4x2 Lexus 1UZ VVTi conversion options

[IndianaJones]

Hi folks

So I want to do a Lexus 1UZ VVTi conversion on a 4x2 2800D Colt bakkie, myself. The Colt is an everyday driver, and shop truck. I need it to be reliable and I don’t have an open chequebook for the build. First off, I would need to make some choices, and here I need your much appreciated input. Most choices would probably come down, to which is the most cost-effective solution.

I want to purchase a pre-wired engine and need to decide between the OEM ECU setup with the Bussmann fuse system, or the Spitronics ECU system. I feel each system have their merits, my only concern is that I probably need to change the diff ratio when using the OEM ECU and auto box, which will add to the cost, while the Spitronics might be fettled to work, but that then points to some time on the dyno, comments will be appreciated.

Furthermore I need to decide whether to use the standard 5-spd automatic which comes with the 1UZ VVTi, or change to a manual gearbox. I would be OK with either setup.
If I go the manual route, I would need to source a suitable manual gearbox, bellhousing, flywheel, clutch pack, and perhaps an adaptor plate. The standard gearbox can’t be used for the conversion, it would not handle the power.
If I use the 5-spd automatic, I think I would need more electronic controllers. I would need to source an automatic shifter, and since the 5-spd autobox makes use of a digital pulse for speed sensing, how does one get the cable operated speedometer working?

Regards

[zahistorics]

I have read that the Hi-Lux manual gearbox bolts directly to the 1UZ.

I suggest you ask the engine importers (ask more than one), they must have answered the same questions a hundred times.

[madrx]

I am busy looking into a lexus conversion at the moment and still have to deside on wich car to use,either Hilux,Mazda or Isuzu.The hilux gearbox is not a bolt on at all,you will either need an adaptor and modify the auto bellhousing or go with a complete new bellhousing conversion.the standard ECU can easily be wired in as long as it is non VVT as the later model has built in immobiliser system.Standard Ecu you are limited to tuning if you later want to upgrade to maybe turbo or supercharger.Spitronics do an auto ECU that is tuneable and also shifters,etc.Try and contact the guys at lexusv8conversions.co.za they have an adapter for the Mitsi gearbox and seem to do a lot of different conversions.Just remember that you starting off with a diesel and converting to petrol so fuelpumps and all that add to the cost,I am looking to start with a petrol EFI base as the cost will be less.Cheers

[IndianaJones]

If I go the manual gearbox route, I’ll probably make use of a W58 gearbox, custom bellhousing and flywheels are available from suppliers in SA. I can’t make use of my Mitsi gearbox, it is a R5M21, I would need a R5M31 gearbox of a Mitsi 2.8TDi or V6, and an adaptor plate. But I think, cost wise, in the end it, it will be more expensive than the auto route.

I will not be going forced induction later on, so no need for that level of tuneability. The standard ECU will serve my needs, I’m just not sure if it can be adapted to suit the overall final drive ratio of the Mitsi, versus that of the car it comes from (LS400). Whether the shift points will occur at the correct speeds, speed limiter cut off, and so forth. The Lexus LS400 has a diff ratio of 3.27:1 and make use of 225/60R16 tyres, whereas the Colt uses a 4.636 ratio diff and 215/75R15 tyres, I can swop to 245/75R15 to help the overall ratio. I suppose you need a slightly lower ratio in a ute/bakkie than a passenger car, to lug loads around, but how much? And with the autobox, I’m still left with how to run the cable operated speedo?

I’m aware of the fuel system changes, and it’s OK, I think I would have changed to new or better quality fuel filter and pump in either scenario. Apparently you need to make use of 4bar items, does the regular petrol EFI bakkie/ute make use of the same pressure?

Some have suggested, I just buy a half cut, and use the standard ECU and autobox, and all associated parts…

[madrx]

Here in Australia I am just going to buy a complete running LS400 or a Toyota Soarer and use what I need and scrap the rest.I can pic up running cars for anything from about $800.There will be a way around the speedo issue,will sort that out when the time comes.The diff ratio could be an issue depending on what the intended use will be for and tyre size will change the ratio,the aftermarket auto ECU is programable for shifting or it will have to be manually shifted.If you use a half cut you could maybe use the Toyota cluster with speed and revcounter and modify the dash.The wiring could become a nightmare to sort out though and you will have to get a auto sparky who knows what to do.For the fuel system you can try and get a Colt v6 intank fuelpump,it should fit straight in the diesel tank as the tanks are normally the same,to get more pressure you can upgrade the intank pump with an aftermarket one but the pressure should be fine to run the engine.

Cost wise you would probably be better with auto,but will still need a shifter and the driveshaft will need to be modified as well as the output shaft on the auto as they run this big rubber donut type coupling ,I think the guys from lexusv8conversions have the adapters also.

[Donovan Smith]

a Friend of mine did the Lexus engine swap on his Jeep Cherokee with the Lexus auto box and Spitronic management, it worked well. The Spitronic system was a problem to get right but once sorted it was a nice vehicle. The gearbox got destroyed on a dyno and he replaced it with the Toyota manual box. He did not like it, he rarely drive the car now.

[IndianaJones]

The gearbox got destroyed on a dyno...

How?

replaced it with the Toyota manual box. He did not like it...

Why?

[Donovan Smith]

The gearbox got destroyed on a dyno...

How?

replaced it with the Toyota manual box. He did not like it...

Why?

He told me that the shifter was pushed into park, tailpiece on the box broke off and bent the prop shaft. That gave the Jeep a good beating underneath. I am not sure what he does not like I will give him a call and get the details

[IndianaJones]

Thanks for the feedback thus far. I’ve now called just about everyone I can think of, to get all the facts about V8 Lexus conversions. After some deliberation, I can conclude that there are mixed feelings, about how to approach such a conversion. The following, is only my personal views, at this point in time.

The safest route to a reliable conversion, seems to still be the non-VVTi engine with its 4-speed autobox. A lot of people have personal experience with these engines, and the general consensus are that they are built tougher, than the later engines. (Should one read, less complicated?)
People seem to be divided as to whether the simpler spark system of the non-VVTi is better, or the distributor-less coil pack system of the VVTi motors.

Info are less forthcoming when you research the VVTi conversions, most sources seem to be in agreement that Spitronics has a hard time controlling the 5-speed automatic gearbox used in conjunction with these engines, people mostly complain about hard gear changes. A few also state the VVTi management is less than ideal. The aftermarket management systems that can control it, apparently cost in the region of R30000.

But then, more than half of the people I’ve spoken to seems to favour the Spitronics management, and be against usage of the pre-wired original ECU management. Could this be because they are more familiar with Spitronics? As the reason for it, some state poor back-up from OE ECU suppliers, some saying that since less sensors are fitted to the “converted” vehicle, the OE ECU therefore needs to be “fooled” into working, and that creates problems. One source even stated a power gain of 20kW is commonplace, by using Spitronics.

Since I would like to make use of a newer VVTi engine, and like the ratios of the 5-speed auto, my only option then seem to be the OE ECU setup, I hope I will not regret it.

If ones opts to use a manual gearbox, decisions would change a bit. A decent flywheel and bellhousing go for anything from R4400 to R5500. Apparently you need at least a 260mm clutch, unless you use a twin or triple plate clutch or the conversion is in a light vehicle. That adds another R3200-3500 to the conversion. And in my case I would have to still buy another gearbox, generally a suitable gearbox sells at around R7000-7500. If I had a bigger budget, I would have gone this route, although more expensive, I feel that it is somehow less complicated, less electronics at least to go wrong.

I would add that, I think, if I opted for a manual gearbox or used the non-VVTi engine and 4-speed, I would’ve made use of a Spitronics system.

[IndianaJones]

OK, so one times 4.3L 3UZ VVTi Lexus V8 and 5-spd auto is bought and paid for. Awaiting arrival from JHB.
I mostly went to the 3UZ, over the 1UZ VVTi, because it comes with a rear sump, which seems would be an easier fit for the Colt’s engine compartment.

Not sure how long this project will take to complete, but besides having to figure out the speedo setup, I am also contemplating a change to the differential ratio.

The 3UZ engines’ torque peak is at 3500 RPM, and power peak at 5600 RPM.
The Lexus LS430 sedan ran a 3.27:1 differential, with 225/55R17 tyres, and weighs in at 1871kg.
In top gear (0.75:1), the 4.3L engine would have done 2301RPM at 120km/h.

The Colt has a 4.636:1 differential, running 225/75R15 tyres, and weigh around 1650kg.
Theoretically, the engine will be doing 3078 RPM, at 120km/h in top gear.

Now almost everyone tells me, the Lexus engines are a multivalve design, and favours higher revs, and had this Colt been a 4x4, I might have accepted it.
But this is a 4x2, all in it will be lighter than the LS430, it will almost never be lugging around off road at crawling pace for extended periods, it will probably be driven without load 90% of the time, and I don’t tow very often. I’m sure the current ratio will give me awesome acceleration/pulling power, but I feel it is unnecessary.
One also have to take into account that when reviewing Lexus conversions, most people are familiar with the non-VVTi 4.0 and it’s 4-speed auto box, that has a 2.531:1 ratio first gear, and would favour a low ratio (numerically high) diff for easy take off. But the 5-speed autobox has a much lower first gear of 3.36:1. To curb fuel consumption, by lowering the revolutions at cruising speed, I’m seriously thinking of going to a higher ratio (numerically lower) diff, and/or going to a slightly higher profile tyre (perhaps a 245/75R15). With Mitsubishi differentials, I think I’m limited to choosing between 3.917:1, 4.111:1, 4.30:1 and 4.555:1 ratios.

My current tyre profile, and the 4.111 diff ratio will get me to 2730 RPM @ 120km/h in top, even with the 3.917 ratio, at 2601RPM it would still be higher than the car, but leaving room for pulling ability, in workhorse situations, and the higher aerodynamic drag of a pick-up.

Any advice? Does my assumptions or concerns make sense?