General 2.3 Liter Turbo / SVO Modification FAQ

This FAQ was compiled by members of the SVO list. Please link to it, but don't copy it, especially without credit. It's not going anywhere, and will be updated as things are proven to work (or not).

This FAQ is aimed at all 2.3 turbo cars, but has specifcs for SVOs. These suggested mods are presented in the order that most people would implement them. This is dependent upon money available, and level of difficulty.

You've got to use your ears and your brain to avoid detonation and broken parts. If you detonate heavy for more than a couple of seconds, you could be looking at an expensive engine rebuild.

Fuel Injectors

SVOs came in two flavors; 84-85.5 (early) and 85.5-86 (late).

84-85 SVOs, and other turbo cars prior to 85, have smaller injectors, green in color, that are rated at 30 lb/hr of fuel flow. This will become a limitation pretty quickly, if you intend to modify the car to go faster.

85.5-86 SVOs, and all Merkur XR4tis, have larger injectors, brown in color, that are rated at 36 lb/hr of fuel flow.

Results will vary, but you can run in the mid 90s MPH, in the quarter mile, on the 30# injectors, about 230 HP, or a few mph over 100 MPH, in th quarter mile, on the 36s, about 300 HP.

With nitrous and some creativity, a lot more is possible.

EEC-IV variances

Merkur XR4ti, SVO, and pre 87 Turbo Coupe EEC-IV computers are pretty much interchangeable without massive wiring mods, although some differences exist. The 85.5-86 SVO computer is the best one that is easily installed. The 87-88 EEC is all out best but there's a lot of wiring to be changed and a few sensors to be added. Do not use an EEC from a car that had an intercooler, on a car without an intercooler. The timing is too agressive. You may even go slower.

On 85.5-86 SVOs, or cars equipped with Rapido's SVO Plus computer, disconnect the knock sensor. It WILL slow you down. On one 84 SVO, the car was slower with it disconnected. You will have to test and see if this helps, or hurts your combo.

If you disable this safety device and blow up your motor, it's your fault.

Boost: The boost can be turned up at any time, but results will vary based on modification level. Boost, alone, does not make power. Flow of air thru the motor does. Do anything you can to increase the amount of air the motor can flow. Cranking up the boost indiscriminately can destroy your motor. Top quality fuel should be used at all times, and detonation religiously monitored for. Some owners even have preferred brands of premium fuel, because of their experiences.

Exhaust: Make it as big as you possibly can. 3" single flows more than 2.25" duals. Use a 3" catalytic convertor if you can. Use a 3" downpipe. They are available for all models. This is the single biggest improvement you can make.

Gauges: Taking care not to hurt your motor can be made much easier by the purchase of an air/fuel ratio monitor. The Cyberdyne A/F gauge can be had, for $50 or less. This is highly recommended if you plan on modifying the car, at all, because it will allow you to have a baseline reading before modifications begin, and then you can read it when you get to the point of NEEDING to monitor it for possible trouble. You WILL need it as you approach the limits of the stock fuel system. An Exhaust Gas Temperture (EGT) gauge can be handy to see when you might be approaching too little fule, or retarded timing. These run over $100 with the required thermocouple.

Fuel System: You can't make power without air and fuel. As you increase the engine's ability to get air in, you have to keep up with more fuel. The turbo cars run REALLY rich to start with, so there is a little cushion in there, but lots of people have found out the hard way, that it's not much of a cushion. Since ALL of these cars are now almost 10 or more years old, get the fuel system up to snuff. For cars with intank pumps, upgrade it to 155 LPH or more. For cars with rail pumps, (Merkur and the early models of the other cars) these pumps seem to be a bit beefier, and the fuel pressure doesn't sag as much, when the boost is cranked up.

Step By Step Modifications

Stage 0:

1. Get the car running right. New ignition wires, plugs, cap and rotor. Ford parts are recommended, and cheap. Wires should be replaced every 6 months to keep the car in top tune. Set the timing to factory specs.
2. Put decent tires on it. Or slicks, if you intend on making further modifications. and need a consistent baseline.
3. Take it to the strip and get a baseline number for it! At sea level, an 85.5+ should run a low 15/high 14, and an early model should run a mid-low 15.

Stage 1:

1. K&N Air filter on the end of the VAF meter. Take off the stock air box $30-$50
2. Turn up the boost till the overboost buzzer just comes on, this is about 17.5 psi OR set it wherever you want (see fuel meter again) ;-). $5-$500
3. The best number heard of so far, for an SVO at this stage was an 86 that ran a 13.75 on slicks.

Stage 2:

1. Big exhaust $200-$1000
2. Engle cam for 85.5 and earlier SVOs, or the automatic cars, if it's not an SVO. $150
3. Cam degree wheel, for tuning the cam timing. For more top end charge, retard it 4 or more degrees. You can move the powerband up and make the turbo "work harder" with this method. Supposedly you can go faster in the quarter on the stock cam with a degree wheel.
4. Tbird Intercooler (optional, save your money for a serious one if you're going to go farther than stage 2) $50-$150, from a junkyard. This is even an improvement over the stock SVO piece.

Stage 3:

1. Late model SVO computer and injectors for owners without this calibration $300 When, and if, this becomes a requirement will depend on a lot of things, but generally, if you're running 95mph or more in the quarter mile in a stock weight early SVO (~230hp), it's time to upgrade to this level. For some people this may happen before the cam change.
2. Late model SVOers (and those others with only an in-tank pump) may also want to consider going to a higher flow fuel pump at about this point. The early model double-pump system should be OK for most applications. If you're going to use nitrous at some point, go all out on the fuel pump(s).
3. At this point, you should have gained at least 5 or 6 mph, and half a second off your baseline time. Typical gains would be closer to a full second, if for no other reason than that you should be getting to be a pretty good driver by now ;-).

Stage 4:

1. GOOD intercooler $250-$1250. For the SVO, the Spearco SVO specific model is tops, with claims of an additional 20 hp on a stock 86 SVO. For the Merkur, Nick makes a nice piece that's a bolt on.
2. High flow turbo $400-$1200
3. Ported intake and exhaust manifolds FREE-$1000

Stage 5:

1. All out ported head/big valves/maybe a bigger cam FREE-$2000

Stage 6:

Parts exist to do an all-aluminum 3 liter 8000RPM stroker motor if you want to go nuts. This will require more fuel than the 86 system can provide. Currently you're on your own for such things... BIG BUCKS!

Other things like underdrive pulleys ($50) and cam timing pulleys ($50-$100) can be played with as desired. Prices vary depending on the deals you find, and how much of the work you can/will do yourself. There's always nitrous for those who are inclined to deal with it, and to take the necessary precautions.

Send updates, comments, suggestions to Dave Compton