Addition to Smokem's AFC SIMPLIFIED thread. Now locked.

B

burnin oil

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I decided to mod my spare AFC yesterday as I couldn't tune out the low boost smoke on my new pump. The 215 gov spring seemed like the ticket. Everything went good until I checked for coil bind. The AFC was limited by about a 1/4" of full travel. In the process of playing I found something that may be of interest to people. The stock 215 gov spring can be installed in the AFC housing without heating and stretching as this has nothing to do with coil bind. To make it work I borrowed a trick from Jim Fulmer (in this thread Question about AFC mod - Competition Diesel.Com - Bringing The BEST Together) and spaced the backside of the diaphram back and it gave just enough room for full travel before binding with the starwheel 95% of the way forward. I also found that using the little piece of the AFC foot you cut off to be the perfect size to use as a spacer. Just in case you can't visualize what I am talking about your AFC diaphram should be assembled in this manner on the rod. Spacer made from AFC foot- modded stock washer ground to move all the wayinside the cavity- diaphram, washer also modded, wave washer, locknut. This will leave the nut tightened down all the way minus about 2 threads. I have not dialed it in yet but it definatly cut the 5-10 PSI smoke down and turbo spool is up from the previous AFC which was working extreamly well in its own right. Hope this help someone.
 
The governor spring is not to be lengthened, only if either of the stock AFC springs are used.
 
note that adding effective distance between diaphragm & afc foot to gain maximum travel can result in the 'at rest' position of the afc foot being foward the same spaced amount.

I ran into this issue; if the spring is not long enough one cannot add extra preload to 'push' the foot/barrel farther back toward the seated position.
 
Weston thanks for the clarification. I think the confusion came from post #5 in your original thread.

Spring choice will vary depending on peak boost pressure, and the desired fuel curve. Many of the springs shown will vary in pressure, and can be modified with a little heat to achieve the correct open pressure.

"Both stock AFC springs are much too short to be of much use. The TST light/medium springs are the correct length and ~ 20/25psi accordingly. The light stock spring can be stretched to increase open pressure to ~ 30psi, and the heavy stock spring can be stretched to increase open pressure to ~ 45psi. For higher pressure applications, such as twin turbo setups the governor spring works quite well, however the shorter spring from the lower hp P7100's comes up a bit short in free length, and is quite high as far as open pressure is concerned." [/COLOR]

Hurley, I am pretty sure that when I reassembled everything the foot was fully to the rear as it was stock. After installing on the truck I put the entire housing full forward with barely any tension on the star wheel and the preeboost just touching the diaphram. I still need to dial it in (broke down on the test drive, cam gear walked forward) but initial smoke is down as is the cloud I was getting at 5-10 PSI. I wonder what we did different? Might have to tear it back off and take another look. Either way I am pretty happy with it.
 
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I got tired of messing with springs a while back, and made this adjustable elbow that fits on the back of the AFC. I put the stock spring back in, backed off the starwheel and use the elbow to make adjustments. It's adjustable from 20psi to whatever you need. I've changed it a little since the picture, it now has a locknut and indexing. I've got it set at 65psi right now, but if I what to change it to 40 or 80 or ?, it takes like a minute. And it cost like $5. Also the rate is somewhat adjusable through the orifice size. A smaller orifice responds quicker. I started small and increased it until it suited me. Works just like the one on the turbo.

AFCBoostElbow.jpg
 
^^^ you know that's a pretty nifty idea right there! You can use a soft spring and just regulate air getting to the diaphragm. Well done!
 
The credit goes to the person that first thought of the boost elbow, this is just another application of it. I know that I'm not the first to use it this way. Honestly, with all of the creative thinkers here, I'm surprised that it's not a standard item with 12v owners. It beats the hell out of messing with the springs.
 
Even with a restricting orifice, there is no reason there aren't a few good spring options in the aftermarket.
 
Drothgeb said:
The credit goes to the person that first thought of the boost elbow, this is just another application of it. I know that I'm not the first to use it this way. Honestly, with all of the creative thinkers here, I'm surprised that it's not a standard item with 12v owners. It beats the hell out of messing with the springs.
Click to expand...

I have a boost elbow sitting right in my tool box that might get put to use!
 
Drothgeb said:
I got tired of messing with springs a while back, and made this adjustable elbow that fits on the back of the AFC. I put the stock spring back in, backed off the starwheel and use the elbow to make adjustments. It's adjustable from 20psi to whatever you need. I've changed it a little since the picture, it now has a locknut and indexing. I've got it set at 65psi right now, but if I what to change it to 40 or 80 or ?, it takes like a minute. And it cost like $5. Also the rate is somewhat adjusable through the orifice size. A smaller orifice responds quicker. I started small and increased it until it suited me. Works just like the one on the turbo.

AFCBoostElbow.jpg
Click to expand...
Where'd you get that?
 
im running something similar on mine, it works really good. i can run a light spring in the afc and just block off any airflow until whenever i want, i have it set for around 20psi right now
 
so which spring should i be looking for to run in my 550cc pump with 7x14s and a 66/s480? i have a governor spring in there right now, but it takes alot to budge.

Sent from my YP-G70 using Tapatalk 2
 
burtonboarder said:
so which spring should i be looking for to run in my 550cc pump with 7x14s and a 66/s480? i have a governor spring in there right now, but it takes alot to budge.

Sent from my YP-G70 using Tapatalk 2
Click to expand...


you could always try stretching the stock AFC spring. Its free and takes all of 15 minutes to do.
 
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