WARNING!!!!
See note at bottom.
ONE WAY TO TURBOCHARGING V4 SONETTS
by: Walter Taucher*
Turbocharging is pressurizing a motor with an exhaust driven compressor. The turbocharger is not mechanically connected to the engine.
On my particular installation, the turbo produces boost from 2800 rpm up to a maximum of 10-12 psi boost at 4500-5000 rpm. The Saab V4 is a durable and torquey motor and takes to the turbo very well. The turbo kicks in smoothly, giving the engine the ability to rev freely from 2800 rpm to as far as the tachometer will read. With the turbocharger the car idles just like a stock Saab, gets over 20 miles to a gallon, is very quiet, and goes like gang busters. This set-up makes even the steepest road seem level.
The turbocharger I am using on my Saab is made by Rajay Industries Inc. It is a model 377B with a .25 A/R turbine housing. The motor is a stock 71 1700cc V4 with an 8:1 compression ratio. This Rajay 377B 25, as it is widely known, is available at most diesel truck supply shops at a cost of approximately $300-$400. On my installation the turbo was mounted behind the engine, since that was the only place where there was enough room to fit.
Keep in mind that your engines’s compression ratio must not exceed 8:1 and that your engine must be in good shape. A motor with worn piston rings or bad valves will not benefit from the use of a turbocharger.
Briefly, this is how to duplicate my installation.
PREPARATION:
Remove the carburetor, the heater hoses that criss-cross over the transaxle, the windshield washer pump, and the exhaust system (front half only). Hang the turbocharger with wire from the radiator fill tube, positioning the turbo with the compressor outlet facing in between the left valve cover and the distributor. The top of the turbocharger should be against the radiator fill tube. This is where the turbocharger will reside.
EXHAUST SYSTEM:
With a little ingenuity you should be able to use many parts from the stock exhaust system in this installation. With a 1 3/4" tubing, start from the front of the engine and route the exhaust around the engine so that it ends just below the turbine inlet of the turbocharger. Find or build a heavy gauge steel rectangular tube with these approximate dimensions, 2" x 4" x 5". This type of tubing is sometimes used in the construction of custom automobile frames. Drill a 1 5/8" hole on the 4" x 5" side. Align it to the turbine inlet, making sure that the rectangular box you just made is parallel with the firewall. Mount three studs into the box and bolt this to the turbine inlet. Make on 1 3/4" hole in each of two 2" x 4" steel plates. Weld these over the ends of the rectangular box. Now weld the left exhaust pipe to the left 1 3/4 inch hole. Make a 2" x 4" oval shaped flange with a 1 3/4 inch hole in it and weld this to the right side of the exhaust pipe. Mount tow studs around the right 1 3/4" hole and drill two matching holes into the oval flange. Bolt the two together and you should no end up with and easily removable 2-piece exhaust header. Use asbestos gaskets for all exhaust parts.
INTAKE SYSTEM:
You now will need to somehow join the turbo compressor outlet to the intake manifold of V4. This is fairly simple. Start from where the carburetor originally was and snake a pipe form the carburetor to the compressor outlet of the turbo, ending 2" short of the compressor outlet. Weld the pipe to a vertical tube that is welded to a flange that is bolted to the intake manifold. Now connect this to the compressor outlet of the turbo with the large rubber hose supplied with the turbocharger unit.
CARBURATION SYSTEM:
Just about anything can be used here. I am using a Carter ball & ball-1 barrel downdraft carburetor form a 6-cylinder Dodge. This is not a very efficient set-up. I suggest a 1.5 inch venturi SU side draft carburetor. It is simple in design, inexpensive, and available at almost any foreign parts wrecking yard. With this carburetor, the cable accelerator linkage from a ‘63 6-cylinder Rambler should work with very little fabrication. The carburetor is bolted to the compressor inlet of the turbo, as the turbo sucks from the carburetor.
DETAILS:
Route the exhaust form the turbocharger turbine outlet towards the front of the engine, and out the hole your stock exhaust used to exit. Connect your turbocharger oil line from the motor’s oil pressure sender. Connect your oil drain straight across form the turbocharger to the valve cover with a ½" or larger diameter hose. The oil drain line should really be sloping downward from the turbo to the motor, but I have yet to have any oil sealing problems. If any one finds a better way to hook up your oil return line, please let me know about it. Run a copper tube from the top of the motor’s intake manifold to the vacuum advance of the distributor, and to the p0ressure gauge which you have installed in you car. The distributor will now advance with vacuum and retard with pressure. Move the radiator fill tube to the back side of the mounting tabs. Use the washers to give some clearance to the turbo. Mount the windshield washer unit lower on the firewall. Now re-connect the heater hoses making sure it does not touch any of the exhaust.
HINTS:
When installing your turbo, keep in mind:
1) Hood and body clearance.
2) Accessability of spark plugs, oil dipstick, transaxle plug and other maintenance items.
3) Wrap the exhaust with insulation material where it is close to your electrical relays.
4) Do not lug your engine at low rpm.
5) Do use premium fuel. If you are unable to find fuel with enough octane, you will have to rig up a water/alcohol injection system to slow down the burning of the fuel you are using.
6) Switch to a spark plug that’s at least two heat ranges colder. Gap the plug at .25 and experiment from there changing to different heat range plugs if necessary.
7) Your exhaust system should be a single 2" pipe all the way out back with a small resonator at the end. The turbocharger acts like a muffler, so there is no noise problem.
8) This particular system does not use a waste gate to control boost, but uses mufflers which are cheaper, less complicated, and more dependable. Keep your boost below 12 psi and you should not have to modify your engine internally. If you are experiencing too much boost, add more restrictive mufflers until the boost is down to the desired level.
9) If you are experiencing detonation or pinging, let off on the gas immediately or you run the risk of ruining your engine. This pinging is usually caused by over advanced ignition timing, or too much boost for the octane of fuel you’re using.
POSSIBLE PROBLEMS:
Lack of boost can be caused by:
1) Leak in exhaust system.
2) Worn valves or piston rings.
3) Carburetor too small. Ex. Stock Saab one barrel carb.
4) Too much exhaust restriction.
Other Problems: Possible Cause:
1) Poor throttle response: Dirty carb.
2) Plugs miss at high power: Gap too large.
3) Plugs miss often: Bad leads.
4) Oil leak into turbine housing: Blocked oil drain.
5) Poor idling: Air leak between carb. & compressor
Always use an air filter. A small hard foreign object can destroy a compressor or turbine in seconds. Use a good grade of oil and filter. If you decide that you want to turbo charge you Saab, I suggest that you read Turbochargers by Hugh MacInnes (HP Books) first.
* This information is posted without consent of the author.
PLEASE READ...... PLEASE READ>>>>
I'm currently working on exactly that project, and I have the same paper that
you posted on the page. One proviso to using those instructions is that they
are 20 years old. More, even - I think they were first published in '78.
Some of the products that they describe are not available anymore, and none
of the prices will be anything like accurate.
Another -MAJOR- issue is the placement of the turbo!!!! You're placing
something that mixes fuel and air UPSTREAM of a turbocharger. A turbo
produces ENORMOUS heat. (I'll send you pictures of exhaust manifolds / turbo
housings that are glowing white-hot, if you like.) It is NOT the safest
proposition in the world to build a suck-through setup on one of these cars.
You are taking SEVERE risks of explosion. The only even MARGINALLY safe
application of a suck-through turbo is in drag racing, where the course is
not long enough for the turbo to heat up to that degree. For any kind of
extended driving, however, it is TOTALLY not a safe thing to do. I was
contemplating it myself, until I called Weber to talk about carbs. The
fellow I talked to had built several turbo VW's, and had used a suck-through
system at one time, with nasty results. Suck through superchargers are a
much safer proposition - they do not have the heat of exhaust gas to reckon
with.
If you -do- post those instructions PLEASE post with them a disclaimer about
the potential of fire, explosion, and death associated with putting a
fuel/air mixture that close to several hundred degrees of hot gas and metal.
Gabe Conlon
'73 Sonett
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