21 replies to this topic

[dickster]

Got the Mini back tonight after having a two box 1.75" Maniflow exhaust system including manifold and replacement cat pipe fitted to my otherwise standard '95 Spi Cooper, I was under the impression that performance exhausts didn't really make any noticeable difference to performance and that only the smallest amount was usually noted right at the very top of the rev range so I was more than suprised to note that my Mini really flies now-I just can't belive the difference in performance and its too much of a difference to be just be me thinking its better as I fitted it for looks and a slightly better noise and to confuse me I read an article in one of the mini mags that said the standard exhaust was restrictive.

I'd be interested to hear of other people's expericences with exhaust systems comparing before and after performance especially with Maniflows.

I do find it a little too close to standard noise-wise, I wonder if I should've gone for a single box system or does anyone find that the noise improves (i.e sounds nicer) as the system 'beds' in with carbon?

[Adcuz]

I beleive that the twin box version is slightly better than the single box as far as performance goes.. Noise doesn't matter!

[GreaseMonkey]

I'm interested in this

I've heard there is no difference in noise between a single/twin maniflow around town but its noticeable on the motorway?

Also that a twin box can slow down the movement of the gas as it goes through two silencers where as the single goes through one but have heard the twin can be better?

Anyone with experience of Maniflow exhausts?

I did once have a single box maniflow on a mini, sounded great.

Edited by GreaseMonkey, 09 September 2009 - 10:43 PM.

[Sherlock]

I'm very pleased to read this, for years I've been hearing that exhaust systems make little difference to performance & for years I've known this is not true. I have a 1981 Mini 998 HL, which had the normal 'pea shooter' exhaust when I bought it, 23 years ago with 17,000 on the clock. Performance was better than most 998's I'd ever driven but the engine always seemed stressed at anything over 4000 rpm & it also 'pinked' dangerously at high revs. I fitted a Maniflow 1.75" single box system with LCB manifold & it was like releasing a beast, The engine is much smoother, revs much more freely, has never pinked since fitting this system, runs cooler, it's more economical & the emissions are improved. The increase in power was noticeable immediately which means it is more than the 3-4% increase most people seem to claim from an exhaust modification. (0.3 seconds quicker to 60 mph than a 998 Cooper). I use the single box system as a 998 doesn't produce as much noise as a 1275. It will sound nicer when the perforated inner tubes of the silencers get get a bit 'carboned up' which reduces the effect of the sound absorption material. I think you have made a wise choice, Maniflow systems are well respected, & if you are interested in sound, they do give a typical classic car note. On a technical note, reducing back pressure can lower combustion temperatures, not a bad idea, considering that unleaded fuel burns faster & hotter than the fuel the A series was designed to use.

Edited by Sherlock, 09 September 2009 - 11:03 PM.

[The_Mistro]

i have a twin box maniflow on mine, only from the cat back, but i think its better through the mid rev range than when it had the pea shooter on it!

is the twin box a better for performance than a single as it keeps a better back pressure, as a straight through exhaust isnt good for performance because of the lack of back pressure!

Edited by The_Mistro, 09 September 2009 - 11:16 PM.

[Sherlock]

i have a twin box maniflow on mine, only from the cat back, but i think its better through the mid rev range than when it had the pea shooter on it!

is the twin box a better for performance than a single as it keeps a better back pressure, as a straight through exhaust isnt good for performance because of the lack of back pressure!

4-stroke engines are not dependent on back pressure like 2-strokes are, it's more to do with gas flow & tuned exhaust length. For instance it's not wise to fit a 2inch system on a 998cc Mini because the exhast gas velocity will be too slow, but on a tuned 1275, it's fine.

[blake12345]

is a 2" exhaust to big for a moderatly to highly modified 1098cc?

[Sherlock]

is a 2" exhaust to big for a moderatly to highly modified 1098cc?

With a good LCB exhaust manifold, it would certainly work ok, it's often difficult to come up with the optimum exhaust without experimenting, but I would give it a try, I have seen a 998 with polished/ported head & 948 cam run very well on a 2" system & although I would normally say that's too big, it was quicker on acceleration than my similar car with 1.75" system. Your engine in a moderate/highly tuned state will push more exhaust gas & the long stroke engine may help, I don't know the science behind this but it's all down to exhaust pulses, which is what led to the design of the LCB. Having seen how well the tuned 998 ran on a 2", I say go for it.

[Mr Duck]

When I fitted my new system (2.5" DTM Fletcher single box) I also got the downpipe sorted out. Now, it might be because I didn't have any more holes in the system, but it went like a bat out of hell when I took it out. I also refitted the cat. converter - no real performance loss and it made the (rather awesome) noise much more bearable. Without it I could feel my ears *bleeding*.

Oh, and it's a Cooper 1275 MPI.

[Bungle]

when i ditched my standard rover exhaust (with cat) for a RC40 single box exhaust (no cat) +matching LCB manifold

i found the car would rev so much freely, it was if something was holding the car back before

i also found a tank of fuel would go a lot further

once things were set up the power went from a standard 62 BHP to 70 on a rolling road

[Jay3178]

i fitted a maniflow system designed for miglia racing to mine, with cat replacement pipe and stage 2 LCB. i found it made a more noticable feel to the performance compared to the DTM i had prior and a much nicer and slightly quieter exhaust note. here is what mine looks like on my MPI Cooper

[dickster]

I'm interested in this

I've heard there is no difference in noise between a single/twin maniflow around town but its noticeable on the motorway?

No idea, we don't have any motorways here!

Well already sounding a little better noise-wise, as mentioned I expect it'll sound a tad throatier once its got some carbon in it.

when i ditched my standard rover exhaust (with cat) for a RC40 single box exhaust (no cat) +matching LCB manifold

i found the car would rev so much freely, it was if something was holding the car back before

i also found a tank of fuel would go a lot further

once things were set up the power went from a standard 62 BHP to 70 on a rolling road

Thats quite an impressive rise from just an exhaust system. Keith Calver suggests in articles that the standard cat is quite efficient but no doubt after 15 years the internals have either broken up or its lost its efficiency-that might explain the vast difference in performance.

Edited by dickster, 10 September 2009 - 07:29 AM.

[Asphalt]

i fitted a maniflow system designed for miglia racing to mine, with cat replacement pipe and stage 2 LCB. i found it made a more noticable feel to the performance compared to the DTM i had prior and a much nicer and slightly quieter exhaust note. here is what mine looks like on my MPI Cooper

Hey - do you have any more pictures of this system?

Re: power increase:
Don't underestimate the psychological effect of a 'sportyer' exhaust. Placebo-effect and such!
Or maybe you'r just more 'active' on the throttle now that you get 'rewarded' with good sound.

Anyways I think a good designed exhaust can improve erformance a bit. Less restrictive exhaust = less backpressure = more torque.

The truth is possibly somewhere in the middle (placebo & increse in torque) - Enjoy!!

[dickster]

Re: power increase:
Don't underestimate the psychological effect of a 'sportyer' exhaust. Placebo-effect and such!
Or maybe you'r just more 'active' on the throttle now that you get 'rewarded' with good sound.

Anyways I think a good designed exhaust can improve erformance a bit. Less restrictive exhaust = less backpressure = more torque.

The truth is possibly somewhere in the middle (placebo & increse in torque) - Enjoy!!

Definately not and I was aware of the possible placebo effect, I also own a older BMW M3 so I am used to cars with real power and I understand the principles of torque, this was my whole point of the post, that the increase is definately real and completely unexpected-I fitted the exhaust thinking it would look better and sound a bit nicer I didn't expect there to be any difference in performance.

Edited by dickster, 10 September 2009 - 08:30 AM.

[alicetheauto]

Did any of you guys have the car rolling-roaded when the exhaust was fitted? This could have found a few bhp from ignition timing, mixture etc already being slightly out with the standard tune, so making the difference seem greater when you have the new exhaust fitted?