Vehicle & Technical > Discovery

tubular manifolds / exhaust system

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Range Rover Blues:
Yeah, but it's a bit, just a bit.  Not worth £450 odd quid or whatever, hardly worth the £230 I just pais S/H for an LSE one.  For me it's the unreliability of the standard exhaust.

ALso I've found that the 3.9 EFi exhaust is pretty efficient, the extra power of the 3.9 above the 3.5 is mainly due to camshaft and exhaust, it's bigger bore already so perhaps I'm not best placed to judge, but if I'd bought it for the performance I'd be dissapointed.

Something I found by accident, the LSE goes through one or another exhaust manifold gasket roughly every month.  This last time I snapped a stud in the manifold and couldn't be a***ed drilling it out so fitted the old one from Blue.  
Well the portings are smaller on the old one, so did Rover change the size of the exhaust track on the serpentine engine/10 bolt heads or has my engine and exhaust been reworked when the engine was tuned up?  Does anyone know for definite?

Eeyore:
One of the huge problems with tubular systems is that the designers forget about the expansion co-efficients of the differents materials involved. Many system exaserbate the problem by using a single flange for each bank (nooooooooooo!). Best to use indivdual flanges for each port ala the original systems and fit them with a freaky taper bolt system to allow for some movement without inducing distorsion in the flange faces (there's only a couple of companies I can think of that actually offers this).

Another problem is that the designers also forget about slight problems such as pulse overlap in the exhaust flow, made all the complex because of the daft firing orders of the Rover v8. This is the key reason why a lot of tubular systems for the rover unit aren't as good as they could be. When the exhaust port is open and expecting to exhale, it gets met by a pulse of exhaust gas coming the other way.

Sadly a lot of exhaust makers are very good welders, but don't understand sufficient about gas dynamics, or how the engine will be used. How many times have you them talk about 'balanced flow?'.  :roll:

Just my tuppence, but I hate seeing folk spend good money on things they've been convinced are great by the people that make 'em or by less than objective magazines....

As has been said before, when doing owt to your cars or engines ask yourself what is the actual problem your trying to solve. Then ask yourself how will it affect everything else.  :wink:

cheers
 8)
Eeyore

Tyke:

--- Quote ---When the exhaust port is open and expecting to exhale, it gets met by a pulse of exhaust gas coming the other way
--- End quote ---


Not rocket science to suss out the correct length of pipe to ensure a negative 'pulse' is sat behind the valve just as it opens . . . just an understanding of the mechanics involved and a bit of mathematics . . . . . However, in practice, it starts to limit the usable rev range of a motor so most standard designs are a compromise to make as wide a usable rev range as possible . . . i dont think designers forget about the pulse timing at all . . . it's more likely an intentional thing to make the engine tractable over a much wider rev range. Not everyone wants a factory racer, in fact very few would want one if they knew how difficult they can be to drive.

Gas flowing and exhaust tuning is really good way to get more from a motor but just be aware of the narrow ranges of power that you can end up with.

Eeyore:

--- Quote from: "Tyke" --- . . . i dont think designers forget about the pulse timing at all . . . it's more likely an intentional thing to make the engine tractable over a much wider rev range. .
--- End quote ---


That was supposed to my point exactly!  :oops:  :wink:

The factory designers have to build the thing to work over a broad range of revs and torque demands and to meet specific NVH requirements, spending many happy hours describing pulse flows (not a job I envy). It's the after-market people I was having a pop at for building some thing that looks nice but usually fails to do the percribed job in one way or another  :wink:

As you rightly say, a bit of mod work on the standard manifolds can do wonders, if it's required.

cheers
 8)
Eeyore

Range Rover Blues:
Well the double S system has all the header different lengths anyway.  If you want to see a proper tubular exhaust for the V8 look no further than the TVR.  They have some clever reverse cone thingy in the exhaust that stops the back pulsing, quite clever.  Expensive though :?

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