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MG Midget and Sprite Technical - Weber setup

So i need some help with the setup of my 45 Weber.

It was set up on a RR by the PO producing 84 BHP
Since then it has had a rebuild being over bored to make it a 1380 and had a difrent head fitted.

After a fuel leak i found out that the weber is jeted a bit unusual.

The engine is
1380 balanced and lightend
731 cam
1.5 roler rockers
flowed head with rimflowvalves (wrote down the sizes but can not find the note)
CR 1:11
45 weber
123 ignition

The weber specs are
idle: 45F9
air corrector: 185
emulsiontube: F16
main jet: 140
starterjet: 85F9
starterjet holder: 150
accelerator pump jet: 40
venturi inner diameter: 37mm
choke: 30

Especialy the choke size confuses me

Yes it will eventualy be setup on a roling road but i want a good starting point and not waste time on the rolers.

So for now anny tips?

Daniels book gives a starting point but maybe you can give a more specified advice
Onno Könemann

Using the MGCC midget register website
under modifications here http://starturl.com/mzefi

I would choose the following:

Main venturi 34mm
Main jet 140
Air corrector 190
Emulsion tube F15
idle jet 50 F9

Bob Turbo Midget England

I can recommend this book, it has a good section in the back on common setting up problems.

http://www.amazon.co.uk/Build-Power-Dellorto-Carburettors-Speedpro/dp/1903706750
Brad 1380

Of course i have Des Hammills book.

And looking carefully through it it seems i have a delorto auxiliary venturi fitted in my weber?!

Bob
In the exploded view i only see the auxiliary venturri and a choke.
Do you mean the choke with main venturie?
Onno Könemann

If you don't want the Dellorto bit i'll give it a good home :-)
Brad 1380

onno a 30mm choke isn't that unusual, my 45 also has them.
can't say what the rest of my setup is, cause i'm in france at the moment. but i don't have to tell you that the smaller chokes give more low rev torque.
Alex G Matla

Alex
Thought you had 32 chokes
And you are running SU's now ;)
Do know about the size torque relation but to small wil not increase torque.
so want to try something bigger

At this moment i have these chokes fitted (generic pic)



Onno Könemann

and on the exploded view of the 45 in Hammills book look more like this


Onno Könemann

the su's are temp. weber returning soon. with bigger chokes btw. i already have a wish list ready for the new set up. need some credits though to go to a rr session.
Alex G Matla

Pep needs to go to.
We could make it an combined effort and try to get a nice price.
3 simmulair midgets should at least be fun

I took my mini to Geldermalsen and Thijs recomended them to having had good experiances
Not just going for max power but also for a good drivable torque curve.
Onno Könemann

ofcourse we should go together. when i get back i'll have to put the engine back in first. and then get the credits, the kind a married man needs to play ;)
Alex G Matla

Sorry Onno that is a little confusing, I call the choke size the main venturi. It is what governs the size of the throat. The auxiliary venturi is in actual fact the jet pipe and is a fixed size.

Not sure what you have fitted in your weber but as you say could be a dellorto part.

Ł4mm is quite a big choke and is good for a 1380 up to about 8000 rpm, is that in your range? :)

What must be remembered on a weber is that everything MUST be balanced to the venturi/choke size. This governs the airspeed through the throat of the carb and therefore the effective suction on the jet. Thus a smaller venturi/choke causes more suction and therefore a much smaller jet is required for the same air flow.
Robert (Bob) Midget Turbo

Thanks Bob
That clears it up
looking further (shops for weber parts) it seems it is a weber part but may be different due to the fact of my weber being the later spanish built.

34 might be a bit big with the 731 cam running out of steam around 7200rpm
But i think i kind of get the balance between choke and jets.
I'll go and get some parts and try to get a more logical starting point.

Alex
some where in september should be good then ;)
Onno Könemann

No, I don't think it clears it up at all.

The photos show auxillary venturis.

I'm not sure what Robert(Bob) means by the aux venturi being the jet pipe?

If you are running a 45, I would have thought that the choke (main venturi) - I agree with Robert(Bob) on that one - would be either 34, 36 or 38 depending on engine spec and characteristics required. Smaller for low-down torque and larger for top-end BHP.

I'm not certain without going down to the garage and having a look, but the photos you show could be the Dellorto and Weber aux venturis, in that order, hence the differences.

The guy that used to do my cylinder heads - the late Les Ryder - reckoned that Webers worked better with Dellorto chokes fitted.

If you want to get it set up on a RR, try Ton Blankespoor - http://www.tonblankespoor.nl/ - a Sprite racer.
Dave O'Neill 2

if i'm not mistaking, the 2nd pic is the choke, wich has a seperate venturi of 30mm orso and is weber. the 1st pic looks like an all in one dellorto ?
Alex G Matla

i have the 1st pic but if it works itls fine by me

Ton Blankespoor dous not have a RR if i am correct.
The one i was reffering to has done lots of A-series engines so that won't be a problem
Onno Könemann

do you have two pieces to put in one barrel or just the one in the pic? not inluding the stacks.
Alex G Matla

Alex - thread theft going on - leaflets - do you still have them??????
rachmacb

yes rach, they're in the mgwokshop and i've put one in every midget that i see there
Alex G Matla

i have the choke (stuck in ther have to make a puller)and the the auxilery venturi which is one big thing.
the rampipe fits between the venturi and the barel.
Onno Könemann

Hope to have some left over for Spridget weekend - but, if not - can some go there too?

What's the big long bridge like?
rachmacb

Onno

Ton certainly did have a RR when I last spoke to him...although his neighbours aren't too keen on it, I believe!
Dave O'Neill 2

rach, do you mean the "afsluitdijk"? it would be nice without the speedlimit, now it's just a long straight road.

on the flyers, if you want i could have postman pat bring some over there.
or arie.
Alex G Matla

LOL - if postman pat is going - then great, but, otherwise, if I have none left by then, then Arie please. I hope to get some from somewhere though, so, I'll give you a shout before then - or, will I pass the MG Workshop on the way?

I'm thinking which way to go across the country - and up via Friesland is first choice at the moment! Speedlimits are a fact of life I suppose now :(

If I had time to join you all on the RR on the Monday though .........
rachmacb

Alex - I have been thinking - I gather that Gary has thousands of flyers left, so, I will get someone to collect from him (or I will if I go to the Ace next week) and bring some of them - better to leave the ones you had in the MG workshop. If you need more, let me know and I'll get some more to you some how. (well, probably via Arie, since neither you or Onno are going to the weekend now, and assuming that he doesn't mind too much ...!)
rachmacb

rach
the workshop's adres is
havenstraat 44A
monster

use that in google maps and you can plan how you fit them in your trip.

might be able to see some of the weekend but a bit unsure as work seems to come in tidle waves now
Nothing......enormous amount of work.........nothing

might not know until the week before.

but i still have to realy read your mail and reply...

ordered the weber bits today
including full radius rampipes to replace my std weber thingy's.
the MED DCR kit was a bit to expensive....
http://www.med-engineering.co.uk/product_details.php?p_id=193&vlang_id=237

and made a plot with the dynolicious app
http://www.dynolicious.com/
only half throtle til 4500rpm corners so not realy optimum.....
made 54 rear wheel bhp
might try a real run later this week without all the other trafic....
Onno Könemann

Onno, what size chokes did you order 32mm?
Robert (Bob) Midget Turbo

nah eventualy did go for the 34's
will see how it works.
Can always go and get some more.
or just trade with the RR guy's

Dave
that must be the reason he does not advertise it ;)
Onno Könemann

onno, you asked for my hp via sms.
IIRC it was 82.5bhp @5000rpm rearwheel. and something like 64 flywheel. with the twin su's.
why?
Alex G Matla

I think it should be 82 flywheel and 64 rear wheel
I have an app on my iphone that can measure the BHP of your car.
Works with the weight of your car and the acceleration.
And wanted to know what gearbox loss i had to Take in to account (as most of us usualy talk about flywheel power)
Onno Könemann

LOL - there's an ap for everything (what's it called?!)
rachmacb

i'm sure about the 82.4, not so sure about the 64
Alex G Matla

rach
look at the links above
Dynolicious

Alex
you have confirmed my memory so that is a 21% gearbox loss then
Onno Könemann

wooohoooo - that's me sitting in the car with the iPhone for the rest of the year then ...! Perhaps, while I have a "willing participant" sitting in Primerose, I can get them to help :) Not like the Dutch countryside is that pretty eh? ;)!!!!!!

Alex - are you going to be able to meet at the workshop on the Monday morning also?
rachmacb

I think the first photo from Onno is an aux vent from a 40DCOE and the second picture is an aux vent from a 45DCOE. The aux vent is very different on the 40 to the 45.
Daniel Thirteen-Twelve

I agree Daniel that was a very good spot, well done
Robert (Bob) Midget Turbo

Then how does it fit in a 45?
For as far as i have been able to check it looks like a 45 delorto venturi.

Added to that the inner diameter was 37mm so fitting that in a 40mm carb would be a bit tight (1.5mm material)
certainly when considering the rampipe slides in around that.
When you assume a 45 mm bore you have 4mm for the rampipe and venturi in thickness.
That is more inkeeping with the scale bore/wallthickness on the pic.

well the parts will arrive soon then i will pull it appart again and take pictures
Onno Könemann

I don't have any Dellorto parts to check but if the Aux vent you have is from a Dellorto it appears to be from a 40 rather than a 45.

I have a 40 DCOE aux vent with an OD of 42.92mm and ID of 36.80 at the thick end and 39.77 at the thin end.

I have a 45 DCOE aux vent that was hard to measure accurately as it has some ovality but let's say OD of 48mm.

I think you will find measuring the OD of the main venturi or choke will help size the carb.
Daniel Thirteen-Twelve

Wel F*CKN H#LL!!!
it's a 40!!!!!!!

There is a linkage on there that covers the complete top cover so the type could not be seen.

The car has been sold to me as with a 45 i have a bill from the po from the shop that fitted and setit up on the RR saying 45 weber!

so me and the PO have been fooled.


Now see if i can cancel those parts....

And start looking for a 45.
Onno Könemann

Onno, heard from Pep yesterday of your little mix up.
Where you able to cancel your order?
Otherwise I might be intersted, just to help, you know :)
Alex G Matla

Rach, around what time will you be at the workshop then? On the 6th of september I presume?
I'm going into the nightshift then, so I can (will) be there.
Alex G Matla

Alex - what time suits? Plans at the moment are to stay in Leiden over Sunday night, so, if it's a hotel, then, we don't have to pack up too much ...! Arie and Onno both have my e-mail address if that's easier? Feedtime at the zoo is calling - loudly
rachmacb

Well, I don't have to get to a boat, so whenever you're there.

Watch out for your hands..
Alex G Matla

LOL - 8 fingers - 2 thumbs all present and correct - and very wet ....!

Talking of which - any idea what the weather's going to be like so I don't have to pack two lots of clothes!

We're on the 2.30 ferry, so, fairly free and flexible, hopefully might make a few more plans over the weekend - and things will be a tad more organised, but, I'm in a "I hate being organised mood" at the moment :)
rachmacb

Well, I'm no weather forecaster, but coming week seems to stay rainy and everything that falls now can't fall again :)
Alex G Matla

That's an interesting view on life - and I'd like to disagree - after all - one can always put jeans back up!

I'm relying on the fact that all the past photos are in lovely weather, and no raincoats - so - t-shirts it is :)
rachmacb

"I'm relying on the fact that all the past photos are in lovely weather, and no raincoats - so - t-shirts it is :)"

Or people just don't take pictures when it's raining....
To be on the safe side I would bring earplugs with you just in case the rain falls that hard it will wake you up at night, just like last year.

But somewhere I have a feeling that we will have nice weather in september.

Pascal


pjw Seezink

Oi, thats me backing up!
Alex G Matla

Arie realy needs to change his ugly late style rearlamp lenses. Dont you think?
Bas Timmermans

LOL - thanks Pascal - that's made my day, as I have not managed to get my new doors, so, there's a slight gap ...!

Also, what close parking - here's how we do it :)


rachmacb

Alex
canceled the parts and going to keep the 40 for now
the injection plans might get put un to action a bit faster......

Pissed about something else now
Got 2 123 ignitions last year
And now they have introduced a new one which is programable with a usb connection!!!

Got to get in contact with them an see if i can do a deal to switch one.
They only have a fax number?!??!
Realy feel screwed a bit
Onno Könemann

Onno, don't be upset about progression!

"If progression is inevitable, why pursue it?"
Alex G Matla

sure i can under stand but they have realy have to get in to this millenium and have an e-mail adres!!!!
And since i contributed to nearly 600 Euro of their income i can only hope the have some feel for customer service and offer a good trade in deal
Onno Könemann

I can understand why they have built a USB programmable one as their original one is hardly programmable in situ. It was the only thing I found to be a dissapointment with mine. Why did they put the adjustment screw on the underneath?
Gary lazarus

Yeah that is realy a piece of bad ergonomics
Onno Könemann

This thread was discussed between 01/08/2010 and 20/08/2010

MG Midget and Sprite Technical index

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