2.3 Turbo Frequently Asked Questions

All information given below are general guidelines. Each car or engine is slightly different and may require additional tuning for safe/optimal performance.

How much boost can I safely run on 91 octane?
These are general guidelines only. Always test with windows up, muffled exhaust, radio off, etc. so you can listen for audible detonation. Detonation sounds like gravel rattling in a tin can down near the back of the engine. If detonation is heard, get out of the throttle and lower boost or timing until it goes away. Since there are so many factors that effect this, I'll try to cover as many as I can but keep in mind that every vehicle is different and many other factors besides those mentioned below will effect maximum allowable boost.

-Assuming no intercooler, stock timing with an early (not LA or PE series) ECU.
14-16psi.
-Assuming stock intercooler, stock timing with an LA or PE series ECU.
17-20psi.
-Assuming large efficient front mount intercooler, stock timing with an LA or PE series ECU.
19-24psi.

Other factors to consider:
-93 octane should allow additional 1-2psi, 89 octane will lower max boost 2-3psi, 87 octane will lower max 3-5psi.
-Small or inefficient intercooler (Volvo, Saab, Probe, etc.) should lower max boost 3-6psi.
-Cold air temps may raise max boost 2-4psi.
-Hot air temps may lower max boost 2-4psi.
-Water/Alcohol injection can raise max boost 2-8psi.
-Larger than stock turbos may raise max boost 2-4psi because of increased compressor efficiency.

How much power will the stock LA series ECU handle?
In general terms, about 300rwhp. This will require elevated base fuel pressure, elevated boost, and other airflow mods before this power can be achieved though.
Early ECU's running 30lb injectors or small air meters will support significantly less power.

How much power will the stock 35lb injectors handle?
In general terms with stock fuel pressure, about 250rwhp, though you can push them to ~300rwhp if using elevated base fuel pressure.

How much power will the stock large vane air meter (VAM) handle?
In general terms, about 300rwhp. It's actually quite a restriction at anything over about 240rwhp and people have pushed them to nearly 400rwhp, though it's like sucking a cheeseburger through a straw at this point.

How much power will the stock turbo engine handle?
With stock crank, rods, pistons, etc., many people have safely ran them in the 400-430rwhp range for quite a long time. A few people have made 515-550rwhp for a while before throwing a rod. 

Can I convert my air meter to blow-thru?
Yes, it is possible, though I wouldn't suggest it without a means of monitoring the Air/Fuel ratio with a Wideband Oxygen Sensor such as one I use from http://www.innovatemotorsports.com 

Can I use a n/a head on a turbo motor?
Yes, you can, though I'd suggest you port the chambers to remove most of the "heart" shape so it more closely resembles the stock turbo head's "D" shaped chamber. You will also need to upgrade the exhaust valves.

Can I just put forged pistons in my stock 2.3 n/a engine and convert to turbo?
Yes, though I'd suggest you still do the swap as if you were dropping in a complete 2.3 Turbo engine as far as wiring, air meter, injectors, etc. go.

What spark plugs should I use?
Stock Motorcraft plugs for 2.3T engine.

What should I gap the spark plugs to?
-.032"-(10-15psi).
-.030"-(16-20psi).
-.028"-(21-25psi).

What spark plug wires should I use?
Motorcraft. Parts store brand wires and many more expensive wire sets cause issues under boost.

Can I use a small air meter/injectors with a computer that came with large air meter/injectors (or visa-versa)?
No. You must use the same size air meter and injectors as came with the ECU from the factory.

What options do I have for tuning/modifying the computer settings?
-EEC-Tuner (link) 
-J3 (links)
-PCMX Software (links)
-Tweecer (link)

EEC-Tuner or J3 adapter both have the same function, they can do all the same things. They plug into the stock ECU's service port and basically "interrupt" the signal to the ecu.
They are tuned with a computer (laptop or pc). They are not tuned "on the fly" meaning the engine is off during tuning. You can adjust "anything" that the ecu controls, rev limiter, injectors, timing, etc...anything you can dream of really.
The main difference between the J3 and the EEC-Tuner is that the J3 uses and external chip burner while the EEC-Tuner is self burned, meaning the "burner" is part of the Tuner board. The J3 uses removable chips that can have different tunes burned onto them for easy swapping of tunes without a computer (at the track or something).
EEC-Tuner is 300 or so, J3 is ~65 bux plus the $50 burner. Both will require PCMX software to make the programming easy, it's about $150.

What other EFI tuning options do I have (Stand-alone EFI)?
-Megasquirt (link)
-F.A.S.T
-Holley Commander
-Accel DFI
-Big Stuff 3
-SDS
etc.

What is a wideband oxygen sensor and why do I need one?
Air/Fuel Ratio Primer: When air and gasoline are mixed together and ignited, the chemical reaction requires a certain amount of air to completely burn all of the fuel. The exact amount is 14.7 lbs of air for every pound of fuel. This is called the "stoichiometric" air/fuel ratio or 14.7:1 a/f. It's also referred to the Greek letter "lambda."

Lean mixtures improve fuel economy but also cause a sharp rise in oxides of nitrogen (NOX). If the mixture goes too lean, it may not ignite at all causing "lean misfire" and a huge increase in unburned hydrocarbon (HC) emissions. This can cause rough idle, hard starting and stalling, and may even damage the catalytic converter.  Lean mixtures also increase the risk of spark knock (detonation) when the engine is under load.

Rich mixtures: When the air/fuel ratio is less than 14.7:1, lambda also is less than one and the engine has a rich fuel mixture. A rich fuel mixture is necessary when a cold engine is first started, and additional fuel is needed when the engine is under load. But rich mixtures cause a sharp increase in carbon monoxide (CO) emissions.

By monitoring the level of unburned oxygen in the exhaust, the sensor(s) tell the engine computer when the fuel mixture is lean (too much oxygen) or rich (too much fuel). To compensate, the computer adjusts the fuel mixture by adding more fuel when the mixture is lean, or using less fuel when it is rich. That's the basic feedback fuel control loop in a nutshell.

Narrow Band Sensors (Stock): The stock oxygen sensor used on most vehicles is referred to as narrow band. This is because it is designed to only be accurate over a very narrow band of air/fuel ratios. They are not useful for performance tuning. The reason is, conventional oxygen sensors give only a rich-lean indication. They can't tell the computer the exact air/fuel ratio. When the air/fuel ratio is perfectly balanced, a convention O2 sensor produces a signal of about 0.45 volts (450 millivolts). When the fuel mixture goes rich, even just a little bit, the O2 sensor's voltage output shoots up quickly to its maximum output of close to 0.9 volts.  Conversely, when the fuel mixture goes lean, the sensor's output voltage drops to 0.1 volts. Every time the oxygen sensor's output jumps or drops, the engine computer responds by decreasing or increasing the amount of fuel that is delivered. This rapid flip-flopping back and forth allows the feedback fuel control system to maintain a more-or-less balanced mixture, on average. 

Wideband Sensors: The newest generation of oxygen sensors are being called "wideband" lambda sensors or "air/fuel ratio sensors" because that's exactly what they do. They provide a precise indication of the exact air/fuel ratio, and over a much broader range of mixtures - all the way from 0.7 lambda (11:1 air/fuel ratio) to straight air.

When the air/fuel mixture is perfectly balanced at 14.7:1 (the stoichiometric ratio and lambda equals 2), the sensor produces no output current. When the air/fuel mixture is rich, the sensor produces a "negative" current that goes from zero to about 2.0 milliamps when lambda is 0.7 and the air/fuel ratio is near 11:1. When the air/fuel mixture is lean, the sensor produces a "positive" current that goes from zero up to 1.5 milliamps as the mixture becomes almost air.

Widebands and Performance Tuning: Many performance engine builders and tuners have discovered the benefits of using the wideband oxygen sensor technology to monitor air/fuel ratios. Being able to see the actual air/fuel ratio at any given instant in time allows the fuel mixture to be fine-tuned and adjusted on the fly - something which previously could only be done on a dynamometer using expensive equipment.  

The air/fuel ratio is critical with high performance, turbocharged and supercharged engines to make power and to keep the engine from leaning out at high rpm and boost pressures. If the mixture leans out, it can send the engine into self-destructing detonation. If it is too rich, it will lose substantial power and create excess heat.

Target Air/Fuel Ratios: Typically, naturally aspirated engines make best power in the 12-13.5:1 range under load. Turbo engines are typically safer in the 11.5-12.5:1 range under load. Each engine is different however and the best ratio for your particular combo may not fall within these ranges. These engines should still idle and cruise at near 14.7:1 a/f ratio for best fuel efficiency and minimal emissions.
Source: Bosch Wideband Oxygen Sensors Precisely Measure AirFuel Ratios

What is the purpose of a blow off valve (bov)?
The Blow-Off valve (BOV) is a pressure relief device on the intake tract to prevent the turbo's compressor from  surging from the backed up pressure waves caused by a suddenly closed throttle. BOV's do not control boost levels. The BOV should be installed between the compressor discharge and the throttle body. When the throttle is closed rapidly, the airflow is quickly reduced, causing flow instability and pressure fluctuations. Airflow bounces off the throttle plate and the pressure waves can reverse direction. These rapidly cycling pressure fluctuations are the audible evidence of surge. Surge can eventually lead to thrust bearing failure due to the high loads associated with it. The BOV releases these pressure waves into the atmosphere when the throttle is closed during shifts or deceleration, creating an audible "woosh".
Blow-Off valves use a combination of manifold pressure signal and spring force to detect when the throttle is closed. When the throttle is closed rapidly, the BOV vents boost in the intake tract to atmosphere to relieve the pressure; helping to eliminate the phenomenon of surge. Source: TurboByGarrett.com - Turbo Tech101

What is the purpose of a bypass valve (bpv)?
The Bypass valve (BPV) performs the same function as the BOV above. The only difference is the air is recirculated back into the intake tract in front of the turbo, not released to the atmosphere. The BPV recirculates excess air when the throttle is closed during shifts or deceleration, creating a muffled "woosh" sound.  Source: TurboByGarrett.com - Turbo Tech101

What is the purpose of a wastegate?
On the exhaust side, a Wastegate provides us a means to control the boost pressure of the engine. The vast majority of gasoline performance applications require a wastegate. There are two configurations of wastegates, internal or external. Both internal and external wastegates provide a means to bypass exhaust flow from the turbine wheel. Bypassing this energy (e.g. exhaust flow) reduces the power driving the turbine wheel to match the power required for a given boost level (speeds up or slows down the turbo). Similar to the BOV, the wastegate uses boost pressure and spring force to regulate the flow bypassing the turbine.

Internal Wastegates are built into the turbine housing and consist of a “flapper” valve, crank arm, rod end, and pneumatic actuator. It is important to connect this actuator only to boost pressure; i.e. it is not designed to handle vacuum and as such should not be referenced to an intake manifold.

External Wastegates are added to the exhaust plumbing on the exhaust manifold or header. The advantage of external Wastegates is that the bypassed flow can be reintroduced into the exhaust stream further downstream of the turbine. This tends to improve the turbine’s performance. On racing applications, this wastegated exhaust flow can be vented directly to atmosphere.

source: TurboByGarrett.com - Turbo Tech101

Should I use an internal or external wastegate?
In general, street/strip vehicles with stock turbos or small hybrids in the middle of their power range can use internal wastegates without issue. As the power limit of the turbo is reached (bordering on being too small), and internal wastegate will become less reliable at controlling boost. If the exhaust side of a turbo is being pushed near the limit, an external wastegate should be used. Also in setups where an external wastegate will simplify installation, or those getting over 350rwhp, and external gate should be used.

Will 3" exhaust kill my low end power because it doesn't have enough backpressure?
No. The turbo creates more than enough backpressure for the engine. The best turbo exhaust is the least restrictive possible. This includes large tubing, mandrel bends (not crushed in the bends), and a straight through muffler design.

What is the best size of intercooler tubing?
In general, the best size is that which minimizes size changes throughout the system. Considering stock 2.3T's have a 2" outlet at the turbo and a 2.5" inlet at the throttle body, using 2.5" tubing only requires one size change; from 2" to 2.5" at the turbo outlet or intercooler inlet. If a 65-70mm throttle body is used, 3" tubing from the intercooler to throttle body can be used, though it won't offer a power increase over 2.5" tubing.

Will too large of an intercooler or too much tubing cause excess lag?
Simply put, no. The amount of air contained in the tubing/intercooler compared to the amount of air the engine ingests every second is very minimal. The difference in lag between no IC tubing to a large FMIC will be hundredths of a second. In other words, it's not noticeable.

What clutch do I need for "X" hp?
Clutch needs will vary greatly depending on driving style, vehicle weight and usage, torque curve, and many other factors. These are just general guidelines. Of course you can always run more clutch than you need...it's better to have more than you need than not enough.
Up to ~250rwhp: Stock Turbo Clutch
250-300rwhp: Centerforce Dual Friction, Spec Stage I, Clutchnet Yellow, or most other entry level "performance" clutches (not stock replacement).
300-350rwhp: Clutchnet Yellow disc with stock pressure plate.
350-450rwhp: Spec Stage III, Clutchnet 3 Button "Red" disc with stock pressure plate.
400-500rwhp: Spec Stage III+, Clutchnet 3 Button "Red" disc w/Red pressure plate.
500+rwhp: Dual Disc (at this point an Auto trans will start to become a better option for 95% of the cars).

Can I use the stock Mustang fuel pump with my new turbo engine?
If you leave the engine stock with only a few basic mods...cone filter, slightly elevated boost, etc. you can most likely get away with it because the stock Mustang pump is the same size as the stock turbo pump. If you plan to make 250+rwhp, see below.

What fuel pump should I use for my modified 2.3T?
Walbro 255 liter/hour High Pressure for 87-93 5.0 Mustangs. Early SVO's and such with inline pump (not intank) must either convert to intank pump or get inline Walbro 255 pump.