Chip

iTrader: (3)

One on the left is the rod as per the early 90s lexus V8 ive got for my calibra.

Rod in the middle is a 4.3 out of a more modern (and higher power!) lexus v8

Rod on the right is the 4.7 iron blocked engine in the big SUV's


Weird they would chose to make such a vital component so much weaker on engines with more power and torque!

Psycho Warren

iTrader: (5)

what about material and manufacturing process's?

LINCOLN

iTrader: (1)

Engineered life span?

Chip

iTrader: (3)

I think its simply a case of the early ones were just found to be massively over engineered.

The later ones are in much more powerful engines, and yet are so much weaker.

Good news if you are plannin to turbo on the early ones though of course!

Other good news is the standard crank is forged steel:



Strong as fuck pistons too, and all you need to do in order to drop the cr from 10 down to a boost friendly 9:1 is fit a set of thicker headgaskets to it, easily capable of 600bhp+ on totally standard internals then.

Not bad for an engine you can buy for 500 quid.
(well mine cost 600 but it came with a free car, lol)

Bladerider

I know, progress is amazing,

Engine oil too for example,

They're changin mine all the time !!



J.

Charlie Chalk

iTrader: (1)

Question, How do the engines make more power though? apart from being a bigger CC, what about revs?


I was always under the impression that revs kill rods, So if they dont have to rev them as hard as the smaller engines, surely that would be why they are made thinner/smaller?



Chip, whats that crank from, the V8 in your Lexus?

Azrael

The volumetric efficency makes the power so probably heads, manifolds....

Twellsie

iTrader: (1)

i would imagine its down to reducing costs, it may not look like alot of differance but across thounsands of engines, think how much steel you have not used

nilrem

i think that its down to not only over engineering as said above. but also the reduction in size not only reduces the ammount of steel used, but also decreases the moving mass, helping to increase the performance of the engine, possibly helping to increase bhp.

Bladerider

Radders,

If they have found that a certain weight of piston can withstand the power that they are getting then that in turn reduces the weight the rod has to withstand at any given engine speed. So if overkill engine 1 has pistons that weigh 800grams but actually a piston that weighs only 600grams is still strong enough then that would reduce the force on the rod by 25% for example allowing the differences seen above.

It still basically comes down to engineering for a price though as only competition engines pare down weight and excess in order to acheive maximum effeciency for a set of parameters, the only time things get reduces in regular cars is when the accountants get involved in the "Design process"

J.

Chip

iTrader: (3)

Radders, yep rods kills revs, my ones are just about safe to 9K though apparently as they are the early ones But I'll never be revving it that high anyway.

Yes its the lexus V8 they are from

Mr Whippy

Chip

iTrader: (3)

lol

oops

Steven_RW

A friend works in the industry and said "if u can reduce 10p from the production cost of a vehicle, it would be seen as a miracle"

This was referring to a high volume car manufacturer. Therefore a little bit of reduction in the "over engineered" front could save you vital pence!

RW

Chip

iTrader: (3)

Agreed, rumour has it that ford save 2 quid each on the production of a zetec engine when they came up with the design with no positive location on the cambelt (ie not using a woodruff key)

Think how many millions of zetecs have been made, and thats a fucking good saving by whoever thought the idea up when the engine was designed initially!

Rick

Also in todays emission and efficiency orientated world they need less energy to move. Some say EVO rods are poor, but yet the engine is more responsive compared to the massively stronger YB.

_DAN_

Could the reason for the SUV rods being 'weaker' be that the intended use of them and the engine is in a car mainly driven by normal people as a run about. Soccer moms and such like.

xr-stu

surely its high cylinder pressures that kill (bend) rods? and revs that kill (snap) rod bolts.

steel is stronger in tension than it is in compression.

i wrote out a massive reply but lost my point 1/2 way through so deleted it

Chip

iTrader: (3)

No, its far more common for rods to dies as a result of revs, they stretch and let go.
On 98 RON fuel its very unusual for a rod to see enough pressure to bend it unless you are talking about a scenario where you have monster amounts of detonation occurring.

xr-stu

i would imagine its at/after TDC when the pistons still trying to go north that things go wrong.

ive heard of rods snapping at random times though, not even when the cars being driven hard.

pani_k

iTrader: (1)

Chip, how have you concluded that the more modern rods are weaker? Simply due to the fact that they are thinner in design and use less material? What about the different stress/strain tests that each rod goes through? Are they still found to be weaker subjected to the same tests? Tensile strength for example. Do you know for a fact that the modern ones will break before the older ones?

Not having a go at you in any way by the way, just curious that's all as to how you concluded the modern ones are weaker . Want to know the reasoning behind it

JjCoDeX75

If my memory serves me correctly, a lot of damage occurs to engines through poor tuning - ie detonation.

Could it be that now the ECUs are that much more sophisticated, and as such better at preventing detination that the tolerances may be reduced?

I could of course be way off base as usual!

JJ