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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / November 2006Can a laser thermometer pinpoint skipping cylinder?
http://cgi.ebay.com/New-ST632-Infrared-Non-contact-Thermometer-Laser-Site_W0QQit emZ290049260392QQihZ019QQcategoryZ50974QQrdZ1QQcmdZViewItem?hash=item29004926039 2 Could such a thermometer be used to tell 'which' cylinder is misfiring when an engine is determined, by ear, to be skipping? (I am NOT affiliated with this sale!) Does anyone use such? What parameter(s) would a mechanic need on such a device to determine which cylinder(s) is colder due to not firing? I'm visualizing several automotive uses for a thermometer like this. Thanks for experienced feedback, including what brand has been used successfully. s >http://cgi.ebay.com/New-ST632-Infrared-Non-contact-Thermometer-Laser-Site_W0QQit emZ290049260392QQihZ019QQcategoryZ50974QQrdZ1QQcmdZViewItem?hash=item29004926039 2 > [quoted text clipped - 5 lines] >this. Thanks for experienced feedback, including what brand has been used >successfully. s I didn't visit the site but just thinking about it, if you can aim a non-contact IR thermometer at the exhaust manifold's individual outlets from each cylinder I would think the one missing would give a cooler reading then the others. Don't spend a lot on such a thermometer, a $40 should work fine. It just will be off a few degrees on some materials but you would only be looking for the relative temps anyway's. >>http://cgi.ebay.com/New-ST632-Infrared-Non-contact-Thermometer-Laser-Site_W0QQit emZ290049260392QQihZ019QQcategoryZ50974QQrdZ1QQcmdZViewItem?hash=item29004926039 2 >> [quoted text clipped - 5 lines] >>this. Thanks for experienced feedback, including what brand has been used >>successfully. s >I didn't visit the site but just thinking about it, if you can aim a >non-contact IR thermometer at the exhaust manifold's individual [quoted text clipped - 3 lines] >degrees on some materials but you would only be looking for the >relative temps anyway's. What is the point? The engine computer on any car made in the last fifteen years will be able to report a missing cylinder by the crank angle etc.. >>>http://cgi.ebay.com/New-ST632-Infrared-Non-contact-Thermometer-Laser-Site_W0QQit emZ290049260392QQihZ019QQcategoryZ50974QQrdZ1QQcmdZViewItem?hash=item29004926039 2 >>> [quoted text clipped - 21 lines] > fifteen years > will be able to report a missing cylinder by the crank angle etc.. My initial thoughts were for 'portable' use, say at an auction sale, where you may have 5 minutes to decide if you buy or pass. A friend uses a paint thickness electronic reader to determine whether a car has re-paint on any of its panels, He deals only in high dollar vehicles. Needless to say it works well. IF the i-r thermometer could somehow help determine whether a car has a burned valve or merely a skip due to electronics or fuel mix or vacuum, it may have an application. s > http://cgi.ebay.com/New-ST632-Infrared-Non-contact-Thermometer-Laser-Site_W0QQit emZ290049260392QQihZ019QQcategoryZ50974QQrdZ1QQcmdZViewItem?hash=item29004926039 2 > [quoted text clipped - 5 lines] > this. Thanks for experienced feedback, including what brand has been used > successfully. s Depends on whats happening a lean cylinder will run hotter an overly rich cylinder will run cooler lack of spark will run cooler. and will only be noticable if its doing it for a while. if its a cast manifold like 99% of production cars you wont be able to tell the difference as it will heatsoak the entire manifold rather quickly. > http://cgi.ebay.com/New-ST632-Infrared-Non-contact-Thermometer-Laser-Site_W0QQit emZ290049260392QQihZ019QQcategoryZ50974QQrdZ1QQcmdZViewItem?hash=item29004926039 2 > > Could such a thermometer be used to tell 'which' cylinder is misfiring > when an engine is determined, by ear, to be skipping? Yes it can. Its VERY often used on big radial aircraft piston engines where there are 9, 18, or even 28 cylinders to be checked, and you can't get in there to ground a sparkplug wire without getting your face caught in a 14-foot propellor :-p But on a car engine, grounding plug wires until you find the one that doesn't cause a drop in RPM is usually the cheapest/easiest method, and doesn't require removing any exhaust manifold shrouding to aim the thermometer at the exhaust ports. > But on a car engine, grounding plug wires until you find the one that > doesn't cause a drop in RPM is usually the cheapest/easiest method, and > doesn't require removing any exhaust manifold shrouding to aim the > thermometer at the exhaust ports. Is grounding the same as pulling the plug wire? Coz that's how I used to do it. Speaking OT of paint thicknesses to determine bodywork though, wouldn't a well-done repair on a slightly bent up panel (think minor fender bender) show thicker paint, but a completely new replacement panel (think major accident or a cow-cut car) show up as 'normal'? Just wondering. Of course, a bad body repair is often visible from 20 feet away, but I assume that the car dealer guy knows what to look for in that case. -phaeton > Is grounding the same as pulling the plug wire? Coz that's how I used > to do it. Those are two different things. Pulling the plug wire is what most people do to find a miss; in this case you are opening the secondary circuit for that cylinder. OTOH if you were to touch the wire conductor to ground you would be grounding it. The benefit to grounding is less stress on the ignition coil from the high voltage, longer duration collapse that occurs with an open circuit. The disadvantage is that you would have to stop the engine and ground one wire at a time, or you would have to hook up a parallel wire in the plug boot to do the same thing with engine running. Toyota MDT in MO >>But on a car engine, grounding plug wires until you find the one that >>doesn't cause a drop in RPM is usually the cheapest/easiest method, and [quoted text clipped - 3 lines] > Is grounding the same as pulling the plug wire? Coz that's how I used > to do it. Nope. Pulling a plug wire can damage modern electronic engine control systems, grounding the plug by inserting an extension on the plug tips so that each one can be shorted to the engine block with a long screwdriver is safer because it doesn't cause a huge voltage spike at the coil pack. > >>But on a car engine, grounding plug wires until you find the one that > >>doesn't cause a drop in RPM is usually the cheapest/easiest method, and [quoted text clipped - 9 lines] > screwdriver is safer because it doesn't cause a huge voltage spike at > the coil pack. I see. Thanks for the correction, Steve and Comboverfish. Though, I mistyped my question (should have been "is pulling a plug wire as effective as grounding") but all is well. I was wrong anyways and learned something in the process. :-) -phaeton > > But on a car engine, grounding plug wires until you find the one that > > doesn't cause a drop in RPM is usually the cheapest/easiest method, and [quoted text clipped - 8 lines] > bender) show thicker paint, but a completely new replacement panel > (think major accident or a cow-cut car) show up as 'normal'? Yes. But the point of devices like that is that of a negotiating tool. If this guy's friend is an expert he doesen't need a $40 gizmo to tell if the car has been repainted. However, if he sees a repaint and tells the seller "it's been repainted" to an expert paint job, the seller can say "no, your just trying to buffalo me, prove it" and the buyer is kind of stuck. However, if the buyer whips out a $40 gizmo with blinking lights, points it at the car, and says "my $40 gizmo says it's a repaint job" the seller might possibly be so impressed that he concedes the point right away, rather than stonewalling. After all, an electronic gizmo with blinking lights is so obviously superior that it must be right. I'm sure the guy's friend could probably use the same $40 gizmo to convince a seller who has a car that's never been repainted, that it has been repainted. And of course, we all assume that the factory paint job is always superior to a repaint, so if the car has been repainted, why then it must obviously be worth less. Remember, all car buyers lie, cheat and steal to try to convince the seller that the car is an utter piece of sh.t and is worthless. All car sellers lie, cheat and steal to try to convince the buyer that the car is in absolutely fantastic shape and is as good as when it rolled off the assembly line. If your playing the game in one of those roles and a $40 gizmo with blinking lights helps you to gain a few points in the negotiaiton, why then it's worth it's weight in gold. Ted |
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