Sounds like a simpler way of doing it Bob - I will investigate. I was ill this weekend so didn't get a change to implement my diodes idea anyway. I'll let you know how it goes. Thanks, RogerSanta wrote:Extra idle can also be gained for extra load if I rember rightly by changing the wiring over to the automatic setup
Need to know what's broken and maybe how to fix it ? Post here
I looked at using the aircon switch, but it seemed a bit complicated, and then I had an inspiration: All I needed was one wire, no diodes, nothing flash, just one wire...
Before describing the solution, I will just reprise the standard setup: The four diodes in the classic "four diodes and a zener" circuit are to prevent voltages feeding back between coils, nothing else - and the zener is a belt and braces idea that in theory is not necessary if you feed the flyback voltages down the original wire from the coil to the 14CUX, since this wire has a high resistance built into it.
So - my simple idea was to take a lead from just one of the coil feed wires - the ones that have the voltage spikes, and feed that direct into the 14CUX. This way the ECU will see only one in four ignition events and will 'think' that the revs are only 1/4 of actual, and so will open the air bypass valve to increase the idle speed. There is no need for a diode since there is only one coil connected, and the zener was never actually needed anyway.
So - did it work I hear you say... Of course it worked and here is a rather crappy video showing it.
What I don't understand though is why it ticks over at 1500rpm... I would have expected it to run at four times the target idle speed (750rpm) and instead it's only running at twice that figure. Strange....
The aircon switch is a none starter anyway, you're after sustained high tickover not a 1 second pulse, which is all the aircon/drive wire gives you when it changes state.
I wonder if the 1500 RPM limit is caused because you don't have enough pulses ? If you're tickover is at 750 then the ECU will think it's getting less than 200 RPM and move the IAC to it's cranking position. ISTR the normal cranking rate for the engine is around 140 RPM and it wouldn't expect the RPM to drop below around 600 in normal operation. My guess is that it's gone into some sort of "safe" get you home mode on the IAC due to an apparently out of range input. Probably moving the IAC to a predetermined safe position.
Does the closed loop idle control still work ?
Further experimentation (all done purely on LPG) as suggested, has revealed some interesting points..
1. Removed the stepper lead when engine is off and then started up with normal connection on the flyback lead causes it to idle at about 3200 rpm. This is due to the ECU winding the stepper motor right out when the ignition is turned off (normal operation), but shows what 'right out' will do.
2. Reconnected the stepper and then tried the '1/4' connection again and as before it idled at 1500rpm (actually there is a slight creep to about 1800rpm as the vapouriser etc warm up).
3. Tried the closed loop experiment with the 1/4 lead in place (braked down to about actual 800rpm) and it appeared to work in that dipping the clutch resulted in revs rising to about 3200 (sound familiar?), but then the revs didn't fall again - just stayed at 3200. i.e. Closed loop now inoperable?
4. Turned ignition off and then tried again but idle was still 3200rpm.
5. Returned to normal wiring and idle was normal 750rpm, but when returned to '1/4' wiring idle was up at 3200rpm again.
6. Disconnected the battery to reset any fault-codes and tried again - idle was once again 1500rpm with the '1/4' lead in place.
Conclusion? Hmm... Not too sure. It does what I want, but it looks to me like it is only just 'getting away with it' and that if I load the engine enough to slow the idle speed, it will then generate a fault condition (it will think that the engine is misfiring, presumably) which will require re-setting. Since I have QR battery connectors and a cheap radio, resetting a fault condition is no problem but is obviously something I would like to avoid.
With regard to why it's running at 1500-1800rpm, it does sound likely that the air bypass valve is set to some sort of intermediate 'cranking' position.
Anyway - for now I think that I will put a relay in the signal lead so that either normal or '1/4' signals can be selected, and take the power for the air system from the same switch when I get a round tuit.
Sorry if this is boring to most people, but I love messing around like this and trying to work things out - I always have...
May I ask which a/c compressor you are using?
I've just setup the on-board air on my 110 with the Denso 10PA compressor with ND-8 compressor oil (as recommended by Denso), and it appears that quite a bit of oil has been collected at the filter even after just a short trial at less than a minute. I could empty the filter after each event of course, but wondering if this is normal. A few articles I read where people run Sanden compressor with grease seems fine without collecting any oil/grease residuals. So am thinking if I should be using thicker oil instead?????
Sorry for hi-jacking your thread...
The compressor I have is the standard Denso one for a 95 v8 and - although my plan is to lube it with grease like it says in one or two postings in a well known other place, I haven't yet done so. In fact I don't recall there being a plug anyway...
So my alternatives are:
No worries about the tread Mr L, your comments are always welcome and anyway, I think it's about run it's course...
Roger........DO NOT pack up grease in the swash plate area of a Denso compressor. I DID and the grease blocked the pressure relief valve, causing back pressure and burst the pipe.
From the compressor output, the pipe connects to a pressure relief valve, then to the filter and snap coupling. The pipe burst today after the trial event, as I was getting to pump up the tyres. Took the valve apart when I got home, and found grease all over it's internals. I could have had the filter before the valve, but would think it will block up the filter in no time too.
So, the compressor is coming out to have a proper bath to clean out the grease.
Thanks for the warning!
What's the plan now then?
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