Weber DCOE tuning - Main and Acceleration circuits
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- Опубліковано 30 вер 2024
- This is final video on the Weber DCOE tuning where we tune the acceleration and main circuits. There are several video's on my channel that address all the DCOE tuning, assembly and operation in great depth. Look for playlist Weber DCOE Tuning
This is a very good video. Well elaborated very clear. You need not to change a thing. Al you need is to theach us more. I appreciate old cars more nowadays and i know that is where my heart belongs. Taking baby steps in this and am really loving having content like this to look up to. Thank you so much Steve. Am from Kenya 🇰🇪
Thanks
Hi steve, even if I already know 80% of your explainations they are incredibly interresting, I've never seen such a good video about that on youtube. You have true teaching skills, congratulations! 👍👍.
Thank you, happy that I could help
Great video Steve. For younger people carbs seem incredibly complicated (eg my 20 year old son) but there are lots of really good books and nowadays good UA-cam content to explain, which yours is excellent. My son is much more happy with ECUs and a laptop on his race car. I’m confident on both but the mechanical principles of a carb is more attractive to me .
indeed, I see that all the time . However the principles remain the same in terms of combustian. I am an electronics design engineer by profession and do handle ECU's , mainly Delphi .. acting on fuel maps , based on inputs from the MAF,MAP and so many other sensors and controls. Yet , I prefer the classical old carbs. A matter of taste
I see why "only" 6000 rpm
This is good stuff, i've got twin 40's on my kitcar and it seems like nobody knows how to set these up anymore, I ended up spending huge amount of money on "professionals" to fix a problem with bogging down on acceleration when warm, nobody fixed it.
In the end I stripped the carbs down myself to rebuild them and found LOTs of really bad stuff that had been done by these "professionals", like shortening and welding the accelerator pumps in such a way that they didn't fully close anymore, parts missing (3 of the the pump circuit bearings), the wrong float valves fitted (so it leaked fuel at idle), they'd damaged one of the idle screws, seals and washers missing, etc etc. They even broke part of my wiring loom somehow.
In the end the problem was a perforated Misab plate and there had been no need to mess with the carbs at all.
It's hard to know who to trust with this sort of work.
Your breakdown of the circuits and progression are well explained. Thank you for his series of weber videos.
TXS
Too much guess work for me. Buy a AFR gauge if you want to do it that way.
Thanks, it's not just guess work... its trial and error... however if one knows the basic rules you can come very close, Of course an AFR gauge will help ( did that as well in other video's) but only if you can log the readings,,, But even then you will need to understand the weber and select the right jets.tubes to get closer to where you want the AFR to be,,,,,
Otro video excelente! Si bien es cierto que se puede usar una herramienta de gran ayuda para estos casos ( sonda wideband ), creo q es importantisimo primero entender los conceptos basicos de este arte que es la carburación.
Thnak you
Proper plug heat range and colour too. Rolling road sure is nice tho. Not even available near me, sadly. Back in the 70's I used to tune carbs in my bare feet, driving. Flat spots seemed more pronounced on the ball of your foot.
As I can see your Dcoe is far from 5⁰ as Weber recommend to be. You set the chamber level to 26mm with the caliper or there is another method?
Its about 6-7 which is not ideal ... I know... I might have to make some shims on the intake manifold... for the caliper yoiu can use a bit .txs for the comments
advance curve in distributor
Steve, I have modified my BMW 2002 with aggressive porting (E21) and a 292 cam. This is in contrast to the stock 264 (I think) cam and regular uncut head. The twin 40 DCOEs were originally set for stock engine and it ran well once warmed up, except always a low end flat spot that forced me to learn to heel-toe when I was a kid. How do I know what hardware to have in my tackle box? I am of a mind to change single variables at a time to observe the outcome. Adding more complexity (or maybe simplicity) is the 123 ignitor distributor that can set advance by blue tooth. Is there a calculation to know what hardware to obtain, and which are the obvious first variables to modify? 95.:1 compression; 94 octane 100% fuel non lead.
This probably requires a semester of teaching or its a 200 level course, but I know I can get my mind around this. I have rebuilt my carbs and I know how they work. I am also a cheater or lazy, and I will ask the smart guy. The forums take off in a few directions, and often degenerate into ad hominem quips. I want high end power, but also to be able to take off from a light up a hill. I do track days in my 911, and I would take the '02 to classic meets.
please, what's the point of tilting the dcoe like that? you don't have a problem with the float level?
Good point, There is no reason to tilt it... its better not... but that is how the intake manifold is.... at the end it makes little difference as the fuel level in a narrow tube like the emulsion tube ( that is the only one that counts) is so minimal in terms of level.
@@D3Sshooter Great! thank you!
Thanks for the great video, when you say backfire is that like a miss fire from the exhaust ? I get a big pop through the carb going from idle to main that can be fixed by a bigger idle jet but carb is too rich for a smooth idle with the rich idle jet. This problem is at a light throttle just normal driving, if I give a heavy push on the throttle the car works fine. As the engine warms up the problem is less and only happens on slight hills giving throttle to stay at say 30 mph.
Thanks for your time.
Mike, backfire is indeed those explosions in t he exhaust.. I would in this case refer to another emulsion tube.. for slight accelerations ( like idle-progression-main and within main) you might want emulsion tube that is more lean on low RPM's like an F2 or F11
If you have 2 carbs, should you divede the jet sizes by 2 then?
Is it better to have one DCOE?
I Have two, not so easy to adjust
I had three of them on my TR six with a hot motor. It took me upwards of two years of research and trial and error, combined with a multitude of Jets corrector jets Venturis,pump jets emulsion tubes on and on. But damn, I had those carbs running like fuel injection when I was done
@2:58
I never understand that people put those wire mesh "filters" on their carbs: it keeps the AIR out of the engine (as in "very restrictive") and maybe a fly too. But not the abbrassive stuf (dust) which wear down your engine. 🤷🏼♂️
So better without those wire mesh and accept extra wear or a real airfilter which is not really restrictive if it is choosen big enough.
It is realy generous of You to share Your knowledge for free, realy apericiating that Steve! A sinsere thank You!
Hi. Very interesting video. Do you think you will make the same video for SU carburator as the system is not the same. I know you have a video on the tunning of it but one "on the circuit" may be usefull. Thanks.
I could, once I have a car with a SU... something to put on my to do list
@@D3Sshooter ho, has you made a video on it, I assumed you had one. Thanks anyway.
good job Sir as usual, have you ever tuned the 40's Weber for a Crossflow 1,7 liter?
This will be tremendously helpful when tuning my car. Very clear and understandable - Top stuff!
Glad it was helpful!
Thank You Steve.awesome video with clear information and excellent quality. You found a new subscriber. Cheers
Thanks Brad
Wouldn't it save alot of fuel, time + wear and tear if you fitted a wideband afr guage ?
Your videos are so good! Thank you so much for sharing your knowledge in a way that is. So easy to explain. Well done!
Glad you like them!
is that 4 main bearing? it looks so tiny against just one webber dcoe. hehe!
4:27 Steve, how do you determine (or measure) that the fuel pump delivers a sufficient amount of fuel to the engine, especially when you run your engine at high rpm?
That will be noticed by sputtering in the carb, as the fuel level gets low in the float chamber, thus the mixture gets more lean. Initially the steady driving at high RPM is ok, but after a time you lose power and the carb sputters. That is a typical indication... Always place a perfromance pump up with a return... that always works
@@D3Sshooter Thanks for explaining the tell-tales of a float chamber running out of fuel. Life would be so much easier if we somehow could measure directly the fuel level in that float chamber ...
Steve, do you think a 40 would work decent on a stock 1800? From block/head # we deduced it to be north of 9.5cr.
Yes, it will but make sure that you do the correct baseline on the choke and all the jets... have alook on my channel and look for playlist weber... I explain on how to go about it
Mant thanks for your most informative vidios Steve.
I have a Saab 96 v4 {a German Ford unit) It is a rally spec car with two weber dcoe 40s. When I test the air flows, I get differing numbers between barrels on the same carb. Is there any way to adjust this out?
Best regards
TXS for the comments, a lot depends on what type of intake manifold you have... if it is one to one , then change the yoke in the carb to have it matched... The difference is mainly because the porting/valve lift and or piston suction for each cylinder
Steve, many thanks for that.
the manifold is a "crossover" type , as the engine is of V4 configuration. It doesn't seem to pull air in any way. I think I will just have to live with it.
Thanks again for your wonderfull site.
Regards, John D.
o
,
Steve, when tuning carbs for lean and rich, did you examine the plugs. I remember as a youngster, reading that plug reading (examining the electrode colour and build up) was important when tuning carbs. Just a thought. Brilliant video as always. Have you also tried to do the tuning on a dyno with the idea, maximum power at a given rpm?? As always thanks so much.
Marc, indeed checking the plugs for color is another approach , but can fool you as for acceleration you can't rely on it. You could read the plugs for the main circuit if you can drive for a prolonged time on the main circuit and then stop and check them.. IMO its an aid, but its much better to test the engine hard out on the track. Yes my car has been on the dyno and that is why I also know that the powerband is in the mid-high RPM's. That is mainly due to the 300 degrees 720SP camshaft... But even without a dyno, one knows based on the camspecs, they always list the powerband... I might make a video on camshafts
@@D3Sshooter Thank you for your thoughtful reply. Look forward to more videos on the MG racer. Cheers.
Thanks for the tips I went to the F11 and it really helped to give much better run from idle to main jets.
Good to hear
Good looking car Steve.
Take care
Thank you
Are you using original Webers jets? Here in the states real original Weber jets are expensive.😕
Yes I do...as those are correctly machined. Of course you can buy them blanc and drill them out yourself.
Hi Steve. Did you consider making any changes to the choke size? Do you have any suggestions for choke size? I’ve a Mini with a 1340cc engine, Vizard VP3, cam. Mainly used for autocross and time attacks. I dropping the choke’s from 36mm to 32mm which makes the engine more streetable but it seems to have lost some power at the top ie 4th gear uphill.
Thanks Jim
JGB, yes I did set the choke size during the baseline video. There are many factors that determine the choke. For instance the cylinder CC's that the barrel needs to feed. If you have a four cylinder and one DCOE or two that makes a difference. Also the intake ports and intake manifold are affecting the choke. Not to mention the cylinder-head as some are Siamese ports (shared).. that all determines which choke. The main purpose of the choke is to be small enough to have high air velocity thereby creating that depression (venturi effect) at the opening of the aux venturie. At the same time it has to be big enough to allow sufficient airflow, thus velocity and volume are key.
Your 32 is IMO to narrow , under low load conditions it will be ok as less mass (air-fuel mixture is needed) but when under heavy load ( 4th and uphill) the engine needs lots of fuel and the 32 is to narrow to provide the mass... OK it does create sa good airspeed but the mass is not enough... I would go back to the 36 and work in the idle jets and emulsion tube type and or jets..
Thanks Steve I’ll give that a try.
Hi Steve, in hoeverre moet je rekening houden met droog of vochtig weer bij het afstellen van de carburateur?
Dat is wel een goede vraag, hetzelfde kan je stellen voor koud of warm weer en altitude... uiteindelijk gaat het om de hoeveelheid zuurstof die de AFR heeft. In principe doe je de kleine aanpassingen voor iedere track locatie en op die dag...
Excellent tutorial. Thanks
txs
Morning - Can you help, my weber appears to be leaking from the O ring manifold/weber mounting (Only after shutdown) what should I check? I have tightened the bolts which appears to have helped but want to make sure it is resolved for good
Thanks
Nítido
my pleasure
Steve - thank you for all these DCOE videos. I've watched all of them, I think, and have a much better understanding of the system. So I am going to try to tune the DCOE 45 on my MGB; I live in Colorado. Currently, the car bogs down in the 2500 RPM range; when I get up to about 3000, things perk up. Main jet = 140, Air Corrector = 215, emulsion = F11, idle jet 55f8. Based on this particular video, in your troubleshooting section, I am thinking about trying a smaller Air Corr, at least as a start. Again, thank you.
Man ya gonna make me swap out my Weber 32/36 conversion for the doce setup! Lol😊
hahaha you should
@@D3Sshooter awww man your not helping! Lol. I do love your other videos on the DOCE. But the question I have is would I have to sacrifice my brake booster? I know they make a short and long intake. And or I could get smaller stacks. You see how confused ya got me now?! Hahahaha.
Really like your videos and your way of explaining! I have a question. Spanish dcoes or fajs? I hear both can be tuned just fine and the low price makes it doable, of course🙂
Hi Lars, In one of my video's on the weber DGAS 37 I show the difference between a Spanish build and an Original Italian build weber. You will see all the issues with that Spanish build weber... look here ua-cam.com/video/TsnF-kjCxYo/v-deo.html Of course you can tune them after the corrections but are never as good as the real thing...IMO
Thanks for the reply! I will check out the video during supper🙂 Again, so glad to discover your channel. I am finnish building a Opel Ascona 400 for the street and i am now building a 400 for historic racing for friend and am going to build a Ascona A «steinmetz» historic for myself. So brushing up on the theory behind things is super!! Thanks
@@llarsk Thank you and good luck with your build
Surprised, you didn't use your wideband on the MG.
good old technology also works...
Man such a great video. I have been looking to tune my high speed circuit too. I think I have a massive backfire issue through 4-5k rpm. But once in a while it’ll pull clean to redline at 7k.
I’m thinking the 38mm Venturi is too big and doesn’t pull enough vacuum in the rev range.
Do you have a video that accurately depicts the exhaust backfire while going through the revving?
engine balanced?
This is a great video... Explains everything extremely well, dank u wel!
Nice seeing old rusty in background........hope it will come back on the channel.
Excelent video,excelent explanation!!Thanks!!
Cheers 👍
Love your work, Steve 👍
txs
My pleasure,
I can not express how helpful your videos are to tuning a Weber. I am still chasing my setup but your videos are excellent. Dual IDFs here and a bit of a pain :)
Thanks for the comments
Hi Steve, learning alot from your videos! thanks a lot. I fitted a pair of DCOE 45 carbs on my honda with an originally carbed 2000cc engine aiming for max. 6000rpm. for that i made a custom intake manifold as well. the runner length is 100mm and runner diameter is 45mm as are the carbs. it is running and driveable and i have good torque at 1500-2500rpm but when i open the throttle 70-100% (especially under load) it acts as if it hit rev limiter. feels like it doesn't have enough airspeed maybe? i can also only reach over 4000rpms in neutral by only opening the throttle max. about 40%. I have tried different ignition timing settings which only seemed to make a difference in the idle rpm. i also deleted the vacuum advance on the distributor. Should i try a different jetting maybe? The webers i bought new already had this jetting which according to your baselining video seemed to fit my engine quite well:
36mm Venturi Choke
4.5 Auxiliary Venturi
145 Main jet
F16 Emulsion tube
155 Air corrector jet
40 Pump exhaust valve
55F8 Idle jet
50 Pump jet
2.00 Needle valve
Thanks for the write-up..have a look on my video on how to baseline your weber... I would start with the progression work.. thus Idle Jets enlarge it .. as those play a role in those conditions. Try to measure with an AFR gauge , that will tell you more. Also make sure that your float level is correct , it might be to low
I just put a reproduction 48dcoe on a 4.9l ford in a 94 f150 it is mounted on a plate where the throttle body flange was it idles well and will accelerate hard until 3/4 throttle with the factory intake tubes and filter box but not open air horns never played with a side draft before also the distributor and sensors are still running off the computer not much difference between distributor connected or locked out
I would recommend to look at the video's on how to baseline your weber. Have this on my playlist webers
Great job helping so much
Good explanation.
Glad you liked it
enjoyed it so much. thank you!
you are a legend. thank you
supervideo!! thanks