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MG Midget and Sprite Technical - Custom inlet manifold ponderings

Long time no see folks. Hi!

Conceptually thinking, can anyone think of a downside to angling a carb away from perpendicular to the engine? For instance in the attached, mounting the carb angled at 45 degrees to the head mounting face.

Cheers,
Malcolm

Malcolm Le Chevalier

What do you want to achieve?
O K

Malcolm this one is very effective when we had a few Maestros with modded heads, very good torque and power.

You could consider an equal length manifold by bringing it from the plug side and over the rocker cover.

Peter

Peter Burgess Tuning

Malcolm

I would imagine the turbulence and resistance to flow would pose an issue in getting a uniformly stoichiometric mix to the engine and also present difficulties in setting the mix ratio and balancing the carbs.

Laminar flow as much as possible please!
Oggers

I was trying to see if I could design (and if I get bored one day, fabricate) a cross over manifold, where the runners were equal length. i.e. the two "primaries" are equal and the four "secondaries" are equal.

I used to have a x-over manifold on, but changed to a parallel type due to exhaust clearance issues. I quite liked the x-over for a variety of reasons but the unequal length runners on a "standard" x-over manifold meant fuelling to each cylinder was a bit uneven.

The angling of the carb is to try to keep things compact and avoid it clashing with the inner wing.

Another side benefit is it would angle the throats towards my cool air pipe too.

Cheers,
Malc.
Malcolm Le Chevalier

It would be afun exercise from an engineering perspective and to prove it could be done .. but it wouldnt be an easy or short term task... i

id suggest EFI on a turbo would be a better use of time and expense vs outcome

prop
Prop and the Blackhole Midget

Malcolm,

I would think that arrangement would work fairly well, a 1500 I would guess, I don't know the 1500 firing order so don't know if it gives regular or irregular pulsing. Sidedraughts on A series suffer from poor mixture distribution at idle due to the low flow and the idle ports being near the centre of the carb, a typical problem is that at idle 1 & 4 plugs leads can be removed with no apparent change in the engine but 2 & 3 being removed lead to noticeable engine speed change, doesn't seem to be a problem when the throttles are opened though.
David Billington

Oggers, the flow is turbulent at the velocities which obtain in car engines. Laminar flow is less efficient and petrol would drop out of suspension. The flow is like a cotton woolplug tumbling, twisting and turning as it goes through the engine. I seem to recall the flow can become fully developed but my physics is v rusty.
Thread I came across on the subject
http://www.physicsforums.com/threads/air-intake-design-turbulent-flow-modifications.761014/
Peter
Peter Burgess Tuning

Malcolm
DO IT
I've always thought a manifold similar for a midget /B would be good with the carb at rightangles pointing out the front with a nice cool air feed from out front of the radiator --do it---finished yet
The Harley guys here have got Webers stuck in all sorts of places, out the front--under the tank, and they seem to work great
And as Peter mentioned you could go over the top like the rotary Mazda guys do it with great results if you want some runner length
willy
William Revit

Interesting you mention the Harleys Willy.
They have a common inlet manifold so present as one pair of siamesed ports like an MGB to my mind. We tend to find they are power restricted the same as the B too! We did lots of development on a 1950 Vee twin. It seemed to us the way forward was separate inlet manifolds and single carb barrel per port. Almost impossible to achieve because of the closeness of the two heads,but a Japanese guy rotated the front cylinder head so he now has two carbs and inlet runners and loadsa power!
Here is a link to a Back Street Heroes article about one of the Harleys we have worked on.
http://www.peter-burgess.com/PDF/BackStreetHeroes.pdf

Peter
Peter Burgess Tuning

One of the Dellortos I fitted to my Sprite had previously been fitted to a HD and the owner said the power increase was enough to scare him so he took it off and put the original back on.
David Billington

I am quite tempted to do it at some point. Just for the fun of it. One thing I need to find is someone that can do nice mandrel bent tubes.

Yeah it's a 1500 btw, for those unsure. Hence the four inlet runners. And typical firing order of 1-3-4-2, so one carb barrel feeds 1 and 4, the other 3 and 2. So the pulses are more evenly spread (It in theory means you can use a smaller DCOE 40).

Cheers all.
Malcolm
Malcolm Le Chevalier

Malcolm,

It may be worth considering standard off the shelf weldable pipe fittings such as http://www.nero.co.uk/Catalogue/Butt-Weld-Fittings-Schedule-10S-316L to keep the cost down compared with custom bends. Those are stainless steel but I've seen the same sort of thing in steel just need to find a supplier.
David Billington

Before you mount thst to the engine ....maybe bolt it to a flow bench.... a cold winter friday at peter burguss shop would unload huge buckets of data on a flow bench

or look up an old car craft magizine on how to make your own flow bench ...i want to say it was a 3 part series....crude but doable

.
Prop and the Blackhole Midget

This thread was discussed between 10/11/2016 and 11/11/2016

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