Using aftermarket head with fuel injected gy6 possible?

[symcrox]

I'm wondering has anyone ever done this?

I have a Sym scooter which is fuel injected but still GY6 and the only major thing that's different from a standard carb'ed GY6 cylinder head is the fact it has a screw in temp sensor port at the top. I could buy one of those temp sensors that fits onto the cylinder head cover bolts (think rollingwrench used one like that in his DIY EFI kit), but I'm wondering whether this would be sufficient for the ECU?

Main reasons I'd want to do theoretically this is down to price and availability of the OEM cylinder head, it costs three times as much as any other high quality cylinder head and appears only available on order from Taiwan. Now if for any reason I had to replace it I could be waiting months for a repair, where as high quality non EFI CH's are available everywhere.

[GrumpyUnk]

To work properly and meet the designed and programmed operation the ECU will use, you would have to match the output of the original temperature sensor/sender. The replacement temp sensor would have to product comparable numbers in V or R to make the ECU happy, and to make it respond as designed in response to temperature sensed at the cylinder head. If you can match that, even with a clamp-on sender, it should work pretty well. The one thing that likely would not would be the change in temperature with the run time of the engine. If the sensor was fin mounted, it would respond differently to changes in engine rpm as the blower volume across the fin would change. If you compared readings to a sensor that was mounted in a drilled & tapped boss on the block of the cylinder head instead of fins, the temperature curve with rpm would likely differ in the short term, and long term also. A drilled port would not likely respond as well to changes in blower volume caused by changes in engine rpm. I guess you might say it is not a trivial change. FWIW, I think air cooled engine fins get hot a lot quicker and cool off a lot quicker than the actual thick metal portion of a cylinder head. I think the temperature of the thicker portions lags behind fin temperatures, in heating and in cooling. More mass...
tom

[Kaos]

Apr 21, 2023 11:40:00 GMT -5 symcrox said:

I'm wondering has anyone ever done this?

I have a Sym scooter which is fuel injected but still GY6 and the only major thing that's different from a standard carb'ed GY6 cylinder head is the fact it has a screw in temp sensor port at the top. I could buy one of those temp sensors that fits onto the cylinder head cover bolts (think rollingwrench used one like that in his DIY EFI kit), but I'm wondering whether this would be sufficient for the ECU?

Main reasons I'd want to do theoretically this is down to price and availability of the OEM cylinder head, it costs three times as much as any other high quality cylinder head and appears only available on order from Taiwan. Now if for any reason I had to replace it I could be waiting months for a repair, where as high quality non EFI CH's are available everywhere.

Yes it'll work as long as the temperature sensor resistance is the same as the stock one. The GY6 FI engines use an injector in the intake, so the heads don't have any differences from the carb'd ones.