No muffler/straight pipe

[Davidov]

Hi.

Myself and Taza are interested in the affects disconecting the muffler/ putting a straight pipe has on the car.

We have done it in both my outback and his 1st gen forester (temporary fun trial). With both cars the sound is incredible.

With the forester it didn't seem to have any ill affects. If anything the power of his 2.0L engine especially offroad seemed to be better.

With my 2.5 outback the engine power seemed quite significantly reduced.

Can not having a muffler have any ill affects on catalytic converters or the engine itself? The power im guessing has to to with back pressure, the foresters muffler providing too much hence improved power with removal. The outbacks muffler must be providing just enough back pressure, hence removal results in reduced performance.

So can it be damaging?

Cheers
David

[El_Freddo]

I've heard you might burn out the exhaust valves, but I don't see how this works as the fuel will still be burning as it exits as it does normally with a muffler.

The only real ill effect I can see is that you'll turn your subis into cop magnets...

Power isn't from back pressure - the low engine torque requires the back pressure, this is probably what you're feeling. Later in the rev range should be another story though, only real issue with this is that A) you'll probably be using more fuel and B) if you don't normally drive your subi high in the rev range you probably won't notice a difference anyway...

What you'll both be looking for is a straight through muffler (don't get a cannon - that's totally ricer and even then they look stupid, Alex has a better word for it like south park does - and no Alex it's not "totally awesome") that's probably a glass pack or something of the like.

I've got a question for you - with the straight through pipe do you get irritated by the droning a cruise or is it not there?

Cheers

Bennie

[Davidov]

I've got a question for you - with the straight through pipe do you get irritated by the droning a cruise or is it not there?

Cheers

Bennie

In my outback the droning isnt really there at all. Its all but un noticable. Coming off the accelerator for a gradual slowdown from fairly high RPM is quite loud and could get very annoying in stop-go traffic.

In the forester the droning is very loud and annoying. After a few hours we were over it and wanted to put the muffler back on.

I have noticed that the outback (at least my gen vs 1st gen foz) has a lot more soundproofing so that could be part of it.

[mud_king91]

.My pop was a marine engineer... he used to yell at me for doing things like that to my cars as no back pressure damages something in the engine... never listened to him tho so yea sorta regret that now

[mud_king91]

Tho in saying that i blew the exhaust off my old t/diesel pajero it lasted 2 weeks running straight from the extractors before it totalled my brand new injector pump and melted the rings

[Davidov]

I asked a high ranking police officer if it was legal and as far as volume he wasnt quite sure (tests since put volume as being legal). However he did warn that it can play around with the catalytic converter sometimes (therefore be illegal) and that it can damage the engine (valves).

[Gannon]

Backpressure is very mis-understood

It is not backpressure that you want as any restriction to exhaust flow reduces power.

The reason for small diameter primary header/extractor pipes is to keep exhaust gas flowing quickly and to make use of the momentum of the pulses of exhaust gas to extract gas from the next cylinder.

If you fit header pipes and or an exhaust system that is too large, you will experience a lack of low rpm torque because of the exhaust gas isnt moving quick enough to to its extracting.

Fitting a free flow muffler or a straight pipe of the same size as the original system will only have a slightly positive effect, but I doubt it would have a negative effect.