I always wondered why this was the case. My father's 78 Ford LTD and uncles 84 Cutlass would be major pains to start in winter. FI cars start right up no matter what the temp - why is that?
Why Carbureted Cars Are Hard to Start When Cold
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Originally Posted By: bretfraz
I think it has to do with the atomization of the mixture. FI units are more precise and can adjust better to the low temps.
/not a mechanic
That is pretty much it.
I think it has to do with the atomization of the mixture. FI units are more precise and can adjust better to the low temps.
/not a mechanic
That is pretty much it.
The ability to vary the amount of fuel dispensed independently of the amount of air with any accuracy.
Sure, a carburated car can choke itself to do this, but that's not really a very accurate way add a richer mixture since when this is happening, the fuel isn't being atomized very well since the jet is being fed x times more fuel than it's optimally designed for. An injector fires the same amount of fuel (rail pressure stays the same) just for longer.
Don't discount modern electronics either. A constant velocity carb really is an impressive thing to see, but has limitations in that it's completely dumb and only has three inputs... throttle, choke and manifold vacuum. It doesn't have the advantage of a computer telling it the intake air temp/oil temp/coolant temp and the amount of air flowing through it (via map/maf).
Plus, carbs are generally not in optimal tune.
Sure, a carburated car can choke itself to do this, but that's not really a very accurate way add a richer mixture since when this is happening, the fuel isn't being atomized very well since the jet is being fed x times more fuel than it's optimally designed for. An injector fires the same amount of fuel (rail pressure stays the same) just for longer.
Don't discount modern electronics either. A constant velocity carb really is an impressive thing to see, but has limitations in that it's completely dumb and only has three inputs... throttle, choke and manifold vacuum. It doesn't have the advantage of a computer telling it the intake air temp/oil temp/coolant temp and the amount of air flowing through it (via map/maf).
Plus, carbs are generally not in optimal tune.
Originally Posted By: bretfraz
I think it has to do with the atomization of the mixture. FI units are more precise and can adjust better to the low temps.
/not a mechanic
You are right. Carbs. have chokes for cold starts that are notoriously unreliable and not very precise.
http://www.2carpros.com/how_does_it_work/choke.htm
Edit: Oops bepperb beat me to it!
I think it has to do with the atomization of the mixture. FI units are more precise and can adjust better to the low temps.
/not a mechanic
You are right. Carbs. have chokes for cold starts that are notoriously unreliable and not very precise.
http://www.2carpros.com/how_does_it_work/choke.htm
Edit: Oops bepperb beat me to it!
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Methenol is far more A/F ratio user friendly than gasoline in cold temps. I think they Idle at 5000 rpm? Not much comparison. The old Detriot iron carbed cars need lots of fuel to get them to pop off.
The cars of the 60s was my time, all had carbs, I put a manual choke and they worked perfectly, and I could drive right out and no coughing or sputtering,,the autochokes could be a pain
Yeah,I put manual chokes on my cars with carbs too. Perhaps the automatic did do a better job when it was working.
Originally Posted By: bepperb
A constant velocity carb really is an impressive thing to see, but has limitations in that it's completely dumb and only has three inputs... throttle, choke and manifold vacuum. It doesn't have the advantage of a computer telling it the intake air temp/oil temp/coolant temp and the amount of air flowing through it (via map/maf).
Plus, carbs are generally not in optimal tune.
On a old Honda CV-equipped car like a Prelude, you have a complex maze of sensors, solenoids, bi-metallic switching valves and a control box that controls the throttle opener dashpots, auxiliary air injection system, and a bi-metallic valve which routes coolant through the carb bodies to help warm things up. And the chokes are controlled via thermistor.
The British SU setups are simple to understand.
A constant velocity carb really is an impressive thing to see, but has limitations in that it's completely dumb and only has three inputs... throttle, choke and manifold vacuum. It doesn't have the advantage of a computer telling it the intake air temp/oil temp/coolant temp and the amount of air flowing through it (via map/maf).
Plus, carbs are generally not in optimal tune.
On a old Honda CV-equipped car like a Prelude, you have a complex maze of sensors, solenoids, bi-metallic switching valves and a control box that controls the throttle opener dashpots, auxiliary air injection system, and a bi-metallic valve which routes coolant through the carb bodies to help warm things up. And the chokes are controlled via thermistor.
The British SU setups are simple to understand.
IF you understand the symptoms of lean/rich starting mixtures, and adjust your automatic choke properly.... or have a manual choke..... the carbureted cars started as fast as a modern fuel injected car. Maintaining that perfect tune probably eluded most mechanics and customers... but if you were your own mechanic you soon got it perfect!!
Actually my carbureted cars started better than any fuel injected car I have ever had, for one simple reason:
You could precharge the intake manifold with gas fumes by pumping the gas pedal the correct number of times - it varied with every car you owned. (The accelerator pump in the carb squirts in a thimble full of gas each time you do this)Then the car would start on the first cylinder up, probably a 1/4 second turn of the key would make it start every time, even well below zero.
Flat spots and over choking still were issues, all through warmup, unless you had a manual choke. Never really figured out why anybody thought the automatic choke was worth it.
Many of my cars had manual chokes - 41 plymouth, 59 ford, 59 Opel, 64 Fiat, 67 BMW. The Fiat used a Weber carburetor with an enrichment valve instead of a choke, this was every bit as good as fuel injection except..... the carburetor cost more than the short block if you were buying!! Ouch!
No, I would not go back!!
Actually my carbureted cars started better than any fuel injected car I have ever had, for one simple reason:
You could precharge the intake manifold with gas fumes by pumping the gas pedal the correct number of times - it varied with every car you owned. (The accelerator pump in the carb squirts in a thimble full of gas each time you do this)Then the car would start on the first cylinder up, probably a 1/4 second turn of the key would make it start every time, even well below zero.
Flat spots and over choking still were issues, all through warmup, unless you had a manual choke. Never really figured out why anybody thought the automatic choke was worth it.
Many of my cars had manual chokes - 41 plymouth, 59 ford, 59 Opel, 64 Fiat, 67 BMW. The Fiat used a Weber carburetor with an enrichment valve instead of a choke, this was every bit as good as fuel injection except..... the carburetor cost more than the short block if you were buying!! Ouch!
No, I would not go back!!
Fuel injectors spray an ultra fine mist that evaporates easily in cold air.
In addition, the ignitions that existed when carbs were used didn't produce as hot a spark as some of the ignitions used when EFI was introduced.
There is another thing not mentioned here. How much easier was starting a mechanical injection engine such as Bosch K-jet/CIS engine when compared to a carb?
There is another thing not mentioned here. How much easier was starting a mechanical injection engine such as Bosch K-jet/CIS engine when compared to a carb?
I believe every Ford, GM and Chrysler manufactured car for US delivery had gone to automatic chokes before the EPA even existed!
What were the last years/cars with manual chokes in Canada?
No doubt a manual choke was a better choice in cold weather - or with better drivers!
What were the last years/cars with manual chokes in Canada?
No doubt a manual choke was a better choice in cold weather - or with better drivers!
Kestas
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I've retrofitted a couple cars to manual choke. I didn't like it. I kept forgetting to push the choke back in and running rich for my entire commute. I quickly went back and properly repaired the automatic choke to work properly.
I've fiddled with carbs for a good part of my wrenching career, and still do. Carburators needed maintenance. When cleaned and adjusted properly, they can perform rather well with respect to cold starting, flat spots, and driveability. I can only imagine how many otherwise good vehicles were scrapped in the past because of neglected carburators.
That said, fuel injection has matured to the point where it is more efficient and reliable than carburators, making FI worth the cost and complexity. It's only in the past 15 years where some manufacturers (i.e., german vehicles) started making fuel injection TOO complicated.
I've fiddled with carbs for a good part of my wrenching career, and still do. Carburators needed maintenance. When cleaned and adjusted properly, they can perform rather well with respect to cold starting, flat spots, and driveability. I can only imagine how many otherwise good vehicles were scrapped in the past because of neglected carburators.
That said, fuel injection has matured to the point where it is more efficient and reliable than carburators, making FI worth the cost and complexity. It's only in the past 15 years where some manufacturers (i.e., german vehicles) started making fuel injection TOO complicated.
As long as cars have to pass smog tests, simple carbs can't be used.
If you want to have simple carbs on a new vehicle, you would need to buy a motorcycle.
If you want to have simple carbs on a new vehicle, you would need to buy a motorcycle.
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