14 CUX pinouts

[BigJon]

I have the ECU out of my RRC at the moment (14 CUX from 96? Disco) because I want to cure my A/C on idle stalling. Everything I can find online shows that pin 33 connects to the A/C relay. I assume that is to give idle up with A/C compressor operation.

I still have that relay as part of the wiring loom that I transferred into the RR, but there is nothing connected to the other end of it. The wire from ECU pin 33 goes to the relay pin 85. The relay pin 86 wire is not connected, therefore that relay is currently doing nothing.

My A/C system still works from the original RR wiring. My question is can I just take a power feed from the current A/C clutch wiring and run it back to the ECU pin 33 to give a feed when the compressor is operating? It seems strange to me that the A/C relay is earthed through the ECU (standard Disco configuration).

[bee utey]

Most LR control circuits I have looked at switch a relay to earth via the ECU. The other side of the relay is usually connected to ignition positive. So feeding power to the ECU is unwise without further info.

Rather than using the ECU to know when the a/c is on, you could use an idle-up solenoid connected to the compressor clutch. Common in late 80's jap cars. They just bypass a bit of air via a vacuum port past the throttle plate. Otherwise check your IAC valve is clean and functioning properly, assuming you are using the later one in the back of the manifold.

[BigJon]

It looks like the ECU controls the A/C clutch then... Bit odd.

Yep, idle control valve is good, as is throttle body cleanliness, etc. I have bumped the base idle up a fraction which has cured the idle hunting with A/C off. Still hunts and stalls with A/C on.

Also going to do Mike90RRs resistor modification to the coolant temp circuit. Recently fuel consumption has increased massively.

[bee utey]

It looks like the ECU controls the A/C clutch then... Bit odd.



Not really, it can disconnect the a/c clutch for starting and delay its operation until the idle is stable. Try hooking up a test bulb between the ECU and ign positive to see what it does. If you use the D1 relay you have to cut power to the clutch it may yet work better.

[BigJon]

I would need to figure out what tells the ECU that the A/C is switched on. I guess another look at the ECU pinouts is in order. I do recall a pin for the A/C thermostat. Don't recall one for the switch.

On the other topic I just checked the resistance of my temp sender with a warm engine. 446 ohms, would account for my increased fuel use. Spec is 300 - 400 ohms with a warm engine.

[PhilipA]

I just had a look at my 89 onwards RRC manual and it shows 2 ECU inputs

The first goes to 33 and is called Airconditioning output control and should be coloured BS Black Grey. This goes to 85 on the compressor clutch relay.

The second is Airconditioning load input goes to 21 and is colour YB yellow black. and it goes to low pressure switch,then high pressure switch,then to thermostat.
Hope this helps.
it looks to me that 21 is an ECU ground which activates the compressor , when a signal is gained from the thermostat and this also gives idle up.

The signal comes from the High med low switch via the fresh recirc switch so is probably 12 volt. It comes via a didode pack.
Regards Philip A

[BigJon]

So what I should do is run a wire from the original RR A/C clutch power to pin 21 on the ECU, then utilise the pin 33 to switch another relay (which is already in the loom) to actually provide the clutch with power? Or should pin 21 be where the clutch power relay is earthed?

The trouble is I am trying to integrate the original RR wiring into the 14CUX wiring (flapper vehicle with Disco engine and engine loom).

I use this site: http://www.britishv8.org/Articles/Rover-14CUX-EFI.htm

for my ECU pinout information.

[PhilipA]

21 goes to the aircon on /off switch, via a diode, via the thermostst,via the high and low pressure switches. This all makes sense for the idle up.

33 is an earth. Pin 33 is where the compressor clutch relay should be earthed from 85.
Disregard my earlier info. I can send you the PDF of the wiring if you like to PM me your email address.

Regards Philip A

[BigJon]

PM sent Philip.

So what you are saying is pretty much what I said. If I take the original compressor power supply and apply that to pin 21, then the ECU will know when the compressor is supposed to be powered. This will take into account the thermostat and hi/low switch.

Then I use 33 as the earth side of the new A/C relay and the ECU will switch the compressor on and off when instructed by the supply coming in on pin 21. The added bonus will be things like no A/C on crank and idle up when the A/C compressor is operating.

[BigJon]

Some progress, but not right yet.

I have my coolant temp sender bypass resistor and switch wired in and it appears to work perfectly.


I have run a wire from the original A/C compressor wiring to pin 21 on the ECU.
I have reconnected the original A/C compressor wiring which goes from the A/C relay through the engine loom to the A/C compressor.

When I run the engine and turn the A/C on the condensor fans run, the idle up works, but the A/C clutch doesn't engage.

Ideas?

[BigJon]

Right, had another thought.

Will keep the pin 21 feed for idle up (which was all I really wanted/needed in the first place) and I will turn the compressor on with the original switch wiring.

[PLR]

G`day Bigjon ,

Out of interest what did you do to overcome the lack of a speed sensor , reason i ask is because the book say`s that erratic idle is a bi- product of it not work right ?

Was looking in my softy manual because it`s more descriptive than the disco 1 but pretty much the same system .

This is only the way the disco works and you may already have it .

Ign on , run , volts to ign relay , volts to Comp relay and AC relay .

Fan speed on and AC switch on gives ground to 86 AC relay through AC dual pressure switch and AC Evap temp switch .

AC relay volts to pin 21 ECU .

ECU grounds coil of Comp Clutch relay .

Volts to Comp Clutch .

Once working , controlled by AC dual pressure an Evap temp switches .

Either , control AC relay 86 ground , inturn Volts to ECU at 21 which removes/makes ground to Compressor relay .

The AC relay and Clutch relay are inter-connected .

The Clutch relay and ecu pin 33 go together .

The AC relay and ecu pin 21 go together .

cheers

[BigJon]

I am not running a speed sensor at the moment. I do have one out of a Disco, but I haven't fitted it owing to the fact it will render the speedo inoperative.

Given that my speedo cable recently failed, maybe I will get a RRC 14 CUX speedo cable and speed sensor, that way I will have a cable driven speedo and the electrical impulse.

[PhilipA]

I reckon you could rig one up by getting the speed sensor from a cruise control that goes on the driveshaft and maybe putting 2 or three magnets on it.
I think it would be harder than you think to replace the cluster.
Regards Philip A

[BigJon]

Not replacing the cluster. I had a Disco one, but it wasn't the right shape / mountings.

I believe some RRC had a cable driven speedo and 14 CUX EFI. They had a speed sensor in the speedo cable.

[BigJon]

A/C appears to be sorted. The relay in the Disco loom had a power feed for the switched side, but no power feed for the switching side. A few minutes with the soldering iron has rectified that. Now the A/C compressor kicks in when it is supposed to, with idle up happening as well.

The coolant temp sender bypass switch is mounted and fully operational as well.

I have somewhere between 500 and 1000 km or so to drive in the next week so I will be able to get some idea of fuel useage, although the failed speedo cable means the trip meter will not be working for accurate measurement.

[PhilipA]

I believe some RRC had a cable driven speedo and 14 CUX EFI. They had a speed sensor in the speedo cable.

Well my 92 has a short cable which goes over to the LH chassis rail and the speed sensor is there. I think that may be what someone means.
But the speedo still works off the sensor.
Regards Philip A

[BigJon]

I think post 88 pre 92 had a cable driven speedo. There are long and short speedo cables listed, plus a speed sensor that appears to have cable in and cable out fittings.

[mike 90 RR]

I am not running a speed sensor at the moment.


Jon .... I haven't done the research .... but a theory for you


When the car is stopped ... the speed sensor tells the ECU to just "idle the motor" and use the appropriate fuel map

When the car is moving ... the speed sensor lets the ECU know this .... and use the ""range" of the fuel map


So with the sensor not hooked up (disconnected) .... Is your ECU delivering fuel based on just "fast idle" .... rather than "motor rev" for driving



Could this be a contributor to excess fuel consumption? .....




I think post 88 pre 92 had a cable driven speedo. There are long and short speedo cables listed, plus a speed sensor that appears to have cable in and cable out fittings.

Good idea .... find 1 and hook it up :)

BTW .... The 1990 has the elec driven speedo .... Same as Phillip's ... The "speed sensor box" has the output drive for the longer cable :)



Cheers
Mike

[BigJon]

I am on the job of getting the new cables and speed sensor box.

The fuel consumption has always been higher with this engine / injection setup than the old 3.5 flapper. It has always been a slight dissapointment in that regard, although power and torque are much better. What I have noticed recently was the fuel consumption getting much worse (160km to fuel light on!, once on a 4wd trip), hence the decision to make the temp resistor modification.

I wired mine slightly differently to yours. I cut the temp sensor input wire near the ECU and joined that to the central output terminal on a three position switch. I connect the other side of the cut wire (coming from the temp sender) to one of the input sides of the switch. For the last terminal on the switch I took a feed from the wire that goes to the temp sender and ran it through a 300 ohm resistor (actually 4 x 75 ohm soldered together in series) and connected that.

Now with the switch in one position it gets the resistance of the original temp sender (for cold start) and in the other position it gets 300 ohms resistance via the resistor block.

I haven't done a trip yet to see if consumption is better.

[mike 90 RR]

..... The fuel consumption has always been higher with this engine ......


You have checked The vacy advance is working ?...... Plus made sure that all ends of the suction are clear ... I check my input hole at the Plenum side and found that to be blocked also :mad: ... A pin was used to clear that hole :D




.... and .... try cleaning the Hot Wire of the AFM




...... I wired mine slightly differently to yours......


So you flick the switch after startup (when cold) and can hear the revs drop? ....

[PhilipA]

When the car is stopped ... the speed sensor tells the ECU to just "idle the motor" and use the appropriate fuel map



AFAIK the speed sensor does three things only
runs the speedo

Kicks up the idle to 1100 when moving to smooth the 2-1 change

Speed sensor signal+ TPS less than 0.49? and revs +1500 equals overrun cutoff of injectors.
There is no idle map as such, whether the car is at idle is determined by the TPS.
In my experience the cruise and overall economy is largely determined by the amount of advance at high vacuum, and of course how you drive and how hilly it is.The 14CUX fuel maps are pretty OK.
Regards Philip A

[BigJon]

You have checked The vacy advance is working ?...... Plus made sure that all ends of the suction are clear ... I check my input hole at the Plenum side and found that to be blocked also :mad: ... A pin was used to clear that hole :D




.... and .... try cleaning the Hot Wire of the AFM




So you flick the switch after startup (when cold) and can hear the revs drop? ....

Vacuum advance unit is good, will check the throttle end for blockage.

AFM is clean (recleaned yesterday).

Yes, when cold there is a slight change when flicking the switch. Checked it all with a multimeter for correct operation too.

[BigJon]

AFAIK the speed sensor does three things only
runs the speedo

Kicks up the idle to 1100 when moving to smooth the 2-1 change

Speed sensor signal+ TPS less than 0.49? and revs +1500 equals overrun cutoff of injectors.
There is no idle map as such, whether the car is at idle is determined by the TPS.
In my experience the cruise and overall economy is largely determined by the amount of advance at high vacuum, and of course how you drive and how hilly it is.The 14CUX fuel maps are pretty OK.
Regards Philip A

If that is all it does then there is not much point in me hooking it up. I don't want the idle any higher when I am moving as I have a manual transmission. Injector cut on overrun won't help my economy much as most of my driving is open road cruise, no overrun happening. It is resonably flat between Horsham and Adelaide.
I could try some more ignition advance, but I find it very hard to pick audible pinging with this engine. I find Holden ironblock V8s are much easier to pick.

[mike 90 RR]

If that is all it does then there is not much point in me hooking it up. I don't want the idle any higher when I am moving as I have a manual transmission.

I'ld still hook up the speed sensor .... cause it stabilises your Idle (stops the hunting)

I knock my tranny into neutral at the lights and the revs are OK .... holds 750rpm .... shouldn't give you the "woop's" being a manual


My ignition is set @ 9 degrees ....

[BigJon]

$350 in parts to do it, just got the email back.

Lots of $$ there. Not sure if I am that keen!

[mike 90 RR]

Just wait for a wreck to come up ..... grab the short speedo cable n box .... out of a 1990 RR to 94 .... then find the Long cable out of a earlier model

Or someone wrecking 1 with Flapper might have the 2 cable / speedo box setup already

[BigJon]

Mine was flapper.... no speed sensor fitted.

[Hobbes]

Hi guys,
I had the exact same issue as Jon with the a/c load input which I finally resolved ( http://www.aulro.com/afvb/technical-chatter/100371-air-con-compressor-excessive-load.html ) - basically I had an aftermarket oe disco system installed years ago into a 90RRC but they'd omitted the compressor connection to the ecu...

In sorting it, I did the usual digging on the intraweb last month and came across this new article on the 14cux. It's got a lot of input from Mark Thompson (g33.uk) & Mark Adams (Tornado chips) Standard ECU 1 (http://www.rv8r.co.uk/standardecu1.html) - bloody excellent actually:)

In short, the VSS does have a lot of input !

cheers
Chris

[PhilipA]

Good article . Taught me a couple of things I didn't know. Funny others reckon the diagnostics work much better with o2 sensors.

Hmmm, maybe I will try mine without the O2 sensors to see whether I get better economy, seeing it runs at 14.3 in closed loop rather than 14.7.

I was puzzled when the dyno guy told me it was running at 14.3 as I thought all narrow band o2 sensors could only run at 14.7.

Seeing it is only a matter of changing the resistor and adjusting the MAF down a bit its pretty easy.
I would be interested to know the differences between the UK fuel maps and Australia. The UK is all high compression but I do not know what that means to the map.
Anyway I have bigger fish to fry at the moment with changing the cam and heads.
Regards Philip A

[Hobbes]

Yeah, I'll post the link to that (and a few other off forum bits) in a new thread so it's easy to find - There's some interesting stuff buried in the TVR section of the Pistonheads forum.
My RRC is ex UK, high comp and of course runs the UK tune - it much prefers a diet of 98 octane, even on 95 it's middle name is "pink" under load. Whether that's just a function of comp/advance or mapping hard to say.
I was going to say I could check by wiring in a switchable tune resistor - but on reflection easier to email Mark Thompson in the UK and ask!

[BigJon]

Hobbes, what is your timing set at? Pinging or pinking is usually caused by too much ignition advance for the engine compression and octane rating of the fuel.

[Hobbes]

sorry didn't mean to half hijack your thread!!!
Last time it was tuned we settled on 9deg BTDC static topping out at 34deg on the basis I'm happy/foolish to run premium!

[BigJon]

No worries with a thread hijack.

[BigJon]

Highway driving fuel consumption with the ECU temp sensor resistor mod has dropped from 20+ litres per hundred to 15 litres per hundred. I am pretty happy with that considering the mod cost my about $5.