I got some time to fine tune WOT. And I can get away with ridiculus amount of timing, dont know where I will end up.. I use WB,knock censor, ears and plug readings during these tuning sessions. Engine spec is. 355 canfield 197cc alu heads hotcam lt1 intake forge bottom end comp with my pistons and my 64cc heads should be (not measured) 9.8:1 The last tuning session I bumped up the WOT timing from 31 to 34degrees A/F where 12.6-12.8 from 4000 - 6400. No knock in datamaster. Shut down the engine right after. Pulled over, took out no 3 plug, no signs of detonation. And the car just love it. Next is to take it to the track and se where it starts to fall off. Do I dare to run 35-36 at WOT ? What do you alu head guys run at WOT? Thanks

What ECM/ Prom you using?

what gas you using. i assume premium 93 octane or higher. you probly could try 35-36 degrees, i run 35 on my L98 with bolt ons no problem but i got stock iron heads/cam etc.

what does your WOT table look like? i have full timing coming in at around 3200rpms and holds 35 degrees to 4800 rpms where it drops down to 34 degrees and holds to redline.

At your high rpms above 5000, it may not like 35-36 degrees. 34 is a good number. I was told something about piston speeds at those upper rpms vs cylinder pressures/etc that it is best to use less timing or taper timing off.

Here in Sweden I use RON 98 octane, dont know what that is compared to your PON US gas.

I got full timing at 4000rpm 34 degrees.
This engine dont like high timing at low RPM ( gets "jerky" ), but as I get past 3500 RPM it just screams "more more! " .
I think my "adequate" comp ratio makes me get away with much timing.

Its a 91 vette. So i use 730ecm 8D code.

THanks

Tried 38deg and no problem on my car, but didnt gain anything either so now I have it at 36 deg.

My car is the same can handle alot of timing

/N.

Unfortunately, there is no "magic" number which will yield max power. In the "old days" when premium was truely premium, most guys used 36* - but that still wasn't necessarily the optimum value.

The best I can suggest is to take the car to a chassis dyno and do some testing. I find it quite useful in "dialing" in the optimum value. You can also do some testing to determine the difference between various values. You may find that you can obtain nearly the same HP/TQ with less timing (which I personally prefer).

Lastly, you may even want to try it using a lower grade of fuel (if possible). Then you can determine the true HP difference between various grades of gas (and whether it is truely worth the difference).

my car made just about the same hp with modified timing table with more advance than the stock table. stock i was running about 32-33 degrees. i bumped to 35 and gained 2hp or so.

the big difference was torque. i gained 10-15lb ft peak and alot of hp/tq under the curve

I found 36d to be the number for my TFS 23d heads/64cc on a 350 at
10.3:1. But I needed to bring it in at around 3200rpm. Any sooner and there was Knock. So the SA curve had a gentle curve to it.

Good ide.. Will do. My first ide whas to crank up the timing untill knock then back off. But its not the best way. Next ide whas to test it with my crapy g-tech. Not whery accurate, but you can se trends.

Cheers
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But your engine is build for FI? So your comp much be lower then mine?

I too think that "playing with the spark curve" is the most important thing to work with...even more important than just the "peak".

Playing with curve may not yield any extra peak HP/TQ but can add more TQ through out the powerband so it improves acceleration (even though peak HP isn't necessarily improved).

agreed! i picked up dyno verified 10wtq peak and held that gain all over the curve and several whp under the curve just by playing with the WOT table.

I think that is the best idea. Lower octane will yield more energy vs time. Getting away with the lowest octane possible is the key. Develfish is not a noob. So my suggestion is to try the lowest grade available. Start tuning it from scratch and make it detonate at WOT. If it still doesn't detonate, then try a hotter plug tip. Let's say it detonates at 30* of timing with low octane. Then you know it was an octane issue. You just had too much.

Good point about the plugs.
I have suspected that I run one step to cold plugs for my engine.
Its a bit to much carbon on the plugs during closed loop operation.

But first I will try to use lower octane.

ps: the knock censor works, did have major tip-in knock counts before I tuned AE ds:

Thanks

36 whas max with premium fuel. Developed knock after a few WOT runs, as the engine build more heat.
I ended up with 34 and a A/F around 12.8...

Cheers

As I am new to this and trying to be on the same page as you guys.
Are you refering to the Spark advance table?

My stock ARAP bin shows 40- 47 degrees in the 96-128 columns ;1800 through 3600 rpm.
I have one knock count WOT every run at 3000 that is pulling timing.

Also the spark reference / base timing #.
Should that be set to what the inital advance is that is dialed in at the dizzy?

The ALDL spark adder.
Does that add advance anytime you are connected and logging through the ALDL?

Methinks you'll find the references are to crank angles.
The tables can vary depending on what bin, what editor, and which definition file any individual is using.

Yeah, but is that before, or after bias values and such are taken into account ?
Kinda depends on the editor and definition file as to what that really means.

YES !!

No, that refers to when the ECM is deliberately placed into factory ALDL test mode.

Thanks for the replies.
Like many others here trying to get my head around this new science.
Have read all the stickies here and other tuning Forums.
Researched many EFI tuning sites.
Understand the theory; no just trying to do the practical.
Many more questions to come no doubt.

Thanks for the replies.
Like many others here trying to get my head around this new science.
Have read all the stickies here and other tuning Forums.
Researched many EFI tuning sites.
Understand the theory; no just trying to do the practical.
Many more questions to come no doubt.

I just revisited my WOT timing and the difference is unreal. I went from not even being able to spin the tires unless I was making a hard left or right turn and just standing on it, to severe traction issues all with one chip. The amount of torque I gained is mind blowing and it pulls incredibly smooth too. Also got rid of the notorious staight pipe cackle that I was having. Here is what I'm currently running. Seems like a lot but it seems to love it on 91 octane and only a few ghost knock counts showing up. Engine is a 185k mile 350 short block with ported and redone vortec heads with a 3 angle valve job running a .015 metal shim head gasket for around 9.5:1 compression and it flat gets it done in a 5200 pound truck.

Any PE adders on the spark?

6 degrees worth and a AFR of 12.4:1 but actually after looking at my PE Fast table I realized I'm not even entering PE. Like I said I'm just roughing it in for now and will tweak the timing later but so far the difference is amazing.

Ok..

Regards

Devilfish..