Enough to know that the difference in rod ratios and dwell around TDC is far smaller in effect vs how well charged the cylinder is, in terms of creating cylinder pressure. You obviously have never done the math.

You are aware what you are proposing means power will keep increasing, as the rod gets longer and rod ratio improves. You don't see this because you run into real world issues like rod mass. Another is engine integration and as the engine gets taller, heavier, raised CG, all to house the taller assembly which has extremely limited power gain that rapidly diminishes very early on in the rod ratio range, so the car doesn't get faster.

You may be aware of one or two prominent exceptions in racing, but the objectives there were airflow from tract efficiency (airbox volume/shape and runner length/trajectory/spacing). The power gains from airflow critical NA operation, the materials used, and engine type and placement, all offset the negatives which are still major considerations everywhere else including here with us.

 

you guys are all mentioning things I already know...yes mass and one problem you haven't mention is peak pressure from burn time in relation to the dwell...

there adverse affects to igniting burn to early...more freely revving and more pressure exerted downward on the piston ATDC (torque)....and in the far extreme case you bend rods, break pistons or snap a crank...

one you can't use a base number like 14 ATDC as best when that is heavily dependant on dwell and when the piston is actually accelerating back down...

trade offs that have been forgotten on the long rod is less rod angularity equally either less thick rods or same thickness and more pressure above the piston allowable...

the mass thing is kind of a funny point as a stroke motor adds mass in the crank too...the block doesn't have to be raised to make a longer rod work...do some math...and power can be increased as a long rod is known to give a more torque when compared with a shorter rod of the same displacement...you have less rod angularity therefore you can increase pressure (though not statically compared to larger displacement) and then use more of the pressure to push the piston ATDC as compared to the shorter rod ratio igniting further BTDC and using % wise more pressure resisting the engine's rotation...that is negative power inevitable in any engine but just lessening it by going with a longer rod…
try punching the numbers into virtual 4 stroke and tell me I'm wrong...please be my guest…

 

hahaha... i think he engineers ic engines... their piston and their rods... as well as their cylinder geometry.

 

you ****in' suck **** at writing. you also failed to clearly depict both timing advance and the autoignition and piston dwell that you were trying to get at.

also you've been jumping from one topic to teh next to try to justify your knowledge and expertise in this subject...

a stroker crank surely adds mass to the crank as the crank is longer... but usually in applications like 'ours' the piston is then modified so you can't just say what you said with any sort of universality.

longer rod is great n all but applicability deems relevancy.

might i say one more time... gadang you suck at writing.

 

This benefit is written about all the time, even on this forum.

Generally..

1) With a stroker you gain displacement, add mass to crank, lose mass in rods.
2) When you destroke you lose displacement, lose mass from crank, add to rods.
3) When you keep stroke and lengthen rods, you add mass to rods as well as to block, and you do not gain displacement.

As you gain displacement, engine speed normalizing for throughput is reduced. Reverse is true for losing displacement. Motion at crankpin is perfect rotation, but any part of of the rod beyond the crankpin is a mix of rotation except at piston pin end, it is pure reciprocation. Pure rotation or pure reciprocation, acceleration still increases as square of engine speed. The difference with pure reciprocation is that you have 2 very large peaks in forces. On 2 and 3, you are adding mass to the rod beam and adding mass to areas which either purely reciprocate or have mixed motion.

So you have to watch where you add mass and realize which contributes more to peak forces.


Yes it does if all else is held constant. As an engineer you should know how to conduct a comparison. If you keep bore, stroke, and compression the same, then the block has to become taller to accommodate the longer rod.

There are always bore limits whether regulation or physical limit. So with that limit there and if you're already at it and you destroke the engine to accommodate the longer rod, then you have to raise engine speed to normalize for throughput and still are fighting considerably greater friction.

It is not "known". It is claimed by you, and it involves way too many variables to attribute any tested gain to a single factor, or even the rod ratio factor as a whole. When you try and conduct experiments to test differences in rod ratio alone, you are changing...

1) rod mass and mass distribution (if bore and stroke kept the same)
1i) crank mass (if destroking for longer rod)
2) piston design, mass and/or geometry
3) how the cylinder draws on the port
5) block characteristics (if compression, bore and stroke held constant and going to taller block)
5i) bore (if block and stroke kept the same)
5ia) ...so port-chamber and/or chamber-bore transition, in cylinder flow and combustion
5ii) compression (if block, bore, and stroke, kept the same)

Go ahead if you can, and propose a truly scientific test that shows true differences in rod ratio alone without involving a bunch of other variables.


Virtual 4st is a simulation. Key word is virtual. You can eliminate the variables in simulations, but the real life tradeoffs and complexities remain. You can't escape them.

 

first of all I never claimed to be good at writing or teaching ingorant people...
trinydex: yes, I never went into detail on all the parts and yes I did jump around a lot. kinda scatter brained babbling. now with you crank mass and piston mass comment think about it...how do you get a longer rod in a block with the same deck height and a stock crank...you modify the piston.

 

you are an *******.


You are an idiot.

There is a beautifull thing called compression height. Look it up and you'll find the answer. How else does a stroker crank work with the stock rods?

You ****ing tools are out here trying to disprove facts that have been presented by Homemade WRX. He has more knowledge on the subject than all of you combined.

Also, if you'd like to give me a go, I'll gladly jump in and make you look like ignorant asses too.

Thanks,
Dominic on Blackevo's login.

 

Homemade has been trying to answer slams from 3 or more people at the same time. it's hard to keep everything on a linear track when you have so much going on.

Main Entry: lin·e·ar
Pronunciation: 'li-nE-&r
Function: adjective
1 a (1) : of, relating to, resembling, or having a graph that is a line and especially a straight line : STRAIGHT (2) : involving a single dimension b (1) : of the first degree with respect to one or more variables (2) : of, relating to, based on, or being linear equations, linear differential equations, linear functions, linear transformations, or linear algebra c (1) : characterized by an emphasis on line <linear art> (2) : composed of simply drawn lines with little attempt at pictorial representation <linear script

figured I'd include that if I used words that had too many letters.

 

Not to rain on anyone's parade, and I realize that it's easy to get into an argument on the Internet but Shawn@SG is a well-versed engine builder.

 

This is so funny. Aparently in your mystical world of engines, you don't have detonation or preignition.

Ever heard of "combustion chamber heat management" ?

It's a nifty thing where we find ways to minimize the amount of residual heat in the combustion chamber. How do you think detonation occurs? It happens because the flame front is ignited too early. The more residual heat the more likely to have detonation or even worse, preignition.



AS far as shawn being an engine builder, wow, that's great. I am too. Woopty freakin' do. Any idiot can swing a hammer and build a house, it's the architect that designs it. Same goes for building engines.

-Dominic on Black's acct still

 

I know I came in here and started flaming, but it just makes me angry to see jerks calling homemade an idiot, when everything he said is very true.

He never said longer rods were better than stroking. He gave pros that a longer rod has OVER a stroker. There are a lot more that he hasn't said that I too could add to this thread. However, this has gone on long enough.

-Dominic

 

so you suck at readin too... i said ENGINEERS THEM... not BUILDS THEM, so you've basically just proved that you're inferior to him... both in reading comprehension and in engine engineering education.

don't you just Love aLliteration?

 

1.) on the 2.3L strokers they use a 150mm rod...stock size num nuts...they shave some from the pistons.
2.)who said anything about destroking?...not needed
3.)who said anyting about lengthenging a block?...not needed

guess what, I know how to conduct a comparison...you obviously don't. Once more the block doesn't have to become taller.

you do have something right...friction does indeed grow a large amount in accordance with engine speed...done a test on that and have a break down by component with removal...


It isn't claimed, there have been studies done on it...not just by me
funny all the things you mentioned are given changes that occur when you change only the rod ratio...yes, virtual 4 stroke is only a simulator but a rather entailed one used in the industry. Have you ever used it?
From all of your 8 points the only true one's that NEED to be addressed in my case would be a changed compression ratio(easily taken care of), rod mass but decreased piston mass (a minute point), how the cylinder draws on the port (yes a new cam would be designed to optimize the long rod).

 

you said engine builder...?...


anyhow, Shaun, how did the stroker kit come along?...also bumped your manifold pressure ratio wondering what you found.


I'm glad Shaun is in this thread as he can throw realistic con's into my design reasons/elements. All input is appreciated...just looking to make the 2.0 a bit punchier, more rev happy and less boost dependant...more like a subie

also while still attempting to play a CFM game, just need to work on some valvetrain bits.

 

where does it say engineer???