Hmm, didn't NickF do this?
UIM honing?
Have seen in one or two posts on here whilst searching thru, people mentioning getting their UIM honed...sounds like it'd cost more than just getting an st200 jobbie, but does anyone actually know what it costs and who might be able to do it?
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You may be right there Simon, i'll have to try contacting him if he's still on here, see what he may be able to say on the subject. You cracking on with the rebuild today mate?
Nick had an ST200 UIM optimised. Not sure what else was done to it, but i know he started with the ST UIM
Now that seems to make a lot more sense, optimising the openings etc on an already honed ie ST200 UIM seems more like it. Will keep searching for a bargain priced ST200 UIM myself then, few about but not enough cash in the pot just now to do the bushes, exhaust AND performance mods.
Cheers for that input Ben_W
Lee
Cheers for that input Ben_W
Lee
http://en.wikipedia.org/wiki/Cylinder_head_porting
The "Porting and Polishing" myth
It is popularly held that enlarging the ports to the maximum possible size and applying a mirror finish is what porting is. However that is not so. Some ports may be enlarged to their maximum possible size (in keeping with the highest level of aerodynamic efficiency) but those engines are highly developed very high speed units where the actual size of the ports has become a restriction. Larger ports flow more fuel/air at higher RPM's but sacrifice torque at lower RPM's due to lower fuel/air velocity. A mirror finish of the port does not provide the increase that intuition would suggest. In fact, within intake systems, the surface is usually deliberately textured to a degree of uniform roughness to encourage fuel deposited on the port walls to evaporate quickly. A rough surface on selected areas of the port may also alter flow by energizing the boundary layer, which can alter the flow path noticeably, possibly increasing flow. This is similar to what the dimples on a golf ball do. Flow bench testing shows that the difference between a mirror finished intake port and a rough textured port is typically less than 1%. The difference between a smooth to the touch port and an optically mirrored surface is not measurable by ordinary means. Exhaust ports may be smooth finished because of the dry gas flow and in the interest of minimizing exhaust by-product build-up. A 300 - 400 Grit finish followed by a light buff is generally accepted to be representative of a near optimal finish for exhaust gas ports.
The reason that polished ports are not advantageous from a flow standpoint is that at the interface between the metal wall and the air, the air speed is ZERO (see boundary layer and laminar flow). This is due to the wetting action of the air and indeed all fluids. The first layer of molecules adheres to the wall and does not move significantly. The rest of the flow field must shear past which develops a velocity profile (or gradient) across the duct. In order for surface roughness to impact flow appreciably, the high spots must be high enough to protrude into the faster moving air toward the center. Only a very rough surface does this
The "Porting and Polishing" myth
It is popularly held that enlarging the ports to the maximum possible size and applying a mirror finish is what porting is. However that is not so. Some ports may be enlarged to their maximum possible size (in keeping with the highest level of aerodynamic efficiency) but those engines are highly developed very high speed units where the actual size of the ports has become a restriction. Larger ports flow more fuel/air at higher RPM's but sacrifice torque at lower RPM's due to lower fuel/air velocity. A mirror finish of the port does not provide the increase that intuition would suggest. In fact, within intake systems, the surface is usually deliberately textured to a degree of uniform roughness to encourage fuel deposited on the port walls to evaporate quickly. A rough surface on selected areas of the port may also alter flow by energizing the boundary layer, which can alter the flow path noticeably, possibly increasing flow. This is similar to what the dimples on a golf ball do. Flow bench testing shows that the difference between a mirror finished intake port and a rough textured port is typically less than 1%. The difference between a smooth to the touch port and an optically mirrored surface is not measurable by ordinary means. Exhaust ports may be smooth finished because of the dry gas flow and in the interest of minimizing exhaust by-product build-up. A 300 - 400 Grit finish followed by a light buff is generally accepted to be representative of a near optimal finish for exhaust gas ports.
The reason that polished ports are not advantageous from a flow standpoint is that at the interface between the metal wall and the air, the air speed is ZERO (see boundary layer and laminar flow). This is due to the wetting action of the air and indeed all fluids. The first layer of molecules adheres to the wall and does not move significantly. The rest of the flow field must shear past which develops a velocity profile (or gradient) across the duct. In order for surface roughness to impact flow appreciably, the high spots must be high enough to protrude into the faster moving air toward the center. Only a very rough surface does this
[quote name=Terry Haines]
http://en.wikipedia.org/wiki/Cylinder_head_porting
The "Porting and Polishing" myth
It is popularly held that enlarging the ports to the maximum possible size and applying a mirror finish is what porting is. However that is not so. Some ports may be enlarged to their maximum possible size (in keeping with the highest level of aerodynamic efficiency) but those engines are highly developed very high speed units where the actual size of the ports has become a restriction. Larger ports flow more fuel/air at higher RPM's but sacrifice torque at lower RPM's due to lower fuel/air velocity. A mirror finish of the port does not provide the increase that intuition would suggest. In fact, within intake systems, the surface is usually deliberately textured to a degree of uniform roughness to encourage fuel deposited on the port walls to evaporate quickly. A rough surface on selected areas of the port may also alter flow by energizing the boundary layer, which can alter the flow path noticeably, possibly increasing flow. This is similar to what the dimples on a golf ball do. Flow bench testing shows that the difference between a mirror finished intake port and a rough textured port is typically less than 1%. The difference between a smooth to the touch port and an optically mirrored surface is not measurable by ordinary means. Exhaust ports may be smooth finished because of the dry gas flow and in the interest of minimizing exhaust by-product build-up. A 300 - 400 Grit finish followed by a light buff is generally accepted to be representative of a near optimal finish for exhaust gas ports.
The reason that polished ports are not advantageous from a flow standpoint is that at the interface between the metal wall and the air, the air speed is ZERO (see boundary layer and laminar flow). This is due to the wetting action of the air and indeed all fluids. The first layer of molecules adheres to the wall and does not move significantly. The rest of the flow field must shear past which develops a velocity profile (or gradient) across the duct. In order for surface roughness to impact flow appreciably, the high spots must be high enough to protrude into the faster moving air toward the center. Only a very rough surface does this
[/quote]
Didnt really understand all of it but go0 the gist. And what and explaination! :L
http://en.wikipedia.org/wiki/Cylinder_head_porting
The "Porting and Polishing" myth
It is popularly held that enlarging the ports to the maximum possible size and applying a mirror finish is what porting is. However that is not so. Some ports may be enlarged to their maximum possible size (in keeping with the highest level of aerodynamic efficiency) but those engines are highly developed very high speed units where the actual size of the ports has become a restriction. Larger ports flow more fuel/air at higher RPM's but sacrifice torque at lower RPM's due to lower fuel/air velocity. A mirror finish of the port does not provide the increase that intuition would suggest. In fact, within intake systems, the surface is usually deliberately textured to a degree of uniform roughness to encourage fuel deposited on the port walls to evaporate quickly. A rough surface on selected areas of the port may also alter flow by energizing the boundary layer, which can alter the flow path noticeably, possibly increasing flow. This is similar to what the dimples on a golf ball do. Flow bench testing shows that the difference between a mirror finished intake port and a rough textured port is typically less than 1%. The difference between a smooth to the touch port and an optically mirrored surface is not measurable by ordinary means. Exhaust ports may be smooth finished because of the dry gas flow and in the interest of minimizing exhaust by-product build-up. A 300 - 400 Grit finish followed by a light buff is generally accepted to be representative of a near optimal finish for exhaust gas ports.
The reason that polished ports are not advantageous from a flow standpoint is that at the interface between the metal wall and the air, the air speed is ZERO (see boundary layer and laminar flow). This is due to the wetting action of the air and indeed all fluids. The first layer of molecules adheres to the wall and does not move significantly. The rest of the flow field must shear past which develops a velocity profile (or gradient) across the duct. In order for surface roughness to impact flow appreciably, the high spots must be high enough to protrude into the faster moving air toward the center. Only a very rough surface does this
[/quote]
Didnt really understand all of it but go0 the gist. And what and explaination! :L
Very good explanation Terry, so leaving the ultimate question, in your experience of working with these engines, if was to proceed as planned on obtaining an SVT UIM, would that generally speaking lose me some low end grunt at the expense of top end, or is the standard V6 UIM particularly bad and generally restrictive accross the usable RPM range?
Lee,
I don't think what is true of inlet ports is exactly true of inlet manifolds as inlet manifolds are further up the chain, longer in "runner" length and don't carry fuel.
It's late now but I could try and find some dyno charts I saw of the SVT UIM vs standard. The difference is quite small in ultimate BHP but actually there was a torque gain from the midrange and up, almost contrary to what is being implied above.
I think given how complex the scenario is and how many variables there are, not least personal preference and driving style it's best to look at people's personal experiences and dyno charts and draw conclusions from the evidence.
Simon
I don't think what is true of inlet ports is exactly true of inlet manifolds as inlet manifolds are further up the chain, longer in "runner" length and don't carry fuel.
It's late now but I could try and find some dyno charts I saw of the SVT UIM vs standard. The difference is quite small in ultimate BHP but actually there was a torque gain from the midrange and up, almost contrary to what is being implied above.
I think given how complex the scenario is and how many variables there are, not least personal preference and driving style it's best to look at people's personal experiences and dyno charts and draw conclusions from the evidence.
Simon
I'm looking forward to seeing how my secondary ports and knife-edged butterflies are working but I'm not going to take my car over 3800rpm so soon after the rebuild! :}
An interesting example of different inlet manifolds is in the E36 straight 6 BMW engines. The 323 is a 2.5L inline 6 with 170bhp. The 325 is the same engine with 192bhp. The difference is the inlet manifold, which was made to be restrictive for the 323. By personal accounts the 323 is a quick car and not really much noticeably slower than the 325. They BOTH have decent midrange power and the less restrictive manifold doesn't ruin that much at all, as long as the car is well mapped. I don't know how this compares to our engines but we know a LOT of other tweaks made the power difference... a lot is in the mapping according to Terry Haines 
Took my brother's 323 for a test drive yesterday, just to see how it performed compared to my ST24 (similar power output etc).
I know this isn't the right comparison for this discussion but it felt more torquey across the midrange compared to my Mondeo.
I know this isn't the right comparison for this discussion but it felt more torquey across the midrange compared to my Mondeo.
Most all std engines that have a bigger t/body,bigger intake manifold,larger valves or a hot cam etc tend to make HP higher up the rev range.The engine is looking for a 'sweet spot' when the velocity of the gas filling the cylinders is at it's max.Bigger T/body etc all slow down velocity. In older engines, before we were able to design ports etc on CAD it was hit and miss and in most cases ports etc were too small. That is why so many older V8's benefit from porting,bigger valves etc., Those days are long gone..
BMW straight 6 engines are very torquey on paper, and peak torque is achieved quite low down compared to ours. Frankly they're better engines but obviously we're not powerless to improve ours a bit.thegfb said:Took my brother's 323 for a test drive yesterday, just to see how it performed compared to my ST24 (similar power output etc).
I know this isn't the right comparison for this discussion but it felt more torquey across the midrange compared to my Mondeo.
FWIW I test-drove a similar aged 325 (E36 shape) with the 192bhp engine once and it actually felt slower than my mk1, but maybe that's just because mine has the louder exhaust and air filter thus making the experience more exciting. I must admit, though, it stuck to the road amazingly well for a non-sporty and bog-standard car!!
[quote name=Terry Haines]Most all std engines that have a bigger t/body,bigger intake manifold,larger valves or a hot cam etc tend to make HP higher up the rev range.The engine is looking for a 'sweet spot' when the velocity of the gas filling the cylinders is at it's max.Bigger T/body etc all slow down velocity. In older engines, before we were able to design ports etc on CAD it was hit and miss and in most cases ports etc were too small. That is why so many older V8's benefit from porting,bigger valves etc., Those days are long gone..[/quote]
Informative post
What do you make of Motorman's high velocity inlet porting, making inlet ports ~65% of valve diameters?
I was tempted to do it to mine but didn't fancy the risk to be honest.
Simon
Informative post
What do you make of Motorman's high velocity inlet porting, making inlet ports ~65% of valve diameters?
I was tempted to do it to mine but didn't fancy the risk to be honest.
Simon
Straight 6 engines are about 'the' best for balance and 'guts' Re BMW, older Jag, my old Ford USA F-150 truck with the straight 6 4.9L motor..they all run for ever and will bull the side of a house down..same with straight 6 diesels..
On smaller ports, yes motoman makes a lot of good points and is 100% correct. The size reduction ,to my mind, is a little more than I would do but his science and engineering is bang on. Ask people who work at Cosworth, Riccardo etc..most of us powertrain/ combustion engineers have known this for all our working lives..as did people like Sir Harry Ricardo..the physics does not change...
Example..some cars in the early 70's that had a 'high power' opetion engine of the same size but higher HP usually had SMALLER intake vales!!..I did a study of this mannnnnnnnnnnnnnny..yeas ago and it was common!! Food for thought..and no, bigger is not always better..Understaind gas flow dynamics etc and velocity ..you will see it is far more important that CFM on a 'low tech' flow bench!!!
On smaller ports, yes motoman makes a lot of good points and is 100% correct. The size reduction ,to my mind, is a little more than I would do but his science and engineering is bang on. Ask people who work at Cosworth, Riccardo etc..most of us powertrain/ combustion engineers have known this for all our working lives..as did people like Sir Harry Ricardo..the physics does not change...
Example..some cars in the early 70's that had a 'high power' opetion engine of the same size but higher HP usually had SMALLER intake vales!!..I did a study of this mannnnnnnnnnnnnnny..yeas ago and it was common!! Food for thought..and no, bigger is not always better..Understaind gas flow dynamics etc and velocity ..you will see it is far more important that CFM on a 'low tech' flow bench!!!
So what Motorman makes out as being new or inside information is maybe just the latter, to some degree :}
Very cool stuff.
With you on the straight six diesels, mate has one - a 530D, with remap and de-cat - and it's very quick and torquey (400lbs/ft)!
Very cool stuff.
With you on the straight six diesels, mate has one - a 530D, with remap and de-cat - and it's very quick and torquey (400lbs/ft)!
Yeah my mate has got the 535D M-Sport, when he first got it I thought 'you're a nob for getting a tractor' but it's amazingly powerful and quick, and bloody economical too
Most all of what motorman says is corrct.Tuners tend to ignore or not even know the basics of physics,combustion and thermodynamics. For example, petrol burns at the same speed at 500 RPM or 5000 RPM..the 'burn' is a chemical acton..a reason why we have ignition advance ..to give the fuel enough time to fully burn at higher RPM..it's a constant and cannot be messed with,it is what it is.Also higher octane fuels do not have any higher calorific value but have additives to burn SLOWER to prevent detonation, also things like cold air,damp air,EGR all,in one way or another 'add' octane..which again causes a slower burn but prevent det..When you get deep into the science it is all very much common sense. Problem is the tuners and speed shops want to sell bigger t/bodies,bigger valves etc etc...so why would they even explain the pure physics and science of combustion..they want your dosh!!
Dumb statements like..'the engine will breathe better' are only true if the engine was a bad design and started life with bad restrictions in the intake system..but it is a 'balance'..you need restrictions to give velocity but not so much as to choke off the engine, so to look at just flow volumes(CFM) is only half of the story.Bottom line..bigger is not always better so don't be brainwashed buy those who think it is...
Dumb statements like..'the engine will breathe better' are only true if the engine was a bad design and started life with bad restrictions in the intake system..but it is a 'balance'..you need restrictions to give velocity but not so much as to choke off the engine, so to look at just flow volumes(CFM) is only half of the story.Bottom line..bigger is not always better so don't be brainwashed buy those who think it is...
323's and 328's both feel more torquey and have better mid range, but lack top end, due to them having a 2.0 air intake system, as soon as theu get replaced for the 2.5 re-worked stuff, they gain 15bhp and lose their midrange pull but they have a lot beter top end, so i presume it will be the same for the mondeo manifolds
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