8 valves >< 16 valves

Vibez

Vibez

Vibez

Permabanned
Joined
29 Oct 2006
Posts
812
What exactly are 8valve engines?

For instance you can get 1.2 8v corsas and 1.2 16v corsas, 16 valves obviously have 4 cylinders, 4 valves per cylinder so I assume 8 valve engines have 2 cylinders, 4 valves per cylinder?

OR

Are 8v engines 4 cylinders with two valves per cylinder as opposed to 4?

Also, on a same chassis car, with a same capacity engine, is it true that 8 valves are generally more torquey than 16 valves and have more power lower down the rev range, and a 16 valve equivalent car will be pretty much the same 0 - 60 etc. but you have to rev the **** off it?

Cheers
 
16 valves provide better control over fuelling I would have thought which can provide more power ?
 
Last edited:
Wow a lot of replies very fast, didn't have time to ninja my OP for clarity before it was quoted hehe

kk cheers for the replies, if anyone wants to touch open whether equivalent 8v's will be more torquey through the rev range and if so, why I'd appreciate that too
 
Example of the difference 8v, 16v. If you look at the BHP and torque, the 16v is much better than the 8v. They may not be true figures, but that gives you an idea as to the difference. Both of them are 2004 Renault Clios with 1.2L engines.

InvG
 
imagine you are looking straight down at a cylinder. it is a circle (unless you own a certain bike or two... ;)).

you need to get as much air as possible in and out of the cylinder to make power.

you can have two valves (one inlet, one exhaust)...but if you increase that to four smaller valves, you get a greater surface area and therefore more flow.

hope that makes sense...think of it like this - four 1p coins have more area than two 2p coins.

*n
 
InvaderGIR said:
Example of the difference 8v, 16v. If you look at the BHP and torque, the 16v is much better than the 8v. They may not be true figures, but that gives you an idea as to the difference. Both of them are 2004 Renault Clios with 1.2L engines.

InvG
Click to expand...

Yes, but if you look at those figures, there is one other difference - the 8v produces its maximum torque at 2500 rpm, as opposed to 3500 for the 16v.

I've preveiously owned a 2.0 8v Cavalier, and a 2.0 16v Vectra, and while the Vectra was definitely quicker, the Cav was more relaxed - you didn't have to rev the nuts off it to get anywhere, even if you weren't quite as quick.

Alan Woodford
 
When 16v engines first came to the mass market, they were generally used as "high power" versions of normal engines. Examples were the Golf GTi 16v, Corolla GT Twin Cam and Astra 16v.
To achieve the higher power, this was sometimes done at the expense of mid range torque. So in the case of the Golf, the 16v was 25hp more powerful, but many stated that it had less mid range torque.

I'm guessing that either engine type could be tuned to achieve torque at different areas of the rev range, though it would be easier to achieve the higher power with a 16v engine.

Ref the comment on a 16v being smoother. I think not. Fuelling into the engine should make no significant difference to how smooth the engine is.
 
saitrix said:
Not all older cars. :D
Click to expand...
I meant the old boring cars :p

I did notice the different RPMs for the torque, but after I posted, but figured someone would have more info on it, and would clear up after my mess. :p

More and more modern cars are adopting 16v though aren't they?

InvG
 
Depends on how you define smooth. 16Valvers are generally much smoother in their power delivery. Power increases almost linear compared to the revs.

8V engines generally do have better low end torque, so when you see their power curves, they shoot up very quickly in the low to mid revs ranges, but then fall off much earlier than the 16v's.

So in each gear the 8v's will take up very well, but then the power falls off and you need to change again, while the 16v will feel a bit weaker(initially) but will happily rev another 1-2k rpm over the 8v engine giving the impression of smooth accelloration. (And have lots of power at high revs)

Of course the attached gearbox makes a big difference too, with a close ratio box, you can keep the 16'v up in its revvy 4000+ rpm power band and its weaker bottom end wont even be noticed.

Thats why systems like VTEC, and VANOS have been put into newer cars. By changing the timing and fueling low end torque can be greatly increased without comprimising the raw high revving power of multivalve engines.

Yes multivalve engines are getting a lot more common, especially as the problems with lower torque at low revs is being improved by better technology. Not just 16V engines either, but 20, 24, and 32v as well in 5, 6 and 8 cylinder engines.
 
Last edited:
InvaderGIR said:
I meant the old boring cars :p

I did notice the different RPMs for the torque, but after I posted, but figured someone would have more info on it, and would clear up after my mess. :p

More and more modern cars are adopting 16v though aren't they?

InvG
Click to expand...

Just about all modern cars are 16v really now.

But yes the older 16v engines did have less power down low. My engine doesn't really get going until 2800rpm, then after that it really goes.
 
Mr_Sukebe said:
Ref the comment on a 16v being smoother. I think not. Fuelling into the engine should make no significant difference to how smooth the engine is.
Click to expand...

Airflow into a cylinder and how well distributed that air/fuel mix plays a huge part in how smooth an engine is.

8v dont rev as freely as the engine power drops quite soon, but with a big lump of torque earlier the peak makes them fell more grunty, typical there not, the 16v just delivers more consistant power. Godd comparison is the VT Saxo's.
 
8V engines remained popular for a long time because their low end power gives very good tractorbility (spelling?). Tractorbility is low end grunt required when your retired neighbour gets in his/her car, pulls off in second and then skips straight to top gear, making his engine labour hard.

Put the same old guy into an early 16v engine and chances are it would just stall.

But engine design improves every few years, and modern 16v engines are nicely balanced engines.
 
You must log in or register to reply here.
Back
Top Bottom