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Z32 NA to TT Conversion information
We’ve gathered all this info over the past several
years through many turbo conversions. We have tons of TT and NA parts here to compare and
a Nissan computer system at our disposal. We receive many emails/calls asking
if we can do a conversion or can sell the parts to do it. We can do it for
around $8750 if you have a 5 sp NA,
around a $1000 more if you have an auto, because we have to change the
transmissions. We can also convert 5p to auto and vice versa for extra
cost. They are with exchange of good NA parts and involve
converting to a stock TT
with used parts.
We do recommend installing certain parts new and
upgrading certain things while we have
everything apart
for minimal extra labor costs. But that just depends on how far you want to go,
it is easy to get up to $15-$20k quickly if you want a lot of performance
parts. The only way we see fit to do the conversion is to buy a wrecked TT or front clip (which we
have quite a few of) and transfer everything into the NA being converted, buying
stuff piece by piece will take forever and become very expensive.
The majority of the differences are listed below.
ENGINE
1. The cylinder block castings and main caps are
the same. They both have oil squirters that direct
oil towards the underside of the piston, but they point at different angles.
The oil squirters on the TT direct oil straight into an off center hole
on the underside of the TT
piston, which leads to a hollow area inside the top of the TT piston. The NA squirters
direct the oil towards the middle of the underside of the piston, which has no
passages inside. They blocks have all of the same oil passages. Two passages
are plugged with a bolt on the NA
block (one on each outside face that feed the turbos
on a TT). The TT block has two oil passages
plugged inside where the oil filter bracket mounts. The NA has two small check valves
in this location. They are plugged in the TT providing more pressure so that the oil will
go through the lines to the oil cooler, which returns back to the oil pan.
There are check valves on the inside of the TT oil filter bracket where the oil filter
screws on, but none on the NA.
The purpose of these check valves is if the oil filter somehow becomes clogged
or collapses that oil will still circulate.
2. The crankshaft is the same.
3. Connecting rods ARE the same!! (Same Nissan part
#)
4. Piston rings and crankshaft bearings are the same.
5. Of course the pistons are different because of
lower compression ratio in the TT,
8.5:1 in
respect to
10.5:1 on the NA.
The internal structure of the pistons is also different, the TT have a hollow ring inside
the top that fills with oil for better cooling and a thicker dome towards the
center. Oil pumps are different. They mount the same and are the same
internally except for the spring for the pressure valve in the TT one is tighter so it
produces more needed pressure to circulate oil to the turbos
and cooler. You can actually just change the spring to the tighter one. The 94+ NA oil pumps and the replacement NA oil pumps from Nissan are
different internally to the older ones and the TTs.
They have internal gears with larger rounded teeth.
6. Oil filter bracket on a TT is different (longer)
because it has an outlet that accommodates the hose going to the oil cooler.
There is a spring loaded valve in the bracket that will not let the oil
circulate to the cooler unless there is sufficient pressure. And then there are
the spring loaded ball check valves that let oil bypass the oil filter if there
is a problem, these are in the block on an NA. Oil filters are all the same.
7. Cams, lifters, locks, retainers, and valve
springs ARE the same (90-93)(same Nissan Part #) The Auto TT has different intake cams
(lower lift) but the intake cams on the 5 speed TT, NA,
and auto NA are the
same. The different intake cams in the auto TT along with the slightly smaller exhaust
housings on the turbos results in 20 less HP in the
auto TT (it was
detuned to help the transmission last longer). All the exhaust cams are the
same. The 94-95 cams were different than the 90-93 but just like the earlier
ones they are all the same except for the intake cams on the auto TT. The 96 cams were ALL the
same.
8. The valves are all the same size. But the
exhaust valves on a TT
are made from a stronger alloy (Inconnel)
9. The heads are different between NA and TT. The castings are almost
the same but not quite. The intake runners are of a different design in the
turbo heads. The castings offer a more open port for the TT. We have used them
interchangeably before without any problems, just probably results in the loss
of some power, when using NA
heads on a TT. It is
significant enough that it would take extensive porting to get NA heads up to TT specs. We use different
spark plugs on the NA and
TT but we see them
used backwards and every way in between a lot. The TT ones we use are NGK PFR6B-11B which are
slightly longer that the NA
PFR6G-11. The longer plug is “colder” which helps with preventing detonation at
higher boost levels.
10. The oil pan is different because the TT one has 2 tubes protruding
on the sides where the oil return hoses for the turbos
mount and another one for the hose returning from the oil cooler.
11. The turbo engine obviously has a few different
accessories and systems to accommodate the turbos.
The exhaust manifolds on the TT
are much shorter than the NA
ones, which go all the way down and tie into the exhaust section including the
catalytic converters. The turbos are oil lubricated
and water cooled. So there are oil and water, supply and return lines
everywhere on a TT
motor.
12. The throttle bodies are the same size but the
passenger side one is different on a TT simply because one of the water lines attached to the
bottom of it has a junction in it to feed water to one turbo. But we usually do
away with all that nonsense with the water lines under the plenum running to
the TB’s in our warm climate. We just run water to and from the metal hoses on
the back of the motor going to and from the heater core. Nissan added all the
water lines under the plenum going through the TB’s to warm the intake air
charge in cold climates. I think they designed it for the NA and just didn’t change it
for the TT. You do
not need this on a TT.
You intercool your air to cool it down after it leaves the turbo, why try to
heat it back up. Remove all the nonsense under the plenum. It makes life much
easier.
13. The upper and lower intake manifolds (plenums)
are the same TT and NA 90-92. Newer ones are
different from the earlier ones. They made the change to the new style
injectors, lower plenum, and the intake port on the heads in 93 for the NA but not till 95 on the TT. So the lower plenum and
heads on a 93 -94 NA
are different than those on a 93-94 TT. The upper plenums changed just a small bit in 94 when
the angle that the flange of one of the EGR tubes bolts on to the plenum
rotated about 30 degrees. Just enough stuff to make interchanges a pain.
14. Motor mounts are the same, but I have a secret
on that. I guess I’ll let it out if you’ve read this far although I have made
some money because of it. The convertible motor mounts are the same but
substantially cheaper for some reason. Motor mounts are broken into almost
every time we pull a motor, so we go through lot of them and have saved $.
15. Head gaskets have a different part #s but
appear to be the same we use all TT
ones because they are less expensive also.
16. Water pump, PCV valves, exhaust gaskets, intake
gaskets, plenum gaskets, valve cover
gaskets,
seals, Timing belt, thermostat all the same.
ELECTRICAL
1. Nissan claimed the TT coil packs were different a couple years ago
and charged a lot more for them. I checked them and found that they were the
same and now Nissan lists them as the same. I guess they got caught on that
one.
2. Of course the ECU is different, along with a
different transmission computer on the automatics, other than that there are no
control units that must be changed. We can upgrade a NA ECU to upgraded TT specs for $250 which is
usually a better idea than buying a TT ECU then paying to have it upgraded later.
3. The main engine (EFI) harness is different also,
but a NA harness
will work in an TT, you just will not have the connections for
the boost control solenoids which you don’t need anyway if you have a boost
controller. I don’t recommend wasting your time with the conversion if you are
too cheap to buy a boost controller. If necessary we have an easy way to remove
the engine harness without removing hardly anything inside the car. There is an
aluminum bracket bolted right inside the firewall that makes the engine harness
difficult to change. The bracket is bolted in behind the heater core and AC
evaporator so it is hard to remove from the inside. We take a pneumatic
reciprocating saw and cut the passenger side of the bracket into from inside
the engine bay and then with some prying the bracket pivots around on one bolt
and moves out of your way.
4. If converting NA --> TT, I would leave the interior harness and gauge
cluster alone. They will work with the TT setup. Get a stand alone boost gauge because the stock
one sux. You would be insane to add the HICAS system
or stock electronic adjustable suspension to a NA so you will not need the TT interior harness. I would
leave all major wiring harnesses alone when doing a conversion.
5. MAF, PTU, TPS, IAA, AIV, EGR, O2 sensors,
Detonation sensor, Coolant temperature sensor are all the same.
6. The electrical AC Condenser fan is different on
a TT. The motor has
three wires (2 speed)
going to it as opposed to two
(one speed) on the NA.
But you can get by with the NA
one on a conversion. The mechanical fan is the same but the fan clutch is
different. The TTs have a yellow dot on the front and
are tighter than the NAs with an orange dot.
7. The starters are all the same.
OTHER DRIVETRAIN
1. If converting most people would keep the NA rear differential, because
a lot of TT owners
switch to it anyway. It has a
lower ratio (4.08 compared to 3.67) that will decrease your top speed but
enhance take off. Plus converting differentials is not easy. You must change
the entire rear subframe because the differentials
mount completely different. You would also have to change the halfshafts, which have a six bolt flange on the TT where they bolt to the
diff (compared to five on the NA)
and the ends are larger diameter where the splines go
into the hubs. So the hubs are different. Since the TT has the Hicas tie rods
in the rear there is an additional suspension arm on the NA to make up for the lack of
support there. Because of the way these bolt up differently to the knuckle, the
knuckles are different also, unless you press a ball joint out and somehow
press a hollow bushing back in.
2. As long as you keep the NA rear diff, the NA driveshaft will work. The TT driveshaft will not work
with an NA diff or
vice versa. The TT
driveshaft has a CV joint at the end where it bolts to the differential and
larger U-joints. There are 6 different driveshafts
for the Z: TT auto
and 5sp, 2s NA auto
and 5sp, and 4s NA
auto and 5 sp. The stock driveshaft is a 2 piece so you can mix and match
combinations and usually come up with something that will work what ever you
are trying, because they will all bolt together in the
middle. The center support bearings will work interchangeably although they are
listed differently and there is a little issue about shimming one. We buy all
new TT ones because
they are cheaper. But the best idea is probably just to go with a one piece
unit anyway. We have one piece driveshafts for any
combination in stock. They are almost half the weight of the stock driveshafts. They have replaceable U-joints (the units in
the stock shafts are almost always bad and can’t be replaced. And they offer
better torque transfer.
3. The NA
and TT have the same
5 speed transmission model #, same splines on input
and output shafts, etc. and the housings are the same except for one small
difference. The spot where the starter mounts on the bellhousing
on the TT is
machined a little differently so that the starter will properly engage the
slightly larger diameter flywheel and so that the flywheel teeth won’t scrape
the inside of the bellhousing. You can use an NA 5 speed in a TT but you just have to shim
the starter out a little with some flat washers and sometimes grind a little
out of the inside of the bellhousing so the TT flywheel will fit inside.
If trying to use a TT
trans in an NA you would either have to grind down where the starter
mounts so that it could engage the smaller NA flywheel or just use the TT flywheel, which could be
used with only a TT
clutch. The internals are the same between the NA and TT 5 sp transmissions,
although all
the 94 + models had redesigned stronger internals. I have used them nterchangeably
without problems. The automatic transmission is different for a TT, but the NA auto would still fit in
place behind the TT
engine, but probably wouldn’t last long. They are different lengths and you
would have to use the corresponding driveshaft. Both autos are geared virtually
the same but the TT
one is built for heavier duty.
4. The speed sensor gear in the transmission is
different, different size for NA
and TT because of
the different ratios in the diff. So if you are using a NA diff you need a NA speed sensor gear. The
speed sensor is different auto and 5 sp also.
5. The TT
clutch has a larger contact face, a stronger pressure plate and a slightly
larger diameter flywheel. You can use a TT flywheel in an NA by shimming out the starter but can’t use a NA flywheel in a TT without cutting down the
spot where the starter mounts to the TT transmission. You have to use a TT clutch assembly with a TT flywheel and the same with
NA because of the
way the pressure plate bolts to the flywheel. The TTs
also included a clutch booster assembly because of the stronger pressure plate.
The clutch pedal and master cylinder were different because of a vacuum
assisted clutch booster inside the firewall. The booster included two plastic
tanks for vacuum storage also, one under the driver’s fender and one under the
clutch master cylinder and a network of hoses connecting them all. Because of
the clutch booster, the clutch pedal and master cylinder are different between NA and TT but all the slave
cylinders are the same. You don’t have to add this setup when doing a
conversion (a lot of trouble) the clutch pedal will just be stiff but it’s not
unbearable in my opinion.
OTHER
1. The Radiator and AC Condenser are MUCH different.
They are much narrower on a TT
so the intercooler piping can go around each side. The front lower core support
is also different (but can be modified to work with a little cutting and
welding) because the TT
radiator and condenser mount farther down into brackets, because they are
taller to make up for the difference in width.
There are some differences in the AC lines also.
The upper radiator hose on the TT
is different but the lower one is the same. We often go to home depot and buy
some chrome drain pipe to replace the bottom section of the radiator hose which
can collapse. We just splice it in with some clamps, better that paying for the
Stillen solid hose and easier to work with when
removing/installing the radiator.
2. When swapping the NA rear diff into the TT the best option is to do away with all
the Hicas lines, solenoid, reservoir, pws pump, etc. The NA pws pump is smaller and
provides less drag on the motor. Plus the TT pump has two chambers, one for the front and
one for the rear. So if you eliminate the HICAS what do you want the fluid
pumping back there for? Like with the return fittings Stillen
supplies for their HICAS elimination bar. You also don’t want to just
disconnect all of that and still run a TT pump, because it requires lubrication in the rear
chamber provided by the fluid. So if converting you would hopefully stay with
the NA pws pump. The mounting brackets and bolts on the block for
the PWS pump are different for the TT
and NA as well as
the length of the bolt that the pump pivots on.
3. The front steering racks look and fit exactly
the same but they have different gear ratios inside providing for more turn
with less steering wheel travel in the NA which doesn’t have the rear wheels to assist. But it
isn’t something to change in a conversion.
4. The rest of the front suspension is the same,
except for shocks and springs. The TT
shocks are the 2 way adjustable units and the TT springs are more progressive, but in a
conversion I would just go with aftermarket performance units on both. The TT swaybars
are also stiffer but no big deal, just go aftermarket performance with that
also at your convenience.
5. The calipers and rotors are all the same size
except for in 90 when the NA
calipers supported a slightly thinner 26 mm widen rotor. There was not enough
cooling capacity in that rotor so all the later NAs and all TTs
had 30mm wide rotors. The calipers were all aluminum until 93 when they went to
cast iron.
6. The TT
alternator is higher output (90A vs 80A) but they are
interchangeable. I don’t think
putting a TT alternator on an NA is a bad idea.
7. The AC Compressors are the same for
corresponding year models.
8. The TT
has all of the intake/turbo/intercooler piping, intercoolers, and recirculation
valves. On an NA air
goes from the intake to the throttle bodies, for a TT we go in the intake to the turbos back up front to the intercoolers and then to the
throttle bodies (big difference). This can be one of the most difficult things
to put on a NA,
because all the brackets that attach it to the frame on the TT do not exist on the NA you just have to get it in
there and support it the best you can. It isn’t easy to find used and is one of
the main reasons I recommend buying an entire wrecked TT for parts if you are
trying to convert from an NA.
When I have complete sets of plumbing for a TT we sell them together for around $600 (minus
intercoolers and turbos) which is only a fraction of
what they cost new.
9. The exhaust is different for the TT (every single section is
different in some way). Although if you get the J-spec downpipes
(which are stock in Japan in the place of our pre-cats on TT’s) an NA exhaust will bolt right up
and work fine but I recommend at least getting the performance cat-back which
with the J-spec down pipes and NA
cats will be a nice reasonably free-flowing setup. The TT muffler sections have
mandrel bent piping and the NA
ones do not. The TT
resonator section has a smaller resonator because TTs
make less noise (the turbos baffle a lot of it). The
catalytic converters include piping that go all the way up to the manifolds on
an NA or to the
pre-cats on a
10. The fuel system is also different. The fuel
pump and fuel pump control units are different
corresponding to the
higher output TT
injectors. But you can get by with the NA pump and
control unit
on a TT without
extreme mods. The fuel rail, filter, pressure
regulator, and dampener
are all the same.
11. Of course the front fascia is different with
the gills in the bottom corners so air can get to the intercoolers. The fascias
are completely interchangeable but, if converting over most just buy an
aftermarket fascia (Stillen, WW, etc.), all of which
will work for NA or TT. As you all know the TT came with a stock rear
spoiler.