hi today a friend told me that the classic shape skooby type r's have weak bottom ends. dont they have the same engines as the wrx sti's. or are there that many variations. cheers

 

STi type R's have the same engine as any other classic STI of that year, there are no differences, your mate is talking bollox basically.
ECU maps on the other hand.... they have the same map but the version 5 and 6 are known to have some issues when running uk spec fuel and are better off being mapped for our fuel as there are lean spots that can cause problems (see the P1 which runs the same jdm map with more knock correction).

Tony

 

Tony's spot on.

uzzy, if you want to know more about it, email Alistair Maine at GGR ...

 

i thought they would have the same engines. its funny because his older borther just recently sold his type r because of that reason. maybe he jus had a bottom end on its way out. he could possibly be running alot of power on standard internals but i didnt want to argue with him too much since he though he knew so much and i wanted to punch him lol.

 

With the v.5/6 STi's (especially the Type R/RA), if they're past 50k miles, then it's only a matter of time - whether soonish or much later - when the Grim Reaper comes looking for big ends...

 

Well mine is a V3 and is on 68k now so i,m praying to God daily.....

 

Why is it the bottom ends that go if its the fueling thats the weak point?

 

Stress.
Its normally det that causes the damage, or not getting the oil around the engine before ragging it (thus i give it a good 10 miles), but det causes stress on the pistons, which works its way down to the furthest point, that happens to be the bearings, its like hitting a piston with a hammer but having an egg underneath it, that egg breaks first... (hence they get remapped for uk fuel)
But there are plenty of v5's and 6's that run 100k+ miles without a rebuild.

Tony

 

Insufficient fuel and/or a low octane can cause intake temps to be hot enough so that the flame front can't burn completely in a controlled fashion by the time the piston has reached top dead centre... This is the dreaded "detonation".

It's more of an almost instantaneous 'explosion' and because the piston is still traveling upwards, the shockwave of the 'explosion' travels down through the piston/conrod and dumps the immense energy in the form of massive pressure loading into the big end bearing shells (which are deliberately designed to be the weakest link of the reciprocating parts). It can take only a few seconds of sustained detonation to weaken them enough to the point of failure...

 

Thanks Joz and Tony!

 

Another phenomenon is "pre-ignition". This is where there's a secondary - obviously unwanted - ignition source in the engine e.g. carbon build-up in the combustion chamber. If temps get too high, then the carbon deposits can literally glow as red hot embers, which instantaneously ignites the fuel as it enters the chamber, with the same consequences as outlined above...

 

Ah right, I have a thread up on this General Technical page named Annoying running problem : 2005 WRX, I was worried it could be running lean or pre det etc, could you maybe have a read and see what you think?

You sound like you know your stuff.

Thankyou!

 

Well explained Tony & Joz....