There are a few things I've learned messing with TBI that I think I will share since alot of posts pertaining to such things come up. some basics

Lets start off with timing.
Back in the days of the stock 305 in my bird i had crazy notions that more fuel, more timing= more power. You seem to see that implication everywhere.

Unfortunately I didnt learn that was not the case until the old motor was allready gone so i never saw its true potential.

Stock Lo3s come with a base timing setting of 0 deg from the factory which is really quite meaningless since the calibration in the chip is the ultimate deciding factor in how much advance you have.
Suffice it to say, the stock timing calibration sucks.

at WOT your total timing might hit 30 degrees depending on your chip, and typically its at a very high rpm relative to what most hot advance curve kits for HEIs offer.

In my experience your typical 305 isnt going to want much more than 36 degrees timing at most. Id venture to say that a near stock L03 would probably most likely perform best at around 34 degrees give or take.

WHen you advance the timing you are simply adding more timing physically to what the chip is allready adding. So say your current combo added 28 degrees on top of the zero your dist was set at and you advanced the timing to 4 degrees btdc you are now running a total timing of 32 degrees.

This is why I think anyone running more than 8 degrees on a stock chip will lose performance and probably detonate.. probably detonate even sooner than 8 degrees if you ask me.

Alot of times that extra timing will feel nice on the test drive.. at part throttle that is. The ecm also has another function called WOT spark advance. In otherwords its holding back a few degrees until you hit WOT. Why gm did this.. im not totally sure. I do know reduced timing decreases NOX emissions. So when you bring your timing up in the stratosphere you are making up for a weak part throttle area while hurting the WOT area. The best solution for this is to start custom chip work.

Youll find this problem most prevalent in cam swap motors. When I first ran my 214/224 cam'med motor on the stock chip it required a rediculous amount of base timing just to idle right and drive decently. What i ended up doing in the process was making the car knock at wot. It just wasnt efficient at part throttle and required way more advance to ignite the mixture.

I think youll find the further you get from stock.. the more things you do to increase the rpm at which peak power is made, youll need more part throttle timing and the more it will seem like advancing the base timing makes more power. Which would be true for part throttle operation, where a large change in the physical degrees of advance would not be as unlikely as it would at wot.. and while the curve of things at wot is likely to change quite a bit, the total amount wont really change more than just a few degrees at most. So dont add more timing to the whole thing when its not neccessary


Another thing that needs to be known is that these cars are most likely going to be a little rich from the factory. Dont just jump up the fuel pressure blindly. After a few basic mods you might have just gotten the A/F ratio to its "sweet spot". The factory o2 isnt really worth a damn either at telling you what that sweet spot is so dont fuss with it too much when looking for wot power.

The whole thing is a delicate balance not just more more more

 

Well said Pablo.

 

When I checked the timing on my lo3 with the esc unplugged it seemed to be a little off at 2* retarded. Then I noticed, that whenever I activate the throttle lever, the timing advances 1 or 2 degrees.
I think this is due to a worn out timing chain.
I then readjusted the timing to 4* advanced and, using winaldl, noticed lots of detonation around 2500 rpm even with 98 octane gas. I am not sure if this isn't due to carbon buildup in my combustion chambers because the engine did knock with the stock timing setting with 98 octane gas, too.
Because of this behaviour of my engine I did not notice any improvement with advanced timing except for part throttle operation, where the engine feels a little stronger.
It looks like, that I will have to wait until my s/r torquers and a new timing chain are on.
Maybe I am wrong, but I think that when receiving bad results/knock when you advance your timing, a worn out timing chain and carbon buildup in the combustion chamber could be taken into consideration.

Any thoughts/comments?

Later,

Andreas

 

yes Andreas you are right.. you might want to try running some top engine cleaner or just plain water through the engine to clean things up. Another thing to consider is ring seal, if you are leaking some oil into the combustion chambers that will make it more knock prone aswell

 

so in essence run the timing on the mark or whats best? 2, 4 , 6 advance , retard............ive never fooled with it its on the stock mark now with a thermomaster from hypertech........

 

you definately dont want your timing anywhere ATDC

so it would be advanced... and i cant give you a definate number. Every car runs differently. Test and tune.

 

Pablo your starting to sound like Grumpy.

 

atdc means retard pablo?

 

hah steve, i hope not.. not to talk smack about grumpy or anything
atdc means after top dead center.. that is retarded
thats bad

 

When you change the timing at the dist are you supposed to change the setting in the prom to show where the dist is physically at? And why......

 

no. The only reason as far as i know for the base timing setting in the chip is so the timing numbers represent whats really going on rather than showing like 6 degrees missing .. its still going to be there just not going to show it when you edit the chip you have to keep the 6 deg at the dist in mind

 

So what the tables show is really plus what you have at the dist?

Say 6 degrees at dist. plus say 24 on table is really 30? If I'm not correct in my thinking please correct me.

 

you are correct

 

provided the chips base timing setting is zero. Which is not usually the case i dont think believe it or not.

 

so instead of doing what hypertech does for their stage 2 chips, (bump timing at high rpm/map)

we should bump em up during mid and low rpm/maps and leave the high rpm low vac numbers alone?

i know the answer to this, i just thought it should be explained from a few different, more clearer points of view.

 

ok im running a hypertech stage 2 chip now with base timing, i asked them if i should run any advance and they said no, what are your guys thoughts on this? i know i know you cant tell till you do it but i dont wana waste my time if im just going to set it back to straight up.....

 

I have the Stage II also, and I wondered the same thing. I posted the same topic, and JPrevost replied and said to do it because the chip only increases the air/fuel ratio and not timing. Now, I have learned to trust JPrevost on just about everything that applies to our engine.
I was thinking though, maybe he mis-understood me and thought I had a Stage I. I think that the Stage II does bump the chip timing, for the reason that it requires 93 octane and a low temp thermostat, as well as the fan switch-which are all relate to advanced timing.
Anybody know for sure?

 

ive personally read a 7747 hypertech stage 2, it did change the main spark table.

Jon sent me a bin for our cars that was a hyp stage 2 and i dont remember if it changed it or not.

so, maybe the do maybe the all dont.

what i was getting at was that you most likely your car can use a few degrees advance durring middle rpm maps but that you should keep your wot maps as constant as possible as if it were not computer controlled.

that was written and explained a bit better but iex crashed and i didnt feel like retyping so much

 

That graph is a comparison showing the hypertech vs the ANTT (stock). Considering our cars can run no problem on 89 octane with base timing set at 6 to 8 degrees more than stock...I'd say this eprom is a waste. Our cars are already not running enough timing mid range so by bumping the base timing from 0 to 8 and you've made MORE progress.
It also moves the tcc lock/unlock in both high and low gears up ~ 11mph so that you notice a difference in the cars driving attitude at part throttle. Once you get a heavy foot the tcc doesn't lockup so it's got nothing to do with performance unless you're one of those guys that likes to race other people with part throttle .
Everything else is exactly the same. Even all the fuel parameters which include all the air fuel ratio's, pump shot tables, and volumetric efficiency tables 1 and 2 (the adder table).
They want you to use those other parts like the fan temp and higher octane so that you again feel a difference in how the car runs...not always for the better. I really am disapointed with hypertech and all those chip tuning companies. They offer a stock replacement eprom that is only good for a stock car but for the $$$ that you spend on it you could be burning your own eproms and/or doing other practical mods.

 

when you reset base timing on the dist to 6-8, you change it on the base timing on the chip right. in the ecm constants. That is supposed to match what you have actually set base to right? or does that cancel out what you just tried to do by retarding your entire spark curve on the chip by what you wanted to advance it.

 

Yes the constant in the eprom is "supposed" to match what is actually on the engine. It doesn't have to be and if you don't program your own eproms then the ecm might say 24 degrees advance but in reality it's 32 because you bumped the base from 0 to 8.

 

prevost? leave the timing at base with that hyper chip or advance it? read my upper post if you could , lemme know your thoughts

 

With hypertech, I don't think you could even advance much without getting some knock at WOT. I would hook up winaldl, datalog so you know exactly when you're getting knock, and just keep advancing the timing until you get some. Then back it off until you can't run the same mph in the 1/4 mile. Then you go up a tick.
With a stock eprom I would start running with 8 base and see if I was getting any knock, if I was I'd try the higher octane and see if that helps. If not, just back off the timing a little and you're probably good to go. It's funny how timing works, it's SO important and this is why the diy-eprom guys hate the aftermarket chip companies. I think the only really good thing about EFI isn't so much the fuel deliver (decel is always good but..) as it is the timing controls. So much potential to unlock the rest of the power. It's like somebody doing huge cam/heads/intake and leaving stock LG4/L03 exhaust manifolds! Best part about the eprom burning stuff is that it doesn't get useless after a point. You bolt on the parts and then you tune it to make the most power, how can that be a waste of money? Oh well

 

well i never put anything other than sunoco 94 in the bird......as for your suggestion i have no clue what winadl and dataloging is so i think ill leave it alone, seems like too much work for a non techy

 

so can i just boost the chip timing 6-8 degrees and then not worry about messing with the dist?

I would rather put in a new emprom than pop the hood.

 

Hmmmm.. Sounds like me at the moment.