Well Matt with the effort I'm sure you are going to put into it, tou are going to solve this. Sometimes I think why all these problems and then I think oh yes it was a hobby, so solving the problem should be too! Good luck
If it does less without the filter, it needs more main jet, depending on having velocity stacks still on. If you were drawing the air in against the bare straight edge of the carb body, that kills the dynamic CSA, as the edge creates a turbulence around it. There also should be a way to adjust part throttle and booster. If the carb opening is too small, the engine pulls enough vacuum to activate the booster on part throttle, fauling the plugs. Then there's the transition from carb to intake plenum. A step here destroys any kind of attempt for a tune. To keep the cam in, I would get a bigger carb with velocity stacks, blend that to the intake, make sure the intake is flush with the head openings, then start to tune the carb.
I have run race mini 1330cc engines on twin HIF 44 carbs making 105 hp and never had a problem with fuel fouling the outer plugs, but I was using a Metro electronic distributor, so I wonder if you have a spark problem as you look like you are running a wasted spark ignition which will do 1 and 4 and 2 and 3 together. Anyway, hope you have a amazing festive time and look forward to more videos and maybe catch you at a track day next year. I always go to Combe. Cheers Kim.
If the dyno readout is right then it is ridiculously rich lower in the revs it will be washing the bores and wetting the plugs, it's down near 9:1 AFR somewhere, would sort that out first then see what is happening with the plugs etc
I wrote it already. You need AFR gauge!!! idle jets work ( with progression hole ) until 3000-4000 rpm ( it depends on which size of choke ). At higher revs work only main jet. ( you can then take out idle jets - engine will still run ). Don't test dyno without sure you have the correct AFR full rev range
I’m not that far from you, the only place I have found to get minis rolling roaded is Southam mini & metro centre they are a bit of a trek up in Southam, Warwickshire but Colin’s your man and keeps loads of Weber bits
What cc are you and what cam are you running, 649? 1.3 or 1.5 rockers make a surprisingly small difference if you are so don't waste your money changing them. What compression is this engine, 11:1 like migs or more? If its about there then you'll also find that there's a huge window where the ignition makes very little difference, you'll find from about 28 degrees to 36 makes no difference to the power, because the compression is relatively low. Migs always have that hideous rich area on WOT between 4 and 5k, you won't tune that out i'm afraid (I've running several of the race winning migs on our rollers, including Endaf's, many times)
Really need to get the weber and ign map calibrated on a dyno, ideally Miglia specialist, if you keep driving it that rich your gonna wash the bores out before you’ve even started, guessing rings not been ran in?
I am no expert on A series but I have seen similar issues in the past with these low to mid range flat spots on DCOEs when the owners have fitted way too big chokes. It might be worth trying smaller chokes to see how it behaves. I would also try a different manifold. Someone in the Mini Miglia paddock must know the best combo to use. I remember the late Peter Baldwin was the man to go to for Mini tuning. A real gent and a multiple Mini Miglia champion. Sadly a lot of the old school carb tuning is declining, mapping is all anyone seems to care about nowadays but carbs are still widely used and there are people out there who do them.
Many race minis use this manifold don't they? Unlikely to be the issue. Just changing idle jets was the main problem and limitation here I think. They don't do much after 1500RPM+ especially in an engine built this way. Choke+Main jets will have way more of an impact.
You can’t beat going to a specialist for getting the most out if these engines and also they know where the engine should be compared to others. Kad/ Swiftune dyno or Slark rolling road for example. I used Swiftune and the late legend Peter Baldwin and you know they will get every last bit out of the engine.
I would start by adding lambda ports on each exhaust manifold branch (less than £10 for 3), then buy or borrow a portable lambda reader, then you can do your own carb tuning under load without having to travel to a rolling road, particularly since the problem seems to be at the lower end of the rev range. To check the engine you could borrow a twin carb intake manifold and add a pair of HIF44s (which are quite cheap in good used condition, and easily resold) Then you will find out if the engine is OK, I suspect it is fine but that remains to be proved. My suspicion would be the Weber inlet manifold but maybe not.
You need to take it to someone who knows carbs. Seems you need to try different emulsions tubes. F16 is always a good starting point. Missab plates between carb and manifold.
I would advise on fitting Misab plates between the carbs and manifold as the type you have can pop the o ring on a back fire . Sure Merlins will sell them at Coombe
If your dyno man isn’t good with carbs, I’d be looking elsewhere. I’m no expert of carbs but I have had a couple of inline 4 bikes with carbs and still own one. There’s at least three carb experts in my area if I need one, surely there’s a carb man where you live?
You really need to find somewhere with a stock of jets etc. I had my Mini set up by Airey Tuning in Cheriton more then a few years ago so somewhere like them might be able to help. I've got a big single SU on mine and with a 286 cam and high lift rockers it never ran very well under 2000rpm. Is the jet size info in David Vizards book any help with the setup you have ?
Wouldn't the wet cylinder lose compression from the extra fuel thinning the oil on the outer cylinders, I would think jetting the carb with a smaller jet in the low to mid range would make a massive difference all though the rev range , good luck 🤞
David Visard made a great video (Why cam companies cam timing cards are almost always wrong) showing how valve seat angle effects optimum cam timing. He found a lot of cam manufacturers timing recommendations are wrong because they don't take valve seat angle into account and he showed significant gains by tweaking them. The general gist was that 30 degree valve seat angles allow more flow as the valves start to open than 45 - 55 degree valve seat angles so cam timing base settings need to be advanced or retarded accordingly.
The dyno man is not up to the job for webers no good messing about with idle jets when it rich middle range,always do compresion checks on full throttle too get max air flow.
Compression checks were done with wot. As I said in the video, he doesn't stock any jets. It was supposed to be a quick swap of idle jets and a few power runs to see what it makes.
I am pleased it was not just me that saw / sees that - if you look at say 1.34, it looks as if the carbs are not tight against the manifold. All looks a bit lose. That is going to cause a problem.
@@edwardgurhy100 Thats totally normal, as usually you fit some rubber (big ring) between the mounts to isolate the carb, so the fuel there in doesn't get vibrated to uncontrollable levels.
Fix one problem and another will come along trying to frustrate you. Always a joy to watch you Matt. Seasons Greetings
Well Matt with the effort I'm sure you are going to put into it, tou are going to solve this. Sometimes I think why all these problems and then I think oh yes it was a hobby, so solving the problem should be too! Good luck
That sound so good !!
Looks like you've nailed this build! Merry Christmas!
Cheers
If it does less without the filter, it needs more main jet, depending on having velocity stacks still on. If you were drawing the air in against the bare straight edge of the carb body, that kills the dynamic CSA, as the edge creates a turbulence around it. There also should be a way to adjust part throttle and booster. If the carb opening is too small, the engine pulls enough vacuum to activate the booster on part throttle, fauling the plugs. Then there's the transition from carb to intake plenum. A step here destroys any kind of attempt for a tune.
To keep the cam in, I would get a bigger carb with velocity stacks, blend that to the intake, make sure the intake is flush with the head openings, then start to tune the carb.
I have run race mini 1330cc engines on twin HIF 44 carbs making 105 hp and never had a problem with fuel fouling the outer plugs, but I was using a Metro electronic distributor, so I wonder if you have a spark problem as you look like you are running a wasted spark ignition which will do 1 and 4 and 2 and 3 together. Anyway, hope you have a amazing festive time and look forward to more videos and maybe catch you at a track day next year. I always go to Combe. Cheers Kim.
spark plugs may be too cold
If the dyno readout is right then it is ridiculously rich lower in the revs it will be washing the bores and wetting the plugs, it's down near 9:1 AFR somewhere, would sort that out first then see what is happening with the plugs etc
Merry xmas all, I'd try 36mm chokes, the 38's maybe a bit too big.
Is that goose neck inlet manifold anygood and on the siamese split on the head knife edge or rounded
Just remembered, I had twin DCOE on my tuned Ford Mexico……..those were the days. Plus supper Oscar rallie spot lights
So what im getting at is I think there is a flow issue? I had the same set up and no issues except my inlet was tubular and flowed extremely well
I wrote it already. You need AFR gauge!!! idle jets work ( with progression hole ) until 3000-4000 rpm ( it depends on which size of choke ). At higher revs work only main jet. ( you can then take out idle jets - engine will still run ). Don't test dyno without sure you have the correct AFR full rev range
p.s: ua-cam.com/video/1pkFSA_rRFI/v-deo.html&ab_channel=SidneyCriticComedyHound
I’m not that far from you, the only place I have found to get minis rolling roaded is Southam mini & metro centre they are a bit of a trek up in Southam, Warwickshire but Colin’s your man and keeps loads of Weber bits
The lower compression must be caused by cylinder wash due to over fueling
What cc are you and what cam are you running, 649? 1.3 or 1.5 rockers make a surprisingly small difference if you are so don't waste your money changing them. What compression is this engine, 11:1 like migs or more? If its about there then you'll also find that there's a huge window where the ignition makes very little difference, you'll find from about 28 degrees to 36 makes no difference to the power, because the compression is relatively low. Migs always have that hideous rich area on WOT between 4 and 5k, you won't tune that out i'm afraid (I've running several of the race winning migs on our rollers, including Endaf's, many times)
It's a 1293 11.3:1 compression, 1.5 roller rockers, sw23 cam. Have you ever had issues with wetting 1 and 4 at idle? Cheers
Really need to get the weber and ign map calibrated on a dyno, ideally Miglia specialist, if you keep driving it that rich your gonna wash the bores out before you’ve even started, guessing rings not been ran in?
Its been run in on an engine dyno prior to fitting. I wont be driving it until it been back on the rollers again.
I am no expert on A series but I have seen similar issues in the past with these low to mid range flat spots on DCOEs when the owners have fitted way too big chokes. It might be worth trying smaller chokes to see how it behaves. I would also try a different manifold. Someone in the Mini Miglia paddock must know the best combo to use. I remember the late Peter Baldwin was the man to go to for Mini tuning. A real gent and a multiple Mini Miglia champion. Sadly a lot of the old school carb tuning is declining, mapping is all anyone seems to care about nowadays but carbs are still widely used and there are people out there who do them.
Many race minis use this manifold don't they? Unlikely to be the issue. Just changing idle jets was the main problem and limitation here I think. They don't do much after 1500RPM+ especially in an engine built this way. Choke+Main jets will have way more of an impact.
A lot of the migs do seem to run a much shorter manifold so its probably worth looking at.
Miglias will run a maniflow tubular manifold I think 3 3/4” length (or around this size depending on engine characteristics)
You can’t beat going to a specialist for getting the most out if these engines and also they know where the engine should be compared to others. Kad/ Swiftune dyno or Slark rolling road for example. I used Swiftune and the late legend Peter Baldwin and you know they will get every last bit out of the engine.
Has it got to be carb'd..?? What about TB's..??
Can only be one TB unless you go complex like the MPIs are.
Malc at TTP performance Bromsgrove is ya man to set that up best in the business 😊
I agree, all of my A series builds go to malc at TTP, he's a great guy and very knowledgeable.
@pauljeffries my little bro he's the best at wot he dose
I would start by adding lambda ports on each exhaust manifold branch (less than £10 for 3), then buy or borrow a portable lambda reader, then you can do your own carb tuning under load without having to travel to a rolling road, particularly since the problem seems to be at the lower end of the rev range. To check the engine you could borrow a twin carb intake manifold and add a pair of HIF44s (which are quite cheap in good used condition, and easily resold) Then you will find out if the engine is OK, I suspect it is fine but that remains to be proved. My suspicion would be the Weber inlet manifold but maybe not.
Merry Christmas and new year from nz.
You need to take it to someone who knows carbs. Seems you need to try different emulsions tubes. F16 is always a good starting point. Missab plates between carb and manifold.
I would advise on fitting Misab plates between the carbs and manifold as the type you have can pop the o ring on a back fire . Sure Merlins will sell them at Coombe
Reminds me of my youth, DCO’s make such great sounds………………..close your eyes and you’d think you were on the RAC rally
Did you say 2 or 3 PSI ??
Either should work fine if the needle+floats are fine.
I've tried 2, 2.5 and 3
If your dyno man isn’t good with carbs, I’d be looking elsewhere. I’m no expert of carbs but I have had a couple of inline 4 bikes with carbs and still own one. There’s at least three carb experts in my area if I need one, surely there’s a carb man where you live?
See you on the next one, Matt.
You really need to find somewhere with a stock of jets etc. I had my Mini set up by Airey Tuning in Cheriton more then a few years ago so somewhere like them might be able to help. I've got a big single SU on mine and with a 286 cam and high lift rockers it never ran very well under 2000rpm. Is the jet size info in David Vizards book any help with the setup you have ?
There are recommendations in the book but there's so many variables. I will get it ironed out soon. Cheers
Had a 1275 Midget in a Moggie 1000 and it did the same with 1 and 4 cylinders
Go for split Webers. That will cure the richer mixture going to the outer two cylinders.
Wouldn't the wet cylinder lose compression from the extra fuel thinning the oil on the outer cylinders, I would think jetting the carb with a smaller jet in the low to mid range would make a massive difference all though the rev range , good luck 🤞
If you believe the carburetor is affecting the compression remove it and test engine without carburetor
David Visard made a great video (Why cam companies cam timing cards are almost always wrong) showing how valve seat angle effects optimum cam timing. He found a lot of cam manufacturers timing recommendations are wrong because they don't take valve seat angle into account and he showed significant gains by tweaking them. The general gist was that 30 degree valve seat angles allow more flow as the valves start to open than 45 - 55 degree valve seat angles so cam timing base settings need to be advanced or retarded accordingly.
I do have his book on the mini engine. its not possible to swing the cam timing with the engine in the car unfortunately.
Maby thats why the split-Weber setup was done…?
Because of the enerti of the misture goes toward the outher cylinders. Manifolddesign….
Hmm, I don't know why that's done but it would make sense.
The dyno man is not up to the job for webers no good messing about with idle jets when it rich middle range,always do compresion checks on full throttle too get max air flow.
Compression checks were done with wot. As I said in the video, he doesn't stock any jets. It was supposed to be a quick swap of idle jets and a few power runs to see what it makes.
@Urchfab i wasnt critising just trying to help i know you will get it right.
It looks like the carbs are not tight to the manifold.
I am pleased it was not just me that saw / sees that - if you look at say 1.34, it looks as if the carbs are not tight against the manifold. All looks a bit lose. That is going to cause a problem.
@@edwardgurhy100 Thats totally normal, as usually you fit some rubber (big ring) between the mounts to isolate the carb, so the fuel there in doesn't get vibrated to uncontrollable levels.
If you watch on a bigger screen you can see the black gaskets. It isn't loose.
Spanish Webers :-/
the honda likes a long cold air intake 1000mm