A/F gauge reading incorrectly? - Chevelle Tech
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post #1 of 57 (permalink) Old Apr 6th, 20, 3:05 PM Thread Starter
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Tom
 
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A/F gauge reading incorrectly?

Hey All,

I have the basic VortecPro 467 in my 68 El Camino. Holley SA 770 carburetor. TH400 and 3.00 rear gears.

I added an Innovate Technologies AF gauge and a vacuum gauge to assist with carburetor tuning. I know that different engine combinations want different AF ratios, but after lots of tuning I think my AF gauge is reading incorrectly. Cruise is constantly reading in the mid-12s and occasionally in the mid-11s. My timing is good with about 18 initial and 35 total. Ive played with vacuum advance and have run as much as 10 in addition to the mechanical.

My spark plugs look good. I tried re-jetting the carburetor fo bring my AF reading up to at least the mid-13s but the car ran poorly. I finally took a half day to swap jets for best cruise vacuum. I ended up with the best readings with the stock jetting. My best overall performance is with the carburetor being at stock jetting but with a slightly larger accelerator pump squirter.

So with all of that, the car runs great with no smoke or the slightest amount of exhaust discoloration, but reads mid-11s to mid-12s on the gauge. Does this sound odd to the rest of you?

Thanks for any help,
Tom.
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post #2 of 57 (permalink) Old Apr 6th, 20, 3:24 PM
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OLIVER
 
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Re: A/F gauge reading incorrectly?

I had a AF gauge go funny all of a sudden , I knew my tune was on point , then I found that the Bosch sensor went bad , changed the sensor and all good again.

Oliver
Milano , ITALY

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1969 396 SS monaco orange (72)
468 Vortecpro 585 HP back to street cruiser
M20 4 speed - 3.31
Prosystems 1000
BEST ET 11.62 (with 4.10)
BEST MPH 121
BEST 60 FT 1.64
4000 lbs street car


1969 El Camino Street Strip
467 Vortecpro Tunnel ram 730+ hp TH400
BEST ET 10.67 @ 127 1.56 60FT
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post #3 of 57 (permalink) Old Apr 6th, 20, 3:42 PM Thread Starter
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Tom
 
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Re: A/F gauge reading incorrectly?

Quote:
Originally Posted by oliver69 View Post
I had a AF gauge go funny all of a sudden , I knew my tune was on point , then I found that the Bosch sensor went bad , changed the sensor and all good again.
Makes me wonder even more. This does use the Bosch wideband sensor. It has read in this same range ever since I installed it. Do these readings also seem off to you? Id think that if I were truly running that rich Id have symptoms.
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post #4 of 57 (permalink) Old Apr 6th, 20, 3:53 PM
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My innovate required a "free air calibration" before use. Did you perform any required calibration before installing it? If not, start there. Grounding is very important, make sure you followed the recommended grounding scheme.
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post #5 of 57 (permalink) Old Apr 6th, 20, 7:40 PM
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Not hi tech But pull Sensor out to see what it looks like cruise at 11-12 is way rich See if sensor is real sooty after a long cruise

66 CDN Malibu SS A51,L34,M20 Aztec Bronze

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post #6 of 57 (permalink) Old Apr 6th, 20, 7:46 PM
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Re: A/F gauge reading incorrectly?

if you have ran any race fuel with lead in it they dont like that either.
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post #7 of 57 (permalink) Old Apr 6th, 20, 8:50 PM
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Re: A/F gauge reading incorrectly?

There's calibration you can try.

https://www.innovatemotorsports.com/...rint%201.2.pdf

Jim

77 Monte
421 Profilers ported by Eric Weingartner, Straub HR 3200 conv. from Jake 200-4r w/ 3.73's
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post #8 of 57 (permalink) Old Apr 7th, 20, 11:30 AM Thread Starter
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Re: A/F gauge reading incorrectly?

Quote:
Originally Posted by Scott65 View Post
My innovate required a "free air calibration" before use. Did you perform any required calibration before installing it? If not, start there. Grounding is very important, make sure you followed the recommended grounding scheme.
Ive done it twice. Once upon initial install and again after a few months of use. No change in the average readings.

What does your gauge tell you when youre cruising down the road?
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post #9 of 57 (permalink) Old Apr 7th, 20, 11:31 AM Thread Starter
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Re: A/F gauge reading incorrectly?

Quote:
Originally Posted by CDN SS View Post
Not hi tech But pull Sensor out to see what it looks like cruise at 11-12 is way rich See if sensor is real sooty after a long cruise
Thats the thing: No soot or smoke anywhere. Tailpipes and spark plugs are clean.
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post #10 of 57 (permalink) Old Apr 7th, 20, 11:32 AM Thread Starter
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Re: A/F gauge reading incorrectly?

Quote:
Originally Posted by Mike 70SS View Post
if you have ran any race fuel with lead in it they dont like that either.
Nope. Just 91 octane pump gas since I got the car.
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post #11 of 57 (permalink) Old Apr 7th, 20, 11:37 AM Thread Starter
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Re: A/F gauge reading incorrectly?

Quote:
Originally Posted by 77 cruiser View Post
Yeah... Ive calibrated twice. My gut feeling is that the gauge is not, and has never been reading correctly. Its hard to imagine cruising around 12:1 without rich symptoms. Occasionally on a cold start with no choke it will read in the 15 range. That often gives me hope that it is reading correctly, but it quickly settles into that mid-12 range soon enough.

And just to clarify, my exhaust system is tight. The sensor is mounted about 15 up from horizontal about 6 past the header collector.
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post #12 of 57 (permalink) Old Apr 7th, 20, 11:49 AM
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Re: A/F gauge reading incorrectly?

I thought I'd throw it out there just in case you hadn't.

Jim

77 Monte
421 Profilers ported by Eric Weingartner, Straub HR 3200 conv. from Jake 200-4r w/ 3.73's
Machine work by Torvinen's machine
11.93 @ 112.7 & tuning
67 Imp.SS for the wife 275 hp 327-TH350
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post #13 of 57 (permalink) Old Apr 7th, 20, 12:05 PM Thread Starter
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Re: A/F gauge reading incorrectly?

Quote:
Originally Posted by 77 cruiser View Post
I thought I'd throw it out there just in case you hadn't.
Believe me; I appreciate ANY suggestions. I wish there was a way to double-check these things. I think my only hope is to suck it up and buy another one, probably from a different manufacturer, and replace it to see how it reads. Or just remove it and be happy with my old-school tuning methods. It drives me crazy that this car seems to be running great but the fancy electronic gizmo is telling me something else.
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post #14 of 57 (permalink) Old Apr 7th, 20, 12:26 PM
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OLIVER
 
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Re: A/F gauge reading incorrectly?

Quote:
Originally Posted by any4xx View Post
Yeah... Ive calibrated twice. My gut feeling is that the gauge is not, and has never been reading correctly. Its hard to imagine cruising around 12:1 without rich symptoms. Occasionally on a cold start with no choke it will read in the 15 range. That often gives me hope that it is reading correctly, but it quickly settles into that mid-12 range soon enough.

And just to clarify, my exhaust system is tight. The sensor is mounted about 15 up from horizontal about 6 past the header collector.
does it move around, when you step on the gas ? or let off the gas ?

if it keeps reading rich all the time no matter what I would think the sensor went bad , this is what happened to me ... just kept reading rich all the time regardless

you can replace the sensor ,I believe 50 $ or so

Oliver
Milano , ITALY

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1969 396 SS monaco orange (72)
468 Vortecpro 585 HP back to street cruiser
M20 4 speed - 3.31
Prosystems 1000
BEST ET 11.62 (with 4.10)
BEST MPH 121
BEST 60 FT 1.64
4000 lbs street car


1969 El Camino Street Strip
467 Vortecpro Tunnel ram 730+ hp TH400
BEST ET 10.67 @ 127 1.56 60FT
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post #15 of 57 (permalink) Old Apr 7th, 20, 12:29 PM
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Re: A/F gauge reading incorrectly?

Oliver, good to hear from you.
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