Questions about Hondata technical info re high vs low frequency VSS sensing

[rufusbob]

In researching this site in planning a kswap, I’m confused by a couple of things. Maybe they’re typos that warrant correction, or maybe I’m REALLY confused?

Please reference my comments inserted in a copy / paste below from this site …

Thanks for your attention.

Bob

“Technical Information K20 Transmissions
Introduction

With regard to the speed sensor there are two types of transmission sold with the K-Series.

Low frequency type transmission

Found in the 02-04 RSX and 02-05 Civic Si.
Signal from the speed sensor is at a low frequency.
Speed sensor is at the rear of the transmission, run from the final drive at a low frequency.
The signal from the speed sensor goes both to the ECU and to the gauge cluster.
High frequency type transmission

Found in the 05-06 RSX, TSX and 06-07 Civic Si.
Signal from the speed sensor is at a high frequency.
Speed sensor is at the front of the transmission, from the teeth on 3rd gear.
The signal from the speed sensor goes only to the ECU. The ECU sends a low frequency signal to the gauge cluster. Should read “high” frequency, right?
Matching Components

The following components need to be matched in order for the ECU and gauges to work correctly:

The transmission output speed signal frequency (low or high).
The engine and dash wiring (low frequency design splits the speed signal between the dash and ECU, high frequency design goes from the transmission to the ECU and from the ECU to the dash).
The ECU internal conversion of transmission pulses to speed (in KManager the low frequency type is the default, the high frequency type can be used if the 'Countershaft Driven Speed Sensor' option is selected).
The ECU output of speed pulses to the dash (not present with the low frequency type, necessary with the high frequency type).
If all these components are not matched, then either your ECU speed or your dash speedometer will not work (or both will not work). Repeat: all these components need to be either the low frequency design, or the high frequency design.

How does K-Pro work on the 05-06 RSX?

The speed sensor is the high frequency type.
The engine and dash wiring is the high frequency type.
In KPro you set the speed signal conversion to high frequency ('Countershaft Driven Speed Sensor').
Hondata modifies the 02-04 ECU to provide a low frequency speed output to the dash.
From the last point you can see why an ECU prepared for a 05-06 RSX is different from one prepared for a 02-04 RSX.

How can I get an 05-06 transmission to work in an 02-04?

Everything has to be either low frequency or high frequency. You can either make the transmission into a low frequency type, or the vehicle into a high frequency type.

Converting a high frequency transmission to a low frequency transmission:

Either drill and tap the rear speed sensor location to accept the 02-04 speed sensor, or swap transmissions cases. Should read “clutch” case, right?
Add the speed sensor drive ring to the final drive.
…”

[rufusbob]

My apologies. In rereading “The ECU sends a low frequency signal to the gauge cluster.” I realize that is correct.

But I believe that an option to convert a high frequency ‘05-‘06 transmission to produce a low frequency signal to the gauge cluster involves swapping the clutch housing.

Can you please confirm that a speedometer Drive gear can be installed on a high frequency final drive? I’m assuming it can be pressed onto the differential housing.

Thanks,
Bob

[Spunkster]

What ECU are you using and what is the serial number that is on the K-Pro board inside the ECU?

[rufusbob]

Hi - Thanks for your reply.

I’m planning out a K swap into my ‘87 CRX Si (w/o A/C) before ordering any major parts, like the engine, transmission or ECU. I have purchased some parts such as a Hasport mount kit and some body, suspension & brake parts.

Wanting to use a complete ‘06 K20Z1 RSX Type S (naturally aspirated) engine and ‘06 RSX Base W2M5 5-speed transmission. ECU function will be limited to what’s required for engine operation. My application apparently calls for the ‘04 RSX Type S 37820-PRB-A08 as a donor ECU for modification into a KPro ‘05-‘06 RSX ECU. Will this work?

The ‘05-‘06 RSX KPro provides a low frequency signal to the instrument panel. I wish to retain the stock dash & speedometer, and am looking at a SpeedHut SpeedBox to convert a low frequency VSS signal to drive the CRX speedometer by cable. Input requirements for the Speed Box are 1v - 100v and 500-250,000 pulses / mile. Can you please confirm the output signal from the ‘05-‘06 RSX KPro to the instrument panel falls within this range? Thanks.

Note that the smaller CRX 185/60-14 tire size (about 887 revs / mile) and my intended W2M5 final drive change from 4.389 to 4.0 are offsetting, and result in my countershaft revs / mile being negligibly different from that of the ‘02-‘06 Base RSX.

Thanks for your help.

Bob

[Spunkster]

If you are using a cable driven speed sensor, is there an output of the speed signal from the cluster?

[rufusbob]

Nope. The SpeedBox converts a low frequency VSS signal to rotary motion to drive a cable driven speedo. (Maybe not the most elegant solution, but ?should? get the job done in this kind of application.)

Thus, I’m hoping the SpeedBox can use the low frequency signal the ‘05-‘06 RSX KPro puts out to drive the ‘87 CRX’s cable driven speedo. This would be independent of how the ‘05-‘06 RSX KPro uses the ‘06 W2M5’s high frequency signal internally within the ECU for engine control functions.

Regards,
Bob

[Spunkster]

The 05-06 K-Pro is only for use in an actual 05-06 RSX and should not be used for engine swaps. You should use a standard K-Pro for this. As long as it is done by Hondata it will have the ability to output a signal from the ECU if a VSS is input to the K-Pro.