souped up VX

[rossocorsa]

http://www.lancisti.net/albums/album84/DSCF1098.sized.jpg

the above is a picture of the carb installation on a scrap beta hpe vx that I have acquired. At the moment the engine, which has not been used for some months, is very hesitant and full of flatspots at low speed but goes like the proverbial when extended. I don't know if it is due to the usual woes from standing (eg muck in fuel etc) or the set up itself. I had thought to use this engine in my coupé. The set up is Weber DCOE40, injection beta inlet cam, recent new big end bearings, piston rings, valve guides, VW passat radiator (to allow space for carb) it seems quite well installed if not as neat and elegant as I would like (this will be sorted if I use it). Anyone got any observations that may help?

[Hamish]

Alan - I'm not at all jealous :roll: of your recent acquisition.....
First thoughts are likely to be exactly same as yours, ie: to clean out and blow through the carb jets etc, blow through the fuel line and generally overhaul the fuel system. Might be worth looking at the fuel pump - is it standard VX or has it been changed :?:
The normal practice is to fit a 45 DCOE or DHLA carb so I'm intrigued by the previous owners choice of a 40, but I suspect this is not the cause of the problem :twisted:
I'd have a look at the choke on the carb, these can get 'sticky' and come on even if they're not actually connected for use, a problem I once had on twin 40's fitted to a standard beta 2 litre. It might be worth ducting some hot air to the carb and see if that makes a difference.
Will be following this with interest :wink:

[Will]

...but the motor might not be pulling enough vacuum through the 40 DCOE to get the fuel vaporised properly. I'd try a good dismantlement and carb cleaning first, then I'd try idling the car with a hair dryer on the carb to see if warm air helps any.
You could have several issues, large venturi, cold weather, and gunky jets on the DCOE all contributing. These issues would tend to appear at idle and go away at WOT.
My .02.
-Will

[rossocorsa]

unfortunately the car it is in is both a wreck and not stored locally! I intend to investigate when next over there but it may be a case of sticking the engine in the coupe when it's ready and then simply seeing what can be done, alternatively I would need to con a friend into running it to see what happens

[Hamish]

alternatively I would need to con a friend into running it to see what happens

Allow me to offer my services :twisted: I'd be very careful with it :P

[Will]

Hamish- are you saying 45DCOE is normal?
I heard this was very lumpy. Since you own one of these, I'll defer to your judgement. What are you running? How's the idle?
What type of DCOE is it? Does it have a cold start device?
Try removing the screw next to the idle jet screw and clearing the progression holes underneath. This will cause flat spots on transition between idle and throttle, and is notorious for getting gummed up, as are the delivery valves and pump jets.
Another thing is that the carb MUST be isolated from the aluminum mounting block with a rubber o-ring or vibration from the SC will wreak havoc with the carb's float, so DO make sure you don't have any type of ridgid connection between the engine or SC and the carb.
-Will

[Will]

On second look, it appears there's no cold-start mechanism, but the ass end of the carb body looks open to atmosphere., is this correct? Hamish?
Or is there supposed to be a block-off plate?
-Will

[rossocorsa]

if you saw the car you'd know that this could only be done on an intermittent basis it is a complete WRECK...........

[rossocorsa]

On second look, it appears there's no cold-start mechanism, but the ass end of the carb body looks open to atmosphere., is this correct? Hamish?
Or is there supposed to be a block-off plate?
-Will


these are all the questions i need to answer but cannot until I next get to the car, it was in regular use so I can only assume that it did run better at some time

[Hamish]

Or is there supposed to be a block-off plate?
-Will

Will,
You're quite right, having looked at the carb again the 'choke section' (for want of a better technical/correct term :wink: ) at the rear of the carb (like your terminology better :twisted: ) appears to be missing...
Currently I'm not in too much of a position to comment too much just make observations as my car is still running standard carb, but I've had contact with several owners who have or are dong the same conversion - they've all gone the 45 route, can't see why it would be any lumpier :?: Surely only an exotic cam/poor set up would do that :?:

[Hamish]

if you saw the car you'd know that this could only be done on an intermittent basis it is a complete WRECK...........

You haven't seen my car recently..... :oops: :twisted:

[rossocorsa]

http://www.lancisti.net/albums/album84/DSCF1097.sized.jpghttp://www.lancisti.net/albums/album84/DSCF1096.sized.jpg

these give a better view of some areas, they are the only pics I have at the moment as it was 10pm at night when we got back with the car.

[rossocorsa]

Another thing is that the carb MUST be isolated from the aluminum mounting block with a rubber o-ring or vibration from the SC will wreak havoc with the carb's float, so DO make sure you don't have any type of ridgid connection between the engine or SC and the carb.
-Will

I'd already noticed that problem, it looks to me as if it is rigidly mounted, I've read that webber do a mounting kit so will investigate it

[Will]

Looks like you might already have isolators (thin plate under carb just showing in pics?) but hard to tell for sure.
More would be better though, the SC vibrates like a mother, compared to a normal intake manifold.
I had heard, third-hand of course, that a large DCOE was problematic off-throttle on a cold Volumex, because fuel would recondense on the rotors if it hadn't been totally vaporised by passing through a narrow venturi (small carb). This could be part of your problem, yet I suspect a good cleaning will help significantly.
-Will

[Wallace]

Well that's funny - I've heard that too - fule condensing out on the rotors giving rough mixture distribution - but others playing around with blowers and fuel injection seem to think a set of injectors is needed BEFORE the blower to "wet it" (persumably to act as a sealant).

Can't have it both ways !!

[rossocorsa]

I will have to see it will be at least a week before i can get back and see exactly how everything is installed but all the comments are useful to help me to know what to look for when i do,I am a bit suspicious about the intake temperature as well as it was a cold damp night when it was picked up I think the car was run with the mods in the summer the owner then had a minor crunch and lost interest

[Will]

On the sealing issue, David Beale, and I think Guy Croft also theorised this. I'm not sure I'm in agreement on that one, as it appears a LOT more fuel would be needed to seal the rotor leakage path, than what the car actually consumes!
The advantage I see of having the SC run "wet", is the ability to use the heat energy of the SC rotors to vaporize the fuel, while using the evaporative cooling to cool the rotors, or more accurately, the rotors and casing. However, both of the SC's that I have disassembled appear to have a pattern on the rotors which would seemingly not be consistent with the idea of the rotor actually being wetted by the fuel. Both had deposits that looked similar to inlet tract deposits, with checking lines which seemed to be indicative of the rotor expanding/contracting.
-Will

[peter_coupe]

Hi All

Just a quick remark regarding that carb and cold start choke or lack of it.

Big carbs usualy do fine without one, I have 2 x 42 DCNF and I do not have cold start connected at all, never had.

All you need is 3 squirts on the pedal and turn the key, never fails. Temperature here drops to -5, not sure for you guy's from Europe.

VX may be different beast but 45 sound very big, try and see.

Peter

[Wallace]

With you all the way on that one Will. ! If fuel condenses out in the blower - it isn't going to come out in nice, fine atomised droplets again !

As to the choke - never really used it on my engine fitted with twin Delorto's either. A couple of quick prods on the accelerator and she'd fire up.!

Thinking about it a bit more - the vx doesn't exactly have wild cams - so any problems with lumpy running at tick over and before the engine's warmed up wouldn't (I think !) be a problem with the Volumex engine anyway ! Might be different with a wild, long duration set though .. .

[Will]

On the Cold Start Device issue (Hate to call them chokes, they really aren't), I got out the trusty Haynes manual (you guys made me do it
) and found the 40DCOE 20 to 22's, and the 45DCOE 12 types are NOT supposed to have this the others are. Check the type number on the carb housing to see what it is. From the exploded diagram shown, it looks like if the works were removed, and no block off plate were used, that might allow air to get sucked through the cold start circuit and lean out the carb. (small vacuum leak to the fuel circuit, basically). I would investigate this, as it looks like it may have been removed to fit the carb to the aluminum mounting block. Sealing this puppy off may improve idle.
My .02
-Will

[rossocorsa]

hopefully I'm going to get over on Saturday and check it all out more thoroughly, the whole thing is not a disaster come what may as the car was very cheap :wink: and the blower (or is it sucker on a vx??) appears to be ok

[Hamish]

hopefully I'm going to get over on Saturday and check it all out more thoroughly

Don't forget to take the camera :wink: :!:

[rossocorsa]

went over to have another look yesterday but as usual got side tracked with other things so I didn't spend a lot of time on it. The carb was loose on its mounting at the top which might have caused an airleak which wouldn't help, it does have the rubber anti-vibration mounting so that is ok. I e-mailed the previous owner who made the following observations

" your flat spots under low revs are due to lack of smoothness on the accelerator - snap open the throttle at anything less than 3,500 rpm and this is what you achieve - flat spots is fuel wetting out on the super charger - low flow through a fully open carb body etc. You can smooth it a little by increasing the size of the idle jets but this tends to screw you on tick over.

remember by converting it to take DCOE you lose the heated inlet manifold!

you will also get problems with icing of the carb in winter - I'm not sure what configuration I left it in but in winter I usually fitted a blanking plate behind the grill in front of the air filter and ducted some air off the back of the radiator to keep the carb body warm - an improvement but not a complete solution.

the key to running it how I left it set up is to be gentle with the accelerator at low rpm. not on off, but grow with rpm. once over 3000 to 3500 then full throttle is fine - that pus from 90 to 120mph always did it for me!

I developed the set up iteratively starting from suggested values in the guy croft bible. think i ended up running slightly small mains and idles."

the blanking plate is fitted as is a small scoop behind the radiator that I presume is intended to feed warm air to the carb, it would not appear to be all that effective though. The cold start device is definitely missing I don't know if there would be a leak through it but I intend to blank it off anyway just in case. I have not been able to see what size chokes are fitted (the front of the carb is quite inaccessable without removing the grille which I didn't have time to do) but I think this could be the root of the problem. I suspect a smaller choke size coupled with a smaller blower pulley may well improve response whilst achieving similar top end power , we shall see!!!

[rossocorsa]

I've added a new album for this engine go to

http://www.lancisti.net/forum/modules.php?set_albumName=albun27&op=modload&name=gallery&file=index&include=view_album.php

[Will]

Interesting that we seem to have diagnosed the two probable problems without seeing more than a pic and hearing the symptoms...we must have too much time on our hands, or know the cars a tad too well. :roll:
-Will

[rossocorsa]

more info from the previous owner,

"alan - throught through the back fire a little more last night - as I'm sure you know the backfire does not blow back through the carb (supercharger in the way) but through the pressure release valve - if this has seen a bit too much action you get carbon build up which can jam the valve open by a small amount - this again introduces a leak path into the manifold - leaning off the mixture inducing more back-fire. I have also seen the O ring seal cut through.

may also be worth upping the spring pressure / swapping for different spring - at high speed/full throttle, from the cabin smell, the valve was leaking.

choke i think is 28mm

looking through my jet box i have
mains 135, 145 & 150 (assume the car was running on 140's)
air correctors 190 plus some resized ones - not stamped up which is always handy!
idles 50's & 65's - i think the car is running on something smaller
pump jets 35's & 45's - think the car is running 35's (not too sure why i have 2 sets?) - increasing these is meant to aid snap response - did not work too well for me.


as for loose carbs - i remember having some fun - I had the carb off for some reason , was running late for some dinner at a mates house and obvously did not re tighten correctly - got there ok but getting home was a different matter - the car would not run (never mind tick) over under 3500 rpm - must have amused the neighbours as ever.

I think I left it set up with cosworth style seals with rubber cup washers - these should be left as loose as posible to isolate the carb from engine vibration - frothing fuel - hunting at idle etc. while still sealing."

[Will]

The valve on the intake manifold should be a pretty hard spring- about double what the blower could put out.
I am wondering what o-ring you are talking about, as far as I know there isn't one internally on mine, and there's a copper crush washer between the valve and manifold.?
-Will

[rossocorsa]

this is all info cut and pasted from mail from the previous owner I am not too sure what o ring he is refering to either I will try to find out

[Bazza]

We found that in order to get proper fuelling with a 45mm. DCOE we had to use main jets larger than any manufactured by Weber - we had no option but to drill them out.

Spitting back may well put the rotors of your supercharger out of phase and this can cause catastrophic damage to the blower - the relief valve is simply not big enough.

[rossocorsa]

I can see that this could be a problem, am I right in thinking that the blower rotors are not keyed to their shafts? I have seen dire warnings about not removing pulleys etc.. as it can put the rotors out of phase I presume this is why?.

[Hamish]

We found that in order to get proper fuelling with a 45mm. DCOE we had to use main jets larger than any manufactured by Weber - we had no option but to drill them out.

Interesting, it seems increasingly plausible that a 40 DCOE is the way forward :?: Having just got 'Mario' back from a rolling road tune I'm increasingly looking forward to putting on my 'tweaked' cylinder head and a sidedraught conversion :wink: when/if I get around to doing it :oops: For folks who are interested the car made 135 BHP at 5,000rpm but the guy at the tuners said the figure is not right as they hadn't corrected for barometric pressure or temperature and had not worked the engine hard as it's only recently had a bottom end rebuild :D the upshot of that is the think it's making closer to 150 BHP - I'm not convinced yet :!:
The engine only differs from standard by having a brand new carb and one of Bazzas overdrive pulleys on the blower :P
Although they reset the timing at the tuning shop - doen't make expensive noises any more :!: - the carb 'fine tune' set up is dire :cry: and I can see what I'll be doing next days off.... :evil:

[johanz]

What do you recommend for setup for a Weber 45 on my standard VX ?

[Hamish]

What do you recommend for setup for a Weber 45 on my standard VX ?

Suggest you speak to Guy Croft or try any of the guys here who've done it.... presumably you're after choke/jets sizes?

[Fingers]

I'm going to get around to putting the 45 DCOE on my VX coupe soon I hope, just haven't got thre time to go near it at the moment, I've got the carb, manifold, and linkage all ready to go and as soon as I get a chance am going to sort out moving the radiator. Anyway the point of all this is that I'm going to start with 145 main jets, 180 air correctors, and 32 mm chokes and see how it goes from there. The next thing after that will be a cam from Guy Croft, his 3A, but for us Kiwis £200 is big dollars. I'm thinking that it's probably better to get it all ready to go (rad moved and cables run) and do the cam and the carb at the same time so I won't have to mess around with jetting.

[johanz]

Yes, I´ve talked to Guy Croft, It´s his trade secret, If I buy a carburettor from him i will set it up..

[DJ]

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