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320i to 3uz conversion
11-08-2018, 05:49 AM
Post: #1
320i to 3uz conversion
Hello all bmmaniacs .
I recently started playing with the idea of changing my stock n46 engine and box for a 3uz and five speed auto box.
As you can imagine I do have a lot of questions regarding the engine swap.
As I am very new to this site and did not have time to read thru all the threats I would like to know if anyone here has done the conversion and if so what advice and pointers can you give me?
A little history of my car.
It is a 2006 320i.
It has 276000 kilos on the dial.
A while ago I noticed that on my way to drop the kids at school as I am driving up an incline I had to change down from sixth gear to fifth gear.
Then after a while I noticed that I had to gear down to fourth just to maintain speed.
Previously I could just fly up the incline without changing whilst maintaining momentum.
This gradual loss of power prompted me to pull the engine and do a complete overhaul.
I changed everything from timing chain and guides to valvetronic gears to solenoids.
Not even sure if that was necessary .
Rings ,bearings and gaskets was also replaced.
I am happy to report that The engine is even better now than when I bought the car with 145000km on the clock.
However I do wish for a more powerful motor and after researching the net for a while I came across a relatively affordable option in the guise of the 3uz engine and box.
I am sure that I will be crucified by the purists amongst you, however the reliability and affordability of the 3uz combined with the amount of power that it packs is the driving force behind this.
Has anybody done it.
What troubles could I encounter?
Please let me know where to go look for more reading on this exhange
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11-08-2018, 07:07 AM
Post: #2
RE: 320i to 3uz conversion
Just test drive one that has been done already and realise why they are sold shortly after completion. You lose a ton of features and creature comforts in the conversion, not to mention the disgustinly poor hack job they do to fit the engine. You are better off buying a e90 with a bigger engine and retaining the value of the car.
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11-08-2018, 07:57 AM
Post: #3
RE: 320i to 3uz conversion
As has been stated
Do not do it.

The truth is incontrovertible, malice may attack it, ignorance may deride it, but in the end, there it is. ~ Winston Churchill


peterkarvelas@gmail.com
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12-08-2018, 11:25 AM
Post: #4
320i to 3uz conversion
DO IT!!!

I have a 1 series with 1uz. A proper conversion can cost you 50-60k. Try look for the 6 speed auto version as the economy is really nice and parts are cheap

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shark111
12-08-2018, 09:07 PM
Post: #5
RE: 320i to 3uz conversion
If you do it, just make sure you do it properly. A crappy swap will ruin everything.

Just remember, if you go ahead and do it, I don't think this is gonna be your daily anymore...
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12-08-2018, 09:33 PM (This post was last modified: 12-08-2018 09:40 PM by Captain_Stealth.)
Post: #6
320i to 3uz conversion
(12-08-2018 09:07 PM)Jeremy.d Wrote:  If you do it, just make sure you do it properly. A crappy swap will ruin everything.

Just remember, if you go ahead and do it, I don't think this is gonna be your daily anymore...

3uz with 6 speed auto actually get really good gas mileage. The motors are cheap. Parts are way cheaper than bmw ones. 224kw and 441nm will be really nice too. These motors are popular cause they are over engineered and super reliable


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[Image: 6c5ac910f77c0a0ffc55fd1c30ed859f.png]

Best bet is to join the Lexus v8 Facebook pages and ask for the best person to do your conversion get some references. And decide from there


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13-08-2018, 01:45 AM
Post: #7
RE: 320i to 3uz conversion
Wow thanks guys.
Admittedly I was sold on the idea of converting even before joining the forum.
I do have a lot more homework to do before I even consider the mechanic.
I do have these questions though.
Is the 3uz's throttle cable or electronic like the BMW?
That would relate to cruise control.
Etc function would not work on unsupported box therefore I am considering a stronger bmw box that has that function.
Does anyone know if a bmw box has been linked successfully to a 4uz?.
What other functions could I possibly be overlooking that I would have to consider?
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13-08-2018, 09:08 AM
Post: #8
320i to 3uz conversion
Well if you keeping it auto the 6speed auto tgat comes with the motor is fine. If you going manual then that’s a different story. Only the 3uz is the electronic pedal. The rest is cable. If you plan on boosting it look for the pre 93 motors as they have thicker rods. I have the non vvti as I like simplicity and they are better for a turbo build. but the vvti are def better for fuel economy and have more power at lower rpms due to vvti system and more power overall. Btw there is no 4uz. Only 1uz. 2uz. And 3uz. The 1uz and 2 uz were the only 2 motors that came in both non vvti and vvti


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14-08-2018, 09:41 PM
Post: #9
RE: 320i to 3uz conversion
1. Your biggest problem will be to make the bmw dash work.
2. Are you going to remove the bmw ECU? That alone will create a few more problems. EWS for one. Are you going to use the standard lexus ECU or Spitronics (they can do 6 speed now).
3. To do a neat reliable conversion it will cost a lot but it will be way more fun and reliable than a bmw motor.
4. A lot of people that does not know what they are doing will have heating issues afterwards. Remember that a lot of these engines were sold in really cold counties. They run hot thermostats. Behind the thermostat is a hole that needs to get a Welsh plug. That hole constantly put hot water back in the heads, the hole alone is bigger that the hose to the radiator. The only time you drill a 8mm hole in there is if you are going to use the standard heater system again. Use a Nissan vg30 76 degree thermostat, you need to take a few mm off the base plate.
5. The 3uz is actually less reliable than the older motors due to the bigger bores which means thinner walls for boost/longevity.
6. The older engines with a good port and polish, spitronics and good exhaust will keep you smiling for a long time. I have a friend who does these conversions for a living. He takes 1kg of shavings out between the 2 heads when he port them.
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