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Post by prestonchipfryer on Jul 23, 2014 17:35:28 GMT
Might be me but has anyone noticed that because of the warmer air we are currently enjoying (enduring) that their car engines don't run quite as sweetly as normal. I say this because engines, especially performance ones, require a lot of air for performance and cold air is, I think, preferable to hot air. Or am I just talking a load of hot air?
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Post by pre65 on Jul 23, 2014 17:39:53 GMT
Yes, you are right.
Cool. or cold air is more dense. 
Vehicles run worse at higher altitudes as well.
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Post by MartinT on Jul 23, 2014 17:59:57 GMT
'tis true, but since the traffic has been particularly awful these past two weeks, there's been no need for more power.
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Post by Deleted on Jul 23, 2014 18:08:45 GMT
Ah i guess old 'Beetle' owners don't have a problem..
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Post by pre65 on Jul 23, 2014 18:14:13 GMT
Ah i guess old 'Beetle' owners don't have a problem..  |
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Post by Deleted on Jul 23, 2014 18:25:34 GMT
Why that? Cool air inlet, fan to outlets
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Post by kember on Jul 23, 2014 23:03:27 GMT
Yup - one of the reasons the old Jag V12s never did well in Australia.
Peter
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Post by pinkie on Jul 24, 2014 6:06:53 GMT
This is true best of hifi forum stuff. Information which is true, at least, not outright wrong, but where it gets extrapolated too far. This is an agreeable mild summer we are briefly enjoying, but by the standards of the planet as a whole it's not that hot. Performance record breaking cars have used deserts for their attempts. Have a think about the temperature many f1events are run in. An engines performance requires oxygen to burn with its fuel. How much oxygen it gets is determined by the density of the oxygen in the air, and the volume of air it can Suck in. Most cars, in most conditions get more oxygen than they need and breath out the spare in their exhaust. At altitude there is less oxygen per cc of air, but still enough to power a jet to keep an aeroplane in the sky. As air heats, it expands, and has a lower oxygen density per cc, which is why turbos use intercooler - you can force more cool air into a combustion chamber than you can warm air. But most cars are probably not oxygen starved when the British climate hovers briefly above freezing.  |
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AlexM
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Post by AlexM on Jul 24, 2014 9:33:11 GMT
Pinkie,
That may be true, but it is a question of calibration not available oxygen. Petrol engines are throttled, so by definition there is excess oxygen at anything less than full throttle. Barometric pressure and temperature define how much fuel can be burnt, and therefore what torque is available at full throttle.
An ECU is set up with base fuel and timing maps, and these are altered by trim values for air mass flow and inlet temperature. The ECU continuously adjusts timing and fueling to hit target air/fuel ratios for a given speed and load. Additionally, the ECU may retard timing when temperature rises, which will directly affect torque output. I used to run an aftermarket programmable ECU in my Impreza, and I could monitor via a laptop the changes the ECU made on the base maps in responses to changes in barometric pressure and inlet temperature. For a highly tuned engine where you raise turbo boost, fuelling and advance timing to the limit of detonation, a rise in external temperature will almost always result in timing being retarded.
The long and short of it is yes, your car will feel a little more flat when temperature rises, and all modern cars with a catalyst do this.
Alex
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Post by MartinT on Jul 24, 2014 9:46:42 GMT
Diesels don't work on the same air/volume ratio as petrol, they take in all the air they can (often forced by a turbo) and burn a metered amount of injected fuel. If too much fuel is injected to burn fully in the available air, unburned fuel emerges as smoke. They too will develop slightly more power in winter due to cold air being more dense, although an intercooler cools the incoming air after the heat of the turbo action.
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Post by walpurgis on Jul 24, 2014 9:53:02 GMT
Ah i guess old 'Beetle' owners don't have a problem.. Yes they do. They own a 'Beetle'. Not a car I'd choose. Not that I've got anything against older cars, especially when they use the BL 'A' Series engine. By the way, I used to run tuned Minis (the real Minis) and always ran them slightly rich to avoid burning exhaust valves, but they definitely went quicker when the weather was hot. Probably the air/fuel balance coming together better. My modified Minivan (one of thirteen minis I had) used a well sorted 1014cc engine would top 105mph (4600 rpm in top on a 3.44 diff), pretty quick for its size and time, it looked good too in Ferrari red with gold alloys. It would also outcorner anything else I ever came across. |
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Post by Deleted on Jul 24, 2014 10:16:40 GMT
Ah i guess old 'Beetle' owners don't have a problem.. Yes they do. They own a 'Beetle'. Not a car I'd choose. Not that I've got anything against older cars, especially when they use the BL 'A' Series engine. By the way, I used to run tuned Minis (the real Minis) and always ran them slightly rich to avoid burning exhaust valves, but they definitely went quicker when the weather was hot. Probably the air/fuel balance coming together better. My modified Minivan (one of thirteen minis I had) used a well sorted 1014cc engine would top 105mph (4600 rpm in top on a 3.44 diff), pretty quick for its size and time, it looked good too in Ferrari red with gold alloys. It would also outcorner anything else I ever came across. How I loved hot minivans. When I were a lad, I used to race slotcars for a bloke that owned a shop. He made regular trips up to Clerkenwell to a factory that produced his gears. The day after I passed my test, he said "rightho then, there is the van, you know where the factory is, see you later!!" Oh boy oh boy did that thing go, stop and corner. I passed my test in my sister's Triumph Herald  In spite of the fact that I came to prefer rear wheel drive, that thing was brilliant. Noisy as hell as it was stripped out and the suspension was basically solid. The only noisier car I have been in was my nephew's hot Beetle. As suggested, the less said about that the better  |
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Post by walpurgis on Jul 24, 2014 11:06:16 GMT
Yes they do. They own a 'Beetle'. Not a car I'd choose. Not that I've got anything against older cars, especially when they use the BL 'A' Series engine. By the way, I used to run tuned Minis (the real Minis) and always ran them slightly rich to avoid burning exhaust valves, but they definitely went quicker when the weather was hot. Probably the air/fuel balance coming together better. My modified Minivan (one of thirteen minis I had) used a well sorted 1014cc engine would top 105mph (4600 rpm in top on a 3.44 diff), pretty quick for its size and time, it looked good too in Ferrari red with gold alloys. It would also outcorner anything else I ever came across. How I loved hot minivans. When I were a lad, I used to race slotcars for a bloke that owned a shop. He made regular trips up to Clerkenwell to a factory that produced his gears. The day after I passed my test, he said "rightho then, there is the van, you know where the factory is, see you later!!" Oh boy oh boy did that thing go, stop and corner. I passed my test in my sister's Triumph Herald In spite of the fact that I came to prefer rear wheel drive, that thing was brilliant. Noisy as hell as it was stripped out and the suspension was basically solid. The only noisier car I have been in was my nephew's hot Beetle. As suggested, the less said about that the better Yes, mine was incredibly noisy, open bell mouths on the carbs, straight through big bore exhaust with only two 'cherry bombs' as silencers and no sound proofing. It sounded like a Lancaster bomber. Great fun. |
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