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2,148 Posts
Discussion Starter #1
Hey,

The afm screw mod is a great idea, but unfortunately is a little unsafe becuase you are telling the ecu there is less air, without compensating with more fuel, so it runs leaner than stock.

Originally I was planning to use an AFPR to jack up fuel pressure, then back out the afm screw so I could run 15 psi, with a stock afr. The afpr raises fuel pressure by increasing the preload of a spring on a diaphragm of the fpr, so I did just that with a stock FPR. I did this with a 3/8" drive extension and a hammer, pushing the centre of the top of the FPR down only .23 mm (measured with verniers). I backed the afm screw out all the way (~13 turns) and found a .23 mm fpr crush was needed to get back to stock afr's.

I did all the measurement with my wideband, and then took it for a rip afterward. Unfortunately I cannot load the afr curve from my laptop though(old pos). At 3500 and 5000 rpm its a hair below 12:1, and it dips to about 11:1 at 4000 and toward redline. This is without any electronic tuning.

Not all cars are the same, but if you were to do this, then reset your ecu, the ecu will adjust for any minor car to car variances. THis should be a fairly safe mod to do, as long as your fuel pump is up to par (the stock ct will hate you though).

BTW, I found one thread that discussed the idea.

Good luck!
 

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Destroyer of Turbos
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4,461 Posts
finially someone set out and did it! i had a strong feeling it would work out fine but now we have someone actually back it up. get some graphs up now! what boost are u running?
 

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Madd Tyte JDM yo ®
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7,014 Posts
Good job mate ;) i Knew itd work! now, if you had an SAFC, you could tun out the rest of the richness to 12:1ish and get a little more power out of that thing. id like to see what the fuel pressure changes before and after.
 

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Discussion Starter #4
yah, id like to know the fuel pressure as well, but the end result is afr, and the afr is fine, so I guess it doesnt matter. Last run with the afrs I described was 13 psi boost, falling off up top. I just shimmed the wastegate more, so well se what it is now. I am shooting for something between 13-15 psi for now.
 

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Madd Tyte JDM yo ®
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7,014 Posts
sweet yo... thats great that its not leaning out. do you have a fuel pump installed yet or no?
 

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Madd Tyte JDM yo ®
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7,014 Posts
cool, so when is the Whinebro gonna be ordered ;) maybe you could order an Autometer fuel pressure guage and some adaptors so you could mount that up and see where your FP is at... thatd be pimpin.
 

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Discussion Starter #9
14 psi, with the afm screw all the way out. With more crush and a lexus afm or electronic tuning, it could be higher.
 
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