Re: Exhaust question

change the whole exhaust!

Depends really on what you want. Ive got a piper but there are others such as mongoose, powerflow (I think), scorpion among others. Not everyone however does exhausts for your car so its worth shopping around. Also its worth bearing in mind that not everyone will do an exhaust with a tailpipe which you will like. I got a 3.5" tailpipe inwardly rolled, but theres others which you can choose from. Dont go for anything too flamboyant, not unless your car can really shift some.

I dont know which ones are the best, I think it really comes down to money and what you want! Some makes are more expensive than others. Mine set me back 285 quid.

scott

Hi G.T.,

Yeah it's really very complicated to figure out the optimum for a particular car/engine - especially if you're getting into pulse tuning. FWIW, I think that most unmodified cars will have the an optimal exhaust system already fitted, so unless you're modifying the engine or swapping it with something with more power, you shouldn't change the exhaust for an after-market 'performance' system. Well, not unless you don't care about performance and instead you just want something that makes a lot of noise. There are exceptions; for example, I heard that the exhaust manifold is supposed to be quite restrictive on a lot of XU-engined cars (but I have no idea if that is actually true). If you've done some serious engine modifications and you're looking to buy a new system, I think you have two options - either get an aftermarket 'generic' performance job that is known to work well with your engine set-up (by that, I don't mean just get what you mate's got because it sounds cool, ask someone with a lot of rolling road experience) or get something custom-built by someone who knows what they are doing (it can be difficult to find 'em, but they're out there!).

BTW, I'm sure the rule went something like, if you have a 4 cylinder engine (NA) up to 2 litres, generally you shouldn't go any bigger than 3" pipe diameter - but I can't remember where I read it now.

Chris.

Hello,

Well, I guess it's just rubbish. Perhaps they talked about the "wing" fit into the exhaust manifold, which is just here to flush the opposite cylinder during one is in exhaust (remember, should be an horizontal steel part, in the middle of the manifold, into the part just fit after the manifold, into the line, near bulkhead). This, indeed, works great for exhaust performance & pollution.

Hey, BTW, just a personnal thought : I sincerely have no clue about the cost of a team of engineers, probably a lot of £ (or a lot of $, EUR, ... Still a lot whatever currency you use, LOL), and I guess a car is just performant & reliable (and here, into the noise rules) with its "factory specs". I don't think all the driving muppets know that.

Regards, G.T snipped-for-privacy@worldonline.fr snipped-for-privacy@ironmaiden.com

This is exactly my thoughts. A lot of people change their exhaust systems or just the backboxes with little or no other engine modifications. In most cases, the engineers who designed the original exhaust system for a car will have figured out the optimum pipe length, shape and diameter for best gas flow velocity and pulse tuning. There are obviously some compromises (these days more than there used to be) to meet emission controls (Cats can be quite restrictive) and noise levels - but the exhaust systems are still generally good, I don't see that aftermarket 'performance' systems can really make much or any difference, unless some significant changes have been made to the engine. I've been thinking about getting a custom-built stainless steel exhaust fitted to my car because: 1, I'm fed up of it rusting away and 2, Changing an engine from carb to fuel injection and increasing the peak power by about

Chris.

Hello Chris,

Mmmm, I'm thinking of my mum's '88 405, which stayed over 10 years with the same exhaust pipe, before it was drilled by rust. Probably the 305 exhaust didn't have an as good design : on 405s, there's a hole in the pipe which is used for residual water evacutation. No more noise, as it was designed for it.

True, but a properly custom designed exhaust (no matter it is classic or stainless) must cost a lot. Perhaps you could try to see if the 405 line (for example from intermediate to the backbox) could fit : I don't think the pipe after the exhaust manifold is really different. Of course, I hope you're already running with the 405 manifold...

Regards, G.T snipped-for-privacy@worldonline.fr snipped-for-privacy@ironmaiden.com

Every time I've replaced the exhaust (both on my old GR and now on my GTX), I've ended up with a slightly different design. The latest change I made was the centre section, which now gets wider for about 10cm in the middle before going back to the original size. It never used to be like that!

I think it probably would be quite expensive. When I took the cylinder head off the 405, I noticed that the diameter of the exhaust was much larger all the way along the exhaust. However, the manifold design on my old 305 GTX was exactly the same - it just gets smaller at the end where it joins to the centre section (where the 405 does not). I couldn't use the 405's manifold because it had rusted to the centre section and I had to angle-grind it off. So yes, I am using the GTX's manifold! That's why I think I should just go and get a full new system. I originally thought that the injection cylinder head probably wouldn't work too well, so I didn't worry too much about changing the exhaust system at that stage - I just wanted to see if it would run at all! Of course, you know what happens when you get something running on a car 'temporarily' - it has a habit of staying that way for a bit longer than expected ;)

Chris.

Hello,

Quite normal, as it has more power.

That may cause the engine to run not that well...

... But it was "4 test only"... Of course, I know how it works. The system (whatever it is) works, and finally you say "oh, it just runs good enough like that, it doesn't worth another headache to mod it now" :-)

Regards, G.T snipped-for-privacy@worldonline.fr snipped-for-privacy@ironmaiden.com