Discuss-engine wear-8 valve vs 16 valve!

[turbovanman²]

Don aka 4cefedomni was over today and we were chatting about his desire to build a bulletproof 8 valve engine, of course, I say go 16 valve,

I say that if you have 2 engines, both making 500 whp, the 8 valve at 30 psi and the 16 valve at 20 psi, that the 16 valve has less forces being exterted on the crank/rods/pistons thus will have an easier life and reduced engine wear.

He says it doesn't matter, 500whp is 500whp and engine wear/stress will be the same.

Discuss!

[jl93sundance]

I'd say 16v running less boost.


You should make a poll

[turbovanman²]

I can't, too late.

[Directconnection]

hp is hp.... BUT... you have things like the 8v being a bit more prone to detonation.

Mostly... an 8v 2.2 vs a 16v 2.2 will make more torque than the 16v down low, and that can "cause more wear" (actually...breakage)

On the flip-side.... the 16v will rev higher, and those revs can lead to failures as well.

[turbovanman²]

hp is hp.... BUT... you have things like the 8v being a bit more prone to detonation.

Mostly... an 8v 2.2 vs a 16v 2.2 will make more torque than the 16v down low, and that can "cause more wear" (actually...breakage)

On the flip-side.... the 16v will rev higher, and those revs can lead to failures as well.

What about the 10 psi pressure differential?

[4cefedomni]

Bah, either way the same volume of air is getting into the cylinders making the same bang so with identicle dyno charts they both will be exerting the same force on the crank. The 16 valve is just more efficient so it takes less boost to get the same volume into the cyllinders. the turbo would probably wear out alot faster.

[turbovanman²]

Bah, either way the same volume of air is getting into the cylinders making the same bang so with identicle dyno charts they both will be exerting the same force on the crank. The 16 valve is just more efficient so it takes less boost to get the same volume into the cyllinders. the turbo would probably wear out alot faster.

The turbo on the 16 valve?

[bakes]

I believe that 8v needs the extra 10# to make the same CYLINDER PRESSURE that the 16v makes due to better flowing head (more cfm).
With the cylinder pressures and rpm the same the load should be same on the piston,rod,bearings for those hp torque readings.

Now a 16v at 30- 40 # boost

[Anonymous_User]

first, horsepower is simply torque over time, so they are nearly identical. Because of the formula for determining horsepower, when someone talks about a high torque motor, that simply means the torque peak is below 5252 rpm. Conversely, when speaking of a high horsepower motor, the torque peak is above 5252 rpm.

Now, to produce torque, the piston has to push down on the rod and the rod has to push on the crank. The force applied to the top of the piston determines the power output of the crank.

Let's consider a 400 hp motor. Each of our pistons now has to produce 100 horsepower. That 100 hp force to push the piston down requires a set amount of oxygen and fuel. No more, no less. In order to get that air/fuel mixture into the cylinder, we either use massive force on a low flowing head or moderate force on a high flowing head. Either way, we introduce the same air and same fuel. We produce the same forces.

400 hp = 400 hp.

Now, with that being said, the other variable is piston speed. Remember that ever revolution, your piston stops twice. It accelerates up the bore, decelerates and stops. Then it accelerates down the bore, decelerates and stops. The higher the RPM, the more stressful this starting and stoping is on the rods, rod bearings, crank, etc.

So, if one 400 hp motor makes that power at 5000 rpm and the other needs 7000 rpm to do it, then the first one will live a longer life, all things being equal.

A rough example of the last statement: My old Ford has a 385 ci V8. I launch at 5600 rpm and I shift between 8000 and 8500 depending on the track. Friend of mine has a 540 ci engine. Launches at 3500 and shifts at 6000 - 6500. I launch where he shifts. Guess which one needs less maintenance?

[GLHNSLHT2]

Masi 16v with custom pistons and longer rods has a better rod ratio and will wear less

[4cefedomni]

The turbo on the 16 valve?

no the 8v turbo cause it has to boost high

[gasketmaster]

What about the 10 psi pressure differential?

Given a perfect tune up on each engine and all the matching components for the task at hand.....I don't think there would be any additional wear in either engine

The turbo might be a different story

[4cefedomni]

chew on this simon, the 16 valve motors have an extra cam to turn so I would think that would mean it would need to make extra power to make up for that on the dyno. Thus the 16 valve motor would need higher cylinder pressures and that would mean more wear it's miniscule I know but proves my arguement more

[boost geek]

16 valve also costs more money. Good luck finding a $50 Lotus head...

[Anonymous_User]

chew on this simon, the 16 valve motors have an extra cam to turn so I would think that would mean it would need to make extra power to make up for that on the dyno. Thus the 16 valve motor would need higher cylinder pressures and that would mean more wear it's miniscule I know but proves my arguement more

Would have to know all the spring pressures to determine the power needed to turn the cams.

if you have 2 engines, both making 500 whp

Good luck finding a $50 Lotus head

Good luck finding any 500 hp capable head for $50.

Oh, if you do, let me know, I'll take three!!

[t3rse]

chew on this simon, the 16 valve motors have an extra cam to turn so I would think that would mean it would need to make extra power to make up for that on the dyno. Thus the 16 valve motor would need higher cylinder pressures and that would mean more wear it's miniscule I know but proves my arguement more

So now you have to equate for frictional differences between water pumps, oil pumps, distributors (or lack thereof), etc....

my vote: 8v rod bearing will go sooner than 16v, all else the same more or less....excluding turbos

[boost geek]

Would have to know all the spring pressures to determine the power needed to turn the cams.




Good luck finding any 500 hp capable head for $50.

Oh, if you do, let me know, I'll take three!!

I'll see how gasketmaster makes out with his van. If he pulls it off, I just picked up a 655 head at pick a part for $50, and I have a $50 2 piece intake to go with it.

[turbovanman²]

chew on this simon, the 16 valve motors have an extra cam to turn so I would think that would mean it would need to make extra power to make up for that on the dyno. Thus the 16 valve motor would need higher cylinder pressures and that would mean more wear it's miniscule I know but proves my arguement more

I bet you can't even measure that. The midrange in my van is unreal at low boost, way more than my 8 valve setup,

16 valve also costs more money. Good luck finding a $50 Lotus head...

So go Neon head, after the costs of porting an 8 valve head, custom intake and ported ex manni,

[BadAssPerformance]

Added poll and moved to 'engine' section.

Assumptions

both are 2.2L displacement
8v = SOHC
16v = DOHC
both produce 500whp

Anything else to add?

EDIT: by "Engine wear" lets define that as gereral engine durability... bearings, rings, turbo life, etc. cool?

[boost geek]

I bet you can't even measure that. The midrange in my van is unreal at low boost, way more than my 8 valve setup,



So go Neon head, after the costs of porting an 8 valve head, custom intake and ported ex manni,

I had a Neon head, but I needed custom intake and exhaust manifolds, new pistons (again), remachined block (again), plus I would have to mess around with a 16 valve cal. If it wasn't my daily driver it would be doable, over a long period of time, but I need my car running by monday morning, and don't have the cash to build a good second engine.