09-15-2005, 02:17 PM
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 Quote:
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Originally Posted by nicke
I'm not using a crank sensor, I'm planning to use an 81 Spider dizzy with a hall sensor instead.
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The "Wasted Spark" system (like the alfaholics replica) doesn't require a cam phase sensor, only the crank one. I think this system is the simplest one to fit to a Twin Cam Alfa engine. The crank sensor won't be difficult to
install. Just use a 75/Milano EFI engine pulley.
The independant coil system will require a cam phase sensor. Due to the inner cam chain belt, it isn't possible to install a cam phase sensor on the camshafts. It could be installed in the former place of the dizzy. It rotates at the same velocity of the cam shaft. I don't know if the EFI system accepts the hall effect signal or the magnetic signal (the Alfa Romeo standard electronic distributor on the Alfa 75) as a cam phase signal.
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João Vale
1969 Alfa Romeo GT 1300 Junior
1972 Alfa Romeo 2000 GT Veloce
1976 Porsche 924
1991 Mazda Miata MX5
Last edited by jpv; 09-15-2005 at 02:26 PM.
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09-15-2005, 02:21 PM
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The iginiton is controlled by the ECU (computer) and the hall sensor in the dizzy booth signal TDC and RPM to the ECU, and the ECU sends the spark to the coil. Just like an electronic system.
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09-15-2005, 02:34 PM
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Quote:
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Originally Posted by nicke
The iginiton is controlled by the ECU (computer) and the hall sensor in the dizzy booth signal TDC and RPM to the ECU, and the ECU sends the spark to the coil. Just like an electronic system.
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I think there is a lot of gains to make just on the ignition system. You won't take full advantage from your engine that way. It's more important ot fit a electronic ignition system over the electronic fuel system...
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João Vale
1969 Alfa Romeo GT 1300 Junior
1972 Alfa Romeo 2000 GT Veloce
1976 Porsche 924
1991 Mazda Miata MX5
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09-15-2005, 10:25 PM
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I also use just a modified distributor with hall sensor for my ignition, but the distributor is locked to e.g. 10° BTDC, and all the rest is done by the ECU. Taking a distributor does not mean that the ECU can´t control the ignition map (i have programmed a individual ign. map on the dyno). It´s just the most simple way to get a fully ECU-controlled ignition with just one coil.
Take a look:
Pay attention to the special headphones (a special kind of "knock sensor"):
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09-16-2005, 03:21 AM
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Quote:
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Originally Posted by nda9h
I also use just a modified distributor with hall sensor for my ignition, but the distributor is locked to e.g. 10° BTDC, and all the rest is done by the ECU. Taking a distributor does not mean that the ECU can´t control the ignition map (i have programmed a individual ign. map on the dyno). It´s just the most simple way to get a fully ECU-controlled ignition with just one coil.
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João Vale
1969 Alfa Romeo GT 1300 Junior
1972 Alfa Romeo 2000 GT Veloce
1976 Porsche 924
1991 Mazda Miata MX5
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09-16-2005, 04:05 AM
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Well, my technical english is not very good, but i try to explain:
My setup is the "normal" way the first electronic ignitions worked (e.g. VW Golf 2 GTI 16v- dizzy fixed, ignition map in the ECU)
The ECU sets the point when to fire the coil. Thats (in my engine) between 50° BTDC and 10°BTDC. A fixed dizzy does not mean a fixed ignition. The dizzy does not directly control the coil, the ECU is between both!
The ECU gets a signal from the dizzy, and it knows that each signal means "piston is 10°BTDC". I have a hall sensor cap with 4 holes (thats what i "told" the ECU: 4 cylinder 4-stroke engine, dizzy used, fixed to XX°BTDC, hall sensor, cap with 4 holes), so the ECU gets a signal from which it can calculate 1) the RPM and 2) when to fire the coil.
Other solution is of course to get rid of the distributor, that´s what you´re talking about. 2 double coils ("wasted spark") or 4 single coils are possible, but that means another sensor setup !
Thomas
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09-16-2005, 06:04 AM
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Quote:
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Originally Posted by nda9h
My setup is the "normal" way the first electronic ignitions worked (e.g. VW Golf 2 GTI 16v- dizzy fixed, ignition map in the ECU)
The ECU sets the point when to fire the coil. Thats (in my engine) between 50° BTDC and 10°BTDC. A fixed dizzy does not mean a fixed ignition. The dizzy does not directly control the coil, the ECU is between both!
The ECU gets a signal from the dizzy, and it knows that each signal means "piston is 10°BTDC". I have a hall sensor cap with 4 holes (thats what i "told" the ECU: 4 cylinder 4-stroke engine, dizzy used, fixed to XX°BTDC, hall sensor, cap with 4 holes), so the ECU gets a signal from which it can calculate 1) the RPM and 2) when to fire the coil.
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I said before that the normal advance curve that the centrifugal weights system offers isn't the ideal one for an engine. There is a lot to be gained with a fully electronic (2 or 4 coils) system.
You say that your dizzy is fixed, it can't be because the ECU gets info out of it. That info is the advance curve of the weights mecanism.
If you have a fixed dizzy with no wheigts advance system you have to have a crank sensor so the ECU knows when to fire the coil. With that system you can upgrade it to "wasted spark" withou fitting another sensor.
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João Vale
1969 Alfa Romeo GT 1300 Junior
1972 Alfa Romeo 2000 GT Veloce
1976 Porsche 924
1991 Mazda Miata MX5
Last edited by jpv; 09-16-2005 at 06:10 AM.
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09-16-2005, 06:37 AM
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Quote:
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Originally Posted by jpv
If you have a fixed dizzy with no wheigts advance system you have to have a crank sensor so the ECU knows when to fire the coil. With that system you can upgrade it to "wasted spark" withou fitting another sensor.
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But when i upgrade to a multi coil system (2 or 4 coils), then i have to use a second sensor, beause then the ECU has to decide which coil to fire. That can´t be done with only one sensor.
Believe me: what i have done works, and i have done it all by myself (so i know where i have a sensor and where not...  )
Thomas
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09-16-2005, 07:53 AM
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My dizzy will be fixed and have all the mechanical advance mechanisms taken out just like nda9h's car.
The ecu knows where the TDC and what cylinder is due to fire with the Hall sensor in the Dizzy, the spark "jumps" quite far if needed depending on the advance and the ECU fires the coil. Not as pretty as 4 coils and a crank sensor, but better than a mechanical dizzy.
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09-16-2005, 06:38 PM
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Quote:
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Originally Posted by nicke
My dizzy will be fixed and have all the mechanical advance mechanisms taken out just like nda9h's car.
The ecu knows where the TDC and what cylinder is due to fire with the Hall sensor in the Dizzy, the spark "jumps" quite far if needed depending on the advance and the ECU fires the coil. Not as pretty as 4 coils and a crank sensor, but better than a mechanical dizzy.
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Quote:
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Originally Posted by nda9h
My modified VW dizzy has NO mechanical advance! And i do not have any sensor besides the hall sensor in the distributor.
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Ok. Then the hall sensor acts like a crank sensor. It informs the ECU of the TDC.
With a hall sensor fitted on the dizzy, the crank sensor can be dismissed and you can fit a 2 coil "wasted Spark" system without fitting another sensor.
Don't get me wrong, I just want to get some info on what you have done. Thanks for your replies!
Can either of you guys show me a picture of your dizzy? From what VW did you get it from? Have to look it up...
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João Vale
1969 Alfa Romeo GT 1300 Junior
1972 Alfa Romeo 2000 GT Veloce
1976 Porsche 924
1991 Mazda Miata MX5
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09-16-2005, 06:49 PM
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Just to make it more clear. This is the system you're using. Instead of the crank sensor it has a hall effect sensor on the dizzy.
One thing that confuses me is the fact that the dizzy rotates at half the speed of the crank. The ECU just wants the TDC point right? Thats no problem. But if you need that the ECU knows the rev speed of the engine for something else (ex: shift light) it will be wrong right? It will only measure half the speed.
Does the ECU have any feature that acconts for this situation?
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João Vale
1969 Alfa Romeo GT 1300 Junior
1972 Alfa Romeo 2000 GT Veloce
1976 Porsche 924
1991 Mazda Miata MX5
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09-16-2005, 07:14 PM
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Quote:
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Originally Posted by msiert
Do you want a closed loop system that wil adjust the air/fuel mixture automatically?
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João Vale
1969 Alfa Romeo GT 1300 Junior
1972 Alfa Romeo 2000 GT Veloce
1976 Porsche 924
1991 Mazda Miata MX5
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09-16-2005, 07:54 PM
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That schematic is what I'm building, but with a Hall sensor Dizzy from an 81 Spider.
A closed loop system dosen't need a knock sensor, what the knock sensor does is affect timing. Like when you use a lower grade petrol and the engine pinks and presto the timing gets retarded. To run closed loop all you need is the o2 sensor, the closed loop is between the o2 sensor and the ECU/squirt timing. Closed loop is usually turned off during hard acceleration.
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09-16-2005, 08:37 PM
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Quote:
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Originally Posted by jpv
To make a closed loop system its necessary to install a knock sensor. I've read at Jim Steck's web site that the Alfa Twin Cam engine is too noisy and the Knock sensor doesn't give a correct reading. Has anyone sucessfully installed a closed loop system?
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Some of the better aftermarket controllers us linear O2 sensors so that you can run a controlled a/f anywhere, as opposed to just stoich for a typical a/f sensor.
If you want to be not as rough to the environment, use a basic O2 sensor and a catalyst. If you have questions about that, PM me- that's what I get paid to do every day.
Control wise, if you have carbs, just adding EFI will be a big improvement, even w/o spark control. SPICA is better, in terms of control, so the benefit is a little less.
If you plan on running any boost, then spark control is required.
For the most part, I find that any controller does a very good job- and the HUGE tables that some controllers use are not that great- it's just more work. The code writer would spend better time learning how to linearly interpolate in a table vs. having massively huge tables. For instance, our production spark tables are generally only 8x8. Fuel is actually a lot less, but that has to do more with the style of control.
Basically, do your research, and know what you are getting yourself into.
One more thing- be careful about fixing the distributor. If you don't get it aimed right, you may get some cross spark to other points. If you match TDC to point at a wire node, you should be ok. But do check it out. It's more of a problem with 6's, and worse with 8's.
Eric
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