How Much Fuel Economy Does EFI Gain?

I agree 100% with you Yatzee except for having dual O2 sensors. Efi is better in every way except it ain't what it came with, so for me if I was given a complete Efi for my car.I doubt I would install it. I would sell it.
And as they say on Shark Tank," And for this reason I am out".
 
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i was thinking on getting a holley sniper setup until i found out i need to use a single plain intake or a inch open spacer just so the M.A.P. can good signal and no make it run like crap on a dual plain intake and that i already have a free oem 4bbl manifold that my brother never used decided to go with an AVS-2 instead when i get to that stage in my project
 
I'm sure a well setup EFI on a vintage V8 must be amazing.
 
twostick said:
Once you get over the starts and idles first time every time no matter what and the faster than instantaneous throttle response, it's pretty ho hum. Lol.

Kevin
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I bet!! I get that though on my old 1986 Omni glhs shelby with +40% injectors and custom cal computor,,ho hum,,,
For my fat old ***** 69 440 I want what she was born with. I am over modified.
 
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I'm still tuning a little on mine but my 360 in my 68 fury gets 7mpg. Went down from 11mpg with a good tuned holley. Dont know how, AFR numbers are the same...

EFI is also essentially a double pumper. Runs on all 4 all the time!
 
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Turboomni said:
I have often wished I had two wide band O2 sensors, one on each bank of cylinders on my Fury. It would make tuning the carb so much easier and factual with data I can see.. The efi systems I see offered for our v8s is a closed loop system of course but only one O2 sensor is used which is kinda too bad. It just assumes the other bank is acting exactly like the one it is monitoring if you have dual exhaust.i have often wondered how good a tune I could get on a carb with wide band O2 sensors to see what is going on. Then accurately tune the carb jets,metering rods etc. To me at.least it sounds fun.
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I had tuned my Holley carb with a wideband, it is worth the money! Buy a gauge, tune it with it, sell the gauge. You'd be surprised how good you can tune the carb like this!
 
Knebel said:
I'm still tuning a little on mine but my 360 in my 68 fury gets 7mpg. Went down from 11mpg with a good tuned holley. Dont know how, AFR numbers are the same...
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I am sure if you asked and stated what Holley carb and cfm you would get alot of info. I run a edelbrock 1406 on a stock 440 and it is 600 cfm. Looking at the Edelbrock site anything over 6300 rpm would be a restriction but I never go there.
 
Turboomni said:
I am sure if you asked and stated what Holley carb and cfm you would get alot of info. I run a edelbrock 1406 on a stock 440 and it is 600 cfm. Looking at the Edelbrock site anything over 6300 rpm would be a restriction but I never go there.
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Holley Street Avenger 670cfm modified with annular boosters. So maybe 630-650cfm

Its weird cause when you let off the gas with the carb it always went pig rich. The efi does not do that and either stays at commanded afr or depending on, shuts off fuel. Yet still my milage decreased.
 
That is weird that it goes rich like that. I have no experience with Holley carbs, just the Edelbrock 1406 my car came with and my very distant experience in the 70's and early 80's which I don't remember much.
 
Gas mileage matters if it’s your daily 75 mile commuter which I doubt many of us do. For me kicking in the secondaries on a nicely calibrated 4 barrel is part of the classic program. I love efi on my Harley and my truck but they came that way.
 
Turboomni said:
That is weird that it goes rich like that. I have no experience with Holley carbs, just the Edelbrock 1406 my car came with and my very distant experience in the 70's and early 80's which I don't remember much.
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Nono. I USED TO have the holley. I now have the efi and the efi gets worse mpg than the holley!
 
IC sorry for the misunderstanding. That seems very odd.
 
I just sold my sniper set up. For what’s worth the EFI was a fun experience and experiment. It honestly came down to feeling like I committed a sin doing the conversion.

My install was easy, I followed all the directions and never had a problem through a summer of hard driving everyday. The mileage was good too. For me it was a personal preference. At the end of the day, I like being the guy that tinkers with his car and carb

The Quick Fuel 735 VS carb I replaced the Sniper with is just about flawless. I’ve been playing with the replacement airbleeds and jets and it’s more fun for me than clicking the keyboards.
 
Turboomni said:
That is weird that it goes rich like that. I have no experience with Holley carbs, just the Edelbrock 1406 my car came with and my very distant experience in the 70's and early 80's which I don't remember much.
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I'd suspect a blown power valve. High vacuum will suck fuel thru that circuit.

Kevin
 
Knebel said:
Nono. I USED TO have the holley. I now have the efi and the efi gets worse mpg than the holley!
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What EFI system?

Running closed loop with an O2 sensor it should do at least as well as a carb.

Is the timing controlled by the ecm? You need to verify that the indicated timing is the same with a timing light at the crank.

If it is like my old Holley Commander Pro, the 02 sensor needs to be free air calibrated so it sends the correct info to the ECM. If it lies to the ECM the ECM assumes it's the truth. It could be indicating stoic and still be pig rich.

Kevin
 
its a Fitech EFI 600HP. Im tuning out a lean tip in and richrbog out now, otherwise it seems to run great. Plugs seem okay too. using fuel only at the moment.

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I'll assume a factory electronic distributor.

Does the mechanical advance work?

Is the vacuum advance hooked up and does it work?

In comedy and internal combustion engines, timing is everything.

Kevin
 
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