revtothelimit - motorbike forum

Tbf the 5vy was bonkers everywhere. All through the range. It was just a bit more bonkers at the top end.

weeksy wrote: Sun Jan 24, 2021 10:20 am Tbf the 5vy was bonkers everywhere. All through the range. It was just a bit more bonkers at the top end.

Press raved about the GSX-R1000 and the 5VY seemed to take 2nd best but having owned both at the time the 5VY won me over.
I ended up doing more miles on track than road with it in the end and it was the perfect tool and as you say, the top end rush was great. The only bike I've owned that I actually felt full control of and certainly helped my riding improve. Unfortunately divorce etc meant I needed to free up some cash at the time so I sold it to a good friend of mine, he then sold it when he emigrated to Oz and I didn't have the money to buy it back at the time - gutted....

Beancounter wrote: Sat Jan 23, 2021 9:20 pmNumpty question, why does the number of valves affect the top end/bottom end?

As an owner of a less than cutting edge 2V Ducati motor, which I much prefer to the more powerful 4V water-cooled versions, this is a question I've pondered before.

As Mr Dazzle said, having smaller, lighter valves allows more extreme engine tuning including more aggressive cam timing/profiles, which, as a byproduct, results in a peakier motor. But there is also some physics at work around the valve sizes themselves. The important thing to consider is gas velocity and the mixing of the fuel/air at various engine speeds.

At low engine revs, although a single intake valve restricts gas flow when compared to a multi-valve arrangement, this restriction results in an increase in gas velocity, (think putting your thumb over a hosepipe to increase the speed of the water jet), and that gives better gas mixing and better cylinder filling.

With a second intake valve open at low revs, gas velocity drops considerably, resulting in less efficient cylinder filling and less torque.

The other side of the coin, of course, is that, at high revs, because the valves are open so briefly you want to cram as much charge into the cylinders as possible, which requires as large an intake area as possible . This is where a multi-valve layout is better.

In theory, an engine with one intake valve at low revs and two at high revs should give you the best of both worlds. Honda's VTEC system on the VFR800 was designed to do this but the benefits never seemed to justify the additional complexity.

You can also mimic the two-valve/four valve switch without deactivating any valves by using variable cam profiles - one profile give low valve lift at low revs, (restricting gas flow and increasing gas velocity), and the other profile gives high lift at high revs, maximising gas volume.

v8-powered wrote: Sun Jan 24, 2021 10:48 am

weeksy wrote: Sun Jan 24, 2021 10:20 am Tbf the 5vy was bonkers everywhere. All through the range. It was just a bit more bonkers at the top end.

Press raved about the GSX-R1000 and the 5VY seemed to take 2nd best but having owned both at the time the 5VY won me over.
I ended up doing more miles on track than road with it in the end and it was the perfect tool and as you say, the top end rush was great. The only bike I've owned that I actually felt full control of and certainly helped my riding improve. Unfortunately divorce etc meant I needed to free up some cash at the time so I sold it to a good friend of mine, he then sold it when he emigrated to Oz and I didn't have the money to buy it back at the time - gutted....

What year is the 5VY?

Yorick wrote: Sun Jan 24, 2021 12:15 pm

v8-powered wrote: Sun Jan 24, 2021 10:48 am

weeksy wrote: Sun Jan 24, 2021 10:20 am Tbf the 5vy was bonkers everywhere. All through the range. It was just a bit more bonkers at the top end.

Press raved about the GSX-R1000 and the 5VY seemed to take 2nd best but having owned both at the time the 5VY won me over.
I ended up doing more miles on track than road with it in the end and it was the perfect tool and as you say, the top end rush was great. The only bike I've owned that I actually felt full control of and certainly helped my riding improve. Unfortunately divorce etc meant I needed to free up some cash at the time so I sold it to a good friend of mine, he then sold it when he emigrated to Oz and I didn't have the money to buy it back at the time - gutted....

What year is the 5VY?

2004 to 2007 from memory....

I've got a feeling that 5 valve Yamahas have less valve area but more circumference than 16 valve engines, but I can't be arsed to look up the valve sizes and work out the (fairly simple) maths.

Its not as simple as you might think, cause poppet valves don't fully open so you would need to subtract the 'blockage' from the valve itself....which in turn is a function of the valve shape and lift.

I think beancounter's Q has been answered though.

It's hardly a secret that more valves equals more power.
Also that a 2 stroke makes shit loads more power than a 4 stroke.

So Honda excelled themselves with 8 valves per cylinder and almost matched the 500 2 strokes for power

Yorick wrote: Sun Jan 24, 2021 4:28 pm It's hardly a secret that more valves equals more power.
Also that a 2 stroke makes shit loads more power than a 4 stroke.

So Honda excelled themselves with 8 valves per cylinder and almost matched the 500 2 strokes for power

The NR500, didn't Rob Haslam get lapped on it?

Le_Fromage_Grande wrote: Sun Jan 24, 2021 6:06 pm

Yorick wrote: Sun Jan 24, 2021 4:28 pm It's hardly a secret that more valves equals more power.
Also that a 2 stroke makes shit loads more power than a 4 stroke.

So Honda excelled themselves with 8 valves per cylinder and almost matched the 500 2 strokes for power

The NR500, didn't Rob Haslam get lapped on it?

His cousin, Ron

Yorick wrote: Sun Jan 24, 2021 6:25 pm

Le_Fromage_Grande wrote: Sun Jan 24, 2021 6:06 pm

Yorick wrote: Sun Jan 24, 2021 4:28 pm It's hardly a secret that more valves equals more power.
Also that a 2 stroke makes shit loads more power than a 4 stroke.

So Honda excelled themselves with 8 valves per cylinder and almost matched the 500 2 strokes for power

The NR500, didn't Rob Haslam get lapped on it?

His cousin, Ron

I suspect auto correct

This popped up on my Youtube feed and as there were a few questions about five valve heads and this goes into some technical details I thought some people might find it interesting.
Ignore the first few seconds with the bloody irritating music cos the bloke is pretty good.



On about valves though, a bloke I worked with a while ago has a tuned Lancia turbo engine with sodium filled exhaust valve stems which as I understand it undergoes a phase transfer from solid to gas and back to a liquid and good for transferring a lot of heat from the exhaust valve to the valve guides and so into the oil where its taken away from the head.

I emember that back in the early 90s (?) Yamaha were making engines for one of the F1 teams (can't remember which). They were bigly touting the benefits of their 5 valve heads over the other team's 4V heads, when in fact the F1 engine only ever used 4V heads. The power of marketing...

demographic wrote: Tue Apr 20, 2021 7:06 pm On about valves though, a bloke I worked with a while ago has a tuned Lancia turbo engine with sodium filled exhaust valve stems which as I understand it undergoes a phase transfer from solid to gas and back to a liquid and good for transferring a lot of heat from the exhaust valve to the valve guides and so into the oil where its taken away from the head.

Sodium valves are reasonably common now. Like a lot of these things they started out mostly in aircraft, up until the 1940s the main driver of piston engine technology was aircraft for obvious reasons. Much of what we think of as race type stuff started out with the big budgets of aircraft powerplants from people like Rolls-Royce etc.

Quite right about the phase transfer though. Making something turn from a solid to a liquid or a liquid to a gas (or vice versa) involves a lot more energy than just heating it up/cooling it down. I can't recall the figures for sodium, but for water if you say it takes "1" unit of energy to heat it by 1°C it takes 7 units to push it over the boundary of liquid to gas. I.e. when you hit 100°C it takes a shit load more energy to then get to 101°C and turn to steam.

This effect can give two advantages, first it means you can absorb or reject a lot more heat in a given space and second it provides a sort of stabilisation effect. Once the sodium starts boiling at it's temperature won't increase - you just increase the rate at which is boils off - until it's ALL gas. So you end up in a situation where you have a pocket of liquid sodium which can keep sucking heat out of the valve without getting any hotter, thus providing cooling and a steam of gaseous sodium moving up the valve.

The opposite effect occurs at the top of the valve - the gaseous sodium dumps a lot of energy into the top end of the valve as it re-condenses.

https://en.wikipedia.org/wiki/Heat_pipe

EDIT: DUnno where I got the factor of 7 from, it didn't sound right so I checked. It's way more than that, like 100 times more.

Yamaha made engines for Ford at one point, iirc the 1.7 Puma had a Yamaha lump... or at least a Ford lump breathed on by Yamaha.

KungFooBob wrote: Tue Apr 20, 2021 7:51 pm Yamaha made engines for Ford at one point, iirc the 1.7 Puma had a Yamaha lump... or at least a Ford lump breathed on by Yamaha.

The Volvo XC90 V8 was a Ford-aha engine - it's very heavily breathed on to make the engine in the Noble M600.

Mr. Dazzle wrote: Tue Apr 20, 2021 7:50 pm Quite right about the phase transfer though. Making something turn from a solid to a liquid or a liquid to a gas (or vice versa) involves a lot more energy than just heating it up/cooling it down. I can't recall the figures for sodium, but for water if you say it takes "1" unit of energy to heat it by 1°C it takes 7 units to push it over the boundary of liquid to gas. I.e. when you hit 100°C it takes a shit load more energy to then get to 101°C and turn to steam.

This effect can give two advantages, first it means you can absorb or reject a lot more heat in a given space and second it provides a sort of stabilisation effect. Once the sodium starts boiling at it's temperature won't increase - you just increase the rate at which is boils off - until it's ALL gas. So you end up in a situation where you have a pocket of liquid sodium which can keep sucking heat out of the valve without getting any hotter, thus providing cooling and a steam of gaseous sodium moving up the valve.

The opposite effect occurs at the top of the valve - the gaseous sodium dumps a lot of energy into the top end of the valve as it re-condenses.

https://en.wikipedia.org/wiki/Heat_pipe

EDIT: DUnno where I got the factor of 7 from, it didn't sound right so I checked. It's way more than that, like 100 times more.

IIRC steel undergoes a structure/phase change* as it heats up and the first one is when the austenite starts to form and another when the austenite is fully formed.
I can't remember which (I assume its the upper cos ferrite is magnetic and austenite isnt) but it stops being attracted to a magnet on one of those critical arrest points.
During those changes it requires a good deal more energy to increase temperature than otherwise.

Not something I really know a huge amount about though, a few of my weld inspection courses touched upon it.

KungFooBob wrote: Tue Apr 20, 2021 7:51 pm Yamaha made engines for Ford at one point, iirc the 1.7 Puma had a Yamaha lump... or at least a Ford lump breathed on by Yamaha.

The block is a Zetec SV lump, the rest of it was designed by Yamaha, the Racing Puma supposedly makes another 25 bhp, but having driven both there's sod all difference in how they go.

The most powerful Pumas were the 1.6 rally cars, which were all Ford

Yamaha did a lot of design work for Toyota, though it's tricky to know where Yamaha stops and Toyota starts.

I got a run on an original R1 when they came out. Bonkers, but I preferred my RU Exup as it felt more solid and planted. Years later I rode a 2000 model back to back with an SRAD and preferred the SRAD as it felt like an RGV compared to the R1. Then I rode a GSXR1000 and it's still the most bonkers thing I've ever ridden on the road.

Iconic bike, the R1, but the 80s and 90s gave us an iconic bike practically every year.