Tuning a TBucket Dart 400 cuin Engine

I get the same message error Rick.

The Demon should be easy to tune.
Done in 1 day Max Time.

PIA.
IF Mine be set aside.

Pull a 8 spark plugs.
Orginize.
Label each from respective cylinder.
Photograph and post the pictures .

Old School way often the best still with Carburators.

Worked for every drag racer 1950- 2001.
 
I sure wish AEM had a class for reading their plots and identifying changes to be made.
I feel lost about what I've done and what to do next. Just have to keep plugging along
until something makes sense to me.

The plot below ........
The primary plot in the thin crisp line and represents the last run with the change to the
bigger PVCR of .070 inches. The secondary plot is thicker and is for comparison. A before
and after comparison.

Between the red lines looks like a change caused by the Power Valve Channel Restrictors
(PVCR), but the change could NOT happen until the power valve opens at it's rated 6.5 inhg,
noted by the vertical blue line. That change could be caused by how I ran the test differently
such as starting at a different RPM (Green Line)

I have to give it up to Bytor, he seemed to have a good handle on this stuff.

2015-08-13-1844.jpg
 
Indycars said:
I sure wish AEM had a class for reading their plots and identifying changes to be made.
I feel lost about what I've done and what to do next. Just have to keep plugging along
until something makes sense to me.

The plot below ........
The primary plot in the thin crisp line and represents the last run with the change to the
bigger PVCR of .070 inches. The secondary plot is thicker and is for comparison. A before
and after comparison.

Between the red lines looks like a change caused by the Power Valve Channel Restrictors
(PVCR), but the change could NOT happen until the power valve opens at it's rated 6.5 inhg,
noted by the vertical blue line. That change could be caused by how I ran the test differently
such as starting at a different RPM (Green Line)

I have to give it up to Bytor, he seemed to have a good handle on this stuff.

View attachment 5983
Click to expand...

For some reason, your chart pictures wont open....

Says,
Grumpys Performance Garage - Error
You do not have permission to view this page or perform this action.
 
They should be full size when you view my post. What do you see.... a thumbnail?
Any messages when you try and open the graphic?
 
Indycars said:
They should be full size when you view my post. What do you see.... a thumbnail?
Any messages when you try and open the graphic?
Click to expand...

Thumbnail... Looks like a permission issue with my login. I just realized I can post a picture ether. Strange.

I get the following message.

Grumpys Performance Garage - Error
You do not have permission to view this page or perform this action.
 
That's exactly the same error as Mathieu posted above.

I made some changes, try again after logging off and back on.
 
"For some reason it was set to NO for viewing and posting attachments."

where? in what permission chart ?
Im trying to run down and correct glitches in the software, and can use some related info for sure, I'd like to get that corrected ASAP
 
I have a different approach to tuning with o2, probably not the best. and my IAB and IFR and PVCR are fixed(cannot tune that part of the carb) and i think its a good thing haha.
I usually start with the idle mixture, then main jet and do the accelerator pump last.(and i think the accelerator pump is the least funny of the 3 to tune).
What i really need help with is ignition timing tuning.
 
You are making good progress. It is a challenge to make repeatable runs. I had a route I would drive that had a nice hill that allowed me to make a nice repeatable loaded run. The key is to learn how to very slowly accelerate and to be able to repeat it. You don’t want to press the gas pedal too fast and cause your accelerator pump to kick in and skew your graph.

Your correct, the PVCR change should not affect the area in between the red lines. It would be good to see the TPS graph on your next runs as well.

A few recommendations:
Only make one change at a time and don’t make any big jumps in sizes. You can easily go down a rat hole with this stuff if you don’t keep track of exactly what you changed.

Focus on the fuel curve for now not so much on the AFR. You don’t want to see any big rich to lean or lean to rich swings as your going from idle to WOT. You want to work on the “tilt” of the fuel curve and get is as flat as you can. You will never get it perfect, just keep that in mind. Your IAB, HSAB and emulsion holes adjust the curve “tilt” Once you have a reasonable flat curve, you can move the AFR up and down with the IFR,PVCR, and pri/sec jets.

Focus on one circuit at a time. For example, work on your transition slot, then figure out when your primary circuit starts up and how strong, then power valve, then WOT.

If you find yourself making too many changes and not seeing results. Stop, reset the carb to it’s baseline settings and start over..

The idle air bleeds are tricky boogers. As you increase the IAB size, your allowing more air in and causing more emulation. This causes the transition circuit to come on strong/rich. The air mixed in the fuel makes the mixture lighter and easier to pull into the manifold. This works to a point, if you go to large the effect reverses and leans out. If you reduce the IAB, your reducing the emulation effect and changing how the transition slot starts up. It will start us a little softer. Once you get the transition curve flat, you will need to change the IFR and idle screws to set the AFR where you want it.

Here's an air bleed and emulsion wright up and graph that help me grasp this stuff. Don't use the info in the graph literally. It just represents how the curve changes as the air bleed size changes and which ones have the most effect on the curve.


Air%20Bleeds.jpg MainCircuitGraph.GIF
 
Thanks that's alot of good info that will take me awhile to absorb.

Part of my problem is the lightness of the car. I run my tests in 3rd gear and start the
test once the car has reached 3rd gear. If I go slowly on the application of the throttle
I will be going in excess of 100 mph before I reach WOT. I'm getting nervous by then.

I've not touched the emulsion holes, don't have any info that gives me an idea what
they do. I've read the Innovate articles and they are pretty complete, but they don't
touch the emulsion holes that I can find.

I feel the IFRs are pretty close. Initially the idle mixture screws started at 5/8 turn
out, now they are setting at 1.75 turn out. The AFR is 14-14.5. The primary TSlot is at
.020" plus a 1/2 turn out on the idle speed screw. Secondaries are at .020 inch showing.

Thanks for the help, it's greatly appreciated !!!
 
Just to be carefull, did you see that lean out at 80% TPS on every pass. too lean near wot not good.
Can this be detonation?
It happen just around 3000-3500 rpm where all ignition advance is in.
 
I found an old drawing I replicated from a post on the Innovate forum. It's a very basic view of how the high speed air bleed and emulsion holes work together to correct the nonlinear flow of the primary jet. If you didn't have air bleeds and eholes, your AFR would get richer as the booster flow increased. The basic principle is that the fuel in the high speed air bleed well drops as booster flow increases uncovering the emulsion holes. The upper ehole is above the fuel bowl level. This is what provides the initial air and emulsification when the main circuit starts. If you make this hole bigger, the mains start sooner and richer. If you reduce this hole, the mains start later and leaner. This is all from memory so it may not be 100% correct..


ehole1.jpg
 
Those are some great drawings showing the main circuit in total. That really helps get
the visual picture of how it works!

Any books you would recommend buying?
 
Most of the carb books don't go into the emulsion theory or tuning details. Here's another good write up describing the emulsion effect.
Warning "long read"

In general terms, a carb is nothing more than a pressure-differential fuel delivery device. With different pressure-differentials throughout as rpm and engine demand for air/fuel increases. If there were no emulsion system in the carb, as the rpm and air-fuel demand increases, the carb would run progressively richer and richer. The emulsion system, with jets, tubes and holes in both, permit tailoring of the AFR curve throughout the operating engine range. With holes or jets in the main emulsion well, as engine demand increases, the fuel level in the main well decreases. Even runs below the fuel level in the bowl. As that well level continually decreases, more 'holes' are progressively uncovered which introduces more and more air, via the air correction (bleed) jet, into the well to emulsify the fuel.

It is well documented that introducing air into the main well encourages low signal flow and can encourage or discourage high signal flow. The natural characteristic of a plain jet and nozzle (no air) is to get richer as airflow increases. The purpose of the air bleed system is to modify that behavior to accomplish a constant (or the desired) air/fuel ratio over as wide a range of airflows as possible. The particular ratios for power and cruise are realized by the selection of jet and rod or jet and auxiliary jet (power valve channel). The purpose of air bleeds is not to emulsify but to accomplish the correct fuel delivery. Emulsion is just a beneficial side effect.

What I’m going on about here is “correct two-phase flow”. That is the description of a fluid flow that is made up of a liquid and a gas flowing together in the same conduit. As the ratio of gas to liquid increases (more gas, less liquid), at some point the gas bubbles coalesce from many small ones into a few big ones and the flow starts to “slug” and become erratic. The carburetor nozzle spits like a garden hose with air in it when there is too much “emulsion” air.

An emulsion of air and fuel has reduced density, surface tension and viscosity compared to fuel alone. This increases the flow of fuel considerably, particularly in low-pressure difference operation, at low throttle openings or lower engine speeds. Just how much of an increase (richer) is dependent upon where and how much air is introduced into the fuel flow.

Mainly, what must be understood is that because the fuel discharge nozzle connects the venturi to the main well, whatever the low pressure (vacuum) is in the venturi, it is also the pressure in the main well. The air bleed is in the carb air horn or somewhere else where it is exposed to essentially atmospheric pressure, which is higher than the venturi pressure. This pressure difference causes air from the air bleed to flow through the emulsion system into the main well and to the nozzle. The flow of air can have very high velocities, approaching sonic in some orifices. The airflow literally blows the fuel toward and through the nozzle. A larger main air bleed will admit more air to the emulsion system and that can increase or decrease fuel flow to the engine. The size, number and location of the other air holes in the emulsion system, the size of the main well flow area, the size of the nozzle and the specific pressure difference at the moment are the determining factors. The ratios of air volume to fuel volume to flow area, with the air volume's expansion with the venturi velocity induced pressure reduction being the key. The bubbles expand as the pressure drop increases with airflow. Suck on an empty balloon to experience the effect.

The fuel flow through the main jet is the result of the pressure difference between the atmospheric pressure in the float bowl and the venturi air velocity induced vacuum acting on the nozzle and the main well. The venturi vacuum in the well is reduced (the pressure is raised) by the "air leak" from the air bleed. This reduces the pressure difference that causes the flow through the main jet. If the air bleed were big enough, the pressure in the well would be the same as in the float bowl and no fuel would flow. Think about drinking through a soda straw with a hole in it above liquid level. Bigger hole, less soda. Suck harder, not much more soda. Big enough hole, no soda. This is the means by which the emulsion system can "lean it out on the top end". Incidentally, the vacuum that lifts water up a soda straw is in the most sensitive operating range for emulsion systems.

It is in the lowest range of throttle opening, at the start of main system flow, that the effect of adjusting the introduced emulsion air (and its effect in increasing the main fuel flow) is most critical. Small changes can have large and sometimes unexpected or counter-intuitive consequences. The goal is to seamlessly blend the rising main flow with the declining idle/transition system fuel delivery to accomplish smooth engine operation during opening of the throttle in all conditions, whether from curb idle or any higher engine speed. The high speed and load mixture correction is usually easily accomplished, in comparison.

The vertical location of the bleeds entering the main well influences the fuel flow in the following ways.

1: Orifices above float level or between the well and the nozzle allow bled air to raise the pressure (reduce the vacuum) in the nozzle and above the fuel in the well. That delays the initial start of fuel flow from the nozzle to a higher air flow through the venturi and is used to control the point in the early throttle opening where the main starts.

2: Orifices at float level increase low range (early throttle opening) fuel flow by carrying fuel with the airflow to the nozzle.

3: Orifices below float level increase fuel flow by the effect of lowering the level of fuel in the well to the hole(s) admitting air. This is like raising the float level a similar amount (increases the effect of gravity in the pressure difference across the main jet) and also adds to the airflow carrying fuel to the nozzle. Locating the orifices at different vertical positions influences this effect’s progression.

4: The "emulsion holes" influence is greatest at low flows and the "main air bleed" has most influence at high flows.

In the first three cases above, once fuel flow is established it is greater than it would be with fewer or smaller holes. Visualize wind blowing spray off of the top of water waves. It doesn’t take much pressure difference to cause the velocity of the airflow through the bleed orifices to have significant velocity in the orifice, even approaching sonic (1100 F.P.S.) if the orifices are small. The phenomenon of critical flow is what limits the total air flow through an orifice and allows tuning by changing bleed size.

Essentially, the emulsion effect will richen the low flow and the air bleed size, main well and nozzle restrictions will control the increase or reduction of high flow. Again, the desired air/fuel ratio is the primary purpose of the bleed system. "Improved emulsion" is an oxymoron if the modification of air bleeds to "improve emulsion" results in an incorrect air/fuel ratio in some range of engine operation. Correct proportioning of all the different bleeds (and, of course, the idle, transition and power circuits) will give the correct air/fuel ratios over the total range of speeds and loads and a flat air/fuel ratio characteristic at wide open throttle.
 
mathd said:
Just to be carefull, did you see that lean out at 80% TPS on every pass. too lean near wot not good.
Click to expand...

Are you referring to the vertical spike from 3.7 to 5.3 seconds, that's 3000 to 3400 rpm.
Yeah that's not good for power either with the AFR reading about 15:1 at the peak.

Now what orifice do I jack with, where is that hat I use to draw from! :rolleyes:
 
NOTE: I made a mistake and got #80s when I thought I was getting #86, so the discussion below is invalid. 8/16/2015, 10:48 am

Today I compared a run I had with the secondaries wired shut and it went rich at the point in question with the leaning out to 15.5:1. So to counter that leaning out of the secondaries I went from #83 jets to #86 jets. This really seemed to reduce the lean spike and flatten out the AFR curve.

I'm thinking that next I will try #89s. That should really flatten out the curve and maybe start going rich at the right time.

Note: Run #1 is a sharp thin line and
run #2 is wider and blurry line.

Opinions about my next change???????

2015-08-15-1402.jpg
 
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