# Why remove Distributor advance



## dburone (Apr 2, 2004)

I know that too much advance would lead to detonation, but when you step on the gas, the advance works because of the vacuum, but when boost starts it will stop working, right??


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## spdracerUT (Jun 11, 2002)

no. ignition timing is determined by throttle position/engine load and rpms and it's programmed in the ignition maps in the ECU. These maps assume that the base timing is set to some value. So you can advance the timing by adjusting the distributor which effectively changes the base setting. So the ignition timing will be advanced everywhere.


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## dburone (Apr 2, 2004)

spdracerUT said:


> no. ignition timing is determined by throttle position/engine load and rpms and it's programmed in the ignition maps in the ECU. These maps assume that the base timing is set to some value. So you can advance the timing by adjusting the distributor which effectively changes the base setting. So the ignition timing will be advanced everywhere.


Sorry, i didint tell, but my car is carbed so no ecu, no maps and those things.
The advance im talking about helps the car to start moving better when you step on the gas.
HEre i think it would work normally when there is no boost that is when i need it, and when boost builds up it will stop working and retard ingnition to its original position.
Am i right?


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## velardejose (Sep 9, 2004)

Hi
Thats the idea dburone
Our third world problem is we don't have access to programable ecus due to way overpriced importation channels
Besides there is nobody capable of tuning/programming it at least in my country...
Centrifugal advance is a solution that gives you an *aproximate * spark advance curve not taking into account throttle position or engine load
Ecus retard the timing when you floor the gas for example
At high engine power/boost levels too much advance can blow it in seconds 
Fixed advance is not perfect (minimum and part throttle), but at least you can control the ignition timing *exactly* for those high power/boost level conditions


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## dburone (Apr 2, 2004)

I agree with you a 100%, but its like i say, when boost starts the stock vacuum advance will stop doing its job and retard to stock timming.


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## velardejose (Sep 9, 2004)

Nice idea...
Maybe an 'inverted' vacuum advance that retards when pressure rises?
A bit of machining and a diafragm and you can build your own distributor 'inverted vacuum advance'
What do you think?


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## Zen31ZR (Mar 24, 2004)

Timing advance pretty much _has_ to go up as engine rpm rises, otherwise combustion will start happening later and later and eventually happen ATDC which can cause a big loss of power and also raw unburnt fuel being dumped into the exhaust. I've seen some cars with a timing advance in excess of 45 degrees in the upper rpm ranges (6000-7000). Remember, piston speed may go up, but combustion speed stays the same, so you have to "_move_" where the combustion happens in order for it to be useful in pushing the piston down in the power cycle.


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## velardejose (Sep 9, 2004)

The combustion needs a full milisecond to get under way
That's 18 crankshaft degrees at 3000 rpm, or 36 at 6000 rpm
This is an aproximation, because there are other factors like combustion chamber size, shape, valve number, usw
At 7000 it would be 42 degrees...


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## Zen31ZR (Mar 24, 2004)

velardejose said:


> The combustion needs a full milisecond to get under way
> That's 18 crankshaft degrees at 3000 rpm, or 36 at 6000 rpm
> This is an aproximation, because there are other factors like combustion chamber size, shape, valve number, usw
> At 7000 it would be 42 degrees...


Chamber size and all that I could see, but what does number of valves have to do with combustion speed. The valves are closed at that point (I should hope). Just curious......


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## wintercar (Nov 20, 2004)

dburone said:


> I know that too much advance would lead to detonation, but when you step on the gas, the advance works because of the vacuum, but when boost starts it will stop working, right??


Maybe you could use a check valve so your distributor never sees boost. Then just run your base a couple of degress retarded?

IIRC you were trying for 7psi? How does the boost feel?


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## velardejose (Sep 9, 2004)

Hi
More valve number = more turbulence inside the combustion chamber = less detonation = higher advance


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## Zen31ZR (Mar 24, 2004)

velardejose said:


> Hi
> More valve number = more turbulence inside the combustion chamber = less detonation = higher advance


Yeah, I shoulda remembered that. Brain fade.... :loser: That was what made the CVCC engines work so well.


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## velardejose (Sep 9, 2004)

dburone
How much advance are you using?
Is it fixed or centrifugal?
I am thinking about turbocharging an engine with 10° fixed advance
8.5:1 cr and max 10 pounds boost
My sc transmission is taking soooooo looong...


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## dburone (Apr 2, 2004)

velardejose said:


> dburone
> How much advance are you using?
> Is it fixed or centrifugal?
> I am thinking about turbocharging an engine with 10° fixed advance
> ...


I have it at stock timming, the distributor is electronic so im not sure how it works.
If you are going to turbo the e16, it hast 9.0:1 CR
Im at 5 psi of boost at the manifold but dont se that much power.


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