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MG Midget and Sprite Technical - How long should a silencer last?

Around 4 years ago I fitted a Maniflow single box exhaust system. When I first fitted it I was impressed at how quiet it was despite providing a boost in performance. Over the course of this year I have become concerned that it seemed to getting much noisier than before. I am concerned that if I ever do a track day it will not pass the noise test/limits. The obvious explanation is that the silencer is not as efficient as before but I only do around 1500 miles per year. There are no external signs of decay and everything appears gas tight. How long is it reasonable to expect a silencer to last? At Spridget50 I noticed some 'repackable' silencers on sale. Anyone know the recommended interval between repacks as this would indicate the life of an effective silencer. Last time I looked a silencer from Maniflow was £80 or so, hence I'm reluctant to just try a new one on the off chance!
Chris H (1970 Midget 1275)

You havnt backfired thur the exhaust have you, that will certianly knock one out for the count.

prop
Prop

My new midget ha a repackable silencer from magic midget and was a bit loud (former owner leked the noise)
so i took one end of (allen head bolts) and stufed in some rock wool i had lying around.

5 minutes job and it sounds great but not loud and for 1quid worth of rock wool who cares how much times i have to refill (about 1000 miles since and stil quiet)
Onno Könemann

I didn't think the single box systems even had a silencer in them! Mine is phenomenally loud. Is it still in good nick? The problem I and a few others I know have found with Maniflow back boxes is that they are absolutely fantastic but they do not last, even in the rust stakes - they rust very quick.

So you might have another 'not lasting very long' symptom of it. In all fairness though, these back boxes are insanely efficient in terms of flow and you wouldn't do yourself much of a disservice by packing it out line onno says. I'm sure your car will still go as fast as ever afterwards!
Rich Amos (1 Sprite 1 Midget!)

I recently replaced my muffler with a 16 inch Coby which has an inlet of 1 3/4 inch. It gives a deeper sound than the previous muffler and I can now hear my ipod when driving. Back pressure has reduced giving some added benefits. The previous muffler was similar to RC40 and had obviously been on for a number of years. The end rusted and became thin allowing the pipe to break away and was not repairable. The Coby fits better between the tank and spring as it is round and is of heavier construction than the previous.
WD Doel

Chris,

Jetex do a range of 'Universal' silencers. All 'straight-through' design, in either aluminised or stainless steel. The two ranges that are of interest are their 1.75" and 2" bore. These are designed to go 'over' the sizes quoted, the actual entry and exit silencer tube o/d sizes are about 1/8" bigger.

Reasonably priced and seem to last well - I have two aluminised ones on our 1380 engined Minor, and they have been on the car for 10 years.

Avaliable from Demon Tweeks.

Richard
Richard Wale

"but I only do around 1500 miles per year." -
this could well be the cause of your problem; the stuff that condenses out of the exhaust gases into the silencer is very corrosive and together with normal high-humidity condensation can rot out the innards quickly. The stainless steel repackable ones use something that looks like loft insulation inside so don't rot. The repacking material is about 15 quid for a big box, some of us now use these on race cars to be able to meet different circuit regulations (no noise limit = not much filling!) Kim at MagicMidget is a good source...
David Smith

No backfires Prop. I suspect Davis S is correct - my suspicion always was that standing around leads to corrosion inside the silencer. I'll look out for the repackable ones. If they are the ones I saw at Spridget50 on the Magicmidget stand they looked enormous (like a zepplin) but I presume they fit or others would not be using them.
Chris
Chris H (1970 Midget 1275)

yes they do fit (just) 'tween spring and tank; to be on the safe side we've wrapped the front half in that asbestos-substitute manifold tape stuff.
David Smith

i can try to make a pic tomorrow it fit's fine
Onno Könemann

Maniflow made me a single heavy duty silencer unit to mount across the back as i have had problems before and it gives good clearances etc.

The pic shows the unit - its oval and fairly h/duty with bracing welded from the pipe to the silencer.

Its got a good deep sound - not too noisy - which can be a pain for longer runs.

Still fairly new so can't confirm durability yet.
I will try and getter a better pic.

Richard.


richard boobier

Now that my '72 is old enough to no longer
need a safety inspection, my silencer will
last FOREVER!

chuck
c c

My maniflow got too loud. I had one made up locally here, and that too is now too loud 12 months on. I wouldn't mind if it was just loud at the top end, but it is loud throughout the rev range. just the force of the gas escaping frightens people to death stood behind the car. Is it a comp ratio, or a high rocker ratio thing?
Shawn

This thread was discussed between 31/10/2008 and 03/11/2008

MG Midget and Sprite Technical index

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