ls3 in a 2001 ls1 f-body timing question

[kyphur]

So I'm looking at my timing when driving and making runs. I've noticed that about the most my timing pulls is around 27 - 28. I'm using one of the timing tables from a 408 tune in the repository for my starting point and have made adjustments accordingly.

The thing is that due to my displacement I think my peak timing is different than the one in the tune. The LS1 with boltons in the repository positions its peak timing higher (lower cylinder volume) in the table while the 408 is just a tad bit lower. So I'm missing my timing curve just a little.

Usually I tune sbc's to pull maximum timing (usually 33 - 36) by 3k rpm. What is safe for a LS3?

[WS6FirebirdTA00]

First, I would not trust tunes in the repository, can be quite dangerous.

Second, that sounds like extremely high timing for an LS3. I would probably back off 10º from there and then start dialing it in.

I am not sure what you mean by peak timing is different. Post the files you are talking about.

[motorheadmike]

Less is more. If you run a proper histogram that logs knock retard you will see where in the table it wants less timing, usually around maximum brake torque (MBT); based on the fuel you are running, load (gearing) and so on.

Cheers!

[kyphur]

Yeah, I've started reading a little more on timing and there's a lot of talk about how the LS series is so much more efficient so it doesn't need as much timing (long story short).

WS6> What seems like a lot of timing to you? The 30+? I used the 408 as a base and compared it against a number of LS3 stock tunes for Corvettes and Camaros and adjust accordingly.

What I'm talking about with peak timing is where they pull in their useable timing. I'm not talking about 0 g/cyl at 5000 rpm. Usually it will be a path with low g/cyl at idle and higher g/cyl at higher rpm but it is limited by the displacement of the engine. The 5.7 liters seem to have their timing curve higher in the chart (due to lower cylinder volume) vs larger displacement vehicles which have their timing curve lower in the chart with higher g/cyl as the rpm climbs.

Does that make sense?

[WS6FirebirdTA00]

If your WOT timing is at 27-28 that is too high.

Correct it will track up in g/cyl as RPM increases mainly off idle, then it will increase slower until it just about levels off. Post your tune, that will help us see where you are at.

[kyphur]

If your WOT timing is at 27-28 that is too high.

Correct it will track up in g/cyl as RPM increases mainly off idle, then it will increase slower until it just about levels off. Post your tune, that will help us see where you are at.

Weird, because the stock tune for the Camaro LS3 has 35* of timing at .28 g/cyl at 1600 rpm's and that's my cruise stats. I'm only pulling 25* at that rpm and cylinder volume. Though at my 80 g/cyl the LS3 Camaro pulls 21* while mine is set for 26*.

I've attached my tune and my walk home.

[WS6FirebirdTA00]

Yea that timing table needs a lot of help.

If you look at the high loads mid to high RPM you are in the mid-20's. Still too high IMO.

[kyphur]

Yea that timing table needs a lot of help.

If you look at the high loads mid to high RPM you are in the mid-20's. Still too high IMO.

Yeah, when I compare it to the LS3 Camaro/Corvette stock tunes I'm seeing about a +/- of about 2 - 3 degrees of where I'm hitting in my normal use curve except at idle which theirs is a lot higher than mine by about 4 - 6 degrees. Cruising at 1200 rpm's (50 mph) I'm about 2 degrees less than they are. On deceleration I'm anywhere from 4 - 18 degrees lower depending on my cylinder volume.

All the low rpm/cylinder volume cells are really high (usually 35+) for the stock files. Seems like my cylinder volume/rpms are only a few off except for the at idle.

Edit> Still looking over my logs... at 2000 rpms and .29 g/cyl my timing is 27 while the stock tune is 37. At 2000 rpm's and .42 g/cyl I am getting 26 degrees while the stock file is 33-35. I'm looking at other tables to see if it pulls timing down in those areas but so far I haven't found anything.

[WS6FirebirdTA00]

Post the stock file you are comparing to as well.

[kyphur]

Here you go. I've compared this one across 4 other stock files in the repository and they all come out identical.

Edit> Mine is lower until about 3k rpm's and then mine goes higher. Not by much, but it does.

[WS6FirebirdTA00]

My biggest concern is full load WOT. Look at 4000 RPM and 0.80 g/cyl. Your table is 8º+ higher.

[kyphur]

Yeah, I was noticing that and that's one reason I posted the original post. I've looked at multiple tunes to try and deduce what was best for my setup and my past tuning experiences with older cars.

The main reason I didn't copy this verbatim is that the new Camaro/Corvette has other tables in the files that affect the way timing is handled. That made me originally believe that when you saw the negatives in the spark field that timing was being controlled by another table rather than main spark table during those instances and that I didn't have access to those tables in my 01 PCM. So I looked at LS1 PCM timing and some LS3 timing tables to try and get me into the area.

After reading about the way LS engines work and need less timing I will be adjusting accordingly now. It's almost the exact opposite of what a SBC engine would need (low timing at idle and higher as RPM's climb). So my thought process on timing for a LS motor is off.

[WS6FirebirdTA00]

Yeah, almost have to retrain yourself on these motors

[kyphur]

I'm learning that, ha ha. Just glad that I just didn't start throwing timing at it and going, "What's going wrong!?!?!?!?!".

[kyphur]

Well, I've been driving it now for a few days with the 2012 Corvette timing tables... I like my old timing table better it seems. Seems more sluggish and has a hard time staying cranked when you first start up on cold days. Just shifting it into gear will kill it sometimes.

I'm noticing my timing is usually running around 30 - 40 (if map/dyn cyl air are low it goes higher than this) when I'm on the freeway. I think the LS3 VCM has other tables to pull or add timing based on driving conditions that I just don't have.