Evo Bottom End--What's letting go?
 

On a consistant basis I have been reading about the torque on stock frame turbos taking out the bootm end of the evo engines..Many seem to blame how fast the torque comes up on someof the newer turbos-- I can't see that as the real problem.. Question is for those who have lost a rod-- what happening?

1) Spun bearings? No one has mentioned this as a problem, but asking.

2) Is it actually the rods themselves--so the rod is breaking above the bearing and its not a rod bolt coming apart?

3) The rod bolts are letting go?

4) No one mentioned losing a crank---so I assume those aren't breaking? Have seen this in other cars--but thats a different story.

I just want to get a grip on what the real weak link is in the bottom end. I dont want to start changing parts to " be sure". So from those with experience, whats breaking? I understand that 380-400wt is the magic threshold.

Discuss...

Most TQ related breakages I've seen on here are rods snapping and playing peek a boo with the outside world.

Look through the "Various My Blown Engine" sticky thread. You'll get tons of faiures and pics man

Broken rods seem to be happening in 5th gear at low rpms..

Thats what a lot of folks are suggesting, question is was it the rod bolts that can't handle the pressue or the rod itself? Not hearing of twisted rods like the Cyclones were used to seeing so thinking what's breaking are the rod bolts. Looking for confirmation.{thumbup}

Yes lots of load on the stock rod bolts will tend to do this..the problem is exactly the Turbo hits to hard at low rpms to fast and the ramp rate is to hard..some tuners will use a soft blow tune to ramp up the Turbo later and have the tq hit in the mid Range vs,s low rpms which put lots of stress on the rods ..the best tuner for keeping stock blocks happy is Arron from English racing he knows how to make the tq hit in a unique way and have the horsepower climb instead of the tq.His limit is 400 but many people have gotton away with 450 but that's not every case.

I blew my iX block cuz #3 Rod broke.
overboosted and through alot of trq through her.

crazy how our cast aluminum pistons hold more then our forged steal rods can.

Yep, just got all the parts for my new build. But if you search youll see my pictures. And its exactly that, the stock rods literally shatter and punch at least a hole in the block. Mine however though it was better to make two( front and back) and then the other half hang around to score the **** out of my crank.:lol:

90% of tuners wont go over 400ft-lbs on the stock bottom end. I made 458ft-lbs and like i said before, punched two holes in the block, two holes in the oil pan, and took half the block/ crank with it..

I agree with the low rpm torque breaking stock rods. From what I have read the rod bolts usually let go at high rpms not load.

So upgrading to stronger rod bolts should remedy the problem assuming tune is correct and not punching in low rpm in 5th gear? I have heard of the low rpm 5th gear problems but as long as you are in higher rpms in 5th should one be safe?

I wouldn't recommend any high load pulls at any rpm in 5th gear as it's the longest gear and will put the motor under the most load/stress. These bottom end's aren't as fragile as most think. Mine took a solid 3 years of every day abuse on the stock turbo @ over 430wtq, FP Red @ over 520wtq, FP Black @ over 580wtq @46psi by 4050rpms (boost controller malfunction), and Hta3582 @ 478wtq before the motor finally gave out. My cyl2 rod failed a day or so after my 9 second pass during normal cruising on a highway ironically. :lol: The rod bolt's look perfectly fine.

All good to know--so it sounds like rods and rod bolts...very interesting. Others pls chime in with your experiences-- Thx to those who have already shed some light on this. I have a new HKS turbo, I dont spin high rpms and I tend to load the motor up in the high gears, I also like torque more then HP--so you see my delima/curiousity. I am still on the stock clutch at 60k-- so i dont beat on my car. then again I have a few years on most of you as well. lol.

Ryu were you wot in 5 the gear??I agree with having to much load in higher gears not safe I only go part to half throttle at the most to pass someone maybe 12 psi at the most.

I spun a bearing at 7500 rpms.. Cylinder 4.

No, very rarely if ever under wot in 5th-- just saying I dont gear down often and just use the throttle to accelerate.. even at part throttle I see 15-20 psi.

Stock framed Turbo??I would be a miracle for me to see 15 -20 psi at part throttle that's why I do it.I'm on a big t3 Turbo and I don't get full boost till 5,100rpms also two is 400 or less.The one bad thing about the stock framed turbos they smack way to hard early and there violent when they hit full boost.