Page 1 of 3 123 LastLast
Results 1 to 10 of 21

Thread: Best AFR values for emissions?

  1. #1

    Default Best AFR values for emissions?

    Hi all. I'm getting setup to pass my bi-yearly emissions test. For the last 10 years or so, I've had a 4bbl carburetor, and usually just lean out the idle a bit, and put in some smaller jets. Now that I have the Sniper, I can just punch in the numbers and have it hit the AFR that I want. We have an idle test and a 2500 RPM test. I'm assuming 14.7 for both? That seems a bit lean for idle, but certainly doable. Does anyone else pass emissions with their Sniper setup? If so, what AFR settings do you use? Thanks!
    1985 Ford Bronco. 300 (305) ci inline 6. 9.1:1 compression, P&P head with enlarged valves, high flow exhaust. 32" BFG A/T tires. 5 speed ZF5 manual transmission with 3.55 rear end. Holley 550-850 2300 Sniper EFI.

  2. #2

    Default

    Yes, 14.7:1 and reduce timing advance at idle as much as possible. And don't forget the usual tricks in case you're borderline: Warm the engine up thoroughly before the test, try to drive straight off the highway into the test facility (don't sit in the lot with engine off waiting). Change the oil right before the test.

  3. #3

    Default

    Thanks, sounds good. Yeah, it usually passes pretty easily, but again that's with a carb, so I don't always know exactly where the AFR values are. I also spent the weekend installing a smog pump, since it's now required, so that should actually help a bit. Thanks for the reminder on the idle timing. It's at 12° advance, so I'll need to back it down a hair.
    1985 Ford Bronco. 300 (305) ci inline 6. 9.1:1 compression, P&P head with enlarged valves, high flow exhaust. 32" BFG A/T tires. 5 speed ZF5 manual transmission with 3.55 rear end. Holley 550-850 2300 Sniper EFI.

  4. #4

    Default

    I take it you're somewhere in California. You'd think an EFI is cleaner running than a Carb. If anything you can tune it for low emissions no? In any case, you can save a Config File for your annual inspection.

  5. #5

    Default

    This is in Boise, Idaho (one of the only places in the state with emissions). They're not super stringent, but I've failed before when my idle mixture screw was half a turn in the wrong direction, so subtle differences in tuning can make a big difference. I mainly want to get as close as I can on the first run, since you get three attempts for $20. If you fail, you have to pay another $20 to try again. I imagine that it's going to be extremely easy with the EFI setup, but it's the first time I've attempted it, so I want to build my Config File properly. Once it's done, I'll reload my previous one and be on my way.
    1985 Ford Bronco. 300 (305) ci inline 6. 9.1:1 compression, P&P head with enlarged valves, high flow exhaust. 32" BFG A/T tires. 5 speed ZF5 manual transmission with 3.55 rear end. Holley 550-850 2300 Sniper EFI.

  6. #6

    Default

    Depends on what your engine likes. I'd try leaning the idle out until it starts to stumble and then back the AFR down a touch. If you've got timing control you can also retard the ignition timing a bit to get a more complete burn at idle.

  7. #7

    Default

    I don't know how a Sniper could pass the visual part of the inspection. Maybe if your state doesn't open the hood. No way Sniper passes emissions in California. The only TBI kit to have a CARB exemption is MSD Atomic EFI. And that's only on certain years of the Chevy 350.

  8. #8
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    21,582

    Default

    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/X-pipe/shorty headers, 100HP progressive dry direct-port NOS, 160A 3G alternator, Optima Red battery, LenTech Strip Terminator wide-ratio AOD/2700 RPM converter, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  9. #9

    Default

    Quote Originally Posted by 351C Sniper View Post
    I don't know how a Sniper could pass the visual part of the inspection. Maybe if your state doesn't open the hood. No way Sniper passes emissions in California. The only TBI kit to have a CARB exemption is MSD Atomic EFI. And that's only on certain years of the Chevy 350.
    They only check for 3 things. A gas cap, a catalytic converter, and an Air/smog pump. Other than that, if it passes the sniffer test, that's all they care about. They don't check that the engine matches the VIN, part numbers, etc.
    If that were the case, I'd have failed a long time ago when I swapped out my stock 1bbl for a Holley 4bbl.

    Well, I got very close last night, but didn't pass. My first test, I failed MISERABLY.

    Idle
    CO%
    Result Standard Test
    FAIL 1.20 8.65
    HC (PPM)
    FAIL 220 1450

    2500 RPM
    CO%
    Result Standard Test
    FAIL 1.20 8.28
    HC (PPM)
    FAIL 220 517

    However, then it dawned on me that since I had to have an Air pump, I had found a port in the manifold and plumbed it in there. So, once I hooked the belt up, it was dumping oxygen upstream of the O2 sensor. It was throwing the computer way, way off. When I pulled the belt off, Idle AFR was 11:1 and cruise was 10:1. So, it was puke rich. So, I left the belt off, drove around, and let the computer relearn everything. I then turned the learning feature off and put the belt back on. (AFR was now reading about 19 - 20:1 with all of the extra O2 from the air pump).

    Next test:

    Idle
    CO%
    Result Standard Test
    FAIL 1.20 3.64
    HC (PPM)
    FAIL 220 510

    2500 RPM
    CO%
    Result Standard Test
    PASS 1.20 0.22
    HC (PPM)
    PASS 220 139

    So, my 2500 RPM test passed with ease, but I'm still failing at idle. It's much better, but still a fail. I realized afterward that I had my vacuum advance connected to direct manifold vacuum instead of the ported vacuum, so it was probably seeing about 20 - 25° advance at idle. I've since moved it to the ported vacuum port, but have not had it retested. Do you think that just moving from manifold to ported vacuum will be enough to fix the idle test?
    Last edited by 85 Phoenix; 05-14-2019 at 10:22 AM.
    1985 Ford Bronco. 300 (305) ci inline 6. 9.1:1 compression, P&P head with enlarged valves, high flow exhaust. 32" BFG A/T tires. 5 speed ZF5 manual transmission with 3.55 rear end. Holley 550-850 2300 Sniper EFI.

  10. #10

    Default

    You might want to read this: http://www.idahovip.org/faq.html

    And especially "This program was established based on EPA standards, which state that a visual inspection shall be conducted on all applicable model years. The purpose of the visual inspection is to ensure the vehicle has all the emissions control devices originally required by the manufacturer pursuant to the requirements of the Clean Air Act and they appear to be in good working order. To remove or render inoperative any emissions control device or element of design installed on or in a motor vehicle or its engine in compliance with federal regulations is prohibited and constitutes “tampering.”

    “Tampering” is defined by the Clean Air Act of 1970 (revised in 1977) to be the removal or rendering inoperative of any emissions control device or element of design installed on or in a motor vehicle or its engine in compliance with federal regulations prior to its sale and delivery to the ultimate purchaser, or for any person knowingly to remove or render inoperative any emissions control device or element of design after such sale and delivery to the ultimate purchaser (Clean Air Act Section 203(a)(3)(A)).

    For the purposes of the Canyon County and City of Kuna I/M vehicle emissions testing program, vehicles that are found without emissions control devices will fail the emissions test until the vehicle is brought back into compliance with manufacturer emissions control device specifications. Consumers should be aware that if the emissions control device is not working properly and is still intact on the vehicle and the vehicle is under eight (8) years old and under 80,000 miles, they may qualify for a manufacturer warranty for emissions control devices.

    Waivers and extensions will not be granted for vehicles with tampering-related emissions test failures in accordance with federal guidelines (40 CFR 51.360

Page 1 of 3 123 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
About us
Holley has been the undisputed leader in fuel systems for over 100 years. Holley carburetors have powered every NASCAR® Sprint® Cup team and nearly every NHRA® Pro–Stock champion for four decades. Now, Holley EFI is dominating the performance world as well as our products for GM's LS engine. Holley's products also include performance fuel pumps, intake manifolds & engine dress–up products for street performance, race and marine applications. As a single solution, or partnered with products from other Holley companies - Hooker Headers, Flowtech Headers, NOS Nitrous, Weiand, Earl's Performance Plumbing, or Diablosport - Holley products can give you the edge you need over the competition.
Join us