Usually it’s not a problem unless you have ‘advanced’ knock sensor programming. Usually the ‘slightly faster burn’ that BG promotes results in a ‘virtual’ advanced timing that increases power, so there is no need to retard timing. Note that I’m referring to using BG as a combustion catalyst, not as a fuel. When BG is used as a stand alone fuel, the ignition timing should actually be retarded to ATDC because the speed of burning hydrogen is so fast. BG as a carbon-fuel combustion catalyst just speeds up the combustion a bit, not to hydrogen burn speeds.
However: Vehicles with computers (CPUs) that use an ‘advanced’ knock sensor programming protocol have their CPU ‘listen’ to a knock sensor and advance the timing until there is a knock and then back off (retard) the timing just enough that the knock is gone.Generally, with carbon-fuel combustion, this is a good thing because the advanced timing gives the fuel a bit more time to burn and thus you get more power from it.BUT, when you change the fuel’s combustion characteristics, in this case by speeding up the combustion of the fuel by adding BG, this ‘advanced’ knock sensor programming causes a power loss. There are two main reasons this is so.First, as described above, the combustion takes place faster, so more of the fuel is burned (making higher compression) as the piston is rising. With ‘normal’ timing this is OK because not so much fuel is burned that it fights the upward movement of the piston.Second, and this is the clincher, the ‘advanced’ knock sensor programming advances the timing until there is a knock… But adding BG makes the combustion not just faster but much more knock resistant, so the timing just keeps advancing, too far! So now so much of the fuel is being burned BTDC and the combustion pressure is pushing down on the piston too soon; fighting the upward movement of the piston and you lose power.What can be done about it? One solution is to add a MAP or MAF Enhancer. If you convince the CPU that there is less air coming into the engine, it will retard the timing; at the same time as giving less fuel, a win all around.Another solution would be to cause an ‘artificial’ knock or a knock enhancing circuit but I haven’t gotten to that yet.