Both my 2005 and 2006 Insights will not lean burn above 2,650 RPM. It appears to be a limit coded into the ECU. As an aside, this isn’t the case with all Insights. I’ve driven a model year 2000 Insight that would happily lean burn to at least 2,800 RPM. But for me, 2,600 RPM is the upper limit of what I can reasonably expect to maintain lean burn at.
When this 2,650 engine RPM threshold is met, my Insights will refuse to re-enter lean burn for a period of time afterward unless engine RPMs drop significantly, or the ECU detects a gear change.
5th gear at 2,650 RPM in the HCH transmission is ~69 MPH. This isn’t an issue on level ground as I rarely drive over 65 MPH. However, on downgrades it is all too easy to accidentally exceed 2,650 RPM, and it can be nuisance to get lean burn back.
The HCH vehicle speed sensor or VSS is not geared the same as the Insight. The HCH speed sensor will cause the speedo to read 7.6% too fast. This means that when the cluster says 70, you will be actually traveling 65 MPH.
2007-2008 Fit sensor on the left. 2003-2005 HCH sensor on the right.
If you want to get close with an OEM part, you can install a speed sensor from a 2007-2008 Fit. Then your speedo will read only 2.2% fast. This means that when the cluster says 70, you will be really be traveling about 68.5 MPH.
For me, this is still too much error. If I decide to leave the HCH transmission in my car long term, I will pursue some kind of VSS calibration method.
According to the counting I did: The Insight’s speedometer drive gear has 27 teeth and the VSS has 23. The HCH speedometer drive gear has 24 teeth and the HCH VSS has 19. The Fit VSS has 20 teeth.
HCH input shaft on the left. Insight on the right.
The shoulder on the HCH mainshaft/input shaft will need to be machined down to make room for the pilot bearing.
Insight Transmission Above
HCH Transmission Below
The Insight and HCH transmissions share the same bolt pattern for the driver’s side motor mount. Despite this, there are a few issues that still need addressing. Unlike the Insight transmission which uses two M10 studs and one M10 bolt, the HCH trans uses two M12 studs and one M10 bolt.
It will be necessary to acquire two M12 Flange bolts. I recommend Honda part# (94050-12080).