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Originally Posted by UniqueMods You mentioned above that you are well versed with tuning a open loop cng system, so i got a few questions for you and other who know hw to tune a open loop cng system...
1. My car is original tuned and been running on the stock filter for 2500km. (open loop + advancer on a santro)
I tried fitting my old k&n conical filter back to the car. once the car was warmed, the car revved OK, but would not idle. it just died. refitted the stock filter and its idling fine.
I assume the extra air allowed by the k&n is messing up the AFR on idle.
How can i re-tune this myself to work with the K&n. I wish to see the effect of the k&n on power delivery and FE. And the installer is a bit too far away for this DIY.
Mine being a open loop system has a screw type nut instead of the stepper motor. Pic attached.
Any suggesting on the tuning process - increase gas flow by turning the flow screw nut, clockwise or anticlockwise, OR is there another method.
any other steps i need to follow to get the idling correct with the k&n.
My biggest concern is that this DIY should be completely revers-able, in case the effect of the k&n is not to my liking.
UM |
Like you have correctly mentioned, the mixture has become lean with the K&N allowing more air and less CNG. Plus the fact that winter has set in also compounds the problem.
Don't worry about having to reverse or undo anything. There is absolutely no harm which can be done by tuning your car. If you are used to adjust older carburetor equipped vehicles, this process should be easier.
Here's how you tune the engine.
1. Let the car warm up. The car should be nice and warm. At least a 15 minute run is recommended before trying to set this. Maybe you can do the tuning after you come back from an errand
2. Now mark the position where the screw is currently on the area where you have labelled as manual power valve. Use a marker, nail polish or any other thing with which you can get the position. This is important so that you can reverse the settings if you are not happy.
3. Rev the engine to around 2500 rpm or so by pulling on the throttle body and hold it in a constant position. Then begin to move the screw anticlockwise. This is just like opening or closing a tap. Mixture becomes richer when you open it and leaner when you close it.
4. The revs shall automatically rise further from where you are holding it. At the best mixture, it shall be the highest. If you make it more rich, it shall then drop. Do this till you arrive at the highest rpm. You can go by your ear if you don't have a tachometer.After you arrive at the best tuning, leave the throttle body and let the rpm drop to idling.
5. Once this is done, then the main adjustment has been set. Now you can proceed to adjust the idling.
6. The idling adjustment is on the reducer itself. It is another small screw. You should find it easily. Else post a pic and I'll help you.
7. Follow the same process. Open the screw (move it anticlockwise) to make it richer and the other way around to make it lean. If you have done it wrong, the car shall vibrate higher or switch off like in your case.
8. After both have been set, take your car for a test drive. If you find it getting choked (dying) when the rpm is low / moderate and you suddenly open the throttle, then the mixture is slightly rich. Minutely adjust the main valve by rotating it clockwise, but not more than 1/8th of a turn at a time. This road test type adjustment is necessary since when you adjust with step 4 above, there is very little load on the car. When you actually drive it, the car may perform marginally differently and you may get a slightly better tuning. At least this is my experience.
9. If you have to press the throttle hard to get power, then obviously the mixture is lean. Make it richer.
10. Once this is done, relax and take off on a nice drive with your spouse and be happy that you tuned your CNG car yourself
Don't worry about reversing anything. It can be easily done. There is no way you can harm your engine in any way. Take courage in the fact that if simple roadside mechanics who barely understand physics can tune your CNG car, you can do better with knowledge, love of your car and a more detailed understanding on how your car performs.