wrd1972

I have a highly modified LT1:
LE2 heads
LE 1.5 cam
CR is 11.2:1
All bolt ons etc.

I am chasing down knock retard at WOT, right now the LT1 KM is installed. When I install the LT4 KM I get KR all over the board including WOT. The Lt4 KM is simply much worse all around than the LT1 KM.

Does anyone know why this is, I thought the LT4 was supposed to be less sensitive?
I have two of them and they both do the same thing.

Is there a certain procedure to following when using the LT4 KM other than simply plugging it into the PCM?

Z06_BluByU

I have read about this problem before.. I think it had something to do with making sure you have it torqued to the proper setting.. (I think that had some control over it..) Also, I think they are installed dry..

rickneworleansla

wrd1972

Whoaa mule, are you referring to the knock SENSOR, I am referring to the knock module.

STL94LT1

What? The LT4 knock module just snaps in to the PCM.

I have been running the LT4 KM in my 94 for 5 years without a problem. It seems that occasionally there is an LT1 that rejects the LT4 module. Why, who knows?

rickneworleansla

Not to change the subject but I'd like to hear more about your mods. What numbers/ET's are you getting with the LE cam and heads? I'm looking to go a similar route. About the KN issue... Has it been on a Dyno for tuning?

wrd1972

I am looking for the answer to this question, there must be one.

Z06_BluByU

sorry.. case of type before read I guess...

tlong

You may want to throw this out in the scan and tune area. It don't make no sense in local Georgia jargon. My LT4 module replacement had no ill effects.

wrd1972

Here are the specs:
2 bolt block bored .030" over, lightly decked, align honed w/ threaded oil plugs
Melling select SV oil pump w/ GM white spring
Oil adapter bypass plugged w/ oil cooler removed
Mahle .030" 6" forged pistons
Scat 6" forged connecting rods
Reconditioned stock LT1 crankshaft
ARP main studs, rod & head bolts
LE2 ported heads
LE1.5 high lift cam
Comp 1.6 pro-mag NSA roller rockers
Comp chromoly 7.00" push-rods
LT4 ED timing set
ASP under drive pulley
LE ported intake manifold
52mm ported throttle body w/ LT1 aluminum cover proudly displayed
30# SVO fuel injectors
MSD coil and super conductor OTVC plug wires
AS&M cold air induction
RK sport mid-length headers
Borla cat-back w/e-cutout without cat
Aluminum drive shaft
Custom Kevlar clutch
4.10 ring/pinion
Madz28.com tune



Have not been dyno tuned yet, waiting for cooler weather. Have not been to the track either. The engine is very powerful and down right wicked if you get a good run with zero KR. When the 5 degrees of KR kicks in at WOT, it feels like it goes down 50HP.

When all is said and done I should be close to 400RWHP, the thing killing me is the KR.

I really think it is false, there is no pinging and no signs of detonation on the spark plugs. I dont want to zero out the KR tables until last resort. Again the LT4 does nothing but make the problem worse, this is aparently also the case with others as well.

Atok

Yep, I echo what you are seeing. On my '95 LT1 with 1.6RR the LT4 KM was terrible. I would get false knock just driving up a hill at 70mph in 6th gear. Install the LT1 module and no more knock counts (or very few). I was getting knock counts sitting in neutral in my garage with the LT4 module!

On my car I found the LT4 KM VERY sesitive. So after buying two new ones and having the same problem I went back to the LT1 module and sold off the LT4 modules. Everyone says they are less sensitive, but my experience shows otherwise.

AlHale

I am struggling with the same issue. I have dyno tuned the car and am now convinced the knock is real. I swapped lt1 KM for the Lt4 and got a very slight gain. Using DataMaster I am still getting 3-6 degrees of Spark retard at 4200rpm. Runs like a bear when the engine is still comiung up to temp. I am trying to locate 100-105 octane racing fuel to prove the theory that it is a real spark knock. I am putting LT4 composite Valve covers on it to lessen the chance of misread knocks. Will keep you posted on the results. Good luck and keep posting the results of your tests.

wrd1972

A little more info, I gt no KR when in open loop. Once in closed loop the KR is very hit and miss. You can be cruising then drop into second and get degrees of KR, do the same thing a few minutes later and no KR. Timing appears to be 36 BTDC according to the Scanmaster.

The last time a ran with 100 octane I saw no improvement in KR reduction. I just want to be positive.

STL94LT1

FYI: Your car goes back into open loop at WOT.

Carpenter

I'm not certain......but I seem to recall that member 69/427 was the designer (?) of the KM? Or had input in it's design? Anyways, do a search of his posts and you'll likely come across lots of info on the KM issue.

Hope I'm not giving you a red herring.......but I'm pretty sure (?) his thread was very informative.

Good luck.

wrd1972

I saw him make some comments, he stated that the LT4 was "less" sensitive. He also discussed the difficulties of detecting false vs. real knock. I also sent him a PM to post a current comment to my initial question.

Carpenter

Well.....best of luck.

(The good news is I wasn't imagining him! )

gslotman

Agree with STL94LT1 - I had 22 degrees being pulled out of my motor (95) with the LT-1 KM in place and less than 5 with the LT-4. The biggest difference though was getting PCM "tuned". Until you get that done your going to be all over the board

69427

Hey guys,

Just happened upon this thread while borrowing a computer. (I'm visiting family at the moment.)
The LT4 module is designed to be less receptive (versus the LT1 module) to vibrational noise spikes generated in the engine. The fact that some individuals are seeing somewhat "opposite" performance using the LT4 module is certainly curious. The electrical specs of the two modules should not allow this scenario.
As I mentioned earlier, I was the ESC calibration engineer for the LT1 (and the later LT5 years). I transitioned to a design group prior to the LT4 introduction, so I I can only refer to the spec sheet (or my memory, at the moment) when discussing LT4 issues.
Piston slap and valvetrain noise often produce frequencies similar to knock noise frequencies, hence the need to reduce the sensitivity of the ESC module to eliminate the occurance of mechanical noise being interpreted as detonation. Aftermarket pistons and valvetrain components can produce a very different noise signature for the engine, but I would expect the calibration sensitivity trend of the modules to be consistent.
An oscilloscope plugged into the sensor line is the easiest way (for me) to determine if the signal is knock or mechanical noise. It also helps to be able to modify the spark advance and A/F ratio while the engine is under load. Unfortunately, this isn't practical for most tuning sessions.
There are a few ways that the signal can be modified for testing, and I'll try to make a list of ways to do that. Hopefully this would help make troubleshooting a bit easier. Some high octane fuel, and a way to retard the spark a few degrees would also help in the debugging process.
Sorry I don't have any quick answers here. Without actually getting to see the sensor signal I can only speculate at this point.
I'll try to keep in contact while I'm on the road.

rickneworleansla

Sounds like a BA machine you got there. Call some of the tuners PCMFORLESS, Madtuner, etc., maybe this is something they have seen before. Also try posting this problem on the CamaroZ28 forum under the tuning or advance section. I'll try searching to see if I can find some info on this.