Instructions to change fuel maps on 14CUX Griffith, Chimaera

[blitzracing]

Joolz put a 20 AM on a 3.9, and the gains where negligible over the stock AFM- you need a bigger engine to make use of the better airflow.

[jjohnson23]

Blitzracing,you are correct about the airflow meter,perhaps worth me looking at a Bosch one as they are readily available as the 20am and 3-5am ones are no longer available new.(The Chinese copies are rubbish from what I can make out.)
I am not looking for better performance but for a straight(ish) factory replacement once I have modified the fueling to suit.

[jjohnson23]

One problem i`m having at the moment is the speed limiter.
In previous posts its been placed at $EA41 which I can`t seem to work out.
Anyone able to help a thicko out please?
Another is that in R2422 Griff re cat_250.bin,the tune resistor is set at FF which I thought was meant to disable the tune resistor option.Can anyone clear this up for me please,i`m getting a bit confused now.

Edited by jjohnson23 on Sunday 4th January 18:06

[danbourassa]

jjohnson23 said:

One problem i`m having at the moment is the speed limiter.
In previous posts its been placed at $EA41 which I can`t seem to work out.
Anyone able to help a thicko out please?
Another is that in R2422 Griff re cat_250.bin,the tune resistor is set at FF which I thought was meant to disable the tune resistor option.Can anyone clear this up for me please,i`m getting a bit confused now.

Paul, if you're looking at tune R2422, the speed limit value will be in a different location than the R2967 tune. If the code is different, all code after the first difference will be shifted. For R2422, the $C4 value may be at $E6D0 (or $26D0 depending on your file). R2422 also has the older fuel map locations in the data section, so, like the code, everything is shifted. This probably also explains why you got so many differences when comparing files.

[jjohnson23]

Many thanks for the explanation,I got too wrapped up in looking for it that I forgot about that altogether.
Its a lot to take in but I find myself looking through the data very interesting for some reason,I think that the fact I may one day be able to mod fueling properly is the draw.

[JOA]

Thanks everyone for all of the valuable information you have been posting in this thread. In the spirit of following in your footsteps I have been playing around with the fueling on my 1990 Range Rover the last couple of days and have a couple of interesting things on which I would like to get your folks opinion.

I installed a wideband O2 sensor and noticed that my fueling seemed rather lean past about 3400rpm; the AFR>16. I noticed this behavior using both open and closed loop maps, maps 2 and 5 respectively with my Operation Pride 3362 tune. I started playing around with the fuel map values in map 2 and was able to get my AFR down to about 14.5 by maxing out the fueling values to FF in the higher load bins. It seems to me that I should have been able to obtain a much richer mixture than this by maxing out the fuel map bins.

Today I tried changing the fuel map multiplier at C3F9 and the row multiplier at C483 to see if I could shift the fueling to richer values. Neither of these values seemed to have the slighted effect on my AFR. Even when I made rather drastic changes, like maxing out the values, there was no difference. I finally loaded a different tune, 3526 that I downloaded from Dan's google drive. When I changed the fuel map multiplier in the newer tune I got large changes in the fueling. For example, when I changed the fuel map multiplier from 5DBE to 6DBE my AFR dropped from 14 to 12. I am wondering why my old operation pride tune 3362 seems not to respond to changes in the fuel map multiplier. Also the newer tune did not run lean at higher RPM despite having essentially the same fuel map values.

Thanks everyone,

[blitzracing]

The 3400 rpm point is when the map goes open loop anyway, but the difficulty is trying to work out if the ECU is simply going into cruise fuelling as you have to be under maximum load to see the richer mixture- although I see the same fuelling pattern as you, but it does richen up when you hit full throttle. I cant tell if this is simply the additional fuel being added for acceleration enrichment, as I cant hold it flat out for long enough to see the beyond the acceleration point and live to tell the tale on the open road.

[danbourassa]

Hi Joel,

First, I have to say that I'm always pleased to hear when another American is interested in this thread. The older Range Rovers are quickly disappearing and we don't have too many 14CUX sports cars over here to keep interest alive.

I don't believe that R3362 is Op Pride. Did you mean R3652? Either way, it doesn't matter too much because all L-R versions from at least R3360 onward represent the latest version of code. Differences at this point were mostly limited to fuel map changes and other details in the data section. Even Op Pride had only a few minor difference. They changed the RPM threshold between a cranking engine and a running engine from 500 RPM to 375 RPM for extremely cold startups.

That said, I can't explain the difference in functional behavior that you experienced. Are you sure that you were running map 2 when you changed the map 2 multiplier?

Also, I don't understand why you would expect a greater change in AFR when maxing out the bins. The change from 16 to 14.5 is about what I would expect when changing from say E0 to FF. Were your changes much greater than this?

[JOA]

Mark and Dan,

Thanks for the replies. Dan, I was extremely excited when I found out that you had reverse engineered the code and that there was now a diagnostic tool, Rover Gauge, available with which we could view realtime engine data. It is a shame that the Range Rovers are disappearing because they are one of the least expensive, yet competent, off road vehicles available in the US.

The tune I found in my ECU was R3362. I don't know why I thought it was Op Pride, maybe I just assumed since it was obviously not the original chip.



According to Rover Gauge, Map 2 was selected and I could see the fuel map bins and the fuel multiplier change on the Rover Gauge screen when I uploaded changes to my Ostrich.

As far as my expectations of greater changes in AFR when maxing out the bins, E0 to FF sounds about right, it is probably just my inexperience at tuning. I just assumed that by maxing out the fueling values in the bins I should be able to get down into the 12 AFR range. Everything I have read indicated that ideal AFR should be in the 12's when running wide open throttle at high RPM. It seems strange to me that Land Rover would have deliberately run these trucks lean at high RPM. Again maybe just my inexperience speaking, but 16 seems very unideal, maybe even unsafe at very high load/RPM.

There is another question I have really been wanting to ask you guys. What is the difference between High Compression and Low Compression tunes? My Range Rover had a 3.9L Low Comp engine in it when I bought it, but I replaced it with a higher compression 4.0L from a 1996 discovery. The new engine is the same displacement, really the same engine, just higher compression so I did not expect it to need different fueling.

[danbourassa]

Joel, I don't have an answer yet on your question but I did want to comment on your circuit board. It appears to be original for a 1990 RR yet it has the PROM on a socket. Early boards that I've seen don't have a socket. Do you know if this was done by a previous owner? Was there a black plastic snap-on cover on the PROM? What is the part number on the ECU? I imagine that the it's an early PRC part number (lower than PRC9060) and not the later AMR number. Sorry for all the questions but I must know!

[JOA]

Dan,

I am happy to provide any and all answers possible.

Based on the handwritten sticker on the ECU I would say that a dealer installed the updated tune on 1-9-96, and you are correct about the part number; it is PRC7081. I am pretty sure that the chip socket is original. I am pretty good at soldering and I could never have made it look this factory.



There was a black plastic cover over the PROM; I had to pry it off in order to remove the chip.

[Mark Adams]

JOA said:

Dan,

I am happy to provide any and all answers possible.

Based on the handwritten sticker on the ECU I would say that a dealer installed the updated tune on 1-9-96, and you are correct about the part number; it is PRC7081. I am pretty sure that the chip socket is original. I am pretty good at soldering and I could never have made it look this factory.

There was a black plastic cover over the PROM; I had to pry it off in order to remove the chip.

All early ECUs until somewhere in mid-1991 had sockets. All NAS versions had sockets too, and the black plastic cover was used to stop the chip working loose or fretting with the endless heat/cool cycles.

That being said, PRC7081 is not a NAS ECU. However R3362 is indeed a NAS tune, that would have been retro-fitted at a dealer. As a NAS tune, it will always use (White) tune 5. There fore any changes you make in the other tunes will be ignored.

More worryingly, this late tune should not be used in an early ECU as it will cause idle and O2 feedback issues.

[Mark Adams]

blitzracing said:

Joolz put a 20 AM on a 3.9, and the gains where negligible over the stock AFM- you need a bigger engine to make use of the better airflow.

Pretty much what I've been saying for the last 24 years then...

[danbourassa]

Mark Adams said:

All early ECUs until somewhere in mid-1991 had sockets. All NAS versions had sockets too,

My experience has been different. The first NAS ECU I ever opened (a PRC9060 with chips dated mid-1990) had no socket. I have collected a number of ECUs since but they have mostly been later AMR units for fear of getting another without a socket. The AMRs have all had sockets.

Mark Adams said:

As a NAS tune, it will always use (White) tune 5.

Yes, but the resistor is ignored and not even supplied with all but the earliest NAS Range Rovers. Tune 5 is locked in software. I have also seen NAS specific wiring harnesses that are missing the pin 5 terminal in the 40-pin connector. I think that our EPA did not want the tune map to be easily changed.

Mark Adams said:

More worryingly, this late tune should not be used in an early ECU as it will cause idle and O2 feedback issues.

Are you saying that there are functional differences in the ECU itself (i.e. other than the PROM)? And, if so, can you tell us more?

[JOA]

Mark Adams said:

All early ECUs until somewhere in mid-1991 had sockets. All NAS versions had sockets too, and the black plastic cover was used to stop the chip working loose or fretting with the endless heat/cool cycles.

That being said, PRC7081 is not a NAS ECU. However R3362 is indeed a NAS tune, that would have been retro-fitted at a dealer. As a NAS tune, it will always use (White) tune 5. There fore any changes you make in the other tunes will be ignored.

More worryingly, this late tune should not be used in an early ECU as it will cause idle and O2 feedback issues.

Yes, when I first exchanged my 3900ohm tune resistor for a 470ohm resistor I thought that I had changed to a non-cat map. I drove it around for about a year feeling like I had accomplished something until I got a copy of Rover Gauge and realized that I was still running Map 5. Once I changed the byte at memory location C7C1 to a value of 00 Rover Gauge reported that Map 2 was selected.

Yes, it runs poorly on Map 2 with R3362. Tow strange things I have noticed while running the R3362 tune are:

1. In Map 2, a most annoying high idle when coasting to a stop. The ECU holds the idle at around 1200RPM when coming to a stop which actually makes it somewhat difficult to bring the truck to a stop. After about 2seconds at zero speed the ECU will bring the idle back down. This phenomenon is not present when using the R3526_(R3360A)_3.9_High_CR tune that I downloaded from Dan's google drive.

2. In Map 5, I noticed that the AFR occasionally jumps up to and sticks at around 15.5 when idling. I am not sure how the ECU is doing this since I think that 15.5AFR is outside of the range of a titania oxygen sensor.

Incidentally, I have tried to force the ECU to run in closed loop at an AFR other than 14.7 by altering the oxygen sensor set point. I did this by modifying the code between C222 and C223 to force the ECU read a hard coded value instead of the analog value from channel 13. I succeeded in being able to swing the AFR lower by giving the ECU a rather large set point value. A fixed value is of course impractical since subsequent variations in the alternator's voltage will cause errors in the O2 sensor readings.

[davep]

JOA said:

Yes, it runs poorly on Map 2 with R3362. Tow strange things I have noticed while running the R3362 tune are:

1. In Map 2, a most annoying high idle when coasting to a stop. The ECU holds the idle at around 1200RPM when coming to a stop which actually makes it somewhat difficult to bring the truck to a stop. After about 2seconds at zero speed the ECU will bring the idle back down. This phenomenon is not present when using the R3526_(R3360A)_3.9_High_CR tune that I downloaded from Dan's google drive.

Joel, that's interesting thanks for flagging that up. If you check the respective data sections for Fuel Map 2 and 5 there are usually different data values declared for the last four DBs:

Fuel Map 5:
LC7BD DB $7A ; value stored in X200E (yet another fuel map value)
LC7BE DB $2C ; value stored in X200F (a coolant temperature threshold)
LC7BF DB $49 ; value stored in X2010 (todo)
LC7C0 DB $64 ; value stored in X2011 (multiplied by abs of throttle delta)

Whereas for Fuel Map 2 the values are: $24,$23,$68,$4C.

Time to look at the code to see what the repercussions are and if idle control is impacted.

[danbourassa]

Dave is correct. If there is a difference in behavior between maps, it must, by definition, be a software difference only.

Also Joel, I would not necessarily expect any map in R3362 (other than 5 and limp-home) to be useable, as is. The unused maps in locked NAS PROMs were never expected to be used and could have just as easily been all $00 or all $FF. Certainly, in that case, we wouldn't expect them to work.

[davep]

davep said:

JOA said:

Yes, it runs poorly on Map 2 with R3362. Tow strange things I have noticed while running the R3362 tune are:

1. In Map 2, a most annoying high idle when coasting to a stop. The ECU holds the idle at around 1200RPM when coming to a stop which actually makes it somewhat difficult to bring the truck to a stop. After about 2seconds at zero speed the ECU will bring the idle back down. This phenomenon is not present when using the R3526_(R3360A)_3.9_High_CR tune that I downloaded from Dan's google drive.

Joel, that's interesting thanks for flagging that up. If you check the respective data sections for Fuel Map 2 and 5 there are usually different data values declared for the last four DBs:

Fuel Map 5:
LC7BD DB $7A ; value stored in X200E (yet another fuel map value)
LC7BE DB $2C ; value stored in X200F (a coolant temperature threshold)
LC7BF DB $49 ; value stored in X2010 (todo)
LC7C0 DB $64 ; value stored in X2011 (multiplied by abs of throttle delta)

Whereas for Fuel Map 2 the values are: $24,$23,$68,$4C.

Time to look at the code to see what the repercussions are and if idle control is impacted.

After a quick look at where the variable in X2010 is used since there is a big difference in the initialisation values from the specific fuel map data sections: Fuel Map 2 has $68 (104) and Fuel Map 5 has $49 (73); here’s what I think:

There is a counter called tpMinCounter that is used to slow down the ‘set Throttle Pot to minimum adjustment’ function (which is initialised with a value of $34 (54)). With the throttle butterfly rapidly approaching its minimum or closed position (the car coasting to a stop scenario) the counter delays the corresponding drop in RPM. Since the Fuel Map 2 count is the higher value, RPM is held at 1274 rpm for a longer period compared with Fuel Map 5.

-OR-

The stepper motor is gunged up and sticking.

[jjohnson23]

Is there any chance of some of you clever people creating more tables and scalars for Tunerpro?Especially for non cat tunes.
A lot of work been done making sense of the information on the eprom but I for one get very confused when working with the prom images as I am only a mere mortal.By the way the check sum fixer in the 14cux toolkit is a cracking little bit of kit,even I can use it.
I am stuck at the moment without being able to do real world testing and look forward to trying some of the mods when I get the car on the road.

[stevesprint]

jjohnson23 said:

Is there any chance of some of you clever people creating more tables and scalars for Tunerpro?Especially for non cat tunes.
A lot of work been done making sense of the information on the eprom but I for one get very confused when working with the prom images as I am only a mere mortal.By the way the check sum fixer in the 14cux toolkit is a cracking little bit of kit,even I can use it.
I am stuck at the moment without being able to do real world testing and look forward to trying some of the mods when I get the car on the road.

This sounds like a job for SteveSprint. Paul, do you mean things like the following:-
Map 2 Throttle table,
Map 2 Start up enrichment
Map 2 Temperature Fuel Multiplier
Dynamic column headings for the main fuel table
MIL lamp enable/Disable

Plus it now sounds like I should also add these,
LC7BD DB $7A ; value stored in X200E (yet another fuel map value)
LC7BE DB $2C ; value stored in X200F (a coolant temperature threshold)
LC7BF DB $49 ; value stored in X2010 (todo)
LC7C0 DB $64 ; value stored in X2011 (multiplied by abs of throttle delta)

If my Griff was on the road I’m sure I would rush out tomorrow and start testing them.

Anything else anyone???

Paul, I'll try and add these before you get your car back on the road.
Cheers, Steve
P.S. I'm not one of the clever people.