Early 420a Research by Bill Hahn

Article located on Hahn Racecraft , I did pruchase a Fuel Managment Unit from them
http://www.hahnracecraft.com/auto/tech/dev.htm

Hahn RaceCraft's development program for the 420A engine began in early 1998. It started as a response to the inquiries we received from our 95-99 Diamond Star customers, whose non-turbo cars are equipped with this engine. They practically begged us to design this system! Little did we know at that time that we would be building over 450HP with this exceptional engine by late 1999.


Our first prototype vehicle for 420A Turbosystem testing was our own 1998 Eclipse RS. This long-term testbed vehicle was at first used to engineer our Stage I and II turbosystems. The components used in these systems were carefully chosen to offer excellent results while also allowing higher-powered options to be employed in the future. While the car underwent long-term evaluation of the turbosystem's effects, we worked in the background to create a foundation for the higher-powered future iterations.
During this period, we were surprised and pleased to learn that the 420A looked promising and amazingly modern when inspected internally. As it is a truly new engine (1995 was its introduction), its CAD design and contemporary design improvements were apparent upon close inspection. The design concepts we noted in the 420A suggested strongly that our current and future power and durability aspirations should meet with success:
A very strong bedplate four-bolt main lower end design appeared quite capable of handling much higher than stock HP. This bedplate design means the engine block actually separates into two sections along the crankshaft centerline, rather than the more conventional and much weaker practice of using separate main bearing caps. This design is typically used only on high output motorcycle or automotive (Suzuki, Viper, Porsche, Ferrari, etc.) engines.
Direct Crank Trigger ignition adds accuracy to spark timing. A strong, knife-edge crankshaft comes standard.
The Lotus-designed four valve cylinder head not only flowed well stock, it also exhibited excellent detonation control from modern port / chamber design and well executed cooling.
Mahle pistons, well known for their quality, added durability to the package. The more we analyzed this engine, the better it looked!
In the first year of testing, we studied the effects of our Stage I and II turbosystems on completely stock engines. This long term testing was crucial to determining the safe upgrade limits for these otherwise stock engines and drivetrains. Over thousands of street miles through all types of climates, with dozens of drag strip passes in between, our prototypes were put through their paces. The stock engines proved quite well suited to the 250 to 275 HP that our Stage II kit produces.
After a year of successful turbosystem and durability development with the stock engines, the time had come to explore the next level. With a target of 375-400 HP, new engines were prepared with forged pistons and billet connecting rods. One was installed in our Eclipse, another in the Neon. These units were carefully assembled, but were intentionally left otherwise completely stock except for the pistons and rods. We also upgraded the fuel systems to full programmable units, while adding a more powerful ignition amplifier. These changes allowed the turbo and intercooler that are standard in Stage I and II systems to run higher boost and produce their maximum airflow of almost 400HP.

We then power was sufficient to land our 2400 lb. Neon squarely into the 11.7 second /119-mph quarter mile range, while still maintaining daily driveability. As a matter of fact, this car has always been driven, not towed, to the dragstrip! The engine proved quite docile, yet still very willing, during street use on pump gas at low boost. The addition of higher-octane fuel and higher boost allows 400HP, all while retaining daily driven dependability. The performance value of the Neon was stunning: the total investment, including the purchase of the 1996 car, was still under $15,000 for a genuine, daily-driveable, late-model eleven second car which still gets great gas mileage in daily driving! The performance per dollar approaches that of a modern sportbike. Needless to say, the Neon was responsible for a lot of jaw-dropping at the local dragstrips.

The next step in power, was tested with our Eclipse RS. In addition to the fuel system and engine internal mods, we added a larger intercooler and converted the turbo to Super 20G specs. Remapping of the programmable fuel system we had previously installed allowed us to take advantage of the additional airflow provided by the larger turbo and front-mounted intercooler. Here the 420A engine proved itself yet again: it was now producing 450+HP, enough to propel the 2900 lb. Eclipse to 122 MPH in 11.7 seconds. Yet the car is compliant and cooperative in street driving, still wears air conditioning and goes anywhere!

It is important to note that our 375+HP Neon and 450+HP Eclipse 420A engines are still stock in terms of airflow. For the sake of turbosystem economy and simplicity, as well as good street manners, we decided to explore the maximum amount of power available while still blowing through a stock throttle body, intake manifold, cylinder head, cams and valves. The outcome is impressive, to say the least. Although the durability improvement provided by the piston and rod upgrades is essential to the use of these engines over 300HP, the pistons and rods do not help produce more power. The power gains are strictly achieved through the capabilities of the HRC turbo and fuel systems. 450+HP is enough for most, and readily achievable. Yet a brave few will try to imagine what results could be achieved with the addition of cylinder head / manifold improvements!
For Hahn RaceCraft, the next step will be to do just that. Our continuing development of the 420A will now explore what we can achieve when we are not limiting ourselves to the 450 or so HP airflow of the stock components. Moving effectively to the next level prompts us to finally take off the stock manifold and other parts that had performed so well to date. It's a bittersweet moment, for while we look forward to the huge power gains enabled by the new parts, we will miss the outright simplicity, ease and affordability of the stock parts. No matter. In order to maintain our position as the authority on these engines under high output, we will now forge ahead to ever-higher power levels. The information learned as we cross the 500HP mark will continue to benefit all of our 420A Turbosystems and engine components. We plan to persist until we have achieved the 400+HP per liter of engine displacement we have achieved with some of our other notable engine programs.
P.S.: The transaxle these engines are coupled to is a nice piece in its own right. Its durability definitely makes the engine's strong points even more viable. In the worst case scenario we've been able to come up with, our 98 Eclipse RS has withstood thousands of miles of turbocharged street use and 11.7 second quarter miles. It weighs about 2900 lbs. with driver and has a completely stock transaxle, uses slicks at the track and has had ZERO transmission issues. I've never missed a gear in it in over a hundred dragstrip passes. It's a perfect marriage with the Stage IV clutch we provide. I drive it hard, and if it holds up to what I dish out, then it's a durable gearbox! The fact that the stock components have held up to this brutal power level for so long is evidence of the durability that you can expect.
Of course, it has been my intention to push these components to their limits and beyond. This is the best way for us to understand what you, the buyer, will ultimately need to know about these cars and their capabilities when power is increased. If you are considering drag racing your car as continuously as we have run the RS, we heartily recommend a limited slip differential, and a training session from one of our drivers to teach you how to get that Hahn RaceCraft power to the pavement effectively while maintaining good drivetrain life. We'll gladly show you what we've learned about extending drivetrain durability and traction effectiveness. We believe it's the best way to make your experience with our equipment even more enjoyable. We have the information. That's why we drive, and race, what we sell!
Thanks,
Bill Hahn Jr.