How does k-pro determine what gear you are in?

K-Series Programmable ECU installation questions / support issues
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chunky
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How does k-pro determine what gear you are in?

Post by chunky »

I was looking at some datalogs tonight and I noticed that my VSS reads all out of whack at times. K-pro sees the wrong gear as well - seeing 6th gear when I'm in 3rd and then 4th. The VSS seems to read correctly during normal driving. I only observe issues during wide open throttle. I have never noticed my actual speedometer jumping around during a pull.

I have a PRB ecu in a 2002 civic si. The VSS was replaced a few thousand miles ago (corroded contacts old one, speedo on cluster showed zero at all times, new sensor fixed problem). The transmission is a rsx-s + ep3 final drive (2005 RSX gear ratios). The diff from my EP3 was retained, so the speedo gear matches the speedo sensor.

I've included two datalogs. One of a 3-4 gear pull, and another of random driving around.
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Datalogs & calibration
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Hondata
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Post by Hondata »

It's from electrical noise. Go through the engine swap checklist http://www.hondata.com/techk20swaps.html, particlarly the spark plugs and number of engine grounds.
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Spunkster
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Post by Spunkster »

I would check your grounds and possibly faulty wiring. It appears to be correlated to the vtec pressure activating.
chunky
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Post by chunky »

Hondata wrote:It's from electrical noise. Go through the engine swap checklist http://www.hondata.com/techk20swaps.html, particlarly the spark plugs and number of engine grounds.
I have a 100% stock engine harness. Never had to change it. I'll double check all of my ground points, the terminals on the VSS itself, and the harness plug.

Thanks for the advice.
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chunky
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Post by chunky »

Spunkster wrote:I would check your grounds and possibly faulty wiring. It appears to be correlated to the vtec pressure activating.
Good obesrvation. When VTP & VTS go on, things go nuts. Thanks for the advice.

For my own benefit, I'm still curious as to how k-pro knows what gear you're in. I'm assuming it's calculating it based on speed & rpm?
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thesilverbullet
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Post by thesilverbullet »

you're right its a calculation based on speed, rpm and the gear ratios loaded into the gear tab of kmanger. lookup gear ratios in help files of Kmanger for details...
'07 S2K w/ JVT header, Berk 3" header back w/ TP Exhaust, AEM V3 CAI & Flashpro
'02 RSX-S w/cai/exhaust/dcrh/kpro - SOLD
chunky
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Post by chunky »

I got a chance to mess with the car tonight. All of my grounds were properly connected. I went ahead and cleaned up all the ground connection points with some light grit sandpaper to make sure that they were 100% clean. I removed the passenger side motor mount and bracket from the block. It had significant oxidation on the contact surface between the block and the side motor mount. I cleaned that up with sandpaper & cleaning solvent. I bolted everything back together and took her for a spin. The problem is not 100% gone, but the condition has improved.

The passenger side motor mount, valve cover, and transmission grounds are all cleaned up. I may remove the transmission ground bracket from the transmission housing and clean up any oxidation at that interface. I also plan to remove the alternator and clean up any oxidation at its contact points with the water housing.

I will also try out a couple of different ground locations for my battery (deka etx14) which has been relocated to the rear of the car. I used to have it grounded to the seat belt bolt in back seat, but when I removed the 0 gauge wire in favor of 4 gauge, I put the ground strap on one of the bolts that is for the safety tether hook points. I looked through some of my old datalogs, and I had no issues with the speed seen by k-pro prior to last year. So I know that things used to work even with a relocated battery.

If things do not improve, I may try adding a few additional grounding straps to improve the grounding between the VTEC switch and the chassis.

Either way, I'm sure it's a grounding/electrical issue at this point, so thanks for pointing me in the right direction. :)
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chunky
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Post by chunky »

Just thought I'd update with the happy ending. I finally found my electrical gremlin. After checking continuity between all the grounds, checking continuity between each sensor's ground and the chassis, I ruled out the grounding system. I then checked voltage at the battery and at the fusebox. I read the exact same voltage at my battery (in the trunk) and the terminals (under hood).

Eventually, I pulled my speed sensor. Looking at the pins of the connector on the wire harness, I thought they looked like they could use some cleaning. I sprayed them down with WD-40 to loosen up any corrosion. I let it soak, then sprayed it out with non-chlorinated brake cleaner. I bent the pins in the sensor slightly to increase the contact pressure between the sensor pins & the harness pins. I plugged it back up and the VSS is smooth again. :)

I'm guessing the problem started from when coolant spilled into my old VSS at some point during a head swap or other occasion when the rear heater hoses were removed. The corrosion killed my factory VSS, so I got a new one and everything seemed to be fine. However, I never properly cleaned out the harness plug until now.

I will say that cleaning up all the grounds seems to have made a positive impact on the engine's overall smoothness as well as knock counts observed.
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