was just thinking about the merits of multi- pots ,most cars have been 4 pots mainly due to cost and packageing I would say ,but then surly theres still advantage to be had with say inline 5's an 6's more valve area , more power strokes per rev , but are long blocks , so then we have V's say 6's an 8's as the next idear same again more valve area more degrees of stroke delivering power due to the v configeration and primary balance is good , but then size of the package can be a problem and friction losses with the extra cam work allso add to its problems , then we have the big boy's the v 10's an 12's same again lots of valve area , lots of bangs per rev ,but there a big package with a lot of heat and frictional losses , so whats your thought on the characters of each engine type ,and why do you think the 4pot still rules is it cost ? or maybe turbo tec that has made the need for multis more defunct ?

 

I have no idea what your asking but I do remember having a 5cyl Audi 80 that sounded like a riot van and I loved it !

 

5 bangers all the way
best noise ever........no argue

and again, no comprende le question!

 

Me and my radio trucking on through the night

 

Motorway sign coming up in the morning light

 

4 pots 4 strokes makes for smooth delivery and reliability

i dunno bout these 5 pots, seems a strange idea and they always seem to be thursty lumps and how does having 2 pots on the power stroke then 3 more singles help with stresses and strains on the crank etc or am i thinking wrongly??

 

[quote=Rax;5690156]I have no idea what your asking
your kidding right! no your not ok ,multi pots in different configerations have advantages over the basic 4 pots so why is the main stable of cars 4 pots and what do you think of the character of multi pots say a v6's revy but lack torque unlike say a v8 and why is there a lack of multi's in todays cars .

 

I love 5 cyls! Sound grunty as hell low down and scream like a V10 high up! Im always amazed at the torque my old mans T5 chucks out! Not that he lets me drive it much

 

i think the main reason is fuel economy .a big v8 is always going to have shit fuel economy even with fuel injection .the 4 pot can give good economy & good performance all in 1 compact little unit which in it self can give you more room inside the car .

 

Got to be a V8

Not including the new fangled ones with a flat plane crank - no burble

 

The sort of 'Messy' sounding V8's are the best!

 

you mean they have a 180 throw not like the one I had a "cross plane crank" with a 90 throw funny that I though 180 cranks was an old school configeration ?

 

think next time Ill just ask about peoples fav chock bar ..........jesus!

 

Flat plane is 180 deg and sounds like a pair of four pots

90 deg has the burble

Old Jamaica chocolate FTW

 

You sure!? I heard 6cyc was the best for smoothness. Not sure how true it is, I can only comment on 6cyc, v6 v5 and 6cyc and head and shoulders above the rest inline6cyc is the smoothest.

4cyc is moot common due to economy, cost and size would say.

By the way original poster missed 3cyc lol

 

More cylinders usually equates to a smoother running engine as you have more power strokes per revolution.

More power strokes per revolution, better power/torque.

For me, it's a V6 all the way. Nice noise, smooth running engine.

However, that Lamborghini V10 in the R8's, glorious engine.

 

Most new v8's tend to turn a bank off when they are cruising for economy, but the bigger the car the bigger the engine needed

 

That's old way of thinking!

 

For a petrol engined road car, you are typically looking at something that works well at about 3Krpm and pulls acceptably to 6K or so for overtaking.

what this means, is that strokes of around 60-90mm tend to work well, due the piston speeds involved.

Generally engines in those rev ranges tend to work well relatively close to square.

So you end up with cylinders of around 300-500cc being particuarly suitable.

So if you want a 1-2 litre engine, a 4 cylinder is a good way to go in that respect.

Then like you say its simple to package of course.

 

how wrong of me, because nowadays most 7 series beemers and s class mercs use 2.0 4 pots don't they

 

What about number of pots with regards of tuning, is more better? Like a V8 vs 4pot?

 

5 cylinder engines don't work like that.

http://en.wikipedia.org/wiki/Straight-five_engine

144deg as opposed to 180deg

 

Well more pots means more valves, and that generally means a bigger total valve area, so that tends to lead well for tuning.

Not always the case though, lots of other factors are important too.

 

Adding cylinders normally looses eficiency due to the increased surface area exposed during the power stroke, allowing heat to leave the mixture as it burns.

Hence 3 cylinders and even 2 cylinders in the new fiat "twinair" engine.

Only a boxer engine's arangment of cylinders can be truly balenced in the 1st and 2nd order, hence porches love of this arangment.

P.S. This should be an interesting thread

 

when you say square do you mean the bore/stroke ratio?

Its there any advantages/disadvantages of an engine being square, over suare or under square.

 

so that would explain why larger engines have tended to produce less power per cc as opposed to the smaller units then?

but it's also easier to get mroe power out of them with a bit of fiddling yes?

can't remember which mag its in, but a recent 5 litre V8 was supposed to only put out 126 brake in one version of a car it's fitted too with another version putting out 260 and above, obviously yank

 

Yes mate.

Its very application specific, often people will make their engine a longer stroke to increase capacity for example, and as a result parhaps end up with slightly less power per cc but still more power as they have more ccs.

Basically as a general rule of thumb, for a really revvy engine you have a bigger bore than stroke, to prevent piston speeds getting too high, and to increase valve area.

But an evo engine has a longer stroke than bore, and a YB has a bigger bore than stroke, which totally contradicts what I just said of course, as the evo engine revs far better than the YB.
But there are LOADS of other factors that are the reason why it looks like it doesnt work how I just said.

 

Spot on!

One of the reasons that smaller turbocharged engines are more efficient is because of the reason above. For the same output, they have a much reduced internal surface area. Increasing the thermal efficiency and therefore the power density of the powerplant

 

Also, more cylinders means more moving parts in the valvetrain, rotating assembly, and sometimes bearing surfaces. Increasing the parasitic friction.

Not to mention the power required to pump water through bigger water jackets and larger quantity's of oil through the engine

 

PPC, talking about the 5 litre v8 in the Lincoln Towncar and the fox body mustang.

Engine cylinder numbers are decided on many factors. 4s being easy to package, straight 6s smooth, v6 can be used in fwd because of their shorter length etc.

Manufacturers just look at whats required/ expected from customers when deciding. People don't really want a revvy 4 pot at the front of their 7 series or a thirsty v8 stuck over the front wheels of their Micra! Lol

 

And less weight of engine means better economy too of course, not just in terms of the engines efficiency but in terms of effecting the weight of the car.

 

Agreed

Im a fan of long stroke engines myself, But as you say its all down to the intended application

 

Not seen the new small engine one then??

They do make them now! 5 years ago would you have ever though of a 2.0d 5 series!? Open your mind

Yes there is big engines aswell and let's face it I suppose if I can afford a new car in that price range etc.

Also I'm no small engine person in my 3ltr 6 pot lol.

J

 

i said 7 series

but i understand what you mean, especially with the new merc 4 banger being the winner of most torque for a 4 pot or something, 500nm or something in a boggo motor is something from a 2.1 litre engine that only makes 170 brake

 

For performance use, you will tend to find most engines end up at around 25 M/S average piston speed at peak RPM

That is true from F1 down to the Vtec lump im putting in my civic.

 

On the mlr there are engines reving to 26M/S at peak rpm, the builders of these engines say it is fine at these piston speeds.

Would this noticeably increase engine wear?


Very interesting thread

 

After driving my uncles camaro in the states, the low to middle range usable power that was always available was bliss, even with a 6500 redline. 5.7 small block with EFI and a T-56 6 speed...

granted, on a track my views might change being able to use the higher RPM band more of the time

 

A vtec B18 engine at 11,000rpm which is what some nutters rev them to, will see piston speeds of 32 M/S !


Higher piston speeds will mean higher wear rates typically if everything else is equal, but things like piston design can make a big difference in ring life, a deep skirt that allows a piston to tip less for example can improve ring life.
Rod ratio effects it too, as it changes the PEAK piston speed, where as we are talking here about average piston speed which rod length has no bearing on.

Internal engine geometry is a very complex subject with so many factors interacting together that looking at just one in isolation is rarely valuable.

 

Chip, do you know of any big power N/A Z22SE builds going on at the moment?


I've been looking at Z22SE.co.uk, theres a guy on there called Vocky with an early VX220 with a N/A 2.4 making around 240-250bhp on throttle bodies.... the 2.4 is a massivly under square engine, 88mm bore and 98mm stroke. The torque must make for an interesting drive with N/A response.... Views???

 

No mate I dont know of any, everyone seems to want to go forced induction, and at that sort of stroke its easy to see why, and when you take into account they have a crap rod ratio which means that its even more a case of flogging a dead horse.

The piston speeds just after TDC are far too high for an engine you want to rev N/A, you just cant generate enough cylinder pressures well.


Its easy to see why you would want to destroke and use a longer rod and have it 2.0 instead of going upto 2.4!