ice95z

iTrader: (10)

Through out my searching on various topics, I have come across many people who shut off or eliminate the knock sensors? Why? I have a few buddies with some fast cars...a 10 sec Grand National, a 10 sec Talon DSM and others and they rely on their knock sensors to let them know if there is a issue. If the knock count gets too high they get out of it before melting the engine. I know its not the same platforms but the knock sensors in all the cars play the same role. Why eliminate something that could potentially save your engine?

HOTROD NETWORK

iTrader: (1)

Some people run solid motor mounts and may give false trigger to the knock sensors,Also noticed when the exhaust is close to the frame it triggers them also.

soundengineer

iTrader: (16)

incorrect.....


people Just dont know how to fine tune knock sensitivity so they do it the easiest way possible, which is to turn them off..

most people also dont know how to tell the difference between real knock and tip in knock(which is calculated...not heard by the sensors)

I run a 252/274 cam with knock sensors and no issues.
also running a Motor plate and mid plate with a Poly trans mount...
I never had any issues with my sold motor mounts before I did the motor plate and mid plate

if somebody tells you that you cant use knock sensors with a certain combo... its because they dont know how to tune them to work with that combo.

soundengineer

iTrader: (16)

and for the record....
if it knocks.. its usually too late...
the stock pcm doesnt correct fast enough or heavy enough to save your motor...
it does however correct enough for a basic engine with minor issues of a tune that is not quite optimal.

Camaroo1

Only reason anyone would shut them off is pure stupidity, like stated above even with them on bad things still can happen. With them turned off its a sure bet pistons are going to become part of the exhaust system.

zzcamaro00

Or your running race gas

soundengineer

iTrader: (16)

you are really stupid if you think that "running race gas" will keep your motor from knocking...

predetonation is caused by many factors...
many of which care not changed by the simple fact that you may be running "race gas"

Roger Blackmore

Predetination??

soundengineer

iTrader: (16)

should have used the Term.... Knock, Pre Ignition....


you want "Detonation" to occur at 14-30 degrees after top dead center

anything before that would be "Pre-Detonation", or Pre ignition, or knock.

and if it happens before TCD, you break **** inside your engine..LOL

Roger Blackmore

Pre ingnition and detonation (knock) are 2 different things I believe.

soundengineer

iTrader: (16)

correct....

A cause of pre-ignition might be a hot spot in the cylinder from a chunk of carbon or a damaged spark plug or heli coil end, a burr of some sort that sets the charge off when it reaches a heat and compression point that is prior to the desired ignition time.

Detonation is due to high temp and most likely improper mixture that instead of igniting and expanding in the desired manner to push the piston as it travels down the cylinder on the power stroke just explodes at once. You have to think of the whole process in ultra slow motion. The ignition normally happens around 20 degrees before the piston reaches top dead center and by the time the piston does reach TDC the charge is expanding rapidly to push the piston down. With detonation the mixture charge explodes and is quickly over with. There's power loss and the hammering against the still advancing piston is really tough on the engine. So tough in fact that it can completely destroy it in a short amount of time.


but both are bad..
knock sensors will not save your motor from Pre-ignition(though they will usually register when it is happening)
and race gas will not prevent Pre-ignition

Race gas can help with Knock....but only to a certain point...
the Higher octane is harder to ignite,which means it ignites later and slower.. which means that you add timing back in to get it to ignite sooner to achieve the same ignition point that makes the best power after TDC....
the Higher octane rating also means it holds more potential power..

Race Gas does not eliminate the need for knock sensors

Roger Blackmore

Correct. I posted my 2nd comment so as not to sound like as *** with my first comment. Lol.

Taspeed

iTrader: (1)

ding ding ding!!! That sir is the money shot, and as true as it gets.

mkvamso

iTrader: (2)

People turn them off for a few different reasons
They can pull timing to retard knock in an effort to keep an engine from damaging itself from detonation but can sometimes step in when not wanted. If you have cheap headers that hit the block sometimes theyll pick up "knock" and youll lose power.
Nitrous guys will pull them sometimes and tune from the spark plug rather than knock sensors when setting timing.

soundengineer

iTrader: (16)

again... read my post.....
there are no reasons to turn off knock sensors...
you just need to learn how to tune the settings for them.

headers resting on the block, wont cause knock...its not even the same frequency that the knock sensors are looking for.
LS1 sensors look for an 11.1 kHz sound, and look for a certain amplitude...

LS3 style sensors look for a lower frequency around 5k ish...


in both cases, you can add a simple bandpass filter to the signal wire if you understand a little about electronics...which will remove almost all problems with false knock casued by other noises.

zzcamaro00

hey man i didnt say it wouldnt. its kinda hard to knock on race gas, but you can manage to make it knock if your not tuning right. cheesh chill out. there a lot more people asking stupid questions and making stupid statements.

KissMyTushZ28

iTrader: (4)

Hey Scott(soundengineer). I'm having a situation with my 99 T/A(check sig\/) where my SES light will come on and stay on for a few short trips(30-45 minutes if constantly driving) then it will go off. It has done this twice. I checked the codes and it is a Knock Sensor Low Voltage Bank 1 code. Would that be that the ground is just having a bad connection, a short, or what?

Roger Blackmore

What ever you do, don't turn them off

soundengineer

iTrader: (16)

the sensors ground thru the block on an LS1

one of 2 things...
either a bad sensor, or a bad signal wire...

pull the intake, check the wires for continuity with a multi-meter
do a visual inspection of the wires for cracks/breaks/burn spots/bare wire

if you have no signs of the wire being bad, replace the Sensor in question(the front one is bank one)..
if that doesnt solve it, then buy Knock sensor wire harness

both items can be gotten at a GM Dealership for reasonably cheap

I personally would Just do them both because its easier to only have to pull the intake once.

soundengineer

iTrader: (16)

actually, its not hard at all to make it knock on race gas...
most people think they can just add it to the tank and all will be fine...
which is not the case... there are a lot of things that can create a situation where knock will be present

one of the most common things people do wrong, is they put in race gas for nitrous, and they dont check to see if it actually helped...
lots of people put it in an already partially full tank, which really negates the benefits, especially if they dont get a good mixture of it before they make a run....
have to get all the lower octane fuel out of the fuel lines before you actually get to the good stuff, and its only as good as your mix between what was in your tank and what you put in.

you can add it to a stand alone, but its still only as good as the mixture it creates. and your main fuel tank is still the majority of the fuel mixture
think of it this way...lets say a stock LS1, makes about 300 HP
so you now have 300 HP of regular gas...
then you spray a 150 shot of nitrous...which requires the amount of fuel for that 150 shot...
so you have 450 HP of fuel, 2/3 of which is normal gas
that doesnt sound all that safe to me



and it doesnt make a lick of difference if you have other issues going on anyways.