Turbo Plus kit wiring question

carnut222 · 2025-03-22T23:46:49+00:00

OK, yeah I know I should just get an MBC, but I have this Turbo+ kit from my original 88 740T (LH2.2)…and now installing it in the 91 240 B230FT project. Pic...

jamesinc

Pin #22 on the LH-2.2 ECU goes low impedance to ground when the mixture is rich, and high impedance when the mixture is lean. It's always a path to ground, but when the pin is in a high impedance state, the amount of current flow is so minute compared to the size of the load that the circuit is effectively switched off.

carnut222

jamesinc Ahh, OK then, I think if I ground terminal 2 on the Turbo+ control module, that should fool it into thinking the mixture is rich, which should allow it to work. Currently I don't have it connected to anything, so that would mean it would be thinking it's a lean mixture, right? Easy enough to test…will report back!

carnut222

OK, so earthing terminal 2 on the Turbo+ control unit didn't enable it to work. Unless anyone has any other ideas in how to "fool" the control unit that it's receiving a signal from the nonexistent LH2.2 Terminal 22, I think I'll just connect terminal 3 on the throttle switch directly to terminal 1 on the overboost solenoid valve as per my original trials. This enables overboost at WOT regardless of RPM. My experience is it takes a while for boost to build anyway, so it's unlikely it would boost too high at low RPM unless going up a long hill pulling a trailer or something, so yeah, easy and done, and no need for the Turbo+ control module. Oh yeah, and I'll always run 98 octane fuel…obviously! 🙂

jamesinc

Why don't you try the opposite, try bringing pin 2 up to 7.5V?

carnut222

jamesinc I guess I could, but that seems like it's what the LH2.4 Turbo+ control box is looking for, whereas this Turbo+ kit is from an LH2.2 car…

jamesinc

Try grounding it through a resistor? The LH-2.2 switching circuitry on pin 22 has a 511 Ohm resistor in front of it, if you used anything in the vicinity of 0.5kOhm imo that would be good enough.

It's also possible the Turbo+ controller has some internal problem, or that it is more sophisticated than we are giving it credit for, and looking for a signal that goes high and low periodically.

jamesinc

Also, just throwing this out there… Dirk (Stonis World) seems to know a lot about them, even if he documented it years ago he may have some idea how to trick it, maybe try emailing him? https://www.stonis-world.com/contact.html

carnut222

jamesinc Thanks - I found this troubleshooting info on stonis web page…not sure it's for the LH2.2 or LH2.4 Turbo+ but seems to indicate terminal 2 voltage >5v is required…so might give that a try. That's consistent with the LH2.4 value of 7.5v, but worth a try I guess. Thanks!

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