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conversion for 4kq to mc turbo(very long)

I am going to try to get into as technical of post that I can regarding my 4kq 
mc conversion project.  This project is not for the faint of heart.  It does 
require some cutting of body parts (and I don't only mean the car), 
fabrication of many custom brackets,  Bentleys for a 4kq and 5kt, and time.  
In my case 5 months but I could see it done in 2 knowing what I know now.  I 
did scrap the ac as it needed repair and is some weight.  I have not got an 
intercooler yet but am planning on having a custom one built for the grill 
area.  I have been told not to have one in front of the radiator.  I have not 
yet completely figured out an oil cooler yet but am planning on an aftermarket 
with custom hoses.  And I am also planning a rebuilt radiator although so far 
no cooling problems.  Trip computer is gone and probably not going to happen 
in my lifetime.  For brakes I am going to wait and see.  I have never had 
brake problems with the 4kq brakes as long as I keep the fluid fresh.  If I 
find I need more I will probably do the g-60 set up.

I have driven it on the track and the temps were all good and the car ran 
beautifully.  I have clocked a 0-60 time of 6 seconds with just spring 
controlled wastegate.  I am tracing some minor electrical maladies but 
otherwise the car has been great.  So here is the step by step process that I 
went through.  I am leaving out a lot of what we did as there is just too much 
to remember but it is fairly complete.  I really suggest that you replace 
anything that needs replacing at this time.  While the car is down and you are 
knee deep in this project you will want to do anything that is easier while 
the car is down.  For example any bushings that are needed should be done.  
Remember you are going to have a few extra horses that will put extra stresses 
on most everything.

Step 1:  Find a large water body just deep enough to drive your car in up to 
the airbox.  Run the car in said water until engine seizes.  This step can be 
skipped if single however is required if married.  This engine killing 
exercise ensures the proper excuse to undertake this large and expensive task. 
 I did not completely succeed in this task though as the motor was not damaged 
by this process.  Solution :  Deeper water.

Step 2:  If you do not have access to garage, find some poor sucker to let you 
use his.  Tell him it should only take 2-3 months and you will spend every 
evening there till it is done.  This is of course a lie but he won't know till 
the end anyway and by then he has given up all hope of ever getting a clean 
garage.  VERY IMPORTANT.  Make sure your poor sucker has plenty of good tools. 
 Not just basic hand tools but drills, jig saws, torch, press, many 
jackstands, good quality jack, and most important, most crucial, liquid 
mechanic.  Do not however pay anything for the use of this garrage as it will 
set a bad precedence.  

Step 3: Find suitable 5kt or other 86+ turbo motor preferably in car.  The 
reason it is good to get it in a car is because you can see how everything fit 
as well as being able to sell parts to recoup some of your investment.  The 
best car is a 5000t because it uses a lot of the same parts that a 4kq uses so 
you can scavenge.  86+ are good because it is the water cooled turbo and more 
advanced computer.  I bought the front half of an 86 5kt for $860 with about 
115k miles.  I figured I can recoup about half of the cost of the motor.  

Step 4: Stare at the cars and wonder what the hell you are going to do.  After 
this, maybe take some pictures for posterity and some close-ups so that if you 
really get confused about where this or that was.  Then start marking ALL the 
wires and hoses and removing them from their respective places.  Since you 
will not need the radiator that should be where you start.  You might also 
might want to remove the air conditioning system since you will not be needing 
it and it has good $ value for used stuff.  Also mark tdc in several spots.  I 
found the mark on the crankshaft pulley to be incorrect on my donor car.  Mark 
pulley and cam sprocket so that you will know how to install the cam belt 
without the flywheel.  

Step 5: Remove the dash of the donor car.  It makes it much easier to get the 
wiring harness out of the car and you probably want to sell some parts under 
it anyway.  This is actually a pretty difficult job if you don't want to break 
anything.  Remove all harnesses as the connectors will come in handy later.  
You also never know what fellow q heads may want.  You may want to mark where 
EVERYTHING came from so if you do not know what it is later you will at least 
know where it was. Be careful with the transmission linkage and all the 
quattro vacuum lines
> on top of the transmission. I suggest removing harnesses with the engine in 
the car as this will assure that you did not forget to disconnect something.  

Step 6:  Remove engine.  Nuff said.

Step 7:  I chose to do a poor mans rebuild.  I did all gaskets, water pump, 
timing belt, head job(no, not what your thinking), injectors serviced, tune 
up, and many other little things I chose not to remember.  Please do not buy 
Audi manifold studs.  I broke 3 of these pieces of crap while trying to torque 
to the proper specs.  Try to find something that actually has some strength.  
We thoroughly cleaned the motor, painted all parts that needed it, and 
replaced any suspect nuts or bolts.  If your donor car is an automatic than 
you will need to get a flywheel and clutch.  These should be from a 5ktq.  You 
will also need to remove the automatic pilot bearing.  You will need a slide 
hammer.  VERY IMPORTANT:   Keep all screws, brackets, wire ties, and anything 
else, especially if it looks useless because most likely it will turn into 
your best friend later on.  Keep the cutting dikes in the box at this point.  
Do not cut anything.

Step 8: Once donor engine is ready prepare your car for engine removal.  
Remove rf tie rod as it will have to be either bent or you will have to buy a 
ur-q rod.   If you buy the ur-q rod you will have to modify the 4kq strut to 
make it fit.  I chose to send mine to 2 Bennett in CA to have them bend it.   
It is only a slight bend and they have done it for years with no problems. I 
suggest marking everything also since you will use some of the 4kq wiring.  Do 
not cut anything.  Assume nothing.   I suggest removing the interior and dash 
although this is not required.  I removed it so I did not spend a month on my 
back.  It is not that hard on  the 4kq and goes fairly quickly.  This also 
gave me a chance to rewire some things that I have always wanted to do.  For 
those of you that hate the cool air "feature" of the center vent this also 
gives you the opportunity to fix it.  Huw Powell has an excellent post on this 
procedure in the archives.  I like the cool center vent so I left mine alone.  
Before removing any wires mark them because you do not want to spend a week 
trying to identify basic 4k components.  

Step 9:  Remove engine/transmission.  It is easiest to drop the engine out the 
bottom.  Just remove the subframe and viola the engine is ready to drop.  
Remove all linkages, hoses, fuel lines and anything else that could get 
damaged.  Do this slowly as you will likely forget something and you will 
prefer to take your time.

Step 10: Clean, clean, clean.  10-15 years of road grime is accumulated in 
every nook and cranny.  Hopefully you will not be removing the engine anytime 
soon so why accumulate more.  It also makes putting the new motor in somewhat 
cleaner. Remove anything that might get in your way.  

Step 11: Remove battery tray.  If you get it out cleanly enough you can use 
the tray to mount the battery in the rear.  I mounted mine in the farthest 
right rear corner of the trunk down in the well.  This uses very little trunk 
room.  It also allows you to use the stock mounting bracket. This can be 
welded > in but I chose to mount it with screws at three locations. Run a 2 
ott welding wire from the trunk to the front of the car.  Use a standard 
terminal on the rear fitting and get a press on eye fitting for connecting it 
to the jumper block.  If you run it carefully, no one will ever know it was 
there.  If you were diligent when disassembling the donor than you will have 
the jumper post and can mount that where the battery was.  This is your 
connection point for the starter circuit, fuse panel power, and alternator.  
Put it about 4" to the drivers side of the strut mount. I spaced it off the 
firewall with some 1/2" spacers.  

Step 12:  Join new engine with old transmission.  This is not any different 
than the usual. I suggest replacing the shift mounts and clutch slave cylinder 
while you are there.  Replace any bolts that are self locking as suggested by 
the Bentley.  Also make sure you use a good torque wrench and torque them to 
proper specs.   It also might be a good idea to fit the mounts to the new 
engine.  Use the 4kq mounts and brackets.  You will need the alternator 
bracket from the 5kt which has the front damper on it.  I chose to use the 4kq 
alternator and mounting apparatus.  It may be easier to mount this at this 

Step 13:  I chose to put the engine before doing the wiring.  The only thing I 
would maybe do is resolve the left side harness issue before fitting the 
engine.  The right side is definitely a wait until the engine is in.  The left 
harness on the 4kq does not have some of the cooling system wiring you may 
need.  I do not have my diagrams in front of me but as I remember there were 
some issues regarding after run equipment which are not on the 4kq harness.  
You also have the multifunction sensor on that side that you may want to keep. 
 Just work on that side for now since the right side is easy and poses no such 
issues.  If you decide to use the 5kt harness you will also need some of the 
4kq stuff.  I ran them both through the firewall.  While this created a mess 
inside the car it gave me everything I could possibly need.  They will fit 
through the stock hole in the firewall.  No mods needed here.  For specific 
wiring questions please ask me specific questions as it would be hard to 
remember it all at once.  Install the left side harness before the engine is 

Step 13:  Figure out what you are going to do about the airbox.  This is a 
major PAIN IN THE ASS.  The easiest thing to do would be to get a urq airbox 
assembly and install the 5kt fuel distributor on top.  But to do this there 
are some hose routing issues and temperature things to consider.  I chose to 
use as much of the 5kt system as possible.  I cut the 4kq airbox at the bottom 
leaving about 2-3" and an open bottom.  Then mount the 5kt distributor to the 
4kq airbox top.  I then cut the inner fender away so that I could mount the 
box inside the inner fender just in front of the wheel well liner.  This 
allowed me to use the 5kt intake boot and make a steel pipe to run from that 
to the turbo intake boot.  There is a temperature issue but I resolved this 
with some aluminum tape and some good ducting.  For specifics regarding where 
to cut the inner fender email me.   Make some brackets and mount the airbox 
bottom to the frame as a permanent fixture.  Do use rubber washers to dampen 
distributor noise.  This is very difficult to do without the engine in the car 
but it is even harder with it in.  You would be wise to have this figured out 
before starting the project.  I did not.  When you get the airbox bottom set 
remove the top and set it aside for the engine install.  

Step 14:  Install engine.  If you have 2 people and a good floor jack you 
should be able to do it without a hoist.  Get the car up high on jack stands 
and set engine/transmission assembly on jack.  Roll jack under car and raise 
to install.  

Step 15: Install heatshield on rf motormount.  This will need to be 
fabricated.  Also start routing hoses.  Install radiator.  Since I used the 
stock 4kq radiator I used the 4kq lower hose with the 4kq motor flange.  For 
the upper I used a 4kq hose cut in half.  The radiator half I used the 5kt 
line with the t for the after run pump. I spliced the 2 together with a heavy 
flange.  For the main line that goes to the heater core we cut the 5kt pipe 
and put a t in to accommodate the pump.  The heater hoses stayed the same with 
just a little trim to match everything up.  I used the stock 5kt pump mount 
and cut it to mount on the fan shroud.  Just trim the hose a little as it is 
too long.  Very clean and functional.   For the downpipe with mine it fit just 
fine.  I did shim the mount up about 1/4" to gain a little extra clearance.  

Step 16: Start the wiring process. The outside stuff is pretty self 
explanatory.  As for the inside stuff it just takes patience and a good 
knowledge of how to read a wiring diagram.  The fuse boxes are identical so 
there is no need to replace the 4kq's.  It also helps to have the 5kt fuse box 
in tact for identifying posts.  Basically I replaced the fuel pump relay with 
the 5kt's and simply spliced wires into the proper posts.  Not very scientific 
but it all worked well.  I also went ahead and used a couple of the 5kt wiring 
blocks to facilitate any later modifications.  For specific information just 
post me with specific questions and I will try my best to remember.  The only 
outside stuff that can pose a problem is the after run fan and coolant pump.  
Since I kept the 4kq harness in and left the radiator circuit in tact I just 
used a relay system to run the pump whenever the fan cam on and the ignition 
is off.  And instead of the way high 130c temp switch the 5kt uses to run the 
after run I put a 170f thermodisc on the wastegate heat shield.  It runs only 
when the car is really hot and then shuts off in about 3-5 minutes.  Even if 
it gets really hot the stock 4kq after run relay has a 10 minute timer.  Use 
the same wires the 4kq used for its after run switch.  For a knock sensor 
light I simply used a seat belt warning bulb socket to wire it in.  Then I 
snapped that into the check engine light.  For the injector cooling fan 
everything stayed with the stock 5kt system.  I mounted the fan in front of 
the radiator just below the headlight.  I then ran a hose from that to the 
plenum.  For the air intake sensor we drilled a hole in the boss on the top of 
the intake and installed it there.  The coil mounted right next to where the 
battery box was.  You can use the existing bolts that are there.  To get extra 
room under that I had to remove one of the 3 plugs that mounts with the coil.  
I tried to use the 4kq oil pressure control unit but for some reason could not 
get anything except the low pressure switch to work.  I will be running an oil 
pressure gauge so that will not be that important anyway.

Step 17:  Have the custom hoses made or weld the intake tubes yourself.  Then 
the exhaust connection will have to be addressed.  I simply had a connector 
pipe made from the 5kt downpipe just below the y to the 4kq cat.   

Step 18: Once the plumbing is done install some type of boost gauge. I used an 
Autometer on the a pillar just above the lf speaker.  Then you need to address 
the throttle cable.  I used a 5ktq cable.  It is really not the best cable for 
this.   It is a little long and this cable is not compatible with the 4kq 
pedal.  I had to fabricate a ring and crimp on a ball for the engine 
compartment.  Just good old fashioned fabrication. If > you can get a throttle 
mechanism from a 5 speed car you may be able to hook it > up like stock at the 
engine side. So far it works great.  

Step 19:  Start the car.  Notice I did not say to put the dash in.  This is so 
you can trace down any electrical problems easier than standing on your head.  
Make sure all your timing marks line up and apply power.  If you did 
everything right  it should start quickly.  If not it won't.  Run it and watch 
closely for any smoke or hot spots.  Run the car and see if all the gauges 
work and if all the fans come on.   Change the oil frequently for the 1st few 
changes as you want to flush that engine out.

Step 20:  Reinstall interior and trace down any niggling problems.  Without 
the ac in it was easy to put the computer in that space. Keep an eye on > 
temperatures, I added some reflective foil to the airbox and the bottom side 
of > the intake pipe to try and keep these as cool as possible. I also added a 
couple > of scoops and hoses in the airstream just under the horn to bring air 
to the
> turbo and the engine mount. I used the intake pipe from the 4kq. The one 
inside > the fender.

That was easy now just do it.  It really is a fun project and will yield 
fabulous performance.  But this warning.  If you are going to do it right do 
not expect it to take less than 2 months (assuming you have a life) and do not 
underestimate the budget.  I posted mine NOT including other improvements I 
made and it was almost double what I budgeted.  
Good luck and feel free to post me any questions.
Pat Martin
864000csq turbo, 2 1/2 cat back, H&R-Boge, MC and loving it.  Drilled rotors 
stopping it. Koenig Cobra 16x7 with AVS Intermediates turning it,  K&N and 
95 subaru legacy 
Bothell, Wa

PS  I would again like to thank all that helped during the project and hope 
that the next guy who tries it gets the same sort of support.