Car Craft July 2005 You’ll Need Some Electronics to Do It, but Now It’s Easier Than Ever to Be A Carb-Tuning Hero By Jeff Smith In a time not long past there was that guy down the street from you – that special car-crafting guru who could tune an engine by ear. He was revered by the local gearheads for his uncanny knack for creating not just impressive power, but also transforming chugging street slugs into razor-sharp sweetheart engines. He was like the Pinball Wizard – the deaf, dumb, and blind kid who could play those flipper fingers like he was part of the machine. We were all in awe of the Carb Wizard. While that guy still exists, we’ve discovered a little piece of electronic technology that can turn almost any knowledgeable car crafter in a Carb Wizard. This latest development in hand held electronic-power knowledge is the affordable air/fuel-ratio meter.

Race Engine Jetting - Tuning a. Car crafter in a Carb Wizard. This latest development in hand. Software allows you to custom.

While there are many on the market, we first ftold you about a favorite, the Innovate Motorsports digital unit, in “Tune In, Turn On, and Make Power” (Feb. ’04) where we explain how it works alongside a few basics concerning air/fuel ratio and horsepower. This is such a potentially great tool that we thought we’d get into how to tune your engine using this tool not just for max power, but also to raise the bar for better part-throttle response and highway cruising. While the innovate meter is capable of logging up to 44 minutes of brain-numnbing data, we’ll approach this tuning session assuming you’re going to read the Innovate meter in real time. Ideally, data logging is better because you can study the information more closely. WOT The best place for wide-open throttle (WOT) air/fuel testing is at the dragstrip. Short of that, you can do Second-gear bursts of 2 to 3 seconds each and have a passenger watch the meter.

For your initial work, you should shoot for WOT air/fuel ratios between 2.5:1 to 13.0:1. Remember to make only one change at a time and keep using the same test procedure. If you’re at the dragstrip, use mph numbers to help with tuning trends. As long as your changes improve trap speed, continue to move in that direction.

IN many cases, the combination will be rich – like 11.8:1 at WOT. That means you should start by leaning out the secondary side of the carburetor. With Holleys and Demons, minimum jet changes of two sizes per step are a good idea.

For example, if you want to run leaner, go from 80 rear jets to 78s. It’s also a good idea to start your tuning with the carb in its stock jetting configuration. IF you are five or six jet sizes (or more) away from the box-stock configuration, it’s possible there’s something else wrong with the carb or your engine. PART-THROTTLE TUNING Contrary to what you may think, street engines spend a majority of time at idel and at very low throttle openings.

In addition, the idle cicuit continues to deliver fuel even when the carb is delivering fuel through the main metering circuit. Given this, the best place to start improving highway and in-town fuel mileage is with the idle circuit.

Most general-purpose aftermarket performance carburetors are designed to deliver around a 12.5:1 air/fuel ratio to avoid lean surge conditions. Most mild street engines can tolerate part-throttle air/fuel ratios of 13.5:1 all the way up to as high as 15.0:1.

Keep in mind that all production EFI engines operate 14.7:1 air/fuel ratio and the driveability is excellent. It’s more of a challenge to tune a carburetor to achieve a lean 14.7:1 air/fuel at part-throttle and still deliver excellent and immediate WOT power, but it can be done. What this means is the power-valve and accelerator-pump circuits become much more critical.

This is where a Q-jet shines, using its small, highly responsive primary side to achieve excellent throttle response for part-throttle driving. But other carbs can be tuned to also work very well. Don’t be afraid of 14.0:1 or even 14.5 – 15.0:1 air/fuel ratios, they don’t hurt the engine. Free Download Buckethead Discography Rapidshare Programs For Kids there. There is very little load at highway cruise speeds because the engine is only making about 15 to 25 hp under these conditions. This is definitely cut-and-try type work. IF you go too lean on the idle-feed restrictors, the engine will surge at cruise and hesitate under light acceleration, since most engines don’t like to accelerate at lean air/fuel ratios. If you tune the idle-feed restrictors too lean, the engine will most likely suffer from an off-idle lean stumble as an early indicator that you’ve gone too far.

It’s the transition circuits that are more seriously challenged and the ones that will falter first when you begin to lean out the idle and primary main circuits. TUNING CHALLENGE 1 Our first real-world example started out with a 9.0:1 compression 455ci Olds with a mild hydraulic cam, dual-plane Edelbrock, the stock 455 Q-jet, headers, and an HEI ignition. Fuzzy Logic Intelligence Control And Information Pdf Aarp there. The Innovate meter reported an idle mixture of around 12.0:1 that went lean at about 13.8:1 as the throttle opened up in mild acceleration.