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EZ EFI 2.0 Throttle Body System Vehicle #2 - An '81 GMC

Discussion in 'FAST Support Forum' started by A A, Jun 5, 2016.

  1. J.K.

    J.K. Member

    Joined:
    Aug 7, 2016
    So I tried 14.4 idle, 14.7 cruise. Bumped up the idle to 900 for the time being. Sounds a bit fast but it keeps the map around 57-60 idling. How does one determine the ideal idle afr? Trying to understand why some efi guys are getting very lean idle afr, some in the 15's....while others tune for the low to mid 13's at idle. That's such a broad range.

    Back with my carb I would get idle about 14.5, but any leaner would cause the motor to die. Best idle afr tended to be in the 13.5 - 13.8 afr. This gave the best off idle tip in quality. Obviously the efi will want to keep itself running, so I find it harder to know where that sweet spot is. It doesn't just stall out like a carb to let me know it's too far.
     
  2. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Use a vacuum gauge to initially determine idle A/F while tuning the idle (initial) timing adjustment also. You want the highest steady vacuum using both adjustments. The front and rear throttle blades may also need adjustment. While juggling settings, the MAP will lower as vacuum increases. Later, you use the color of the outer half of the inner ceramic firing end and the O2% reading. O2% should settle close to zero at a steady fully warmed idle with the correct idle A/F. Idle A/F tends to be richer at idle due to slower runner speeds there. A camshaft design that also lowers power at idle (performance cam that increases power later in the RPM band) requires more fuel at idle. Most all engines need more fuel at idle to maintain more power at idle.

    With your extreme FI camshaft, you should be getting a MAP of 57-60 or less at 750. Something isn't tuned correctly. Your rear throttle blades may be opened too far at idle - this will prevent proper IAC control and will give a false adjustment correction setting. With everything set correctly, your fuel maps should correct to easily allow a lower idle.

    What you're describing happened to my 406 at idle - during my earlier tuning after changing to a single plane intake. The dual plane intake would never allow an idle below around 900 regardless.

    I had to keep the idle higher until the plug heat range, initial timing, and rear throttle blades were correctly adjusted with the new Vic Jr intake. I also had a third factor that happened during this time - bad fuel from a local gas station near my home. Once I replaced that fuel with fuel from a different station, I was able to quickly correct the plug heat range and adjust all settings for a smooth 750 idle in and out of gear - even as low as 700 without problem. Before that, I was getting all kinds of misleading readings that appeared to be what the engine wanted. If my other vehicles hadn't started running rougher than their usual smooth as silk, I might have overlooked the fuel as an issue. I had been buying most of my fuel from that nearby station for years without problem. I haven't bought fuel there again, and I haven't had any more fuel problems.
     
  3. J.K.

    J.K. Member

    Joined:
    Aug 7, 2016
    It's a bit frustrating that these throttle bodies are shipped incorrectly set up in the first place. Mine came with the secondary linkage rod set up in the top hole of the primary lever, and set loose on the secondary so that it would function just like a Holley double pumper carb would. Me being new to efi, I certainly didn't know better and ran it like that for a while. It was by lots of efi searches on the internet that I just happened to stumble across a proper FAST throttle body linkage set up procedure on a site that had nothing to do with FAST products. Then is when I realized it was set up completely wrong and the secondary was suppose to move the same time the primary moved.
    I have fine tuning to do, but it does run and drive so much better than it did in the beginning. Back then I was ready to chuck it in the scrap. Now it's drivable and pretty decent, just not perfected yet. I still plan once I can afford it I will get the xfi ecu. This way I can go back to my xr294hr cam. The xfi cam I have does the job but I still feel as I made alot more torq in the mid to upper rpm with the other cam. And to me it had a much angrier tone once in it's rpm happy spot than the xfi cam does. Also the xfi cam makes for much noisier valvetrain. My other cam not nearly as noisy.
    In the meantime would you set up idle with both butterflies closed, and both opened equally for proper set up? I think mine are close, but primary probably open slightly more than secondary. My secondary I think was set to just touching the screw, so as to not have the blades bind in the bores.
     
    Last edited: Sep 23, 2017
  4. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    This new cam is correct. You needed it because of your compression ratio - to help control pre-ignition/detonation. It may cause a little more valvettrain noise due to the ramp design, lifters, and engine oil pressure. But, the benefits are far greater using it - including its ability to make more mid range and top end power over your previous cam - with improved idle due to its increased idle vacuum design.

    Engine exhaust tones are very deceiving. Compression, fueling, and timing have a lot to do with this. Some settings can make the engine sound stronger, but the reality is the engine is running ragged and erratic and producing lower torque. With the old cam, you were likely experiencing detonation - and that will give that "angrier" exhaust note,

    I've never seen a FAST throttle body come with the linkage set up wrong from the factory. I have seen the rear blade screw adjustment set incorrectly.The linkage is supposed to be progressive with the 2.0 TBI unit. If yours isn't, you've found the cause of more problems. - as this will not allow the adaptive learning to work properly at building fuel maps. You shouldn't need to fool with the rear throttle blades unless running over 500 cubic inches.

    The secondary linkage should be in the lower of the two holes on the main throttle. The linkage should be "loose", per design. This allows the rear throttle to close using its shaft mounted spring - and keeps the rear throttle closed during part throttle operation until the engine needs and can use the added air from the rear blade actually opening. Not having it set this way also affects engine deceleration operation while driving - further upsetting fuel maps.

    With the linkage correctly adjusted, the main throttle fully opened, the rear blade should be at a slight angle from straight in the rear throttle bore. Too much air from the rear throttle blade at part throttle will cause a stumble, and will not allow the adaptive learning to create proper fuel maps. Easier, the linkage adjustment will have the end of the rod slightly inside the back of the adjuster nut instead of sticking out the back of it
     
    Last edited: Sep 23, 2017
  5. J.K.

    J.K. Member

    Joined:
    Aug 7, 2016
    Interesting, I will have to look at that setting again. I was under the assumption since efi works different than carb, the front and rear blades needed to move the same for a balanced air flow. Maybe I'm misunderstanding the terms "progressive" and "1:1". I will look again at the manual, but I thought I read somewhere in the manual that the front and rear blades needed to be as close to 1:1 as possible.

    I found it in page 63, just a few lines down. It says a 1:1 set up is preferred over progressive. Yet they seem to be all shipped with progressive setting.
     
    Last edited: Sep 23, 2017
  6. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Yeah, I see that on page 63. Crazy! The design of the throttle parts is for progressive movement not 1:1. All engines cannot accept the rear throttles opening at the same time as the main throttle begins to open - and will stumble. 1:1 basically will defeat much of the ability of the ECU controlled IAC.

    The angle of the rear throttle blades will basically look straight with the main throttle fully open.
     
    Last edited: Sep 23, 2017
  7. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    On one of my 2.0 throttle bodies, the rear throttle blades were sticking slightly open after some backfires once. With the slack the factory designed into the rear setup, I was able to find and correct this with the main throttle closed. Once the rear blades were again closing properly, I re-adjusted the IAC and TPS - restoring perfect running at idle. The problem has never re-occurred.

    As the main throttle opens farther, the setup does transition to more of 1:1, but this is still a progressive setup.
     
    Last edited: Sep 23, 2017
  8. J.K.

    J.K. Member

    Joined:
    Aug 7, 2016
    I'll give it a try. Mine is 1:1 now, runs pretty good though. Don't know till you try right? It may get better yet.
     
  9. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Be sure to "blip" that rear throttle several times with the main throttle closed. This will let you know if the rear throttle is sticking open.

    Maybe this will allow the ECU build better fuel maps.
     
  10. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Decided to start working for better fuel mileage from the GMC today. With the regular gas I use, 28 total mechanical degrees is all this engine will stand using a 4000 RPM slope - before pre-ignition starts. The default 60% vacuum load setting also never allowed any added vacuum timing on this engine. I bumped my vacuum timing from 6 to 10 degrees - keeping the 45% load figure I was already using. I felt the engine smooth out a bit more between 1400 and 1600 RPM, and checked the plugs. The plugs looked good, but were beginning to soot some on the ceramic insulators. I pulled idle A/F from 14.3 to 14.5, and reset cruise A/F from 14.7 to 14.8. The plugs began burning cleaner again, and the engine was responding well and sounding ever so slightly mellower at the exhaust through the RPMs. I then took the vacuum to 20 degrees and went for a drive. There was no problem with mild or hard acceleration (no pinging), and a later check of the plugs showed no oil deposits or other problems. I'm sure hydrocarbons are down while nitrides have risen. There is no doubt in my mind that mileage just jumped up from the 12 MPG I had been getting. I'll be keeping these new settings to see how much my mileage improves - so long as the engine continues to run sweet at them.

    Edit:
    Decided 48 degrees total timing was too aggressive a jump and pulled the vacuum advance back 4 degrees to 16 degrees for a total of 44.
     
    Last edited: Oct 25, 2017
  11. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    After putting the GMC through some aggressive paces, I found a small spot of oil on two sparkplugs, and the side electrode heat line appeared closer to the plug base. The slight oiling was nothing that wouldn't burn off quickly in normal driving. I dropped the vacuum load percentage to 40% and put the GMC back through the same aggressive tests as before. The spot of oil is no longer appearing to the inside ceramic of the two plugs, and the heat line appears normal again in the affected sparkplugs.
     
    Last edited: Nov 4, 2017
  12. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Decided to check the headers for any leaks today - and found a few very slight ones. Some bolts were a little loose, but not bad for the first time since the headers were installed.

    While the engine was still cold, I turned the air conditioning on and dropped the transmission in gear. Noticed the engine used all of the default 5 degrees of idle trim - increased this to 8 degrees and saw that was the sweet spot as the engine warmed. Once the engine warmed, I increased the initial timing from 20 to 24 degrees, and saw the engine liked this also in drive with the air on. IAC became more stable and low engine RPMs became smoother. The engine is sounding even sweeter out the exhaust as I move the RPMs up and down.

    I should start seeing even more fuel use improvement. I was expecting I could improve this along, and the EZ EFI 2.0 ECU
    appears to be processing the information it sees more efficiently. Not bad for an engine that has more compression than I remembered building it with - and the performance cam I matched to it in 1990.
     
  13. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Here are the previous settings:

    Initial timing 20 degrees
    Idle trim 5 degrees
    Idle A/F 14.4
    Cruise A/F 14.8
    WOT A/F 12.7
    Slope All-In 4000 RPM
    Mechanical All-In 28 degrees
    Vacuum Timing 7 degrees @ 45%
    Total Timing 35 degrees on Standard Oil Regular (Chevron 87 Octane with Ethanol and Techron)

    .. and here are the current settings:

    Initial timing 24 degrees
    Idle trim 8 degrees
    Idle A/F 14.5
    Cruise A/F 14.8
    WOT A/F 12.7
    Slope All-In 4000 RPM
    Mechanical All-In 28 degrees
    Vacuum Timing 16 degrees @ 40%
    Total Timing 44 degrees on Standard Oil Regular (Chevron 87 Octane with Ethanol and Techron)
     
  14. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    After noting the idle trim compensation operation with the air conditioning on, transmission in drive, I have now turned on the full 12 degrees of idle trim.
     
  15. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    While 12 degrees of idle trim appeared to help idle with the air conditioning on in drive, It seemed to be creating other issues at RPMs just under the idle trim cutoff. I have now turned off the idle trim. Throttle increases from 750 idle RPM up are now smoother. The trade-off was IAC is now pegging in drive with the air conditioning on at idle, and quick throttle return from higher RPMs to idle dips to 400 for a moment If I add any idle trim back, it will probably be only enough to aid in holding RPMs from dropping too far below 750 with a quickly closed throttle. I then dropped the initial to 22 degrees.

    I'm also getting very slight cold and warm idle improvement using a 14.6 idle F/A target. Engine is sounding very sweet now in 750-1050 RPM throttle application.
     
    Last edited: Nov 9, 2017
  16. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Found 1&2 cylinder sparkplug ceramic glazed and fouling. Replaced the factory heat range UR-4 plugs with colder UR-6. Engine idle smoothed back out. Cold start still fine with UR-6 plugs and current F/A ratios.
     
  17. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Well, this has been strange. No errors, no IRM #s, no header leaks. But, I had to drop idle back to 14.5 A/F, cruise to 14.7 A/F, initial timing to 20, and had to pull the vacuum timing back to 12 degrees. I also pulled the total mechanical timing back to 26 degrees. The plugs are looking correct again. I'll have to drive it a while before trying to get the mileage higher again. The one variable that changed, before losing ground, was I had changed over to a tank I had filled two months back. I'm betting I mistakenly pumped mid-grade fuel in the tank I had been using in my earlier tuning - and didn't realize it. Engine is running sweet again. At least I have some timing numbers for mid-grade fuel now. For now, I'll keep running the UR-6 plugs.
     
    Last edited: Nov 13, 2017
  18. Pfingstl

    Pfingstl Member

    Joined:
    May 30, 2016
    Location:
    Denmark
    We have 95 Octane as the standard gasoline (+ $6 / Gallon) and Shell sells 99 Octane - of course even more expensive!!
    Only unleaded.

    And bad fuel isn't nice. Just service some old classic cars with 5-8 year old fuel. No power and the smell.......................................
     
    A A likes this.
  19. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Hi Jens,

    We/re lucky here - 87 Octane @ $2.18 a gallon. 89 Octane @ $2.48. 92 Octane @ $2.88. Now in Venezuela, it was pennies a gallon for decades - it just went up 60 times to about $2.00 a gallon. Still not worth a trip there. ;)

    Last time I checked, 5 gallons of 100 octane fuel here was about $70. :(

    Yep! I well know that old fuel smell - I bought some classics that had fuel 10 years old and more. It's bad to varnish up fuel systems also. It's best to drain and use that old stuff carefully for outside fire starting - and use a good fuel system cleaner to flush out the varnish. Old oil can be about as bad too. If it isn't contaminated too bad, I filter and mix it in with my diesel fuel and burn it. If it's really bad, I mix it with the old bad fuel - and use it outside to burn debris. It still has an odor that doesn't soon go away.:eek:
     
  20. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    The reason I switched tanks while tuning.... The tank started showing empty at the gauge. Turned out to be the in-tank fuel pickup assembly - as the tank was still almost three quarters full. Probably good it happened now and not later. I also finally remembered why I had put higher octane fuel in that tank - I had heard some clicking injectors at startup I wanted to clean. The higher octane worked and stopped the clicking from the injectors. I had filled the TA with the same higher octane fuel on that same day. My old memory is throwing curves at me. Hopefully, I won't forget what fuel I have in the TA.
     

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