With the engine taken care of I felt it necessary to focus on the turbo setup. There was nothing
specific to the turbo itself but to the ancillaries that support it. Specifically, the wastegate flanges
had been problematic since day-one. The heat from the exhaust was causing the flange bolts to work
their way loose (see bottom of my
GT35R build page. Previously,
without pulling everything off the car I did the best I could and installed some fancy NordLock washers
and better hardware than what came with the original ASpec kit. However the only real solution to a
problem such as this is to drill and safety wire the bolts and nuts so it would be physically impossible
for the bolts and nuts to unscrew themselves. With all the parts off the car I drilled and safety wired
all the wastegate bolts and nuts and safety wired them all together. With the drill press already setup
I also drilled and safety wired the turbine discharge flange connection nuts also, even though they never
gave me any real problems it wouldn’t hurt to safety wire those also. I cut new copper wastegate gaskets
to replace the used and toasted old copper gaskets I had made previously. These are definitely one-time use
items!
One of the most common failure mechanisms with single turbo installations that results in blown
engines is a singed/burnt vacuum line to the wastegate. Basically the vacuum control line to the wastegate
gets too close to the turbo or downpipe and it melts or gets a hole in it. With no vacuum, the wastegate
stays shut, boost spirals up and out of control, and the engine over boosts…KaBlammo motor. With this in
mind I replaced both silicone vacuum lines to the wastegate with braided SS -4 lines w/AN fittings. Each
line was also sheathed in a thermal wrap.
The adapter fittings at the wastegate were easy to find but the adapter fitting at the boost pressure
solenoid took some digging. Apparently the GReddy fitting in the solenoid is a BSPT
[British Standard Pipe Tapered] thread. So trying to find a BSPT fine thread
fitting with an AN-4 female thread on the other end took some time but which I eventually found at
“old faithful” – McMaster.
To better manage the turbine heat I decided to ditch my custom made
aluminum turbine section heat
shield and replace it with a fiber based thermal jacket.
The jacket is much more effective at keeping the heat energy in the turbo and shielding the
neighboring components also. Keeping the heat energy in the turbo means more energy to spool the turbo
itself. On the other side of the turbo to be sure the intake air stays as cool as possible, given its
proximity to the turbine housing, I used a ceramic coated LIM (using the Cerama-Chrome finish so it was
nice and shiney) with an insulating gasket between the LIM and UIM. The LIM to block gasket was of course
upgraded to the OEM metal gasket. Can you believe my car still had the original paper LIM gasket! New
LIM to block studs were installed. I also replaced the fiber based exhaust manifold block gasket with the
expensive but much more reliable OEM steel gasket set. All new exhaust manifold studs were placed in the
block also.
One of the concerns I had with the ASpec
GT35R kit, as supplied,
was the selection of rubber hoses to plumb
oil and coolant to and from the turbo. Rubber doesn’t like heat And sure enough, even though I only
had a few thousand miles on my car since I installed the kit, the coolant hose connections at the turbo
when I removed them were brittle, cracking, and in pretty poor shape. In the interest of reliability
both turbo coolant lines were replaced with braided SS hose with AN fittings, as was the turbo oil drain
line. Not as easy as it sounds. I used AN -8 lines for the coolant plumbing and an AN -10 line for the
oil drain.
The problem being there is not much room, practically none, in between the compressor housing
and turbine housing to fit and tighten the actual hose end fittings to the adapters screwed into the turbo
center section. I eventually simply removed the turbine housing and fitted and tightened the SS lines to
the turbo and then reinstalled the turbine housing (making sure it was clocked the same way).
The coolant line fittings at the turbo were pretty straight forward, however, the other end was a bit of a mystery.
Both these lines connect to the water pump housing, which is made of aluminum. The water pump housing has
large steel coolant hose nipples press fit into the aluminum housing. There wasn’t enough material in the
housing to drill them for threaded fittings. It has been done but this was not a method I wanted to try.
A friend of mine then clued me into a neat trick. First cut the lip (just the lip) off the end of the
steel hose nipple in the housing. Then find an AN adapter fitting for the AN hose size you want to connect.
Cut off the non-AN end of the fitting leaving the nut portion of the fitting.
The fitting should have an inner tube diameter (hole size) a tiny bit *smaller* than the steel hose nipple
on the housing. Then drill out the hole/interior of the AN adapter fitting such that it can slip snugly over
the steel hose nipple on the housing. It really should be a snug fit. Before final fitment, “glue” the fitting to the hose nipple using
some JB weld. The result is you now have an AN fitted connection
to the housing without actually having to drill. The coolant lines I assembled myself – these were cake
after doing all the fuel lines. The oil drain line was a bit simpler because there were flanged connections
at the turbo and the engine front cover which could accept adapters I found through
ATP Turbo. I simply bolted them on and connected the line.
It was VERY tight at the front
cover connection due to the location of the OMP but it will fit. This actually was the location of a small
oil leak that cost Ray at PFS a socket to tighten it down and
stop the leak!
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This page last updated April 1, 2009
