Blowing exhaust = large loss in power?

shauncr91

shauncr91

shauncr91

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Ok about a week ago my exhaust started blowing, I thought nothing of it and opted to get it fixed in January when I've got enough spare cash.

However, I've also noticed that my car is feeling more and more sluggish since it started happening, could this be a direct effect of the exhaust damage, or a whole new issue? (Car's a '99 Clio).
 
shauncr91 said:
How hard would it be to fix it myself do you reckon?
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Depends on what you mean by "fix", where it is blowing from, and how the exhaust sections connect together.

If you are going to replace the blowing part, and said blowing part isn't the manifold/downpipe or cat sections, then replacing a mid section (if existant) or backbox section isn't too difficult. Although you may find that the sections are pretty rusted together and can be a PITA to separate.

If you mean sealing up the hole, then you'd need to know how to weld, and either weld in a very confined space under the car, or remove and re-fit the section.
 
Or use a can of coke and some jubilee clips ;)

Uh I mean, don't do half arsed jobs kids. Always seek the help of a professional.
 
If I were you I'd have a very close look at the rest of the exhaust if it's still on the original, the backbox on my 99 Clio fell off last year and the rest of the exhaust was rusted through so had to replace the whole thing. The standard exhausts seem to rust rather well.
 
Power loss depends on the induction, generally na will lose you power but on a turbo you will gain and then some. ;)
 
DampCat said:
Or use a can of coke and some jubilee clips ;)

Uh I mean, don't do half arsed jobs kids. Always seek the help of a professional.
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I use a baked bean tin....stronger than coke..bosh loads of cheap silicon sealer on it before tightening jubilee clips and it lasts for ages:D
 
Busa said:
I use a baked bean tin....stronger than coke..bosh loads of cheap silicon sealer on it before tightening jubilee clips and it lasts for ages:D
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gun gum is the putty of the gods... not really though, i find other brands of exhaust putty muuuch better from my limited experience.
 
Gaygle said:
How much power should it lose and why? I thought it would be negligible.
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Think of a garden hose. With the end free the water flows slowly, but if you restrict the end a tad with your finger the water flows a lot quicker. Restrict it too much and not enough water comes out, and so on. it's all about getting a balance.

In a purely functional sense, the job of an exhaust system is to get the most exhaust gasses out of the cylinder as quickly as possible and to do this you've got to juggle about with the much misunderstood idea of 'back-pressure'. Too much of a restriction in an exhaust system means that not enough gasses are flowing (restricted hose), too little of a restriction (in the case of a hole in the exhaust) means that the gasses aren't flowing quickly at the optimum velocity (completely unrestricted hose).

When it gets complicated is when we start asking ourselves why you want gasses flowing at an optimum velocity. Basically you want to scavenge the most spent gasses as possible during the split second the inlet and exhaust valves overlap (are open at the same time), the faster moving gases on the exhaust side creates a vacuum that the spent gasses still inside the cylinder rush to fill and as a result move out of the cylinder before the next stroke, but don't ask me to explain the science any further than this, because I can't :p.

How much power you'll lose is dependant on the hole (among other things), but it certainly doesn't surprise me that you're noticing the power loss.
 
I noticed the power loss in my old Megane (when you only have 90bhp, you tend to notice every last one ;) ) when the exhaust was blowing. Although I'm sure the knackered, rattly cat didn't help matters ;)
 
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