MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - Maniflow LCB conclusion

Gentlemen
The past winter I bought a Maniflow LM031 manifold. At first I was somewhat dissatisfied, since it wasn't a plug and play fit. It did hit the bottom frame rail and we had to heat it and bend the downtubes just a little. With that sorted out and with the manifold fitted, the carburettor heat shield hit the middle tube, so I had to cut out a little area in the shield.
With that said, it has transformed, not only the exhaust note, but the engine is much, much more happy. And that is all over the rev. range. More bottom, more middle and not at least top end, it's so much more rev. willing up, and (just a little) into the yellow range.
So, all the extra work when fitting is absolutely worth it
Jan Kruber

Hi,

Thank Jan for the feedback ! I start to wonder if I will not change mine, taking into consideration your feedback and Malcolm on another topic. You both look really happy !

I am somehow surprise that this change lead to so much improvement to an atmospheric engine... Is the original design so poor ? In term of flow ?
CH Hamon

Malcolm did the INLET manifold, and on 1500. It is here : https://mg-cars.org.uk/cgi-bin/or17?runprog=mgbbs&mode=thread&access=&subject=110&source=T&thread=2019032610202314873

Sorry to pollute your topic Jan ! Manifold topics look interesting to me lately... :P
CH Hamon

Jan,
thanks for reporting back and great to hear of your success and enjoyment.
Nigel Atkins

Most racers use Maniflow manifolds. IMO the best that are available.
Dave O'Neill 2

My midget came with a LCB fitted but like the carbs it never looked like it was the best to me and when I swapped to a Maniflow it was found that a couple of the openings on the previous exhaust slightly closed off the engine openings. so not all LCBs are equal (in more ways than one).

The LCB can also help to liberate other tuning, upgrades, improvements (such as regular full servicing, maintenance and repairs).

Nigel Atkins

Sorry Cedric forgot your question - I'm not sure the factory manifold is that poor just that at the time the cars were new BL considerations would be as required for new road going cars in everyday use relative to the competitors vehicles, regulations, customer expectations and of course cost.
Nigel Atkins

Are they officially road legal ? Tolerated ? More noisy ?

I am not really into transforming my Midget into a performance car, but improving air flow for better torque and sound at the same time as allowing the engine to breath better make sense to me :)
CH Hamon

You are obviously thinking of this information for a year's time after you've used your Midget on reasonable length journeys regularly throughout the whole year through the different weather seasons and traffic conditions, when you've got to know your car and have fully serviced, maintained and repaired it.

They are road legal, there are not noisy as such as they are only the first part of the exhaust system, what follows them accounts for the exhaust being noisy.

Do not overestimate the effect or gain of the exhaust manifold in isolation. The sound and performance is dependent on what is before and after it, the induction and general engine condition and set up and the exhaust pipe and box(es).

A friend of my wife's had a MGB with a new sports exhaust that would set off car alarms at unbelievable distances whilst I knew a local club member with the same model of MGB with the same and new sports exhaust which was quite quiet but sounded correct and certainly would not set of car alarms even if next to them. Guess which car was better serviced, maintained and repaired.

Neither were my car, one was owned by a fully qualified engineer the other by a person that at the time made the molds for model vehicles to sell for production runs, I leave you to guess who had the very noisy exhaust.
Nigel Atkins

Cedric
I now know why the Spridget people praise the LCB manifolds and consider them to be a "must fit".
Dont worry about noise. I have the same two silencers on as last year. A "Cherry Bomb" to take the top and a stock single silencer. The difference is, that the exhaust just sound awesome, compareable withan MGB.
Again, I'm amazed by the increase in performance, it could be 10% at least.
Just wait, someone will tell us....
Jan Kruber

Nigel, do you mean I put the exhaust before the intake, the cart before the horse ? :) I agree... still learning how to read in my car's mood !

Jan, did you take a "Classic" or "Stage 2" ?
From pictures, hard to tell the difference, except price :)
https://www.maniflow.co.uk/index.php?view=category&category=169

Do you plan to upgrade the intake too ? Or already did it ? If you can now breathe out better, you are ready to breathe in greater ;)

CH Hamon

Cedric, you are better than me with your English, I could not remember the saying, yes cart before horse, your car has only just progressed from being pushed to running. :)
Nigel Atkins

Cedric,
I bought the LM031 at £159.50.
I chose the LM031 because the engine is stock, no gasflowing or other improvements done so far. But you never know, right. I believe I have read somewhere that the LM031 can handle up to 100 HP, someone will correct me if I remember wrong.
Jan Kruber

It's not a question of poor flow characteristics, there won't be much flow difference between the two. The all-into-one nature of the std manifold is the culprit, as it allows exhaust gas from a just-opened valve to backwash into an adjacent cylinder in which the exact valve is about to close. The result is a lot of residual exhaust gas trapped in the combustion chamber, and this reduces the amount of fresh charge which can be drawn in.
This reduces the effective capacity of the engine.

By separating cylinders that could have exhaust valves open at the same time this effect is eliminated. This is why an LCB works so much better.
Paul Walbran

The MGB was one of the first production cars to adopt this principle as standard, now virtually every car has it as it's such a simple way of improving output.

It is also one that gives excellent gains at low speeds, where the backwash effect is more significant. It is even more so once a lot ger duration camshaft is fitted. One owner I know once fitted a fast road cam into a midget with a std manifold and it was well slower than before! Until fitting an LCB.

Paul Walbran

Yes but would it be at least 10% increase in performance with stock engine, no gasflowing or other improvements, 5/6 hp increase - is Jan correct/optimistic or am I wrong/pessimistic?
Nigel Atkins

Hi Jan,
Thanks for feedback. They do look pretty similar, so not easy to understand the difference in price at first look... Maybe diameter or material ? But for touring, the first one would be more than enough !

Hi Paul,
Thanks for sharing, it makes sense. One question come to my mind after your explanation : what about cylinder 2 and 3, as they share the pipe (if I am correct) ?
CH Hamon

Cedric if my figuring on my fingers is correct it doesn't matter because when #2 is on the exhaust stroke #3 is on compression with the valves closed, so #3 cylinder is not exposed to exhaust gas from #2.
If that makes sense.
Greybeard

Nigel, the 10% is just a wild guess.
Some people told me, that removing the belt driven pulley fan and replace it with an electric fan will increase power with one horsepower, I don't know if that is correct..
If it is, hooray, I have one horse power more.
But the amazing transformtion of the engine's behaviour feels certainly like more than this single HP.
I was very sceptic when fitting the LCB manifold, I mainly fitted it because it looks cool. But the noticeable different really has surpriced me.
If I were ever to take over another Midget 1275, the first thing to do, was to fit an LCB, period! basta! ponc!
:)
Jan Kruber

Nigel, yes it does make that much difference at lower speeds in particular. So while you might not see 10% in peak nap I would expect to find it in the lower speed torque.
An example of what excessive residual exhaust gas can do: my wife has a (one owner) original Fiat 500. Now 650 :-). After the 650 effort I was disappointed. So I biffed the std exhaust and made up a proper extractor. Result was that everything went up a gear: 2nd gear hills became 3rd gear hills, 3rd gear hills became Top Gear hills. And people who pullede out to pass it on the long 1 in 10-ish hill near home were left behind in the
Paul Walbran

Good news then. I was just a bit surprised at how much by itself but I've never read Daniel's or any other tuning book.

If there was a 1hp gain when I removed the engine driven fan then most of it is probably lost when the electric fan cuts in as that seems to make the uprated alternator work up a sweat causing a bit of drag to the engine, luckily the cooling fan is only normally running when the car is going slower.

When I went from not so good LCB to good LCB I noticed a bit more openness especially at higher speeds.

Nigel Atkins

Maybe it was the first car fitted with (passive) EGR ? :)

"If that makes sense. "
Yep, it does, thanks Greybeard :)
CH Hamon

This thread was discussed between 01/05/2019 and 03/05/2019

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.