Join Date: Oct 2011
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I was just poking threw this great thread and wanted to add one little thing about bench setting your AFC. So your truck makes 43 psi according your boost gauge. You take your AFC off and set the compressor to 40 psi and tune your AFC to be full forward (full fuel) at 40 psi (you want full fuel a few psi before you max out boost to ensure just that FULL FUEL). I am now going to tell you why this way ONLY gets you close and not perfect, as mentioned at least 100 times in this thread. Your boost lines going to your boost gauge have like a 3-4mm inside diameter (I'm just throwing that number out there) however, psi=pressure per squar INCH not PER MILIMETER. When a 1
Inch line will lift 40lbs of weight when charged to 40psi, your 4mm boost gauge will lift, well lets see. 25.4mm per 1 inch. So math: 4÷25.4 will give us what percent difference it is between a 1 inch hose and a boost line. So 4÷25.4=0.1574 or 15.74%. So your boost gauge is 84% (100%-15.74%) smaller than what PSI reading are suppose to be measured in (a 1inch hose). This means when a 1 inch line at 40psi can lift 40lbs your boost hose will only lift 15.74% of that or 6.29lbs. I know most shop hoses are probably 1/2 inch but you understand the idea behind how a different diameter hose affects actual PSI. So to adjust for this, companies (like glowshift, autometer, etc..) make this mathematical adjustment by gearing down the boost gauge to accomidate a small tube, to give an accurate (in charging system measurment). So what I'm trying to say, to get your AFC PERFECT take your boost gauge you have been monitoring (from your truck) so that factor remains the same. Make a T, with boost line running from the AFC into a T fitting, then with a piece of boost line coming from the perpendicular portion of the T (this line will run to your mechanical boost gauge you pulled from your truck). Then, run the last port of the T to the air compressor. Final product should have the AFC and air compressor "inline" on the T fitting and the boost gauge coming off the perpendicular hose. Now set your air compressor so your BOOST gauge reads 40psi. Notice: your air compressor gauge will be quite a few lbs off of what your boost gauge reads. Now you can adjust your AFC to perfection. I set my smoke screw while it was on my truck that way when I took it off to adjust AFC I could set the star wheel perfect with my preboost setting.
**the reason just your air compressor doesn't work is because your air compressor line is much larger than a boost line therefore completely throwing off the pressure per squar INCH ratio many of you forgot when tuning with just an air compressor.
Please let me know if I didn't explain something clearly. This is the only way I have been able to set my AFC and I found my "driving and watch smoke and adjust based on visual smoke, tune " was really far off. Whole new truck and driving experience when tuned in this manor.
98 12v SC 4X4 114K Miles, A5K, SDX 5X18, 4K GSK, KDP, Custom VB, Deep Pan, Peak Diesel IC/B, Devils Own W/M, Head Studs, 60lb VS, 2095 Rack Plug, Barrels moved, Guages (EGT, Boost, Trans Temp), Timed 22* http://s1057.photobucket.com/albums/t398/lwilde13/
Last edited by nSaEvAyL; 01-27-2014 at 02:48 AM.