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MG Midget and Sprite Technical - Fabricating an inlet manifold

I need to make a new inlet manifold for my next modification, does anyone know what the min bend radius is for 1 1/2" s/s tubing?
I think i'm going to need two S shaped inlets & would like to know how much space to allow for them.

cheers
Brad
Brad (Sprite IV 1380)

Brad,

That really depends on the equipment you have. Mandrel bending is best and requires the most kit. IIRC about 3 * tube OD as centre line radius is around the common minimum. I've seen these guys on ebay and they seem to do various http://myworld.ebay.co.uk/solid-fab/ . No connection, just bookmarked them as they looked useful.

BTW the last manifold I made was hammer formed from 14 swg steel in an upper and lower piece and welded together.
David Billington

Interesting eay shop that, could be quite useful.
I don't have any suitable gauage pipe bending equipment so would have to get someone to fab that part for me. I'm off on my travels again soon, so will be checking out the local machine shops as usual.
Brad (Sprite IV 1380)

Hey Brad

Are you wanting to make a maniflow intake (see pic below)...the angle is 20 degrees. Most of the parts from the HS2s and HS4s are interchangeable, So you can use the HS2 linkage to connect the 2 HS4s...that will help you figure the distance between the 2 and will place you dead on on the CH intake holes.

I have to say, I tried many times to make the maniflow intake, but failed each time...It looks simple, but unless you have experiance with a welder and percision cutting tools...its a freak.

I ended up making an intake out of a MGB intake from around 1967...Obviously I havent used it yet, but Im vary happy with the outcome

I never could muster the nerve to pay the $400 bucks they want for the maniflow intake for the equivelant on 1 foot of steel tubing, 8sq inches of flat stock and 15 minutes to gigg it and weld it

Prop


Prop

No Prop,
i want to get the red thing bolted to the big ali thing.



Brad (Sprite IV 1380)

Brad,

Oh WOW,

Your doing a super-charger, vary cool...Is that from the BMW mini cooper.

I wonder if you cant order an intake from mossmotors for the super charger after all they sell a kit.

Another way, get a intake for a single SU HS6 carb and make an adapter plate to fit on the super charger out put hole inorder to connect the 2 mounts.......or get the duel log type intake and mod up a new SC plate to fit the 2 intake holes on the SU intake manifold, infact maybe even get a MGB log type intake and mod that up to fit, it would be bigger and diliver more air and be better balanced then the 1275 log type

Just some fast thoughts

Btw there is a supercharger section on this website towards the lower end of the list, those guys know there stuff...its worth a chat with them

Prop
Prop

Hi, I found this on Ebay, not had any dealings with the seller so can't vouch for quality.

Not sure if he would sell items seperatly.

http://tinyurl.com/ncksaw

Mark
Mark Whitmore

The problem with the mini ones is they are a sit on type & need a bonnet bulge for the Spridget, i can do better than that & far cheaper than Moss.
The only feature i can see on the Moss one that is nice is the blow off valve, i purchased one from the blower shop in the states for $25.00 plus shipping. My Eaton is the teflon coated later verson with delivery on it, an ebay bagain at £87.00.
I was going to make an adapter plate for the ERA Mini turbo inlet i have, but the bolt alignment just doesn't work out & i'm not keen on welding to that grade of ali; so i'm going to design an inlet from scratch.
I've had a few hours in the garage away from cutting fields & reckon i can get the SC to sit in less space than the present 7" Longman intake & 45DHLA set up though fitting a twin choke to the inlet is going to be interesting.
I have most of the bits now, MegaJolt ECU all built & tested, Innovate wideband, MED supercharger pulley, ported Metro turbo head, just need a tensioner pulley which i'm sure won't be difficult.
Brad (Sprite IV 1380)

Well to answer my own question 2D measured from the tubing centre line, seems to be the tightest curve available. Luckily this just falls inbetween the C/L of the inlets.
Brad (Sprite IV 1380)

Anyone see a problem with this manifold design?


Brad (Sprite IV 1380)

With forced induction, you can get away with some real odd ball shapes and designs. However, you do need to worry about cracking.

If you could do a double feed to the U-shape, then I think it might be more feasible.
Trevor Jessie

Trevor,
the problem with a double feed is hitting the sweet spot on the SC, internally it has a vee which channels the output, which is where i put the outlet. Maybe i could put some fillet welds in to help prevent cracking.

cheers
Brad
Brad (Sprite IV 1380)

A couple of issues i see...(agian its forced as treavor says) .

I think you will need a balance tube at the top of the U before going into the head...obviouse reason is to balance out the flow to the 2 seprate ends.

next i would stair step the U tube to the head (reversions), that way flow cant back up on you going.... smaller to larger, (may not be an issue))

Id weld a devider in the small piece that connects to the U tube...that way you can split the flow, and not rish one side getting a lot and the othere side a nominal amount

I still dont see why a single carb intake manifold wouldnt work

Prop
Prop

here are a few articals that might be of help...they arnt going to answer the problems but might provide insight

http://www.sdsefi.com/techheader.htm

http://www.sdsefi.com/techinta.htm (building an intake header)

infact this whole site is vary good... http://www.sdsefi.com/


Prop
Prop

Thanks for the links.
I don't think the extra length of one of the inlets is going to create an imbalance, though i will see what i can do to strengthen it all up & change the feed to the u-bend.
Brad (Sprite IV 1380)

Does this look better, it has some stiffeners on the bottom of the u-tube.


Brad (Sprite IV 1380)

I'm not familiar with the "sweetspot" for the feed, but using my elementary logic it seems like you are creating a bottle neck. I know pressure and velocity will vary indirectly and all that physics crap, but for the sake of keeping the fuel atomized and at a stable temp... I would want the cross area of the tube feeding the U-shape to be at least as large as the sum of the cross area of both inlet ports.
Trevor Jessie

That actually sounds reasonable, i'll see what i can do tomorrow, it's late o'clock here now,

cheers
Brad
Brad (Sprite IV 1380)

Why would it need a balance pipe Prop?

Isn't the "u" bend one Big "F" balance pipe? or am I missing something?
Robert (Bob) Midget Turbo

to be most effective the balance pipe needs to be as short as possible
David (davidDOTsmithAT stonesDOTcom)

Hey Robert and Brad,

Im certianly no thermo dynamics airflow engineer...But the main issue i see and I think even treavor is hitting on indirectly...Agian I dont know the terminologie

But what I see happening is one side of the U bend out let will get alot of atomised fuel airflow, and the otherside not so much-to vary little...an inbalance of sorts...does that make any scence

to put the question at a grade school level...How will the flow know which side of the U=bend to go up ...the right side or the left side...granted if one pipe is a bit shorter of has a degree or 2 more bend thus creating a faster short side (AKA air plane wing profile) then the airflow will choose that side rather then the other side

So if you have a balance pipe at the top of the U-bend to connect the 2 sides back togather agian...you would have even pressure and flow on both sides

BUT...Thats Airflow, Being that this is a supercharger and where talking pressure and vacume... I maybe completely wet in hog snot as to my thinking. and forced pressure will push the airflow into each side...making balance illrealivant as the SC is the driving force and will waant to fill any voids in the intake manifold

Prop

Prop
Prop

Prop the flow will go to which ever side of the U bend has the lowest pressure. (Whether that be 1 PSI or minus 1 PSI, a balance pipe will achieve nothing it is the same as the U bend. I think you are confusing this with the kind of instalation that has 2 INDEPENDENT inlet tracks AKA Weber.
Robert (Bob) Midget Turbo

Giving this some thought and thinking about my SC engine a couple of points come to mind.

1. If Brad's SC has an internal bybass then there will be vacuum at partial throttle
2. Since the fuel/air mixture is coming from a single inlet no balance tube should be required.
3. Although no balance tube is required I'd still want to keep the runners to the individual ports as short and even as possible.
Trevor Jessie

Why would you want them as short as possible??
What happens when you fit an intercooler between the SC and the inlet, then you end up with very long tracts with no ill effects?
Robert (Bob) Midget Turbo

The fuel is injected close to the ports if you are using an intercooler. Brad is introducing his mixture prior to the SC so consideration must be given to getting it into the chambers without have it puddle in low pressure areas caused by varied gas speed. (Think: air foil)
Trevor Jessie

WOw Robert,

Your Great, I didnt know you where a mind reader...can you do any other tricks...LOL


You are exactly correct I was thinking of "2 INDEPENDENT inlet tracks AKA Weber" As the basis of my (personal theory)...But not so much the webber, but a good example. more so the log intake and duel Sus we have on our midgets

I think once the airflow lives the single mouth and goes into the Ubend...the Ubend becomes 2 seperate tracks... agian look at #3 of treavors above comment, granted balance tube Not required i differ on.... But I have to completely agree with """I'd still want to keep the runners to the individual ports as short and even as possible.""" Short and Even being the Key words...I just think without the balance tube your going to get alot of pulsating action as the SC tries to figure out which tube to put the pressureized flow into as the cly./piston eats it up...thus creating confusion for the flow as to which side of theUbend to go down...right or left.

Agian all the above theory is from the "Mind of Prop" So its probably only worth $12.38 without S&H...LOL


prop
Prop

I guess that why I still like the idea of a single carb intake manifold.

you have the carb hooked up to the SC then the SC hooked up to a 2 in diameter interconnecting pipe with a carb mounting face attached at one end and bolted to the single carb intake manifold hole and the other end to the SC exit hole ...whola...No Ubends needed, along with the persision built into the Ubends for proper balance, there is NO wieght being applied to the intake system from the SC to form stress/heat cracks, you can bend the interconnecting pipe between the SC and the Intake manifold any way you want and the SC has many new options/angles for how its secured into place..and you can add a nitrous injector into the interconnecting pipe, so it will be fully atomised with the other fuel when it hits the cyl.

Much easier Id think,,,and no calculas/ geometery math needed along with persicion craftsmanship of cutting and welding. aka About $1000 back in your pocket not having to pay someone to do the deed.

prop
Prop

heck you could use that exhaust flexie pipe for the interconnecting pipe between the SC and the single carb intake manifold...that would make intallation super easy. Now your talking about a DIY weekend project, with just a simple welder and basic cut off wheels...No High dollar professionals needed Like in your above 1st thoughts.

Prop...I should really be getting paid for my ideas...Prop
Prop

Trev I had assumed that the carburettor was positioned before the SC and then the SC connected to the cylinder head.
Thus the SC would raise the temperature of the charge, so the intercooler would need to be positioned between the SC and the head, so causing the carburettor to be a good way off the head ports wouldn't it? Not that Brad is considering an intercooler at present. :-)

Prop, I'll tell you what lets beg to differ, you live in your universe and I will live in mine! Deal?
Robert (Bob) Midget Turbo

Bob, it is my understanding that you can not have fuel/air mixture flow over an intercooler because the fuel will condense and not be atomized well enough to have complete combustion. All "kits" that I am aware of have the fuel introduced after the intercooler...or, like mine, they have no intercooler.

I supposed if we moved this over to the supercharging forum those guys would prove me wrong. ;)
Trevor Jessie

Seems sound advice Trev I fortunately have a "blow through Turbo and carb so my intercooler is before the carb. Modern vehicle as you ay are direct fuel injection so no problems so in this example I wonder how good an intercooler would be on the inlet to the carb and SC?
Robert (Bob) Midget Turbo

A cooler before the SC? Have you teleported over to Prop's universe? ;)

Until the air is compressed, there is little energy(heat) to be removed.
Trevor Jessie

No not yet fortunately just thought that a reduction in inlet temp was better than ambient temp entering the SC, but point taken :-))
Robert (Bob) Midget Turbo

Not sure if it helps, but here you go!

http://www.peterrenn.co.uk/midget.html#supercharger

David Hunt

Prop,
'wet in hog snot'!!! what a marvelous expression.

I did originally plan to bolt the SC direct to an inlet manifold which is why you can see a ERA turbo one in the picture, but the bolt spacing & SC lateral offset didn't really work out.

Trevor,
the SC forum is a bit on the quiet side, mostly used by B owners who have half an acre spare space under their bonnets.

cheers
Brad
Brad (Sprite IV 1380)

I got ya now brad...thats why,

Prop...back to the showers...Prop
Prop

This thread was discussed between 07/08/2009 and 18/08/2009

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