Quad 4 engine

First released to the public as a regular production option for the 1988 Oldsmobile Cutlass Calais and Pontiac Grand Am, the engine's availability expanded to Buick in late 1988 and Chevrolet in 1990, after which it became a mainstay in GM's lineup.

The Quad 4 underwent two rounds of exhaust port size reductions, followed by the addition of balance shafts in 1995 to address its levels of noise, vibration, and harshness (NVH).

At the 1988 Indianapolis 500, the pace car was an Oldsmobile Cutlass Supreme convertible powered by a turbocharged production Quad 4.

After positive reviews for the first few years of sales, the automotive press began to criticize the Quad 4 for its NVH levels when compared to turbocharged four-cylinders, V6es, and occasionally V8s.

The design gained a minor following in hot rodding circles due to its resemblance to a 1930s Offenhauser engine once the ribbed aluminum cover was removed, exposing the tall cam towers and deep valley between them holding the spark plugs.

The naturally aspirated Quad 4 was able to produce that power with a 9.5:1 compression ratio, and was able to meet emission standards without using an EGR system.

Minor running changes to the base Quad 4 included different crankshafts, cams, and manifolds, all meant to increase torque and reduce NVH.

A slightly augmented version of the LD2 was offered in some Oldsmobile Achieva models with the SC (and possibly SL) trim packages.

W41 applications: This SOHC variant of the Quad 4 was intended to replace the Pontiac 2.5 L Tech IV OHV "Iron Duke" engine.

Although power and fuel economy were better than the Tech IV, the Quad OHC was retired after 1994 when the DOHC version became standard.

Applications: The LD9 Twin Cam was a 2.4-liter Quad 4 variant which debuted in 1996 with balance shafts and a redesigned cylinder head.

LD9s also had very small oil passages, making for less than adequate lubrication, and costly engine repairs if not maintained properly.

The engine was a turbocharged 2.3-liter Quad 4 built mainly with factory parts that produced 250 hp (190 kW) at 6400 rpm.

The Aerotech II is a wagon-back sports coupe concept with a 2.3-liter Quad 4 making 230 hp (170 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 4 that developed 230 hp (170 kW).

Under this scheme the derivative engines had to keep the Quad 4's four-stroke combustion cycle, double overhead cams, multi-valve cylinder head and, significantly, 100 mm (3.94 in) bore spacing.

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 4.

The Feuling block was developed by Keith Black Racing Engines, who produced a Y-block with deep skirts.

[13] 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.

[17][18] The engine made an appearance at a Specialty Equipment Market Association (SEMA) show in Las Vegas, but did not go into production.

A 2.3-liter Quad 4 in 1989 Cutlass Calais
A 2.3-liter Quad 4 in 1995 Chevrolet Cavalier Z24
A 2.3-liter Quad 4 W41 engine
Quad OHC engine
A 2.4-liter Twin Cam in 1997 Pontiac Sunfire
Batten RE engine with single turbo
Twin-turbo Feuling BE engine with one external port per valve