Paul said:
Car and Driver put a turbo on an Opel back in the mid 70's. They went the low pressure, about 6 psi, route. The were looking for hotter performance coupled with improved emmisions. They were able to achieve BOTH. Someone on this list or the Classis Opels Group bought this car a year or so ago. If you wanted to go that route yourself, verses buying the set-up from TGSI, it might be a good place to start.Paul
As might be expected with turbos, the C & D car had its' boost turned up a bit higher, and ended up blowing all the rings out. The current owner Craig Roberts had to replace the shortblock because of this.
The problem is, carbureted turbos do not have very good fuel atomization. In fact, I'd completely put the idea of a carbureted turbo out of your mind. If you do a draw-through system, the carb can remain stock, but you can't intercool it.
If you go blow-through, you can intercool it, but then you will be pressurizing the carb. So, you will either have to build a leak-proof box around the carb, or re-engineer it to be pressurized. It will leak air past the throttle shafts, and the power valve vacuum port will have to be repositioned to accept vacuum from BEFORE the turbo (or you will pressurize the power valve and force fuel back into the carb....leaning it out under boost), and you will need to use a rising-rate fuel pump/regulator. If you have a fuel pump with 5 psi fuel pressure, and you boost 5 psi...you will cancel the fuel pressure out, forcing fuel back into the fuel lines. You want to have a pump capable of feeding fuel pressure that is as high as your boost levels are, PLUS the fuel pressure the carburetor need normally (3.5 psi for a Weber).
Another concern is older distributors have WAYY too much ignition advance...you'll pop a motor in no time if you have the 'wrong' distributor for a turbo. Also, a higher energy ignition is mandatory. An ignition has to work much harder to strike up your plugs under pressure.
In my opinion, the only way to go is with fuel injection. However, I would NOT use the standard Opel fuel management. It is woefully inadequate for a turbo application, at least the older analog L-Jetronic fuel injection. I am building a turbo engine for my Ascona wagon. I am using the 1975 fuel injection intake manifold.....that's all. The rest will be custom. I will have injectors that are over 80% larger to handle the increased fuel requirements of a turbo. I will have a larger capacity fuel pump (110 litres per hour), a larger (custom) fuel rail to feed the injectors, a larger 65 mm throttle body adapted to the stock intake, and a stand-alone programmable ECU (this eliminates the stock restrictive MAF).
Besides the changes above, I still need the turbo, the wastegate (integral), a custom exhaust manifold, a custom exhaust, an intercooler, intercooler tubes and silicone connectors, a blow-off valve (not necessary for low boost applications but a good ides nonetheless), a larger radiator to help with heat dissipation, an oil cooler, a modified oil pan for the oil drain-back line for the turbo, etc, etc.
Initially, I'll be installing all these components on a stock 1971 engine with very low mileage. I KNOW it will pop eventually, I'm simply curious as to 'when' this will happen, and it is a testbed for the operation of the fuel/turbo system until I can build a proper reinforced shortblock and a better cylinder head with stainless valves and adequate valve springs.
My goal is to put around 10 psi of boost into the modified engine, with the capability to run 15-16 psi as needed. This should net me around 260-275 hp reliably. HOWEVER, be forewarned that it will not be inexpensive to undertake something like this, and there's a lot of fabrication involved. My estimates so far are $3100 for the turbo stuff and management (the turbo is dirt cheap because I got an almost new turbo and intercooler from a friend, otherwise add another $1000 to that figure). It'll cost me another $1400 for a short block (all my labor), and another $1200 for the top end of the engine (again my labor). Then there's all the turbo manifold/exhaust/intercooler fabrications.....my labor, but if you paid someone for all the engine labor, fabrications, programming, dyno time (I also get dyno time for free), and didn't get a deal on the turbo, it'll cost about 40% more than my prices.
This is NOT cheap to do, but if you go the cheap route, then pop the motor, then build a new one, then pop it again....which one makes more sense to do?
Bob