Stock '02 Z06 22.5 degrees timing max

[pmontelo]

Here is a sample of the timing curve on my completely stock '02 Z06.

You can see how @ about 3250 RPM timing starts to drop like a rock from a maximum of 29 degrees at WOT.

By about 4800 RPM, your left with only 22-22.5 degrees of total timing

Note that MAX torque on a stock '02 Z06 is made @ 4800 RPM, if it were not for the PCM timing calibration, this wouldn't be so.

This pi$$ poor timing continues all the way to red line... when drag racing, 2nd, 3rd and 4th gears are spent entirely in the 22 degree timing zone.

(note that I wasn't powershifting the car and I hit the limiter in second )

There is never more than 29 degrees of total timing @ WOT. You can see 40 degrees of total timing on these cars but you will only see 40 while reving in neutral or decelerating.

You can certainly get a more torque out these cars by getting past the limitation of 22 degrees total timing after 4800 RPM... too bad I can't change my timing in SCCA SS...

[FRISKY]

Thanks for posting the graph showing this. This is exactly what I have seen on my car and what I have been talking about in earlier posts!

If you took these readings while on the dyno, you would most likely see the timing drop that happens at about 4800 rpm is also when the torque level goes over 350 lbs/ft at the rear wheels.

Is this "torque management" to help keep it below the 350 lbs/ft limit that we know the computer is set to? I don't know for sure, but I suspect that's what it is.

Good luck trying to convince anyone else this is real.

Maybe LS6-Edit will fix it...

[PerforminNorman]

Awesome stuff. Thanks for sharing. I had 50 degrees of timing at lower rpm in my blown Camaro. Talk about responsive.

[timgt]

I just went out and scanned my 02 as well after reading this post, on WOT I also got 22 degrees of timing!!! Mine isnt bone stock but it only has a Halltech T1-c and a 178 degree thermostat for now. I think now its about time to order 30# injectors and get a MAFT or AFR1!!!

P.S. what do you think I can get my timing up to with the injectors alone without going into the PCM? From 22 degrees on WOT to maybe 28?

[c4c5specialist]

HI there,
A little point here.
The resulting timing curve is a result of emissions, and fuel calibration.
HOWEVER, there is a simple truth to the absolute timing.
It is only needed to complete flame burn in the cylinder. Sometimes, if you advance the timing too much, you result in a loss of power, and in extreme cases, detonation.
The reason for the loss of power, would be that the flame burn is completed before the piston gets to far from the top dead center, so the power transfer is not complete.
Also, flame burn is a direct result of turbulence in the combustion chamber, caused by tumble of the air into the chamber, cylinder head and piston quench area.
LS1 class, or Gen 3 as they are called, have much more efficient combustion chambers, then that of the L98, and the LT1, LT4 class of engines. Hence the need for less total timing for efficient power production.
I hope that this helps, besttoall, c4c5

[pmontelo]

From all the posts that I've read, these cars have been able to tolerate 26-28 degrees of advance and provide the best torque and power. At 28 degrees, under high load and high temperatures (like on a dyno pull), sometimes there is a hint of knock. Then the knock retard may kick in which will temporarily pulls the extra timing out.

Like C4C5 said, too much advance = knock and a power reduction (and possibly engine damage over time). You don't want that! But unfortunately the ultra conservative 22 degrees of total timing is firing the plug too late for optimum torque (for most conditions). But just because my old big block ran good with 32-36 degrees of total advance doesn't mean the Gen III small block or Vortec V8s with "fast burn" heads will. It's all a matter of how long does it take for the flame to spead. The faster the engine spins (up to a point), the more lead time or timing is needed for the "explosion" to happen at just the right time.

There are a lot of factors that weigh in here. GM wants the car to run well on crappy gas. They also don't turn the cooling fans on high until 226 degrees for economy and emissions. Also keep in mind that the Z06 is a fairly high compression engine @ 10.5:1.

From what I have seen on my car; I have never seen a *single* knock occurence under any condition with the 22 degrees of advance. So it's too conservitive for my typical operating conditions.

*But* I always run 93 octane fuel, and I always have my A/C system on when it's hot out so that my cooling fans stay on. My car is always running right around the thermostat temperature.

So if you want to gain some additional torque by increasing timing, you can help make sure that you don't encounter spark knock by making sure you car is cool and is not tuned to run lean.

A 178 degree thermostat and fan controler, throttle body bypass, 30# injectors and MAFT sound like the quickest and easiest way to do this today on these cars. By keeping the car cool, you have an extra measure of protection against knock. You also get a denser intake charge. You don't need the injectors for the extra fuel, you just need them to trick the PCM into giving you more timing with the MAFT.

[ZeeOhSix]

pmontelo -- nice data. What did you use to collect the data? It must have a fairly rapid scan/store rate.

Anyway, nice little ripple at the end of 2nd on the rev-limiter.

[pmontelo]

Originally posted by ZeeOhSix
pmontelo -- nice data. What did you use to collect the data? It must have a fairly rapid scan/store rate.

Anyway, nice little ripple at the end of 2nd on the rev-limiter.

ZeeOhSix,

I hate when I hit the rev limiter What this graph shows best is my poor reaction time!

FYI, I have an AutoTap. As far as the sample rate: one thing to remember with any of these scanners, the key to getting a high sample rate out of any GM car is to monitor or log only a small number of parameters at once.

Unfortunately the class 2 serial data bus that GM is currently using for OBD-II is only 10.4 Kbps. So the more parameters you monitor at one, the more data you have to send over the slow serial link for each sample. The maxium number of samples per second is ultimately limited by the amount of data you have to send over that slow serial link.

[rbartick]

As far as IAT vs. timing goes, I checked the stock 02 IAT vs MAP timing adjustments in LS1Edit. See the picture below. By 35 degrees C (95 F) we lose 1 degree. At 140 F and above, which is 60 C and higher, we are losing 7 degrees of timing. We really need to keep IAT below 95 F.



With respect to total timing, the LS6 determine total timing based on fuel quality, RPM, and airflow. See the picture below. When you get more than .72 Gm/Cyl of airflow high RPM timing is pulled back to 22. This is probably what pmontelo is seeing. Pmontelo, did you log MAF values as well?

[McRat]

Hmmm... Thanks for the info!

Observations I've had so far:

I will get KR at 60mph at IAT = 76, H20=174, WOT third gear, running 91 octane premium. I saw a max of 2 deg. I also got 2 degrees on the dyno even though engine output was normal (360hp).

The LS1 timing starts high, ~29 deg, then reduces to 25 during mid-rpms, then climbs again to 29.

Why the difference between the two engines? I can only guess:

GM went too high on the compression to run modern (crappy) premium.

The LS6 head has better flame propagation. (I doubt it).

Or ?

I haven't received my LS1Edit yet, but I'm going to put a stock (29-25-29) LS1 timing table into the LS6 running 95 octane and check power output on a dyno. My guess is that I will see ~10rwhp.

My timing on my LS1 was programmed 29 deg FIXED across the the board when racing, running 95 octane. 0 KR, excellent mid-range, and good top end (336rwhp) for a stock engine. So I think a 29-25-29 curve will easily overpower a stock LS6 table, without creating a detontation problem.

[VettTheRipper]

I don't know what the difference between the 01's and 02's were as far as TQ mgmt/abuse mgmt etc./KR are concerned but my 01 was a very early production model delivered in Jan. 01. My scans consistantly have shown between 30-33 deg TA at WOT. Granted these readings were taken in winter but winters here are fairly mild. I think my scans were done with air temps ranging from 55-70 degrees OAT. I'm only mentioning this because I'd bet this engine can tolerate fairly high advances provided engine temp can be kept under control and fuel quality is known to be good. I wish I knew why mine is able to run so high without problems. I'm sure the different cam profile on the 01's have a little to do with it. Are there other 01 owners that have TA data from their scans to compare?

[rbartick]

Originally posted by VettTheRipper
I don't know what the difference between the 01's and 02's were as far as TQ mgmt/abuse mgmt etc./KR are concerned but my 01 was a very early production model delivered in Jan. 01. My scans consistantly have shown between 30-33 deg TA at WOT.

This is not a TQ mgmt/abuse mgmt etc./KR issue. The 2002 LS6 22 degree TA is normal timing with high airflow. Someone should extract the stock PCM programming from an early 2001 LS6 so we can see what is going on.

[ZO6LS6]

VTR, my '01 did the same thing...........the '02's are set up differently.......why...........I do not know?

[rbartick]

Originally posted by McRat
<snipped>
The LS1 timing starts high, ~29 deg, then reduces to 25 during mid-rpms, then climbs again to 29. Why the difference between the two engines? I can only guess:
My timing on my LS1 was programmed 29 deg FIXED across the the board when racing, running 95 octane. 0 KR, excellent mid-range, and good top end (336rwhp) for a stock engine.

I just compared the stock timing for a stock 2002 LS1 M6 to my 2002 Z06 timing. The 2002 LS6 timing is more aggressive than the 2002 LS1 timing at high RPM & high airflow . I can post tables showing the differences if you like.

[02ZO6]

24.5 WOT with misfires. It wil only get better once Ease tells me what cylinders(s) are misfiring.

30#rs, maft and BW with cold air box. You can do it just need to experiment a little to get 27deg.