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Registered
Join Date: Apr 2005
Location: Co. Carlow, Ireland
Posts: 455
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911 goes like stink in cold weather
Winter has been setting in here in England and we've just got our first bout of cold weather. I've just been out for a spin in the 911, and wow - I've never felt it accelerate so hard! I'm sure its got another 50 bhp from somewhere!
I've heard before how in cold weather cars get a little more power due to the cold air being denser or something, but I can't quite understand how this should make a difference. I could understand if there was more fuel being squirted into the cylinders as well, but not the denser air alone. Any ideas? Also, do any of you chaps know what sort of difference it makes to power? Not much I expect in reality, but I can certainly feel it.
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Charles '84 911 3.2 |
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11-24-2005, 03:24 PM
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Registered Cruiser
Join Date: May 2004
Location: Pursuing Happiness
Posts: 3,892
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Cold dense air at sea level is like a Guiness for your 3.2.
Post # 69....
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87' Carmine Red Carrera - Keeper 82' Silver SC - Sold 79' Gran Prix White SC - Sold 05' Black C2S - Daily driver I have never really completely understood anything. |
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11-24-2005, 03:41 PM
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Registered
Join Date: Dec 2003
Location: Arapahoe County, Colorado, USA
Posts: 9,032
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Charles,
I’m somewhat surprised you notice such a large change. You always will see some change just due to the fact that our 911s are head temperature limited and the denser cold air. Do you have any issue with running warm otherwise? Could the Vicar’s church mice have found a home and be an issue in normal weather (never hot in Liverpool) and not be a problem in cold weather? Take a torch (flashlight) and peer back past the fan and see if there are any signs of rodent nests. Occasionally you will see leaves and nesting material coming out from under the fan shroud along the cam boxes or at the intake runners. Short of removing the fan housing, the two easier (not easy) places to look are by removing the cover over the engine oil cooler and the tin behind the distributor. Enjoy the power! Best, Grady
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11-24-2005, 04:17 PM
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Registered
Join Date: Apr 2001
Location: Linn County, Oregon
Posts: 48,575
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Grady, probably not as noticeable in your mile high altitude, but yes...cold air delivers more oxygen, and it's very noticeable at sea level or slightly above. Drag racers have known this for years, routing ducting for the air feeding the intake to the front of the car in order to feed in outside air, cooler than the under hood air...
it does make a difference. Your tips on looking for a rodent nest are well appreciated! I try to remember to pull up my heat lever when parked and plug the exhaust pipe with a tennis ball, thus eliminating 2 of the paths the little monsters enter though...also, whenever our cats want to play in the garage? They are more than welcome to do so! Especially when the car is covered to reduce scratches. 
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"Now, to put a water-cooled engine in the rear and to have a radiator in the front, that's not very intelligent." -Ferry Porsche (PANO, Oct. '73) (I, Paul D. have loved this quote since 1973. It will remain as long as I post here.) |
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11-24-2005, 04:35 PM
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Registered
Join Date: Apr 2005
Location: Co. Carlow, Ireland
Posts: 455
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Thanks for the suggestions Grady. I was exagerating rather a lot when I was saying it felt like 50bhp, but yeah, it does feel a very noticeable. I haven't had any issues running warm and I don't think any little furry animals have made their home in my engine, but what do you mean by our 911s being head temperature limited? Is this to do with the cylinder head temp sensor? I'm not sure what the CHT sensor does, apart from sense the temporature of course!
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Charles '84 911 3.2 |
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11-24-2005, 04:37 PM
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Back in the saddle again
Join Date: Oct 2001
Location: Central TX west of Houston
Posts: 56,274
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Don't forget that the gas is also cold and more dense.
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Steve '08 Boxster RS60 Spyder #0099/1960 - never named a car before, but this is Charlotte. '88 targa  SOLD 2004 - gone but not forgotten
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11-24-2005, 04:44 PM
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Me like track days
Join Date: Sep 2003
Location: Kirkland, WA
Posts: 10,209
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My 930 sure loved the 80 degree intake temp vs. 130 at the track day a few days ago. Zippier for certain.
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- Craig 3.4L, SC heads, 964 cams, B&B headers, K27 HF ZC turbo, Ruf IC. WUR & RPM switch, IA fuel head, Zork, G50/50 5 speed. 438 RWHP / 413 RWTQ - "930 is the wild slut you sleep with who tries to kill you every time you "get it on" - Quote by Gabe Movie: 930 on the dyno |
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11-24-2005, 07:37 PM
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Non Compos Mentis
Join Date: May 2001
Location: Off the grid- Almost
Posts: 10,603
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Any small airplane has a noticably better climb rate on cold days. The performance charts all take temperature into account to determine take-off length and climb.
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11-24-2005, 07:41 PM
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Me like track days
Join Date: Sep 2003
Location: Kirkland, WA
Posts: 10,209
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High & hot & heavy = not good
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- Craig 3.4L, SC heads, 964 cams, B&B headers, K27 HF ZC turbo, Ruf IC. WUR & RPM switch, IA fuel head, Zork, G50/50 5 speed. 438 RWHP / 413 RWTQ - "930 is the wild slut you sleep with who tries to kill you every time you "get it on" - Quote by Gabe Movie: 930 on the dyno |
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11-25-2005, 12:44 PM
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