead of the flame front starts to ignite under the pressure and heat spontaneously.

Conversely pre-ingition what people often mix up with knock or should I say pre-ignition effects are what people mistake for knock are devostating. Pre-ignition is caused by cross fire in the distributor or from a hot amber glowing off the carbon buildup in a motor that pre-ignites the charge in the cylinder as the piston is still traveling upward. This tries to drive the piston back down and you can imagine what that does when the others are sending it upwards,.

But knock is something that people greatly over-exaggerate. motors for YEARs ran without these knock sensors and with much WORSE fuel and heads/materials. Obviusly you should avoid knock if you do experiece is, as it can take its tole over time.

But if you know what your doing and do not try to get stupid with timing and lean on fuel you should be fine without the knock sensor. I say this as my finding are once you modify the motor you effectily change the frequency in which the motor's knock would occure anyways which detunes the knock sensors ability to pick up knock.

use your judgement, but also bone up on the causes and difference between knock and pre-ignition. Pre-ingition can kill the best running/tuned motor in a matter of a fraction of a second, if say you get distributor scatter and that spark jumps to the wrong post in the distributor. If you wanna see what it can do, I can send you a picture of my 1500 dollar billet crower rod!

 

Listening worked for an awful lot of years before knock sensors came along.



A clarification. KNOCK is the noise made when when two flame fronts meet in the combustion chamber. The forces of meeting set up vibrations in the engine metals. Pre-ignition is exactly as Jesse described. The initiation of a secondary flame front caused by the heat of compression (as in a diesel engine) is called detonation. Unfortunately, the terms, "knock", "detonation", and "pre-ignition" are, often indiscriminately, used interchangeably.

As an aside, higher octane gasolines burn more slowly, and inhibit or retard the combustion initiated by the heat, alone.

RACE ON!!!

 

Will if my engine exibits any of the above symptoms(knock,detonation, or preignition) I blame it on Jesse as he is the one that tuned my beast Hey someone has to be the scapegoat

 

Blame it on the Bossa Nova.

RACE ON!!!

 

You can put a toggle switch on the ground wire for the knock sensor module. This is the only way to bypass the knock sensor without throwing a code or SES light. It is located on the passenger side under the hood near the passengers door. This will allow full ignition advance so be careful! I installed it on my 89 because I suspected false knock due to my headers. I was correct and yes I did pick up over 1/10 in the 1/4 mi. I still have the switch installed but I don't use it much.

John