My buddy just recently purchased a lt1 355 and vortech supercharger from Alvin@PCMforless..They were running it speed density with a 93 PCM,however my buddies car is a 94.I thought I read somewhere that you should not use a lt4 knock moduel on a boosted application?Can someone confim this for me?...thanks

 

I'm sure someone will correct me if I'm wrong, but I believe that the lt4 knock module may not sense actual knock in boosted or sprayed applications. The lt4 had a noisier valve train. This valve train tricked the computer into thinking there was detonation or a knock. So GM put the less sensitive lt4 knock module in to keep the computer from pulling excessive amounts of timing from false knock. When you add boost to a high compression motor you run the risk of detonation if the computer does not retard the timing when actual knock occurs. I think it would be best to run your factory lt1 knock module to reduce the risk of damaging the motor.

 

The LT4 knock module is not "less sensitive" to knock. It is simply a filter that filters out the noise of the Crane Gold full roller rockers that were used on the LT4 engine. It should not filter the sound of true knock (detonation). I used one on my setup when the engine was basically stock, with an NOS 125HP dry kit, and the knock system continued to operate normally, as evidenced by the full-time knock retard display on my ScanMaster LT1.

 

So is it safe to still use the LT4 knock moduel on a supercharged motor?or use the lt1?

 

I don't see how it would not be safe to use on anything. It still picks up real knock, just like Fred said.

 

Tuners can accomplish the same thing without you wasting money on unnecessary additional hardware. Heard some good arguments the LT4 module was designed for the OBD2 system and doesn't even function properly on OBD1.

 

It would be interesting to see how they "filter" within the tune. You can adjust the limits, attack and decay rates, but I'm not sure how they would select the frequencies of the noise that is passed through or ignored. Maybe its in there... don't know.

I don't even run the stock PCM or a knock senser, but back in 97 I had the LT4, and played with octane, and the LT4 module still allowed the PCM to respond the same to low octane fuel as it did with the LT1 module.

 

Tunercat has added a lot of tables since 1997

 

We started it up today with the lt4 moduel and it ran great!!!!I think Fred and Shoebox should write a book on lt motors... Awesome knowledge..

 

http://www.ls1tech.com/forums/4164970-post9.html
http://www.ls1tech.com/forums/13682786-post13.html
http://www.ls1tech.com/forums/5123258-post7.html

 

Quote: Ed Wright, You do not want to use an LT4 knock sensor with an OBD1 PCM. No need to change the module either.
You can take care of any false knock problems when you tune the PCM.

Good luck, Ed

I have been using search to read up on this. This appears to be a common
swap that works fine for most people. Why does he say this?

I got interested after I tuned a '94 Impala SS Car was basicly stock Flowmasters on stock pipes and a CAI. the car owner swapped in a LT4
module as I was pulling the file from the car. I put timing tables in that I have
used on several cars like this with no issues. Driving the car it would pull timing just rolling into the throttle 6 -7 * WOT 3 -4 * Fuel pressure was good
@ KOEO and WOT fuel trims corrections 5 -6% I can not belive this is all real knock. It occured to me it might be the CAI messing with the MAF but I would expect the trims to be whacked if that were the case.

Also is there any scanner that reads MAF hz on an LT1?

 

I dont think Ed is saying it is bad to use one. Just that its pointless if your going to get a tune being it you can make adjustments then.

Sent from my Evo 4 using tapatalk

 

He seems to say that for an OBD1 pcm. The LS1 cars will have some KR @ tip in to
WOT but it is easy to get rid of with fuel. KR @ lower loads usally means too much
timing or lean and this car has niether.WTF

Are the burst knock values learned or constant in the knock module?
Would not a reflash reset any learned values?

 

Ed specifically said you do not want to use one in an OBD1 pcm, go back up and reread the quote and look at the links.