7 replies to this topic

[mini-mad-mark]

On all my three minis I'm currently using a single box RC40 system which I quite like in terms of fitment and noise/sound and as far as I am aware is OK for performance (2x 1275 using std bore LCB and the 998 using a Cooper freeflow  - all MiniSpares supplied although possibly Maniflow manufactured I guess? (The freeflow defniitely Maniflow)

 

Note - I did have a twin box RC40 system on the 998 for a while but it caught all the speed bumps round my way  (and I couldn't get off the driveway without it catching)  so I changed it to single box in the end. 

 

 

I'm just starting a new project which will be 1380 with 286 cam (possibly weber 45DCOE funds permitting!) so hopefully a bit more meaty than my current minis; I would like it to sound a bit more aggressive (Its going to be a "weekend warrior" type car not a daily or long distance car although maybe with ear defenders......!)

 

What do people think about the Maniflow 2 inch bore exhaust used with a Maniflow LM5 large bore LCB  - would that be OK for my engine level or too much, and kill performance? Has anyone got this set up and does it sound a bit  "harder" or would I be wasting money? (more than twice the price for the Maniflow large bore set up)

 

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[GraemeC]

Personally I would go for the 1.7/8” system - I don’t think you’d gain anything from the 2” other than a lighter wallet and a tighter fit. Depending on the cam etc it may even lose you some torque.

[nicklouse]

Why a 45? A HIF44 will give the same power and better economy.

 

exhaust bore size comes down to what the build needs in relation to the power output. It has nothing to do with noise. Reduce the number/size of the silencers to add noise.

[Midas Mk1]

I’ve had a 2” single box maniflow, for your question on noise, sounds more aggressive than the 1 7/8 single box with rcm that the same car has now.
Got a 2” centre maniflow on the other one and large bore stg3 lcb, fits and sounds a treat.

Edited by Midas Mk1, 08 January 2023 - 10:38 AM.

[Northernpower]

On my 1342 7 port injected I originally fitted a 1 7/8 system. I thought it was restricting it at higher revs so changed it for a single box 2 inch. I put it back on the rollers with the 2 inch fitted and as expected it lost out on torque at lower revs and didn't match up until 5K revs at which point it was slightly better. It did sound crisp but I ended up fitting a centre box just because I got fed up with the noise on longer runs. Back on the rollers it regained the torque and was a much less tiring drive. It depends what you're looking for in performance and how you're going to use it. In hindsight, for me, the twin box 2 inch for road use was not worth the extra.

[Cooperman]

A 1380 with a 286 cam should run fine with a 2" exhaust. The 286 gives its peak power at 6400 rpm and you can expect to be running high revs a lot of the time, so there is a lot of exhaust gas to clear down the pipe. Ideally, for best overall oerformance you need to keep the revs over 5000 rpm when driving hard, and unless you are going to drive hard a lot of the time, then the 286 is not the best cam for you.

One other thing, I presume that you will be fitting a close ratio gearbox and a lower final drive ratio in order to keep it 'on the cam'. I have a 286 in my 1310 cc 'S' and I run a SC CR gearbox with a 3.9:1 final drive ratio, That's about ideal and my exhaust is a 1.875" dia. Gearing is about ideal with that set-up and if I change up at 6500 rpm it is still in the optimum power band.

I hope this helps.

[mini-mad-mark]

Why a 45? A HIF44 will give the same power and better economy.

 

exhaust bore size comes down to what the build needs in relation to the power output. It has nothing to do with noise. Reduce the number/size of the silencers to add noise.

I was going with an HIF44 originally (as I happened to have a good carb) but a few people suggested that a 45 would be better with the engine/cam combination I have  - I bought a complete (good) S/H engine with this CC/cam combination

 

I may change the cam for something more tractable/road friendly (noting Cooperman's FDR advice) - just gone to the engine builder for a check over and head job so I will ask his advice about the whole thing. (He already suggested an AC Dodd RS+ cam?)

 

I just wanted the mini to sound a bit "racier" as my current minis all sound quite civilised - I don't want a hooligan loud noise (like those Fletcher SS 3 inch bore jobbies) just a bit more meaty if I could, but it seems that the consensus is not to go for the 2" bore Maniflow and probably go with an HIF44  -  my wallet will appreciate it !!!

 

Thanks to all for the advice.

[Cooperman]

Mine with the 286 has to be low geared in order to keep it 'on the cam'. It's fine on very twisty tarmac roads when the revs are high, but at 14 mph/1000 rpm in top, that's 5000 rpm at 70 mph. Fine for a rally car, but on the road, with the necessary SCCR gearbox, it is a bit tiring. Mind you, when it is 'up on the cam' it doesn't 'arf go!

My 1330 cc 1990 Cooper has a nicely-flowed head, an HIF44, MG Metro cam, LCB with a 1.75" exhaust, a gearbox with the original Cooper 'S' gear ratios and a 3.44:1 final drive and it is excellent on the road. It has 16.5 mph/1000 rpm in top, so 4200 rpm is 70 mph and the cam gives peak power at 5700 rpm with peak torque at around 4200 rpm. That seems about ideal really.