AlexM

Hi,

I'm looking at adding either a SS downpipe, magnex midsection (with resonator), or possibly both to go with my SS backbox. My car goes well, but feels a bit like there is a potato up the exhaust at 6-6rpm - and there no point in revving it any higher.

I'd like to keep the volume of the system to it's current level or as close as possible...

My questions are as follows:

1) Is the mid section worth replacing on it's own? If so, how much louder will it be?

2) If the downpipe is replaced does this increase volume greatly when used in conjunction with a standard midsection?

3) Is the combination of SS downpipe and Magnex midsection very loud with the SS backbox?. If so, would a different backbox help keep the noise levels under control without negating the benefit of the changes?

Thanks in advance,

Alex

P.S. my car is a UK MY98

Matt Churchill

Alex,

I went from a SS back box to a full system, so I can't advise on all of your questions.

1. Don't know - but probably!

2. Again don't know, sorry.

3. I would suspect that a magnex would be around the same as a scoobysport mid - so yes, it is a bit louder. I seem to remember reading that some back boxes can be quieter than others, but I think this is at the expense of performance (don't quote me though).

My personal advice would be to do the lot. The noise at low revs isn't that much more I think, but when things get going it sounds like more of a rally car - which can only be good

I still don't rev mine that much at the level you mention, but I found that the improvement low down was awesome, it picks up a lot quicker, and helps performance (or at least that is what it looks like on the Dyno site).

BTW mine is a UK99.

Hope this helps
Matt

john banks

My car MY00 then to PPP - so new centre section and Prodrive BB - increased volume under load, not much difference otherwise. Compared to another car with the addition of a SS DP and PPP it sounded like a BMW! So it seems like a DP makes the biggest difference, but is obviously modulated by the rest of the system.

I am considering a Falkland twin dump DP - may give more power than SS but this is theoretical - see other posts.

RON

If you only want to do One bit, do the downpipe, thats sure to make the biggest difference, thats what I did, only trouble is, six months on I'm now thinking of changing the middle bit aswell!
Ron

Sith

The DP gives the most gains and also the most noise. Alot more noise.

Trying to make up my mind to get either the Magnex resonated or non-resonated centre section. Every little helps.

Prepared to be shot down in flames here, but IMO The SS DP and BB would probably let me keep with a PPP motor with no other mods.

Flame suit on with sand buckets on the beach with high tide.

P.

john banks

Andy Tang

iTrader: (3)

Hi Alex,

I've tried a couple of combinations:

SS backbox/SS downpipe/Standard Centre - MY97 UK

The downpipe does make the car louder. You'll hear the turbo spin up much more, and there is a noticeable increase in cabin noise.

Will still pass an MOT if the centre cat is still working order, as I had my old car checked.

There was a marked improvement in performance!

SS downpipe/SS backbox/Magnex Centre (with resonator) - MY99 UK

The car goes much better! But believe it or not the car is quieter than the old one!

Much quiter than cars with a full SS system!

Unsure if I would bother just changing the centre, I think I'd rather change the downpipe than the centre! (Performance wise!)

Might be worth having a chat with Pete Croney, as I believe SS have supplied backboxes which are quieter!

Might be worth popping along to some meets, and going for a quick spin!

Hope this helps
Andy

Ps - Hope you are keeping well!

Al Cook

I dont'w want to change the direction of Alex's post, but he raised a valid point that Andy touched upon. Mainly only having one cat in the system.
I have a 94 WRX and passing my MOT after installaing a de-catted SS DP and new BB (keeping my mid section) is a cuase for concern.

I'd hate to spend out on a nice system only to find at MOT time that i'll have to replace the centre because the cat stopped working 2 years ago!

So, do cats have a life span?
Is mine potentially dead?

No Jokes about 9 lives either pleeease!!



[This message has been edited by Al Cook (edited 22 August 2001).]

LEE P

Well peeps ive got my flame suit on!!! but ive been talking to a reputable tuner, and he informed me MY00 cars only have one cat and thats the downpipe! centre section looks like a cat but is not apparently. so they said down pipe and back box. dont incinerate me just what i was told. also my dealer said P1 does not have a centre cat either! im heding for the hills!

dowser

STi's/P1's don't have a centre cat. All UK/euro cars do..until you fit the PPP, which has an STi centre.

Your dealer was right, the tuner obviously only works on imports

If you want a quiet d/p, I believe mild steel is much quieter than stainless steel. Can anyone confirm?

Richard

macker

Well to put a New Zealand perspective on things, I have mucked around with the 94 WRX Ra spec engine in my Legacy and found that the rear muffler and front pipe made all the difference and the centre (when replaced) didn't seem to do squat..I've never had it on a dyno to check it mind you...we're a bit short on 4WD dyno's here in Christchurch.

And you are right the centre just seems to have a small resonator box in it rather than being a CAT, which buy the way we don't have to retain it if we don't want to..a good front pipe here costs about 50 of your pounds and has a nice waste gate seperator that merges about 30cm down the pipe...;-)

dowser

Hi Macker

Where do you get the £50 front pipe? Are they online?

Thanks
Richard

Adam M

Mild steel downpipes are much quieter. BPM is mild steel twin dump three inch and hpc coated.

They claim 6 db quieter than equivalent stainless pipes.

I have one of these on my car and am very pleased with it.

As for rest of the system, HKS su[per dragger, like on anders car was scarily quiet, like normal car quiet, and with equal length headers!!! But exhaust noise and volume will vary enormously from car to car. Turbo makes a difference to this too.


Performance wise, I have been reliably informed that a straight through centre can show a 15 bhp gain on the rollers. This was tested on the same day, at power engineering. Both straight through, but one with resonator, and one without.

I doubt everyone would see this, but to say it wont make a difference is a generalisation.

Alex, you kow your stuff, you know how these things work, more restrictive equals quieter in general. Its your choice wheer you want to strike the compromise.

Only mild steel, will yield no performance loss, yet be quieter, but you pay with longevity!

JAMES BUSHELL

The MOT shouldn't be a problem on a 94 WRX as the cars aren't listed.. as they're Jap imports.. So they can't check the emmisions if there's nothing to check against..!

I haven't had any Cats for about a year now and no problems...

James

AlexM

Chaps,

Thanks all for your comments.

I think that I shall start off by fitting the SS downpipe and take things from there.

For the time being at least, I'll retain the standard center section.. mainly to verify that the car will pass an emissions check with it fitted. If this is proven, then the center section can be swapped a lot more easily than the downpipe at MOT time.

Adam - an interesting comment re: the respective noise levels of mild and SS downpipes.. does lagging make any difference to the acoustic properties of the system?. I agree re: the trade-off of restriction vs. noise levels, but I'll have to get myself along to a meet to see what this means in practice.

Regards,

Alex

Adam M

Mild steel is definitely quieter due to its resonance characteristics. Therefore BPM is quieter. Hpc coating is supposed to address corrosion issues.

HKS super drager is scarily quiet. BPM centre with Cat didnt silence my car a whole lot. So not sure how much diff a resonator would.

Pete will amke up a special silenced back box.

Try trax, or perhaps come along to the meet at teh pub in Letchmore Heath teh following week. Should be plenty of us.

The Saint

Am I right in thinking that the MY00 only has one cat, in the downpipe ?

RON

Message for 'the saint'
No A my00 has two cats, one in the centre section aswell as the d/p!

The Saint

Cheers, that's cleared that one up.

No wonder it goes better when they are both removed.

Is it right that the turbo on this MY has some sort of restriction plate/obstruction in it too & that an aftermarket downpipe removes this ?

Lambo

Adam, I've just put a SS downpipe ( lagged ) on my MY99 wagon, with the std c/p and a std P1 bbox. There has been no increase in noise inside the car, although, if I have the windows open I can hear more turbo whistle, which is pretty cool.
This would indicate that the bbox probably has the biggest influence on the sound rather than the d/p.
Hope this helps.

Lambo

PS. Car much more responsive than before, revs to 7000 rpm easily.


[This message has been edited by Lambo (edited 28 August 2001).]

Adam M

Lambo, i find it hard to believe that changing the downpipe and removing a large cat has had no effect on the volume. Lagging will improve things but not that much.

Besides what happens on an individuals car can only be a guide to what will happen on another car. It cannot be used as an example.

Thst why I only report experiences on my own car.

Eg BPM back box on ss mid section and downpipe was excrutiatingly painfully loud. And not nice either. Cant explain why but the mix was awful. BPM full system sounded nice (without bung only) and SS system as ever also sounded great, but the mix.......... never again.

The total noise is not simply the sum of its parts, unfortunately it doesnt work like that.

All I can suggest is have it fitted on the promise that if not liked, It can be swapped back, assuming that you pay for the labour.

I cant imagine many will be swapping back though.

Incidentally, I think physical issues such as the mild steel, will always be quieter relative to an identical stainless steel equivalent. But then I dont think you can buy a stainless bpm downpipe!

Sith

Agree with Lambo. Not much more noise inside the cabin. But outside, armagedon is comming.

P.

Lambo

Adam, I was only reporting my own car, and the plain fact is that changing the dp has made no noticable effect on the noise inside the car, whilst having a definate inprovement in the performance.

ROBO

I`m running an my 98 with a HKS hiper mid section, backbox and a BPM downpipe.
It is loud, but it sounds the bollox.
Cabin noise is obviously up, but bearable.
No way is it legal as there isn`t a catalyser in sight.
Fit a full system have some fun, but be prepared to play around for the mot.

AlexM

Scoobysport D/p is on the way..

Cheers,

A.

Luke

Adam M

When is this meet?? and Is it the Battleaxes or the one opposite the Hari chrishna place???

Cheers

luke

Do people tend to bring bits to sell etc??

YorkshireSimon

I think I must be the only idiot who owns a de-catted downpipe and not have it on the car.

I have the full HKS Super Drager system, but only have the mid section and back box on the car. I have seen in my local area police making random checks on vehicles at the roadside.

I guess they have instructions to pull cars older than 5 years, and Scooby's and EVO's. No fair really.

My point here is, I do a lot of miles in my motor with work, and if police are actively carrying equipment to check noise and emissions levels, should I be taking the risk? It seems to me that almost everybody on this BB does the whole lot, but I am curious as to finding out if anyone has had any run-ins with the law?

What's the general opinion here, am I the only one that worries about a rather large fine? Or like I said, am I an idiot for not getting it on the car, and stop worrying...

Thanx

YS

john banks

I'm wondering when I put my Falkland DP on whether to put on the OEM not PPP centre catted section - at least then it should *just* be illegal, but how much performance would I lose? Would it make any difference to noise levels? Presumably DP + OEM centre + PPP backbox will be better than PPP setup with OEM DP + PPP centre & rear?

ROBO

Simon.
If your doing a lot of miles mate, i wouldn`t risk the pull if your worried about it, would only **** you off if you fitted it and were pulled.
I only drive my car for 9 weeks of the year so i arrive home make a lot of noise for a few weeks, and then put the car away until the next time, chances of a pull, minimal.
Rob

YorkshireSimon

Fair comment Rob.

Still, makes me dead jealous when I think I have got one of the least responsive scoobs on the road. You are right though, sods law will say that I would be pulled.

Cheers

Simon