Technician tidbit: Warming up your vehicle: To warm your vehicle or not to warm your vehicle, that is the question! And the answers is… I don’t know about you, but when I wake up in the morning, I can’t spring out of bed and run a marathon without a little walking around first. Give me a few minutes of walking in circles and another two minutes of jump rope and I’m ready to run. In my last article (Oil Changes) I mention how 30 years ago when I was entering the automotive trade, vehicles were still produced with carburetors, leaded fuel was still an option at the gas station where I was working and oil changes were mandatory at 3 months/3,000 miles… I am now going to add that warming your vehicle was mandatory also. But as always, times they are a ‘changing. A cold engine is a dirty engine! This is one of the first things I was taught back in school. Cold engines can’t vaporize the fuel efficiently so you need more fuel to create more vapors. This holds true even today, but manufacturers have engineered today’s vehicles to warm up faster to help reduce pollutants. The old school carbureted vehicles used a movable plate to restrict the air flow through the venturi; this design performed two functions: 1) Air flow restriction which would increase the fuel saturation of the air/fuel mixture ratio. 2) It created a low pressure area (vacuum) just under the plate which would draw excess fuel into the engine through several different fuel ports… more fuel, more vapor. By pumping the accelerator (gas) pedal twice before starting, the high idle step would be set, the accelerator pump would prime the engine with a shot (or two) of gas and the choke plate would close to restrict air and create the vacuum; this was the condition needed for the engine to start. After the engine started, more air was necessary to allow the engine to remain running, so a choke pull off would open the plate slightly. As the engine ran at high idle, the plate would slowly open as the engine warmed up. Three main methods were used to accomplish this; in all methods a heating element was used for the actuation of the choke plate; some vehicles had the heater hose (yes, the hose that brings heat into your vehicle) running across a housing that contains the heating element and as it warmed, it opened the plate. Another type utilized hot exhaust gasses from an exhaust crossover port in the intake manifold and the third type was an electric heating element. As the vehicle warmed the idle would step down (sometimes you had to give the engine a rev) and that is how you knew the car was ready to go. Although effective, this method wasn’t very efficient… at least as fuel conservation goes and so in its place, stepped fuel injection. Carburetors have not been used on mass produced vehicles for about 20 years now; the manufacturers have all switched over to some form of fuel injection to be able to meet the strict pollution regulations that have already been implemented and that get stricter as the years go by. There is no need to pump the pedal twice before starting your vehicle anymore, the air/fuel mixture, idle speed and most operations of today’s engines are all computer controlled. Information being fed to the ECU (Electronic Control Unit) by a multitude of sensors placed throughout your vehicle makes for a more precise handling and conservation of fuel, which in turn creates lower emissions created by your vehicle. So… with that said, let’s get back to the question. Do I warm up or not? My suggested guide on warming your vehicle: (non-carbureted vehicles) - 75 and above degrees = 30 seconds to 1 minute - 50 – 75 degrees = 1 – 2 minutes - 32 – 50 degrees = 2 – 3 minutes - 0 – 32 degrees = 3 – 4 minutes - Below 0 degrees = 5+ minutes After the initial warm up and you start driving the vehicle, the vehicle will warm up quicker, but you need to drive gently at first until you see the temp gauge start to move. This will help you conserve fuel as well as protect your engine. No gauge? Drive easy for about another couple minutes and you should be good to go. ** (This is a suggested warm up guide and should not be used in place of your vehicle manufacturer or your service provider recommendations)
Posted on: Tue, 01 Oct 2013 23:07:55 +0000
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