Instructions to change fuel maps on 14CUX Griffith, Chimaera
Discussion
Hi all,
I finally got around to putting a socket in my spare 14CU ECU and am now looking at doing some remapping, one area I am interested in is managing the idle speeds for off-road/green laning. The standard ECU has:
1. Base Idle rpm - fixed value
2. Neutral Idle rpm - Active low when automatic transmission in N
3. Screen Idle rpm = Active high, raises idle speed by an offset when heated screen active
4. A/C Idle rpm = Active high, raises idle speed by an offset when HVAC compressor active
Have I understood these correctly and they are enabling an offset which is added to the base idle?
Are they cumulative? i.e. if 2,3 and 4 were active would I get the sum of, for example, -200 + 200 + 50 = base idle +50?
I am considering remapping a chip and experimenting with a 3.9 UK non-cat map with the following changes:
1. Base Idle rpm - fixed value
2. Neutral Idle rpm - Hill descent idle with speed lower than Base idle for short periods
3. Screen Idle rpm = Fast creep with engine speed around 800rpm
4. A/C Idle rpm = Active high, when cooling fans running - no change in offset
2 and 3 would be interlocked by wiring to low range, mutually exclusive and possibly only allowing 2 for a short period if oil pressure is deemed too low.
ETA that is need to set the base idle lower by means of the air bleed screw on the plenum then keep it at the correct idle speed by applying an appropriate offset by switching the neutral signal to 0V so there is good oil pressure for normal use.
I finally got around to putting a socket in my spare 14CU ECU and am now looking at doing some remapping, one area I am interested in is managing the idle speeds for off-road/green laning. The standard ECU has:
1. Base Idle rpm - fixed value
2. Neutral Idle rpm - Active low when automatic transmission in N
3. Screen Idle rpm = Active high, raises idle speed by an offset when heated screen active
4. A/C Idle rpm = Active high, raises idle speed by an offset when HVAC compressor active
Have I understood these correctly and they are enabling an offset which is added to the base idle?
Are they cumulative? i.e. if 2,3 and 4 were active would I get the sum of, for example, -200 + 200 + 50 = base idle +50?
I am considering remapping a chip and experimenting with a 3.9 UK non-cat map with the following changes:
1. Base Idle rpm - fixed value
2. Neutral Idle rpm - Hill descent idle with speed lower than Base idle for short periods
3. Screen Idle rpm = Fast creep with engine speed around 800rpm
4. A/C Idle rpm = Active high, when cooling fans running - no change in offset
2 and 3 would be interlocked by wiring to low range, mutually exclusive and possibly only allowing 2 for a short period if oil pressure is deemed too low.
ETA that is need to set the base idle lower by means of the air bleed screw on the plenum then keep it at the correct idle speed by applying an appropriate offset by switching the neutral signal to 0V so there is good oil pressure for normal use.
Edited by 100SRV on Saturday 7th January 23:08
100SRV
Welcome & sorry for the delayed reply, I assume you mean your 14CUX not 14CU.
Yes you are correct, cumulative, meaning the Neutral, A/C & Heated Screen idle adjustments are all add/subtract together from the base idle.
The idle speeds are RPMs in hex at the following Prom Offsets
1. Neutral: 159/15A
2. A/C: 15B/15C
3. Base Idle: 176/177
4. Heated Screen: 1E9/1EA
1. I believe the Neutral adjustment lowers the idle in drive, but not 100% sure, can an auto owner confirm.
2. A/C adjustment increases the idle when the A/C is on.
3. The heated screen input is the big surprise as it actually lowers the idle speed just when you need it increased and I believe that’s why its always 00 and never used. However, I’ve also noticed when turning on the heated screen input the idle momentarily increases before it drops by the offset and believe that why my TVR cooling fans +12V are connected to pin 8 for the heated screen.
The 14CUX was designed to be a digital copy of the analogue 4CU with the same feel but I guess Lucas took that literally and also copied all the bad side effects.
Welcome & sorry for the delayed reply, I assume you mean your 14CUX not 14CU.
Yes you are correct, cumulative, meaning the Neutral, A/C & Heated Screen idle adjustments are all add/subtract together from the base idle.
The idle speeds are RPMs in hex at the following Prom Offsets
1. Neutral: 159/15A
2. A/C: 15B/15C
3. Base Idle: 176/177
4. Heated Screen: 1E9/1EA
1. I believe the Neutral adjustment lowers the idle in drive, but not 100% sure, can an auto owner confirm.
2. A/C adjustment increases the idle when the A/C is on.
3. The heated screen input is the big surprise as it actually lowers the idle speed just when you need it increased and I believe that’s why its always 00 and never used. However, I’ve also noticed when turning on the heated screen input the idle momentarily increases before it drops by the offset and believe that why my TVR cooling fans +12V are connected to pin 8 for the heated screen.
The 14CUX was designed to be a digital copy of the analogue 4CU with the same feel but I guess Lucas took that literally and also copied all the bad side effects.
Edited by stevesprint on Wednesday 18th January 00:03
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