Thread: 3.9 to 4.6 Fuelling?

Probably the tornado chip is the best alternative as interceptors such as Unichip and I presume Haltech cannot do one thing and its the thing you want.
That is they cannot increase the total duty cycle of the injectors as programmed into the 14CUX. The Tornado does this.
The limitation of the 14CUX for larger engines is that it is limited to AFAIR about 70-75% duty cycle.
The injectors are quite big at 23.5Lbs per hour vs a Commodore 5 litre at 18lbs per hour.
Regards Philip A

The standard 3.9 injection will fuel a 4.6 just fine , If you want more performance yes go some other brand of computer

Although a 4.6 will run under a 3.9 map, it will be far from optimal. Your 3.9 injectors will be fine however an ajustable fuel regulator might help.

First the 4.6 is going to require more fuel on full load due to the larger capacity. Running lean means hotter engine and that really needs to be avoided in LR engines bigger than 3.5. This difference alone is also worth 20-30 BHP on full throttle! Then again how often doesa that occur.

However the fuel is also metered according to air flow into the engine by the MAF. Air flow is proportional to torque for this type of fuel injection system, so it is therefore very closely related to engine size. If the peak airflow is not recalibrated by using a different fuel map EPROM to match the 4.6, you will find 4.6 engine running on a 3.9 map will operate too far up the fuel map leading to over fuelling at part throttle. That is expensive.

You could use say a Haltech piggy back chip and do away with mechanical advance on dizzy OR new EPROM in ECU. I would go the latter route and spend money saved on Hatech on recalibrate advance on a dyno. I think you will find local EPROMS and Adams Tornado EPROM about the same price. My choice is the Tornado only as I have no experiance with any others. While your at think about changing your 5AM to a 20AM out of a GEMS RR. They are worth a hundred or so second hand. I see you have 1995 so you need to check and see your ECU came with a socketed or soldered EPROM. Mark will set you up with all you need however if you don't trust your soldering of a socket into ECU do a ECU swap out here using wrecker or Ebay.

I have some instructions on the above so send me a PM. Good luck with your your upgrade.

I'd suggest option 4...

Rip out the ECU and fit a Haltech system (complete system) around $1800.00 from TRS supplied fitted and tuned.

Traco i think all the advise you have got so far is right but under different criteria.

PhilipA is spot on about total "duty cycle" increase with a new 4.6 specific EPROM. He doesn't mention you will also get with a Tornado EPROM little things like "check engine" warning lamp happening which 14CUX ECU's in Australian LR's didn't get.

rangierman is right a 3.9 ECU will fuel a 4.6 ....however not too sure you could say "just fine" though.

Tombie says "Rip out the ECU and fit a Haltech system (complete system) around $1800.00 from TRS supplied fitted and tuned." That will work a treat and would be my preference but I do question the $1800 as total cost? That $1,800 will just get a Haltech Interceptor or simple piggy back tuned on a 4WD dyno by someone competent (and inferior outcome to 4.6 specific fuel map for reasons stated by PhilipA), and is surely not true cost of a "complete system" tuned on a 4WD dyno, things like digittal amp etc swap over etc etc Tombie?? If $1,800 is it then wished I lived in Adelaide around corner from TRS.

My vote is still rechip your ECU, upgrade MAF and save for a quick trip to dyno to do a very basic recalibrate or advance and get best out of your new EPROM map, you can all do yourself and less than 1/2 cost and bother of a replacemnt ECU route.

I paid less than $1800.00 for mine

TRS (Phil) did an awesome job, benefits were that I lost the MAF (went MAP) and got full ignition timing control too..

The "Tornado" solutions wont be properly tuned to the particular vehicle either.

Originally Posted by Tombie2

I paid less than $1800.00 for mine

TRS (Phil) did an awesome job, benefits were that I lost the MAF (went MAP) and got full ignition timing control too..

The "Tornado" solutions wont be properly tuned to the particular vehicle either.

If less than <$2K all up ....that is a very attractive Tombie.

However not quite correct to say Tornado wont be tuned to vehicle. They are not off the shelf EPROMS. Adams will give you a fuel map or maps that match engine setup. While you can "plug and play" you really need to dyno tune inc adjusting CO trim on MAF and respringing/calibrating ignition.

Thanks everyone. I was under the impression a Haltech swap was more like $3k but perhaps they have come down a bit since the last time I enquired.

Tornado chips are selling for UKP411 less 15% VAT for overseas customers according to Mark Adams. And they can be tailored to suit the engine's exact requirements.

Hotwire was used on the 4.2 engines (4.275cc) and the 4.6 engine is 4.552cc. so only 277cc. extra capacity so it's not a great increase, though I'm not sure if the 3.9/4.2 ECUs used the same fuelling chip.