You'll know I'm a beginner soon enough

I'm happy to report I've finally had success with my aldl cable and have been able to log some data.

The situation (MAF Car, L98, ZZ4 cam):
As I accelerate
LV8 153
O2 48.8 mV
BLM 122
INT 128
Vehicle Speed 26mph
RPM 1825
Spark Advance TDC 17.23*
Spark advance Rel to Ref Pulse 39.38*
Base Timing 6*
Knock Retard 8.4*

The question:
Is the solution here to go into the advance vs LV8 table and retard the entry by the amount of retard (8.4*) and log again? And then, subsequently with every incident of knock retard?

I told you I was a beginner!

 

First take out the ALDL spark adder (in the bin), then repeat the test. It should be at start address of 23 (and a multiplier of .3515625, but you're gonna zero out the number anyway). I'm assuming your cable has the 10k resistor in it, which causes this problem. The factory code puts 10 deg extra (I think it was 10, mine's 0 now), when in ALDL, which I think was a way to check knock sensor function without another special mode.

 

So, if I read you correctly, you're saying that the equipment is at fault? Yes, I have the 10K in the cable, but I disconnect it as soon as the connection is made to the ecm.

Could you walk me through the procedure you just described? Start address 23? . Thanks

 

If you disconnect the 10k, then it should come out of the special mode. But just to be 100% sure, I'd still zero out that value.

If you're using Tunerpro, you can easily add an ECU item. The address for the spark adder in $6E should be 23. Look at some of the other ECU items to get a feel for what the values mean.

Do those timing numbers add up? Looks a little strange. Which tables did you start with? ARAP tables have too much timing for almost everything. Stock iron head L98 tables would be a safer place to start. Leave the coolant temp spark advance correction stuff alone for now, and just stick to the main spark advance table (yes, the one you're referring too in the first post) and the PE spark advance table.

Since you say you're a beginner, have you set the actual base timing to 6* or is that just the table value? They should both be set to the same number. If they're not set the same, that could the source of all the knock. If they are, then, happy tuning!

At low RPMs and high load, not much timing is usually tolerated, as you can see. Really calibrating a full table is kind of an impossible thing to do on the road, so don't expect to see night and day differences with a 1-2* change. Try to keep most of it out of knock, but don't worry about a few degrees of retard at tip in (distributors aren't very accurate). Don't tune to the knock limit at all places, either. If it's only for street fun, don't push your luck too much.
There are no hard set rules for spark timing via in-car calibration, so just make your own based on input from others.

 

I'm running the ARAP bin, but you're right, it must be a bit too aggressive. I'm going to check out another bin's table. I am running aluminum heads, though....

Thanks for your patience and suggestions.

 

BTW, your base timing for that cam is 10* as per GM. They actually like a little more but that's a great place to start. Should give you loads more top end. 12-13 should be even better.....

 

Captain,

I've been down this road already.

Specifically, my initial timing was 9 degrees and I found there was a lot of "creep" at idle as well an overall sense that the engine was less than tame, you'd have to use the brake a lot and the pinging was pretty bad.

I've now got the APYP table in there and I've logged significantly less knock retard than what I was getting with the ARAP advance.

Does anyone have any feelings on this situation? I know I could stand to gain a lot more performance.

BTW, Captain, where did you find the 10 degree reference? Also, that's probably the spec as it refers to the ZZ4 crate engine with a carb. Does that make a difference?

 

Personally, ARAP is the worst bin file I used out of all of them!!!!! Way too much timing. What I have now works nicely. I got the original bin from an aftermarket company and modified it from there. Basically I reset the fans to come on at a higher temp (205*) since I was temporarily running a 195* thermostat. and modified the A/C switch to work with my 85 switch (NC vs NO), and I had to take a few degrees timing out from 2400 to 4800 to work with this 91 octane premium in California..... I also set it for the current 30# pound injectors I have.

I saved the original bin file for 24# injectors in case I go back, and to use as a reference point in the future. You are welcome to a copy of it, but use it at your own risk. I have 9:001 compression, but I'm also using 76CC chambered iron heads with 60's technology chamber designs......

The 10* is the factory recommendation and it's where I set the timing to get it through smog. It actually makes more top end at a higher setting, but you have to balance that against the attending loss of low end.....

The file I will send that is Mod 1, has the reduced timing. That is if you want the bin files.....

 

Captain C, I'm confused how you're having to compromise top end and bottom end on a fuel injected / computer controlled timing car. You can have WOT set to whatever you want without affecting emissions, bottom end and top.

 

I'm talking base timing..... Just like a carb, you advance the base timing for more top end, and retard it for more low end. What we are doing with chip burning it just like changing carb jets and recurving the distributor. It's just possible to do a much better job with electronics.......

 

I can handle the file if you don't mind sending it along.
I checked your profile and I can't e-mail you.
Is it possible to p.m. me the file?
Thanks.

 

Oops! I thought I had my email unlocked. I forgot to bring the files with me this morning anyway. What size injectors are you running? I can format that for you before I send it off.

I reset my email control so you email me now. Just be sure to put something in the subject line so I know what it's for!

 

I can fiddle with the injector. They're 24# but set at 25, the blms are better.
Thanks for your interest.

 

I already have the files formatted as 24# since that 's what I had originally. You may want to leave them there until you see what the BLM's are.

What are you running for fuel pressure? Higher than 40# pressure (what most aftermarket injectors are rated at) will make your injectors "bigger"..... I also have a file at home that will calculate that for you as well. I found it somewhere on this site or a link from this site. I need to add that to my CF Card/Reader tonight.....

 

Holley variable. Set at 43 normally and 50 with vacuum hose disconnected for WOT (to my understanding)

 

I actually found the original 24# bin file on my computer here at work. It may have too much timing between 2400-4400. I cut 10% off in those areas. I still need to optimize a little bit... I will try to send that to you if your email is setup.

With 50# and your vacuum line plugged, you are probably running around a 28# injector. Without my Excel file that has the calculations, I can't be sure. My 30# injectors are rated at 40#, at 43.5# fuel pressure, they equate to 32# injectors. That was enough to throw my BLMs way off!!!!!

Just sent the bin file, it may already be set up for 6* initial timing, you need to check that. BTW, look at my signature and see if your airflow is going to be close to what I have..... That all makes a big difference....