Knock Sensor Tech "Topic of Week! 2/12/2012"

We seem to have plenty to keep us busy but I wanted to try a topic of week. If you have tech info and part number for knock sensors post it up!

Since we haven't ever really got into knock sensors and there are lots to choose from maybe this can end up with all information gathered as a FAQ type thread.

I'll start because I don't know the answer to which Knock Sensor I should get for the IH TBI conversion in progress on my sons truck. It is a 16197427 PCM that came with $OE 4L80E trans. I have the same Memcal in it that came with it but a G1 adapter and 27s512 chip from Moates.

For those who don't know the knock module is in Memcal, older C3 had an ESC on engine.

My son works at Oreillys Auto Parts and looked it up tonight for 1995 Chevy 1/2 ton and came up with 2 part numbers for Borg Warner
S8011
S8012
I forget which was which but one for auto and one for manual. Since it was a Auto Memcal I'm thinking it would be correct, but he is running a manual trans $OE now.

Have him also look up one for an application that is known to definitely have a '7747, and see if it is the same as one of the above. Then use the other one which will probably be for an Auto.

Just like AutoZone: for 5.7
SU154 - '88-90 both trans, '91-95 man. = '7747
SU169 - '91-95 auto only = '6395, '8625, '7040, '7427

I have a feeling that this will also tell us the answer to the question of a '95 5.7 man. '7427. It may not exist. If they say a '95 manual uses the same KS as a '7747, then a '95 man. ?must? be '7747.

ac delco part # 213324==manual tranny==s8012 borg warner==su154 autozone
ac delco part # 21392==auto==s8011 borg warner==su169 autozone

i always go through rockauto.com and look up parts. they usually give descriptions.

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Originally Posted by gregs78cam

Have him also look up one for an application that is known to definitely have a '7747, and see if it is the same as one of the above. Then use the other one which will probably be for an Auto.

Just like AutoZone: for 5.7
SU154 - '88-90 both trans, '91-95 man. = '7747
SU169 - '91-95 auto only = '6395, '8625, '7040, '7427

I have a feeling that this will also tell us the answer to the question of a '95 5.7 man. '7427. It may not exist. If they say a '95 manual uses the same KS as a '7747, then a '95 man. ?must? be '7747.

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Good point! What we keep seeing is 5.7L manual always comes back as a C3 ECM... already called and he's looking it up.

I spent an hour or so searching for differences in GM knock sensor frequencies and this is all I could come up with... unfortunatly can't find a copy of the SAE paper.

For a background on knock sensors, read SAE Technical Paper Series 900488, Combustion Knock Sensing: Sensor Selection and Application Issues
Authored by Steven M. Dues, Joseph M. Adams, and George A. Shinkle: Delco Remy Div, General Motors Corp.
In the mid '90's, a GM engineer sent me a list of GM sensors, showing part numbers, resonant frequencies, parrallel load resistance, and mounting style.
At the time, they were producing sensors in these frequencies: 5.2kHz, 6.0kHz, and 7.0kHz.
A chart from the SAE paper shows that the fundamental frequency of a 75mm bore is about 7kHz, a 94mm bore is about 6.0 kHz, while that of a 110mm bore is about 5.2kHz. The chart shows a fairly linear relationship of frequency to bore diameter.
The paper terms the GM sensors to be "broadband resonant", with "bandwidths approaching one thoundsand hertz".

I went through this when I did my 7427 swap. It also showed 2 diffrent knock sensors. One had a white connector, the other one was black.
The one with a white connector was what it said was for a manual trans, it also was the exact same part number as the one that came up for the 89 7747. I already had it installed for use with my 7747.
The black one was what it showed for auto. So like mentioned above, but be a ECM-PCM thing. With the manuals using the older style knock sensor.
I believe it had something to do with their ohm readings. I pulled one of the black ones from a JY vehicle.

But the knock sensors are useless for me. I get thousands and thousands of knock counts, even back when I had so little timing, a knock would have been impossiable. Changing ESC modules didnt help any. I kept them instaled, but had retard turned off and have made my whole timing map by ear.

You just have a noisy motor I guess. There was some testing by Grumpy and found the ESC made some differnces. I did read a paper about knock sensor placement in block and block metal resonence. Said placing in center of block closer to head was optimal. Duh! But never mentioned in water jacket where I think all GM sensors are?

I mounted the 7747 KS in the block coolant drain plug hole on the drivers side. The threads were the same as the plug that was originally there. Its kinda low and centered.
The black one I pulled from the junyard had longer regular threads (not pipe threads) and was in a head. So I put it in a un used hole in the block closer to the front of the engine, still on the drivers side. No diffrence in knock counts when I went to that KS and the 7427. Mabey one day I will play with diffrent locations.

Head is suposedly bad spot. What car had it there?

Wonder what would happen if you mounted 2 knock sensors? One on each side of block? Probably mess up reading but could change wire from one to other to see if one side is knocking or producing less noise so knock works better?

My Camaro has crazy knock counts when cold due to the forged pistons, and at certain rpm when warm I think due to the link bars between the roller lifters, you can actually hear them under the manifold at an idle.

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Originally Posted by EagleMark

Head is suposedly bad spot. What car had it there?

Wonder what would happen if you mounted 2 knock sensors? One on each side of block? Probably mess up reading but could change wire from one to other to see if one side is knocking or producing less noise so knock works better?

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A 4.3 Memcal uses two sensors, if you want to have two going all the time.

Knock sensors on my engine are worthless, due to cheap roller rockers.

It's the black one, you need for the V8 Memcal or two of them for the 4.3 Memcal.

93, are you saying that cheap roller rockers cause knock sensor problems? HMMMM I was looking at a set of full roller stainless rockers for my rebuild, maybe I should rethink that.

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Originally Posted by 93V8S10

A 4.3 Memcal uses two sensors, if you want to have two going all the time.

Knock sensors on my engine are worthless, due to cheap roller rockers.

It's the black one, you need for the V8 Memcal or two of them for the 4.3 Memcal.

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Are you saying this could be incorerated into a V8 16197427 built EFI system?

My LT1 has 2 knock sensors and the knock module is built into PCM. Thread with pictures in this forum. I was wondering if that module could be incorperated as some have used it in TPI ECMs.

Interesting!

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Originally Posted by jim_in_dorris

93, are you saying that cheap roller rockers cause knock sensor problems? HMMMM I was looking at a set of full roller stainless rockers for my rebuild, maybe I should rethink that.

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To be honest, I don't really know exactly why I can't get a knock sensor to work with my engine. At this point, I have assumed the rockers to be the culprit.

Quote:

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Originally Posted by EagleMark

Are you saying this could be incorerated into a V8 16197427 built EFI system?

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Maybe, remember I don't have a working knock system. I do have a 4.3 Memcal with two sensors that are hooked-up. You would have to experiment.

I think it was a 4.3 astro van that I got the knock sensor from. I didnt see a 2nd one, but its not like there is a lot of room to work with on those, even with the inside cover off. I could have overlooked the 2nd one. But I saw that one, so its not like I kept looking after I found that one...lol