R.P.M.

iTrader: (3)

I'm just finishing a Weber 48 IDA powered 12A bridgeport and I'm just wondering where I should start out setting the timing?
Right now I have the distributor set pretty far advanced but its tough to get started. I'm just looking to get a general idea of where to initially get it set.

I'm not used to this old distributor stuff lol....btw Haltechs and EFI rock out

blown7

my old 48 ida and 12a bridge was about 5-10 degrees advanced. been awhile since it was in the car but my 13bpp is 20 degrees advanced right now from the stock markings.

My 12a bridge didn't like to start either if it sat more than a week and once it was built it was a bitch to start.

TomaSoft

I have the same problems.

I'm not sure about the ignition time setup at all.

I read allot but found too much different meanings.

My ignition is 100% locked and set to 24* advance.
The engine works well, but it starts very hard.

I'm not sure if 24* advance is OK for a 12A full bridge port.
I'm no sure either if 100% locked ignition is the best for bp.

Perhaps someone out there can help here so that I don't have to start a new thread about this.

ultimatejay

iTrader: (1)

If your running pump fuel you don't want to run any more than 26-28 btdc. If your running 100+ you can go much higher with gains. Every motor is going to be different, so you will have to try out diff. settings and go from there.

Regarding the locked dizzy- this is set up is mainly for racing/turbo applications and you low cruise low rpm power will suffer a little because you have so much advance early.

TomaSoft

If I understand well, I can set the ignition timing to 26 BTDC with my 12A bridge ported engine. And then try to find the best setting for my engine.
I thought 24 BTDC is the maximum for a 12A engine

Exactly that was also in my mind.
In the last race I missed a little power at low RPM.
As it was the first race for my bridge ported engine and the locked distributor, I was not sure if it is the engine or the dizzy or both.

I locked the dizzy as this setup was designed for track race application and I read somewhere that bridge ported engines don’t like idle a DTC.

If I go to 26 BTDC at 4000 RPM, with an unlocked distributor, my idle should be at 6 BTDC at idle; if I consider that the mechanical advance system advances 20 degrees. (Correct me if I'm wrong)

Does the bridge ported engine like 6 BTDC or should I modify the mechanical advance system to limit its range, to get a little more advance at idle?

I've prepared a dizzy that combines my custom 4 igniters, 4 coils setup (https://www.rx7club.com/general-rotary-tech-support-11/4-igniters-coils-dfi-setup-coils-l1-l2-fire-together-767776/) with mechanical advance, but as I will not find allot of time before the next race to make experiments, I want to be sure that is worth modifying the ignition.

peejay

Not always If you are experiencing poor chamber filling at those low RPM then it's actually a benefit.

I have never had a problem with starting, in fact my 13B(un)T in my car right now is set at 27 locked, no split. Now, when I "lock" a distributor, I just remove the springs. When cranking, in theory anyway, the advance minimizes and as soon as the engine lights the timing advance whacks wide open.

Old trick from 60's Chrysler engineers...

TomaSoft

That could solve my starting problems

But are you sure that the dizzy-weights come back to 'idle' position without springs at all?

I thought about finding the best BTDC angle to start and run my bridge ported engine at low RPM by modifying the mechanical advance system to get more ore less degree range if required and then go to optimum advance timing at higher RPM, with stronger springs even later than 4000 RPM if necessary.

Is DTC OK to start a bridge ported engine?
I read somewhere that bridge ported engines dont like DTC .....
At what BDTC should it run at low RPM range to get the maximum low RPM power possible?

peejay

The friction between the rotor button and the distributor cap should be sufficient to pull the advance back to minimum while cranking.

In the 60's, the points friction was DEFINITELY enough.

I'm no expert on BP timing... tried all sorts of things on the P port though... including 40 degrees by accident It really didn't seem to make much of a difference.

TomaSoft

I have no rotor and no distributor cap
I have 4 inductors, 4 transistors and 4 coils.
This works great with the locked distributor axle.

My problem too and in addition to this, there is not much time left before the next race to do excessive testing.
I just don't want to loose power at low RPM, that’s why I think about reconfiguring variable ignition timing.

Just need to know in which direction to go.

My main question is:
Can I get more power at low RPM range if I go to fewer advance?
(We still can discuss about the approximate timing setup later on.)

TomaSoft

No more answers?
So I have to go on my own.
I'll keep you informed

TomaSoft

I'll reinstall an ignition with mechanical advance.

I'm still waiting for suggestions on timing.