Advance Timing For L98's
 

Hey guys, So I was doing a search about advance timing for L98's I already have a tune in the ECM by Painless Performance( I had my Air Ratio/Fuel Injector tuned) I was just wondering how can this help me if I advanced 4 degrees? And how can I do this?

Thanks guys! Happy New Years! :cheers::flaghalfmast::flag:

Unless you have timing changed in the tune itself, the ECM controls timing beyond the stock 6 degrees BTDC as set with a timing light.

Yes, you can advance the timing. GM was conservitive w/ the advance because of the octane of the fuel out there. If it has spark knock, either run a higher octane fuel or retard the timing.
To adjust the timing you need a timing light & a distributor wrench. Get the engine up to temp. shut off & unplug the timing connector, point the light at the timing scale while the engine is running, loosen the dist. clamp bolt slightly & turn the dist. You'll see the mark on the balancer, line it up to the number on the scale.

Thanks seems helpful, now will this gain anything? I run a 93 octane fuel I haven't heard any knock, how much is a distributor wrench? and can I get one at my local auto shop?

Here is a pretty good write-up on how to set your ignition timing.

Yeah, the auto stores usually carry a universal type dist. wrench.
Advancing the timing will probably give you maybe 6-8hp, but its the overall responsiveness you'll probably feel.
Some engines like the adv, some don't respond to it.

Sweet deal, I'll look more into it, thank you!

Experience is the best teacher.

The ECM only knows that "base timing" is 6 deg.
The L98 has no crankshaft position sensors so setting "base" @ 6 is critical.
From there the knock sensor will back timing off as the ECM see's fit.

I have bumped my L98's "base" up to 18 at one point just to see how the ECM would compensate.
It worked fine but the knock sensor was on overload :eek:
After many trial runs I settled on 12 for the best performance and least knock counts at WOT.
Gets me 24MPG at 70MPH cruise speeds too.
This is with a CC268 cam and PCMforless tune running Chevron regular fuel.

:cheers:









.

Whatever. If you think 47-deg of advance -- at partial throttle opening is conservative -- then bump it up into the 50's. That's what moving your dizzy will accomplish.


That's why I took the time to learn about tuning instead of farming it out to Alvin and the Chipmunks.

Must not be THAT "critical" if you advocate changing it (like you tried).

Ding! Ding! Ding!

"Worked" is such a loose term. Let's see....47+18-deg advance gets you 65-degrees of spark advance for light-load running. Nah...not the recommendation I'd give. :eek:

People who learn to tune find out that GM had a built-in hwy "circuit". At light loads, they did bump timing 3-4 degrees to get a hair more mpg. More importantly/effectively, they also pulled fuel to raise mixture from 14.7 "stoich" to a higher, leaning mixture. (When reading up on fuel tolerance, you find this is acceptable and functional.) Somehow, the EPA said this technique was "cheating" on EPA fuel ratings and made GM disable that circuit.

By bumping your timing 4-6 degrees (like some advocate), your ESC system will be pulling timing from moderate to high loads ALL THE TIME. BFD, you may say....and understandably so. But most people don't realize/care that retardation by the ESC system can end up with softer timing than landing short of the knock sensor trigger. (Because the ESC pulls enough to be safe...which can end up lower than "ideal". ) If you don't time/dyno the changes, your butt-o-meter will probably lie. You may get a hair more responsiveness in exchange for slightly slower mid-top-end. OTOH, you will be permanently setting some of the hwy parameters which get a hair better mpg.

What's better is to ask a tuner to activate hwy mode, get BOTH fuel and spark advantage (at light loads), retain normal (correct) timing at mid-high loads, and (IMO) adjust for E10 fuels. That way, you'd be ready for any BS your local gas station does from the current E10 standard.

More importantly, you won't be pushing the limits of the ESC system to the point where you're car may become undriveable if the ESC fails. By that, I mean a lack of spark retard could leave you seeing how much (too much) the timing is advanced. And, w/o the ESC knocks just trying to drive it down the road.

GM didn't code these systems conservatively. They were pressured in every way to hit mandated mpg demands for the environment. If anything, they lowered compression to stay out of detonation issues. The ESC system is there so they could be aggressive yet have a backup system that would "save" an owner who dumped low-grade, low-octane fuel in an engine timed CORRECTLY for the recommendations provided in the manual.

If you aren't happy with your performance, buy another car, get modding, or hire a tuner to do any changes correctly. And, FWIW, the later is a waste of time unless you do have significant mods....or you want to alter it to FOCUS on light-load hwy use. Cause that's about the only thing you might gain.

You said you already have a tune in the car. What does your TUNER recommend for static timing? He knows your setup a lot better than the rest of us who are guessing and throwing out random suggestions.

I just wanted to know how advance timing could improve my tune, thats all

When I first got my '88 I read on this board that advancing the timing will give me better performance, so I did. I thought it felt more responsive, but took it to the dyno and had actually lost hp. It ran best at 6 degrees.

If you datalog, you can bump the timing and see the effects. I have a fear of spark knock so I datalog any time I make a change in the car.

I musta missed the part where somebody asked you for an opinion. :D

:cheers:

The spark advance is determined by a combination of the static timing (where the distributor is set mechanically) and the timing determined by the ECM. The PROM in the ECM has a parameter for the static timing (6 degrees) and the ECM adds its own timing to that. If you increase the static timing the ECM doesn't know that and it could overadvance the timing and cause pinging.

:withstupid:

Exactly

Interesting; that confirms Gregg's point earlier. :thumbs:

Back to the original question.......
 

I think most people who tune or have knowledge of how ECM tuning works would tell you not to fool with the base timing. To some folks it can *feel* like a seat of the pants improvement, but as mentioned above in post # 12 it is usually unfounded. Kind of similar to other urban legends like the TB airfoils, etc. Your total advance is best left to the tune parameters so you're not beating piston rings to death (or worse) on a hot day or going up a steep hill in the mountains. HTH & happy new year!

:iagree:

It was recommended that I see your post here as I am having my issues. Having done much research and with "email talking" with Patrick at Super Chevy Magazine he thinks I may need to replace my ECM. This makes sense to me since it is on a daily driver 1987 Corvette with 176,000 miles on the odometer now. But freshly installed newly built motor. Here is the link to my original thread: http://forums.corvetteforum.com/c4-s...ng-richer.html

Here is what I have written today:

Yesterday I attempted to start the Corvette once again.

This past Friday I replaced a broken up Idle Air Control Valve Connector as pictured below. While this was a necessary evil the connector does not come with colored coded wires. Careful attention to connect the new wires into the same wires as on the old connector was done. I also replaced the Electronic Spark Control Module on the chance that this may have been bad. Since I previously checked the spark plugs and finding the #1 plug to be fouled richly, the other plugs were seen as slightly rich but mostly burning normally. So on this day I had replaced all 8 plugs with fresh ones. Many attempts at starting the engine gave me zero results other than good cranking but not catching fire. It also resulted in having to trickle charge the battery over night. This being the New Years weekend I refrained from further work on the Corvette to avoid the wrath of my wife.

This being Monday (yesterday) I again made my attempts to start the car. But first, I pulled the #3 wire, attached 1 of the good plugs I replaced and grounding it onto the header I saw that indeed spark was coming thru. Onto the even side of things I did the same thing with the #4 wire and spark again shown working. This puzzled me, good spark, having smelled fuel as if in my attempts to start the engine caused me to flood it in my attempts. So now I pull plugs #1-3-4 & 6, these being the easiest to get to. These plugs all looked just like they did when I pulled them out of the box to install. No signs of spark or fuel having touched them. This has become my problem now not being too rich as I first thought.

I called the gentleman who built this engine and who got me running in the first place to get his opinion. He suggested that I try to put some fuel, or not having that, spraying some WD40 into the Throttle Body to try to get some fuel into the thing to start it. I am apprehensive about doing this as it is not like my muscle cars of years past with a carb on top of the intake. I would not hesitate doing so on a carb'd engine having done so many times before. But this is a TPI Fuel Injected engine so my hesitation. Your thoughts on this?

At any rate I am now at a cross roads as to what to do. I am wondering if for some reason installing the GForce Chip after the HyperTech Chip had been running without issues was such a good idea. Is it possible that this chip swap caused some unforeseen problems? The HyperTech Chip is back in again with no better results in starting the engine up.

Or, thinking further, could the Fuel line, Filter or even the Fuel Pump be an issue now? In my email yesterday I mentioned "Popping Corn" sounds while attempting to start the engine. I had by way of cell phone the engine builder listen to the start up process and he says it sounds like it wants to start and I am hearing the spark firing but not enough fuel to ignite. That one BIG POP that I heard last week, is it possible it ignited in the runner/plenum area and knocked out 1 or more Fuel Injector from working properly? I of course can't tell and I did several times run my Code Scanner and every time it flashes a "12" as in normal. No codes to indicate what if any problems there might be.

I am waiting for a programmer to return my Factory Memcal Chip from the ECM with the reprogramming being done to my new engine specs. As I indicated in my earlier email, he suggested I go to an adjustable Fuel Regulator. Before making my car any richer and spending money I will wait to see what happens with the newly programmed Chip.


Actually the link to the sensor connector just replaced: http://www.autozone.com/autozone/par...ntifier=342412