Tuning the RX4's Fuel Injection

[Lukas]

Originally Posted by Bob Kelly

But the problem is that the bike Runs too lean from the get go !!! it could handle more fuel throughout the entire band ! .... the question is how much resistance is needed and where do I put it ? LOL I'm willing to add a resister in line to richen up my bike I don't think a bike should have a white plug in it...but that is how they are set up... !
.....
Bob.....

These bikes do not have catalytic converter but catalytic converter mesh in the muffler which is an ordinary straight pipe and the mixture on the lower parts is set to very poor to make the exhaust as clean as possible which results in lack of power in the lower parts of the rpm my RX3 had power only from 6000k rpm now after map tuning by Italians the power is from 3000k rpm. At the beginning, it is quite a strange experience for someone who is used to riding this motorcycle, so the map must be tuned, i.e. injection time, fuel quantity and ignition timing, that all sensors make corrections to the amount of mixture and ignition timing in relation to the basic map and work together which means that a change in the signal of one sensor can cause something in the form of misinformation for the ecu which may result in a check engine light up.

[JFOlivier]

Does anybody know what the EFI sensors do, the input air temperature does it increase or decrease fuel with a rising temperature. What about the input air pressure is this just an advance signal to the EFI as to how much fuel to add with an opening throttle position sensor? and then what does the cylinder temperature sensor do, my thought maybe the sensor that closes the loop when the engine reaches operating temperature which then leaves the O2 sensor in control of the fuel levels. Anyone care to help here.

[pyoungbl]

You might find this interesting...from Zongshen....

Sadly, does not really answer your questions about how the sensors interact with the ECU. My experience is with Ducati and Moto Guzzi ECUs. There the temp sensor adds fuel while the engine is cold...much like the choke with a carb. The air pressure sensor will adjust according to air pressure...that is altitude. Engine temp...probably another fuel adjustment. The thing is, each of these sensors act in concert with each other. It's not a simple additive process. You might see the air temp sensor telling the ECU to increase fuel while the air pressure sensor is saying to decrease, and so on. That's why making a new map is so difficult.

[Boatguy]

Originally Posted by pyoungbl

You might find this interesting...from Zongshen....

Ah! A new weapon for the EFI/carb wars! Lolol.

[wheelbender6]

“Adjusting the resistance leaves one with the same problem as before, the ECU will respond with more fuel across the entire rpm range. A good ECU map will try to maintain the mixture at a steady state but, in reality, many maps go from lean to rich and back to lean. This means that your 'fooler' might take care of a lean condition on parts of the map but a super rich condition elsewhere.“

Hmmm. Sounds just like many of my carb jetting experiences.

[wheelbender6]

The reason I am horning in on your thread is because I may buy a Genuine G400C, and it has Delphi EFI.
I’d like to own an RX4, but the seat height concerns me since I have only a 29” inseam. I ride in a lot of stop and go traffic and tall seats make that more difficult.

[Bob Kelly]

Originally Posted by wheelbender6

The reason I am horning in on your thread is because I may buy a Genuine G400C, and it has Delphi EFI.
I’d like to own an RX4, but the seat height concerns me since I have only a 29” inseam. I ride in a lot of stop and go traffic and tall seats make that more difficult.

I own a 2021 RX4 and I lowered it 2" front and rear super easily
1.) i took out all the pre load and ran the nuts up to the top of the shock in the rear and locked them there... that dropped the rear almost exactly 2" (EDIT# I discovered that this is not the thing to do as it bottoms out the rear shock. I made a longer lower link instead to get it 2.5" lower)
2.) I loosened up the pinch bolts and raised the fork tubes in the triple trees up 2" and that lowered the front.... However to do that I had to buy some handle bar risers to fit the handle bars and move the handle bars back away from the fork tubes.... i got the 2" riser type that pivot in the original handle bar clamps
it worked real good I have a 30" inseam and can flat foot both feet at a stop.
.....
Bob.....

[wheelbender6]

Great bedtime story.

[pyoungbl]

The Delphi ECU is used on many small engines. They probably have similar (if not identical) sensors but the actual map is going to be modified to work with the specific engine model, exhaust and intake setup. As a purely academic exercise I'd like to know how the various sensors feed into the base map and how they interact. Check the throttle body size for that Genuine 400. On the RX4 it's a 45mm TB.

[JFOlivier]

If you take a look at the IAP sensor on the x-pect it is between the throttle valve and the intake manifold so how does that give you the atmospheric pressure when it is working from almost a vacuum to near atmospheric pressure depending on the throttle position and the engine load. I sort of felt that that pressure sensor was sort of an advance warning to the EFI system as to where the RPM's were in relation to the throttle valve so as to supply more or less fuel. With RPM's rising on a flat road throttle valve will be closing and pressure in the inlet manifold will be dropping into more of a vacuum where Rpm's dropping on a hill with the throttle valve opening would be increasing the pressure to the IAP. So does this sensor really do anything about altitude or is altitude just handled by the O2 sensor in a closed loop.

[pyoungbl]

x-pect?

[wheelbender6]

The G400c makes a little over half of the hp of the Rx4, so it will have a much smaller throttle body. The rest of the EFI components should be very similar.

[wheelbender6]

Thanks Bob Kelly. RX4 is back in the running for me.

[JFOlivier]

When I get some time I will take a look at my air temp sensor and try to measure its resistance. Then raise the temperature and see if the resistance increases or decreases which will give me some idea where to aim for. Right now spring in the bee yard is keeping me a little busy. I would guess that the colder the air temperature the more fuel added.

[JFOlivier]

I removed and tested the Intake Air Temperature sensor and checked its resistance and at around 70 degrees F it read 1.8K ohms and at about 35 to 40 degrees F about 2.2K ohms.
So this thermistor has a negative coefficient and the higher the temperature goes the lower the resistance so to lower the temperature reading you will need to add some resistance in series with the thermistor. I would try no more than 100 ohms at a time or if you can find a 200 or 300 ohm potentiometer you could work from zero increase up to 300 ohms increase in steps. Measuring any changes is the challenge, however I just filled my tank with mid grade gas and feel there is a difference in power and acceleration on my Lifan e-pect so maybe the RX guys will be able to feel a difference. Looking at setting up ECU hacker I need to find some of those flat pins they use in the China Bike plugs so that I can make up a plug to fit the ECU port, any idea where I could find those.