What does 'ported and flowed heads' mean?
Discussion
Pretty similar
Ported - the ports (big holes where manifolds join heads) are enlarged to improve volume of flow.
Gas flowed - the tubes that the fuel and exhaust flow through are machined so that the fluids can flow with less resistance hence faster, so more fuel gets pupmed in per stroke.
In a nutshell
Ported - the ports (big holes where manifolds join heads) are enlarged to improve volume of flow.
Gas flowed - the tubes that the fuel and exhaust flow through are machined so that the fluids can flow with less resistance hence faster, so more fuel gets pupmed in per stroke.
In a nutshell
It basically means subtely changing the geometry of the ports in a head. Involves rounding of port edges, polishing surfaces, widening ports that sort of thing. Anything that might improve flow through the ports, making the engine breath more freely. There is slightly more to it than that of course......
edited to say: blimey, folks are quick round here.....
MrSBC
>> Edited by MrSBC on Tuesday 27th April 09:53
edited to say: blimey, folks are quick round here.....
MrSBC
>> Edited by MrSBC on Tuesday 27th April 09:53
Generally meant to mean machining the inlet and exhaust ports (the bit between the exhaust/inlet manifold and the valves) to achieve a greater air flow when measured OFF the engine. This is then supposed to translate to a higher power output from the engine.
In reality it involves polishing the port to an impressive, but pointless mirror finish.
Ask yourself why the manufacturer doesn't simply make the ports bigger to start with.
In reality it involves polishing the port to an impressive, but pointless mirror finish.
Ask yourself why the manufacturer doesn't simply make the ports bigger to start with.
bor said:
Generally meant to mean machining the inlet and exhaust ports (the bit between the exhaust/inlet manifold and the valves) to achieve a greater air flow when measured OFF the engine. This is then supposed to translate to a higher power output from the engine.
In reality it involves polishing the port to an impressive, but pointless mirror finish.
Ask yourself why the manufacturer doesn't simply make the ports bigger to start with.
Cost? not needed for the cars intended application.
If anyone is interested and would like to see proof that proper gas flowing does work, I have figures for my Delta's head and inlet manifold from a flow bench before and after it was done, as component parts and assemblies. Makes interesting viewing.
First off, P,
maybe it did work in your case, who's to say it doesn't ?. But you're making a fundamental mistake in equating results from a flow bench to results on the engine. If you increase the size of a hole, then on a flow rig you can obviously flow more air through it, basic fluid dynamic. The problem is that the flow bench does not necessarily equate to what's happening in the engine. Think of it this way, if you empty a bath of water through the plug hole it will take x seconds. If you double the size of the drain then the water will drain more quickly. There comes a point however when further increasing the size of the drain has no effect, can you visualize that ?
Like I say, maybe porting works in some cases, but the manufacturers have huge resources to optimize the ports and chase every performance gain that they can.
maybe it did work in your case, who's to say it doesn't ?. But you're making a fundamental mistake in equating results from a flow bench to results on the engine. If you increase the size of a hole, then on a flow rig you can obviously flow more air through it, basic fluid dynamic. The problem is that the flow bench does not necessarily equate to what's happening in the engine. Think of it this way, if you empty a bath of water through the plug hole it will take x seconds. If you double the size of the drain then the water will drain more quickly. There comes a point however when further increasing the size of the drain has no effect, can you visualize that ?
Like I say, maybe porting works in some cases, but the manufacturers have huge resources to optimize the ports and chase every performance gain that they can.
bor said:Not necessarily. If that extra x% of power costs a manufacturer £y per engine to achieve, the beancounters may decide that it is uneconomic. You may decide otherwise, so there is always room for improvement if you deem the cost / benefit to be acceptable.
Like I say, maybe porting works in some cases, but the manufacturers have huge resources to optimize the ports and chase every performance gain that they can.
For example, the Corrado VR6 was intended to have a variable inlet manifold to give more torque low-down and more bhp higher up the rev range. The beancounters decided it would put £1000 on the price of an already expensive car and decreed that it would not be standard equipment. Or, indeed, an option (which was a pity).
However, rather than wasting the development effort, VW Motorsport initially sold it as an aftermarket item and then sold the design to Schrick. You can by the Schrick VSR as an aftermarket fit for £1500 + VAT but not many owners have had it fitted as the cost / benefit isn't great enough.
Sorry, I digressed a little bit there. But you get my point, I hope.
bor said:
There comes a point however when further increasing the size of the drain has no effect, can you visualize that ?
I think that may be incorrect... If you took the plughole to its maximum size (i.e. the size of the bath) then all the water would just drop straight out.
However, if this led to a drainpipe that couldn't take that much flow, then it would still back up.
The analogy hold for the engine in that you could increase the size of the ports and ensure a lovely smooth flow, but what goes in must come out, so eventually the exhaust will prove the limiting factor.
So then you invest in a free-er flowing exhaust and maybe an extractor manifold etc etc ad infinitum
Bor,
That is simply not the case. Manufacurers do not spend massive budgets chasing every performance gain they can. Only on high end cars would they bother doing it. Thats like saying fitting a tubular manifold doesnt gain any improvement over a std one, as the manufacturer must have designed it to the optimum. That is simply not true.
Manufacturers do a decent job, however they have to compromise, and build a car to do what it is needed to do, and too a budget.
The example you have mentioned regarding a bath doesnt make sense either. How can a larger hole not cope with a larger flow for any given pressure.
www.img31.photobucket.com/albums/v93/PeteS/inlet%20manifold/porting.jpg
Rgds
Pete
That is simply not the case. Manufacurers do not spend massive budgets chasing every performance gain they can. Only on high end cars would they bother doing it. Thats like saying fitting a tubular manifold doesnt gain any improvement over a std one, as the manufacturer must have designed it to the optimum. That is simply not true.
Manufacturers do a decent job, however they have to compromise, and build a car to do what it is needed to do, and too a budget.
The example you have mentioned regarding a bath doesnt make sense either. How can a larger hole not cope with a larger flow for any given pressure.
www.img31.photobucket.com/albums/v93/PeteS/inlet%20manifold/porting.jpg
Rgds
Pete
pdV6 said:
There comes a point however when further increasing the size of the drain has no effect, can you visualize that ?
I think that may be incorrect... If you took the plughole to its maximum size (i.e. the size of the bath) then all the water would just drop straight out.
That's the point. If you increased the plughole beyond the size of bath the water wouldn't drop out any quicker. Er, if you see what I mean.
JonRB said:
Not necessarily. If that extra x% of power costs a manufacturer £y per engine to achieve, the beancounters may decide that it is uneconomic. You may decide otherwise, so there is always room for improvement if you deem the cost / benefit to be acceptable.
Pete & Jon,
the economics argument is flawed in this case. The ports are eithe left as cast or are machined. The theoretical shape of the port has no influence on cost. If the port is machined by the manufacturer, then they can machine it to any shape they want. If it's cast, then it can be cast to near enough the shape they want. Polishing a cast port can tidy the port up, taking out casting tolerances, removing casting flash and burrs etc and in that case one could see an improvement, but it would be a lot of work for a limited gain.
psimpson7 said:
Bor,
No, because if the water was there it would flow out faster...
Guys, I'm changing the bath example to a shower. Sorry, the bath thing was a bit misleading.
One of those nice power showers on full blast. All the water going down the plughole. Plughole gets quadruppled in size. Any difference ?
Just going to get a sandwich. Back in 5.
bor said:
That's the point. If you increased the plughole beyond the size of bath the water wouldn't drop out any quicker. Er, if you see what I mean.
Only because then the limiting factor would be the shape of the bath... If you filled the bathroom with water floor to ceiling and pulled the larger-than-bath-size plug, then the limit would be the flow through the bath itself.
Engine analogy: the ports are larger than the inlet manifold pipes. Pointless!
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