donut
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| posted on 27/1/03 at 05:27 PM |
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twin 40's or keep downdraft?
I have been offered a pair of twin 40 weber 's for my standard 2 litre pinto. How much better will they be as aposed to the standard down draft carb?
How much more bhp can i expect?
Cheers
Andy
Andy
When I die, I want to go peacefully like my Grandfather did, in his sleep -- not screaming, like the passengers in his car.
http://www.flickr.com/photos/andywest1/
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Deckman001
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| posted on 27/1/03 at 06:41 PM |
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saw on a different post some one recomending 45's or 48's
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Mark H
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| posted on 27/1/03 at 07:12 PM |
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Certainly look/sound better!
Would I be right in thinking that it'd also be lower than the downdraft.
Elsewhere there is debates over weber v choke size. DV Andrews website seems to be the font of all knowledge on the subject (i'll find the link if
you want, but I'm sure someone else will have it to hand) - even I could understand the principles.
Mark
Mark Harrison and
Q986 KCP back from the dead...
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donut
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| posted on 27/1/03 at 07:17 PM |
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Good point there boss, I'm gonna stick with standard i think and sell the 40's for my friend.
Another thing i have been told is that it's damn hard to get through sva with twins for emissions!!!
[Edited on 27/1/03 by donut]
Andy
When I die, I want to go peacefully like my Grandfather did, in his sleep -- not screaming, like the passengers in his car.
http://www.flickr.com/photos/andywest1/
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geoff shep
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| posted on 27/1/03 at 08:06 PM |
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What sort of price is this friend after? and are they on a pinto manifold?
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donut
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| posted on 27/1/03 at 08:28 PM |
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I'll find out. He thinks they're on a ford manifold but not certain. They come with linkages and trumpets.
When i find out i'll pop them on the for sale section but drop me an email and i'll give you 1st dibs, i'll even try and get a few photo's. Email
me at andy@donut.co.uk
cheers
Andy
Andy
When I die, I want to go peacefully like my Grandfather did, in his sleep -- not screaming, like the passengers in his car.
http://www.flickr.com/photos/andywest1/
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kingr
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| posted on 28/1/03 at 11:10 AM |
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You'll need to be more specific about the manifold too, since there are different ford manifolds.
The link for DV Andrews is : http://hometown.aol.com/dvandrews/index.htm
Kingr
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Sideways 2 Victory
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| posted on 28/1/03 at 03:02 PM |
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Hi Donut,
Twin 40's theoretically enable you to add more fuel to the mix, allowing for greater timing advance, hence producing xtra power. They also do away
with all the vaccum gubbins associated with the distributor and the water pipes generally fitted to heat the inlet manifold on road cars.
I'm sure there are other benefits but there is obviously a MPG penalty to be paid for all the extra fuel the carbs are slurping.
They also look and sound fantastic and help to keep the height down, although I am using a Crossflow which is not quite as tall as the Pinto.
I asked about this before.........
See this link to the thread.
Twin 40's SVA thread
Seems doable at least. I'm going to try with the rebuilt Twin 40 Dellortos, if that fails I'll clean up the old standard Webber downdraft from my
donor and try that.
ATB
Cheers
Dave
www.nurburgring.org
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donut
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| posted on 28/1/03 at 05:18 PM |
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Thanks but i'm gonna stick with downdraft at least till after SVA.
Andy
Andy
When I die, I want to go peacefully like my Grandfather did, in his sleep -- not screaming, like the passengers in his car.
http://www.flickr.com/photos/andywest1/
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jollygreengiant
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| posted on 28/1/03 at 07:15 PM |
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You can run a std 2.0 pinto on 40's. you will not get as much of a power increase as you would using 45's, 48's or (for a real screamer using a
40/40 cam with roller followers) 50's. But 40's will run ok. As for fuel usage if they are tuned properly on a rolling road, then fuel usage should
not be too bad unless you cannot hold your right foot still. ( I used to get 30+ on a run and 20 round town). You just have to consider that a single
cylinder can only burn fuel economically on a 14:1 ratio, too much & your pocket feels it as well as performance dropping of, too little and you loose
power and burn valves. a rich idle at about 2.5% co should stop valves burning and idealy you should aim to get about the same value at about
3000/4000 rpm. The reason that most people complain of poor fuel economy is because of the accelerator pump jets. With a single carb (or even a twin
choke) you get only 1 pump of neat fuel squirted into THE engine each time you push down on the accelerator.
With twin chokes like DCOE's (& dellorto's) you get ONE SQUIRT PER BARREL which means that you use three times more fuel. To drive cheaply you need
to learn the 2 position driving technique.
Stop = foot of the loud pedal.
Go = foot on fully on the go pedal and control your speed (where ever possible) with the gear stick. and when you reach cruising speed just back of on
the loud pedal until the engine is comfortable.
Enjoy.
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kingr
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| posted on 30/1/03 at 10:15 AM |
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I believe there are approx 11 different accelerator pump arms, which will alter the ammount of fuel, and also, you can alter the size of the jet for
the accelerator pump backwash to use more or less fuel (not all the volume of the accelerator pump is used). Hate to bring you up on your maths JGG,
but 4 is four times more than 1, and besides, there's only two pumps, one per pair of barrels.
Kingr
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jollygreengiant
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| posted on 30/1/03 at 07:31 PM |
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depends on the way you look at things. One carb for four pots, one jet and only Xmax amount of fuel can be thrown down into the induction system
before you reach a flooding mass. This is because the fuel will be drawn into each cylinder proportionately dependant as to which cycle of rotation it
is on (suck, squeeze, bang or blow), BUT all the fuel gets utilised and the wastage is very negligible.
With a multi barrel carb set up as in dcoe's, yes you have one pump, BUT two accellerator jets, one in each barrel. Now fuel is not clever, it does
not know which of the one barrels of the two bodies is on the most appropriate possition to provide a pro rato ammount of fuel to. Therefore three of
the barrels are giving inapropriately large ammount of fuel to their respective cylinders. To a degree this is not a bad thing because it helps to
cool the valves down, but none the less three barrels are wasting more fuel than the other one which at that particular time is on the suck stroke.
Yes I do realise that we are talking about events that are over and done with in reguards to cylinder duration in terms of thousands of a second, but
also the waste occurs in retrospect on all cylinders as the cycle goes on.
If you would like I could start to go into the pure math side of the arguement but I think that I've already sent a few people to sleep. Most people
are only concerned with 'Does It Go' and the answer is yes but at a cost.
Oh & I did try to keep it simple.
Enjoy.
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kingr
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| posted on 31/1/03 at 11:27 AM |
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OK, your point is valid that it goes, and uses lots of fuel. Not sure to what degree the accelerator pump causes that, but not to worry. But please,
pretty please, with icing and a cherry on top, will you call it maths we've got enough Americanisation as it is.
Kingr
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Gene Rosson
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| posted on 31/1/03 at 05:55 PM |
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Webers for 2.0 Pinto
Andy asks whether the Webers will improve performance for the 2 litre Pinto.
Answer is yes, but only if competantly tuned. Dave comments, in good faith, that the Webers will furnish more fuel and allow the timing to be advanced
which will create more power. Sorry Dave , you are way out in left field here.
he Webers will allow more fuel if tuned that way. Excess fuel will destroy performance ! Excess ignition advance will not only diminish performance
it will also lead to engine destruction through detonation.
Why are the side draft carbs better ??? Because they allow a better path for air to traverse and the fuel air mixture is more likely to remain
homogenous. Homogenous mixtures burn more readily and allow ignition to be retarded somewhat. Retardation will produce more power.
How do I know all this stuff ? Graduate Mechanical engineer who frequently operates a flow bench and dynomometer. Have worked on numerous 2.0 ford
induction systems.
Incidentally four Mikuni carbs will also work very well. 40 mm bores, weber, Mikuni, Del-Orto, etc.. are entirely large enough for most uses. Larger
bores will cause lagging throttle response. I hope this info is useful Gene
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jollygreengiant
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| posted on 31/1/03 at 07:44 PM |
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quote:
Originally posted by kingr
But please, pretty please, with icing and a cherry on top, will you call it maths we've got enough Americanisation as it is.
Kingr
Oky Dokie, Sure thing boss.
Have a nice day.
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Alan B
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| posted on 1/2/03 at 04:09 AM |
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Gene,
Welcome to the forum.
I'm just a couple of hours from you near Vero Beach...I know Lakeland quite well.
Check out my site and see what I'm up to
http://www.desicodesign.com/meerkat/
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Stu16v
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| posted on 1/2/03 at 02:36 PM |
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Gene is absolutley spot on. And is the very reason why 40's are to be prefered on an otherwise standard Pinto/Crossflow etc. Bigger is not
necessarily better. Straightening the inlet path up pays dividends, but looking at the induction as a whole the next (and in most cases) the biggest
restriction is in the valve area.
To put it simply, think of it like a garden hose pipe! There is no point in having larger diameter hose, if the restriction on the end is the same
size, you just will not get any more water coming through.
Back to the engine, it then logically follows that the exhaust side becomes an issue. To get fresh mixture in, first you must get all of the spent
gases out, and so on.
And top it it all off, how often (honestly now... ) would you spend flat out? It's much better to have slightly smaller carbs, and exhaust manifold
etc (but well designed!) which will improve mid range torque and driveability no end with only minimal loss of top end power (if at all).
Big carbs do not mean big power, more often than not you end up with just a car that is a pig to drive, and bigger fuel bills, because huge carbs can
be difficult to calibrate for 'normal' driving.
HTH Stu.
[Edited on 1/2/03 by Stu16v]
Dont just build it.....make it!
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