Here's a scenario to ponder: You hand picked the best components for an engine build, had those bits meticulously machined and assembled, and ended up with a stout engine that made 850 horsepower on the dyno. The engine runs perfectly on a cool spring day when temperatures and humidity are close to the ideal dyno corrected figures (60 degrees F, 29.92 inches of barometric pressure, zero-percent humidity).
Then the dog days of August roll in. The thermometer now reads 96 degrees and track surface temperatures are well into the triple digits. The barometer reads 29.20 inches of mercury and the relative humidity is a mere 74 percent. Now that stout motor feels like it lost 90 horsepower.
Can you recover some of that lost power? Yes you can, and without having to spend a lot of time and money. We'll show you four tricks of the trade to compensate for weather conditions. But first, some schooling on what weather does to your engine.
Temperature, Humidity, and Dew Point
When an engine is tested on a dyno, the results are corrected to 'dry' air, which means air with no water vapor. While useful for tuning, dyno results don't reflect real-world conditions where temperature and humidity are always changing.
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- Find historical weather by searching for a city, zip code, or airport code. Include a date for which you would like to see weather history. You can select a range of dates in the results on the.
- (Measurement of temperature) 'Degrees Kelvin' (°K) is a former name for the SI unit of temperature on the thermodynamic (absolute) temperature scale.Since 1967 it has been known simply as the kelvin, with symbol K (without a degree symbol). Degree absolute (°A) is obsolete terminology, often referring specifically to the kelvin but sometimes the degree Rankine as well.
Water vapor in the air is better known as humidity. The true amount of water vapor in the air varies with temperature, even if the relative humidity percentages stay constant.
Dew point is a better way to accurately measure water vapor in the air. It is the temperature at which air can no longer hold all of the water vapor, forcing some of it to condense into liquid water. The dewpoint is always lower than or equal to the air temperature.
The difference between air temperature and dew point indicates how close the air is to saturation. If air temperature and dew point match, you will see liquid water in the form of dew, fog, or rain. Good sources for local dew point information are airports close to the track or National Weather Service radio and online reports.
Dew point provides a much better gauge of moisture content in the air than the relative humidity percentage in your local weather report. You can find a detailed explanation on the relationship between dew point and humidity at weathersavvy.com.
Tuning for the Weather
There are three inexpensive tuning tools and one driving tool you can use to compensate for changes in weather conditions:
1. Ignition Timing
As dew point and air temperature get closer together (there is more moisture in the air), you can increase ignition timing. It's kind of like nature's water injection; since there is more water vapor in the air ingested by the engine, the chance of detonation decreases.
An old racing rule of thumb states you can add one degree of timing for every 10 percent increase in humidity, with a maximum of four degrees of extra timing. As we explained above, relative humidity percentages are not an accurate measurement of the amount of water vapor in the air. The best way to determine the right amount of extra timing is to test. Add a set amount of timing, then make a test pass. Keep testing until performance stops improving; that's the sweet spot. Keep an eye on the spark plugs so you can avoid a detonation situation.
Keep in mind that engines with flat top pistons are usually more efficient than engines with big honking dome pistons, so flat top motors can get away with less total timing.
2. Carburetor Jetting
Since there are fewer air molecules in a specific volume of warm air than in the same volume of cool air, hot air is less dense and has less oxygen for an engine to burn. That means you need to change the air/fuel ratio to compensate. In warm air conditions, you have to jet down the carburetor to lean out the air/fuel ratio.
Another old racer rule of thumb states you should go down one jet number for every 20 degrees of temperature increase. Again, the best way to re-jet is to go down one jet number at a time, then test until performance stops improving. Keep a close eye on the spark plugs; they'll show you when the air/fuel mixture is too lean.
There's one more old drag racer rule of thumb to consider: for every 700- to 800-foot change in altitude, the jetting should be adjusted. Just like higher temperatures, an increase in altitude reduces the amount of molecules in a given volume of air. That means you should decrease jet size as the altitude increases. Use the same technique we outlined above to avoid detonation problems.
3. Valve Lash
You can also compensate for higher temperatures and altitude by adjusting valve lash. Increasing valve lash effectively shortens camshaft duration and decreases valve opening overlap. That allows the engine to build more cylinder pressure.
Always start with the intake side first. Try increasing the lash by no more than 0.008-0.010-inch. If the performance of the car improves, do the same thing on the exhaust side. Some cars need an intake lash change only, while others require both intake and exhaust lash changes.
Never go beyond the 0.008-0.010-inch lash figure (perhaps even less with a tight lash camshaft) unless the cam manufacturer advises otherwise. Since what you're doing is artificially increasing the engine's compression ratio, there's a chance for detonation if you go too far. As always, keep an eye on the spark plugs.
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4. Shift Points
Changing your shift points can be beneficial, particularly when barometric pressure changes. When barometric pressure decreases, an engine becomes less efficient. To compensate, you can shift at a higher rpm in each gear. Inertia is working in your favor, particularly when the engine is down on power. Extending shift points allows the engine to operate higher in the torque band, and engine rpm won't drop as low when you shift into the next higher gear.
Keep in mind that changing shift points can be easier said than done. In the case of a car with a two-speed Powerglide (one shift point), this technique is easy-peasy. Increase the shift point by 100 rpm; if the car picks up, add another 100 rpm. The sky isn't the limit here. Roughly 300 to 400 additional rpm is all most camshaft and valve springs will tolerate, but it should be enough to improve performance.
This technique gets more complicated when you add more gears. Take a car with a five-speed manual. The car might like an extended shift point on the 1-2 shift only. Or it might like an extended shift point on the 2-3 and 3-4 shift, but not on the 1-2 or 4-5. The only way to find the perfect setup is by experimenting.
Other Ways To Compensate
There are some other ways to deal with Mother Nature. Keeping your fuel cool is one of them. This applies to the fuel in the car and the fuel you bring to the track. Always store fuel in a tightly sealed proper fuel jug that's kept in a cool spot, like the interior of the trailer.
Rear axle and transmission gear swaps can also prove beneficial. Some cars just like more rear axle gear and/or steeper gearbox ratios when it's hot out. That's why you'll often find drag racers from the East using a little bit more rear axle ratio in their class cars in comparison to similar cars campaigned almost exclusively in the West. It's the high summer humidity east of the Rockies that makes the difference.
Something else to think about is a carburetor spacer. A good wood or phenolic spacer accomplishes two things: It increases intake manifold plenum volume and helps insulate the carburetor from the hot intake manifold. Since a spacer will increase the distance between the manifold plenum floor and the carburetor, the carburetor signal will weaken and larger carburetor jets will be required.
Compared to an open carburetor spacer, a four-hole carburetor spacer tends to reinforce the velocity of the incoming air/fuel mixture. That velocity creates a stronger carburetor signal. If you use a four-hole spacer, you will still have to increase jetting, but not as much as with an open spacer.
Here are some other things that can help engines do better in the heat:
- Lifter valley trays—they work like an air-gap intake by helping isolate the bottom of the intake manifold from hot oil
- Blocked intake heat risers help keep heat away from the carburetor, which keeps the air/fuel mixture cooler
- Wrap carburetor fuel lines with air conditioning hose insulation to keep fuel cool
- Coated headers hold in heat, allowing engines to run cooler
Some cars respond very well to a consistent intake manifold temperature, which is why some racers put bags of ice on the manifold between rounds. Other racers even worry about the color of the car. The bottom line is to do everything you can to get rid of excess heat.
While you can't manipulate Mother Nature, you can counterweigh the effects of weather with some simple tuning changes. Be extremely cautious when making the tuning changes outlined here, and follow up with constant spark plug monitoring. You're walking a fine line between better performance and a pile of parts.
Having Weather Station Problems? This Troubleshooting Guide Should Help.
Complex equipment is not always perfect. And weather station problems can occur with any model, but they do appear to be more common at the less expensive end of the market.
There is no doubt that the less expensive home weather stations, particularly those from La Crosse or Oregon, are a great choice for a first weather station. Many have found them to be everything they wanted, and have successfully put their data online.
But it's sometimes a bit of a lottery. From reviews and posts on forums there are some concerns about quality control, and you can be unlucky with sensors.
Other weather station problems arise with radio interference, equipment malfunction, and improper installation.
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Keep in mind that weather stations are quite complex pieces of equipment, and some compromises need to be made to keep the price within reach of enthusiasts. You do get what you pay for, and it is unreasonable to expect the same standards found in more robust, and much more expensive, commercial and agricultural models. Logic pro x 10 4 4 requirements.
Many potential weather station problems can be overcome by thoughtful setting up, preventive and regular maintenance, and some inexpensive modifications. Here's a more general discussion of Home Weather Station Set Ups.
And also check out The Eight Most Commonly Asked Questions About Home Weather Stations (And The Answers). It's a free 20 page special report, and it comes with a free subscription to Watching Weather newsletter.
The following discussion applies equally to wireless and cable weather stations. Cabled models give faster updates in some cases, but use the same sensors and console. They will often work better if the supplied cables are replaced by stronger versions, or if modified to reduce radio interference. If this is not your strong point, the staff at RadioShack or similar electronics suppliers will be able to help.
Instruction Manuals
Many long standing weather station problems can be traced back to the initial set up. I suspect many of them would have been avoided if the manual had been read before and during assembly, rather than as a matter of last resort.
Now I know you always read the manual before and during any set up, but you may know someone who is less thorough. So you know what to tell them.
But that isn't quite as simple as it sounds, because with some models the instructions are not as clear as they could be, particularly for someone with limited electronic knowledge. Some of the manuals from La Crosse and Oregon manuals could certainly be clearer, although they do seem to be improving. Bear in mind that the radio connection between sensor and receiver may take a while to be established during set up. Be patient, and again, consult the manual.
Waterproofing
Many other weather station problems can be overcome by a little preventive maintenance. Remember that the sensors are not exactly overdesigned, and battery, transmitter or magnet compartments will probably not be weather proof. Regular application of waterproof grease or silicone sealant will prevent water penetration, which is a proven sensor killer.
Another easy way to reduce weather station problems resulting from the entry of water is to ensure that any cables have a drip loop - that they are set up so they loop below both connections and any water drips off the lowest point rather than running down into the equipment.
And equipping yourself with a screw driver which fits the supplied screws perfectly will prevent another common problem - stripping of the screw heads.
In some areas extreme cold or freezing rain can immobilize the wind speed sensor or the rain gauge. Spraying any moving parts with penetrating oil will reduce this problem
Accuracy
Temperature sensors for this family of home weather stations rarely come with any shielding from direct or reflected sunlight and heat. Careful positioning in light shade will help, and still provide enough light for the solar cells to keep an adequate charge. It is also not too difficult to make your own shield - any form of white plastic with slots for ventilation, will improve accuracy when installed around the sensors.
Air pressure needs to be calibrated to sea level to be consistent with official data. Most home weather stations have some means of adjusting the readings, and if your station is linked to your computer you should be able to make adjustments there.
If you live close to an official or commercial weather station, you should be able to adjust your AP to their values.
Birds love rain gauges - often a perfect perch. Unfortunately they are notorious for contributing to the contents. Often attaching some loose pieces of wire will deter the birds without affecting genuine readings. Rain gauges also need regular cleaning to remove dust, leaves and insects.
Radio Reception
Hopefully you were able to experiment with positioning your sensors and receivers to achieve good radio contact before installing them. If you are still having weather station problems that appear to be due to poor signal reception, you may be able to increase the transmission range by taping small pieces of metal to the sensor antennae to increase their effective length. Use electrician's tape for this.
You can also improve the reception at the console end with a slip over connector extension, such as a Sony portable radio antenna - talk to the people at RadioShack about this.
Reception will also deteriorate if batteries are run down - this can happen after long periods of dull weather when the solar cells are unable to recharge the batteries fully. Even a small loss of power can affect performance, so if you start having problems, try fresh batteries. Check your manual for the correct way to install new batteries - it is important to do things in the correct order and to give the sensor and receiver reasonable time to recontact each other.
There is one other problem with cheaper wireless weather stations that has no easy solution, and that is the frequency at which data is updated. This really only affects the wind speed and direction sensors, where update rates of up to 2 minutes may cause the strongest wind gusts to be missed. Some computer software may sample more frequently, but to some extent this problem is related to radio regulations. This is one example where cable connections,if possible, may give better results.
That pretty well covers the most common weather station problems and the ways of minimising or preventing them. Most people find their weather stations do a fine job. Keep the packaging your equipment came in, in case you need to return it, and good luck with customer service. Among the most frequent complaints about both manufacturers, particularly La Crosse, is the slowness in response to questions and warranty issues.
This is unfortunate - overall the products are a good introduction to home weather observation and recording, and it makes no sense for the manufacturers to be slack with customer support.
Good luck, and please let me know if you've found any other ways to improve the performance of your weather station.
For general advice on setting up home weather stations, visit theSetting Up page.Back to the Top, or return to the Home page.
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Last update 05/28/2011
