13BREW Engine Rebuild - Turbo Improvements

Safety Wiring the Hardware

Safety wired wastegate flange hardware.

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!

Better Vacuum Lines

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.

Wastegate fittings and braided SS vacuum lines. The BSPT AN adapter fitting for the GReddy boost Solenoid.

A little Insulation

CeramaChromed LIM, Insulating intake gaskets, Turbo blanket

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.

OEM steel exhaust manifold gaskets. Yes, that is the turbo blanket buried down in there.

Turbo Plumbing

The "$100 hose" - turbo oil drain line (not if you buy it off eBay). Flanged fittings from ATP Turbo.

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.

-08 AN coolant return line and -10 AN turbo oil drain line using.

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).

Installing the inlet and outlet coolant line -08 AN hose fitting adapters.

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!

Adapter fitting modification shortcut

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If you would like to contact me and converse about my experiences with my RX-7's:
please feel free to send an e-mail to crispyrx7@yahoo.com

This page last updated April 1, 2009

Disclaimer: All images contained on this page are the sole property of C. Regan.