Dave Plowman (News) wrote:
In article ,
The Natural Philosopher wrote:
However, tuning the
exhaust system gives lesser results in comparison with the effects of
tuning the input system (by quite a lot).

Another sweeping generalisation that is only correct 50% of the time.


But a true one. Exhaust gases are under highish pressure. Inlet merely -
at best - atomospheric. On the cylinder head and inlet manifold attention
to the inlet tract by reducing restrictions etc that shouldn't be there
but are due to the costs of removing them in manufacture, etc will pay far
more dividends than the same work carried out on the exhaust ports. And
most production cars are already fitted with free (enough) flowing
exhausts.

Not at all. Certainly in my tuning days, the SINGLE most effective way
to increase power in MOST stock engines was to hit the exhaust first.

On my old Triumph Spitfire, the gains were well known. about 10bhp
increase from a free flow exhaust, then about 7-8 from fitting bigger
carbs, and a hotter cam, and then another 5 from fitting gas flowed
head, manifold and webers rather than SU's. I went as far as a fast road
cam, better carbs, and better exhaust. Still go that car. Must get it
back on the road some day..

Similar results on BMC A series engines.

The situation was almost reversed on B series BMC engines - that engine
had a ghastly cylinder head and no amount of anything made much
difference until that was re-ported and gas flowed with better valving.

Gas flow is all about removing the major bottle necks first. If you
think exhaust is irrelevant stuff a potato in the exhaust pipe and see
how the power drops off;-)

In article ,
The Natural Philosopher wrote:
Not at all. Certainly in my tuning days, the SINGLE most effective way
to increase power in MOST stock engines was to hit the exhaust first.

That's why I said *modern* production cars. Many older ones had extremely
poor manifolds and exhausts.

--
*Geeks shall inherit the earth *

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
The Natural Philosopher wrote:
Not at all. Certainly in my tuning days, the SINGLE most effective way
to increase power in MOST stock engines was to hit the exhaust first.

That's why I said *modern* production cars. Many older ones had extremely
poor manifolds and exhausts.

It seems to me that in many modern production cars the "performance
tuning" has already been done...

The message
from Chris Bacon contains these words:

It seems to me that in many modern production cars the "performance
tuning" has already been done...

Yes - and no. In many cases there's only minor differences between the
rip-snorting version and the grandad version - one is just a crippled
version of the other. Priced accordingly.

--
Skipweasel
Pay no attention to that man behind the curtain.

In article ,
Chris Bacon wrote:
It seems to me that in many modern production cars the "performance
tuning" has already been done...

Indeed. Unless it's a turbo where you can simply wind up the boost, it's
extremely expensive to get a meaningful power increase on most modern
engines.

--
*Aim Low, Reach Your Goals, Avoid Disappointment *

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
In article ,
Chris Bacon wrote:
It seems to me that in many modern production cars the "performance
tuning" has already been done...

Indeed. Unless it's a turbo where you can simply wind up the boost, it's
extremely expensive to get a meaningful power increase on most modern
engines.

Oh, no rechipping will net you lots..at the expense of dire fuel economy
usually. Especially if there is a turbo you can screw the waste gate
down on

In article ,
The Natural Philosopher wrote:
Indeed. Unless it's a turbo where you can simply wind up the boost,
it's extremely expensive to get a meaningful power increase on most
modern engines.

Oh, no rechipping will net you lots..at the expense of dire fuel economy
usually.

Not on any decent car, it won't. Only those where there are identical
engines of differing power outputs where the power is set by the
electronics - and these are usually diesels.

Especially if there is a turbo you can screw the waste gate
down on

That's what I said above. Although you might well shorten the service life
of the engine.

--
*Experience is something you don't get until just after you need it *

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
In article ,
The Natural Philosopher wrote:
Indeed. Unless it's a turbo where you can simply wind up the boost,
it's extremely expensive to get a meaningful power increase on most
modern engines.

Oh, no rechipping will net you lots..at the expense of dire fuel economy
usually.

Not on any decent car, it won't. Only those where there are identical
engines of differing power outputs where the power is set by the
electronics - and these are usually diesels.

Especially if there is a turbo you can screw the waste gate
down on

That's what I said above. Although you might well shorten the service life
of the engine.


Oh definitely...

I think the point I meant to make is that a commercial engine is
optimised for other things than raw power..flexibility, ease of
starting, fuel economy, emissions, noise and pure packaging concerns as
well as long service life may all be compromised by trying to 'extract
the max'

With fuel injection, you HAVE to remap if you start playing around with
alteration to the exhaust, valve timing and inlet tracts.

There is at least one installation - forget which one, which is 5bhp
down on an identical engine fitted to another model. The difference
purely being in the packaging of the exhaust manifold and pipework.

Every tuner knows that if you slap a nice trumpet without (much) air
filters on an engine, and put an optimised and really noisy exhaust on
it, shove in a high overlap cam, and dump as much fuel into it as
possible, a normal car engine can develop about twice the power, at the
expense of appalling idling, appalling noise, appalling fuel economy,
and a very short but colorful life.

If you also skim the head, and shove 5 star in it, it gets even better. :-)

I suppose your point, that there are no appallingly BAD installations
these days that can be EASILY upgraded by SIMPLE changes is also valid.

stuffing 5 star in, being the case in point.