Besic / Jim Steck Supercharged Bonneville Engine


A Conversation with Jim Steck regarding the 2002 Besic Supercharged Bonneville engine.

Air box: Is this an air to air, water to air or...intercooler? Or do you feel one is not needed?

The intercooler is water-to-air. It's more efficient for it's size than air-to-air. You can get by at low boost without an intercooler by reducing compression ratio and timing...always a trade-off somewhere. Without an intercooler, the engine will make less Hp at the same boost, because the charge temperature will be higher...1% loss for each 10 degrees increase in charge temperature. Since the water-to-air units can be
mounted directly to the engine, the intake system is more compact...which is good for throttle response.

Front bracket: Guessing it holds a small Japanese (Nissan?) alternator. If so, would it provide enough poop for a 'regular car with heater, radio, etc?

There is no alternator on this engine...but there is just enough room to install one close to the original position. The little Nippondenso alternators put out 60 amps...more than the stock Alfetta. I put one on a customers turbo Alfetta with air conditioning...more than enough power. The cars are fairly simple, without big power draws. It's from a Geo Metro. Normal is 50
amps, and air conditioned cars have a 60 amp unit...integral voltage regulator and cheap. Make sure you get the 3-pin connector with it.

What fuel induction system are you using on this engine?

I'm fond of Electromotive. I've had very good luck with them and they were the first reasonably-priced system to integrate fuel and ignition management. They get the job done and have been completely trouble free. The only failure I had was a magnetic pickup that I adjusted too close to the crank. Would you believe the end of the crank moves +/- 0.015 inches? The intake manifold is from a Bosch spider, with a custom fuel rail...I don't like the rubber hoses. Since throttle response is not really important at Bonneville, I mounted a GTV6 throttle body directly on the supercharger inlet eliminated the need for a compressor bypass valve, simplifying the whole system.

Are you using any particular exhaust headers on this engine? (Would love to see a photo of the complete engine from the exhaust side).

Just used the standard Shankle header on this one...that's what Besic provided. I don't think I have any photos of the exhaust side...before I got the digital camera. My favorite headers are the y-branch design built by Paul Spruell. I'm not sure they make any more Hp on a street engine, but the difference on a high-compression race engine is significant!

This was the first generation and all I did was build the intercooler, supercharger mounting and drive and the engine management. Internally, Mike built the engine to my specs including having a set of piston-cooling
nozzles built and installed.

(continued on next column)

Guess as to HP at the flywheel?

No guess, horsepower was 364 @ 7800 RPM. The problem with this engine was the Vortech supercharger. It wouldn't live at the rated boost of 24 psi. I blew up two of them in less than 2 hours on the dyno. At something more streetable, say 15 psi, the Vortech would probably run forever. At 15 psi, it made almost 275 flywheel Hp on a very pessimistic dyno.

Are you available to make / fabricate any of the custom features of this engine (or a complete turn key engine)?

I'll make pieces or put together and dyno a complete engine. The fabrication is what I like best. I usually model the custom parts in solids first before cutting any metal. Equal-length headers for the Bonneville turbo would not have been possible if I hadn't built the math model first. (Bonneville Turbo engine) After it was done, all I had to do was cut the straight sections to length and the bends to the correct angle and weld them together...none of the frustrating and time-consuming trial and error (and scrapping) of pre-computer days.

The rendering is just to show you what the header model looked like before I broke it down into straights and bends for fabrication.

I assume you add air conditioning compressors to all of the Bonneville engines. Yes, I'm kidding.

No, but after sitting in a four-layer suit for 20 minutes, Besic would probably appreciate it. We're circulating ice water through the intercooler...from a Coleman ice cool the charge. If I had to wear that suit, I'd buy a cool vest and hook it up to the intercooler system. FWIW, we melt almost 20 lbs of ice per run...a little more than 2 minutes under power.

What are your views on supercharging a Twin Spark engine?

This is a better setup for high output than the single plug engine. The intake port, in particular, has a much higher flow more power can be made at the same boost level. The shape of the combustion chamber is also better and requires less ignition lead.

For modest boost levels, the old single plug head is almost as good. Detonation is the problem on street-driven cars. The best unleaded pump gas is only 94 octane and 12-13 psi is all the boost it will take with a 7.5:1 CR. If the head is ported, even less boost can be better ports don't get you that much.

I've heard that the TS head is more prone to cracking because of the extra plug. I don't know because I have no experience with a supercharged one yet...but I have a couple engines and one of them will be force fed.


PS Didn't know how much you like superchargers. A turbo will always make more horsepower, but the supercharged engine will always sound better...nothing sounds better than a supercharged small bore engine. I'm planning a supercharged 2.0 (Eaton M90) for my '60 Giulietta Sprint.

To contact Jim Steck

Steck Bonneville Turbo Engine + TS Parts | Supercharged GTV | Steck 4-Cylinder Engine Adapter
More Conversations with Jim Steck

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