Project Nissan 300ZX: Part VII

When we last left off, we were busy upgrading the suspension and safety equipment of Project Z in anticipation of big power gains. Work is progressing rather slowly on our promised super engine, but don't despair, we aren't slacking off. Actually, we're moving ahead, but with a complex project like Project Z, we just have to be patient; good things often take time. Our goal is to check off at least one item on our long list every week until the project is completed. Here is what's been going on over the past few months.

Engine Treatment
To withstand the 500 rear-wheel hp we anticipate, we must fortify every little detail of our VG30DETT. In our installment featured in the September '99 issue, we looked at the Cunningham forged rods and JWT pistons that were going to be fitted to our engine. We also covered the cryogenic treatment that our block and crank were getting, and we touched on the epoxy block stiffening treatment that the block was undergoing to ensure reliability. If you read that installment, you may have thought we did everything that could possibly be done to a VG30. Well, there's more. Here are some additional tweaks we are currently undertaking.

Straight from the factory, the water passages of a VG30DETT are filled with casting flash. This is due to core shift and the way the sand mold for the block is filled during production. The casting flash is so bad that the main water gallery in the vee of the engine is almost completely obstructed by the flash towards the rear of the block on most VG30 engines.

People that are experienced with building VG30DETT's know that cylinders 5 and 6 (the two rear-most cylinders) are prone to failure on high-output engines. It is most often that these two cylinders show signs of detonation when a VG30DETT is run at the limit. Rear cylinders failing? Restricted water flow to those rear cylinders? Hmm... Elementary, my dear Watson. We must improve the water flow to the rear cylinders.

JWT's Mike Smith carefully ported the block's main water passage to vastly improve water flow. He used a carbide cutter with a long bit to remove all of the obstructing casting flash from the block's central water passage. Smith also deburred all of the water passages in the block leading away from the main coolant passage to help reduce turbulence and cavitation. Smith polished and radiused the block recess and passage behind the water pump as well. The result is a passage with 75 percent more flow area--the way Nissan intended it to be. Hopefully this will cure the thermal stress on the two rear-most cylinders as well as make the engine run cooler. This should have a big impact on the engine's reliability.

Very high horsepower VG's are hard on their rod bearings. If a 500-plus hp VG is pushed into serious detonation, it is very easy for them to pound out and spin their rod bearings. We took several measures to reduce this potential hazard on Project Z. Instead of the stock soft tri-metal rod bearings, we used the heavy-duty aluminum faced rod bearings used on the old single turbo Z31 and the Frontier truck. These bearings have superior load-bearing capacity, but are not as forgiving to dirt contamination, as they lack the softness of the softer stock lead, tin, zinc tri-metal bearing. Since we use only the finest synthetic oils in our engines and change them frequently, as well as painstakingly cleaning our block before assembly, we do not think dirt in the engine will be much of an issue.

Coatings
Again, to improve reliability of our super engine, we turned to Swain Technologies to supply us with coatings to help keep our engine alive and healthy at high power levels. We have used Swain's coatings before with excellent results on the Z's little brother, Project 200SX SE-R and opted to use every advantage-gaining coating that Swain had to offer in order for our engine to live at big power levels. Nissan Motorsports makes extensive and successful use of Swain coatings in the Infinti IRL engine and we heeded many of its coating suggestions for this project.

To protect the domes of our pistons from heat and detonation, we used Swain's Gold Coat thermo-barrier coating. Unlike many coating houses that use generic off-the-shelf thermal barrier coatings, Swain develops its own in-house coatings that are much more sophisticated. Gold Coat is a severe-duty, three-layer thermal barrier that reduces heat transfer by about 25 percent. The different layers provide different protective functions. This helps better protect the pistons from detonation and other high-boost abuse. By keeping the heat out of the pistons, we can run an amazingly tight (for a forged piston) clearance of 0.0025 inches. Gold Coat also helps distribute the combustion heat evenly across the top of the piston to help ensure complete combustion and to reduce any detonation-starting hot spots that could form under high boost.

We also had Swain apply its Poly Moly dry-film lubricant piston skirt coating to our pistons. This coating uses molybdenum disulfide and tungsten disulfide for a dimensionally stable heat-conducting matrix. This is better than the Teflon that most other companies use because Teflon, being a soft plastic, distorts and creeps under load. Teflon is also a heat insulator. Since the pistons cool themselves by conducting heat through the skirts, insulated skirts are not a good idea. Poly Moly will help tame the clatter of our forged pistons. Since Poly Moly also tightens the piston-to-wall clearance by about 0.0014 inches, our total clearance will be down to a very low 0.0011 inches. This will eliminate piston slap, improve ring seal and help reduce oil consumption.

To conduct heat away from the piston, we coated the bottom of the piston with Swain's black body emitter coating. This voodoo stuff is supposed to be able to increase the heat emissivity of whatever it coats. Since oil jets cool the bottom of Project Z's pistons, we figured this coating would help cool the pistons even more. Swain also recommends coating intercoolers, brake calipers and radiators with this coating to improve cooling.

Since Project Z's cylinders are going to carry the high load of turbocharging, we coated the piston rings with Swain's new anti-wear coating. Proven in long-duration NASCAR events, this coating helps prevent piston ring and piston ring groove wear while reducing galling under extreme combustion pressures. This will help our rings maintain a better seal longer under our anticipated tough conditions.

As we mentioned before, since VG30 bearings get pounded, we treated our bearings to Swain's bearing anti-wear coating. This coating is very similar to Poly Moly and is designed to bear high loads without distortion, provide lubricity and to conduct heat, two things a bearing coating needs to do well.

Our combustion chambers, the bottom of the intake valves, the entire surface of the exhaust valves and the exhaust port were coated with Swain's two-layer thermal barrier coating. This protects these parts from the effects of heat and detonation in addition to preventing the head from absorbing too much heat. Much of the heat energy that used to heat the water jackets of the head will now be used to drive the piston downward and to help spool the turbochargers more quickly. We have seen exhaust gas temperature jump by 200 to 300 degrees and water temps stay 20 to 30 degrees lower in other turbo engines that are using these coatings.

The Z has a very crowded engine compartment and tiny grille openings. Combine that with a belly pan and lots of hot things like turbos under the hood and you get one hellish engine compartment. During consecutive acceleration runs, we have noticed a drop in power and an increasing propensity to detonate. With all of this heat soak, we have noticed that our manifold gets egg-frying hot, too hot to touch with the bare hand after a few blasts around town. To help combat the effects of heatsoak, we coated the underside of the intake manifold with Swain's Thermo Barrier coating. In an effort to reduce some underhood heat, we also Swain-coated the exhaust housing of our turbos and our exhaust manifolds.

To test how well Swain's coating works, we checked the surface temps of another Z we have built. The Z's exhaust flows first through the exhaust manifold, then through an O2 sensor housing, and then to the turbo. We coated the exhaust manifold with Swain thermal barrier coating, and the O2 sensor housing with a generic polished silver thermal-barrier coating. Despite the fact that it's closer to the exhaust ports, the Swain coated exhaust manifold was always at least 125 degrees cooler than the O2 sensor housing.

Finally, Swain treated our intake port and inside face of our intake valve with its Flow Coat. Flow Coat is a super-slippery Teflon-type coating that helps improve airflow and resists build-up of fuel residue and carbon. Residue sticking to port walls and backsides of intake valves is a serious problem with EFI cars and can really hurt performance. Flow Coat should reduce this build up and improve flow.

We anticipate that the Swain coatings might free up a bit of power and will certainly improve component life--that is if our experiences with other projects apply here. Swain coatings should be considered cheap insurance for reliability.

Water Injection
In an effort to run more boost without having to resort to running race gas full time, and to help keep our engine cool during extended high-speed runs such as hot lapping, we installed an ERL Aquamist competition water injection system. Unlike the crude windshield washer pump-based systems of old, the Aquamist system uses a sophisticated, solid-state, piston-type pump that pumps the water at 125 psi. At this high pressure, there is little likelihood that boost pressure can reduce water flow significantly. A windshield washer pump, by contrast, can only run 10 to 20 psi. If you only have a 10 psi water pump and are running 20 psi of boost pressure, you will end up reverse-flowing boost pressurized air throughout your water injection system.

Water injection relies on water's naturally high specific heat, which means it requires a lot of heat to change liquid water into water vapor (steam). The high specific heat is one of the reasons why water is an excellent coolant. When injected into an engine, water does several things. When it is first injected, some of the water vaporizes absorbing heat from the incoming intake stream. This helps cool the hot intake charge in much the same way nitrous oxide injected into the intake of a nitrous-equipped car does. Since the Z's stuffy engine compartment and intake tract suffer from heat soak, we will really need this intercooling effect.

Once inside the combustion chamber, the water is fully vaporized into steam. This vaporization absorbs a tremendous amount of heat from the combustion reaction, helping cool the engine internally to prevent glowing hot spots (areas of self-ignition where detonation propagates). The heat absorbed from the water's phase change also acts to buffer the combustion event, slowing it down. Thus, the water helps regular pump gas behave much like slow, controlled-burn, high-octane race gas.

The superheated steam also acts like a powerful steam cleaner inside of the engine, removing compression-raising, hot-spot-propagating carbon deposits from the combustion chamber and spark plugs. This is a pretty cool side benefit of water injection.

Since water absorbs power-producing heat, it does not produce quite the same horsepower per psi of boost as race gas does, but it does allow quite a bit of additional boost. Because of its cooling and combustion buffering effects, water also goes a long way to eliminate engine-damaging detonation.

The Aquamist water injection system uses a unique proprietary atomizer nozzle to introduce the water to the intake air stream. The nozzle produces a range of droplet sizes from a fine fog to a coarse mist. This helps the water work more efficiently. The fine water fog vaporizes almost immediately, helping reduce the intake air temperature by about 20 to 30 degrees. The larger droplets do not vaporize until they reach the combustion chamber where they can perform their internal cooling and combustion buffering duties. All of the droplets are small enough where the even distribution of water throughout the manifold plenum is assured. Since most modern fuel injected cars have manifolds that are designed to flow dry air only, not a mixture of liquid and air, the maintenance of correct water droplet size is critical for even cylinder-to-cylinder water distribution.

Since we first tried the Aquamist system, we have had nothing but success with water injection for both increasing power and getting more reliability out of heavily boosted engines.

The Aquamist system works so well that almost all of the psycho turbocharged Group-A rally cars in Europe use this exact system with up to 3 bar of boost. Some rally cars use two pumps with multiple nozzles for even more water flow. In fact, the European-market Ford Sierra Cosworth uses this system as original equipment from the factory! This alone speaks highly of the system's reliability and performance.

In previous testing, the Aquamist system was able to keep a turbocharged SE-R's engine from getting coolant temperatures above 200 degrees during hard track lapping on a 100-degree day. Stock SE-Rs will normally overheat under these conditions, no less turbocharged. This is a strong testament to the ability of water injection to keep an engine from overheating under extreme conditions. Since the Z's tight engine compartment suffers from poor air circulation and the Z is also prone to overheat under track conditions, the Aquamist system is going to be one of our strategies to help keep the engine cool and in one piece at the track.

The Aquamist system can be tuned using different sizes of jets ranging from 0.40 mm to 1.0 mm. We opted for twin 0.5 mm jets, treating our engine as two, small 1500-cc three-cylinder engines. We used the Z's rear-mounted windshield washer reservoir as the water holding tank for the Aquamist system, since the Z is so tight that there was no place else to fit an additional water tank. Because of the Z's lack of space, we were forced to mount the Aquamist pump to the backside of the front bumper support. This sounds less than ideal, but because space goes for such a premium in a Z, this was literally the only place we could find!

To partially offset the power-reducing, internal-quenching effect produced by the water, a leaner fuel-air mixture and more ignition advance can be run. Advancing timing on a turbocharged engine that has been retarded to avoid detonation will not only increase power output, but also reduce exhaust gas temperature--a good thing. JWT will program a special ECU that has a special map to complement the water injection system once we get close to getting our engine running.

The water injection system is almost like having a perpetual tank full of race gas--without the $5-per-gallon cost. After all, water is cheap. For once in the history of hot rodding, something can be done for nearly nothing. As an interesting side note, water injection also reduces toxic oxides of nitrogen emissions by reducing combustion temperatures. All of these advantages and cleaner air to boot!

Improved Intercooler Airflow
The Z has pretty good intercooler air flow management in stock trim, with molded plastic ducts directing the airflow from vents in the front bumper to the intercooler. With the big intercoolers, these ducts do not fit anymore and the intercoolers have to depend on random air coming through the bumper vents. This really hurts the efficiency of the intercoolers (even though they are still much better than stock).

Another issue is that air entering the area of the intercoolers has no place to go as the area is almost like a sealed box. In order to have good flow through the intercooler, the air must be able to exit, something it cannot easily do in the stock car.

Finally the radiator overflow tank seems to be specially designed to block air from flowing through the driver's side intercooler as it is practically molded to the back of the intercooler! In testing, we have found the driver's side intake can receive air almost 20 degrees hotter than the right side because of this.

To help combat this tendancy, Stillen has made new intercooler ducts that bolt to its much larger intercoolers. These ducts ensure the intercooler gets a directed airflow straight from the bumper vents. The Stillen ducts are also pretty generously sized, so they will work with the bigger vents that many aerokit airdams have. We have found in the past that ductwork can increase the efficiency of a heat exchanger by up to 40 percent or sometimes even more. These ducts should really help the Stillen intercoolers perform even better.

To give the air from the intercoolers somewhere to go, we installed in our plastic inner fender liners, right behind the back of the intercoolers, some plastic louvers that were made for us by a fabricator friend. Not all of you have friends that can custom mold some of these, but a vent diffuser from a hardware store will work just as well. The 1990 300ZXTT had inner fender liner louvers for the first few months of production, but they were deleted as a cost saving measure. Unfortunately, they no longer exist in the Nissan parts system anymore, so if you want them, you have to do it yourself. These significantly improve airflow by giving the air a low-pressure zone to migrate to.

Finally, we axed the stock radiator overflow tank, replacing it with a universal tank from Summit Racing. We fabricated a bracket out of angle aluminum to mount the tank and bolted it to the core support beside the driver's side intercooler. We plumbed the tank to the radiator with Hose Techniques' new slick-looking, polyester- reinforced, silicone heater hose. Now, air can flow through the intercooler without any restriction.

Although we have not yet had time for thermocouple testing, the power loss under subsequent WOT runs is not as apparent, even on a 100-degree Southern California day. The engine seems much happier and less affected by heat in general.

Some of the casting flash that blocks the water passage is visible from the top of the motor looking down through a freeze plug hole. At this point, the flash blocks a great deal of the passage.

The water passage from the same top view after JWT cleaned it. Notice the casting flash is now gone. You can also see some of the epoxy reinforcement on the left side of the picture.

JWT modified our block's main water passage, so coolant now has free flow throughout the engine. This should really improve flow to the rear-most cylinders. Note the water pump area is also polished and radiused.

The top of the JWT forged pistons were coated with Swain's extreme duty Gold Coat while the piston skirts were coated with slippery Poly-Moly.

The bottom of the pistons were coated with Swain's heat-emitter coating. This should help the oil from the piston coolers carry away heat.

The piston rings were coated with Swain's anti-wear, anti-galling ring coating for better performance under high-boost conditions.

The highly stressed rod bearings were given a protective layer of Swain's bearing coating.

Here is a view of the coated valve faces and the combustion chamber. All areas exposed to combustion heat are fully protected.

We coated the combustion chamber with Swain's Thermo Barrier coating, which is light gray against the silvery metal of the head. You can also see the black flow coat in the intake port and the coating in the exhaust port in this view.

The intake valve face is coated with Swain Thermo Barrier coating to protect it from combustion heat while its backside is coated with flow coat to prevent deposits from sticking and to improve flow. The exhaust valve is fully coated with thermo-barrier coating to protect it from heat.

The Aquamist high-pressure pump was wedged behind the aluminum bumper support as the Z has very little under-hood room.

The Aquamist atomizer nozzle installs into the intake tract before the throttle body. The silver cylinder is a one bar check valve to maintain pressure in the system to reduce water lag.

Stillen's molded plastic intercooler ductwork does an excellent job of directing air to the intercooler. Ducts like this drastically improve intercooler efficiency. The duct is cut oversize where it meets the bumper, so it should still work with aftermarket aero kits.

We pop riveted these louvers into project Z's inner fender panels right behind the intercoolers to give a low-pressure area for the hot air from the intercoolers to flow to.

Since the factory radiator tank seemed to be especially designed by Nissan engineers to prevent flow through the driver's side intercooler, we replaced it with this relocated overflow bottle by Summit Racing. The bottle was bolted to a bracket on the side of the intercooler.