Just finishing a 383 build on an L98. I have not reinstalled the knock sensor into the block and am considering using a plug or drain instead and eliminating the knock sensor altogether.

Surely some body else has done this. With what success? What about ski, cfi and all of you that are runnig highly modified engines. Any experience to shed on this topic? Thanks in advance.

 

The ECM tests the knock sensor once after startup and wants to see a knock count. Maybe this feature can be disabled with a chip mod??

 

Is there a particular reason you want to disable the knock sensor? It's not a bad thing to have on a brand new motor, at least until you verify that you aren't getting any real knocking.

I was seeing a lot of false knock counts in my '87 (also a 383), so I installed the upgraded ESC module and the counts came WAY down (only 1 or 2 every now and then). Check out this tech tip:

https://www.corvetteforum.com/techti...D=99&TopicID=2

If you want to eliminate the knock sensor, I believe you can install a resistor (not sure how many ohms - I can verify later if you'd like) on the wire between the knock sensor and the ESC module which will keep the ECM from throwing any codes.

 

I don't understand why you would want to eliminate them since they protect your engine. If you feel they'll cost you power they won't, unless you have a problem that isn't dealt with. This is one of the greatest features of an electronic high performance engine in my opinion, since detonation during severe use can destroy your engine in a heartbeat.

 

After testing my stock 90 6 spd with a Diacom I found that the dual mass flywheel was fooling the knock sensor during shifts into thinking the engine was in a knock condition. The ESC took out a lot of timing and it is very slow to return. Tired of losing power I tried every trick to desensitize the knock sensor until my research found out the ESC circuit is frequency dependent not amplitude sensitive.

As an experiment, I had a chip burned without the knock sensor active. My first weekend out with the chip at Thunderhill, I was black flagged during the first session. In the pits I opened the hood to find oil and every valve cover plug blown out!! To make a long story short, I had cracked ring lands on three cylinders. The stock Hypereutectic piston alloy is not very strong. I had encountered knock and never heard anything. No pinging, no marbles in a can, nada, just a blown engine. This by the way was on a 50/50 mix of 94 and 100 octane gas!!!

Learned my lesson the hard way. Turning point in converting my 90 into a race car. Wound up building a killer motor as a replacement.


Larry

 

You really don't want to do this.... a previous owner of my Vette had disconnected the sensor and tied the pigtail against the frame (so I know it was deliberate). When I first got the car, I was getting occasional knock under heavy acceleration until I found this problem. Later, when I disassembled the motor during a rebuild, I found a broken piston skirt and several broken rings. And the cylinder with the broken skirted piston was not a pretty sight...
[RICHR]

 

If the chip is tuned for no knock sensor you can get away from it as long as your careful about tuning. Read the plugs, listen hard for knock and make sure it always has enough fuel.

My car is going on 3 years without a knock sensor.

Mustangs didn't get knock sensors until 96 I believe, I know 95's still didn't have them.. Carbed cars don't have knock sensors. Life is possible without a knock sensor.

 

I'm still catching my breath from laughing my azz off. OK. We can proceed now. My 1984 Crossfire not only has a totally stock long block, it is all original. It has never had any internal repairs. Its never even had a head off. That said, I agree with the others as to the value of a working ESC system. Keep it if you can. My engine was generating a large amount of "false knocks". Rather than track down the cause, a formidable job, I perceived, I disconnected my knock sensor. I have tuned, and over tuned, my car. I have assured myself that I can hear when it is pinging. For me, it works fine, but I wouldn't recommend it for just anyone, especially if they don't know what they are doing, and EXACTLY why they are doing it. Kind of like a 160° thermostat.

RACE ON!!!

 

I've seen a few engines detonate themselves to death. Not pretty. You would be nuts to remove them.

 

I've seen a few engines detonate themselves to death. Not pretty. You would be nuts to remove them. One batch of bad fuel and you might end up replacing a few pistons.

(Sorry for the double post....DSL hicup)

 

I did it for consistancy. When I was bracket racing the difference between my absoulute fastest, and absoulute slowest run of the day would be less than .04 out of 12 or so runs. I tried eliminating all the variables.

Like I said before, there was a time before knock sensors and everyone wasn't blowing thier motors up then.

Do I reccomend it to everyone, NO.

 

There is an "optimum ignition point" and is dependent on several factors. Spark control is designed to keep the timing advanced as far as possible and backing it off with the onset of detonation.

If you hear spark knock, you are deep into detonation. Cylinder pressures well above the desired level can occur WITHOUT your noticing this problem. A properly functioning electronic spark control system is highly desirable. They are very good at firing spark at just the right moment. They compensate quite nicely for variations in fuel quality and operating temperatures, RPMs and cylinder loads.

If you really want to understand timing and the importance of spark control, head down to Barnes and Noble, find David Vizards Volume 1, How to Build Horsepower, ISBN 0-931472-24-5, and head for around page 95 and enjoy. His explanation and graphs are the best I've seen explaining the complex process of combustion.

I ususally find a comfortable chair and read for free, however this book was worth the price, $18.95.

Keep the greasy side down.

dlmeyers 90 coupe zf6 3 speed shocks

 

If you're concerned the knock sensor might be overly sensitive, check out the tech tip on upgrading the spark control module for '85-'89 models.

 

but thats a mustang, a corvette is a real car

 

Sorry did not see this thread for a while.

Here is my take on it. With a modified motor, away from stock CI, roller rockers, definately if you put a solid roller, or even Headers - you will most likely trigger the knock sensor at some point.

The way a knock sensor is configured/designed it is tuned a sensor that looks for a specific frequency. This frequency it's looking for is specifically designed for the motor by engineers in its stock form. So one can imagine, that this frequency could dramatically change with ANY change from the stock motor. IE, a forged crank, larger bores, etc. What I am getting at is there is a VERY good possibility that you have already circumvented the knock sensor with the changes you have made.

On a similiar application I have engineers at work designing resonate ultrasonic testing equipment for inspection of OEM cam caps for inspection purposes. These units can VERY effectively and quickly detect unseen cracks in our product. However like your knock sensor, very subtle changes in density and material composition makes keeping the database accurate, where they do not either pass bad parts or throw away good ones a NEVER-ENDING battle.

Also for years and at nearly every strip around you will not find guys running a knock sensor. I have not had one for years with no issues.

You need to know how to read plugs, listen for ping and get out of it immediately, and run decent gas.

So in summary my opinion is that 90% of the people out there with modified motors have already made their sensor either more or less effective by changing the motors configuration. This is something that is going to be VERY difficult to put your finger on and each application would be different. I would get that even running different degrees of coolant vs water percents would have an inpact on how and when the knock is picked up. I am sure and have read the range of frequency and its pretty wide. But you get the idea.

If you want to get real tricky(well not tricky but), you can have the chip tuned so you can still use the sensor, but it will not remove any timing. This does a few things. 1 you will not have a check engine code, and you can still see knock if it happens on the logs. But remember the ECM will not pul any timing.

Hope that all helps!