For the love of a tractor engine: The life and times of the 18R-G

[Rens]

For a n/a you need to rev it harder to get decent power out of it, shortening it's life. Turbo engine would be making more of it's power at a lower rev range. As long as your not running crazy boost , the turbo engine should last longer and probably be more efficient too.

Oiling would probably have a say in it too

I still prefer the sound of the carbs over the surge of the turbo though.

[JustenGT8]

how so witzl

i woulda though 200kw is 200kw of strain on all engine components regardless of how its derived every action has an equal and opposite reaction ????

wear i can under stand as the parts are moving more for any given amount of time so the service interval becomes more frequent but loads and forces exerted would be the same bar frictional losses wouldnt they ??????

Nope, not even close Zammo.

If you look at the forces on components thru the combustion cycle (google it) you'll see they peak just before TDC and BDC ie when the piston suddenly stops. Nothing about boost effects this, this is simple the piston stopping and reaccelerating with revs. But wait it gets worse, this forces increases exponentially with increased rpm.

So, not only is rpm the main stressor of an engine (not combustion forces) it's the thing you need more off to make power n/a and it gets to nasty levels real quick.

Adding boost will increase combustion pressures so you do need a head gasket up to the task and piston ring lands will become an issue at some stage...but generally speaking, most engines will take boost and easily make 1.5 to 2 times stock hp. Not many (if any) will do this n/a, without significant mods

[JadeEstevez]

Just throwing this out there... The stroke on a piston engine also creates torque with the down force before BDC doesn't it? That's why RPM doesn't hurt Rotary engines, They thrive on it but don't create much torque yes? Sorry if I'm incorrect.

While I'm at it, I heard torque wrecks diff's. Does this mean technically you could have a 1000hp Rotory engine creating bugger all torque on a pissy little T series diff and it won't be destroyed? O___o

[Sagluren]

i work at a roatary workshop, seen pleanty of destrpyed diffs, rotarys like revs becuase as justen said rotors dont have to stop they keep turning. Rotarys also need revs to clear out all carbon deposits. there are a busket load of seals on the rotor that are very sensitive to carbon deposits. Hense why the auto rx8 are having engine rebuilds at 60000km

cheers sam

[JadeEstevez]

Ahh okay... I have been thinking about buying a rotary for the Celica, Is there other options for the seals in rotary engines so they last longer?

[The Witzl]

Ahh okay... I have been thinking about buying a rotary for the Celica, Is there other options for the seals in rotary engines so they last longer?

Yep, replace engine with 18rg, and take your rotary discussions to another tread.

[JadeEstevez]

Sorry about that

[Zammo]

YES RPM is more stressfull to components the weight difference between a 200gram piston moving at 26m/s compared to 30m/s is probably measured in tonnes ? that knida math is interesting but i cant work it out without help (Letters are for reading not adding)

Turbo is more efficient and moves the stresses to were an engine can better cope with it


but theres ppl that make MORE efficient N/A engines High CPR +12:1, 12-14.000RPM very expensive motors THEN smack a turbo on it the entire opposite of what most ppl do.

my reasoning

X-chemical energy IN = Y-kinetic energy OUT i realise there be slight differences here as in a turbo will output the same KW with less CE or output more KE for the for the same amout of chemical energy

but as you increase the efficiency of a motor you reduce energy loss

all things being the same the forces acting in the motor must also be the same as we know we cant yet create extra energy from nothing ?????

so turbo moves those forces to where an engine can better cope with it

argggghhhh

[The Witzl]

I'll make it easier.
Think of the piston coming up to top dead centre and bottom dead centre (ie, moving up and down), as you being flung back and forth between two brick walls.
its giong to hurt a FUCKLOAD more if you are being flung back at forth at 100times per minute than at 80 times per minute - because of the extra acceleration and decelleration.


As justen said, the extra forces are SQUARED for each unit increase in RPM.
That means, if the rpm is doubled, the forces are QUADROUPLED. If RPM is 4x, then the forces are 16x.... etc etc.

[Sagluren]

marcus, not reall any better seals, you can get diffrent apex seals but they destroy housings. But as witzl stated. not more rotoary talk.. read at book called 4 stroke performance tuning.. will teach you all you need to know.


cheers sam

[Zammo]

As justen said, the extra forces are SQUARED for each unit increase in RPM.
That means, if the rpm is doubled, the forces are QUADROUPLED. If RPM is 4x, then the forces are 16x.... etc etc.

this was the bit throwing me off the SQUARED factoring ive not read that anywhere

'being flung back and forth between two brick walls.
its giong to hurt a FUCKLOAD more if you are being flung back at forth at 100times per minute than at 80 times per minute - because of the extra acceleration and decelleration.

Love that analogy but i highly doubt id care much about the pain when id be dead in both instances = from this ive concluded that i will stay high RPM hi CPR spastic N/A motor

if its gunna die atleast its gunna die spectacularly doing what we love.

[JadeEstevez]

Cheers Sagluren, I'll suss it out.

Agreed on that analogy Witzl, Made me and my Girlfriend laugh =P

[masterofsinanju]

this was the bit throwing me off the SQUARED factoring ive not read that anywhere



...

If you consider the formula for kinetic energy

KE=1/2mv^2

Think about the speed each of your pistons reaches just before having to come to a complete halt in very short order. Even a relatively small increase in piston speed equals considerable additional energy that needs to be absorbed by various parts.

[Zammo]

KE=1/2mv^2

I told you letters are for reading numbers are for adding.

corolla = half a boat and a little triangle require me to think, brain dont do that but the 2 i understand.

we dont "maths" were i come from we just bolt shit together and flog fuck out of it till it goes boom boom bang (i will try not to fuck any heads up but OK)


no doubt i could learn it but that would push out other memories i wanna keep, so no.

all to much for me.

imma take it back to the old school and just fuck shit up, trying!

[o_man_ra23]

It's actually the force applied which is the problem. Not so much the amount of it, but the direction at which it is applied. As the conrod is only vertical at TDC and BDC, these are the two points in the cycle where it can actually handle the most force from the piston. However, once it starts getting into the cycle, the forces applied are at an angle, and the rod wants to bend.

As force is a factor of accelleration, as you spin the motor quicker, the rate of change of speed of the piston has to increase, and it does it in a squared manner (as explained for Ek (kinetic energy) above. This is because as you increase the speed of the piston, it has less time to change speed in. It's a vicious cycle

So going high up in the rev range, just rotating the engine, let alone trying to make power from it, becomes an arduous task. And this is why conrods like to work on their tan when you over-rev an engine...