def1

iTrader: (6)

alright that makes sense. I was under the impression that the turbos flow rate meant that if it made the same horsepower with less boost it was the same as running the smaller turbo with more boost. But i can see how boosting a turbo much higher would cause a lot more heat and such.

detroit pistins

iTrader: (102)

Ya i agree with Scorke and some of the others as well, it makes sense. ........Thanks everyone!

I have another question but not sure if i should put it in the drive train section or here, let me know i u guys think i should move it..anyways.... its the following:

what determines how high an engine can rev? meaning what's the highest rpm it could go up to. is it displacement? or more of the porecision machining that took place on the mechanical components of the system. I guess, why cann;t a 2.0l engine rev as high as the 1000cc motorbike engine? what does it take for an engineer to design such a thing? would like ur comments.

Thanks

RoadSpike

iTrader: (5)

Engineering wise its a few things.

First your pistons have weight, which may seem obviously but listen further. As you spin the motor you are moving the pistons up and down faster and faster. Well that motion translates into forces upon the rods, crank, and wrist pin of the piston. Quite simply if the lower assembly isn't strong enough you will simply make the lower assembly fly apart. A rod bolt will stretch, rod snap, piston break, or some other failure that will end your engine. One very important thing to consider on the bottom end is the stroke. Stroke is the distance that the piston has to travel up and down per rev. Longer strokes means that piston can be moving quite fast at even pretty modest RPM.

Secondly we have the valve train which needs to be able to close that valve fast enough before the piston decides to slam into it. If the valve springs aren't up to the job you could potentially have a piston slap a valve at high rpm . Well no need to describe how bad that would be. At the very least your springs will not be adequate and you'll loose compression as the valve bounces around on the seat.

Generally speaking if you want to have a higher RPM limit you decrease the stroke of the motor, assuming you have tapped out the physical limits of the parts. In this way you reduce piston speed and allow the rev limit to climb. To make the 2.0L motor capable of a 10k rpm limit all that's really required is a beefy valve train upgrade spring wise and a forged set of internals. To go higher will require taking stroke out of the motor to allowing for lower piston speeds thus allowing higher rpm limits.

detroit pistins

iTrader: (102)

from what i understand, its a matter of how well u can move the mass of the internals at a higher revs, correct?

RoadSpike

iTrader: (5)

Not really certain what you mean by "how well".

I'll borrow a few bits out of http://www.kidzuku.com/StrokeOrNot.pdf which is the stroke sticky in the drive train section. Read up on the pdf its good information on what your asking.

More or less if we want to forget a whole world of other things on why the bottom end will or wont take 10k rpm its simply about acceleration. That is how fast the piston and rod combo change direction at any given point in time. This would equate to the G forces involved and how many G's the material your using can stand before it simply gives up and becomes so elastic its unstable or snaps.

detroit pistins

iTrader: (102)

Thanks for the link, i have been reading it for a while but not done yet.
i think when it comes to the material of the internals, as long as they stay within the elastic range then we should be fine simply because all material undergo surface stresses and fatigue at high temps, and accelartion, its when they cross the yielding point and all the deformations becomes plastic then that's when u start breaking things up and interfere with other components such as teh cylinder walls...etc. thus, what do u think if titanium was used for the material which has lower weight and higher yielding point (assumming that material cost is not an issue), u think higher rpm revs are achievable this way?
Thanks

RoadSpike

iTrader: (5)

From what I've been told titanium doesn't do super well because its too elastic and thus will deform more than steel of the same size. It probably does well as a rod but I'd hate to see an elastic crank.

detroit pistins

iTrader: (102)

that's true too. i did some resaearch on what temp they exponentialy start elasticaly deforming but its tough to predict cuz there is no data what the temp of the components are internaly at those rpms.

RoadSpike

iTrader: (5)

What kind of rpm are you trying to pull?

There are other limits too besides mechanical like mach numbers in the intake.

detroit pistins

iTrader: (102)

don't really have any numbers on mind i was just curious what some of the limitations were.
thanks,

scorke

iTrader: (18)

If you can reduce weight of the rotating assembly without making the parts weaker it's going to allow you to rev higher, more safely, yes

Unless you are trying to do something not seen on these forums you should be just fine with a steel rod!!!

Scorke

detroit pistins

iTrader: (102)

Alriiiiiiiiiiight!
Thanks

Broham

iTrader: (10)

Have to resurrect this thread once more, since I thought of it as very interesting. When is it adviseable to upgrade the internals of the car? rods, pistons, crank. i am running a simple evo 9 with stock parts and don't know if it's wiser to strengthen now or to strengthen when I or if I ever upgrade the turbo.

Pistins, what hp did u end up making? what did u do?

detroit pistins

iTrader: (102)

unfortunatly, i ran into some financial needs and never had the chance to mod the car, its up for sale.

for ur question, i think its best to built the motor at first especialy if ur eventualy thinking of it just to avoid any other components that might fail down the road, such as breaking the block incase u throw a rod or something. I think ur decision is a function of both, how much power u r planning on making, and how much of an impact ur wallet is welling to take.
cheers!

Joshs EVO

iTrader: (46)

I did 485Hp on 22lbs