redman Posted February 7, 2023 Report Share Posted February 7, 2023 Hi hope you guys are cool! I am trying to wire my Xtreme for 2wire VTC solenoid and my tuner said I should use a half bridge? I guess this means Aux 9/10 for me, but do I wire one wire to 9 and one wire to to 10 and the ECU will give it the live and ground? Or do I just wire one wire to one of those Aux and the other wire to ground or live like a regular old boost solenoid or something? I think he wants more control than just "on or off", but I don't really understand. It is frying my brain but that is still better than frying my ECU Thank you! Quote Link to comment Share on other sites More sharing options...
Adamw Posted February 7, 2023 Report Share Posted February 7, 2023 A half bridge is generally an output that drive both high side and low side, but that term can be used a bit loosely in some circles. It is not needed for VTC, just a conventional low side drive aux is all that is needed. Connect one wire to any spare aux output (Aux 1-10) and the other side to ign switched +12V supply. redman 1 Quote Link to comment Share on other sites More sharing options...
redman Posted February 7, 2023 Author Report Share Posted February 7, 2023 14 minutes ago, Adamw said: A half bridge is generally an output that drive both high side and low side, but that term can be used a bit loosely in some circles. It is not needed for VTC, just a conventional low side drive aux is all that is needed. Connect one wire to any spare aux output (Aux 1-10) and the other side to ign switched +12V supply. That's cool, thank you Adamw, is it possible I misunderstood and it was VTEC that is best on a half bridge, not VTC? Would that make any sense? I was pretty sure VTEC is a straight up "on/off" solenoid going by the stock harness. On the stock harness both VTC solenoid wires go to the ECU instead of just one of the two wires from the VTEC solenoid. Is it maybe just a weird Honda thing? Quote Link to comment Share on other sites More sharing options...
Adamw Posted February 7, 2023 Report Share Posted February 7, 2023 Some OEM's high side drive the VTC solenoid (Honda and Subaru) but there is no specific need to, just what they chose to do. Some of the early Vtec hondas (B serias and possibly D series) they had a single wire VTEC solenoid where one end of the coil is grounded through the body so the ecu needs to switch the positive side. But still a half bridge is not needed, just a high side drive or more commonly just a relay. I suspect where the confusion is coming from is just the loose use of the term "half bridge". Motec for example call their aux outputs "half bridge outputs" just because they are capable of high side or low side drive, but you dont use them as a half bridge to drive a solenoid. They only work in half bridge mode if set up as a stepper motor drive or in a pair for E-throttle (but when 2 half bridges are paired like this it is usually called a full bridge). On the Xtreme Aux 5-8 are half bridge outputs, but we dont call them that as the only time they actually work as a half bridge is when set up as a 4 wire stepper. For all other functions such as VTC or idle valves they only function as low side or high side drives. redman and mapper 2 Quote Link to comment Share on other sites More sharing options...
redman Posted February 8, 2023 Author Report Share Posted February 8, 2023 That is an awesome explanation. Thank you! Sorry for all the questions but at least this will come up in searches now. Quote Link to comment Share on other sites More sharing options...
mapper Posted February 8, 2023 Report Share Posted February 8, 2023 The big difference on Motec's halve bridge is they can do. 10 amps compared to 2-3 amps of the other Aux types. Technicaly Adam is spot on. I guess most manufacturer name there outputs which can be cofigured to a full bridge - halfe bridge Quote Link to comment Share on other sites More sharing options...
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