For the knuckle draging carb guys - Team Camaro Tech
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post #1 of 14 (permalink) Old Apr 12th, 15, 04:16 PM Thread Starter
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For the knuckle draging carb guys

I have an AFR meter (Innovative MTX-L) in my car. Man does it make tuning a carb easy
My car used to stink (burning rich) so I was playing today.
I went from upper 11's and low 12's AFR with a cruise AFR in the low 12's also.
Started making adjustments and kept looking at the gauge...knew exactly what was good or bad in real time.
Now I idle in the upper 13's to low 14's, cruise in the mid 13's (2000-3000rpm) Exhaust smells better, picked up 1-2" more vacuum, idles smoother....All around better IMO.
Now I doubt any of this will help at the strip....just yet

Just a nice "tool" to help

68 Camaro~LSx ~all motor
1.54 60'--6.95 @ 98.45 660'--10.96 @ 121.53
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post #2 of 14 (permalink) Old Apr 12th, 15, 05:17 PM
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Re: For the knuckle draging carb guys

They were the only way to really know where you are at and what effect changes have on the car. How far out are your idle mixture screws? You may want to go with bigger idle air bleeds to get your lean cruise in the 14-15 range. What carb are you using?

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post #3 of 14 (permalink) Old Apr 12th, 15, 06:15 PM Thread Starter
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Re: For the knuckle draging carb guys

Kind of scared to go too far since last time at the strip I was playing with the timing to see what she liked....ended up with a few black specks on the plugs.
Went back to the best ET/MPH timing, and put in slightly colder plugs...all better

Mighty Demon 750 (DP carb)

68 Camaro~LSx ~all motor
1.54 60'--6.95 @ 98.45 660'--10.96 @ 121.53
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post #4 of 14 (permalink) Old Apr 13th, 15, 03:08 PM
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Re: For the knuckle draging carb guys

Good to see other 'see the light' and move to 21st century home workshop tools for dialing in engines
Your idle u should be able to get that to high 14s low 15s.. depending on the cam...
The simplest way is to set the idle mixture screws to 1 1/2 turns out then adjust the idle advance and the secondary butterfly stop screw.. but dont let the sec butterflies sit against the bores...
a wild street cam u may have around 20 degs on the idle, mild street 12 to 16....to establish what is need...but with a wilder cam u will not get the AFRS much more than mid 14s.
Same basically applys to dialling in the cruise mixtures and advance around the 42 degs.. thu the innovate u can hook in a knocksensor and get more safely without inaudible detonation

As to Strip/ WoT... u still need to keep AFRs rich in the mid 11s low 12s....once u have then there is just a matter of starting with total a little over advanced 36/ 38 then knock back in 2 deg increments till the power drops off.. about 2 deg above this point will be your best total for that mixture.
Once u have established each of the timing points.. idle, total cruise its just a matter of adjusting the cent advance (rounding off the tails of the counterweights) and springs, the VA advance and vacuum it works in ( where the lever starts and finishes in the rear slot) with a reasonable initial to give these.

Quote:
Kind of scared to go too far since last time at the strip I was playing with the timing to see what she liked....ended up with a few black specks on the plugs.
Went back to the best ET/MPH timing, and put in slightly colder plugs...all better
Change fuel, dynamic compression ratio, fuel mixtures and u will change the time the flame takes across the chamber to max piont of explosion (cylinder pressure) .. which means to bring that point back to the point between 12 and 18degs that suits your engine means a timing change at any given load/ rpms
Plug heat.. always run as cold as possible.. which often means a hotter plug on the cnr cylinders... usually the front 2.

My Spelling is not incorrect...it is creative

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post #5 of 14 (permalink) Old Apr 13th, 15, 04:00 PM
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Re: For the knuckle draging carb guys

Doug, what changes did you make?

Sean

1968 rs with an old school 354" SB2.2 pump gas motor.

Repetition does not transform a lie into a truth.

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post #6 of 14 (permalink) Old Apr 14th, 15, 01:57 PM Thread Starter
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Re: For the knuckle draging carb guys

Closed the secondary some, blew out the air bleeds with carb cleaner (been sitting and wanted to be sure), 1/16 or so turn in on the 4 corner IAB's, raised the timing a fuzz (2*) 700-1300rpm (idles at 900-1000).

Best thing was that any change, good or bad, could be seen in real time.

68 Camaro~LSx ~all motor
1.54 60'--6.95 @ 98.45 660'--10.96 @ 121.53
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post #7 of 14 (permalink) Old Apr 14th, 15, 02:12 PM
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Re: For the knuckle draging carb guys

Closed the secondary transfer slot then, and maybe leaned out idle by "opening up " the bleeds. Have you ever looked at how much transfer slot is exposed on both currently and before? Is the transfer slot between primary and secondary pretty close?

My old Prosystems carb was perfect on my 406, but with the new motor it has required some tweaking, I had to tighten up the transfer slot a bit, and increase the IAB. It runs killer now but richer at idle than I like, which is an HP 950 characteristic I guess.
For around $200 Prosystems will rework and update the tune up on their carbs, which is a good deal, but I like working through it myself so I know what it likes.

I'm comfortable tuning at the track for WOT with ear and plug reading, but an AF meter would sure be nice for around town cruising, I will probably invest in one eventually. You just have to know around town and WOT are going to be two different tunes probably.

Does you meter use two O2 sensors in the collector?

Sean

1968 rs with an old school 354" SB2.2 pump gas motor.

Repetition does not transform a lie into a truth.

Franklin D. Roosevelt
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post #8 of 14 (permalink) Old Apr 14th, 15, 03:42 PM Thread Starter
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Re: For the knuckle draging carb guys

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Yes, O2 in header at collector. I found the best price on Amazon too

As for the carb (before) was, slots were squared front and rear, carb has an "idle-eze" (Demon carb) which I have no clue if open/close/somewhere in between.
Never re-checked the slots after the adjustment...but rear is now closer to closed than front.
Seems to run pretty good, no "seat of the pants" feel of improvement to speak of.

Cool thing on the MTX-L is that you can add other meters (of their brand) and also "datalog" with a laptop.

Quote:
ALL-IN-ONE

(Wideband Controller integrated into the MTX-L gauge housing)

The new Innovate Motorsports Digital MTX Series Air/Fuel Ratio Gauge utilizes the only 100% digital Wideband air/fuel ratio technology on the market! The award-winning patented DirectDigital™ technology we use is faster and more accurate than common “UEGO” gauges and is now more affordable! In addition, the gauge features a water resistant casing, interchangeable faceplates and bezels, and 2 fully programmable linear analog outputs for use with aftermarket engine managements systems and dataloggers!

KEY FEATURES
• The only 100% digital wideband air/fuel ratio technology!
• Water Resistant 52mm (2 1/16”) round dash-mountable casing is perfect for automotive, powersports, marine, and demanding racing applications
• Built-in Direct Digital™ Wideband Controller reduces wiring and simplifies installation
• Wideband O2 Sensor is compatible with all fuel types (Leaded, Unleaded, Diesel, Methanol, E85, etc)
• Ability to calibrate O2 sensor for increased accuracy
• (2) 0-5v fully programmable linear analog outputs for use with engine management systems “closed-loop” and external dataloggers
• Interchangeable faceplates and bezels: Black and silver bezel, black and white faceplates included
• Large digital readout and programmable “Digital Needle” provides the functionality of a needle style gauge with the pinpoint accuracy of a digital display
Datalog using LogWorks on your PC
Serial IN and OUT ports allows for easy connection with other Innovate MTS and other devices

68 Camaro~LSx ~all motor
1.54 60'--6.95 @ 98.45 660'--10.96 @ 121.53
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post #9 of 14 (permalink) Old Apr 14th, 15, 03:44 PM
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Re: For the knuckle draging carb guys

Whatcha got against guys with long arms?
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post #10 of 14 (permalink) Old Apr 14th, 15, 03:53 PM Thread Starter
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Re: For the knuckle draging carb guys

LOL....nothing, I'm one also.

Just so many going EFI, and we're "old school", Neanderthals

68 Camaro~LSx ~all motor
1.54 60'--6.95 @ 98.45 660'--10.96 @ 121.53
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post #11 of 14 (permalink) Old Apr 14th, 15, 03:58 PM
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Re: For the knuckle draging carb guys

I like my Holly 780 Vacuum Secondary. It takes long arms to tune it.

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post #12 of 14 (permalink) Old Apr 14th, 15, 04:29 PM
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Re: For the knuckle draging carb guys

Did u preset the idle speed screw (primary butterfly ) adjustment to 1 1/2 turns before adjusting the sec butterfly stops?

Quote:
I'm comfortable tuning at the track for WOT with ear and plug reading, but an AF meter would sure be nice for around town cruising, I will probably invest in one eventually. You just have to know around town and WOT are going to be two different tunes probably.
The readings are in milli seconds so one knows what is happening at any given time, rpms during a track run when played back.. one picks up the smallest of millisec anomalies so easy that any plug reading seat of the pants stuff there is no way one can over the whole run... one can then fine tune these anomalies/ transitions between circuits so accurately... even something like a single partial misfire in a run will show up as a AFR rich spike
There is no way that sort of thing can be picked up any other way.

Track and road cruising can be the same
idle timing and mixtures are same for both
Cruise mixtures and timing are for just that
WoT mixtures and timing are for track and same for street.
Basically think of having 3 dizzies and 3 carbs all built into the same 'box'

Quote:
Does you meter use two O2 sensors in the collector?
one can run 1 or 2 (each side) also add other sensors like TP, IMAP, rpms, knock, crank position.
Basically what one is doing is monitoring the engine on a millisec scale then manually making adjustments to the 'anolog' timing carb etc
The only difference between this and modern ECU controlled engines is the ECU monitors and then can make real time adjustments to the electronic 'dizzy/ carb'

this is the 21 st century workshop tools on 20th century technology.. reading plugs that can only accurately tell u what happens at the end of the run during run off and rest is sort of guess work have gone....

Even on a daily driver it will pick up a plug that is just starting to break down way before. months before one can notice or even read anything.

My Spelling is not incorrect...it is creative

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post #13 of 14 (permalink) Old Apr 14th, 15, 04:55 PM Thread Starter
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Re: For the knuckle draging carb guys

Before tuning with a dataloger (not mine)


After tuning....(again, not mine)

68 Camaro~LSx ~all motor
1.54 60'--6.95 @ 98.45 660'--10.96 @ 121.53
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post #14 of 14 (permalink) Old Apr 14th, 15, 05:11 PM
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Re: For the knuckle draging carb guys

We tuned a 1200 horse motor with 3 systems at 1600+/- horse without the RacePak up and running, and after we got it up and running the tune up showed fine on the datalogger so we must have been pretty close tuning with plug color and heat. Probably quicker with the data chart though.
The plugs tell you a lot if you know what to look for... and at the end of the run if you shut it down the plugs show what they are up to when it matters, WFO.

Not taking anything away from computer logging of course, but there are a lot of guys doing it with plugs only, on the ragged edge with nitrous and having a great deal of success. Data logging lets you get the most though.


Nice to know you can run two sensors. I would think since the banks are totally separate and typically can run differently two O2 sensors would be the way to go.

I'll have to look into that meter, seems like good value for what it gives you.

Sean

1968 rs with an old school 354" SB2.2 pump gas motor.

Repetition does not transform a lie into a truth.

Franklin D. Roosevelt
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