Bones232

I've been tuning WOT lately. It seems I'm having trouble sorting things out. My AFR runs 11.9 pretty steady up through 3600rpm but my egt's shoot through the roof (see attached WB log). Usually around 3600 I start logging 5-10 knock counts (not suprised when running 1700degF). I have pulled tons of timing out in an attempt to eliminate the knock without success. Timing at 3600 @ 100map is 10d. The car is a dog and still knocks.

Anybody have any ideas?

*Please note that the user1 series in the attached log is the map voltage.

Fast355

iTrader: (2)

You are actually burning 1 point to rich for my taste. Rich + Late = Still burning on the way out and added heat.

RBob

iTrader: (1)

The knocking may be from the forced knock test. The ECM will run this test after each engine start while in PE (WOT) mode. Once it passes it won't run again until the next key-off, engine start cycle.

Have you made two runs without doing a key-off cycle? If not try it and see if the knock is gone on the second run.

As the engine has been rebuilt, is the compression ratio too high?

Can you hear it knock? Maybe false knock is fooling the sensor.

RBob.

gcpoland

iTrader: (18)

Many people think that the leaner you go, the higher the EGT gets. This is incorrect. Peak EGT occurs at stoichiometry- about 15 to 1 for our purposes. If you go richer than 15 to 1, EGT will drop and if you go leaner than 15 to 1 EGT will ALSO drop. It is VERY important to know which side of peak EGT you are on before making adjustments. It is safe to say that peak power will occur at an EGT somewhat colder than peak EGT.

It is really the AFR that is important, not the EGT. Most engines will make maximum power at an AFR of between 12.0 and 13.5 to 1 however, the EGT may vary from 1250F to 1800F and is dependent on many factors.

After you tune for the correct AFR, then watch your EGT and fine tune for peak, power. This allows you to retune the car using just your EGT s/u, when you are off the dyno.

**Some info taken from Simple Digital Systems

Gary
Kingston,NH

Bones232

Thanks for the input fellas...

I am using the forced knock patch ($61). I do not hear any audible knock. Although the motor's pretty loud @ 3500. The car seems to knock more in the lower gears (1&2) when the RPM is increasing quickly. Sometimes in third I can squeak by with only 1 or 2 knock counts.

As for AFR vs EGT, I'll pay more attention to the AFR and use the EGT as a fine adjustment tool as gcpoland suggests.

Thanks again
Bones

Grumpy

I wouldn't say AFR is more important the EGT.
EGT is how close you are to the thermal limits of the motor. Run 1,800dF on a SBC, and you better have Ti valves, or be ready to start replacing parts..

It takes a both EGT, and AFR to know where you are.

Not to mention timing plays a roll in BOTH.

Yes, EGT peaks at Stioch, and as mentioned you need to know for absolute sure which side of the curve your on. And with some of the weirdness in gas lately, I'm less and less confident in just how accurate AFRs from day to day.

Bones232

While looking over some logs, I noticed that the PW in the 3100-3400 rpm range (same area as the knock) drops momentarily and then recovers. Both VE tables are continuously increasing in these areas as well as WOT afr's.

What else could cause the PW to drop in PE?

The first highlighted section is a 3rd gear pull and the second pull is a 2nd gear pull.

Z69

I've had motors knock hard enough you could feel the car slow for an instant.
But you can here that usually, or I can at least. That really depends on the car.

Notice your map dips too. I wonder what your not seeing with that slow aldl of yours.

Are your PE vs RPM and PE vs temp smooth in that area?

IF you have knock with only 10d, you have another problem.
Put the SA back to a reasonable value.

RednGold86Z

iTrader: (1)

10 degrees is killing you. Are you sure it's real knock? Have you tried higher octane/boosters, cool thermostat, whatever?

8 knock counts is nothing, over that amount of time. It's probably false knock or at least insignificant, and it's probably not retarding much, if at all. Put a normal spark table back in there, and measure your EGTs before you burn up the valves or eat the seats.

RBob

iTrader: (1)

Bones, what BCC did you start with?

The reason I ask is that I recently discovered GM used several variations of the code on the $61 ECMs.

This affects where the forced knock bypass patch goes. I made the patch on the ANLU code, and had no idea that there are other versions of the $61 code. One that I found to be different is the AXKW code, which is an f-body release. So the patch as I wrote it will not work properly with that BCC.

RBob.

Bones232

Does 'ANTT' sound right? It was labeled on the exterior sticker next to the service number. The label attached to the daughter board next to the memcal chip did not have anything other than a barcode on it. I have always modified the original bin.

I agree the 10d is not good. I was basically trying to rule out SA as a source of knock. I'm leaning more towards fuel delivery and/or false knock. I have since increase SA considerably.

My VE tables are pretty smooth in that area (see attached). My AFR vs RPM is fairly smooth as well;
4000, 12.00
3200, 12.00
2800, 12.50
1600, 12.30
800, 12.30

When the knock occurs, I can definitely feel something going on. The motor will hesitate for a moment. So far I've noticed that the PW dips in this region, egt's are high and WB reading doesn't spike or even move all that much.

I guess the next step would be to output the SA to my aldl stream and hope I can see if any timing is being pulled. Your right though, I miss so much with the aldl.

RBob

iTrader: (1)

ANTT is OK, it is the same code as the ANLU BCC.

There is a answer for that too.

RBob.

Bones232

I new that was coming I shouldn't complain though, I know what the fix is. cough cough EBL cough!!!

Anyways, I noticed my map reading on my WB during WOT runs peaks between 2400 to 2600 and dips between 3300 to 3500. The average kpa readings are as follows;
(2400-2600 rpm) Peak: 102 kpa
(3300-3500 rpm) Low: 96 kpa
Everywhere else: 99 kpa

Are these peaks and valleys within acceptable limits? Is the low a sign of some sort of restriction? If so, why only between 3300-3500rpm? Or is this just the normal resonance of the motor?

*Again, the user1 graph is the map voltage.

RBob

iTrader: (1)

Thinking here for a minute. If the PROM only has a bar code we don't really know if it is the original or not. IOW: ANTT or something else. I just uploaded ANTT (stock) to Craig's site:

http://www.moates.net/files/1)%20Sto...aries/antt.bin

Download that and compare it against what you have. The calibration section will have differences. Once past address $569 everything needs to be the same (with the exception of the knock patch).

As for the log I've never seen a MAP sensor do that. It just doesn't look right. There may be some kind of resonance in the intake. Can you feel a differece in the engine during those RPM sections?

RBob.

Bones232

Sure do. When i get to the 3300rpm range the engine feels flat and sluggish. Once I get through that rpm section it seems to pick back up again.

Are all map sensors created equal? I have one from a 4.3 I could use to rule out the sensor being bad.

Thanks for the info on the antt.bin. I will compare it tonight when I get home.

RBob

iTrader: (1)

Not all MAP sensors are created equal. Even amongst the 1 BAR's.

Check the hot stamped 3 digit number on the left side above the connector. The common EFI #'s are 460 and 039. They are darn near interchangeable (very slight difference, I've interchanged them).

RBob.

Bones232

Ok, up date time. I've been fiddling around trying to figure out what's going on with my knock counts at WOT.

Since my last post, I have found a couple of things contributing to my WOT troubles. The first problem was that my VE1 table was not configured correctly in my xdf file. Once the table was corrected, it was immediately obvious why my PW was dropping around the 3200 rpm range. The PW looks much better now (at least more predictable), however my WOT knock count continues.

With the PW looking better, I am now concentrating on the SA looking for patterns. One thing I have noticed is that I get an odd reading at or just after knock occurs. It has happenned more than once, but not every time. When the anomally occurs I'm getting a raw SA of 65533. Is this what knock retard looks like? Can anyone explain this?

I have attached a snap shot to help illustrate my thoughts.

RBob

iTrader: (1)

Timing went to ATDC. To calculate the timing subtract the above number from 65536.

65536 - 65533 = 3, for -1 SA

RBob.

Bones232

Thanks, that makes sense.

Did you happen to notice that I only registered a single knock count before the timing went limp? I have the 'min knock counts to do retard' set to 20. I wouldn't expect to see any KR.

My main SA table is pretty flat in those areas. I have my PE SA adder table and slope above 3600 zeroed out.

I also double checked to make sure my SA table is configure correctly in my xdf. As far as I can tell it is...

Any ideas?

RBob

iTrader: (1)

The knock count in the ALDL stream is only the upper value. It takes 256 counts to get 1 on the ALDL stream. The other fun part is that the knock sensor uses a 1msec pulse resolution to the ECM. That means the knock count basically jump in 64 count (+-) increments.

RBob.

Bones232

Time for another update. Its been awhile and I have done lots of tinkering and I believe I've made some progress.

First things first. This knock retard thing was driving me completely crazy. No matter what I tried the knock continued. So I began a quest to prove weather or not the engine knock was false.

I have already set the timing to a ridiculously low setting with little to no effect on the engine knock.

The second task was to look around the engine compartment for potential false knock generators. I never like how much noise my alternator made so I replaced it. Still knocked.

Next the old partially siezed smog pump was eliminated. Still knocked.

On deck was the exhaust. The entire system is free and clear of any body parts to rub against. I did however, find an exhaust manifold gasket leaking profusely. Still knocked.

At this point I was out of things to eliminate, replace or fix that could remotely generate a false knock. However I still suspected that the engine knock was false (mostly because I've never heard an audible knock). So now I was out of physical things to check and growing quite frustrated with the whole thing. I think at this point I grew a pair and decided to gradually turn down the knock retard in the problem areas, namely the 3200 rpm range in WOT.

After many white knuckle runs the knock retard was completely inhibited. And what do you know, still no audible knock. Oh yeah, the car would pull straight through to redline also.

With the engine pulling through the entire rpm range it was time to actually begin some serious WOT tuning. I found the EGT/AFR combination an excellent tool in tuning WOT. It seemed the trick was to first get the afr in line and then tweak the timing table until the EGT falls to desired levels.

I am by no means telling people that this is the way to tune WOT, I am just documenting my experience with my engine. I am still a novice tuner experimenting with what I've got.

Attached is the latest WOT run. AFR and EGT seem much better than before. The car pulls fairly strong and is much more enjoyable to drive.

A couple of things I noticed while tuning WOT;
1. SA seemed to effect EGTs more than the afr
2. knock retard sends your EGT through the roof.

With the car running better, I can focus back on the cause of the engine knock. I've heard that the valve train could sometimes cause false knock. I'm not sure why or how to determine that though.

I am also skeptical of the well being of my ECM itself. One morning on the way to work the knock retard went nuts. Every time I would give it gas, the timing would retard so much the car would actually slow down. I stopped, shut the car off, restarted it and it was fine (weird).

Well, back to the garage....

sully91rs

Hmm. So you're saying the ECM is picking up some false knock? I am having similar issues myself. After driving around for a while the knock retard starts kicking in. I believe I have a leaky exhaust, but you mentioned that you fixed your exhaust leak and still picked up knock counts.

Any more ideas for the false knock?

Bones232

I'm still not sure what's causing the knock. I am now running a different ECM, but have not been able to log a WOT pull yet to see if it made any difference.

Other than that, I plan to look for potential causes this winter when it's in the garage getting it's annual up-grades

dimented24x7

iTrader: (2)

Id zero out the knock tables, put 20-30 degrees total, depending on the setup, and slowly work your way up to WOT over several runs, and listen for knock. If the EGTs are good and there isnt anything audible, then it may be false knock. Also, are you using the right KS? The later model ones with the internal resistance will register lots of false knock with the stock module.