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Discussion Starter #1
OK I have no experience tuning any vehicle. I did stage 1 a few months ago and used the power vision auto tune for quote a few runs. I can't really comment on butt dyno but it runs smooth from idle to the Rev limiter and no longer surges as low speeds.

My question hinges on the tuning. I don't fully understand the effect and value of the ve table. The auto tune does not alter the afr map, only the ve tables. Is this how dyno tuners do it? Does the ecm use these values to adjust it's fuel tables? Is this an altitude sensitive tuning or do these values change with manifold air pressure (which would change with altitude, all else equal)? I remember some mention in the auto tune manual that says it sets air to a different value when in auto tune; is this the target afr of is it just eliminating a variable?

Feel free to link some good articles if you've got them. The reason I assumed the MAP linkage is because the pv manual mentions it. Thanks guys! Young guy wants to know what you old guys have to offer.
 

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Changing the AFR is a big part of what the tuner does . There are a lot of different tuners on the market and there are different ways to achieve the same thing . A dyno-jet power commander, power vision, etc will allow the ECM to compensate for altitude changes . If your AFR is 13 to 1 it will remain that at high altitude , that's part of the reason for electronic fuel injection with sensors in the exhaust , it's constantly adjusting itself to maintain the correct AFR .
 

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AFR tables are used to adjust the mix of air and fuel within the cylinder. VE tables are volumetric efficiency. Basically it tells the ecm how "full" the cylinder guts on the stroke at a particular RPM. So a VE of 85 means that the cylinder only reaches 85% of fill capacity on the fill cycle at that engine speedm
 

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Discussion Starter #4
So why does the power vision only adjust ve and not alter the fuel tables? Is it just providing the ve data to the ecm and letting it do the calculations?
 

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Its a calculation. Its based on cfm (cubic feet per minute), cid (cubic inch displacement) and Rpm. (Revolutions per minute) By using these three inputs, (as well as map sensor on some applications and injector "dead time" to determine when the injector I'd not spraying) this is simply another method of adding fuel, knowing that the AFR is going to be xyz, with ABC amount of fuel based on the calculations, injector size and fu demand from the map sensor. It does not use the O2,sensor readings.

Since it's fuel injection, the pulse width of the injector is adjusted accordingly.

Other efi units use input signals from the TBW, TPS, map sensor and cranks sensor. Each item has a number scale value. Take each number from each one, plot the on an scale, draw a connecting line and the center point they all connect is how much fuel is delivered at that point. Hence the term "map".

Older efi (magnetti marelli) used a map sensor. Personally I like these because they can adjust more accurately and usually faster. When Delphi ignition started in 2002, it was eliminated, as was a cam sensor.

VE is simply another method for piggyback system to provide fuel to increase the AFR. Some feel its more efficient than a standard map override. I agree. They're popular more in the turbo world.

Learning tuners (real closed loop systems) with O2 sensors and wideband, not narrow, are the most accurate IMHO as long as the processor is fast enough.
 

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Discussion Starter #6
Ah thanks! I may spring for the pro auto tune kit when I get cams next year, but I may just have the bike dyno tuned. There's currently no stage 2 maps for a Switchback on dynojet's site which is why I'm leaning towards dynoed at a reputable shop.
 

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Reading this thread reminds me of when I first started back in the mid 60,s my first tuning project was on a 37 UL Harley. Jumped in feet first trying to revive that bike that had not run in years. Also found and met some of the most talented engine men around at that time. Course now stuck in Old School carbed engines no matter the basics are the basics no matter how the means to the end comes.
Have fun azglocker getting to the nuts and bolts of tuning, one day you will be glad you did the legwork.
 
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