seeing as this is a car forum, how about a discussion of 8v vs 16v engines?

i've often wondered are 16v engines really better than 8v engines for the average driver? 16v engines in my experience tend to have less grunt, lower down the rev range than your average 8v. obviously at higher revs the 16vs are much better but i've found for general driving 8v engines are much more useable, is this just my experience or is this a fair comment?

and on that note are 16v diesels any better than a 8v diesel due to the lower revving nature of the diesel engines?

come on lets get some good fairly technical discussion going

i'm basing this on four cylinder engines, but any other engines with 2 valves/4valves etc per cylinder may well be relavent too?

well for the fiat 1.2 8 valve
they are cool
seems to be able to survive my driving

Variable valve timing can help a 16v engine give low down power comparible with an 8v engine. Also, I think some of the VVT engines operate less valves at low revs and only open all four valves above a certain rev range giving them good torque across the rev range.

I'm not that clued up on it though, but I do remember many people comparing the 16v mk2 Golf GTi when it first came out with the 8v model and finding that the 8v was nicer and easier to drive. As you said, it was because the 8v was noticeable more torquey low down whereas the 16v needed revs to produce its extra power. In real world driving situations the 8v could more often be the quicker car simply because the power was more useable.

With MPi and VVT I would've thought modern 16v's would have the best of both worlds these days? Anyone known?

The more basic 8v engines are produced manly for torque - for example a mk1 1.4 punto gt had the same bhp as the mk2 1.8 16v HGT which had vvt, but the GT had more torque due to the turbo.

When comparing the 1.2 8v and 1.2 16v engines there should be slightly better emissions on the 16v.

When you get into bigger engines is where the valves really matter Ferrari V8's have 5 valves per cylinder - 3 smaller inlets plus 2 larger exhaust valves. This allows a large amount of torque low down and loads more power over a larger rev range which is also helped by vvt.

1986Uno45S said:

With MPi and VVT I would've thought modern 16v's would have the best of both worlds these days? Anyone known?

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Mulitvalve engines are pretty useless tbh without vvt IMO. Mpi has been around for ages now and is good but compared now with FSI type injection plus multivalves plus vvt and a turbo you can get low down torque a constant supply of power over a higher rev range plus if driven right a close mpg of a diesel from high performance petrol engine TFSi rocks :slayer:

in 8 valve engines you have 8 less valves to bend when the cam belt snaps Unless its a "safe" engine of course..

Andy Monty said:

in 8 valve engines you have 8 less valves to bend when the cam belt snaps Unless its a "safe" engine of course..

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I have a 16v and rev it lots and lots, it loves it :devil:

8v engines much better lower down- my Fiesta was a 16v'er and it didnt have any power until 3500rpm- at this point it felt like VTEC coming in lol

If you look at the new m-jet 1.6 16v, the torque comes in lower than the 1.9 8v m-jet?

I have 2 16v cars ant one loves being reved, the other doesn't

The 16v 1.9 multijet produces nearly 40bhp more standard. Maybe it's turbo, I don't know.

The 20V alfa 2.4jtd made around 175bhp where the 10v alfa made 136.

Helz said:

I have a 16v and rev it lots and lots, it loves it :devil:

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:yeahthat: I love hitting 4000rpm where its almost like hitting vtec yo! :slayer:

I love the little 999cc and 1108cc 8V FIRE engine. Really pokie around town, and don't mind revving.

The 1.4 16V in the Stilo though. OMG, 1st-3rd gear, hit te 3500RPM mark and it feels like nos has been injected Is a bit crap at lower revs though and needs to be slung down gears if a quick pick-up is needed.

Most Easterly Pandas said:

I love the little 999cc and 1108cc 8V FIRE engine. Really pokie around town, and don't mind revving.

The 1.4 16V in the Stilo though. OMG, 1st-3rd gear, hit te 3500RPM mark and it feels like nos has been injected Is a bit crap at lower revs though and needs to be slung down gears if a quick pick-up is needed.

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are all 16v engines gutless below 3500 rpm though? ignoring VVT and JTS/FSI

for example my old car would happily go up monks hill (1 in 3 or 4) at low revs in 2nd gear whereas the sedici won't. obviously the gears are different, 2nd only went to 40 in old 1.4 and almost 60 in 2.0. i don't think my old car used to do it in third though, but then 2.0 is a bigger engine so not really a fair test lol.

this is an issue as you have to slow down near the top due to a blind and tight bend. obviously it's easy enough to drop into first so going up is not a struggle at all but crutially it has to be in the right rev range on the sedici as opposed to pretty much anywhere on the 1.4

also i've found similar with a renault clio 1.4 i did my pass plus in. below 3500rpm it was slllllooooowwwwwww but then above 3500 it suddenly picked up dramatically, so in reality it was slower than my lower powered 1.4 tipo which was a bigger/heavier car.

thinking about it, with diesels the turbo tends to come in earlyish anyway so provides the faster flowing air for the multi valves earlier on. so is pretty much irrelevant lol.

My dads C5 is boring and gutless below 2k, as soon as you get to 2500 your off. Its probly got VVT though, which would help

16v - better performance but a little more maintenance. For instance the 8v doesn't need to have the fuel filter changed.

Last punto I had was a 8v. No problems with it at all. Only thing was the gearbox. It would have been helpful to have a six gear just for the sake of crusing as the revs are so high you can hear the engine more than the tires.

claymore said:

16v - better performance but a little more maintenance. For instance the 8v doesn't need to have the fuel filter changed.

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Whys that

maddogmorg said:

are all 16v engines gutless below 3500 rpm though? ignoring VVT and JTS/FSI

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Dunno. Mum's 999cc 16v Yaris goes like poop off a scoop (with me driving) but that has VVT-i

The Stilo isn't gutless below 3500rpm from moving off (will shift in 1st with it below that rev number) but just when wanting to overtake etc.

If you go back to when 16v engines started to put in an apearance, mid 80s? they were useless below 3500 - 4000 revs. Essentially, at that speed they had too much valve area. It was a bit like fitting a 3" fire hose to your kitchen tap and then trying to reach the flower bed at the bottom of the garden. It couldn't produce enough flow to project the water far enough.

On the other hand, fit a half inch garden hose to fire hydrant and try to put out a fire. Not enough flow, therefore the water would just trickle out of the end of the hose.

So it's a case of horses for courses. A magic hose would narrow itself for the kitchen tap and then widen itself to put out a fire. The larger valve area of a 4-valve head would mean that a small amount of petrol and air would tumble down the inlet manifold and not arrive in the combustion chamber at the right velocity, or alternately, incorrectly mixed. At higher revs, however, it would all
work perfectly well. With a 2-valve head, the mixture was right at lower engine speeds but the smaller valve area limited the amount of air/petrol or diesel that could get into the cylinders.

Engine management systems and (sometimes) VVT is the magic hose element of it all. Oh and mustn't forget EFI. Put the EMS and EFI together and the 16 valve head suddenly makes sense.

As for diesels, well I can only compare my 1.3 MJ with the 1.4 Peugeot engine in our Fiesta at work. You only have to drive them to see the MJ is a generation ahead of the Ford/Peugeot/Citroen unit. The only other diesel comparison I can think of is how much better, in every respect, other than simplicity, modern Common Rail Truck diesels are than their predecessors. Smoother, more powerful, more economical, quieter and cleaner.

claymore said:

16v - better performance but a little more maintenance. For instance the 8v doesn't need to have the fuel filter changed.

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Eh?

claymore said:

more maintenance. For instance the 8v doesn't need to have the fuel filter changed.

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Well thats a lot of tosh! The fuel filter should be changed as part of routine maintanence, it is a service item like any other filter on a car. The amount of valves in your engine doesnt come into it

What happens when it gets clogged full of crap? 8v or 16v, your going to have the exact same problem. The petrol pump doesnt decide its putting fuel into an 8v, so it will give you pre filtered fuel!

Any fuel filter needs replaced, the amount of valves you have never comes into it! By the logic of more valves = more need to change a fuel filter, all i can say is god help the people with 24 valves and above they would need to change their filter every fuel stop, for those with more, before every journey!

The Beard said:

If you go back to when 16v engines started to put in an apearance, mid 80s?

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Come along now, Bentley 4.5s had 16V four cylinder engines in the 20s, which I think was an idea stolen from Peugeots, surely you remember that.

Cheers

SPD