Anybody care to elobrate what are the advantages if any that an 8 valve engine would have over a 16 Valve engine.

A mate is trying to convince me that the 8 Valver can be reved out more.

Asuming both Engines are going to see the same ammount of boost. And both engines are going to have their heads moded and ported.

i.e. 10-20 PSI.

 

less things to brake on the 8 valve. sorry i dont know much.

 

are you talking about d series?

A head is a head, and it depends on how its combustion chamber is designed and the shape of its ports. You have to take it on a case by case basis. Think, people still make the toyota 22r series into horsepower monsters.

Now, speaking of the d15b8 8 valve head, this head is the same casting as 88-95 d15 and d16a6 except it doesn't have the other two valves per cylinder machined in and it has a spacer in the valvetrain where the rockers should be. The only advantage i could possibly think of with this head is it may have a little bit better low low end torque....but it simply cannot rev, seriously, it struggles to climb past 5k. So d series 8 valve < any other 16 valve d series.

 

If the 8 valve engine that your friend is speaking of has mechanical lifters and not hydraulic lifters than this would be true because on an enigne with hydraulic lifters, at high rpms the valve lifters can lose contact with cam lobes. This is called valve float. This can cause damage to the valve train. But remember an engines power is limited by its breathing ability. So I think the 16 valve engine will probably make more power considering that both engines are at the same boost levels.

 

Valve float is when the valve springs dont pull the valves back to the seats fast enough at high rpms mate. Also, the hydraulic lifters are above the valves not the cam lobe. The lifters collapsing would cause the valves not to open or open not as far, but the hydraulic system is definitely a downside to high rpm design.

 

Lol, I thought this was about volkswagen motors.

 

d15b8 ports are pee hole sized where as the 16 valve heads are virgin ----- sized


on the same head with same port size the 4 valves will outflow the 2 valves
the max rpm depends on your valvetrain

 

a little info.
the 8 valve motor has all 98 tork at 2K rpm
the 16 valve has 98 tork at 5K rpm

BTW the 8 valve has the thottle body size of a dick.

 

The engine being discused is a swift.
Also asuming both have had their heads ported and worked on.

So the 8 Valvers have more TOrque.
So all we need to beat the 16 valvers is more boost right.

I belive his point was that the springs and the load on the springs is far more on the 16 valvers so they suffer from valve float sooner. WHere as the 8 Vlavers dont so you can rev them out more.