DramaFoYoMama

Everyone has to start out somewhere. I would say copy the table and make a few test runs to make sure no knock is present. Then go to town tweaking to your liking. We're here to help you out if you have any questions.

Predator

Appreciate the support! I'm in the process of ordering a Strange 12-bolt now, and heads won't be until after I get the rear installed in the spring, but I'm trying to plan what's next, and if I can tackle it. Actually I'm doing the rear, UD pulley, front sway bar, C5 brakes, and then heads. Anyway, thanks again!

Viper

iTrader: (6)

Good luck Predator, with all the new stuff get some pics in action and change the avatar out of the woods!

Predator

Thanks Viper! I'll definitely get some pics up. First thing will be shots of my new Billingsley Strange 12-bolt, off the truck, but I think I'm keeping the avatar. It's kind of an artsy fartsy black-and-white appreciation of my Trans Am. I do b&w film photography in a home darkroom.

Predator

Just to update you guys on my concern about changing the timing table. I think I have a handle on it:

The lower airflow values (0.24-0.32 g/cyl) are where the engine operates under low-rpm load. The middle airflow values (0.36-0.72 g/cyl) are where the engine operates under medium load. Values above 0.72 g/cyl are about where the engine operates at WOT. You begin tweaking the 0.76 g/cyl and larger values to either raise or lower your WOT timing. Then tweak the 0.72 and 0.74 g/cyl values to smooth the transition from part throttle to WOT.

Seems pretty simple when you take a little time to understand the table. This is great because it means I can get heads that will increase my CR up to about 11:1, and be able to run the best timing program for it.

DramaFoYoMama

What cam are you going with? I can send you a table of a tune I did for a guy with an LS6 motor and an HPE S cam.

Predator

I have a 224/224 112. Yes, send the table, I'd like to look at it. Appreciate it. What are the specs of an HPE S cam?

One thing I'm not sure about is if you were retarding timing, would you just lower the WOT timing values (0.76 g/cyl and up), or lower the timing numbers across the entire table (globally?)? Thanks!

DramaFoYoMama

I would just lower the WOT timing. You could actually take the timing from an LS1 file and up the low and medium load areas and get no knock. Also, you need to log before you do any changes. What air mass are you hitting at WOT now? I tuned a car with an MTI X1 cam that only hit .68 g/cyl @ WOT. It still runs very good, but every car is different. What logging program do you use? If you want to make a log, I'd be happy to look at it for you.

Predator

Thanks, I just have a cam and stock heads now. I'm planning on getting heads in the spring (not sure which ones yet). I looked at my latest EASE scan and I'm not sure if I have the PID that has the air mass info you asked about. I have "Air Flow Rate MAF Sensor" which maxed out at about 32 lbs/min at WOT. What PID do I need to log to determine what g/cyl I'm hitting at WOT? I still have lots to learn as you can tell. Thanks again!

Predator

I found this formula but not sure how to apply it to MAF Air Flow (lbs/min):

g/cyl = 15 * MAF/RPM (when MAF is measured in g/sec).

Predator

454 grams in a pound, so 32 lbs x 454 = 14528/60 secs = 242 g/sec ???

DramaFoYoMama

Actually, that's not quite correct. There are no units of time in g/cyl. If you want to be more accurate, use 453.59 grams per pound. Also you divided by 60 seconds, where it needs to be RPMs. I've never heard of EASE. Who makes it? What format does it save the logs in? I seriously doubt it would be compatible with EFILive, but who knows.

Predator

I was trying to convert MAF Air Flow lbs/min into g/sec, that's where the 60 secs came from. It's probably not that important because I'd be retarding the timing table below 0.72 g/cyl, so I'm pretty sure that the WOT air flow on my car will be retarded even if it's below 0.72 g/cyl.

Ease scans have a .G2P extension. Here's the website if you feel like checking it out for the heck of it: http://www.obd2.com/

I'd like to thank you for your help! I've learned a lot this weekend. I feel pretty confident now that I can handle my timing table. Whatever heads I get I'm sure will give me a higher compression ratio, so I'll probably adjust the WOT timing to about 22* as a starting point, and go from there. No sense blowing my engine if it could be avoided.

Anyway, I might need some more help when I tune my heads, but in the meantime, thanks so much for your help!! Say hi to Roger's parents for me. Happy holidays dude!

DavidNJ

This thread brings up the question: how does ignition timing vary with different heads? I tried to start a different thread on the subject unsuccessfully.

In any case, when tuning I would imagine you use high enough octane so that it isn't an issue. Then, if you need to pull timing because of compression you know you have an octane/compression trade-off.

Bombguy99z28

Read this

And this

Should answer any and probably all ignition timing and compression ratio questions.

Predator

Exactly DavidNJ.

Thanks for the links Ben.

Truth is I was hoping for simple rules-of-thumb, for example, assuming 93 octane, with a 10.5:1 CR you should never run more than 26* of WOT timing, 11:1 never more than 24* and so forth. But I see that it's not that simple, and all the variables between cars, climate, etc. make it impossible.