Wideband Results

[KTPhil]

[stan_tichomirov]

Ok, here is an interesting observation, maybe you guys can clear this up for me.

2276, 40x35.5 heads with lightly cleaned up ports, 9.3:1 CR, .050" DH, Web 109 with 1.1:1 rockers, 1 1/2" BP merged header with hideaway, sea level. I've been tuning this with Spanish 40IDFs and have been having an issue with lean readings at WOT -- it'll stay in high 13 / low 14 range at WOT. Last jetting tried was 30mm vents with 52/145/200 on F7 tubes -- ran fine, with idles being on the rich side, but no hiccups.

I got a set of crusty Italian 44IDFs off eBay, cleaned them up and set them up with same manifolds as before. Used 55 idles and same emulsion tubes from the 40s -- F7s, 145/200, 36mm vents. Car feels smoother overall with more power (obviously), but weird thing is, the WOT is now reading in low 11s and sometimes I'll see 10s -- totally normal and makes me happy, but why did the same mains/airs act leaner with smaller throats/vents?

Another issue is my idle is high, like around 2K. Throttle plates are covering all the transition holes (I checked), I have to check the bypass screwes but pretty sure I saw their tips sticking out of the barrels. Any way to get the idle lower? Timing at idle is at 9 BTDC. Mixture screws are 1 1/4 turn out for now, idle AFR is around 13.

I drove it around for half an hour and it felt nice, but clogged an idle jet (I was expecting that -- insides of carbs were really cruddy and corroded, it'll take time for them to clear up). This engine definitely likes 44s better though.

Stan
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Aircooled.net
Jansen Enterprise
My 1835cc build
My budget 2276 build

[gereonb]

Probably answering my own question here, but it is possible to put an O2 sensor on a standard Type1 Beetle Muffler/Exhaust ?.
I am guessing a bung would have to realistically go in each of the removable tailpipes in which case the answer would be a NO ?,
obviously the removable type clip with sensor that gets pushed into the pipe is also out of the question due to the diameter of those tailpipes.

[ps2375]

[stan_tichomirov]

I went through them again tonight, 1/2 side had bypass screws backed out 2 turns. I'll start it tomorrow and see how it goes.

Stan
_________________
Aircooled.net
Jansen Enterprise
My 1835cc build
My budget 2276 build

[modok]

[tzepesh]

Thank you for your advice John and Roachdub. I made it run on 52s as I needed the car during the weekend. The throttle plates were opened too far .
I am reseting the LBI after each jet change.
I will do the whole tuning procedure all over again on road during the weekend if the weather is good. I want to start clean and not base my assumptions on what I did before, and draw conclusions after each small step.
What ignition map shall I start with? I just plugged in the 009 timing map to get the car running, but it is obviously not the best (slow increase in advance with RPM and no load - MAP or TPS - dependant change). As I know, increasing the load at the same RPM implies reducing the advance. But how about the AFR? Leaner mixtures need less advance and richer need more?
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'74 1303S, L98B Viperngrun (extra glitter), German Look
'64 1200, Sea Blue, under restoration

[TinCanFab]

[stan_tichomirov]

[tzepesh]

Is there any technique to measure the idle jet size without jet gauges? I can only find gauges in 0.05mm steps, and for Dellorto I would need something like 0.47 or 0.49. I'm thinking about using a microscope with digital camera, these usually have a SW that can be used to measure things in pictures if the scale or magnifying ratio is known. But I do not have any available.

Regarding the ignition map, I was asking from what type of distributor shall I take the initial timing map (mechanical and vacuum), not the real map (I can find these in different topics). But now I'm thinking that the Bosch diagrams show ported vacuum not manifold vacuum, so they are really no use. I will just drive with a laptop near me and see the bins where the timing is staying in various driving conditions.

Leaner mixtures burn faster so the advance would need to be retarded, and richer mixtures burn slower so they would need more advance, right?
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'74 1303S, L98B Viperngrun (extra glitter), German Look
'64 1200, Sea Blue, under restoration

[tzepesh]

I was just thinking of another method to check the jets: I can use a fuel pump with all jets in parallel (something like a commonrail) and measure how much gas is flowing through them during a defined period of time. I can do this with 4 identical jets or I can put different sizes of jets in parallel, such that the test would be in identical conditions for all.

Would misfire in carb be due to too much advance (but I doubt it because the map is from a 009 so advance is small, wideband shows rich, and it doesn't backfire with smaller jets where wideband shows lean).
_________________
'74 1303S, L98B Viperngrun (extra glitter), German Look
'64 1200, Sea Blue, under restoration

[the2ndcashboy]

The most common way to check jets without a jet gauge is to use the shanks of a series of really small drill bits. You might not be able to get the exact size but you can usually get close enough to figure out what you've got.
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[modok]

How to measure a hole; post apocalypse methods

Find a range of things similar to the size of the hole. They can be sewing needles, drill bits, bicycle spokes, hypodermic needles, and whatever you can find. SORT them by size and stick into a piece of foam to stay organized. If you need a thing IN BETWEEN two sizes, take a bigger thingy and polish it smaller. The dremel 3-jaw chuck is very handy for this. Chinese cheap drill sets are a good source of raw material, but often are not the sizes claimed.

Also, you can take a longish thingy and polish it to a taper, and then see how far the jet goes onto it, and measure that spot.

[T Hollis]

http://www.ebay.com/itm/21-PC-Mini-Drill-Set-Small...XQrhdTTtud

This is a very cheap (cost) and reliable set.

[tzepesh]

I'll just follow the normal tuning procedure step by step and see what I end up with. Maybe I'll make those #50 work. I'll post when I get the final results in a week or two depending on weather.

The holes I'm trying to measure are 0.45mm, 0.47mm and 0.49mm, and I need to measure them extremely accurately which seems almost impossible. The tool set Hollis linked is for larger holes, from 60 up. I do not see any possibility to use a combination of wires or something else, the holes are too small. I don't see many things that small to get alone in those holes, talk about two? I like post-apocalyptic methods, but just for the fun of thinking, they usually do not apply to such high precision or at least not in my case.

Maybe just for fun I will try the flow measurement with fuel pump, at least I can get an idea if the 52 flow the most, 50s less and 48 the least, an then see if there are any differences between the 50s (if they are balanced).

I have to buy a small bench lathe, it's only about 500 bucks and I keep fining every week that I could use it for something. I could have used one to mill 0.5 or 1mm drills to the needed dimensions, to use them for measurement. I have all kinds of micrometers and precision measurement tools, but I don't have the possibility to machine things...

Thank you all for your support and advice, I'm confident I can fine tune it and I'm willing to be pacient and follow the whole procedure from start to finish.
_________________
'74 1303S, L98B Viperngrun (extra glitter), German Look
'64 1200, Sea Blue, under restoration

[modok]

If I designed a carburetor, I would not use jets smaller than 0.5mm, because yes they are impossible to drill, hard to measure, and plug too easily.

Another possibility is to just use a good standard size idle jet that is a little too big, and enlarge the air bleed until it is right.

I'd like to think I thought of that, um, but actually so did everybody else too, and many are made that way.

[RHough]

[RHough]

Tried No Air Correctors (300's?) - Thinking that larger AC would start main circuit earlier - still lean 18+ on transition
Tried No Air Correctors and 165 main - Thinking that if it is late mains circuit the combo of huge main and huge AC would make transition too rich ...

Nope
_________________
92x74-1967cc; 9:1; L5 Heads; W-120; 1 1/2" CSP Python; Weber IDF 40

[[email protected]]

Try to block one of the bleed holes with MIG wire. Don't block both, just one for now. Re-test. This will bring mains in sooner. You'll have to re-experiment with air jet sizing.
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[RHough]