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Discussion Starter · #1 ·
Hey Guys,

I was just wondering, when should you upgrade your internals? First, HOW do internals fail? Is it dependant upon the amount of power your engine is putting out, or is it dependant upon the amount of pressure/boost you run?

So, if I had a larger turbo running at 1.2 bar (or less), would I need internals? Even though the power would be far greater, the boost is relatively low? Yes/No? OR is it power dependant?


Discussion Starter · #2 ·
Disclaimer: I am no expert, some of the following may need correction :)

Internals fail when they take more mechanical stress (or heat, or both combined) than the materials can handle.

It's dependant more on torque (and air mass for compression forces on the piston) than on power. 350bhp/310ft lb (tuned road evo) is less stressful than 310bhp/400ft lbs (wrc tuned evo) on the various engine bits.

As for when... well, there's various replies. Personally I'd upgrade as soon as I started tuning, as I'm concerned with engine life and reliability. I'd rather run bits at 70% of rated capacity (ie max torque/power figures) than 95%, as they are much less likely to fail. Given the conrods/ARP bolts are often quoted as the weakest link in the 4G63, I'd be tempted to get these done before I even upped the boost from standard, although people on here have been running 1.4/1.5 bar (original turbo) on the standard internals without experiencing problems. Others have done the same and blown engines within a month.

Blade and Just Custard are the resident tuning experts (both have slightly differing views on tuning too). I'd pick their brains, as they both have experience of taking evo's pretty far on the tuning curve. Lightspeed is the god of turbo's :D and most of the guys here have done breathing and boost mods.

Anyone else got any better (more accurate border|EQU| 0 align|EQU| absmiddle >) info?


Discussion Starter · #3 ·
i am no four stroke expert.....just a fast learner !

i believe my engine has survived because,
its set up 100 % correctly.......there is a lot of bullshit on here !
i warm it up.....i mean i really warm it up before using it
it has a recirculating bov
it has ample cooling capacity....both water and oil.

and,my style of driving is that of a short shifter,(anyone remember Audi Quattros?)
so i spend less time at high revs,yet go much faster.(than std car)

the std pistons will stand 2 bar low revs,1.7 bar top revs
forged pistons are not needed below this IF the car is set up right
i do know a little bit about pistons !

Discussion Starter · #5 ·
Original Post:
First, HOW do internals fail?
They fail through too high boost (torque) mid range or through overheating. Result: holed piston or bent connecting rod. :(

Original Post:
Is it dependant upon the amount of power your engine is putting out, or is it dependant upon the amount of pressure/boost you run?
These two options you suggest are basically the same thing. :)

Discussion Starter · #6 ·
if your motor detonates...or runs lean and hot, then it will blow up, internals or not
provided this is not a problem then mechanical strength next issue and strain basically goes up by the square of engine speed
rods said to be the weakest link, said to fail between 375 and 400hp
and also fatigue ie can run high power but for how long?


Discussion Starter · #7 ·
Interesting thread. I pose another question.

What is the typical failure mode of a con rod in a correctly mapped EVO engine (no detonation)?

We all hear the importance of upgrading rod bolts which in my opinion will only be failing under tension ie. forces generated by High RPM where max acceleration peaks at Top dead center. If the rod actually bends or fails under compression then it clearly must be due to a torque that over loads the rod on the power stroke.....Absolutely nothing to do with rod bolt strength. Is it a bending force when the rod is at it's max angle to the crank? If in compression then aren't we are all wasting our time uprating rod bolts?

Discussion Starter · #8 ·
yes rod bolts are a waste of time and money,below 350/350
i can see the rods bending after this,which is why i am having some made !

Discussion Starter · #9 ·
Just curious , why r u having rods made , there r as u will obviously know a number of top 1's on the market.

Discussion Starter · #10 ·
i can get them made very cost effectively,i am sure more people will mod as the costs come down.
and i like to do things my way,rather than take the easy route.
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