New 'Hobby' Project, carb tuning gone high tech Options

[McMark]

EDIT: I know about tube-and-water setups. You can't drive with those. I'm building some different.

I've been pondering this project for awhile, and now I'm finally getting ready to start. Every time I synch carbs I think about how terrible and approximate the process is. What I'm going to try is using a small, programmable computer called an Arduino. There are add-ons called Shields to expand the functionality, and I'm using a LCD screen shield. I'm going to hook up 4 to 6 MAP sensors to the Arduino and output their readings on the screen. Using this tool, I'll be able to numerically evaluate the relative balance of the carb throats.

One possible shortcoming is that the intake pulses may create fluctuating values that are difficult to interpret. Although, I have some ideas that may deal with this. Some sort of averaging could help. (IMG:style_emoticons/default/idea.gif)

Here's what the Arduino looks like (this is the Uno version)
(IMG:http://www.914world.com/bbs2/uploads_offsite/www.adafruit.com-419-1381898348.1.jpg)

Here's the screen shield
(IMG:http://www.914world.com/bbs2/uploads_offsite/www.adafruit.com-419-1381898349.2.jpg)

Here's the MAP sensors I'm going to start with.
(IMG:http://www.914world.com/bbs2/uploads_offsite/thumbs4.ebaystatic.com-419-1381898350.3.jpg)

I'm also probably going to have to make some plates that will go between the carb and manifold with a vacuum port on it. This would be the easiest way to access manifold vacuum since I can't count on carbs to have vacuum ports. Oh, and this will also be useable while driving to evaluate dynamic synch.

[Harpo]

Nice and I'm not even in the sand box!

[bfrymire]

This looks like fun. Couple of comments. I think that a flow meter would work much better rather than a MAP sensor. I did a quick search and could not find the ones i have encountered before. So, I looked at MAFs, which were way too expensive.

Hum. Well, all a MAF is, is a wire heated to temperature and as air flows over it, the temperature of the wire fluctuates and hence its resistance. So, if you used the Arduino ADCs to measure a voltage across the wire, you could sense the air flow. So, it is possible to build your own MAF. Just a thought.

As far as averaging, you have to determine the type of signal you are trying to measure. Signals will have a low frequncy content (Usually what you are trying to measure) and a high frequency content (noise in this case.) Well, if you use standard averaging, you will get a flat line response and loose all of the low frequency content, such as air flow fluctuation. However, using box car averaging you will get some noise rejection, and still retain the low frequency content.

Have you thought about how to display to data to make it easy to adjust? This is me is similar to leveling signals, so, I have used a contour plot to display the data and put a "leveling bubble" on it to represent the center of all four corners, and then you adjust to "bubble" to center. Again, just a thought.

BUt, it sure looks like fun!

-- brett

[Mike Bellis]

This looks like fun. Couple of comments. I think that a flow meter would work much better rather than a MAP sensor. I did a quick search and could not find the ones i have encountered before. So, I looked at MAFs, which were way too expensive.

Hum. Well, all a MAF is, is a wire heated to temperature and as air flows over it, the temperature of the wire fluctuates and hence its resistance. So, if you used the Arduino ADCs to measure a voltage across the wire, you could sense the air flow. So, it is possible to build your own MAF. Just a thought.

As far as averaging, you have to determine the type of signal you are trying to measure. Signals will have a low frequncy content (Usually what you are trying to measure) and a high frequency content (noise in this case.) Well, if you use standard averaging, you will get a flat line response and loose all of the low frequency content, such as air flow fluctuation. However, using box car averaging you will get some noise rejection, and still retain the low frequency content.

Have you thought about how to display to data to make it easy to adjust? This is me is similar to leveling signals, so, I have used a contour plot to display the data and put a "leveling bubble" on it to represent the center of all four corners, and then you adjust to "bubble" to center. Again, just a thought.

BUt, it sure looks like fun!

-- brett

(IMG:style_emoticons/default/agree.gif)
with the MAF's. This way you could see flow at high rpm too. A MAP will loose signal off idle unless it is a pressurized system. VW/Bosch (type) MAF's are pretty cheap and are voltage based. GM MAF's are frequency based if you want to go that route.