PASADENA, CA – The sport compact-car segment has grown increasingly competitive in recent years, from entry-level “tuner specials” (Scion tC) to delinquent “hot hatches” (Mazdaspeed3), all vying for the hearts, minds and pocketbooks of young enthusiasts.

Nissan Motor Co. Ltd., which has been notably absent from the segment as it focuses on strengthening its volume models and polishing its Infiniti luxury brand, enters the fray in 2007 with a 2-pronged attack based on its new Sentra sedan.

Encompassing fourth-generation variants in SE-R and SE-R Spec V guise, the new sport compact Sentras take a page from the auto maker’s history books, eschewing rabid performance for affordability and packaging.

Unfortunately, the tepid enhancements made by Nissan’s performance boffins pale in comparison to those possible through modern aftermarket tuning.

At the core of the new car is a new QR25DE 2.5L high-output 4-cyl. gasoline engine producing 177 hp in the SE-R and 200 hp in the Spec V.

Both engine configurations feature variable intake valve timing, counterweighted crankshafts and dual balance shafts for extra smoothness and efficiency.

However, the Spec V mill adds revised internal components; reworked valvetrain and intake plumbing; a higher compression ratio and redline (7,000 rpm) and a less restrictive exhaust system.

The Spec V engine also requires premium unleaded fuel vs. the regular unleaded requirement of the standard SE-R.

Both units feel stout yet smooth and eagerly rev to the redline, especially in the Spec V.

But in transferring that power to the front wheels, Nissan chooses a complicated and unconventional path.

The more aggressive Spec V dons a traditional 6-speed manual, but the regular SE-R is saddled with Nissan’s Jatco Ltd.-supplied Xtronic continuously variable transmission (with six pre-set ratios operated manually by steering-wheel-mounted paddles).

On twisty mountain roads outside Los Angeles and on the Big Willow road course of Willow Springs International Raceway near here, the Spec V proves to be nimble and athletic, despite its archaic torsion beam solid rear axle.

The ride is smooth (if a little soft) and very composed, with a neutral personality that can provide either understeer or oversteer, depending on the driver’s commands.

Shifting is smooth (but a bit vague); the aluminum-capped pedals are well placed; and the new sport seats are sufficiently supportive; all making for a rewarding driving experience.

However, the standard SE-R, which foregoes most of the Spec V’s dynamic additions in favor of a more “daily driver” demeanor, feels wholly inadequate when pushed hard.

Aside from the soft and wallowing suspension, the biggest detriment is the CVT gearbox (a first in the segment), which Nissan says is designed to offer drivers a more convenient option for long freeway commutes and unenthusiastic spouses.

This configuration is fine for normal Sentras, but the elastic and “winding-up” nature of the CVT saps the responsiveness of the SE-R’s engine and, in normal mode, leaves it cluelessly hunting around for the proper ratio when the driver needs it most.

A disaster? No, but far from ideal for aggressive driving.

In addition, there is no manual gate on the shifter stalk, and the paddle shifters only can be activated by pushing a big “M” button on the console. This inconvenience is exacerbated by the paddles themselves, which rotate with the steering wheel, making it confusing to find the proper lever in the heat of the moment.

Making the SE-R the range-topping regular Sentra and designating the Spec V the standard SE-R would have better served Nissan, while also leaving room for a more track-focused (and more powerful) Spec V.

But the new SE-Rs do represent a solid value proposition.

Nissan followed the $100 per horsepower figure it adopted for the current-generation 350Z sports car and pledges a “200 hp for $20,000” benchmark for the Spec V. Exact pricing will be released prior to the models’ March 8 on-sale date, the auto maker says.

Both models wear 17-in. wheels, with the SE-R adding performance all-season tires, stiffer coil springs and larger brakes – 11.7-ins. (29.7-cm) in the front and 11.5-ins. (29.2-cm) out back – featuring antilock control and electronic brake force distribution.

'07 Nissan Sentra
SE-R SE-R Spec V
Vehicle type Front-engine, front-wheel-drive, 5-passenger, 4-door sedan Front-engine, front-wheel-drive, 5-passenger, 4-door sedan
Engine 2.5L (2,500 cc) DOHC I-4, aluminum block/aluminum heads 2.5L (2,500 cc) DOHC I-4, aluminum block/aluminum heads
Power (SAE net) 177 hp @ 6,000 rpm 200 hp @ 6,600 rpm
Torque 172 lb.-ft. (233 Nm) @ 2,800 rpm 180 lb.-ft. (244 Nm) @ 5,200 rpm
Compression ratio 9.61 10.51
Bore x stroke (mm) 89 x 100 89 x 100
Transmission Continuously variable w/6 pre-set ratios 6-speed manual
Wheelbase 105.7 ins. (268 cm) 105.7 ins. (268 cm)
Overall length 180.1 ins. (457 cm) 180.1 ins. (457 cm)
Overall width 70.5 (179 cm) 70.5 (179 cm)
Overall height 59.1 ins. (150 cm) 59.1 ins. (150 cm)
Curb weight 3,102 lbs. (1,407 kg) 3,078 lbs. (1,396 kg)
EPA fuel economy, city/highway (mpg) NA NA
Market competition Scion tC, Honda Civic Si, Volkswagen GTI Honda Civic Si, Volkswagen GTI, Chevrolet Cobalt SS Supercharged

Stepping up to the Spec V, developed on Germany’s formidable Nurburgring racetrack, brings an optional helical limited slip differential; larger 12.6-in. (32.0-cm) front brakes (with “SE-R”-embossed calipers); performance summer tires; sport-tuned shocks and struts with 0.4-in. (10-mm) shorter springs and a 1.0-in. (25-mm) larger front stabilizer bar; and additional reinforcements in the cowl and trunk.

In addition to the performance add-ons, SE-Rs also feature new front and rear fascias with revised lighting systems; side sill extensions; a rear spoiler; unique SE-R badging and a larger exhaust tip, all of which are conservative in design and do little to improve the Sentra’s bulbous proportions.

Inside, occupants find a black interior with sport seats featuring red stitching and embroidered SE-R seatback logos; attractive red seatbelts (Spec V only); and an array of safety equipment, including six standard airbags and active head restraints.

Also present is a new patent-pending gauge pod atop the infotainment display that houses readouts for oil pressure and lateral G-force measurements.

A 340-watt Rockford Fosgate stereo, sunroof and intelligent keyless access (SE-R only) are the only major options.

Nissan expects the SE-R models, built alongside regular Sentras in Aguascalientes, Mexico, to account for about 10% of U.S. Sentra sales, or approximately 12,000 to 15,000 units, with the mix split 50/50 between the SE-R and Spec V.

Although not poseurs, Nissan’s new SE-Rs lose some performance credibility in their quest to attract a larger customer base, which likely would have been equally satisfied with a single, better executed model.

However, 200 hp for $20,000 in Spec V dress undercuts almost every one of the SE-R’s rivals and positions the homely pocket rockets near the top of the attainable performance ladder.

msutton@wardsauto.com