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SD987 · 10-13-2006, 11:04 PM

Rail26 provides a nice summary, but off the top of my head, I'd say the specific differences between the two engines are:

* 987 crankcase has a fully aluminum bearing saddle for a reduction in weight vs the 986 which has cast iron inserts

* 987 crankcase has a deeper central hole for a .7 lb reduction in weight

* The tensioning rollers and deflection pulleys in the 987 belt drive are made of plastic in engines with a manual gearbox while the 986 are made of steel

* 987 has a new air cleaner with new housing

* 987 resonance intake system has a twin-branch distribution pipe with intake-manifold flap

* The electric fans in the engine compartment of the 987 are infinitely adjustable where the 986 fans are two-stage

* 987 exhaust sytem has lower gas back pressure due to larger cross sections and damping of drive-related vibrations by heat-resistant damping elements among other things

* 987 standard manifold is lighter

* 986 3-way catalytic converter has one converter left and right, where the 987 has one pre- and one main catalytic converter left and right (the lightest catalytic converters in the world)

* 987 silencer is lighter with improved flow rate; and 2 parallel silencers with crossover pipe and integrated main catalytic converter

* 987 water pump has an optimised impeller for increased flow rate and improved component cooling

* 987 water bearing casing is plastic and flow-optimised, where the 986 is die-cast aluminum and 1.9 lbs. heavier

* 987 tandem pump has a vacuum for brake boosting provided by a mechanical vacuum pump where the 986 has a sucking jet pump and vacuum reservoir

* 987 oil extraction pump has lower frictional losses and higher delivery capacity

* 987 doesn't have an oil dipstick (which saves .39 lbs(

* 987 radiator air flow is closed, directing air to the front wheel housings where the 986 is open, directing air in front of the wheel housings

* 987 radiator fan control is continuous, where the 986 is two-stage

* 987 engine compartment scavenging blower is dependent on intake air and ambient air temperature, where the 986 is dependent on intake air only

* 987 secondary air pump is fastened directly to the engine where the pump in the 986 is fastened to the body

* The 987 generator cranks out 420 more w (2100 to 1680)

* The 987 uses motronic 7.8/40 DME which has enhanced computing and memory capacity

* 987 engine weighs about 10lbs less in manual and 12 lbs less in auto but produces 12 more hp, 7 lbft more torque with a 3kW increase in specific output

That's all that comes to mind, but if I thought about it for awhile I might come up with a few more differences.

10-13-2006, 11:04 PM	#4
SD987 Registered User Join Date: Jun 2005 Location: San Diego, California Posts: 874	Rail26 provides a nice summary, but off the top of my head, I'd say the specific differences between the two engines are: * 987 crankcase has a fully aluminum bearing saddle for a reduction in weight vs the 986 which has cast iron inserts * 987 crankcase has a deeper central hole for a .7 lb reduction in weight * The tensioning rollers and deflection pulleys in the 987 belt drive are made of plastic in engines with a manual gearbox while the 986 are made of steel * 987 has a new air cleaner with new housing * 987 resonance intake system has a twin-branch distribution pipe with intake-manifold flap * The electric fans in the engine compartment of the 987 are infinitely adjustable where the 986 fans are two-stage * 987 exhaust sytem has lower gas back pressure due to larger cross sections and damping of drive-related vibrations by heat-resistant damping elements among other things * 987 standard manifold is lighter * 986 3-way catalytic converter has one converter left and right, where the 987 has one pre- and one main catalytic converter left and right (the lightest catalytic converters in the world) * 987 silencer is lighter with improved flow rate; and 2 parallel silencers with crossover pipe and integrated main catalytic converter * 987 water pump has an optimised impeller for increased flow rate and improved component cooling * 987 water bearing casing is plastic and flow-optimised, where the 986 is die-cast aluminum and 1.9 lbs. heavier * 987 tandem pump has a vacuum for brake boosting provided by a mechanical vacuum pump where the 986 has a sucking jet pump and vacuum reservoir * 987 oil extraction pump has lower frictional losses and higher delivery capacity * 987 doesn't have an oil dipstick (which saves .39 lbs( * 987 radiator air flow is closed, directing air to the front wheel housings where the 986 is open, directing air in front of the wheel housings * 987 radiator fan control is continuous, where the 986 is two-stage * 987 engine compartment scavenging blower is dependent on intake air and ambient air temperature, where the 986 is dependent on intake air only * 987 secondary air pump is fastened directly to the engine where the pump in the 986 is fastened to the body * The 987 generator cranks out 420 more w (2100 to 1680) * The 987 uses motronic 7.8/40 DME which has enhanced computing and memory capacity * 987 engine weighs about 10lbs less in manual and 12 lbs less in auto but produces 12 more hp, 7 lbft more torque with a 3kW increase in specific output That's all that comes to mind, but if I thought about it for awhile I might come up with a few more differences. __________________ http://i7.tinypic.com/24ovngk.jpg http://i7.tinypic.com/24ow0id.jpg 06 987S- Sold Carrara White / Black / Black/Stone Grey Two-tone 05 987 5-speed - Sold Midnight Blue Metallic / Metropol Blue / Sand Beige 06 MB SLK350- Lease escapee Iridium Silver Metallic / Black We've heard that a million monkeys at a million keyboards could produce the complete works of Shakespeare; now, thanks to the Internet, we know that is not true. - Robert Wilensky Last edited by SD987; 10-13-2006 at 11:10 PM.