K-Pro loses connection when Datalog Recording

[Hondata]

There are ground loops resulting from poor grounds or incorrect wiring. This is the norm, rather than the exception, for engine swaps. It can be fixed - I have fixed the same issue with a number of Elises and Exiges with these steps:

1. Check the spark plug type is correct. Don't take the owners word for it, pull the plugs, look up the part number and verify the plug is a resistor plug.

2. Refer to the engine swap wiring diagram here. Read the engine swap notes on the page. Note that you can't take any shortcuts - if it says that you need a main and fuel pump relay, it is for good reason.

3. Eliminate the lotus 'multi relay' box. Use a seperate relay for the main, fuel and oxygen sensor. Wire as per the diagram. Important points are use of switched vs unswitched power, and the correct wiring of the relays.

4. Remove the main chassis ground on the left side of the engine bay and clean off the anodizing to ensure a good ground. Run a ground wire from this point to the harness main ground (see below) and also to another point on the engine which has good contact with the head (I use one of the bosses on the end on the cylinder head near the ECT sensor).

5. Check that there is a decent sized ground strap running from near the start motor (transmission case bolt works) to the chassis ground. This can be the same ground point used as above.

6. Check the main harness ground (normally goes to the intake manifold) for any broken wires near the crimped end. Attach the harness ground to the cylinder head (again I like to use the unused boss on the end of the cylinder head). This ground strap and attachment is critically important.

7. Check the o2 sensor wiring. If there is any questionable wiring, disconnect it until a later stage.

8. Check inside the ECU that the USB connector is insulated from the ECU lib. While you have it open, check the daughter board retaining screw(s) are not loose, but do not over-tighten. Note that the ECU case does not need to be grounded, and if in doubt, do not ground the case.

9. Connect everything together and ensure you have at least 12.5V battery voltage. When you start the car later make sure the battery voltage as measured at the ECU does not fall below about 10.0V - typcially you just need to run a battery booster until the car is sorted and running.

10. With a multimeter, attack one lead with a wire to the negative battery terminal. With the other lead, test all ground points, the ECU case and the USB connector for voltage difference. You should not see more than about about 4 mV voltage difference. If not, check grounds once again.

11. Now measure current flow between the battery terminal and ground points (plus ECU case and USB connector). You should not see more than about 4 mA.

12. Repeat 10 and 11 with the engine running. If the grounds are good you should see <1mV voltage and <1mA current. Note that this is where the lotus multi relay box tends to let you down.

13. If you don't have ferrite cores on the USB cable then add some. You can't have too many, but remember that these only help the symptons on the real problem - which is current loops in the vehicle wiring from bad grounds / relays.

I've left out some points I'm sure - if any wiring looks suspect, then it probably is. Also you can check that the laptop is not creating a voltage difference / current flow at the laptop USB connector when connected to the vehicle for charging. The only known laptop problem is that Dells have a particularly poor USB port which gives a higher incidence of problems than other brands.

If I ask one thing it is that you follow all the above instructions fully before defaming Hondata again.

[moses187]

i have greddy kit,650 injectors,greddy plugs,ive tried usb cable with and w/o ferrites.records fine until i hit boost.this com is a newer dell also.i have placed the ground on the valve cover as instructed.i also have a grounding kit on the car which terminates in 6 different places.

[Razathorn]

i have greddy kit,650 injectors,greddy plugs,ive tried usb cable with and w/o ferrites.records fine until i hit boost.this com is a newer dell also.i have placed the ground on the valve cover as instructed.i also have a grounding kit on the car which terminates in 6 different places.

I've found that using a car 12v laptop charger to keep a common ground to the car/ecu does wonders. I will randomly get disconnects without it.

Wayne