Shift gears: your tuning notes/diary

[Jim Ratto]

Thought it might be fun to share notes from the road. I keep a small black notebook in my driver's door pocket, filled with all kinds of gibberish and tuning notes. Lately I have been re-tuning after workng out a carb-heating/heat soak issue.

Anybody else keep a log of change made to tuning?

[lawrence]

Yes. Jets in use, timing settings, plug gaps, mileage when stuff was done, amount of turns, etc.

[Jim Ratto]

New Year's Day I went thru half a tank of 91 trying to remind myself of how badly F11 tubes run in my car. Despite my stubborn stupidity I ran the car around and wasted 2 hours, noting what I had known from years before, they never run well. No matter main jet I ran, transition and tip in are very very lean. Even drowning the engine with 70F10/110 idle air and 170 main, it would still buck under load.
I'm right back with my good old stand by F4 tubes and what has made sense, despite what AFR sensor tells me and the 3 pages of notes from Wednesday.

[lawrence]

That's weird. I think my engine has always run best with F11s. It usually bordering on rich down low even with 55f10 fuel/109 air and 135 main/178 air. I'm pretty sure it would run even richer with F7s because those enrich the transition circuit and low rpm.

[Arry]

Don't want to turn this into an emulsion tubes topic but Jim, how you think the F4s compare to F2 tubes?
I'm running F2s with 37 vents in my 48s, so far I like them way better than the F7s they originally came with.

[axam48ida]

help me here understand the emulsion tubes, I thought the F2 were more for alcohol bend fuels, I have ran the F11 and F7 both with good results.
The F20's I read about on another post, what is there range?

[Jim Ratto]

F2 and F4 are both 7.5mm but belong to different families. Both are for high fuel demand. F4 has air holes farther down. but air holes at top and fuel holes at bottom are same as F2. My car responds to throttle @ 2500 much crisper with F4 than with F2. The F11 are 8.0mm and flow less fuel to aux venturi nozzle. No matter how big of a main I inserted, I think the fatter diameter of the F11 was choking off fuel to nozzles. There are other tubes I would like to try but I don't have the $/time/patience right now to do all this again right now. I know Oelkers car ran much better on the F2's over the F7's we took out of it. With the ethanol in our pump gas in CA it's no wonder these F2 or F4 tubes repsond well. The F2 runs richer the higher I wind it, even with 205 airs.
there is no correlation to F number and how the tube works. And one tube might run rich in a 1500 rpm segment then lean in the next, whereas a sister tube will do the exact opposite. Weber groups the tubes into "families"
Interesting that the F4 was used in the 1600cc Porsche 692 Carrera 'GT' which ran big 38mm chokes and 3.00 needle valves. Obviously a need for sensitive metering and fuel demand there. Carbs were 40DCM2 Webers. Talked to a guy this week that is running a pair of these Webers and collaborated the theory on F4.
The F7 is going to run rich (depending on jets used) on transition. It has no air holes until "3rd row" down, requiring pretty healthy vacuum in venturies to being emulsifying or atomizing fuel on its way to the nozzles and motor. An F16 is kind of the same except it's fatter, @ 8.2mm. The 904 Carrera tube, the F14 is a weird one. Diam is 8.2mm but has no holes after 1st top row.
I think it's important to "build" an idle jet stack that will take you to 2800-3200 rpm and still not cloud over @ idle. I test this by taking the car down the street with NO main stacks in carbs and watch to see what rpm the idles stop fueling motor. I judge how far out mixture screw needs to be too. Once I know what works on idle then I go to main jet and tubes.

[Arry]

Interesting, thanks for the good info Jim.

[axam48ida]

thanks Jim, your always there with the breakdown.
 on another forum topic (improving your IDA's) they refer to a "F20"
are they talking about the F2? or is there a F20?

[javabug]

I don't keep super-detailed notes, although I know I should. You're exactly right about going round trying to re-convince yourself that something that didn't work before might work this time. I've been doing it for the last two years trying to nail the tune on my car.

[JS]

thanks Jim, your always there with the breakdown.
 on another forum topic (improving your IDA's) they refer to a "F20"
are they talking about the F2? or is there a F20?

There is a F20. I´m no expert on emulsion tubes, so I really don´t know how F20´s compare to the more commonly used F2,7,11 etc.

[Jim Ratto]

The F20 was the tube used in 356 Carrera 2 (2 liter) when it was ordered with 46IDM Webers and the Sport II exhaust. Used with 165 or 175 main, 40mm choke and 240 air corrector. It's in the same "family" as the F4 actually. Same diam and hole orientation except it is missing the lowest row of air holes when compared to F4. Another high rpm, high fuel demand tube.

[Jim Ratto]

the Pat Braden book gives a good explanation of how emulsion tubes work but it's hard to find specific answers as to how specific tubes work until you try them or talk to people that have used them and made them work. There's a good short vid on youtube by David Vizard too. The official Weber Tuning Guide has a chart and drawings of every 61450 series tube known, with OD, ID, hole location, hole count and hole dimension. You can go blind working thru it. I picked the tubes I have and have run and plotted them in Excel so I can refer to them easier.

[DKK Ted]

Jim, how is the F-8 compared to the F-4, I remember Andy at Bergs, when I worked there, used the F-8's in the Berg carbs.

[DKK Ted]

Oh! I do keep a small book in my car with jets I run with dates I make changes.

Ted

[Jim Ratto]

Jim, how is the F-8 compared to the F-4, I remember Andy at Bergs, when I worked there, used the F-8's in the Berg carbs.

Hi Ted
The F8 isn't grouped into same family as F4 by Weber. I don't have any F8 tubes but from memory they are like an F7 (lack of holes near top of tube for low RPM) but with additional holes towards the lower portion of the tube. I don't know the diam of the F8. I'll have to look it up later in Weber's chart.

[wph]

This may have some helpful info:

http://www.webercarburatori.com/?p=handbook&s=2

[Jim Ratto]

This may have some helpful info:

http://www.webercarburatori.com/?p=handbook&s=2

yep good link. The F8 is same diameter as F7 but has 2x 1.00mm "top row" air holes, whereas the F7 has none.

[mg]

Anybody else keep a log of change made to tuning?

Need one per car per track.

[Jim Ratto]

recent entries from my book
"1/1/2014 11:30am 65idle, 120 holder, 165m, F2, 200air 3/4 turn rich in transition when cold. Hunting 118 west Stearns to Madera Less rich 118E Collins-Madera"
"11:55am 65 idle, 120 holder, 165m, F11, 200air, 3/4-1turn, off idle good and clean. W 118 Madera Princeton no hunting. E118 Princeton-Madera very lean @ tip in, 12.5+ @ cruise, lean. Will go 3200 with 65 idle and no main"
"12:30pm 65 idle 120 holder, 170m, F11, 200 air, 3/4-1turn, off idle ok still, no hunting W118 Madera Princeton. E118 still too lean, tip in no change AFR"
"12:45pm 65 idle, 110 holder 170m, F11, 200 air, 3/4 turn out, idle dirty, no hunting W118 Madera Princeton. E118 still lean Princeton to Madera. Lean grade Tierra Rejada west. Hot"
"1:10pm 70 idle 110 holder, 165m, 200 air, 3/4 turn, hard to clean idle, hunts W118 Madera Princeton, E118 still lean back to Madera. Still lean grade Tierra W"
"End 1/1/2014"
I went home and went over notes and spent time thinking what next logical stack should comprise.
After a few more 118 and Tierra passes- I went back to the F4 tube and the lean hole vanished. Initially I went back to 110 holder but it brought on the rich hunting (esp when cold- sounded like a full drag car idling through pits). Went 60 idle with 110 holder, now it left slight gap @ top of transition and lost its "hard idle." Went 650 x 120 holder and wham, nice hard edged idle, no hunting (with F4). Still pulled to 3200 w/o main stacks.
"1/2/2014, 8:20pm 65idle, 120 holder 150 m, F4, 180air, no hunting W118 Madera-Princeton, full power on 3000+ E118 12.88 @ 6000"
Final jetting ended up same with 155main and 180 air in F4's

[DKK Ted]

This may have some helpful info:

http://www.webercarburatori.com/?p=handbook&s=2

yep good link. The F8 is same diameter as F7 but has 2x 1.00mm "top row" air holes, whereas the F7 has none.

So with the air holes in it, what does that mean?

[Jim Ratto]

This may have some helpful info:

http://www.webercarburatori.com/?p=handbook&s=2

yep good link. The F8 is same diameter as F7 but has 2x 1.00mm "top row" air holes, whereas the F7 has none.

So with the air holes in it, what does that mean?

The holes in the higher region of the tube allow air to mix with fuel at low to mid RPM. The more holes or the bigger the holes the more air admitted to mix.

[Cheesepanzer]

Started keeping logs a number of years back when I couldn't remember $hit during builds that took a year or two to fully complete.  The logs helped me keep track of various specs, torque settings, geometry, end play, plug types and gaps, timing details, and of course jetting.  I then supplemented those entries later with results at the track or a dyno session.  Definitely helps with my "recall" and helped with later builds.  Each build has a separate notebook.

[JezWest]

When I inherited my bug from my grandfather, I inherited 'all' servicing details (and the original bill of sale, handbook etc). Seeing as it was already there, I just carried on. Everything goes in there, so if the car starts running like a tractor I can go back and see what I did to mess it up. I keep a stack of paper in the garage to make measurements, record changes and every now and them transcribe then to a file on the computer. Stuff like which valves felt tight, repairs to oil cooler cover seals, idle mix screw adjustments. There's also a shopping list for stuff I need (which now reads headlight tubes, front wings, stainless M12 wing nuts, stainless this, stainless that, stainless the other...). Saved me so many times.

Bit geeky maybe - I call it scientific 

[Arry]

Went 650 x 120 holder and wham, nice hard edged idle, no hunting (with F4). Still pulled to 3200 w/o main stacks.

"1/2/2014, 8:20pm 65idle, 120 holder 150 m, F4, 180air, no hunting W118 Madera-Princeton, full power on 3000+ E118 12.88 @ 6000"
Final jetting ended up same with 155main and 180 air in F4's

Very interesting; Jim, are you still running your 48s with the stock 2 prog holes?
I remember you advising to use a smaller (110) idle air to improve overall driveability; do you think going larger on the idle jets (with the stock 120 idle airs) and the F4 tubes makes using a smaller air jet unnecessary?

[Ben67]

Ok Jim. Your tune is with the stock 2 progression holes. What about those with a 3rd hole.  I recently tuned a bit on  a car with the 3rd hole mod. How does this affect changing idle holder size?  I think I kinda  figured it out but I'd like to hear from others. 

[Jim Ratto]

Still just 2 progression holes.
We in CA get to deal with 2 different fuel blends, depending on the season. In 2011 I struggled with a sudden change in the way my car was running off idle, but I had changed nothing. This was as the fuel prices soared at the pump, and us consumers were told by the media "oh the price increases are due to the switchover to 'summer blend'". That season it took 60 x 120 to get idle cleaned up. Since then the car has more compression and different cam timing, altering it's mixture of choice. Used to have locked advance curve too.
The idle circuit on a 48 IDA Weber isn't "just for idling" this circuit only "idles" when plates are in closed or almost closed position and mixture emits from small holes adjacent to throttle plates. As you open throttles, the idle circuit is still responsible, emitting fuel not only from hole on underside of carb, but from progression holes as well. Once signal to aux venturies is strong enough, mixture will begin from main circuits too. The idle circuit should be able to take engine (under load) up to around 2800-3200 rpm, so it's important to build an idle stack that will do that. By using the smaller air hole in the idle jet holder, you runner a richer "idle" fuel curve at top end of this rpm region. Or you can run a bigger fuel jet, but you may end up with too rich idle (actual idle). I run irdium plugs to help keep idle "clean" with 65 fuel jets

[Jim Ratto]

Ok Jim. Your tune is with the stock 2 progression holes. What about those with a 3rd hole.  I recently tuned a bit on  a car with the 3rd hole mod. How does this affect changing idle holder size?  I think I kinda  figured it out but I'd like to hear from others. 

Hi Ben  I have only played with one VW which had 3-hole 48's and I couldn't make it run correctly. This was in the late 1990's. We didn't try different emulsion tubes (or idle jet holders). This motor was dyno'd @ 218hp and had a huge sag in the transition but would scurry up to 8200 without fail once you drove through it. It had 70F10 idles and 120 holders that were drilled to 135. Not sure what would have worked. The owner of the car felt he was stuck with the flat spot and said "just leave it as they dyno'd it". My opinion now is that the jet holders didn't need to be 135. I'm sure with smaller air holes and maybe different e-tube it could have been better. The motor had an exhaust valve for lunch one day on the 880 freeway in Fremont and to this day it's in boxes still @ Ray Schubert's shop.
So I don't know. 

[Jason Foster]

So that would make sense then why my F11's work with my 3rd progression holes right? I don't experience the leaning out you have been with them because of the added fuel coming from the third holes.

[Jim Ratto]

So that would make sense then why my F11's work with my 3rd progression holes right? I don't experience the leaning out you have been with them because of the added fuel coming from the third holes.

I don't think the emulsion tube has any influence on the progression holes, directly. The fuel through the tubes goes through aux vent nozzles. The progression ports get fuel from idle jet.

Now the way the tube brings the main in I'm sure works differently between 2 hole and 3 hole. My car was displaying lean under load with throttles pretty far open, so I don't think progression holes (2,3 etc) would have mattered. It was the main circuit well running lean. Your motor is larger cc than mine, so it has stronger signal I'm sure. At lower rpm, your motor will pull on main harder than mine.
Rayburn's car is probably the smoothest "off idle" 48 IDA car I have been around. With 2 progression holes. It's all in how he sets up his idle stack. I listen to his car and it's hard to believe it has 275' @ .050 in it
Oelkers car too- 2 holes, 285' @ .050" . We spent a day making it happy, and it was as docile as can be. Step on it though and it would rip your brain out.
We ran F2 in his