Z32 Basic Terms

Here you will find the most basic terms about the Z32 or second generation of the 300zx.

• 2+2 / 2+0
• AIV Valves
• ALC - Automatic Line Controller
• Boost
• Boost Jets/Welding Tips
• Cats
• Cat-Back Performance Exhaust
• Chip
• Cold plugs
• CAS - Crank Angle Sensor
• Detonation
• Detonation Sensor
• Downpipes
• Dual POP Charger
• ECU
• EGR
• EPROM
• EVC
• Fascia
• Fairlady Z
• Gutting the Cats
• H-Pipe
• HICAS
• Injectors
• Intake
• Intercoolers
• MAS
• NA/TT
• NOS-Nitrous Oxide System
• O2 Sensors
• PCV-Positive Crankcase Ventilation
• Plenum
• POP Charger
• Power Transistor Recall
• Pre-cats
• Pre-silencers
• Safety Boost
• Slicktop
• Soft Valves (early models)
• Spool
• SR-71
• Stages
• Sway Bar
• Test Pipes
• Throttle Bodies
• TPS-Throttle Position Sensor
• Turbos
• Turbo Timer
• Underdrive Pulley
• Valence
• Welding Tips
• X-Pipe
• Z32

2+0 : Also known as a coupe. Two front seats, no back seat
2+2 : Two front seats, two (small) back seats

How to recognize them...

The 2+0 has the fuel door in FRONT of the rear left wheel, while the 2+2 has the fuel door AFTER the rear left wheel.

The following info is only about models that can be bought through local dealerships (not converted, not privately imported)

In the US,
- ALL the 2+2 ARE NA, there was no 2+2 TT imported.
- The 2+0 can either be a NA or a TT
- Convertibles are based on the 2+0 model and are only non turbo

In Europe
- ALL the 90+ are 2+2 AND TT
- The 2+0 are not available
- The non turbo models are not available

In Japan
- The 2+0 can either be TT or NA
- The 2+2 can either be TT or NA
- A special recardo edition existed

The AIV function, as described in the manual, is to send secondary air to the exhaust manifold using a vacuum created by exhaust pulsation in the exhaust manifold. When the exhaust pressure is below atmospheric pressure, secondary air is sent to the exhaust manifold. When the exhaust pressure is above atmospheric pressure, the reed valves prevent secondary air form being sent back to the sub-air cleaner. I've heard that de-acceleration is supposed to keep the assembly clear of water.

As for the AIV (air injection valves) "gurgling", they are in the front fender wells behind the plastic shielding at the rear of the front tires. Very few 90-92 ZXs have escaped a failure of these. Symptoms include the "gurgling" sound at idle that stops just off idle and returns on decel back to idle. Also the car will fail the idle portion of most smog inspections, since the ECU adds 7% more fuel when they operate so the extra air they pump to the catalytic converter has some fuel to burn to keep the cat up to temp. If the AIVs are not sucking air into the exhaust the fuel just passes through making things worse then ever. The fix is to try to clean and align the reeds in the AIVs, replace reeds, or replace the AIVs as an assembly.

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ALC-Automatic Line Controller
The ALC is a product made by HKS and ALC stands for: Automatic Line Controller.

The ALC was developed for the computer controlled automatic transmission as equipped on the Z. It is designed to maintain line pressure within the transmission for consistent, high performance shifting.

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Boost
The amount of positive air/fuel mixture pressure inside the intake. Usually measured in pounds per square inch (PSI), but sometimes measured in barametric (bar). Alternately, a negative intake pressure is vacuum.

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Boost Jets/Welding Tips
Calibrated Boost Jets come with the Jim Wolf ECU upgrade. They are simply small orifices to restrict vacuum pressure to the turbo wastegates, causing the wastegates to stay closed until a much higher boost pressure is achieved. The power gained from the ECU upgrade is from the boost jets, not the ECU. The ECU is remapped to provide adequate air/fuel mixture to the engine under the altered boost levels.

Contact Welding tips are originally used to meter gas on welding guns, but can be used in place of boost jets. They are metal, not aluminum like boost jets, so are a bit easier to work with since they are sturdier.

They can be bought at any welding supply shop in different metering hole sizes, such as 0.045 inch, 0.035, 0.030, and 0.025 inch. since they came in many sizes, boost level can be fine tuned to your requiremnent.

***Caution***

Remember that a Jim Wolf ECU upgrade makes the raised boost safe, but boost can be raised on a stock ecu up to about 14 psi if you use it sparingly, i.e.: no top speed runs, etc. It is also of prime importance to always have an accurate boost gauge (non-stock) on the car and use cooler pfr6b-11b(#6) NGK plugs or pfr6b-11 plugs to help ward off detonation . The boost limits of the stock injectors is 15.5 psi per Jim Wolf.

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Cats
Catalytic convertors are devices used in the exhaust system to reduce pollution of the environment from unstable hydrocarbons from the emission.

They contain some catalysts (like vanadium or platinum) that neutralize unburnt hydrocarbons into carbon di-oxide and water.

Cars with cats (after 1975) should only use unleaded fuel as the lead (Lead tetra-ethyl was added to gas to reduce knocking  and to lubricate) in the gas will coat the catalysts and make them inoperative.

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Cat-Back Performance Exhaust
An exhaust from your main catalytic convertors back to the mufflers. Most cat back exhaust are 2.5 inch to 3 inches in diameter. Depending on your needs, anything above 500 horsepower should have a 3 inch system so the air can flow much faster. Prices for a cat-back system can range from about $400-$900, depending on who the supplier is. However, you can have a custom built cat-back system using a 2.5 or 3 inch pipe with the mufflers of your choice, or you can purchase a complete system from any major supplier which will include not only the pipes but the mufflers also. Most cat-back exhaust system are built to achieve maximum power from an engine by letting the air flow much quicker and smoother... Hence most aftermarket exhausts use mandrel-bent pipes which allows the air to flow quicker and smoother. Power gained from an aftermarket exhaust is best determined by a dyno, but in most cases expect about 20-30 more horsepower. Choosing an aftermarket muffler not only depends on the about of horsepower gained but also on the way it SOUNDS!!

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Chip
See EPROM

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Cold plugs
Used in cars that will see harder use since the combustion temperatures rise and promotes detonation.

The lower the #, the hotter the plug.

The stock TT plug is a #5. Typically, colder plugs are used when raising boost in the TT's. PFR6b-11B is the part # for the  #6 plug and PFR6B-11 is for the #7.

Colder plugs aren't generallly used for the N/A Z's since they do not heat up their combustion chambers as much as the TT's.

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CAS - Crank Angle Sensor
Known in the service manual as the CMPS - Camshaft Position Sensor. The CMPS monitors engine speed & piston position to send the data to the ECU. It's basically a disc with 360 slits cut in it around the perimeter & 6 slits cut to mark the 120 degree positions. It uses photodiodes to transmit light through the slits while rotating to determine speed & angle.

www.nhtsa.dot.gov
Service Bulletin #: FC0004794
Date of Bulletin: Jan. '91
Model: 300ZX
Year: 1990

Summary: Excessive initial timing advance, index notch on camshaft damaged, R/R crank angle sensor, camshaft and cylinder head--1990-91 300ZX CM

The problem was that the left cylinder head of a certain production # range of early Z cars ('90) was mis-machined. This caused the CAS to be thrown off in its readings of cam timing, so the symptoms are usually very sluggish performance or detonation. Eventually the readings of the CAS stray so far (for reasons unknown to me) that the symptoms show up when the cars have some mileage on them. I've heard of some having this problem and they replaced the CAS, but the CAS was expected to fail again, because the root of the problem is the badly machined left cylinder head.

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Detonation
When increasing boost, there is a danger of detonation. Detonation occurs when the compressed air and gasoline ignite due to the heat of compression before the spark plug sparks. This results in a loss of power (at least) or blowing holes out of the side of the engine block (very bad). Higher octane fuel has a slower burn rate, and is less susceptible to detonation.

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Detonation Sensor
The detonation sensor (or knock sensor) is a piezoelectric sensor that detects detonation noise below 3500rpm and sends a signal to the ECU. If detonation is detected below 3500rpm the ECU will cut the boost to 7psi and retard the timing in order to protect the engine. Any detonation above 3500rpm will not be detected by the detonation sensor and the ECU will not
protect the engine.

The detonation sensor is mounted to the block between the heads. To replace this sensor the engine has to be removed ($$$$).

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Downpipes/Testpipes
The purpose of down and test pipes is to reduce the flow restriction imposed by the catylitic convertors.

Down pipes are hollow pipes used to replace the restrictive pre-cats that come right after the turbos on TT Z's. They sell for about $500 for stainless steel units.

N/A Z's do not have pre-cats. most people do not keep the pre-cats since they are easily gutted when the clutch is changed or the trans is dropped.

Test pipes are hollow pipes that replace the two main cats under the car. The main cats can be hollowed out for similar effect.

***This is not a legal modification in the U.S. for street-driven and registered vehicles and should only be done when the car is an off-road track car. Getting caught carries high penalties.***

On a Stage III TT, gutted/removed pre-cats can gain 10-15hp & gutted/removed main cats can gain 10-15hp too.

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Dual POP Charger
Only Useful if the TT engine is producing 450 or more HP.

The kit consists of TWO POP chargers installed side by side where the air intake was. The MAS will be relocated on one of the side, while the other will only have a tube.

(If the car already has a POP charger, only the required parts will be needed)

Because the MAS will only see HALF of the air going to the engine, the ECU will have to get a new EPROM programmed to handle the change.

The low speed driveability may suffer, and the JWT "low speed driveability update" should be installed (comes free with the DUAL POP charger). Installation of the "low speed driveability update" will required to cut some vacuum lines, drill a hole in the right stock surge valve, and route a hose to it.

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ECU
Acronym : ECU = Engine Control Unit.

Location : Under the passenger's foot well, under the wooden board.

Function : This is the "computer" that is controlling all the engine functions.

Notes : When you put a "performance" upgrade, you'll have to change the "software" in it. The software is stored in an EPROM .

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EGR
This is a valve on the engine that goes from the exhaust manifold to the intake manifold, controlled by the ECU. When the ECU senses that there is too much oxygen in the exhaust, it diverts some exhaust gas into the cylinder, reducing the oxygen in the cylinder, causing more total ignition of the available oxygen and gas, and reduced emissions.

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EPROM
Acronym : EPROM = Erasable Programmable Read Only Memory Also known as a "chip".

Location : Inside the ECU which is under the passenger's foot well, under the wooden board.

Function : The EPROM is an electronic component where the software running the ECU, and the data about the car (i.e. maps) are (semi) permanently stored. Most of the modification that can be done to a Z are through some optimization of this code, and the modification of the data.

The EPROM is kind of a "silicon floppy disk"

Notes : The EPROM is a 28 pin "chip" that has the software code to run/manage the engine stored on it. When you upgrade your "chip", you are actually buying a new/modified EPROM with different "software" on it.

In the case of Jim Wolf Technology (JWT) the code has been SUBSTANTIALLY changed. In the case of SuperChips, only ONE byte on the entire EPROM is different (removal of the speed limiter).

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EVC
This aftermarket modification controls the level of turbo boost in the Z. This is attained by a solenoid which sits in the engine bay that is connected 'through' the boost line (it goes in between the intake and the wastegate on the turbo.) The EVC's solenoid stays closed which doesn't allow the wastegate to see the pressure that is really building up (it thinks boost is low so it's staying closed also). Then, at the last second (once desired boost is seen by the EVC), the EVC solenoid opens, and the wastegates slam open and shut again (I think this takes like a nanosecond,) and this is what allows the EVC to keep rock-steady boost at a pre-programmed level.

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Fascia
Basically, this is the front bumper on a 300ZX. A stock TT fascia will have intercooler "gills" underneath the turn signals.  Along with the wing, this is the most popular body molding upgrades.  Many companies make aftermarket front fascias for both NA and TT models.

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Fairlady Z
The Short Story:
Fairlady - The name given to the first line of sports cars designed and built by Nissan Motors Japan after W.W.II, with the specific intent of being marketed in the USA - 1960.

The name "Fairlady" was given to the new sports car line by Mr. Katsuji Kawamata, President Of Nissan Motors Japan, after he attended the Broadway Musical "My Fair Lady" while visiting the US in 1958.  He felt that the name would invoke an image of beauty for the car - because people would think of the beauty of the music and the leading lady in that Broadway Musical.

This is a common and accepted practice within the Japanese culture for selecting automotive names.  It is not a usual cultural method here in the US however - so Nissan more commonly used engine size and model numbers as Model Names for the US market. (Note  There are also minor differences in many cases related to engine sizes, safety and emissions equipment between the Japanese home market models (Fairlady Z's) that thoes exported to other countries)

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Gutting the Cats
To remove the catalytic material from inside the exhaust, this allows much freer flow of the exhaust gasses. Gutting all four can gain ~22hp on TTs. NAs should retain their cats to keep enough backpressure for optimum performance, TTs get backpressure from the turbine side of the turbo.

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H-Pipe
A style of exhaust pipe between the main cats & the mufflers sections. The left & right side pipes are joined with a center pipe in an 'H' fashion for balancing the exhaust pressures before the mufflers.

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HICAS
Acronym for: High Capacity Actively Controlled Suspension.

Method by which all 4 wheels are steered based on information processed by the HICAS control unit with the main input being vehicle speed.

For some detailed info: click here or get "Nissan 300ZX: An Enthusiast's Guide" by Ray Hutton (of C&D fame)

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Injectors
Small solenoid valve that injects atomized fuel into cylinder. Signal from ECU causes coil in injector to energize, pulling a
pintle back from the tip of the injector, allowing fuel to spray out. The duration of the spray is varied by the ECU depending
on throttle position, RPM, etc.

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Intake
See POP Charger.

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Intercoolers
Turbochargers compress air. From PV=nRT, the only other variable is temperature. When boost pressure goes up, so does temperature. Hot air is less dense. Intercoolers cool the air, making it denser, creating more burnable oxygen per unit, equalling more horsepower. Larger intercoolers  work better, making more hp.

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MAS
MAF = Mass Airflow Sensor

A device which measures the amount (mass) of air inducted into the engine. This measurement is used by the ECU to calculate the amount of fuel neccessary for complete and safe combustion.

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NA/TT
NA (Naturally Aspirated) - Non-Turbo version of the Z. 10.5:1 compression, 222 horsepower stock, 225/50-16 stock tire size, 16x7.5 stock wheel size. 4.08 rear differential ratio. Available in convertible, 2+2, t-top, and slicktop.

TT (Twin Turbo) - Turbocharged version of the Z. Compression dropped to 8.5:1, 300 horsepower stock, 9.5 psi boost from the factory. Same tire/wheel combo in front, but with 245/45-16 on 16x8.5 wheel in the back. Front fascia changed for intercooler slots. 3.69 rear differential ratio. Heavier clutch & clutch vacuum booster, Super HICAS rear wheel steering, t-tops, rear spoiler/wing, TwinTurbo sticker on rear right side, adjustable suspension, & dash cluster boost gauge are all standard equipment. See 2+2 / 2+0 for more configuration specs.

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NOS-Nitrous Oxide System
Nitrous Oxide is a gas. It's properties dictate that it burns faster and hotter than oxygen. A NOS system sprays Nitrous Oxide into the air stream coming into the engine (before it gets to any of the 6 cylinders,) this then mixes with the air coming in and gets drawn into the cylinders. More power is provided because of the faster and hotter burning of NOS compared with the air it's mixed with. NOS systems usually draw quite a concern about the added stress it puts on an engine (and it really does pack quite a punch when released.) But, the VG30DE engine in the Z is quite a strong one and withstands this quite well. Nevertheless, caution (and moderation :) should be taken in using any Nitrous setup.

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O2 Sensors
The O2 sensor's purpose is to read how much oxygen is present in the exhaust. This signal is sent to the ECU. This signal is used to tell the ecu how rich or lean the air/fuel mixture is so the ecu can adjust how much fuel the injectors inject to achieve as close to a 14.7:1 stoichiometric air/fuel ratio, which is neither rich nor lean and produces good power and fuel economy.

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PCV-Positive Crankcase Ventilation
The purpose of the PCV valves is to relieve pressure that might build up in the engine (crankcase). This pressure can arise due to a slight amount of pressure (from the fuel burning in the pistons) "leaking" its way past the piston rings, into the crankcase.

Excessive pressure can cause engine oil seepage past the engine seals, especially the main rear seal, out of the engine, where it may slightly leak to the ground, or be burned on the exhaust pipes.

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Plenum
The plenum (or upper intake) is the upper piece on the engine that is connected to the throttle bodies. The plenum is what separates the air to go into the lower intake and then to the intake runners on the heads.

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POP Charger
POP=Jim Wolf Technology's Performance Optimized Programming. This is a cone air filter/intake 'velocity stack' that replaces the stock air box, reducing induction restriction, and give some extra horsepower and fuel mileage. It either comes with a K&N filter (Stillen) or a generic one (some JWT), both of which are washable

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Power Transistor Recall
The power transistor is the unit that amplifies the ignition signal to each of the 6 individual ignition coils. The early Hitachi ones on 90' and 91' Z's were prone to failure so Nissan made a voluntary recall on them to replace with a new improved Mitsubishi unit.

The symptoms of a bad power transistor are stalling and running rough. Many times, the car will not restart once it stalls. Nissan is to pay for towing as well as the part since this is a recall.

A few of the replacements have failed as well, so Nissan should pay to replace the faulty transistor again.

Call 1-800-Nissan-1 with your VIN # handy so you can find out if the recall has been performed on your Z.

Even if the Power transistor is exactly the same all around the world, Nissan decided that ONLY the US Z can benefit from the recall !

So if (or more exactly when) it'll fail, the NON-US Zers have to buy a replacement Power Transistor Unit , very often at a overinflated price (depending on your country, you may be charged between 2 to 5 times the US price).

And to add insult to injury, the power transistor unit you'll then get will have the same old, faulty design, and will fail again (guess how I know ?)

The best workaround is to buy one in the US , and install it yourself (it's easy, and can be done in about 20 minutes)

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Pre-cats
Only on TTs. The pre-cats are a second set of catalytic convertors for cold start emissions purposes. They are immediately after the turbos in the exhaust pipes. The main cats are sufficient to pass regular emissions tests, so a lot of the time they are 'gutted' or replaced with downpipes, gaining ~10rwhp & decreasing spool-up time, while still meeting most standard emissions requirements.

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Pre-silencers
The stock exhaust & some performance cat-back systems utilize pre-silencers to aid the mufflers in quietening the exhaust note. They come between the main cats and the muffler sections of the exhaust. On other performance exhaust systems, they are replaced with an 'H' or 'X' style pipe.

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Safety Boost
When detonation occurs at low rpm, the ECU invokes safety boost which reduces the boost to about 5-7 psi to protect the engine.

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Slicktop
Production model of the Z possessing a hardtop to the driver's cabin in lieu of the T-roof or convertible top. Relatively few were produced and all were normally aspirated. These machines are approximately 200 pounds lighter than the standard T-roof model.

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Soft Valves (early models)
This is a known problem with the very early '90+ Z's, both NA and TT.

Somewhere around 350 1990 Z motors were produced with 'soft' intake valves. The chances of having one of these  engines is pretty remote. There were 35,000 or so 1990 models sold in the US alone. It took Nissan until mid-1992 to get enough data together to determine what the problem was and to isolate it when it occurred. By then, cars had tens of thousands of miles on them, so it's not a problem that occured in the early stages of ownership. Although Nissan published a Technical Bulletin describing the problem and giving the engine serial numbers affected, not all of the engines in the group will experience the problem.

Other problems could cause these symptoms including a worn spring in the intake valve timing cam. This is also a known problem, which Nissan diagnosed in 1992 also and issued another Technical Bulletin about. This is much more common and could be the problem here. Three things could cause the noise: the VTC tensioner spring, the auto tensioner, or a lifter. Nissan indicates in the Technical Bulletin that the lifter is the primary suspect, followed by the VTC spring and then the tensioner.

Then, just to confuse things, Maximas, which use a different head, have a similar problem that's caused by some other things. I mention this because some folks have confused the Maxima problems with the 300ZX ones because the engines are similar.

The 'soft' valve problem *could* be in NA engines with serial numbers lower than 777599, while TT engines are lower than 619550. The engine serial number is located on the rear of  the passenger's side head. Car assembly dates are earlier than June 22, 1990 for NA's and December 11, 1989 for TT's. The intake cam problems are NA ENGINES ONLY, and are for engine serial numbers lower than 475679 in cars with VIN's lower than 012836 for the coupes and 003754 for 2+2's

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Spool
Spool up time is the amount of time it takes to reach full boost from a turbo. Spool up is a function of turbo design and how much exhaust flow reaches the turbo. On the ZTT, this is at about 3500 rpm's.

Larger aftermarket turbos can have nearly stock spool up, but will flow more air which produces more power per given boost pressure level(psi).

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SR-71
The SR71 is a limited edition 300ZX that was modified by Texas Motorsports and was done similar to what Saleen does to the Mustang.

They took stock 300ZXs and upgraded them to a Stage VII w/NOS using mostly HKS products, along with Kaminari bodykit and forged 3pc BBS rims.

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Stages
This is the standard benchmark Twinturbo Z stage chart. Most people use this as their performance upgrade path:
 

Stages:	Modifications Required:	Approximate M-T HP at Flywheel & Boost Pressure
Stock	None	300hp 9.5 psi
Stage I	Performance cat-back exhaust system	320hp 10 psi
Stage II	High flow intake	340hp 10.5 psi
Stage III	ECU EPROM upgrade & boost jets	396hp 13.5 psi
Stage IV	Larger intercoolers	405hp 13.5 psi
Stage V	EVC	418hp 14.5 psi
Stage VI	555cc injectors & 550 type turbo upgrade	445-500hp 16.5 psi
Stage VII	Dual high flow intake	520hp 16.5 psi
Stage VIII	600 type turbo upgrade	620hp variable psi
Stage IX	NOS	680-760hp variable psi

 
This standard stage chart is a bit dated. SGP Performance has made an updated TT chart to include newer modifications & rearranged a few of the steps in their performance upgrade path. On the forum, you'll see this noted as SGP Stage ????.
 

Stages:	Modifications Required:	Approximate M-T HP at Flywheel & Boost Pressure
Stock	None	300hp 9.5 psi
Stage I	JWT POP charger & Underdrive pulley	305-325 hp 10 psi
Stage II	JWT ECU upgrade & boost jets	365-380 hp 12-14 psi
Stage III	B&B test pipes & Gut pre-cats	385-400 hp 12-14 psi
Stage IV	Performance cat-back exhaust system	400-415 hp 12-14 psi
Stage V	EVC	420-435 hp 15 psi
Stage VI	JWT NOS system	490-505 hp 15 psi
Stage VII	Larger intercoolers	495-510 hp 15 psi
Stage VIII	JWT dual POP charger	510-525 hp 15 psi
Stage IX	Ported throttle bodies & Matched intake	515-530 hp 15 psi
Stage X	NISMO 555cc injectors	530-545 hp 17 psi
Stage XI	Sport 500 turbos  Sport 600 turbos  Sport 650 turbos (cam upgrade required)	555-575 hp 17-21 psi  560-605 hp 17-21 psi  620-675 hp 17-21 psi
Stage XII	JWT cams & SGP head package	640-695 hp 17-21 psi

 
The standard stage chart for NAs:
 

Stage:	Modifications Required:	Approximate M-T HP at Flywheel
Stock	None	222hp
Stage I	Performance cat-back exhaust system	234hp
Stage II	Computer Upgrade & Intake	254hp
Stage III	Nitrous Oxide & Injector Upgrade	300-320 hp

 
Again, SGP Performance has created a more up-to-date NA performance upgrade path to follow:
 

Stage:	Modifications Required:	Approximate M-T HP at Flywheel
Stock	None	222hp
Stage I	JWT POP charger & Underdrive pulley	238 hp
Stage II	JWT ECU Upgrade	250 hp
Stage III	Performance cat-back exhaust system (also ALC for A-T)	262 hp
Stage IV	Stillen headers	279 hp
Stage V	Ported throttle bodies & Matched intake	290 hp
Stage VI	Injector upgrade & JWT NOS system	390 hp
Stage VII	SGP head package (porting & 5 angle valve job)	420-430 hp

 


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Sway Bar
A sway bar is connected to two points on the suspension, across the frame, from left to right. Their use results in less body roll and a stiffer suspension.

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Test Pipes
See Downpipes/Testpipes.

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Throttle Bodies
Connects intake piping to intake manifold. Throttle position sensor and throttle position switch are attached. Contains a butterfly valve - when the accelerator is pushed down it pulls a cable which is connected to the thottle body, which causes the valve to open, allowing air to flow into the engine.

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TPS-Throttle Position Sensor
A sensor connected to the outside of the driver side throttle body that feeds information back to the ECU telling it where the throttle position is. The connections on the TPS can often get dirty and cause an erratic idle. Cleaning the TPS connector can often cure idling problems.

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Turbos
Basically, a turbo is an exhaust-gas driven air pump. Exhaust gases exit the engine, run through the turbine section of the turbo, spin the turbine, and then exit the vehicle through the exhaust system. The turbo's turbine is connected via a shaft to the turbo compressor. The compressor is spun by the turbine, and compresses intake air to the engine. As the intake air is compressed it is made more dense. Because the air is more dense, more air, and therefore more oxygen, flows into the engine on each intake cycle. The engine's ECU measures the air and adds the correct amount of fuel. Therefore, compared to a normally-aspirated (NA) engine, more oxygen goes into the engine and more power is made.

The intercoolers come into play by reducing the temperature of the intake air after being compressed by the turbo, further increasing intake air density.

Turbo wastegates allow some exhaust to pass around the turbo's turbine under certain conditions (i.e., to avoid over-boosting the engine).

The shaft connecting the turbine and compressor is supported by an oil-lubricated bearing. This bearing cavity is cooled using engine coolant. When people talk about letting a turbocharged engine idle for a bit after start-up and prior to shutdown, it's due to this bearing.

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Turbo Timer
A Turbo Timer is an electronic device that will allow your engine to keep running AFTER the ignition key was turned OFF and removed, either for a preset amount of time (most of them), or a computed amount of time (based on how "hard" you drove)

Some of them have additional functions (like a boost gauge) They may require electrical skills to install them if the car is fitted with an auto-activating alarm, or if they aren't provided with a wiring harness for installation

They will prevent the common mistake to simply shut down a turbo engine after a "hot" run. If the engine is directly shut down, oil will stop flowing, may "cook" in the turbos and this may damage the turbo's bearings.

It's a "nice to have" gizmo, but not absolutely necessary if...

- You let your engine idle down from 30 secs to 2 mins before shutting it down

OR

- You do NOT engage the boost for the last 2 minutes of driving before stopping the engine

- Use of 100% synthetic oil will greatly reduce the risk of "cooking" your oil (but you'll still have to let the car idle)

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Underdrive Pulley
An underdrive pulley is a pulley that is smaller in diameter than the pulley it replaces. The diameter of the crank pulley is reduced a specific amount (from 20-30%), depending on the vehicles accessory needs. In other words, all accessory minimums are retained: air conditioning efficiency, power steering feel, and voltage (minimum allowable voltage 12v), even at idle, with everything on in the car. With the smaller diameter of the pulley the car will rev up quicker.  Weight loss is the most critical factor in HP production, each lb. of mass taken off the crank/eccentric shaft is worth approximately 2.7 HP and the figure increases with forced induction and as RPM's increase.

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Valence
Basically the rear bumper & ground effects, some aftermarket body kit suppliers have bumper replacements or a bumper 'cap' that covers the bumper area & adds different ground effects.

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Welding Tips
See Boost Jets/Welding Tips.

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X-Pipe
A new style of exhaust pipe between the main cats & the mufflers sections. The left & right side pipes actually come together in an 'X' fashion for better exhaust pulse blending.

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Z32
Nissan's model designation for the '90+ 300ZX. The '84-'89 300ZX is the Z31.

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Sources used on this page:

• Members from Twin Turbo.net
  
  • Dallas DamonZ
  • Kyle(Houston)
  • Henri Le Hir
  • njttz
  • Steven(Phx)
  • PWS
  • Joe VA
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