slickfx3

To gain some insight on timing as a whole, I have been goggling, wieghted distributors and vacuum advance have made cars go fast in the past, now and in the future, for the street gang anyways.

It like automatic, sensing vacume, etc to real time compensate.

it takes the tuning and guesswork out of tuning for the lazy/inept tuner like me...

sounds like old school, but classic. is there a way to convert to this? will it past smog?

or am I crazy?

http://www.onesicks10.com/CarbPDFs/IgnTiming.pdf

J_D_

Be pretty tough to pass smog, I'd think. That said the best ignition I ever had when racing my Nova was just locked at 34*. No advance at all. Nothing to go wrong. Ive thought about burning a chip like that to see what would happen.

slickfx3

why did you lock it at 34? from experimentation? sounds bizarre...

xch3no2

Holy step backwards slickman!

There's bats in the belfry!

slickfx3

yeah I have been retarding like crazy....

xch3no2

So we want to know why you are retarding, knock?

To replicate the mechanical vacuum advance I would want to graph it's operation on the engine, then apply those values to your SA tables.

In any case I'd think 35kpa & less values would be advanced.

Orr89RocZ

iTrader: (20)

You still have to setup the mechanical units to a certain base timing, and then set the weights and such to allow a certain amount of advance by a certain rpm and the vacuum stuff is the same way...it will add a preset value based on vacuum it sees. So its not like its automatically doing all for you..you had to set it up and tune it.

Its much easier to do the same thing in an ECM based table. Lower vacuum higher load rpms need less timing than higher vacuum light load rpms. In general, lower rpms need less timing than higher rpms. Those 2 trends are used to setup your timing table.

For emissions I dont know what would be best..that is something you'd have to tune. Adjust air fuel and timing and see what readouts come out the exhaust....thats hard to do since most people dont have free access to a smog facility test dyno/equipment.

Thats a way to do it if you wanted..lock all cells at 34. It can work ok in some situations but theres all that room for adjusting, it makes sense to take advantage of it. My 383 tune used locked timing of 28 deg at idle.... 35 in most all of the cruise cells i'd normally encounter in day to day driving and 34 deg locked at timing from 2800 on up in the WOT table. So basically a 3 step advance. A more advanced "locked" out timing curve if you will. Car drove great like that. The other motors/setups i've played with do not use that setup..its changing in all cells now

J_D_

This was a carbed street/drag car. Most drag cars will have 12* or so at idle with a mechanical advance, with 36 total all in by 3000 RPM or so. With a loose converter you reach full advance pretty quick anyway. Test & tune told me the motor liked 34*. Having it locked took away the moving parts for the advance. I had problems with the weights and springs in the past so I eliminated it. I would get the motor cranking and then flipped the ignition on so it it did not drag the starter. Worked great.

slickfx3

Everything I've read indicates a advance floor and a ceiling for all engines, based on gasoline's burn rate, VE, cam overlap, etc.

why on earth would a car ever, ever, need 28* at idle, it does not and will not make sense to me, it's at idle , it does nothing, that's why they call it idle.

they say at those speeds, the burn rate remaining the same can be triggered later, hence I found through my tuning in the past few days, the perfect 14*, at idle.

I read that SA can be conservative,based on compression, gas quality, weight of car, driving habits, and now AFR heads, cam etc.

That got me thinking, conservative meaning less advanced. and the fact that old school dizzies, go into a machine, not in the car to curve them. so this removed any knock events that may or may not occur until the dizzy was replaced. Major wiggle room.

Vacume serves the purpose of part throttle operation, address what I believe is the LV8 equivalent on our graphs. which I think this is easier than data logging. I find this more flexible, it may not get every tenth of a second, but in my case who cares.

to me in high load moments 128-208 lv8, max the advance to around 28-32* and watch the tach and index the knocks,and work the advance down.

I cut the retard in PE to 7*, when it was 15* the retard was so severe it cost the run. at 7* the car still moves forward with urgency, making me think that I am within 5-7 degrees for that RPM. which is not alot, I pull 1 or 2 degrees and when the knocks it gone, I think I am there or real close.

In the old days I tuned the car's advance by ear, these were normal street cars, and this was the best way, for me anyways.

in low load situations, I mimic vacuum advance adding or the stardard 10 degrees so thats 38-42 at under 112 LV8, and drive the car to high rev's with a partial throttle. litsining for issues,....none.

of course the base table will serve as the template so I can rise and fall rates and relationships based on this, and do some smoothing for obvious, unwarranted dips and spikes.

and i am please to report without datalogging, my car is a different animal, pulls very hard, no knocks, idles perfect.

my opinion about fueling after all of this is it needs to be tweaked, relative to the SA curve, they are to closely related and reliant on each other to operate independently,

that said fueling is still close, I could leave it or play with it.

so all these comments I see about set it at 34* and forget it is not that bad of an idea, simple works...

I want to add that my" all in" timing occurs at 2000 rpm and fades back with higher revs, I don't know if that is normal rise rate, but no problems here, so far.

J_D_

I will not get to do any SA tuning this year. Only get one more trip to the strip and thats if it doesnt rain. Next season, I think I'll try a chip with little or no curve to see what happens. I know the Nova worked well, but it was a very different animal than this car. This car has a Miniram on E85 and it likes a lot of advance, quick. It sucks that summer is over, here in the midwest, too many projects, not enough time.