996FLT6

What's the difference in weight of an aircooled 964/993 motor vs a watercooled gt3 motor. How much added weight with the coolant system? Just curious and can someone tell me how the motor gets cooled for aircool motors- I'm clueless. Mike

GrantG

I don't know the precise difference in weight, but the aircooled motors are also significantly oil-cooled motors (oil radiators used extensively).

The engine cooling fan is driven off the crank and blows air through a shroud covering the top of the motor and blows over the finned individual cylinders.

Early 911's (from 1968-1977) used Magnesium crankcases and were much lighter than a GT3 motor.

Much of the benefit of the aircooled motors is that there is less to break: No water pump, no coolant lines, no coolant thermostat, no coolant radiators, no coolant reservoir and pressure cap, etc. Those things all weigh something, but they also are known to be some of the more failure prone parts of a motor (i.e. we've seen issues with coolant fitting and lines on GT3's, but it's much more rare to see a GT3 or another 911 dump its oil).

996FLT6

Now the reason for the change is noise regulations? Let's just say hypothetically gt3's remained aircooled. How would it fare from a racing perspective? Water is probably a better medium for cooling less hotspotting but what if they kept air-cooled system? Mike

GrantG

It seems that Porsche had trouble with making a 4-valve per cylinder head without water-cooling (as well as noise, emissions, and fuel economy issues). So, I think it would be hard to reliably get 125hp/L from a normally aspirated aircooled motor (like in the RS 4.0).

Some race aircooled motors do see some numbers that are close to that though.

jrgordonsenior

I know the GT3 motor weighs about 50-60 lbs more than a M96 motor though I don't know why....