I need advice for my difficult mix of bits.

Howdy ECU wizards’ who have gone forth before me. This is a hard one there are a lot of different factors in the mix of this build, and I need help.

The problem: I am an Australian who is suffering from having a weirdly driving and self-deprecating “need” to tune an engine that is old, not commonly modified, or supported. I’m looking for some advice on which product to use. It’s a daily drive and off road car, not a drag or track car. It’s not an easy job with an off the shelf plug and play solution. Tuners don’t seem to know what to do and run away. So I find myself learning to do it myself. (Insert sympathy here)

The offending engine: Is a 1989 to 2003, 3.5L, all alloy V6, quad cam, 215BHP, ISUZU. That was rebadged by GM, Holden and Honda and used in such vehicles as Jackaroo/Trooper, Frontera/Rodeo/Passport and Vehicross.

The ECU: Uses a Delco EPROM, so from what I understand from two decade old forums, it is not able to be flash programed without removing the chip from the board. I am led to believe the support for doing this on a 25 year old car is no longer around?

Tuning style: I have a model of car that has a BorgWarner controlled torque on demand auto transmission and other components like the gauge cluster, fuel pump, anti-theft etc that require the can bus connections from the OEM ECU. So I think this puts me in the much hated piggyback category ???? Or a partial stand-alone running alongside the OEM ECU dribbling out just enough info so it doesn’t throw codes at me.

The model car: I have collected 3 different vehicles with the same engine. Two extras for spares and experiments (manual Frontera, auto Jackaroo), to support my one build on the rare Vehicross. Only 5958 made, only 1805 in RHD, and none were ever sold in Australia. So only a handful here from private imports. I have only seen 6 others here in over a decade. It is a concept car that got a short production run. Looks like a sports car/SUV on a short wheelbase 4x4 ladder chassis. Standard with torque on demand transfer case, Recaro seats and the first ever production car to have a color reversing camera.

The hardware setup that needs the tune: I fitted an imported professional 3” lift from the States which replaced trailing and control arms, ball joints, shocks, springs and braided brake lines. Designed when Vehicross won its class in the Dakar rally. Larger slotted brake rotors, softer pads. Increased the tire size to 33” and reduced the diff ratios to match. I have added a “Detroit style” Aussie locker to the front independent suspension diff. And a selectable locker to the 3 link live axel rear. The transfer case has selectable 2WD, 4WD and 4WD low. When in 4x4 the separate BorgWarner ECU automatically steps the power to the front drive shaft depending on driving conditions monitored by 12 sensors from 15% to an equal split 50/50 front and rear. The auto gearbox has a power button that increases the rev shift points. I have a custom all stainless 2.5” mandrel bent exhaust. Complete from the tuned headers into two high flow cats then joined together for a fairly large muffler and resonator. The OEM O2 sensors are just before the cats. Designed with Increased flow in mind but with still backpressure for torque and not too loud. An Eaton M62 roots supercharger kit running 5psi pulleys, which replaces the intake and repositions the existing cable operated throttle body (not drive by wire) which is said to deliver an extra ~50bhp over the existing factory 215bhp. It has a vacuum operated mechanical bypass for when at idle. Standard fuel pump, regulator and injectors 273cc/min. Running standard compression heads and gaskets. EGR blocking plate, oil catch can on PCV and breathers.

The desire: Australia is a large place with some cool off road exploring to be done. I would like to adjust fuel and timing to a Stoich economy map for daily drive and long distance HWY use. But use the gearbox “power button” to trigger a selectable second map that gives me peak torque, but retains the reliability needed for remote exploration.

Me: I have quite a lot of automotive wiring experience and electrical understanding, with a matching mechanical ability. I can fabricate, modify, wire and fault find. This 50yr old electrical engineer can tune, rebuild and put a roll cage in anything with a carburetor and a distributer in his sleep. But despite the 9 vehicles and 2 motorbikes in my yard I have yet to purchase any EFI tuning equipment. I have good bidirectional workshop quality OBD2 scanner. And have learnt just enough tuning knowledge to be dangerous. I am interested in building a tune myself but I’m certainly not opposed to seeking professional help. I’m able to design a diode and relay trigger output from the gearbox. But I’m too new to this and the engine is too old for me to google the correct equipment to throw my money at.

The Question: Please point me in the direction of a Piggy back ECU, AFR with wideband data logging and laptop software that play together. So I can put the car up on my hoist and solder it all into my rare as hen’s teeth wiring harness. Or learn me up, or correct me on what is the best way forward for my project.

Please and thank you.

Many stand alone ECU's will allow you to control nearly any engine so long as you are willing to put in the effort. Your problem will be the shortcut in many ECU's is having an engine they already have a base map for, or at least is similar that gives you a really good head start.

So one way or another you'll likely need a dyno initially to do some stead state and get it running with a base map.

Given the odd setup and that its mostly a daily, i'd be going a ECU that has good self learn so that if your base map is rough, it can make it better as you drive it. A Haltech S3 would be the go to in my view.

Haltech's software is fairly easy to learn, but their ECU's self learning stuff is amazing. Especially the new transient throttle (MAP predication) system is unreal for a daily, as this make it drive smooth. I've had cars with base maps that are super rough, and after even a few hours of just driving around, idle control is sorted, cruise performance and O2 control is spot on and transient throttle is also bang on.

Would also give you option in the future to easily swap to DBW and add cruise control and give you the option to dial down or up the throttle sensitivity when offroad with a rotary dial or keypad or even use the 4x4 switch in the transfer to trigger it.

Have you actually driven it with a wideband in the exhaust? I would assume it already targets a dappled lambda 1 in cruise conditions with the existing ecu? Unless you want to target lambda 1.1 in cruise you are unlikely to gain anything meaningful in cruise economy unless the factory ignition timing is woefully retarded.

You are probably limited by the factory injectors and the operating window of that supercharger in terms of gearing it up much further too. If you really want to tune it for the sake of doing so go nuts but you are probably talking vary marginal gains in economy and peak power over what it is delivering now.

Tyre selection would likely yield a larger gain in economy unless it is running significantly richer or retarded than expected in cruise at present. Else reverting to original diff ratios for lower cruise rpm but a higher numerical transfer reduction gear (if available) for low range to maintain offroad capability.

You are probably best to do some wideband and EGT logging with a generic device to see how hard it is currently working at cruise to try to balance engine rpm and load depending on if it is thermal or efficiency limited at present.

Hi Paul, thank you for your suggestion of the Haltech S3, I will read up on that now. But I’m concerned about the amount of OEM vehicle features I would lose if I go to a full replacement. I know the engine would be well accommodated but all the other creature comforts that are currently controlled by the OEM that led me to assume I’d have to go with a piggyback?

Hi Slides, cheers for replying, I have not purchased a wideband gauge yet as I was first attempting to find out what ECU I would use so. I could buy a wideband that would talk to it without much fuss. I am quite keen to have a look as the engine was never released with any sort of forced induction so I’m assuming there is no corresponding map in the OEM ECU for positive manifold pressure?

I’m sure the standard injectors and fuel rail pressure are not up to the top end of the task. The Alpine techs that designed the bolt on top end charger kit were aiming for 4.9psi as that was the best bang for buck in regards to load for output. Others changed pullies to achieve 7psi and 10psi on standard compression. But I’m lead to believe that came at significant heat and fuel usage. On reading older forums there was talk of adding a 7th injector to pull it up to where it needed to be. But being off road I’m chasing torque figures and am happy to accept whatever HP happens is associated.

Is there a particular AFR gauge with data logging output you would recommend?

You'd be surprised Ben what the new gen of stand alone ECU's can do. Especially if you are handy with the wiring.

I run the Haltech Elite 2500 (predecessor to the S3) with a PD16 (Power Distribution Module) and it runs the entire car, and i do me everything. Including lights, wipers, rear demisters, cruise, hazards, dash, even the horn. And on some newer cars they can integrate into the factory can bus. For instance on later model subaru's speed and ABS sensors is controlled via a body control module, which the Haltech can talk to even with the factory ECU removed.

I'd suggest downloading the Haltech NSP software if you are curious and just open a new file and have a poke around

A lot of the standalone ECU's including Haltech even have the ability to control an automatic transmission, inc lock out functions, shift points etc

Often given the controllability and flexibility you have with the standalone the car will drive and operate better with more power and better fuel economy with all the comfort of knowing the ECU's brain will monitor the health of the car way better than the factory ECU even protecting the engine if need be

Hi Paul, I honestly don't know the capabilities of any of the ECU models which is why I am asking for advice like this thank you :)