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Post by doggietom on Nov 15, 2009 17:52:13 GMT -5
ok so this all started after i changed my headgasket and installed ARP studs and a SAFC. Car runs great until you try to boost. I have a maft translator and a SAFC, if you try to boost it's like the motor stutters and does not want to go. I did a boost leak test and found 1 leak fixed it and same problem. any ideas?
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Post by dsmwiseman on Nov 15, 2009 20:43:10 GMT -5
did u check the fuel pressure? and check your plug boots for cracks
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Post by doggietom on Nov 15, 2009 21:51:34 GMT -5
i did add a walbro 255 and a fuel pressure regulator. i forgot about that. i set it at 45psi (no vacuum) i did'nt check my boost for cracks yet, i have a cop setup i have to pick up soon. just gotta pay Aj some cash money.
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Post by dsmwiseman on Nov 15, 2009 21:58:23 GMT -5
why so high on the fuel pressure??
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Post by laser92 on Nov 16, 2009 7:40:58 GMT -5
Should be 37ish if I remember correctly Tom. With vacume removed. May need to be plugged too, It's been awhile. Someone correct me if I'm mistaken please.
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Post by 92redLaser on Nov 16, 2009 7:49:47 GMT -5
hows the turbo feel? my 97 did the same thing when the turbo went bad....
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Post by 99gst_racer on Nov 16, 2009 15:18:59 GMT -5
Should be 37ish if I remember correctly Tom. With vacume removed. May need to be plugged too, It's been awhile. Someone correct me if I'm mistaken please. Yup, with the vacuum line removed, it's: 1G=37 psi 2G=43 psi
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Post by doggietom on Nov 16, 2009 16:11:22 GMT -5
turbo was good last time i checked it, it's a big 16g, i will have to readjust the pressure thx Paul.
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Post by doggietom on Nov 22, 2009 19:38:45 GMT -5
adjusted fuel pressure to 27 as vfaq said to cleaned it up alot i can now get 7 lbs of boost now instide of 0
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Post by laser92 on Nov 22, 2009 22:06:28 GMT -5
I really hope you meant to say 37, becaust 27 is still WAY off Tom
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Post by doggietom on Nov 22, 2009 22:27:54 GMT -5
www.vfaq.com/index-main.htmlSX FPR install The stock Fuel Pressure Regulator (FPR) is designed to increase or decrease fuel pressure 1psi for every 1psi air pressure change. 1G/2G NT FPRs are rated at 47.6psi at zero psi (meaning with the car idling, disconnect the vacuum hose to the FPR, and plug it with a golf tee, bolt, or your finger), the 1G Turbo FPRs are rated at 36.3psi at zero psi, the 2G Turbo FPRs are rated at 43.6psi at zero psi. What this means is that at idle (assuming a healthy engine with stock cams, which should have roughly 18-20" of vacuum), 1G/2G NT fuel pressure should be around 39psi, the 1G turbos should be around 27psi, and 2G turbos should be around 35pi (because 2" vacuum equals roughly 1psi). On a 1G turbo, you should have roughly 41psi at 5psi boost, and 51psi at 15psi boost. When installing a very high flow fuel pump, the stock FPR can easily be overrun, leading to a fuel curve that is no longer linear. On my car, it runs about 40psi of fuel pressure at idle all the way to about 5psi boost. This makes it harder for the ECU to keep the AF ratio "correct", as the nonlinear fuel curve makes the ECU have to dial down the injector pulsewidth (IPW) at idle and low boost, and then raise it back up where it belongs at higher boost. If you have really large injectors installed, the ECU may not be able to dial down the IPW enough at idle to have a smooth idle, as the high pressure combined with the large injectors leads to a rich condition. The problem isn't really the large pump, it's the stock FPR. The return hole on the valveseat in the stock FPR is very small, 1/8" or smaller - it's just not designed to flow a lot of fuel. The fix is to install an aftermarket adjustable FPR (AFPR) that has a much larger passage in it, and will allow you to dial the fuel pressure back down where it belongs at idle. NOTE - make sure you get the right kind of AFPR. The B&M CommandFlo is not what you want. It is basically parts you add to your stock FPR to modify it for higher fuel pressures, it does not let you lower them, as it still has the same stock restrictive outlet hole. You want a Paxton, SX or similar "rcing" AFPR with really large outlets. However, make sure you buy an EFI AFPR, as they do have ones for carbureted cars that have an adjustment range of about 2-15psi - you need an EFI AFPR with an adjustment range of 25-60 or so psi. There are several ways you can plumb this setup, many people cut the end of the stock fuel rail off and weld an aluminum 8AN fitting directly to it. I am going with the complete bolt-on solution, where you cut up a stock regulator, weld part of a steel 8AN fitting to it, and then everything else bolts to it. The advantage of this is that it is very easy to swap between the AFPR and a stock FPR for troubleshooting or if you sell the car. You can get stock FPRs off of Hyundais in boneyards pretty cheaply.
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Post by laser92 on Nov 23, 2009 7:35:42 GMT -5
So it's 27 with the vac line reinstalled?. I'm not sure why you copied and pasted that??? It's better now?
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Post by doggietom on Nov 23, 2009 18:18:00 GMT -5
just to make sure i read it right
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Post by dsmwiseman on Nov 24, 2009 22:43:49 GMT -5
its a typo.. its 37 all day
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Post by doggietom on Nov 27, 2009 21:44:46 GMT -5
i tried it at 37 and it got better with less pressure.
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