I have a mass airflow (MAF) sensor in my '95 Corvette with a small round screen inside. I've seen aftermarket sensors without the screen, which are claimed to increase airflow and horsepower. Couldn't you accomplish the same thing by removing the screen from the original sensor? What, exactly, is the advantage of an aftermarket unit? If I modify or replace the sensor, will I need to buy a programmer for the ECU, to keep the "Check Engine" light from coming on?
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Yes, you can increase airflow by removing the screen. However, be aware that removing the screen changes the flow rate of the meter and causes the engine's fuel mixture to become leaner. Another reason the factory put a screen there was to act as an "air straightener," to increase laminar airflow. Laminar airflow, sometimes known as streamline flow, occurs when a fluid-in this case, air-flows in parallel layers, with no disruption between the layers. Simply stated, it makes the air straight to get rid of turbulence in the intake tract. There are some factory vehicles that did not come with screens, such as the higher-performance Z06. Delphi worked hand in hand with aftermarket MAF-sensor specialist Granatelli Motorsports to devise a sensor that was ideally calibrated for screenless operation. When considering an aftermarket MAF sensor for your car, only use one that is properly calibrated.
In addition to increased airflow, an aftermarket MAF sensor also promotes freer breathing. It's been said that a stock sensor will flow enough air to support 450 hp, but that doesn't take into consideration the effort it takes for the engine to reach that power level. Think of the OEM sensor as being like a restrictor plate. The engine still has enough power to go 190 mph; it just takes three times as long to get there.
Second, the MAF sensor has a direct effect on the ECM's load table. By increasing airflow, you also advance engine timing. This is another reason why you should only use a calibrated MAF sensor, and not a stock ported or descreened unit. Otherwise, you run the chance of "leaning out" your engine (that is, running too little fuel) while simultaneously advancing the timing-a recipe for disaster. A calibrated MAF sensor will not create this problem. Finally, a calibrated MAF sensor does not require the ECM to be retuned.
I recently watched the Mecum auction on The Discovery Channel and greatly enjoyed it. I'd like to attend an auction myself, but I don't understand the buying and selling processes. Could you explain how it works?
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Auctions are great fun to watch, and participating in the bidding is even better. To start the process, you must register as a bidder with the auction house. The easiest route is to preregister by mail or fax, which will require a photo ID. If you prefer, you can always stand in line the day of the auction. You can find the necessary forms on each company's website.
Buyers agree to pay the ending "hammer" price, plus an auction fee. Payment is typically required within one hour of purchase. Auction fees vary. Mecum, for example, has one of the lowest commissions-6 percent for both buyers and sellers-of the major auction houses. Some auction companies have combined fees as high as 20 percent!
When buying at an auction, it's important to remember that the vehicles are sold "as is," and that all bids are final. So before you raise your hand with your bidder number, inspect your prospective buy as thoroughly as possible. Auction companies do not provide any guarantees about the authenticity or originality of the vehicles they sell.
To sell a car, you must first register with the auction house as a seller. The same fees and agreements apply. In most cases, Mecum-auction sellers are paid before the auction is over. Other auction companies may have you wait anywhere from three to six weeks to receive your check in the mail. Know the policies of each auction house before you make any commitment to buy or sell.
If you've never bought or sold a car at auction before, don't hesitate to ask questions. The auction staff should be ready and willing to explain the process and make your auction experience go as smoothly as possible.
Before you get to the auction block, spend some time watching the bidding action. Observe the auction staff and how they interact with the buyers, so you'll be more comfortable with the process when it's your turn.
Question:In your recent article titled "Low-Pressure Situation," one of the photo captions alludes to a potential problem with attaching wheel sensors to aftermarket wheels. The caption states that the sensors can be attached using a band clamp, a procedure that's shown in the photo. I have a '98 convertible with Forgeline wheels that do not accommodate the sensors. I contacted Forgeline as the article suggests, but their system involves drilling holes in the rim to secure the sensors.
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You are correct: The system Forgeline uses requires drilling a hole into the rim shell to accept the wheel-sensor brackets. However, if your Corvette has a TPMS (tire-pressure monitoring system) and you order a Forgeline wheel, the company will drill the rim and install the bracket for you. While the Forgeline brackets were developed to work with Forgeline wheels, they will work with most other aftermarket wheels as well. A set of four brackets runs about $50.00. Follow the link below for more information.
The caption in question was intended to depict an alternative to purchasing the wheel-sensor brackets. While we know of no problems related to the Forgeline system, some Corvette owners simply don't like the idea of drilling holes in their new rims. If you have an aftermarket wheel that will not accept your C5/C6's valve-stem-mounted wheel sensor, the sensor can be mounted on the inside center of the wheel, similar to the C4 configuration. This requires affixing the sensor to the wheel with an epoxy. You'll need to sand the wheel where the sensor will be mounted, to give the epoxy a good bonding surface.
Another option is to use a band clamp, similar to the ones installed in the C4s. This is the way a lot of repair shops were installing the wheel sensors before the brackets became available. This is not a foolproof system, however, as evidenced by cases in which the wheel sensors have come loose. Other companies offer bolt-in or snap-in style TPMS sensors. The drawback to such a system is that there's nothing to hold the sensors in place if they become dislodged. So if you don't like the idea of modifying your aftermarket wheels, a bracket system may be your best bet.
Question:I hope you can help me with my '98 Corvette. The car is displaying random DTCs [diagnostic trouble codes], the headlights dim occasionally, the dash lights flicker, and other unusual problems occur when I hit bumps in the road. I've replaced the headlight switch and the alternator, and checked all the fuses.
Via the Internet
The majority of C5 electrical glitches can be traced to chassis grounding problems. These are usually caused by corrosion in a chassis ground plug (Image 1) due to moisture building up on the contacts.
While there are several ground connectors on your C5, the underhood contact located inside the driver-side fender (Image 2) is the most likely culprit. Completely disassemble the ground plug and clean the contacts with contact cleaner and a small wire brush or Scotch-Brite pad. Once the contacts are clean, spray them with white lithium grease and reassemble the connector. This can typically be done in 30 minutes.
Unfortunately, the corrosion will eventually return. The only permanent solution is to cut off the underhood chassis ground connector and solder all of the wires into a single ground lug.
While you have the hood up, check your battery terminals to verify that they're torqued to 11 ft-lb. You should also make sure that the positive battery post is not loose or leaking, as this can cause an array of electrical issues. Finally, double check the connection at the alternator to confirm that it's tight.
I have an '07 Corvette that's just started to make some popping noises in the roof. I've checked my weatherstripping and even taken the car to the dealer, but nothing has worked. Have you had any other complaints on this, and, if so, what is your advice?
Via the Internet
This is a common complaint, but fortunately there's a simple solution. Chevrolet has issued a technical service bulletin, No. 08-08-67-13A, to correct the problem. The popping noise you're hearing could be caused by the roof-panel latching handles. What happens is the nylon rollers inside these handles can come loose, allowing the rollers to move on the pins. This movement causes the popping sound. The fix for this is to replace the left and right front roof panel handles and lube them at the same time. The new handles are designed without the nylon rollers.
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