1UZ Coil-on-plug conversion

[Sciflyer]

There doesnt seem to be much info around on how to do this although no doubt plenty of people have done it i thought id put up some notes on how im doing it

I dont know if there is any performance benefit but if there is there wouldnt be much in it, its mainly to greatly simplfy and neaten up the existing ignition setup, particularly if you have a top-mount supercharger or other modified engine

What you get rid of with CoP

2x ignitors
2x coils
2x distributors
plug leads and all the plastic trays that hold them
plastic cam/belt covers (if you want)

What you need for a CoP setup

8x CoP units
Aftermarket ECU (Factory ECU is effectively 2 channel, you need either 4 channel for wasted spark or 8 channel for fully sequential operation)

There are a number of Toyota and non-Toyota CoPs people have used, it comes down to the usual issues like cost, availability, ease of fitting, etc

You also need to factor in whether you need CoPs with in-built ignitors or not, as with many (most?) ECUs you cannot directly connect them unless they have an ignitor

I will be running an Adaptronic ECU and CoPs with built-in ignitors in wasted spark mode (4 channels with each channel firing two plugs) so in comparision to the stock ignition layout it will go like this

ECU>CoP>plugs

By comparison the stock system goes like this
ECU>Ignitors>coils>dizzys>plug leads>plugs

The CoPs i have chosen are from the 2AZ-FE Camry/RAV 4 engine part no. 90919-02244




These have been used before on UZs (JZK25 ) because

* They are close to the right size and are reasonably easy to fit (Minor mods and they bolt directly onto the UZ cam cover using existing holes)
* Easy to get
* Look factory once installed
* Have built-in ignitors

Cons-

* They arent cheap. New ones will set you back between a few and several hundred dollars for a set of 8, 2nd hand/ebay will still end up being a couple of hundred
* They still need a bit of modding to fit
* They have a wierd plug engagement (more on that later)

I only decided to go ahead and do this after i sourced a set of these for $15 each so in true Top Gear style i thought "how hard can it be?"...

First thing when you get them is they look like they will be a perfect fit down the UZ plug tubes - theyre not.

The two plastic ribs have to go, then reducing the diameter of the body a tiny bit will see them slide right in. If you had a lathe or something this would be easy but i didnt, so the ribs were ground off on a grinder, then 5 mins in the vice with a strip of sandpaper was enough (we are talking about removing probably the thickness of a piece of paper, so little needs to be removed i doubt it would affect the insulation at all)



The CoPs after sanding down. The rubber seal at the top has also been taken off and the two plastic bits at the top of the shaft that hold it have been ground off. It is important that the CoP goes as far into the UZ plug tube as possible. The spark plug boots have been also been removed in this pic, which leads me to the next mod necessary...

[Sciflyer]

These CoPs have a weird plug engagement in that they dont use a normal clip, just a spring that presses on the top of the plug

Yes this is a bit ghey. The other thing is that the UZ tube depth to the top of the spark plug is about 5mm more than what it must be on a 2AZ, the result is that when you fit one the spring is barely contacting the spark plug - not good. So this needs to be sorted. The plug boot comes off (as above) and the spring can be seen, this is just a press fit into the end of the unit and pulls out easily.

Options are to fit a longer spring or stretch the existing one. I buggered about for a while with other springs that didnt quite fit, in the end i ended up just stretching the existing spring, in the above pic you can see one i have stretched. Time will tell if this provides a good enough contact or not.

Once the spring issue is sorted and the plug boot back on the rubber seal can be fitted, this actually fits against the cam cover better upside down and stretched around the "disc" part of the CoP as can kind of be seen here



I think this will give a pretty decent seal against water and shit ingress, unless you are regularly hosing your engine bay/driving through rivers

[Sciflyer]

What you can also see there is the CoPs line up exactly with the existing bolt holes on the UZ cam covers - win!



Well, all except for the front one which doesnt have a mounting hole, so a simple short bracket needs to be made to mount it via the bolt hole near by

[Sciflyer]

If you really want to retain the UZ plastic cam cover err... covers, these would probably be the only CoPs to use, as it is you still need to do a little trimming of the covers to make them fit, then they do so reasonably well.



You would need to be wary of heat buildup though as the covers arent vented... this may or may not shorten the life of the CoPs? Some say it will, some say it wont, who knows...

[RA35GT]

Nice work dood!

[jzk25]

I had trouble with the 2AZ coil on the 1UZ. I ended up replacing them with subaru coil packs and leads. The problems were more to do with the vehicles usage(4wd hilux being raped up the beach/in creeks/mudholes/etc) and once a small amount of water got down the tube the coils just blew holes in themselves. Leads don't really suffer from this and are cheap to replace if they do.
You don't really need to worry about this on a normal usage car.

The other problem was the tube depth as you have found. I also stretched the springs but it wasn't good enough and there was evidence of lots of arcing between coil and plug. Have a rethink on this prob and all will be good.

[Sciflyer]

Thanks Al, in that case i'll keep a close eye on the springs, i might have another go with the other ones i have, or maybe rethink a better connection altogether

[AL510]

There was a thread on lextreme where the op found some little extender nuts that went under the screw on nut on top of the plug to effectively lengthen the spark plug.You might be able to find something similar.

Cheers, Al.

[jzk25]

Sounds like a good plan Al.

[wagonist]

Did you put the rubber boot back onto the bottom? This is what makes the positive locating contact with the spark plug & stops it from moving around (don't forget it's really only held in with one bolt).

I'd also strongly suggest you change your retaining screws to bolts, or at least the allen key heads. Whilst little torque is needed to hold down the plug, a mate who had used screws to hold his down had trouble with the screw head rounding off after 100 000km of heat cycling the engine

What's so weird about the spring? All you need is a metal contact that ensures positive contact with the plug.

Does the 1UZ have factory camshaft sensors? I noticed this was a big difference in my 3S head with CoP vs the earlier GT4 engines which have a distributor.

[twentyEight]

These measurements I took of the 1ZZ/2ZZ ones might be handy for anyone else wanting to do this for the 1UZ.

[Sciflyer]

There was a thread on lextreme where the op found some little extender nuts that went under the screw on nut on top of the plug to effectively lengthen the spark plug.You might be able to find something similar.

Cheers, Al.

Yep i know what you mean, i didnt investigate this option as the plugs i had were a fixed top that didnt unscrew. Could be a simple fix with the right plugs though

Did you put the rubber boot back onto the bottom?

Yes Its not so much the physical locating of the plug in the end of the CoP unit as the rubber boot does that fine, its the contact/pressure of the spring on the plug end to make a good *electrical* contact

I'd also strongly suggest you change your retaining screws to bolts, or at least the allen key heads. Whilst little torque is needed to hold down the plug, a mate who had used screws to hold his down had trouble with the screw head rounding off after 100 000km of heat cycling the engine

I was certain in my bucket of Toyota nuts and bolts there were 8 suitable ones but do you think i could find them?

What's so weird about the spring? All you need is a metal contact that ensures positive contact with the plug.

Because of the extra depth of the UZ tube its not a very positive contact, stretching the spring might make it long enough but may not provide enough pressure to make a good contact

Does the 1UZ have factory camshaft sensors?

yup

Sciflyer, it might be of note that the 1st COP you have pictured in your first post is different to the RAV4 ones. The rubber end is the biggest giveaway. It looks more like a 1ZZ/2ZZ one but it has the mounting ear at the back flat section, rather than the back corner. (Might be from a 1NZ, although I think they're identical to the 1ZZ/2ZZ ones.)

These measurements I took of the 1ZZ/2ZZ ones might be handy for anyone else wanting to do this for the 1UZ.

Those ones look similar to the 1MZ units i also tried (they were bigger but didnt have integral ignitors). The ones im using are definitely off a RAV4 because i pulled them off the car myself

Its likely that there were more than one type of CoP used over the years, hence me referencing the part number

[turbo ke20]

why not use 2uz-fe ones?
the v8 engine that comes out in the 100 series landcruiser.

[Sciflyer]

They wont fit on the cam cover without chopping the mounting off, and then you have to find some other way of securing them. They have been used though

[Sciflyer]

Connectors:

I didnt have the factory plugs for these so needed to find connectors for wiring them up. Hunted around at work for bits and found standard 3.2mm brass crimp connectors (the type commonly found in telecom phone plugs) are a perfect fit - picked up a couple of packs for ~$6