Cold idle air valve
Discussion
I have an Emerald ECU fitted to my car and tuned by Joolz. At the time Joolz set up the ECU I had no idle air valve fitted. I am now attempting to fit an idle air valve to be controlled by the Emerald. I have removed the extra air valve that was fitted to the flapper system and made a bracket to fit the two wire air valve in it's place. My plan is to use the old pipework for the extra air valve to take the air from the throttle plate area and feed it through the valve to the plenum where the extra air valve used to feed it, if I understand how the original system worked. Here are two pictures of the installation so far. Can anyone confirm that I've understood how the system works and is there an easier way to fit a two wire valve than the one I've tried. The pipe work is a bit convoluted from the valve to the plenum. TIA.
Your thinking is correct. This is mine:
My valve is hanging free on an extremely short stepped diameter silicon hose on the side of the plenum; and then a long 90 Deg reducing hose wrapping around the plenum to the original auxiliary air rail. It's been on there for a couple of years with no issues.
The valve itself works very well too, it's used for closed loop idle control as well as cold start. It's also used for dashpot control; ie when the throttle is slammed shut by the driver it opens and brings the engine speed down in a controlled manner, helping to avoid stalling at junctions and giving smoother gearchanges. It's all calibratable with megasquirt so you can make it do whatever you want, I'm not sure about Emerald.
My valve is hanging free on an extremely short stepped diameter silicon hose on the side of the plenum; and then a long 90 Deg reducing hose wrapping around the plenum to the original auxiliary air rail. It's been on there for a couple of years with no issues.
The valve itself works very well too, it's used for closed loop idle control as well as cold start. It's also used for dashpot control; ie when the throttle is slammed shut by the driver it opens and brings the engine speed down in a controlled manner, helping to avoid stalling at junctions and giving smoother gearchanges. It's all calibratable with megasquirt so you can make it do whatever you want, I'm not sure about Emerald.
Hi Martin, could you tell me what PWM value and update rate you are using for your valve. Emerald suggest 300Hz and 10 msecs but that's for any 2 wire valve. I'm wondering if this is the wrong value for this type of valve as I am having difficulty getting the valve to work properly. I find that if I open the valve to a value, for instance 50 from a value of 30 it opens the valve a different amount compared to moving the valve to 50 from a value of 70. I thought possibly the valve was sticking but I have a new valve and a used valve and they both exhibit the same behaviour. I'm wondering if a different PMW value and update rate might help.
Hi Leslie,
Sorry for the slow reply; I use an ancient laptop for my engine tuning and I didn't have it at my house.
I'm running at 217 Hz, although it doesn't make too much difference other than you might hear a more pronounced buzz at lower frequencies. My update rate is the general processor rate which I think on MS2 is of the order of 1ms, although I'd have to check to be sure.
The valves are not linear, mine is fully closed at 34.9% PWM and fully open at 70.2% (or at least open enough such that the idle speed no longer increases with values above that). It's a Volvo/Bosch 2 wire valve. The odd numbers are down to binary to decimal conversions. If I go below 34.9% the valve opens again; this is to allow cold starting with a high idle if the valve fails.
I originally set my valve up for warm up only so I specified a valve position depending on coolant temperature. It's now in closed loop idle speed control so I specify an idle speed vs engine temperature; I have it set to 950rpm when hot as I have a fast road cam.
Martin
Sorry for the slow reply; I use an ancient laptop for my engine tuning and I didn't have it at my house.
I'm running at 217 Hz, although it doesn't make too much difference other than you might hear a more pronounced buzz at lower frequencies. My update rate is the general processor rate which I think on MS2 is of the order of 1ms, although I'd have to check to be sure.
The valves are not linear, mine is fully closed at 34.9% PWM and fully open at 70.2% (or at least open enough such that the idle speed no longer increases with values above that). It's a Volvo/Bosch 2 wire valve. The odd numbers are down to binary to decimal conversions. If I go below 34.9% the valve opens again; this is to allow cold starting with a high idle if the valve fails.
I originally set my valve up for warm up only so I specified a valve position depending on coolant temperature. It's now in closed loop idle speed control so I specify an idle speed vs engine temperature; I have it set to 950rpm when hot as I have a fast road cam.
Martin
Hi Martin,
Thanks for the reply. I have got the valve working correctly by changing the frequency to 100Hz. But I still have a problem. With the valve fully closed (at 34% on my valve) there is so much air leaking past the valve that even with the idle speed screw on the plenum fully shut I can't get the idle down to where it should be when the engine is hot. I am using a Bosch valve at the moment so I think I need to try a different type of valve.
Thanks for the reply. I have got the valve working correctly by changing the frequency to 100Hz. But I still have a problem. With the valve fully closed (at 34% on my valve) there is so much air leaking past the valve that even with the idle speed screw on the plenum fully shut I can't get the idle down to where it should be when the engine is hot. I am using a Bosch valve at the moment so I think I need to try a different type of valve.
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