Gear detection issue with HLT and GoPoint BT1

[daphatty]

Forgive me if this has been discussed at length already. I searched though previous threads and wasn't able to find anything relevant to my issue.

First, my setup.

GoPoint Technology BT1 OBDII Sensor
Harry's Lap Timer Rookie (latest version available on app store as of this post, v17 I think)
iPhone 4 running iOS 6.1.3
2004 Honda S2000

Issue

For some reason, the Gear statistic is almost always wrong and I am unsure whether the problem originates from the BT1, HLT, or possibly the car itself. I've been able to verify this behavior within GPS Buddy as well. Typical behavior reports the gear in use as one or two gears lower than actual. i.e. First gear instead of second gear, fourth gear instead of sixth gear.

I plan on generating a debug log (as outlined in the debug FAQ, but I am suspicious that this may not actually be a problem with HLT. All of the other statistics seem to work just fine. Has anyone else encountered this problem? Any suggestions you could provide would be greatly appreciated.

[Harry]

Hi,

Gears are calculated from speed, rpm, wheel size, gear box ratios. This means you need to configure a vehicle with your car's specific values. Please check your vehicle settings from Vehicle List and enter the wheel and gear values for your car. Search for "gear ratio" here on the forum to find more information.

Harry

[daphatty]

Harry,

Thank you for the feedback. I followed your instructions and entered the missing vehicle data into the profile. While I have noticed some improvement, the displayed gear is still incorrect. In fact, now the displayed gear is off by exactly one gear. I tested this functionality using a similar program (Dash Command) and had identical results so I suspect I may be missing a small piece of information someplace. Would you mind taking a look at my settings export to see if anything stands out as an obvious mistake? (I removed the VIN number from this export but everything else is there.) The data was pulled from the Wikipedia link below.

Code: Select all

<?xml version="1.0" encoding="windows-1252"?>
<LapTimerVehicleDB>
	<name>Vehicles Database</name>
	<vehicles>
		<vehicledef index="1">
			<name>Honda S2000</name>
			<powerloss>0.180000</powerloss>
			<massfactor>1.100000</massfactor>
			<cW>0.280000</cW>
			<frontSurface>2.010000</frontSurface>
			<unladenWeight>1450</unladenWeight>
			<payload>120</payload>
			<maxTorqueRPM>6800</maxTorqueRPM>
			<maxTorque>220</maxTorque>
			<maxPowerRPM>7800</maxPowerRPM>
			<maxPower>177</maxPower>
			<vin></vin>
			<gears>
				<gear>1,3.130000</gear>
				<gear>2,2.040000</gear>
				<gear>3,1.480000</gear>
				<gear>4,1.160000</gear>
				<gear>5,0.940000</gear>
				<gear>6,0.760000</gear>
			</gears>
			<driveRatio>4.100000</driveRatio>
			<frontWheels>215 / 45 Z 17</frontWheels>
			<rearWheels>245 / 40 Z 17</rearWheels>
			<driveWheels>rear</driveWheels>
			<drivetrainInfoDefined>false</drivetrainInfoDefined>
			<bodyInfoDefined>false</bodyInfoDefined>
			<engineInfoDefined>true</engineInfoDefined>
			<powerTransmissionInfoDefined>true</powerTransmissionInfoDefined>
			<intakeType>Naturally Aspirated</intakeType>
			<engineType>Otto</engineType>
			<maxRPM>8000</maxRPM>
			<shiftGearThreshold>90%</shiftGearThreshold>
			<minRPM>1500</minRPM>
		</vehicledef>
	</vehicles>
</LapTimerVehicleDB>

http://en.wikipedia.org/wiki/Honda_S2000#References

- Rob

[Harry]

As written in the reference, the S2000 has a secondary gear reduction that needs to by multiplied to the final drive ratio. This ratio is 1.160 or 1.208 for your 2004 model (please check the codes in the wiki). As a sample using the 1.160, you need to enter a drive ratio of 1.160*4.1 = 4.756. The overall relation between engine rpm and axle rpm is:

Code: Select all

Spec:     axle rpm * (final drive ratio * secondary ratio) * gear ratio = engine rpm 
LapTimer: axle rpm * drive ratio * gear ratio = engine rpm

- Harry

[daphatty]

Excellent! I new I was missing something. That did the trick. Thank you for all of your assistance.

Would it be possible to add Final Drive Ratio * Secondary Ratio = Drive Ratio to the Drive Ratio Description within the app? I wasn't sure what needed to be done until I saw your equation. Listing the equation within the app might reduce the learning curve for some of us.

Thanks again! I'm off to the track this weekend and am looking forward to collecting my data.

[Harry]

The secondary ratio is common for motorbikes, but rare for cars. There is another special case: different drive ratio for certain gears. Adding all that stuff to LapTimer would make it pretty confusing for 90% of the users - which in turn is the reason I actually prefer helping here on the forum

- Harry

[ambordokan]

Harry, on this matter I think the motorcyclists among us lack support: my Ninja 300 has a primary ratio of 3.087 and a final ratio of 3.000 (stock, with original sprockets of 42 and 14). So, this means we should be able to insert a final drive of 9.261 and we are allowed to go just to 9.000.

Also, it would be really useful if we could, on a motorcycle setup, be able to change rear and front sprockets (a very commom setup at the track) and be able to emulate somehow what would we achieve in terms of final speed on each gear.

What do you say?

Cheers!

[Harry]

Please feel free to post the "sprocket change support" as a feature request (forum: viewforum.php?f=10). That makes sense from my point of view but certainly needs to get balanced against other requests

To work around the 3.087 x 3.000 > 9.000 issue, simply calculate the compete ratio for each gear and enter it into the gear ratios. Set the Drive Ratio to 1.0 in this case. As long as the product from both is correct, distribution to the two ratios is arbitrary. The only value used by LapTimer is the product from Drive and Gear ratio, the individual values are not used.

- Harry