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bctom · 01-29-2011, 06:25 PM

I found this short article on spark advance at this link:

http://www.rasoenterprises.com/index...-advance-curve

Dual Fuel Advance Curve
Sunday, 18 January 2009 13:20

When running a dual-fuel setup, ideally you should have both a gasoline advance curve and a propane advance curve. For older vehicles, Dual Curve makes a dual advance curve ECU for these applications under PN 40622. I contacted Dual Curve about the operation of their 40622 ECUs and they gave me the following response:

Regarding timing advance, the PN40622 is designed to give an additional 8-10 degrees of advance, after the distributor is recurved.

Please refer to the PN40622 instructions pg. 2:

“The Timing Recurve will electronically delay the factory set timing signal 15 degrees. The user must mechanically move the distributor timing ahead or advanced 15 degrees. Add 15 degrees to the original factory gasoline set point. With the 15 degree delay for gasoline, the Recurve can then provide timing advance for the higher octane LPG/CNG fuel. At idle on LPG fuel, only 10 degrees (CNG fuel, only 13 degrees) additional advance will appear on your timing device. The other degrees (5 LPG or 2 CNG) of timing are used to compute a smooth, accurate timing for RPM changes. After the (gray wire loop) fuel timing program is set-up and selected. The fuel selector switch will select the proper timing program via the yellow wire.”

You can use this ECU for straight LPG or CNG applications too. I believe the reduced timing advance when on LPG at idle would make the engine easier to start, which would be the main advantage for installing it on a straight (or dedicated) propane vehicle. However, I found that I have not had any starting problems with the advance curve used at the top of this page.

It was on this web site: http://www.rasoenterprises.com/index.php

There are also articles here on rejetting the carb, ignition and spark plug changes that are necessary in dual fuel conversions . They also state that your vacuum advance should definitely be hooked up. You might find the 195 degree thermostate too warm in the summer months. I don't have any experience running these engines at sea level, and I'm not sure how hot it gets in Holland in the summer time, so you will know better than me.

01-29-2011, 06:25 PM	#149
bctom Registered User Join Date: May 2010 Location: BC, Canada Posts: 15	Re: Improve mileage 350 with Quadrajet I found this short article on spark advance at this link: http://www.rasoenterprises.com/index...-advance-curve Dual Fuel Advance Curve Sunday, 18 January 2009 13:20 When running a dual-fuel setup, ideally you should have both a gasoline advance curve and a propane advance curve. For older vehicles, Dual Curve makes a dual advance curve ECU for these applications under PN 40622. I contacted Dual Curve about the operation of their 40622 ECUs and they gave me the following response: Regarding timing advance, the PN40622 is designed to give an additional 8-10 degrees of advance, after the distributor is recurved. Please refer to the PN40622 instructions pg. 2: “The Timing Recurve will electronically delay the factory set timing signal 15 degrees. The user must mechanically move the distributor timing ahead or advanced 15 degrees. Add 15 degrees to the original factory gasoline set point. With the 15 degree delay for gasoline, the Recurve can then provide timing advance for the higher octane LPG/CNG fuel. At idle on LPG fuel, only 10 degrees (CNG fuel, only 13 degrees) additional advance will appear on your timing device. The other degrees (5 LPG or 2 CNG) of timing are used to compute a smooth, accurate timing for RPM changes. After the (gray wire loop) fuel timing program is set-up and selected. The fuel selector switch will select the proper timing program via the yellow wire.” You can use this ECU for straight LPG or CNG applications too. I believe the reduced timing advance when on LPG at idle would make the engine easier to start, which would be the main advantage for installing it on a straight (or dedicated) propane vehicle. However, I found that I have not had any starting problems with the advance curve used at the top of this page. It was on this web site: http://www.rasoenterprises.com/index.php There are also articles here on rejetting the carb, ignition and spark plug changes that are necessary in dual fuel conversions . They also state that your vacuum advance should definitely be hooked up. You might find the 195 degree thermostate too warm in the summer months. I don't have any experience running these engines at sea level, and I'm not sure how hot it gets in Holland in the summer time, so you will know better than me.