tcu

[Rome702]

The H23 transmission's gearing is between that of the H22 and F22. It is shorter than the F22's gearing.

The H23 revs higher than the F22, but only by 200 rpm.

The powerband has nothing to do with the transmission. It is where in the RPM range that the engine makes power. The transmission (and the electronics that dictate when it shifts) only determines how high the engine will rev before shifting, and how low the RPM will be in the next gear. The ECU doesn't tell the TCU to shift, nor does it interpret the RPM... RPM is physical, not something interpreted by a computer. It is a constant.

If your gearing isn't suited to your engine's powerband, and your TCU is telling the transmission to shift too early or too late, you're going to be driving in a dead zone. In order to be effective performance-wise, they need to be properly matched.

As I said, it won't hurt anything, but it may not do anything but change the way things feel when driving your car. And with the H23 TCU, probably not a whole lot.

his ecu is from an f22 not an h23, and the ecu has to relay the info from the vss to the tcu allowing for it to change gears. the tcu does not connect to the vss and does not read the rpms, that is the job of the ecu. that is why you can chip the ecu to adjust the rpm range of a shift, as well as programming a stall converter and what rpms you engine will idle. If this info went straight to the tcu, then you gauge cluster wouldnt work as well as all the sensors in your motor. The tcu only keeps track of what gear you are in and what gear to shift to, based off of the info the ecu sends to it. Otherwise, you wouldnt be able to use an automatic ecu (obd1) in a 5speed conversion, cause it would not read your rpms or speed.

[deevergote]

Ok, I suppose that makes sense. Still, if the ECU gave the TCU the OK to shift, then what's the point of the TCU? The RPM info may be relayed to the TCU, but the TCU is what determines where in that range to shift gears.


I looked into a few things, and I've been able to find a number of TCUs on www.car-part.com listed as Prelude TCUs, for both H23 models and F22 models... both are listed as P15. It's possible that the Prelude S and Prelude Si had the same P15 TCU. That may not be the most reliable source, but there were a few of each listed... and the junkyard guys don't have any understanding of their meaning, usually. They're merely copying what they see on the part.

That would explain the P12 marking, just as the PT3 on the F22A6 head is simply because the same casting is used throughout the F22A range.

[Rome702]

Ok, I suppose that makes sense. Still, if the ECU gave the TCU the OK to shift, then what's the point of the TCU? The RPM info may be relayed to the TCU, but the TCU is what determines where in that range to shift gears.


I looked into a few things, and I've been able to find a number of TCUs on www.car-part.com listed as Prelude TCUs, for both H23 models and F22 models... both are listed as P15. It's possible that the Prelude S and Prelude Si had the same P15 TCU. That may not be the most reliable source, but there were a few of each listed... and the junkyard guys don't have any understanding of their meaning, usually. They're merely copying what they see on the part.

That would explain the P12 marking, just as the PT3 on the F22A6 head is simply because the same casting is used throughout the F22A range.

the tcu is for controlling the solenoids and syncros of the tranny, and keeps track of what gear to shift to (whether it needed to shift up or down). You dont technically use the tcu when your in sport mode either. really it is a colaberation of work between the ecu and tcu. the fact that his tcu is labeled with p12, i would say it is from the f series prelude