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tuning impco system 

 

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 Post subject: tuning impco system
Posted: Sun Apr 08, 2007 6:32 pm 
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can anyone make sense of this system..

the car is an EF wagon has the following :

impco model L converrtor
impco 200 mixer
impco commander fuel controller
efi start controller


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in the first pic that black thin tube is plugged and goes nowhere it should go to a little solenoid thingy like on my other car

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I want to hook this tube up so it runs in closed loop properly...but as you can see in pic 4 the wires have nowhere to go...
whats the procedure for tuning these things?

id have to richen it up first wouldnt I, as the controller can only lean out not rich up?

strange thing is that this car runs well on lpg and returns good economy

also whats the start controller doing there? what happens if I get rid of it?

 

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Last edited by gogetta on Mon Apr 09, 2007 12:02 am, edited 1 time in total.

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 Post subject: Re: tuning impco system
Posted: Sun Apr 08, 2007 8:09 pm 
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gogetta wrote:
in the first pic that black thin tube is plugged and goes nowhere it should go to a little solenoid thingy like on my other car
It should go to your FCV (flow control valve), which controls mixture - makes a ticking noise, a hose from the lower engine side of the converter hooks up to it as well. Also has two wires (maybe purple and yellow - check the impco commander pic, and what you've circled). There was a thread with pics on the FCV, asking what it was, can't find it unfortunately.

gogetta wrote:
also whats the start controller doing there? what happens if I get rid of it?
Leave it, it's for petrol start.
Tuning is done via the two mixture controls on the mixer in the first pic lower right - idle (spring loaded screw) and the other (part/full throttle). AFAIK, you need a testbox to hook up to the two FCV wires, as well.

There should also be somewhere a little black box with wires going to it - safety cutout for the lock offs, has tacho signal going to it, etc.

 

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Posted: Sun Apr 08, 2007 11:49 pm 
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You also have to ask yourself why it was plugged in the first place. Usually its because the FCV gets worn out from continually bashing its valve seat, and fails to correctly control the mixture. If the commander controller is faulty, or the EGO sensor isn't working properly, this may have been why it was changed back to open loop, and it might not work properly any more if converted back.

Also, that particular mixer (looks the same as mine) can run at least two different kinds of air valve/diaphragm. One will give great computer control with the FCV in closed loop, but apparently runs horrible (or not at all) if used in open loop. The other diaphragm is designed for open loop, but will still work ok in closed loop with the FCV - but with less range in fuel control. The difference is in the shape of the metal cone-shaped valve in the middle of the diaphragm.

If you have the non-FCV air valve, tuning of the mixer will need to be more precise or you may suffer problems with economy or backfires when you convert it back to closed loop.

Assuming the controller is working ok, you should expect to see a duty cycle on the FCV of ideally 50% on a capable multimeter. If it sits at, say, 95% and doesn't move, its seeing a continually rich mixture and has run out of ON time to make it leaner with the vacuum from the mixer tube. The opposite applies if it stays at 10% or so, and you'll need to richen it up.

 

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Posted: Mon Apr 09, 2007 12:10 am 
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well this is how the car has been since i bought it....
it runs well on lpg and i really should just leave it...you know if its not broke dont fix it

the mixer is probably the one that came with it originally so its probably the open loop one your refering to, but it runs fine the way it is (closed loop)

EBGIZMO - where can i find more info about this stuff? is there a book or something?

 

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Posted: Mon Apr 09, 2007 12:23 am 
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I only know of this from many long conversations with a guy I used to know who was an Impco Rep. He also supplied me with my parts at a great price :D

If it runs fine, and you're happy with the economy and performance, it might be better to leave it as is. The dept of transport might have something to say about it, but as long as you don't end up going for an inspection, you should be ok.

 

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EB II Sedan <--- R.I.P. (Rest in pieces - gone to the wreckers for $50...... bargain!)

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Posted: Mon Apr 09, 2007 12:39 am 
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ok so your the impco brain round here then...

does the impco controller have any sort of memory or does it just keep constantly reading 02 and adjusting the fcv?

what sort of imputs does it use? just o2?

 

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Posted: Mon Apr 09, 2007 12:41 am 
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so to tune it i need to hook up a duty cycle meter to the fcv and then adjust the 2 screws on the mixer till the fcv reaches about 50%

 

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Posted: Mon Apr 09, 2007 12:50 am 
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I wouldn't go that far ;-)

I have a different computer - its a CDP Oz, also made by Impco. It has a tacho input as well as the O2. As far as I know, it doesn't have any sort of memory - it only adjusts the fuel metering until it sees stoic at the O2 sensor.

It may have some advanced features that are enacted when it sees the tacho signal changing - I don't know :)

If the tacho input is missing, it stops pulsing the FCV.

This tuning method works for my CDP Oz, and if the commander works like snap0964 said, it sounds exactly the same.

 

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LSD High, 3.23, Black wheels, other shiny bits.

EB II Sedan <--- R.I.P. (Rest in pieces - gone to the wreckers for $50...... bargain!)

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Posted: Mon Apr 09, 2007 12:57 am 
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EBGizmo wrote:
This tuning method works for my CDP Oz, and if the commander works like snap0964 said, it sounds exactly the same.


could u explain the tuning method for me again, im not sure i understood what snap0964 was saying.....cant see why it would need a "special" plug in tuning device....

 

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Posted: Mon Apr 09, 2007 1:06 am 
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Because of how the CDP Oz works (by pulsing the FCV), you can use a multimeter to read the duty cycle of the FCV, and see if it has enough contol over the vacuum to the converter.

Impco also make a tuner which does the same thing, but it probably displays it as a rich/lean/correct readout. I've never used or seen one, but they do exist.

The tuner would be easier to use, as it would be designed for the particular unit. Also, not all multimeters are capable of measuring duty cycle, or don't update the result fast enough.

Snap0964 is probably more in-the-know for tuning specifics. The screw with the spring controls your mixture, but it works in reverse to a petrol carby screw. It controls how much air is allowed to bypass the diaghragm (rather than controlling fuel allowed in). Therefore, screwing it in (clockwise) makes the mixture go richer as less air is allowed to get into the throttle body. Anti-clockwise makes the mixture leaner.

 

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LSD High, 3.23, Black wheels, other shiny bits.

EB II Sedan <--- R.I.P. (Rest in pieces - gone to the wreckers for $50...... bargain!)

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Posted: Mon Apr 09, 2007 1:13 am 
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so basically these systems when runnning right are in constant closed loop from idle to full throttle?

 

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Posted: Mon Apr 09, 2007 1:25 am 
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By default, I think so. My setup is different, however. The dump valve in my setup wasn't reacting well enough, and the CDP Oz didn't control the mixture fast enough when I floored it at the lights, or under rapid acceleration. The result was that my engine would hesitate like it had no power for half a second, then take off - not good when you're trying to slip in at an intersection!

I made a work-around for this using a tacho switch kit from Jaycar. My car now runs a little rich in open loop mode from 0 to 50km/h (FCV is disconnected), and after 50km/h the FCV is reconnected and the computer runs in closed loop. It remains in closed loop until the speed is reduced to 40km/h or less, then goes back to open loop. The 10Km/h hysteresis is necessary to stop the FCV and computer from going haywire if I was to hover at the changeover speed for too long.

Doing it this way also prevents higher vacuum from being exposed to the converter during quick throttle actions below 50km/h.

I'm also going to put a switch on the gear selector that puts it into open loop whenever its in 1st/2nd/3rd. That way, you can knock it back immediately when you need power quickly, and not have to worry about switching over any home made economy switch.

 

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LSD High, 3.23, Black wheels, other shiny bits.

EB II Sedan <--- R.I.P. (Rest in pieces - gone to the wreckers for $50...... bargain!)

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Posted: Mon Apr 09, 2007 1:27 am 
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gogetta wrote:
im not sure i understood what snap0964 was saying.....cant see why it would need a "special" plug in tuning device....
More than likely you can use a meter as described - my LPG mechanic had a special testbox.
EBGizmo wrote:
This tuning method works for my CDP Oz, and if the commander works like snap0964 said, it sounds exactly the same.
The CDP Oz will have a separate plug near the unit itself, don't know what it does - as your normal tune goes off the 2 FCV wires.
Actually the wire colours for the gas commander are the same as the CDP Oz - wouldn't surprise me if they are identical in connection.
It certainly looks like it's been modded to run open loop - that green wire in the engine bay may possibly be the O2 sensor line that goes back to the gas commander.
Since a changeover relay would've swapped the O2 sensor between gas and petrol, I wonder whether the O2 sensor is hooked up to the ECU??

How's your petrol operation ??

 

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Posted: Mon Apr 09, 2007 1:43 am 
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EBGizmo - whats the dump valve? wheres it attach?
can it be seen in any of my pics?

snap0964 - the car has a fair bit more power on petrol and economy isnt too bad...also do you have a diagram for the commander and CDP Oz?

 

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Posted: Mon Apr 09, 2007 1:55 am 
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gogetta wrote:
snap0964 - the car has a fair bit more power on petrol and economy isnt too bad...also do you have a diagram for the commander and CDP Oz?
I did have, but I think I've lost it - I did my own install on my wagon 2 yrs ago - impco system and CDP-Oz. So might need a little memory jogging.
As it stands, your gas commander is doing nothing, as it has no FCV to control, and the O2 sensor to the LPG side will not be there.
Your petrol start unit and safety cutout (whereever it is) will probably still be working.

 

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96 XH Longreach 'S': LPG, Alarm, 3.23:1 LSD, Cruise, Trip Comp, ABS, Power Windows, Mid Series Dome Lt, Climate Ctrl
97 EL Futura S/W: LPG, Alarm, LED int Lts, Trip Comp, F/Lane Dome Lt, Climate Ctrl, T5 Conversion

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