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Discussion Starter #1
Well, I know people have been asking about the fuel economy of carb vs EFI, difficult to relate though it may be, and I wanted to share my experiences.

The rear is an 8.2" w/ Yukon Posi 3.08. The tranny is a TKO-500 with the 3.27 1st gear. The engine is a BluePrint full Roller 383 430hp, coil in cap dist, Edelbrock dual plane EPS, with electric fans. For a carburetor, I was running a Edelbrock 1406 (it's a 1405 set to run leaner from the factory).

Before I moved out to AZ, I used to drive 80/20 highway/city and still have receipts showing 22.9-23.3 mpg per tank on the carb.
Driving from The West Valley in Phoenix, through Phoenix to 87 and then up through the mountains to Flagstaff with the AC on and two kids in the back, we averaged high 18's in the mpg. That includes the 5K ft elevation change and the city driving through Flagstaff.
Once I installed the Sniper system, choose stock cam in the set up Wizard regardless of what your cam is..., I drove it around and let it learn how to be happy. Once it was, I adjusted the Idle AFR to 14.0, The WOT AFT to 13.0 and the Cruise AFR to 15.0. She was happy and had no temp issues of lack of power in Lean Cruise, so I upped the AFR to 15.5. With those settings, I am averaging over 25 mpg. Pure Highway @ 65 is over 27mpg. For my next trick, I'm gonna try and lean her out some more and try to find a stock GM distributor that I can lock out and use the Sniper System to control the timing.

- Rob
 

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Pretty dang cool information Rob. I just installed one of these on my car and though my motor configuration isn’t similar in cubic inches the info is somewhat applicable. Thanks for posting. I may hit you up in the near future to pick your brain on how to do this myself with my sniper.
 

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Discussion Starter #4
Oops! 91 Octane weighs more than 87..... So, now I'm at 26 mpg at 65 at 15/1 afr. My bad....
 

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That's some really nice MPG Rob and I have been reading a lot about it. Please post more info as you do more test settings I am very interested. Thanx for posting what you did
 

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Discussion Starter #7
Well, she did not like the 16/1 cruise.... However, I believe it is because the parameters of Idle, Cruise and W.O.T. are not ideal for my car. It would seem that the closer I get to WOT, the richer the afr would get; and it does, but not until around 30% throttle!!!!! So, hear I am trying to accelerate for a pass on the highway at 65 mph in 5th at about 1650 rpm. 16/1 ain't gonna cut it. I suppose I may need to buy the $50 cable so I can adjust those parameters on my laptop. Sigh....
 

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Nice...my problem is keeping my foot out of it :eek:

Always blip the pedal on under passes, city streets, and such :eek:


I may go FI one day, buddy has a FITech I can try, but its the smaller one which might be too small for my motor :(
 

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Not going to like 16- 1 afr on any motor and detonation will kill the motor let alone the mileage stick around 14.8 - 15.

Have you set it up to let the sniper control timing? Doing so will get you the best of both mileage and throttle response. You can use an adjustable MSD rotor.
 

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Not going to like 16- 1 afr on any motor and detonation will kill the motor let alone the mileage stick around 14.8 - 15.

Have you set it up to let the sniper control timing? Doing so will get you the best of both mileage and throttle response. You can use an adjustable MSD rotor.
Well said John. Yes a MSD/Holley dizzy will plug and play with your configuration.
 

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Discussion Starter #11
I have not a dual sync or msd; they're expensive!!! I'm searching for a stock gm that'll drop in with the Sniper.
 

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Discussion Starter #13
how well does a efi self learn work with a manual tran
Well in my experiences! The one important item would be to wire the Sniper EFI A/C ground to a relay triggered by the compressor. That way the EFI knows the added load is from the AC. It will then bump your idel up by 100 and trigger your E Fan if you have one. I really have no complaints about the system except the need for a $50 cable to download the MAP to my PC if I want to tweak certain perameters.
 

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Haven’t really checked my mileage but I don’t think it’s even close to that. Mine is in a 69 Camaro with a mild camed 350/700R4, I better go through the wizard again
 

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That's pretty phenomenal mileage from a 430HP SBC. Cam specs?
 
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