ChinaRiders Forums - View Single Post

franque · 02-22-2021, 05:21 AM

@ricsha91 I've left you a reply at the bottom, just trying to correct a couple of things for some misinformed posting below

@wheelbender6 at least with the smaller stuff, one doesn't install nozzles, the whole injector is replaced.

@Billy Hilly Did you read OP's post? They had poor results! Your speculation on how fuel injection works, or should work, is disconnected from reality. In particular, this is something that is, if I remember correctly, 50 state street legal and CARB approved. I'll unpack this below. Remember, try to make what you post fact based, and not based on your opinion of how EFI might work.

- Firstly, with regards to what you said about the computer: to attain EPA/CARB approval, ECUs are quite locked down, and they are forced to stay within certain parameters. That is why, for example, a Harley that gets a different air cleaner and pipes requires a tuner so that it can run properly, and not excessively lean (OP, sound familiar?). There have been a couple of injected bikes on the market with user adjustable ECMs, but I don't think there has been anything sold in the last 10 years like that. It was a loophole that was closed.

- Secondly, the injector. Many injectors are specc'd for their specific application (though in this case, my educated guess is that they used something that was close, I doubt they received a custom injector) and there is not much room for increased fuel flow or power. Many "stage 1" tunes for cars are based on not exceeding the duty cycle of the injector, so that the car can run reliably without having to change much in the way of components. Exceeding a "stage 1" tune usually requires swapping injectors, etc. to deal with increased duty cycle on the OE injectors.

Without looking at the maps on this ECM, we cannot know the injector duty cycle, so it is foolish to say that the injector can "spray more fuel than you would ever need". That is merely a guess, and based on the wool between your ears.

- Fuel supply system - we have no idea if, or how much excess capacity the fuel pump has for this application, it could be that this system is based on European market 125s, where fuel injection is now required for emissions standards. If that is the case, which my educated guess is that Lifan didn't custom spec something for their 200cc bike, then there probably isn't much headroom for that, which I admit is (educated) speculation.

What you're describing in terms of EFI is kind of, almost, how a wide band O2 EFI system works, but only if there were no emissions regulations so that the ECM was free to make whatever power it liked, though there are still a lot of things to consider. Is the O2 sensor actually wide band? My guess, again educated, is that they're using narrow band O2 (nbO2) sensors, because they're cheaper, most name brand motorcycle manufacturers aren't using wide band O2 (wbO2) sensors because of cost. Additionally, in the locked-down state that this ECM has, there is no sense in putting an expensive sensor in it from the OE's perspective.

Why is wbO2 vs nbO2 important? A wbO2 can measure between 12-22:1 AFR, while an nbO2 can only measure 14-15:1. If the increased airflow is causing it to go leaner than 15:1, when it was almost definitely designed to run at 14.7:1, aka stoichiometric, there is not too much headroom for the O2 sensor to add fuel to get it back to 14.7, especially since anything richer than 14:1 is outside of the capacity of an nbO2 sensor to read, so they target 14.7:1, which is the ideal air-fuel ratio for emissions in a spark ignition gasoline engine.

Is it a MAP or a MAF sensor? That can change certain parameters. Additionally, there are tricks to get more fuel into the engine by spoofing the temperature sensor. Is it alpha-N, where you only have a TPS and engine rpm controlling fueling?

------
------

My educated guess is that it is a cheap Delphi open loop nbO2 EFI system that will require either another ECM for more independent control of the EFI, or potentially a tuner for another Delphi application could be used to adjust some parameters. Realistically, without a wbO2 system, there won't be a lot of capacity for increased power, partially because peak afr for a gasoline engine is around 12.5:1.

Sorry if I was a bit long-winded, I could explain more, but I hope that this will suffice at this time.

02-22-2021, 05:21 AM	#4
franque Join Date: Nov 2017 Location: Marseille, France -> Conakry, Guinea Posts: 1,481	@ricsha91 I've left you a reply at the bottom, just trying to correct a couple of things for some misinformed posting below @wheelbender6 at least with the smaller stuff, one doesn't install nozzles, the whole injector is replaced. @Billy Hilly Did you read OP's post? They had poor results! Your speculation on how fuel injection works, or should work, is disconnected from reality. In particular, this is something that is, if I remember correctly, 50 state street legal and CARB approved. I'll unpack this below. Remember, try to make what you post fact based, and not based on your opinion of how EFI might work. - Firstly, with regards to what you said about the computer: to attain EPA/CARB approval, ECUs are quite locked down, and they are forced to stay within certain parameters. That is why, for example, a Harley that gets a different air cleaner and pipes requires a tuner so that it can run properly, and not excessively lean (OP, sound familiar?). There have been a couple of injected bikes on the market with user adjustable ECMs, but I don't think there has been anything sold in the last 10 years like that. It was a loophole that was closed. - Secondly, the injector. Many injectors are specc'd for their specific application (though in this case, my educated guess is that they used something that was close, I doubt they received a custom injector) and there is not much room for increased fuel flow or power. Many "stage 1" tunes for cars are based on not exceeding the duty cycle of the injector, so that the car can run reliably without having to change much in the way of components. Exceeding a "stage 1" tune usually requires swapping injectors, etc. to deal with increased duty cycle on the OE injectors. Without looking at the maps on this ECM, we cannot know the injector duty cycle, so it is foolish to say that the injector can "spray more fuel than you would ever need". That is merely a guess, and based on the wool between your ears. - Fuel supply system - we have no idea if, or how much excess capacity the fuel pump has for this application, it could be that this system is based on European market 125s, where fuel injection is now required for emissions standards. If that is the case, which my educated guess is that Lifan didn't custom spec something for their 200cc bike, then there probably isn't much headroom for that, which I admit is (educated) speculation. What you're describing in terms of EFI is kind of, almost, how a wide band O2 EFI system works, but only if there were no emissions regulations so that the ECM was free to make whatever power it liked, though there are still a lot of things to consider. Is the O2 sensor actually wide band? My guess, again educated, is that they're using narrow band O2 (nbO2) sensors, because they're cheaper, most name brand motorcycle manufacturers aren't using wide band O2 (wbO2) sensors because of cost. Additionally, in the locked-down state that this ECM has, there is no sense in putting an expensive sensor in it from the OE's perspective. Why is wbO2 vs nbO2 important? A wbO2 can measure between 12-22:1 AFR, while an nbO2 can only measure 14-15:1. If the increased airflow is causing it to go leaner than 15:1, when it was almost definitely designed to run at 14.7:1, aka stoichiometric, there is not too much headroom for the O2 sensor to add fuel to get it back to 14.7, especially since anything richer than 14:1 is outside of the capacity of an nbO2 sensor to read, so they target 14.7:1, which is the ideal air-fuel ratio for emissions in a spark ignition gasoline engine. Is it a MAP or a MAF sensor? That can change certain parameters. Additionally, there are tricks to get more fuel into the engine by spoofing the temperature sensor. Is it alpha-N, where you only have a TPS and engine rpm controlling fueling? ------ ------ My educated guess is that it is a cheap Delphi open loop nbO2 EFI system that will require either another ECM for more independent control of the EFI, or potentially a tuner for another Delphi application could be used to adjust some parameters. Realistically, without a wbO2 system, there won't be a lot of capacity for increased power, partially because peak afr for a gasoline engine is around 12.5:1. Sorry if I was a bit long-winded, I could explain more, but I hope that this will suffice at this time.
	3