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Getrag Rebuilder
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Discussion Starter · #1 ·
I have a 1st gen AVC-R and I took a look at the manual for it on apexi's site and have a question about how to calculate duty cycle. I have been using the boost controller on the A mode which has a default duty cycle of 30%.

I have been having trouble making any significant amount of boost in 1st gear and overall the cars boost response feels a little slugish. My car had been running very rich and now that I got the fuel trims in spec the turbo response is better... but I think getting the right duty cycle will make a world of difference.

I looked through the archives trying to find out how to calculate my duty cycle for a given boost level but am confused. I found a good statement by Mark in a post, he said:
"Duty cycle is supposed to be the percentage your stock wastegate setting is of your final boost desired. That is, if your stock wastegate pressure is 5 psi and you wish to boost to 15 psi your duty cycle should be 66%."

How did Mark get 66%? Wouldn't 5/15 = 33%?

I turned off my AVC-R and found that I'm getting .5 kg/cm^2 or 7.11167 psi from the wastegaskets. I'm planning to run .6 kg/cm^2 or 8.53401 psi to start.

So:
7.11167 / 8.53401 = 0.83

Would my duty cycle be 83%?

What would be the way to calculate duty cycle without converting the kg/cm^2 values into psi?
 

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3,562 Posts
I wish I could help ya right now, but I don't have my car running right now so I can't even check to see what my duty cycle was set at.
 

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Getrag Rebuilder
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1,801 Posts
Discussion Starter · #3 ·
Well, the first gen AVC-R has a lot less tuning options... from what I got from reading the manual you set your boost and calculate the duty cycle to set, then test and see how the boost responds... if it's close to the target boost it will slowly learn the curve. If it falls short or overshoots you need to adjust your duty cycle and try again.

What I'm confused about is how to calculate my required duty cycle based on the wastegasket pressure and what boost I'm going to run.
 

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that is the correct formula, but i found that it did not work for me either. what i did was to set the boost at 1 bar and the duty cycle at 30%. i would then continue to raise the duty cycle until both my apex'i boost guage and the avc-r read 1 bar as well. from then on, i left the duty cycle alone and then raised boost and watched it work. it held boost very well with a little adjusting of the feedback speed and start duty functions.

if i remember correctly, my settings were:

duty: 73%
feedback speed: x 4 3 2 2
start duty: +3 0 -1 -2 -2

hope that helps.
 

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Getrag Rebuilder
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1,801 Posts
Discussion Starter · #5 ·
I went ahead and set my duty cycle for 83% and... wow, big difference in turbo response and feel. I can make full boost in all gears... first gear is alot more fun now. =)
 
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