changing fuel pressure for smog check

[sy2185]

I've got a mech. herew in san diego that'll ignore my visual violations if the truck passes the sniffer test. I plan to crank down the fuel pressure literally on the side of the shop before I pull in. My question is how low to go? It's not a dyno style rolling test b/c of the awd, and I'll have to drive maybe 50' to the test bay.
35lbs fp?
25?
Any input appreciated.
Jeremy
SY2185

 

[GM TURBO]

Re: changing fuel pressure for smog check

Well, you can only go so low before the truck won't run. The tech that did mine was a bit bothered that my truck didn't like to idle But I did pass.

 

[sy2185]

Re: changing fuel pressure for smog check

how low did you go?
Jeremy

 

[Jimmy]

Re: changing fuel pressure for smog check

Just turn it as low as you can that it still runs.

 

[BigBadSmoosh]

Re: changing fuel pressure for smog check

mine was around 25lbs when i managed to pass emissions.. that and half a tank of super + 3 bottles of gas anti-freeze (alcohol) and she passed like a champ.

i limped the truck home and fixed it.

 

[JSM]

Re: changing fuel pressure for smog check

I just got a local truck here to pass through just the chip.

I adjusted the tables and got truck to run, drive with o2's around 30-50mV at all times.

I also pulled 14 deg. of timing out across the board.

Turned boost off as much as possible

Raised idle to 900

Truck was probably getting 30mpg, but had almost no power even under boost.

No knock either but timing under boost was 0.

It did work though, and truck passed emissions, but failed the tranny test.

 

[sy2185]

Re: changing fuel pressure for smog check

just got back from failing my first try. I ran w/29lbs fp, 160F thermostat,no egr or pcv valve. Truck was good and hot when tested. I passed all but my idle Hc. allowed is 120, I was 177. But on the 2500 rpm Hc test allowable was 180, i tested 11. I'm gonna do cap,rotor,wires and plugs this weekend, but I'm thinking it' prolly just my oil, low miles but old. Plus, when I checked it a day or two ago, I noticedit kinda smelled like gas. Tech says contaminates in oil can double idle h/c. he wants to see my egr back on, the pcv hooked up(doesn't care if it's the stock airboxor my ATR)and to pass the sniffer. he'll let me keep the afpr. what do you all think? Tips?
Jeremy
SY2185

 

[truckins10]

Re: changing fuel pressure for smog check

Nox should not be getting measured, so dont worry about installing the EGR valve, unless he wont test it without it. Also, without the PCV, you will not be burning any vapours in the engine, so changing the oil wont do much(unless you hook PCV back up). I didnt see it mention, do you have a cat installed?? How old is it. You can try disconnecting the timing connector under the passenger compartment for the test, this will retart timing and should do the trick. Good luck

 

[0966Sy]

Re: changing fuel pressure for smog check

i'm a smog tech here in the bay area. i would turn it down to 35psi. it should pass, as it won't really see any spool up, because its a 2 speed idle test, basically idle/2500rpm. if you have an egr make sure it works before you get there. to see if it works, at idle push the diaphram in, and if truck stumbles it works. good luck.

EDIT- if you turn it too low, you will experience lean misfires, will raise HC an CO.
Get your emissions to look like this
HC 40-60
CO 0.20%
CO2 14.2%
O2 under 1%

Ditto on this, keep it above 35psi. BTW my Sy passed on 42psi base FP with 50# Injectors(open loop chip) thus not correcting fueling to get a 14-7-1 AFR. I tried it at 35psi and between and the HC's and CO's where to high because it was to lean causing more NOX from missfiring. I dont see why people turn to cranking down base FP when it's just going to go lean and cause misfiring which will fail. You want your AFR as close to 14-7-1 as possible to pass.

 

[QUICK STORM]

Re: changing fuel pressure for smog check

Nox should not be getting measured, so dont worry about installing the EGR valve, unless he wont test it without it. Also, without the PCV, you will not be burning any vapours in the engine, so changing the oil wont do much(unless you hook PCV back up). I didnt see it mention, do you have a cat installed?? How old is it. You can try disconnecting the timing connector under the passenger compartment for the test, this will retart timing and should do the trick. Good luck

in CA if the vehicle comes with EGR, it has to be on there. and the PCV needs to be hooked up the the airbox after the filter, its a fresh air recirc. system. as i stated before, if you turn it down to low you will get a lean misfire at idle, no vacuum advance applied to fpr. at 2500 you get a slow spool which increases base fuel pressure and timing somewhat, thus a better burn. low fuel pressure isn't always the trick. a lean misfire is the worst miss that you can have. good luck

 

[mrweelr]

Re: changing fuel pressure for smog check

Hey Branden -

I'm in Santa Clara and I'm currently in the process of doing RPM A2A IC, 60-1 turbo w/3" downpipe, 50# injectors, ATR headers, 3" cat, Razor alky and some other stuff. Truck used to pass sniff test no problem when I had Ultimate for stock injectors. I just turned the base fuel pressure back down to ~38 without vac and hooked the EGR up. Tech never gave me crap about the Kenne Bell cold-air kit, but I guess if he wanted to he "could." I'm wondering if the truck will pass CA emissions with all the new speed goodies? I'm actually more concerned with the visual inspection than the sniff test. Will the tech close the hood as soon as he sees headers, different turbo, intake, etc.? Sure hope not...ugh.

 

[sy2185]

Re: changing fuel pressure for smog check

Have a "hook up". My guy said he'd forget visual violations(except egr&pcv) but as a what if I asked him what else it'd fail for and he said AFPR, ATR intake,and aftermarket throttle body, but he missed my 42mm Tial ext. WG on the x-over pipe and mentioned he could be a real dick about the alky b/c it's technically in front of the cat, thereby needing a CARB E.O. #.
Jeremy
SY2185

 

[mrweelr]

Re: changing fuel pressure for smog check

No hookup, it's not going to be pretty (sigh). Oh well, I worry about it when the time comes.