**Best Engine**

[Topher-EK9]

^ Ah got it
this is why i joined this fourm as it was by far the most tech out of the lot of them.

this is a nice piece of INFO:

"engine wear is increased and rod failure is possible if rev limits are pushed to far with B20 blocks, The g forces the rod experiences are significantly more (20% more) at the same RPM." 20% more than a B16A at 8000RPM
that is cool.

 

[Kozy]

AH man i just found this.....

FTLRacing

its s*** hot info but i need a cup of tea and a good couple of hours to get through it.
equations always throw me and then you see a diamgram and it makes total sense.

Yes have a good read, it's interesting stuff.


As always with the stuff I do, it's very much a case of garbage in garbage out, so take it with a pinch of salt, but I have a fairly comprehensive spreadsheet that I wrote at uni than depicts this sort of stuff rather nicely.

Here's a plot of the internal forces of the two engines at 8000rpm.

Primary accleration is that of the piston moving up and down the cylinder
Secondary is the additional acceleration caused by the side to side motion of the conrod.
Combined acceleration is the overall effect of the two accelerations.

We can clearly see just how much more stable the B16B is at high speed compared to the B18C. Worth noting here that the primary forces balance out in a four cylinder engine, leaving the secondary acceleration as the primary cause of engine vibration. Actually, I'm not sure it is the primary, that could be due to the firing order, but it is certainly the motion of the conrod that contributes more to vibration than the piston moving up and down the cylinder.

Heres the same plot with the B16B at 9000rpm and the B18C at 8000rpm.

Notice that now the primary acceleration on the B16B is higher, but since these cancel out to leave only the secondary forces unbalanced and these are now almost equal with the B18C.

Combine this with those piston speeds I mentioned earlier, and we can see how the B16B could be capable of that extra 1000rpm over the B18C. It would certainly need a bit more work to achieve this, but the possibility is there. It would need lighter pistons for a start, the B16Bs are fairly weighty at 327g compared to the B18Cs 305g.

This weight contributes to rod stretch at TDC, which then increases the compression ratio slightly at higher RPM, which then.... oh where do I stop?!

I'm going to shut up now and let someone else chat **** for a bit.

 

[dhdavectr]

Best engine that I've had has to be the b18c, more torque than a b16, revs better than the b20 I was in and has that bit more than a b18c4.

Can't beat a b16 for bang for buck but for the price of a b18c4 lump getting lower each day I don't see much point in buying a b16 to save a few quid

 

[Barryl85]

Although it may seem that the B18 is just as reliable as the B16, simple physics means that the internal forces in the B18 are significantly higher, and this leads to reduced longevity, especially with regards to piston rings.

I estimate that the B16B can take handle another 1000rpm over the B18C before the internal forces start to equalize, at 8000rpm the B18C mean piston speed is 22.61ms, where the B16B is only at 20.07ms. At 9000rpm the B16B is up to 22.58ms, so still a tad less than the B18 at 8k, and there is roughly 17% less sidethrust to wear down the piston rings at any speed.

This is not to say the B18 is unreliable at all, but if you were to take two new crate engines and race them flat out for 24hours, then strip them down and check the cylinders for wear, the B18 will show a bigger cylinder ovality and significantly worn rings compared to the B16. It would not last as long as the B16 in an endurance racing environment for this reason.

Considering not many people run EK9s as proper race cars then this is a bit of moot point, 99% of people will happily trade a bit of longevity for the extra low down torque that the B18 offers, but talking purely in terms of race engine design, the B16B is the better engine.

I still dont agree, the internal components in both engines will be within spec to withstand the constant forces produced internally.

Doesn't larger internal forces lead to more torque produced?



If you take this as an example, you have two bridges the largest one is capable of withstanding 10000kg's in weight and the smaller one is capable of withstanding 12000kg's in weight.

At any given time the bridges only hold 8000kg's

Which one will fail first?

Answer is none.

 

[Kozy]

I see where you are coming from, but the principal is a bit different. A bridge does not not have the same life expectancy as an engine, it would be expected to last indefinately provided it is not taken outside of its operational limits in terms of load. It does not wear out like an engine does because generally it is a solid structure and not designed with friction surfaces. Even if an engine is not pushed beyond its limits in terms of load/rpm, the friction surfaces will eventually wear out over time, there is no escaping this fact. The geometry of the B18C increases the wear on the cylinder walls and piston rings because of the larger angles the rods run at and this reduces the life expectancy of the engine. Think about how everyone says the B20 is unreliable when revved high, yet it's stroke is only 1.8mm more than the B18C. Sure the cylinder liners are thinner, but this is only a problem because of that sidethrust caused by the conrod angle. (Or if you are running big boost)

Again, this increase in wear isn't anything that anyone would reasonably be expected to notice unless they were racing, and the power gains usually outweigh the slight reduction in life expectancy so it is pretty much universally accepted as being a worthwhile trade off, at least for a street engine.

 

[Barryl85]

I see what your saying also mate

I also think about other factors as well - with you saying stress/load on the engine - wouldnt the extra torque of the B18C give it less work to pull the same weight?

 

[Kozy]

Yes, but you are then removing the 'all else being equal' parameter, which makes it difficult to compare.

You would have a point perhaps, if a B18C never saw more load than was needed to match a B16 as obviously it would be spinning slower to produce the same power at any point, but that is not representative of conditions on track, where engines spend a large proportion of the time at WOT and component wear is most pronounced.

 

[Topher-EK9]

I'm really starting to get the hang of these graphs kozy, Its V.interesting mate....
thanks for taking time to write it up.
I can go for a second order of that **** though...
dare i say i want more...