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MG Midget and Sprite Technical - Exhaust Silencers and Noise

Hey folks, hope everyone is well and enjoying driving season.

Just pondering on exhausts, as you do. My car has the standard two box system with the short round box, followed by a larger square-ish box across the back.

Would deleting the first box (whilst simultaneously upping the bore to 1 5/8 or 1 3/4) leave me deaf and miserable?

I see Maniflow offer one or two box systems, but with no real info on the pros/cons of either.

Also remember I am only 28 (for the rest of today at least) and like Radio 1, so I am probably more noise tolerant than the average MG driver! :-D

Cheers,
Malcolm
Malcolm Le Chevalier

Malcolm, I've been looking in the archive as mine may need doing and someone said they had put a 1275 back box on in place of the 1500 two boxes and it was OK. Just wondering myself about pipe sizes for 1275 matching 1500?

The archive was from about 2006 ish.

BTW life ends at 30 so enjoy it while you can :-)
Dave Squire

And from previous thread on this page just noticed:

Paul Walbran, New Zealand

We use GEX3429 rear silencer MGB on our A series midgets and find it a nice balance between tone and not too loud.

Both ideas much cheaper than standard and no heavy back box! Its about pipe sizes methinks.
Dave Squire

Malcolm,

I'm 53, but quite tolerant to exhaust noise, or perhaps I'm going deaf from 30 odd years of loud bikes and cars. I'll not get into the earplugs debate...

My 1360 runs 10.2:1 compression, which has a bit of an effect on noise. My car runs a Maniflow LM031 SII and the matching single box system. I had it ceramic coated.

Its quite loud, but deep, not buzzy. I think that's partly down to the heavy, mild steel construction.
You can definitely hear it cruising on the motorway in 5th gear, but its not too intrusive. No more so than the wind noise etc anyway.

Its not at the Saxo/106 boy race level.

Hope that helps.

Mark
M Crossley

Malcolm

I too had a similar twin back box and have recently fitted a Maniflow 1 5/8 straight through - the one with the large single cylindrical back box with the tailpipe exiting at the nearside. Bought it direct from Maniflow - other suppliers are available of course - but the Maniflow chap was very helpful and it came with hangars and clamps. IRRC the manifold end is flared and it fitted over my LCB outlet and clamped up. I too was thinking of the 1 3/4, but as the LCB was the restriction, I did not see much point. Do measure up the outlet OD of your manifold to determine what is best for you though. I believe the thinking is to fit any long tubular pipe down the chassis over the existing manifold or at least use a sleeve so as not to cause any restriction to flow. The idea is to remove the exhaust gases with as little turbulence as possible.

Paintwork is a bit flaky, but it seems well made. Had to do a bit of fiddling about at the rear as it is a tight fit. Fuel tank and rear springs constrain matters. I ended up drilling the boot floor to fit an extra hanger. Not a big deal, but the back box is heavy and again IMHO requires support at each end of it. Nice chrome effect tailpipe.

Whilst the volume is somewhat louder, it is not particularly intrusive. The tone is more mellifluous, deeper and sounds more like a sports car. Seems to bring a wee bit more response in so far as a greater willingness to rev, and possibly brings a tad more bhp to the party.
Oggers

Rules and regulations aside

there probably wont be any noticeable differance from 5/8 to 3/4 ...its a 1/16ths inch is all... you have a 90 degree turn at the manifold so theres your real detractor ... if your engine was a fine tuned master piece of art and performance where every gram of HP had to be found then that 1/16th of an inch differance will come into play

because your an irresponsible kid living a life of only 2 % responsiablity and not a refined elegant sophisticated mature gentleman with a vast supply dejore mustard and old spice deoderant

id recommend a cherry bomb exhaust ... very similar to what oggeer discribes above... thats what i have it has a great rev sound like F1 and it is somewhat loud .. but im not driving 300 mes at a time

Put it is loud enough that i got neighbors complaining to replace my muffler and it does give the copw pause as to weather they want to say hello... so far not yet

but if your going to drive a race car it should sound like a race car is my personal opinion

but the less restriction and less turbulance without being to big dia is the way to go...and connections should be narrow to large from the engine to the tail pipe tip ... small dia spilling into larger dia connections ... other wise the gas flow gets caught on to the lip if you go larger to small

prop

prop

Sounds like you have a real weeney exhaust system Prop ! ;-D
Guyw

1380 with an 45mm RC40 rearbox sounds just fine.
Not tyring for the long drives but noisy enough to be fun.
Iirc the maniflow is just a bit louder
Onno K

Hmmm, hadn't considered just doing straight out and doing away with the cross-box. Good shout.

The impression I am getting is whatever I do, it's not going to be *that* loud anyway. Good to know.
Malcolm Le Chevalier

I have the Maniflow single large across the back box + manifold, it helps as it does not interfere with the springs/tank.

Gives a good sound, but not too loud on longer trips - mine is getting a bit old now and I am thinking of replacing with a similar system in stainless - not sure if that will be a bit noiser.

R.


richard boobier

Malcolm, I replaced the 'across the back' system on my 1275 with a straight through Maniflow single silencer a couple of years ago. It's a larger bore but not the largest - bought from Magic Midget. Although I don't think it affected the overall performance much, it sounds silly but it just seems more relaxed! It seems to pick up more willingly and makes a deeper, more throaty sound without being much, if any, louder.

I recently replaced the leaky LCB manifold of uncertain make with a proper Maniflow one and it has improved things a bit further.

The Sprite gest sound-checked regularly and always gives 90dB +/- 2dB, so not too loud at all. I'm rather older than you and partially deaf but it sounds equally good with and without hearing aids (with the aids I just hear all the other squeaks and rattles!). My son, however, is close to your age and a Music teacher - he loves the way it sounds. To the two of us, tuning the Sprite takes on a different meaning. :)

Cheers

Colin
Colin Mee

I have an early Maniflow with a single box on my 1275 frog. Its 99dB and can bark a bit at about 3500-4000 rpm but hums in a mellow way below that and wind noise drowns it out above that so I have sort of got used to it. Doesn't really bother me on long runs.
Bob Beaumont

Prop

The difference between 5/8 and 3/4 is 1/8, which is actually an increase in cross-sectional area of 44%.

What Malcolm actually said was 1-5/8 and 1-3/4. The difference there is only 16%, but still a significant amount.
Dave O'Neill 2

Single box RC40 and 1 3/4 pipe gives between 92 and 94 dB on the back of my K series car. They are cheap, fit between the spring and tank, just, and sound nice. Car makes 121 bhp so probably not strangled.
Rob Armstrong

I have a Maniflow single silencer on the smaller of the two pipe sizes. The box is at the back behind the axle and runs straight out at the offside rear). It is quite loud but not unpleasant and has never failed the noise tests at Donington Park on track days (measured IIRC at 89 db). As the engine was producing 109 bhp on a RR and I was running with high revs I guess that is quite good so I'm a big fan of Maniflow.
Chris Hasluck

Chris

Offside?

Oggers

Whoops - should be nearside!
Chris Hasluck

Malcolm

I think you’ll find your best results by using a single RC40...

Great sound, great performance and NOT too intrusive (noise wise) but loud enough to appreciate.. :-)

Mark (aged 56 11/12ths)
Mark T Boldry

I have a 1500 with the full Moss GT Sports exhaust and manifold, I'm not sure what size bore it is but it must be around 1 3/4..

It sounds ds really nice and it's not too loud either (I'm 25 so maybe my ears are slightly more tolerable than yours 😋)

After a long day of driving it does get a little tiring.. but we are talking a good few hours in the saddle... Looks great too.


Karl Bielby

time to get that new exhaust...

I hit one of those stupid half sized speed bumps at a bad angle and reasonable speed this morning. it has fair battered my downpipe!

Malc.
Malcolm Le Chevalier

This thread was discussed between 11/07/2016 and 23/07/2016

MG Midget and Sprite Technical index

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