Cookwithvette

I remember reading a thread some time ago talking about adding timing around light cruise giving a positive effect.

What I'm getting at is, how do you figure out how much timing to use? Do you just keep adding until the engine starts complaining then back off a tad? What about idle? I've learned how much my motor DESPISES anything less than 17 at idle and it runs well at 30.

How do I know how much timing my motor wants?

mrvette

I remember my '87 and it called for 6-8 degrees and I used ten on the initial, and found the engine liked it.....

since then my '72 with EFI here has had two differant programming chips, and I not happy with the one here now....runs lousey when cold....
maybe there is another problem, but I notice the timing acts weird, but that discussion is years old now, and been accepted as 'normal' by me, due to other folks input....still think it's weird though....

GENE

zwede

Don't know if there is a scientific way of finding out without advanced equipment (detonation detection). I used to have a 96 Z28 and hooked up a scantool and mapped the timing advance it had. I then set my vette to something pretty close.

I can run about 45 dgr advance at 1500 rpm, low load. It goes to 52 dgr low load by 2400 rpm. Idles at 22 dgr.

Fevre

It is very similar to what the chart would look like for a reg vac adv unit, low loads induce vac adv while WOT throttle negates it, low rpm's has lower mech adv and higher rpms has higher mech adv. You can set up a few diff tables for diff driving cond: regular driving, track time and 'I got a ****ty tank of gas'. Your ECM will pull adv when it encounters spark knock but it is best to try and adj for if you can like when you get bad gas.

stickboy

A knock sensor is the easiest way to set it. Just advance the timing until you start to get knock, then back off slightly.

Here are picture of what mine is set to at this point. Your timing will depend on your compression and cam, but maybe these will give you an idea of what the curve should look like.

http://dev.corvettepages.com/forum_i...ming%20map.jpg

http://dev.corvettepages.com/forum_i...%20map%202.jpg

Cookwithvette

Okay, thanks guys. My current map looks like this:



Don't think I'll be getting really aggressive in the high load range but I'd like to maximize cruising efficiency.

Budman68

6-8 with a the ignition plug harness disconnected. Then stop the car and reconnect. Restart and you are advanced 15 to 20 depending what is in your program. This is how you set up the base timing on my TPI.

cardo0

Wow this new forum system is from out'a space!

Well cook I know nothing about FI but I can tell you need a vacuum gauge to monitor your MAP at different rpm. They're really cheap and you can mount them permanent or temporary. No electrical power required, only need to find a vacuum fitting somewhere under throttle plate - or at least on nearby runner - to connect to. Also the small 2&1/4" gauges will fit in that stupid clock hole - but opening that plastic instrument cluster is a ton of work.
Yea vacuum gauges are nice for setting up carbs parts like power valves and ignition vacuum advance cans. Pretty much a no brainer to install and use and hope this helps. cardo0

zwede

Cook: A few thoughts on your ignition map:

Low rpm, high load: Take out some timing there. I guess you don't floor it much at 1000 rpm, but if you should you really don't want to give it 25 dgr. Start at about 14 at 400 rpm WOT, then go to 20 by 1200, 30 dgr @ 2000, 36 @ 2500.

Run the same advance at 800 and 1000 at idle MAP (35-45 or whatever vacuum you idle at). The way you have it now it will gain 4 dgr if the idle fluctuates up and that makes the idle less stable. You should not have any problems idling at 20 dgr or more.

You can advance your cruise advance a lot. Run 40-45 by 1500 rpm cruise. Go to 52 dgr by 2400.

Cookwithvette

cardo0, I've thought about putting a vacuum gauge in the panel. Some time ago I replaced all the gauges and put an oil temp gauge in the clock hole. Didn't really think that one through. Never got around to mounting a sender. Vacuum gauge just might be the trick.

zwede, Hey, thanks man! It's still the base Holley map, I've been busy tinkering with the fuel map up until now.