1994 400HC Fuel map confusion.

[stevesprint]

legacy4cam said:

Thanks for replying Steve.

There is a tune resistor, more confusion though, its white wires but resistance measures 460ohms rather than 3900 I see quoted online for a White tune.

How do I know if the Ecu can see it.... or is that a daft laddie question....

Iain.

Very strange, sounds like the previous owner may have changed the small resistor in the clear sleeve to change maps but not the white wires and blue plug, was the resistor unmolested in a clear flat heat shrink sleeve like this or did it look tampered with?



Have your cats been removed? you'll know if it fails the MOT, if not using map 2 you run the risk of contaminating the cats as Mark Blitz explains.

legacy4cam said:

At warm idle I have idle bypass reading of 9%, is this too low?
MAF reading direct 31%
Throttle corrected 0%

All look good, your idle bypass is a little low but ok.

davep said:

400 HC on the label means that the guy at TVR responsible for tuning the ECU ensured that it and the original tuned TVR engine in your car worked as one.

Did you take a screenshot of map 2 before you changed the resistor or notice the CO Trim as it may help identify the issues with map 2 ?

legacy4cam said:

Mmmm,

If the ECU is suspect, what is the best source of a reliable replacement, and is there differences between the TVR ECU's and the Land Rover parent unit which you read the part number from on the labels..

All Land Rover and TVR 14CUXs from 1992on are the same except for the tune chip, but unfortunately some have the tune chip permanently soldered in.

I doubt its the ECU as they are generally very reliable.

[legacy4cam]

Steve,

The resistor was not like your photo, it was in a bit of black heat shrink and wires cut back a bit shorter . So probably been changed by someone.

Interestingly I was cycling past be of the old TVR dealers in Scotland , popped in to see if anyone still worked there with RV8 memories, and the owner and mechanic ( young lady unusually) were both adamant that the Chim RV8's should always have 460 ohm resistors and by fitting the 3900ohm one I had somehow caused all my own issues......despite some negative comments about owners messing about with their own cars , they did seem knowledgable , albeit some opposing views to everything I can read online. ( another sin, Internet research, it would seem) .

So , anyone else's Chimaera with cats been supplied from the factory not running a Cat fuel map?

A little knowledge is dangerous, hence why I'm trying to learn a little more....lol.

Cheers, Iain.

[Belle427]

Sounds like someone has changed it in an attempt to try and cure something. If you have a read through some previous threads regarding tune resistors you will see that some people have improved low speed shunting by switching to this tune, which is what may have happened.
Id be more inclined to listen to the guys knowledge on here, no disrespect to the dealers you visited in Scotland.
Be nice to get some insight regarding the tuning of these ecus before they left the factory by the people that used to do it.

[davep]

legacy4cam said:

...the owner and mechanic ( young lady unusually) were both adamant that the Chim RV8's should always have 460 ohm resistors and by fitting the 3900ohm one I had somehow caused all my own issues.........

This is based on an extract from Land Rover documentation:

0 Ohms			Fuel Map 0	Limp Home Map 0
180 Ohms	Red	No Cat	Fuel Map 1	Australia and "the rest of the world."
470 Ohms	Green	No Cat	Fuel Map 2	UK and European vehicles without catalytic converters
910 Ohms	Yellow	No Cat	Fuel Map 3	Saudi vehicles (without catalytic converters)
1800 Ohms	Blue	Yes, Cat required	Fuel Map 4	Saudi vehicles (with catalytic converters)
3900 Ohms	White	Yes, Cat required	Fuel Map 5	USA and European vehicles with catalytic converters
> 3900 Ohms			Fuel Map 0	Limp Home Map 0

The 14CUX tune resistor sensing code within the ECU never varies, which means:

All Rover V8s running a 14CUX Engine Management System require a tune resistor in the range 180 - 3900 Ohms, otherwise a fault code is flagged and Fuel Map 0 is selected. This excludes '90s onwards NAS or US spec Rover V8s, where there is no tune resistor and the EMS is internally locked to Fuel Map 5.

All TVR V8s running a 14CUX and an engine using catalytic converters with Lambda sensors require a 3900 Ohms tune resistor unless the car was destined for Saudi Arabia. This ensures that the ECU runs the code required to perform Closed Loop fuelling management.

All TVR V8s running a 14CUX with an engine that does not have catalytic converters with Lambda sensing require a 470 Ohms tune resistor unless the car was destined for Saudi Arabia. This ensures that the ECU does NOT run the code required to perform Closed Loop fuelling management, instead the code uses Open Loop fuelling management.

All TVR V8s running a 14CUX Engine Management System were remapped and tuned at the factory, where changes were made to Fuel Map 2 or Fuel Map 5 only according to engine size/tune and Cat/No Cat. No other maps (0, 1, 3, 4) were altered, so remain as Land Rover tunes.

Regarding the extent of TVR's ECU tuning, here's an extract from SteveSprint's excellent website @ http://home2.btconnect.com/stevesprint/remap-14cux...

All TVR tunes/maps use one of two different software program versions R2422 and R2967. Precat 400 & 430 Griffith both run the R2422 software, which is exactly the same software program version as Land Rover's 1990 version R2422 but obviously with different fuel data. All catalyst equipped TVR’s from 1993 on including all 400’s to 500’s run the specially modified software version for TVR called version R2967 that is similar to Land Rovers 1994 UK program version R3383 but less an A/C enhancement. Once TVR’s software program branched away from Land Rover’s software program base TVR didn’t then go back and incorporate Land Rover's 1995 final refinements in versions R3652 to R3654 called Operation Pride.

Finally, a quote from TVR's engine guru John Ravenscroft:

..."No TVR left the factory with a standard Range Rover ECU. The amount of modification depended on the state of tune and intended application. Most had the following modifications:

Removal of the speed limiter which prevents Range Rovers exceeding their tyre speed rating of 112mph.
Increasing of the rev limiter in line with the camshaft and valve train capabilities
Adjusting the idle speed control to achieve the best compromise of emission levels and smooth running.
Re-calibration of the main fuel maps (including cold start and accel/decel maps) to achieve the best power output, fuel economy and smooth running consistent with low exhaust emissions.
Modification of the closed loop control strategies and overrun fuel cut-off for improved driveability and emissions performance (cat cars only).
Re-calibration of the air flow meter input to cope with high air flows (5 litre engines only). "

Edited by davep on Monday 29th May 10:11

[legacy4cam]

I'm on hold as during the latest search through the components possibly contributing to occasional poor running and idling, I've found a couple of plug leads with signs od arcing and degradation.
New set of Bosch leads ordered, and a new Bosch coil while I was at it.

I'll get the stepper motor out to check operation as the recent test resulted in high idle from start ,not correcting down even after 20 seconds or so running. Ignition off is resulting in the stepper making a noise as if its returning, but something is amiss.

I will add some thermal socks I think to protect the leads a little from the direct radiated heat from the manifolds. I expect a bit of response to this , seen lots and lots of commentary elsewhere....

Iain