C5 97-00 01-04 timing tables

[boogsawaste]

Does anyone know why the high/low octane timing tables on 97-00 corvettes is so crazy high on the top end and mild on the low end compared to the 01-04 that are more aggressive at the bottom and much much (11?), less on the top end?

I know there were changes in 01+ namely the ls6 intake and exhaust changes through the years but why such a drastic change otherwise? Cam changes happened but they?re all pretty close in size.

I?m swapping my 00 intake to an ls6 and I also spray a 100-150 wet plate shot of nitrous. Just wondering if there are other modifiers to the tables that affect WOT timing? I?m curious if I should be tuning off of a base 01+ tune once I swap or if I should keep working off the one I already have. Side note I?ve read that the intake plays a big part in reducing the timing but of course that?s just what I read and not sure I came across any concrete information. Thanks!

[Fast4.7]

Does anyone know why the high/low octane timing tables on 97-00 corvettes is so crazy high on the top end and mild on the low end compared to the 01-04 that are more aggressive at the bottom and much much (11?), less on the top end?

I know there were changes in 01+ namely the ls6 intake and exhaust changes through the years but why such a drastic change otherwise? Cam changes happened but they?re all pretty close in size.

I?m swapping my 00 intake to an ls6 and I also spray a 100-150 wet plate shot of nitrous. Just wondering if there are other modifiers to the tables that affect WOT timing? I?m curious if I should be tuning off of a base 01+ tune once I swap or if I should keep working off the one I already have. Side note I?ve read that the intake plays a big part in reducing the timing but of course that?s just what I read and not sure I came across any concrete information. Thanks!

The more airflow the higher the GM/CYL value.

[ELSimple]

Not sure if your OS has this. Spark> base corrections> fuel > base will add timing depending on commanded afr/eqr.

[boogsawaste]

The more airflow the higher the GM/CYL value.

Yeah for sure but the only major difference I?m seeing is the intake manifold and it?s not even that great of a manifold. I?m talking the 97-00?s have 28? at the top of the graph while the 01+ have 17?. I can post up the whole tables if anyone wants to see. It?s just wild to me that they changed it so drastically and I was wondering if it?s more because the LS engines don?t need much timing or something else. Appreciate the reply.

[boogsawaste]

Not sure if your OS has this. Spark> base corrections> fuel > base will add timing depending on commanded afr/eqr.

I?ll have to look when I get home. Thank you!

[Fast4.7]

Yeah for sure but the only major difference I?m seeing is the intake manifold and it?s not even that great of a manifold. I?m talking the 97-00?s have 28? at the top of the graph while the 01+ have 17?. I can post up the whole tables if anyone wants to see. It?s just wild to me that they changed it so drastically and I was wondering if it?s more because the LS engines don?t need much timing or something else. Appreciate the reply.

The 01+ have 243 heads. That being said stock does not run much below 0.80 gm/cyl dynamic airflow. I doubt the portions of the timing map it actually uses in reality are that much different. They went to both the LS6 head casting and intake manifolds on the 01+ LS1. My buddies 2002 TransAm had them factory. My brother in law also had a 2005 L33 truck with 243s on it from GM. The timing tables were subatantially different compared to a 706/862 headed 5.3L.

Feel free to post up both tables and the stock tunes.

[boogsawaste]

I honestly didn't think the 01+ corvettes came with them so I learned something new today! That could definitely explain the big timing swings. Hopefully these pictures work and are clear enough.
timing.jpg
timing2.jpg

Sorry I added my nitrous tune with reduced timing. Edited with correct stock timing tables.

[Fast4.7]

I honestly didn't think the 01+ corvettes came with them so I learned something new today! That could definitely explain the big timing swings. Hopefully these pictures work and are clear enough.
Attachment 153075
Attachment 153077

Sorry I added my nitrous tune with reduced timing. Edited with correct stock timing tables.

I have seen too many of them on those cars that look absolutely untouched to think otherwise. I feel like GM may have had a shortage on 241s at some point and used them. I have seen 243s as early as 2001 and 241s as late as 2004 with no realy rhyme or reason.

[boogsawaste]

Strange but it could definitely explain things. I also had a wrong table in my previous post which I corrected now.

[2xLS1]

The 01+ have 243 heads. That being said stock does not run much below 0.80 gm/cyl dynamic airflow. I doubt the portions of the timing map it actually uses in reality are that much different. They went to both the LS6 head casting and intake manifolds on the 01+ LS1. My buddies 2002 TransAm had them factory. My brother in law also had a 2005 L33 truck with 243s on it from GM. The timing tables were subatantially different compared to a 706/862 headed 5.3L.

Feel free to post up both tables and the stock tunes.

I've seen and worked on more 98-02 F-bodies than I can count in the last 25 years including owning 2 (still do) and no LS1 F-body ever came from the factory with 243 heads. 01 and 02s got the 241 casting head which were the same port wise as the 98-00, 98s being perimeter bolt valve covers, 99-00 being center bolt so a different casting number. Only the 01+ Z06 Vettes came with 243's. All the 01-04 LS1s had the LS6 Intake and 241 heads, F-bodies and Vettes. There were a few 01 and 02 LS1 F-bodies that got a LS6 block (block only, not short or long block) not that it made any difference in HP. And yes the L33 5.3Ls had 234s

[2xLS1]

Not sure if your OS has this. Spark> base corrections> fuel > base will add timing depending on commanded afr/eqr.

The Vettes don't use that table until starting in 01. Before that that table is zeroed.

[Fast4.7]

I've seen and worked on more 98-02 F-bodies than I can count in the last 25 years including owning 2 (still do) and no LS1 F-body ever came from the factory with 243 heads. 01 and 02s got the 241 casting head which were the same port wise as the 98-00, 98s being perimeter bolt valve covers, 99-00 being center bolt so a different casting number. Only the 01+ Z06 Vettes came with 243's. All the 01-04 LS1s had the LS6 Intake and 241 heads, F-bodies and Vettes. There were a few 01 and 02 LS1 F-bodies that got a LS6 block (block only, not short or long block) not that it made any difference in HP. And yes the L33 5.3Ls had 234s

I have cammed probably 20 of them now and yes some did have 243s on them. I was in doubt when I saw them before until I cammed my buddies 2002. He bought it new and it was a 40K mile untouched car. Also explained why it put down 320 whp through an A4 as a tuned but otherwise stock car when I tuned it. Never looked at closely until I pulled the cam from it and was swapping springs.

[SiriusC1024]

And since we're being contentious 799 heads are not the same as 243.

[boogsawaste]

The Vettes don't use that table until starting in 01. Before that that table is zeroed.

Could this possibly explain the change in the high/low octane tables being so different then?

[2xLS1]

GM certifies engines to be emission compliant with certain parts and doesn't just willy nilly build them with non certified parts for that vehicle and put them in vehicles. I've dynoed plenty of tuned A4 01-02 F-bodies put down 320 hp on 48" roller Dynojets with 241 heads. Both my 99 and 00 A4 F-bodies made 308 HP bone stock untuned and those have LS1 intakes.

[2xLS1]

Could this possibly explain the change in the high/low octane tables being so different then?

Possible. Trying to understand why GM calibration engineers do things the way they do can be an exercise in futility.

[boogsawaste]

Possible. Trying to understand why GM calibration engineers do things the way they do can be an exercise in futility.

You’re not wrong!

So I’ll probably just stick to my original 00 tune and adjust as needed.

Thanks all for the help and info!

[2xLS1]

And since we're being contentious 799 heads are not the same as 243.

The ports and the combustion chamber are the same. The Gen 3 6.0L head has the same port as the 243 head. Just has a bigger combustion chamber. 20 years ago when there were not all the aftermarket head choices there are today and 243s were scarce and costly Patriot Performance was taking the 6.0L heads and welding up and machining the combustion chambers and selling them as LS6 style heads for less than what real 243s were selling for.

[SiriusC1024]

The ports and the combustion chamber are the same. The Gen 3 6.0L head has the same port as the 243 head. Just has a bigger combustion chamber. 20 years ago when there were not all the aftermarket head choices there are today and 243s were scarce and costly Patriot Performance was taking the 6.0L heads and welding up and machining the combustion chambers and selling them as LS6 style heads for less than what real 243s were selling for.

That's what everyone says, but it's not true. I've ported both. The ports are different. The outlet of the exhaust port on the 799 is slightly tilted, and the entire port has a twist and bias.

The seat material is more durable on 799's. Typically there's a lot less wear. When trimmed with a cutter the metal has a slight copper hue.

799 is the superior head, and it's cheaper.