I just realized that I own an O2 reading setup I bought years ago to tune the mechanical fuel injection in my BMW 2002tii. It has a sensor holder that clamps to the tailpipe and a small box with readout. What values shoud I be looking for for a well tuned engine 
R Thorpe
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If you're running carbs you're looking for notes of cherry and old leather, with maybe some spice or hints of forrest floor on the finish.
I jest because I don't know the answer other than somewhere between 12.5-14.5 ish. Wait for @DannyP to chime in.
Stoichiometric with gasoline is 14.7:1. Tuning is not as easy as just aiming for that everywhere-- it helps to be rich of that (lower first number) on acceleration and leaner than that on cruise (if you can get away with it).
Heat is also a factor.
Thanks, got the tools might as well take a look. This thing is a gas hog, my 911 got better mileage, and it was a 3.2 with Webbers.
The vast majority of people have the set up pig-rich. Using the A:F gauge to tune is always a good idea.
Here's a how-to.
tl/dnr:
Best A/F ratio at idle is 13.5--14:1
WOT 12.8-13.2:1
Cruise and mid should be in those ranges; a little richer when stomping on it but not below 12, and generally in the 14:1 range when steady-state.
As stan says, you're probably super-rich. Like 10, even 9-ish, which is wrong and stupid and it won't "run cooler" like that either, despite what a plurality of "experts" claim. Just wasting gas, leaving power and throttle response on the table and probably hurting the engine a little too.
I've got the same chore high on my agenda.
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I know I'm running rich. The tail pipes get sooty, instead of that nice gray color they should be.
But, it just runs and sounds best this way.
I've tried all kinds of things to lean it out. Smaller fuel jets (idle, main, idle and main). Larger air jets. Lower settings on the 'mixture' screws (which aren't mixture screws). Lighter on the accelerator pumps.
When I do any of that, it runs like crap and starts popping, or stops responding well. So, I gradually nurse it back to where it runs well and all of the settings end up exactly where they were when I started.
It is a good way to spend a few days, though, feeling like I've just done some righteous guy stuff - the stuff you just have to drink a beer after.
If it weren't for that manly feeling of having once again wrestled the bull and won, it would probably be a complete waste of time.
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What Ed said. Washing your cylinder walls with gasoline is NOT a good thing.
I shoot for 12.5 at WOT(wide open throttle).
What does your wideband say, Mitch?
Also, how much are you reducing your spark timing to compensate for leaning out the fuel mix?
I know @DannyP will chime in here with some actual wisdom.
I don't back off the timing at all with carbs.
But I'll actually know more when it warms up again and I get some road time and tuning time.
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Ed, no wideband, no narrow band, no band of any kind.
The engine builder and Anthony had much experience with builds like mine, so their first guess at vents and jetting was pretty close. I swapped in one size larger idles, left everything else where it was, and it ran pretty well from the start. That was 30,000 miles and six years ago.
It idles, transitions, and pulls well - no dead spots. When warm, it smoothes right out. Never any popping, even when cold or when going down a long hill in gear, foot off the throttle.
Twice a year, at change of season, I'll go around the 'mixture' screws and adjust - but they never need more than half a turn. I think the best thing I did for the carbs was the Magnaspark.
I average 20-23 mpg, but that's maybe because of the 5-speed. On rural roads, I spend more time in 4th than in top gear. On the rare freeway cruise, the mileage can go up to 25-27.
Honestly, if I hooked up a wideband and it told me my numbers are wrong, I'd be reluctant to change anything.
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Everybody sings the praises of the Tomlinson Dellorto and Weber manuals. Your experience may vary, but I've found them to be borderline useless to actually tune a set of duals. They're written with all the precision of a 1979 Car Craft article (they read like a Hot VWs feature). They talk about stuff and give "rule of thumb" settings for mixture screws, air-correction jets, etc., but don't tell you much of anything specific. They have 2 or 3 nice exploded views, but I have an internet connection and can get those views pretty much anywhere, so the books were read once and set aside.
I've read more about this than most people. I think I'm the only man alive that tried to read all 10 bazillion pages of the AF thread over on theSamba. Internet opinions are like belly buttons-- everybody's got one, but some of them are just wrong.
I've had an Innovate wideband for years (purchased before I knew I could get the same thing for 1/4 the money), and have used it to set the idles and mains. I was never very comfortable knowing what to do with the air jets, so I just left them. Carbs are pretty much fancy air-leaks, and I figured I had them as good as they could get without going to EFI.
My car always ran way better than 90% of the other speedsters I've driven, and always returned me at least 25 mpg, no matter what engine I was running. Some engines ran better than others, but there's always the interplay between the actual engine, the ignition curve, and the fuel mixtures.
There are known mechanical combinations that work well (the 2110 with an W120 and 1.25s, the 2332 with an FK8 and 1.4s, etc.). Most of us have one of them, and they're great. But the thing is, no matter what engine is back there-- it can be made way better by tuning it. That's ignition and fuel.
Most of us have a distributor we drop in and set to 30* advance at 3000 RPM. Idle advance is what it is, and we live with the curve. I'm convinced this is 75% of tuning-- getting the ignition curve right, and we just live with whatever we've got for a distributor. 009s are notoriously suboptimal, but most of us don't even have that-- we're trying to do this with a Chinese 009 (or 034) copy. I ran a CB Black Box on the twin-cam motor, and was blown away how much better a stable and customizable ignition curve was. People have no idea. I figured this was about as good as it was going to get.
Then I ran with Danny's Spyder. It was a revelation.
He's got the reputation as a "carb whisperer", and he's made a lot of guy's cars run a lot better by just working with one of the 3 (mechanical, spark, fuel) systems. But I'm convinced that his crank-fire setup was at least 75% of the reason his car ran as good as it did (with carbs, not EFI). His engine pulled hard everywhere, even with worn rings (in 2018). I'm not running his car down at all (far from it), I'm just pointing out that even when the engine was getting tired and needing a rebuild-- it ran well enough that 99.99% of the people out there wouldn't have touched a thing on it.
He played with his ignition curve for years, and optimized it with 50+ different maps. When I drove it last fall, it had a fresh rebuild but still had carbs. There were no holes anywhere-- none. There was no discernable transitions from idles to mains, no hesitation off idle, no stumble on an accelerator stomp. It was as close to perfect as I've ever driven. A 2332 has more outright power, but his car spooled up and took off in a way that most bigger engines I've driven have not. The power the engine has was everywhere. Total output is not the only measure of performance, and not even the one that matters the most.
I came home resolved to go to crank-fire, and I'm deeply "in process". The current plan is to eventually get to EFI, but to set up a Microsquirt system with ignition only to start, then go to injection once I'm completely comfortable with TunerStudio. Baby steps. The Black Box was a gateway drug, but it relies on a distributor pickup. I'm excited to dive into the world of dead accurate and dead stable crank position ignition pulses.
I really do think that we're all starting in the wrong place when we try to tune. Fuel really can't be set up optimally unless spark is worlds better than most people settle for with a fake 009. I'd encourage everybody to get a Black Box at a minimum.
Anyhow, I reread the John Connelly article Ed linked and it helped me get excited about playing with my carbs again once I'm up and rolling with 50% of the Microsquirt (the ignition).
John is a smart guy, and provides way more information than Tomlinson ever did with "the books", but he's not a writer either. It's going to take a season or two to optimize the carbs even with a better ignition. I've got every jet I could possibly need, and have the O2 sensor to get it done.
I don't even think I'm going to put the new engine in the Speedster this year. For once, I think I'm going to stand pat and stick with 'ol trusty (the 2110), and use it for the test-bed for the Microsquirt/crank-fire thing. I can dial in the carbs using John's article as a guide, and see how well I can make this run (and how comfortable I can get with the software) before I introduce a whole different set of variables with an engine needing a proper break-in, etc. The EFI part of the program will be last, and is probably several years away.
Anyway, read the article Ed linked. There's a huge amount of information-- and I can guarantee that if you use half of it, your car will run better than it ever has.
Stan, once again, thanks. I don't do anything special to my carbs. The floats are dead on. The fuel pressure is exactly 3.5 psi. The linkage is also dead on, zero play. After that it's just 4 screws, set to what each cylinder needs, not some arbitrary number.
I would say that the crankfire ignition is the single best thing you can do for these old 4 cylinder lawnmower engines. It makes it start quicker, idle better and smoother. It takes out that crappy, unreliable, and INACCURATE distributor.
Stan writes with an eloquence I'll never have. This post of his should be a sticky somewhere as a must-read to anyone having "carb problems".
I've also read through that Samba thread on AFR, and it certainly took a while. But it took me to an understanding of the why and how. In short, the light came on. John Connelly supplied me with a couple 35PDSIT Solexes(with electric chokes) for a sandrail customer about 8 years ago. I also changed the distributor to an electronic SVDA and ran vacuum line to BOTH carbs. Stacked up a bunch of gaskets under a stock mechanical pump to get 1.5 psi.
I got them installed and running decent but wasn't impressed. It needed other than stock jets. I told him the engine size and exhaust and altitude the rail runs. Dead on jet sizes came in the mail. The man knows things. This rail runs pretty much like any electric-choke-equipped Big-Three single-carbed V8 back in the 70s: 2 pumps and hit the starter. It runs, warms up and idles down. It doesn't bog, spit, sputter or anything else untoward. Eight years later they haven't been touched. Still runs GREAT.
The point of that last is John from aircooled.net has more stuff in his head than a lot of people. He should be listened to when he speaks.
What is a crank fire ignition and where do I get it?
sounds like I need it. My 2110 has the stumble
This is CB Performance's version. There are others.
https://www.cbperformance.com/product-p/2094.htm
An alternative might be the system from 123ignition, but for similar money I would go with a true, crank-fire set-up. Using the 123ignition distributor just can't be as precisely accurate as a 6+" toothed degree wheel.
John's knowledge and willingness to share it is one reason aircooled.net is usually the first place I go to buy stuff, even if the price is a little higher sometimes.
Also, I tend to be less concerned about quality with stuff from there.
@Phisaac posted:Seems pretty complicated. Thank you
Paul ISAAC
Paul: it is!
What you're doing with the CB or other crank-fire kit is grafting on the modern ignition every road car has had for the last 30 years to an engine that wasn't made for that sort of thing—and programming in the spark advance curve your particular engine likes best.
Nothing quick or easy about it.
But it absolutely works and, once done, will likely never need to be touched again. No cap/rotor changes, no points, no condenser and (most likely) no problem ever with the "module" like some people report with the in-distributor Pertronix.
I'm one who believes most of the trouble with the 009 disty can be solved with a good aftermarket unit like the MagnaSpark. Crankfire probably is overkill for most hobby car people. But what Stan says is very true: Danny's car is very, very well set up and that kind of smooth violence is hard to let go of once you've experienced it.
Back O2 ratios, I also agree that John at air-cooled has more real experience with VW engines than almost anyone. I used his guidelines when setting up my air fuel ratio targets and have changed them over time. Here's the thing, every engine is a little bit different in what it wants to run best. Change the compression ratio, running temperature, head/port flow, force induction and the engine will want different. fueling to be in the sweet spot (and/or safe spot).
The BEST way to find it for your engine setup is to get close and then go to a dyno and change fueling while tracking changes to torque/hp. Of course, you'll be listening at all times for engine knock. I've done this many times with my supercharged and turbo engines, but have just depended on my butt-dyno on the 1776 in the speedster .
I've moved a lot leaner than John's guidelines over the last year. I'm running 9:1 compression on Panchitto heads and high test gas in ambient temperatures that range from 70F to 90F. Here's the target air-fuel ratio table that I'm currently using. I don't get any knock with this and the engine definitely likes it better than a richer setup. This is certainly not to knock John, but to give folks a sense of the range of setups that might run best. Always start with a richer setup and move leaner to keep from detonating your pistons or burning your valves, But you guys know that.
Thanks, Mike. That's really useful.
Thanks all...
I have the CB Performance Magna Spark distributor. Think the black box although great is a tab over my head for now. Will grow into it.
Yeah, Mike, since I'm tuning my EFI right now, that REALLY helps. AFR targets are important and you're right, every motor likes something different.
Timing at idle means ABSOLUTELY NOTHING. It's max advance that's important, and should not exceed 32 degrees under full load(usually).
30 degrees is a good compromise of power versus safety. If you have a vacuum pot on the distributor, disconnect and plug the line/hose.
as always thanks I will give it ago. That aside except for the stumble under hard acceleration it runs great.
I don't know if my commentary is needed here or not but as I was reading through all of this, especially Stan's comments; all I could personally think of was me driving Danny's car for myself. We have, from a 30,000 foot view, the same car. However, there is a glaring difference between his car and mine and the work he has put into and the knowledge he has on these engines shows pretty clearly when you drive his.
I have spent enough time with Stan both following his car in my modern Porsche and with speaking with him to know he also knows what he is doing and for him to compliment Danny's car as he did above, again, speaks volumes.
I am not saying anyone's opinions here are invalid nor am I saying that others here don't have equally valuable opinions. I am just saying that of those I have met personally and those whose cars I have seen in person, when Danny or Stan offer their opinion, I listen carefully.
@Sacto Mitch posted:.
I know I'm running rich. The tail pipes get sooty, instead of that nice gray color they should be.
But, it just runs and sounds best this way.
I've tried all kinds of things to lean it out. Smaller fuel jets (idle, main, idle and main). Larger air jets. Lower settings on the 'mixture' screws (which aren't mixture screws). Lighter on the accelerator pumps.
When I do any of that, it runs like crap and starts popping, or stops responding well. So, I gradually nurse it back to where it runs well and all of the settings end up exactly where they were when I started.
It is a good way to spend a few days, though, feeling like I've just done some righteous guy stuff - the stuff you just have to drink a beer after.
If it weren't for that manly feeling of having once again wrestled the bull and won, it would probably be a complete waste of time.
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Mitch, what carbs: Spanish, Italian, or Chinese? 40 or 44 IDF? Pretty sure you have medium build 2110, correct?
What is you fuel pressure, float height, and emulsion tube(F11?). What are your mains, idles, and air correctors? What is your usual altitude? Curious to know.
I DO AS WELL. I always tell my clients the only dump question is the one that is not asked.
SO, here goes.......
concerning the advance. 30-32 degrees advance. is that also BTC?
There are no dumb questions.
@Phisaac
Yes, Phil, that’s 30° - 32° Total advance before top dead center, set at a steady 3,000 rpm.
Set the total advance, then go back and see what you have for advance at idle. Ideally, it'll be pretty close to what you had before, but the amount of advance (and when it comes in) is pretty spotty from distributor to distributor.
When you check your timing, do it at night or in a dark garage so you can really see what's going on. If the light seems to be misfiring sometimes, and the timing doesn't seem very steady on the 30* mark-- it's probably not your light. That's called "spark scatter" and I never saw it on any vehicle before I got hooked on ACVWs. That's not OK-- that's why these cars often run hot, "ping", and have flat spots. The spark timing is all over the map. It's worse when the advance starts-- if you watch your timing light from idle up to 3000 RPM, most times it's going to be unreadable along the way.
If you can read it at all, your distributor is better than most. If it's rock steady-- hold onto it and never let it go. Ever. OG German Bosch 010s (and the like) are reputed to be that steady, and they sell for $300+ each used over on theSamba. I can tell you from experience that no Brazilian or Mexican Bosch distributor will do that. East Asian copies? Please.
Couple the flakiness of the most widely used distributors with the fact that the points replacement modules most of us have been using for years are "less reliable" than we'd like to think they are (to put it kindly), and you have a messy, weak, scattered ignition system. Having something steady, strong, and reliable is worth the effort and expense. Everybody wants to spend the money for shiny new carbs, but the mysterious electrons under the red cap are presumed to be doing their magical 'lectrical thing. Out of sight is out of mind.
Distributors are lousy, points replacement modules are lousy, and coils are pretty lousy as well. All in all, it's the system time forgot. Motors got really big and really powerful. Carbs are the miracle of the mechanical age, and they are way, way more reliable than people think-- but somehow they always take the rap.
It's almost always spark. Even when it really, really seems like fuel it's spark. Even when you've driven (or trailered) you car through a biblical thunderstorm, and you're sure (SURE, I tell you) that you've got water in your float bowls or in your idle circuit-- it's spark. When you're a newbie, it's spark. When you're way too experienced to get sucked in, it's spark.
A car with a plugged idle jet won't idle well, but it'll clear out when it comes on the mains. Drive it hard enough, and you might not even realize it. A misfiring engine stumbles and bucks and farts and backfires. 95% of fuel problems are spark.
That's why I was droning on and on about crank-fire. Not because it's easy, or because everybody does it-- but because it's the final solution, the end of all the spark nonsense we all endure all the time. A Black Box gets you 50% of the way there, but it's not really the right 50%. Some alternative crank-based pickup (I've been looking at the Moroso flying magnet system for V8s) would be much, much better.
Good luck. Forewarned is forearmed.
What Stan said. Again, eloquence. I don't has it. But I agree 150%, crank-fired since 2008.
It is the way of today, and the way of the future as long as the ICE exists.
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Stan (and Danny), here's that video I posted the other day of my Vintage Speed exhaust. This was recorded a few years ago, when I still had the Pertronix.
Jump to the last 10 seconds (at about :50) where I'm trying to hold a steady speed at about 2800 rpm. It sounds sort of OK, but if you listen carefully, you can hear the miss. How many of us pull our hair out trying to get rid of that with jetting? That went away with the MagnaSpark.
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@DannyP posted:.Mitch, what carbs: Spanish, Italian, or Chinese? 40 or 44 IDF? Pretty sure you have medium build 2110, correct?
What is you fuel pressure, float height, and emulsion tube(F11?). What are your mains, idles, and air correctors? What is your usual altitude? Curious to know.
Danny, it’s a mild 2024cc (at least, that’s what my math tells me). Crank is a counterbalanced 78.8, with thick-walled 90.5 Mahle jugs. Engle 120 cam, 1:1 rockers. I think the heads are SCAT with single springs. CR is about 8.5.
Spanish 40 IDF Webers, 57 idle, 135 main, 180 airs. Magnaspark II with blue Bosch coil. Vintage Speed (1.5”) exhaust.
In the beginning, I tried going down to 55 idles, and it didn’t like that at all. And I think I tried 130 mains, too, but it started popping a lot. Now it only pops if one of the ‘mixture’ screws is too far in, and usually a quarter turn out will fix that.
Fuel pressure (mechanical pump, no shims, no regulator) is 3.0 psi, and floats were set by Anthony, so I know they’re right. Never any sign of starvation. After five years, there were signs (and smells) of leaking needle valves, but the seals turned out to be worn and were replaced.
Like I said, I really want to leave this alone as it runs well in all conditions. The exhaust doesn’t smell super rich - more like most cars from the fifties with no smog controls. It’s just that the inside of the pipes look sooty. Max advance is at 30 degrees. I started with the stock springs on the Magnaspark, but you can get more advance earlier on by swapping one of the springs, and doing that seemed to help response off idle.
I’m at 300 ft ASL, and do most of my driving below 2000 ft. It doesn’t seem to start losing power until about 5000 ft.
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As I understand it, the stuff that made the inside of our exhaust pipes that nice, gray, leaden color was, in fact, the lead in the gasoline we were buying back then. The same thing occurred on my Dad’s school buses - exhaust pipes that had been gray once turned sooty black after the refineries went to non-leaded gas delivered to Massachusetts starting around 1980.
Honestly Mitch if you're running smooth with good transitions and snappy throttle response and you get 26 mpg on the highway you're probably pretty close to right.
