More Noice = Less Speed??

[Duncan Hermer]

I know this subject may have been covered before and that the debate raged on, but about 10 days ago I had an exhaust conversion done on my Chim.

Not the full on sports exhaust, but the "cut open the box, remove the baffles, replace perforated pipes with solid ones and refit" modification, done at Peninsula.

First impressions - fantastic, loads more noise and an altogether 'better' sounding Chim - all for a fraction over a hundred quid.

However - last Saturday, funny bloke in Mini Cooper decides to speed up in inside lane as i overtook him going up Marsh Mills flyover in Plymouth - about 1/2 mile long hill. Usual sequence followed - laughed to myself and put my foot down. Was in 5th doing about 90mph and the time (approx 3500-3750rpm.

Thing was, for the first time since i've had the car, i didn't get that "arse dropping, forward lurching" moment of torqeyness as i shot past the mini. I just sort of sped up gradually - just enough to prevent embarassment.

Now i know others who have had this mod - one actually at Peninsula too and have had absolutely NO effect at all. I'm wondering if it was a one off thing or has my ability to show my heels to others really been lost from a simple mod which hasn't affected others? How can it affect one and not another?

i don't know if any of the Peninsula guys follow this forum but could anything different have been done and have others mentioned this to them?

Like I say, hoping it's a one off and will test for sure once the rain, wind, sleet and snow vanishes.

Any feedback from others would be useful before test day.

Duncan

PS Noticed the spelling mistake on topic title after posting and can't seem to change! It reads 'Noise' BTW

>>> Edited by Duncan Hermer on Tuesday 28th January 20:55

[CLINT887]

Any feedback from others would be useful before test day.

Had exactly the same conversion as you for about the same price AND same result lovely noise BUT definite slight loss of torque mid-range. Improved a lot since I had one of Tim's induction jobs fitted. Can one of you experts out there explain please.

Had a clean up for you Clint, hope you don't mind.

Big Al.

>> Edited by ABBTVR (moderator) on Wednesday 29th January 22:11

[shpub]

Fiddle with the exhaust and it changes the back pressure which screws up the gas flow which screws up the power. On some cars it screws it up more than others. Bit of a lottery on the potential effect though.

Steve

[shpub]

You might want to check that the car can now meet the noise limits for your test day. Most of these conversions cause big problems as the cars are simply too loud.

[2 sheds]

I'm not a fan of the zero silencing, IMO they sound a bit hollow and can spoil the chances of track days. as far as losing power it depends whether the internal silencer pipes are too big, as Steve says the silencer will produce some back pressure although only a small amount, curiously i have dyno'd many cars with and without silencing and there has never been a marked difference in output.
Tim

[CLINT887]

shpub said: Fiddle with the exhaust and it changes the back pressure which screws up the gas flow which screws up the power. On some cars it screws it up more than others. Bit of a lottery on the potential effect though.

Steve
This is interesting. I know nothing about tuning exhausts but I imagine that basically you arrange header lengths so that the exhaust from one pot does not impede the exhaustion process in another. Since all the pot exhausts in a tiv V8 are swallowed up in a gigantic railway-tunnel-like black hole where is the tuning? This means as Tim says that the effect is probably minimal. I wouldn't call the noise "hollow"--rather like an old fashioned propeller aircraft ticking over. Now a powerful bike--that's a hollow sound--quite different.

[corin denton]

I've had it done and it sounds monster monster , always gets remarked on at club events and as for track days - that's why they make drop-in silencers.

[2 sheds]

Another thing, the steel tube fitted into the silencer must be 100% air tight !. I still don't like the idea of zero silencing, but if you really want to go this route be careful.
The ideal exhaust system would be smaller bore everywhere including primaries, but thats another story.
Tim

[shpub]

corin denton said: I've had it done and it sounds monster monster , always gets remarked on at club events and as for track days - that's why they make drop-in silencers.

Drop in silencers will give you about 6 db improvement. Many of these exhaust conversions are 110 +. Do the sums and that rules out most track days which are now around the 98-100 level. Anyway your choice.

Steve

[Paul V]

New or old mini? If it was an S and he was working the gearbox I don’t think they’d be to far behind a 4-litre chimera especially as you didn’t drop it a cog. A friend’s 1425cc classic mini often gives people a fright.

Maybe the car isn’t lacking, just the other was quicker than expected?

[Duncan Hermer]

Paul - this is what i've been trying to tell myself too. I'll be seriously wounded if this has decreased my power and will have to consider one of Tims induction jobs that Clint mentions - whats the score here Tim.

New mini by the way - but not an 'S' just a standard - i checked this before i put my foot down! The real worry didn't develop from the slowness at which i passed him, more the lack of thrust you normally get - at any RPM and in any gear.

[Paul V]

Maybe its time for a rolling road set up to make sure things are ok.

[corin denton]

Hello , I must apologise on Duncan's behalf for wasting everybody's time , I took his car out today and it's aqbsolutely fine , don't tell him but it's just his woosie driving!

[Duncan Hermer]

Corin's right I'm afraid. I think I whooped myself up into a paranoid state for no reason. Or perhaps just thought my car was faster than it actually is. Woosie driving? More driving to the limit which perhaps isn't quite enough