Crypton Synchro Check Instructions
Discussion
Has anyone got the instruction sheet for one of these?
Essentially, what I need to know is, when the engine is running, should the needle be steady or fluctuating between two numbers? I'm trying to tune a pair of DCOE's and seem to have both results on the same carb/different inlets, even with the mixture screws set the same. Turning the mixture screws doesn't have any effect ie the steady one stays steady and the oscillating continues to flap about.
Any suggestions?
Thanks in advance
Essentially, what I need to know is, when the engine is running, should the needle be steady or fluctuating between two numbers? I'm trying to tune a pair of DCOE's and seem to have both results on the same carb/different inlets, even with the mixture screws set the same. Turning the mixture screws doesn't have any effect ie the steady one stays steady and the oscillating continues to flap about.
Any suggestions?
Thanks in advance
I'm pretty sure I have one of those still in it's box in my pile of accumulated toot, unfortunately I'm away until next Saturday but will have a look then.
Just a thought but with a pair of side draughts you are measuring undamped pulses whereas Sus or Stromberg's usually share at least two inlets often with a balance tube between them so should give a smoother signal.
Tim
Just a thought but with a pair of side draughts you are measuring undamped pulses whereas Sus or Stromberg's usually share at least two inlets often with a balance tube between them so should give a smoother signal.
Tim
the other tim said:
I'm pretty sure I have one of those still in it's box in my pile of accumulated toot, ....
Thanks Tim, no rush. You might be pleasantly surprised what these are selling for on eBay at the moment.the other tim said:
...
Just a thought but with a pair of side draughts you are measuring undamped pulses whereas Sus or Stromberg's usually share at least two inlets often with a balance tube between them so should give a smoother signal....
True, but why would I be seeing an osciating reading on one barrel and a smooth reading of the other barrel on the same carb?Just a thought but with a pair of side draughts you are measuring undamped pulses whereas Sus or Stromberg's usually share at least two inlets often with a balance tube between them so should give a smoother signal....
Confused
Does anyone have any tips on how to set up the balance linkage between the two carbs for the initial set-up of the mixture screws?
AH - brings back memories that does - used one of those quite a lot on my old Triumph saloons.
It's just a flow meter, and it isn't damped all that well, just a spring. On the one I had there's a button near the bottom which
can be pulled out to change the sensitivity.
It works quite well on Stromberg/SU on a more 'shared' manifold, but if you're using it on 40DCOEs it's going to be harder as the inlet pulses
will be more separated (assuming it's a 4 cyl engine) and so needle will probably will bounce around a lot. A hot cam will make it worse too.
I can only suggest temporarily turning up the idle a bit ...
And then simply try to get the readings as near equal as poss (but you knew that already....)
It's just a flow meter, and it isn't damped all that well, just a spring. On the one I had there's a button near the bottom which
can be pulled out to change the sensitivity.
It works quite well on Stromberg/SU on a more 'shared' manifold, but if you're using it on 40DCOEs it's going to be harder as the inlet pulses
will be more separated (assuming it's a 4 cyl engine) and so needle will probably will bounce around a lot. A hot cam will make it worse too.
I can only suggest temporarily turning up the idle a bit ...
And then simply try to get the readings as near equal as poss (but you knew that already....)
v8s4me said:
True, but why would I be seeing an osciating reading on one barrel and a smooth reading of the other barrel on the same carb?
Confused
er....that sounds a bit weird to me, it is a true 'one per cylinder' inlet ? Is it the one connected to the brake servo (bigger volume will tend to smooth out the pulses, even with a valve) or even PCV (if it has one). Confused
I've mostly done twin SU setups, I would start with mixture and idle set the same (screw in as far as poss and adjust out say 5 turns, and then try to adjust as a pair). To be honest though after a while you can do twin SU by just watching engine...
Oh, and from you photo, that seal isn't original - they had a rubber cone to allow for different carb sizes
RCK974X said:
...Is it the one connected to the brake servo (bigger volume will tend to smooth out the pulses, even with a valve) ...
Yes it is. That explains that then. Thank you.RCK974X said:
....Oh, and from you photo, that seal isn't original - they had a rubber cone to allow for different carb sizes.
I think that must have perished and fallen off some time ago. This has a home-made rubber seal; it works OK but it is a bit hard, meaning the gauge has to be held onto the carb quite firmly, adding to the vibration. I'm looking out for some closed cell foam to make something more suitable.Thanks for your help.
No worries.
Rubber cone - the original wasn't that soft either - you had to push pretty hard to seal properly (but that could have been old age too !)
Yeah closed cell, or soft rubber if you can find some....adapted door seal ? Even a household door mat ? (Yeah weird, but sometimes...)
good luck with the tuning.
If you ever see a cheap one, the old Gunsons colortune did actually work for mixture settings, although you have to be in a dark shed or car park dark corner to see it properly, but worth a few bucks.
Rubber cone - the original wasn't that soft either - you had to push pretty hard to seal properly (but that could have been old age too !)
Yeah closed cell, or soft rubber if you can find some....adapted door seal ? Even a household door mat ? (Yeah weird, but sometimes...)
good luck with the tuning.
If you ever see a cheap one, the old Gunsons colortune did actually work for mixture settings, although you have to be in a dark shed or car park dark corner to see it properly, but worth a few bucks.
RCK974X said:
...If you ever see a cheap one, the old Gunson's Colortune did actually work for mixture settings...
I've still got one of those as well! I used that to set the mixture screws on each cylinder. That got the whole thing ticking over nice and smoothly.Then I used the Synchro and got the strange readings. The issue is, it is dying when the throttle is opened sharply. We've already gone up a size on the idle jet, which did improve things a bit, but the problem is still there. We can always go up another size on the idle jet but I want to rule out any issues with the way the linkage is set up first.
Do 40DCOE carbs have an accelerator pump ? [I don't know enough about them ]
On more ordinary carbs, when you hit the throttle the carb pumps in some neat fuel to richen the mixture.
This is called an accelerator pump (or enrichment pump) in common language.
If engine stalls when throttle opened suddenly, it sounds like you need more fuel at that point, i.e. more accel pump.
I checked on web and it says 40DCOE have separate 'pump jet' size, so I guess you will need a bigger pump jet(s) ?
Anyone else help ? I've never worked on these carbs....
On more ordinary carbs, when you hit the throttle the carb pumps in some neat fuel to richen the mixture.
This is called an accelerator pump (or enrichment pump) in common language.
If engine stalls when throttle opened suddenly, it sounds like you need more fuel at that point, i.e. more accel pump.
I checked on web and it says 40DCOE have separate 'pump jet' size, so I guess you will need a bigger pump jet(s) ?
Anyone else help ? I've never worked on these carbs....
This is worth its weight in brain cells and buggeration:
http://www.amazon.com/Weber-Carburetors-Owners-Wor...
http://www.amazon.com/Weber-Carburetors-Owners-Wor...
I run twin DCOEs on my Vixen and it took me a while to get mine to behave. I took a small drill to the air correction holes on my idle jets which sorted mine out but not suggesting that you do the same.
I agree with New Zealand Andy in that it sounds as if you are running too weak in the critical progression phase when you come off idle and onto the throttle. The syncro tool is useful in helping you to balance the airflow between the two carbs through a combination of adjusting the four idle screws and the throttle linkage balance. The reason why one of your readings was oscillating is because that particular carb is hunting and probably too weak compared to the other. The syncro tool won't help you to determine whether or not you are running optimum fuel/air mixtures but should help you to get a balanced air flow for a smooth tick over. If you a running a hot cam you will need to aim for a slightly faster tick over. There are plenty of good on-line articles about webber tuning. If you can't find any then pm me and I will email some over to you.
I agree with New Zealand Andy in that it sounds as if you are running too weak in the critical progression phase when you come off idle and onto the throttle. The syncro tool is useful in helping you to balance the airflow between the two carbs through a combination of adjusting the four idle screws and the throttle linkage balance. The reason why one of your readings was oscillating is because that particular carb is hunting and probably too weak compared to the other. The syncro tool won't help you to determine whether or not you are running optimum fuel/air mixtures but should help you to get a balanced air flow for a smooth tick over. If you a running a hot cam you will need to aim for a slightly faster tick over. There are plenty of good on-line articles about webber tuning. If you can't find any then pm me and I will email some over to you.
V6Pushfit said:
This is worth its weight in brain cells and buggeration:
http://www.amazon.com/Weber-Carburetors-Owners-Wor...
I bought one of these but it doesn't offer anything not already available on the Web. There is just one section on the DCOE and in that a few brief paragraphs on tuning. There is much much more available on the net so save your money and get Googling.http://www.amazon.com/Weber-Carburetors-Owners-Wor...
Andy - thanks for your help.
Update - fitting larger idle jets and re-balancing has helped, and the mixture screws are where that should be with a nice blue flame in the Colortune. But it still coughs and stalls when the throttle is snapped open. The timing is advancing as it should so, is the next step (a) larger idle jet, which will be F6 or (b) a larger pump jet? It is currently fitted with 40 so the next size up would be 45. (1700 X-Flow).
Any suggestions?
v8s4me said:
I bought one of these but it doesn't offer anything not already available on the Web. There is just one section on the DCOE and in that a few brief paragraphs on tuning. There is much much more available on the net so save your money and get Googling.
The manual is about six quid, the web can be very misleading.Just trying to help
"How To Build & Power Tune Weber DCOE & Dellorto DHLA" recommends a 50 idle jet for 425cc per cylinder, F part is the air bleed (F6 being the richest air bleed).
40 pump is probably around right, we're running a 35 pump on our 1600M with twin dellortos, we've got a 60 idle though because we've got H (alfa) carbs which have a fixed idle air bleed.
If you're really quick with the throttle from idle, it does stutter a little, when on the road though it's fine most of the time so long as you're in the power band.
Does it rev ok when you build the revs up slowly? (eliminating the pump jets).
Might want to check the accelerator pump discharge bleed valve (pump spill valve) in the float chamber. This increases/decreases the amount of fuel sent to the pump jets.
40 pump is probably around right, we're running a 35 pump on our 1600M with twin dellortos, we've got a 60 idle though because we've got H (alfa) carbs which have a fixed idle air bleed.
If you're really quick with the throttle from idle, it does stutter a little, when on the road though it's fine most of the time so long as you're in the power band.
Does it rev ok when you build the revs up slowly? (eliminating the pump jets).
Might want to check the accelerator pump discharge bleed valve (pump spill valve) in the float chamber. This increases/decreases the amount of fuel sent to the pump jets.
Edited by Cerberus90 on Wednesday 4th May 18:22
Edited by Cerberus90 on Wednesday 4th May 18:26
Cerberus90 said:
...Does it rev ok when you build the revs up slowly? (eliminating the pump jets)...
It does, and the Colortune indicates the mixture is staying on the right side of rich as the revs increase. This is why I'm thinking the next step should be the pump jets because, if I understand the process correctly, this is what will give the additional squirt of petrol when the throttle is snapped open. Clearly too big a squirt would probably produce a similar splutter.With 55/f8 idle jets the mixture screws had to be turned out more than 2 1/2 turns. Fitting 55/f9 improved the idle mixture significantly and now the idle screws are 1 1/2 turns out (+/- 1/8), so that's why I'm thinking we are about right on the idle jet now.
From your description
1) engine is fine throttle opened slowly
2) stumbles/stalls on quick opening.
I'd go for larger pump jet(s) first.
And remember you may still find your calibration isn't quite right on the road, as load etc. can make a big difference.
So you may need to revisit a few times, but each time will be a step nearer !
NB. Colortune should show a momentary yellow (rich) when throttle opened quickly, which is from the accel pump, or at least all the
ones I used to work on did that. So that's another clue.
May be worth doing a web trawl to see if anyone has posted their jets sizes/cal on a similar engine ?? Or have you done that already ?
1) engine is fine throttle opened slowly
2) stumbles/stalls on quick opening.
I'd go for larger pump jet(s) first.
And remember you may still find your calibration isn't quite right on the road, as load etc. can make a big difference.
So you may need to revisit a few times, but each time will be a step nearer !
NB. Colortune should show a momentary yellow (rich) when throttle opened quickly, which is from the accel pump, or at least all the
ones I used to work on did that. So that's another clue.
May be worth doing a web trawl to see if anyone has posted their jets sizes/cal on a similar engine ?? Or have you done that already ?
RCK974X said:
From your description
1) engine is fine throttle opened slowly
2) stumbles/stalls on quick opening....
Correct.1) engine is fine throttle opened slowly
2) stumbles/stalls on quick opening....
RCK974X said:
...NB. Colortune should show a momentary yellow (rich) when throttle opened quickly...
It does.RCK974X said:
....I'd go for larger pump jet(s) first......May be worth doing a web trawl to see if anyone has posted their jets sizes/cal on a similar engine ?...
Thanks for the tip.Just in case, I thought of this later on last night, it could also be the jets are too LARGE ... if so, engine may flood and stall.
I don't think that's as likely as too small, but it's possible.
I guess you may be able to smell unburnt petrol at the exhaust pipe if it's too large, not sure....
I can only say try to keep an open mind and always allow for a fault being something not what you expected.....
I don't think that's as likely as too small, but it's possible.
I guess you may be able to smell unburnt petrol at the exhaust pipe if it's too large, not sure....
I can only say try to keep an open mind and always allow for a fault being something not what you expected.....
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