Editing Quad 4 engine (section)

==Prototypes and experimental engines==
===Factory prototypes===
At the same time that Oldsmobile announced the planned high-output "HO" Quad&nbsp;4 in 1988, they suggested that a turbocharged version producing up to {{cvt|250|bhp|kW|0}} was planned. A turbocharged Quad&nbsp;4 with a reported {{cvt|200|hp|0}} was installed in an Oldsmobile 98 that was previewed by [[MotorWeek]]. A turbocharged Quad&nbsp;4 was never released as a production option.<ref name="jalopnik-mar2019"/><ref name="mw-feb2020"/>

The pace car for the 1988 Indianapolis 500 was an Oldsmobile Cutlass Supreme that had been converted into an open car by Cars and Concepts. The engine was a turbocharged 2.3-liter Quad&nbsp;4 built mainly with factory parts that produced {{cvt|250|hp|kW}} at 6400&nbsp;rpm.<ref name="wbody-1988pace"/>

The Oldsmobile Aerotech II and Aerotech III were both released in 1989. The Aerotech II is a wagon-back sports coupe concept with a 2.3-liter Quad&nbsp;4 making {{cvt|230|hp|kW}} with some form of forced induction. The Aerotech III is essentially a preview of the 1990 Oldsmobile Cutlass Supreme sedan, and came with a supercharged 2.3-litre Quad&nbsp;4 that developed {{cvt|230|hp|kW}}.<ref name="oo-concepts"/>

===Aerotech engines===
Even before the production Quad&nbsp;4 was released, Oldsmobile engineering's Chief Engineer Ted Louckes and Future Systems and Technology engineer Bill Porterfield had begun a program looking for more power and higher efficiency from the engine. Part of the project included building the Oldsmobile Aerotechs in pursuit of new land speed records. Two new twin-cam four-cylinder engines were built, based not on production Quad&nbsp;4 parts, but on a set of engineering parameters derived from the engine, which Oldsmobile referred to as the "production architecture." Under this scheme the derivative engines had to keep the Quad&nbsp;4's four-stroke combustion cycle, double overhead cams, multi-valve cylinder head and, significantly, {{cvt|100|mm|in|2}} bore spacing.<ref name="hrm-apr1987b"/>

====Batten RE engine====
[[File:Quad4-900-2.JPG|thumb|right|Batten RE engine with single turbo]]
The Batten RE engine was designed by Rudy Sayn and Andy Schwartz of Batten Heads in Detroit, and followed the restrictions set out by Oldsmobile. The engine's cylinder head, block, and sump are all of aluminum alloy, with the sump also able to handle structural loads. The RE also has an unusual coolant distribution manifold. The RE's designers retained the valve angles and sizes, pent-roof combustion chambers, dual chain-driven camshafts, and stock piston crown shapes of the production Quad&nbsp;4.<ref name="hrm-apr1987b"/>

The RE is a [[Cylinder (engine)#Sleeve|wet sleeve]] design, with four cast iron cylinder liners attached to an upper cylinder block deck plate. With a bore of {{cvt|3.5|in|mm|0}} and a stroke of {{cvt|3.1|in|mm|0}}, the engine displaced {{cvt|1955|cc|cuin|2}}.<ref name="hrm-apr1987b"/>

The electronic fuel injection system came from Rochester Products, while Delco Electronics provided the engine's high-voltage ignition system. The RE was fitted with a single turbocharger from [[Garrett AiResearch]].<ref name="hrm-apr1987b"/>

Output estimates for the Batten RE engine range from {{cvt|750| to |900|hp|kW}}. A Batten RE engine powered the short-tail Aerotech car.<ref name="oo-aerotech"/>

Applications:
[[Oldsmobile Aerotech]] short-tail

====Feuling BE engine====
[[File:Quad4-1000.JPG|thumb|right|Twin-turbo Feuling BE engine with one external port per valve]]
In Ventura, California, Feuling Engineering undertook development of an experimental engine subject to the same set of restrictions set by Oldsmobile. Feuling's design focused on thermal efficiency and heat rejection. Like the Batten engine, Feuling's BE is an all-aluminum design, with an alloy sump able to handle structural loads. The Feuling block was developed by Keith Black Racing Engines, who produced a Y-block with deep skirts. This engine was also linered — in this case by a set of aluminum/[[Nikasil]] liners courtesy of [[Mahle GmbH|Mahle]].<ref name="hrm-apr1987b"/>

The engine's camshaft profiles were the result of a collaboration between Feuling, Engle Manufacturing Company, and Dick Jones Camshafts. In the BE, the camshafts are driven by timing belts rather than chains. Each intake and exhaust valve has its own external port. External manifolding connects each exhaust port to one of two different turbochargers.<ref name="hrm-apr1987b"/>

Feuling later used a similar cylinder head design on what is reported to be a Cosworth block to create a Feuling/Oldsmobile V8 engine intended for Indianapolis.<ref name="mas-fov8"/> This was a different engine than Oldsmobile's own Aurora IMSA/IRL racing V8.

Output of the Feuling BE engine is estimated to have been approximately {{cvt|1000|hp|kW}}. It was used in the long-tail Aerotech car.<ref name="oo-aerotech"/>

Applications:
[[Oldsmobile Aerotech]] long-tail

===Quad&nbsp;8===
In an episode of [[MotorWeek]] from early 1988, a photo is shown of an Oldsmobile V8 engine developed using Quad&nbsp;4 technology. The engine is called the Quad&nbsp;8.<ref name="aw-1988"/> What was shown was apparently a mock-up of the engine, possibly built by Feuling Engineering.<ref name="hotrod-jan2023"/><ref name="cyclenews-apr2002"/> The engine made an appearance at a Specialty Equipment Market Association ([[SEMA (association)|SEMA]]) show in Las Vegas, but did not go into production.<ref name="hagerty-apr2020"/> The Quad&nbsp;8 was featured in an article in the June 1993 issue of [[American Rodder (magazine)|American Rodder]] magazine.<ref name="ar-jun1993"/>