California98Civ

The VSS is used to judge speed, obviously, but does the ECU in a sixth gen Civic DX also use its 0-5v pulses to judge distance? I'm guessing yes, but I cannot find a definitive answer in the 1996-1998 Honda Service Manual (or here or online).

Thanks in advance for any info. I am running a 5th gen tranny now (just swapped) and those cars had 13" wheels stock, while the sixth gen had 14" of course. Trying to figure out the odometer difference.

kyden

distance? no. the ecu doesn't care how far you go. it only needs road speed for vtec + gear correction.

California98Civ

Then how does a manual trans civic gauge distance traveled, if not using the VSS? Couldn't the number of pulses coming from the VSS gear inside the tranny just as easily tell the ECU how many revolutions of the wheels there have been and thereby report a distance calculation for the odometer?

kyden

the odometer and the vss input at the ecu have nothing to do with each other.

California98Civ

Okay, thanks. But then how is the odometer getting the data on distance? Is it a cable? That seems not likely. Is there another sensor besides the VSS that supplies data for the distance calculation?

kyden

no. voltage is sent to the cluster, and it powers the counter in the cluster.

ElectronBlue00

Care to explain why the Odometer stops reading once you unplug the VSS ?

ElectronBlue00

https://honda-tech.com/forums/honda-civic-del-sol-1992-2000-1/does-vss-control-odometer-well-2584063/

grumblemarc

iTrader: (4)

Doesn't mean that the ECU reads distance.

ElectronBlue00

That is correct

grumblemarc

iTrader: (4)

So what's your point?

ElectronBlue00

To answer his questions.

1: Does the VSS Supply Distance data.
2: If the information is tracked by the ECU.

Answer: The VSS Supplies speed data to the Odometer so that distance may be tracked. The ECU does not record it, So checking the "pulses" as he said would not be the proper way to judge any difference in readings.

Though I believe the difference would be minor between the two rim sizes, the correct method to judge the difference between the readings with the different transmission he installed, I would not be 100% certain of.

kyden

i'm not sure where you are getting at either.

VSS signal is sent to the ecu and the cluster. (the signal to the ecu is piggybacked off of the signal to the cluster.)

The odometer stops when you unplug the VSS because the VSS is the input for the odometer. all 'calculations' are carried out at the speedo/odometer.

California98Civ

These last few posts, kyden and ElectronBlue00, are precisely what I needed to know. The VSS is the source, one way or another of the data that is turned into distance measures. THANKS! That means, of course, that a 14" wheel with stock 185/65-14 tires would undercount distance when the transmission was designed with 13" wheels and 175/70-13 tires. Only a little, maybe one or two percent. That's what I needed, thanks again.

EDIT: probably the only reliable way to test the extent of the difference would be using GPS or mile markers and comparing the odometer reading.

jbpnoman

Or just do some simple math. 175/70R13 = 891.0 Revolutions per mile. 185/65R14 = 859 Revolutions per mile.

94EG8

For what it's worth the transmission and VSS don't really have anything to do with differences in rim sizes. 5th and 6th gen transmissions share near identical gearing when comparing trim level to trim level. Also both 5th and 6th gen civics had 13" and 14" wheels depending on the trim level ('96 only had 13" wheels on base models for 6th gens)

The long and short of it is Honda never bothered to compensate for the difference in tires. The difference was so slight it still let the speedometer/odometer be within acceptable limits for accuracy. In other words swapping out your 6th gen trans for a 5th gen wont affect your odometer at all.

California98Civ

The problem with that is that looking at tirerack.com's spec on tires will reveal that different tires in the same size category will have different revolutions per mile specs from the manufacturers. My tires are not on the site.

The fifth gen CX tranny and the sixth gen DX coupe tranny have really significantly different gearing, FD 3.250 versus 4.058, for example. And while fifth gear is the same, 1-4 are different, and taller in the CX.

I just did a test run on my return commute. I used ridewithgps.com to chart my trip because it takes into account elevation changes. My odometer under counted the distance by about 14%. I'll test it again tomorrow and Friday. I'm surprised by such a large under count. I don't believe my own results yet.

I wonder if it is possible that there is a difference between the design of the VSS on the two transmissions that messes-up the gauge cluster readout. What do you think?

Schister66

My thoughts exactly. They have to be tied to one another...the only other option would be using the ABS wheel sensors to calculate wheel rotations and extrapolate distance based on OEM tire size

94EG8

Yes, but a 5th gen DX trans and 6th gen DX trans are geared the same.

It really doesn't matter anyway and here's why: All '92 - '00 D-series transmissions use one of two speedo gears. EX/Si/HX use a the black speedo gear. Everything else uses the white speedo gear. All models use the same VSS gear. The speedo gear is pressed directly onto the differential carrier. The transmission gearing is totally irrelevant since this comes after it. For all intents and purposes the speedo gear is directly connected to the axles. Transmission gearing absolutely does not have any impact on the speedometer/odometer. I'm not sure why this didn't occur to me in my last post.

There's something wrong there, the difference should be about +/- 3%

No, there isn't. But if you really want to prove it to yourself swap in your old VSS, they're absolutely interchangeable.

94EG8

Also, before anyone says "well what about gearing differences between the black and white speedo gears?" There aren't any. The two gears are because of two different sized differential carriers and bearings. The outer diameter of the gears is the same, it's the inner diameter that changes.

I just went outside and snapped a couple of pictures to prove this since I just happened to have both laying around.

Black B000 "big bearing" speedo gear taken from a D16Y8 trans:



White A000 "small bearing" speedo gear take from a D15B7 DX trans:



It was cold and the LCD on my vernier caliper wasn't working well and it's hard to see, but both gears are 90.6mm. One says 90.7mm only because I wasn't very careful about moving the caliper while trying to get a decent shot. I'm also aware that neither measurement is accurate in terms of the actual size of the gear, my caliper wasn't deep enough, but when I did the actual measurements I measured from the same place. I had to let the caliper sit on top of the gear for the pictures because I only have so many hands.

California98Civ

Thanks for both of these last posts, man! Makes it all much clearer, and puts it up on the internet for others. Honda-tech.com is a great site. I'll have to figure out what I am doing wrong in my distance calculations and try again.



james

94EG8

This thread quite honestly reminds me of the way Honda-Tech used to be.

ElectronBlue00

Agreed!

Also.. what a very informative thread! I always love learning something new.