5v engines

[SeventyNine]

how do they work?

by 5v enginesi mean, the vw 20vt engine or similar, where theres 5 valves per cylinder.

is it a case of 3 on one and 2 for the other?

or is it switchable maybe? where theres 3 inlet when accelerating and 3 outlet when deccelerating?

surely what goes in must come out therefore they would need to be the same all thye time.

[Keefy]

I'm pretty sure they are 3 inlets and 2 outlets.

[SeventyNine]

[Dave Dorson]

It's so they could get a better combusion chamber, they are more "dome" like than conventional multivalve engines.

I don't know all the ins and outs, but they work well

[Lewis]

As far as I know all current 5 valvers have 3 intake, 2 exhaust per cylinder. The exhaust valves are bigger (to maintain flow through the cylinder) but as with 2 versus 4 valve, the intake valves have a larger total area.

You can do lots of clever things with them, like opening the two outside intake valves early, before opening the central one to induce swirl in the chamber getting a better mix, more power and cleaner emissions. You can lose a little torque though, as the combustion chamber is an irregular shape, but it depends on how well you work on it

They haven't proven very advantageous however, so few manufactures actually go to the hassle of using them. Most just stick with the 4 valves per cylinder approach.

[SeventyNine]

how do they compare to the 16v vw engine when used in n/a guise?

20v on carbs is yet to be done ;D

[Lewis]

In reality I think you'll find little benefit with a 20v two litre over a 16 valve one

On an NA engine with 20 valves you'd have very rapid breathing at lower revs, you could impair low end torque quite nastily

Depends how you'd drive it I guess ;D

Toyota used 20 valves in their 4A-GE engines for a bit (silver tops, like you see in some kit cars). Most of 'em don't give more than 150HP on the dyno according to my EMS book, even with custom ECUs (but on stock cams).

I think there was one of those in PPC recently that got only like 160HP too. Pretty lame for a 20v compared to the 16v, for the added complication.

[spottedlaurel]

My experience of 20v non-turbo 1.8 was Passat was terrible - no torque, undergeared, errghhh. Turbo one I've driven since was much nicer.

[danblez]

Can I ask a stupid question and why do they use several round valves rather than one irregular shaped one of equal (or larger) surface area?

Edit* Having read the thread properley again maybe Lewisk has already answered my question

[Blown_Imp]

Oalve or square valves wonted work unless you also had a square valve stem aswell. This is because valves spin on their seats. This is what causes valve recession when a piece of the seat sticks to the valve andthe valve then grinds back into the head!

There was an 8 valve per cylinder honda engine years back, its was the most expensive bike theu ever produced. It also had an oval piston!

J

[Lewis]

Yea, remember reading about those.

I guess with strange-shape valves it'd be very hard (well, I'm sure you could do it but it'd take time) to get decent flow into the chamber without it just going every which way

[Blown_Imp]

A linear beaing assembly could be used on the valve stems, this would mean much higher cam veloties could be used compared to normal valves. I wonder if that would work?

Engines with barrel valves seem to work quite well, its good becuase the have so much less to go wrong. Its just a tube with some holes in it!

J

[quantum stop]

the bike in question with the spam tin shaped pistons was i think a honda vfr1000r a limited production run now highly sort after rode one once mountains of torque it had also they did do some funny shaped valves called "tulip" that were oval andy

[steve3]

impstop said:

the bike in question with the spam tin shaped pistons was i think a honda vfr1000r a limited production run now highly sort after rode one once mountains of torque it had also they did do some funny shaped valves called "tulip" that were oval andy

The road going, oval piston'ed Honda was the NR 750.


So expensive that there are still some crated, brand new, never sold.
It was developed from the GP500 racer which used the same oval piston idea.

Yamaha R1's have 5 valve, in fact Yam 750 and 1000 sports bikes have all had 5 valves since the FZ750 and FZR1000 back in the 80's.

[PhoenixC]

lewisk78 said:

In reality I think you'll find little benefit with a 20v two litre over a 16 valve one

On an NA engine with 20 valves you'd have very rapid breathing at lower revs, you could impair low end torque quite nastily

Depends how you'd drive it I guess ;D

Toyota used 20 valves in their 4A-GE engines for a bit (silver tops, like you see in some kit cars). Most of 'em don't give more than 150HP on the dyno according to my EMS book, even with custom ECUs (but on stock cams).

I think there was one of those in PPC recently that got only like 160HP too. Pretty lame for a 20v compared to the 16v, for the added complication.

But from a standard 1600 that is still not bad, especially considering the standard 4age will give 118bhp in an AE82 and 124bhp in an AE86 I remember chipped ones gave very little extra top end power but gained around 8bhp in the mid range.
For power gains cams make some of the biggest difference on a 4age.

[quantum stop]

vrf was the loose derivetiveof the nr in britain wern'tit

[Deleted]

Hmm, didnt those Atlantic Series 4age engines have 20v heads? And wasnt those 240 horsepowers at 11-12000rpm or something?

[PhoenixC]

madmaxx said:

Hmm, didnt those Atlantic Series 4age engines have 20v heads? And wasnt those 240 horsepowers at 11-12000rpm or something?

Not sure but very probably

I know the BTCC Corolla`s from `86 and `87 had between 220 and 240bhp. IIRC the first ones used the standard cast exhaust manifolds as well as they were fine upto 200bhp.

[CR500Dom]

impstop said:

vrf was the loose derivetiveof the nr in britain wern'tit

Nope.... nowhere near

The Later VFR used some of the styling cues from the NR but thats about it.

The VFR was the road going version of the RVF or RC30 engine, which was "The Daddy" of road racing/endurance racing in the 80/90`s, gear driven cam V4 that sounds superb at full chat on open pipes ;D

The NR was Honda Dick swinging, they wanted to get greater valve area and they couldnt increase number of pistons so they built a 4 cylinder "V8", with Oval pistons, 8 rods (2 per piston), and 32 valves (4 inlet - 4 exhaust per cylinder).....

They were £37,000 new there is one sitting in BAT motorcycles at biggin hill if you want to see one (Or there was last time I was down there)

The Iconic Ducati 916 and its designer were inspired by the NR750....... Tamburini has admitted it was that bike and the Cagiva GP500 that were his inspiration when doing the 916 ;D

[quantum stop]

i stnd corected mi memorys not like it was LOL