Bottom end inspection after seeing 8,800 RPM
 

So I recently cracked a 01 piston in half running 20 PSI boost with a lot of water injection, lots of timing, not enough fuel, high AITs, on pump gas. I think I simply reached the power limit for these pistons. This motor was previously behind a EFR 7670 for 700 miles at 17 PSI, and during that time it saw 8,800 RPM probably 200 times at the drag strip. I lowered the rev limit to 8,000 for the last 1,300 miles before I cracked a piston in half.

I expected to see destroyed/heavily worn bearings from the high RPM abuse. We all KNOW BPs don't like high RPM right? But surprisingly the bearings all looked fine! When I built this bottom end in 2013 I reused the old stock bearings as they were in pretty good shape. They all had a scratch or 2 in them, but overall looked pretty good. They look the same now as they did then, no visible wear/scoring/scratching, nothing! Granted I didn't plastigauge them, but I kinda expected that I would have hammered the bearings with that high of RPM but they look just fine. And this is with a stock VVT oil pump/pressure. Crank looks just fine as well. Basically other than broke in half piston the motor looks good.

These bottom ends are pretty tough! Now I'm questioning if 8,000 rev limit is on the side of conservative after seeing how normal the bottom end looked. Also I no longer feel the need to increase the oil pressure after seeing how normal these bearings look given the load/RPM they have been through.

I have nothing to add but I have to say I appreciate all the write-ups and data points you offer even if I don't necessarily agree with your analysis every time. Keep it up!

Thanks Ryan! I will no worries. This is how you learn, by doing. There's only so much you can learn by reading, some things need to be tested.

Another thing I learned is that the new rotating assembly that was built by a race shop, the hone they did is wayyyyyy smoother than the hone I did when I built the motor. Like, a lot smoother. Mine I did it with a 220 grit bottle brush hone. Theirs looks like a 600 or so by comparison. I think I must have way over done it when I did it. I want to call them just to see if they'll tell me what they used for the final hone. I'm guessing the reason this motor had not-ideal compression was from me using the wrong hone on the block.

Pics or it didn't happen. :)

what oil.

that was not a question?

Castrol 10-30 conventional with a mazda filter.

I doubt I'll tear it apart again to take pics. If anything I should have plastigauged the bearings before so that I could do it now to compare, but I didn't. Either way they aren't destroyed, which is what I was expecting to see based on what I've read on the forums.

Thats castrol GTX right? That stuffs got mega film strength so your results make sense.

Yes sir, and yes it does! I used to run Rotella 10-W40 but I'd see wear on those running 8K redline after a year/5-10k miles. Not terrible but there was wear, it was measureable/visible. Thus why I figured with 8,800 the bottom end was probably toast.

I think 10-30 is better for factory clearances/pressures.

I switched to the Valvoline VR1 for the same reason as you. Mega film strength but the VR1 also has a nice additive package. And being only $6/quart a napa also helped that decision.

To be honest it was a few years ago when I really read into oils, and I just concluded that Rotella was not ideal for high RPM engines where film strength is important. I think they had another name for that actually, I forget. Anyways Castrol looked like a solid choice for performance/additives/price/availability so long as you're ok with keeping it changed/not running it to 280*F. I have a nice oil cooler now and after seeing this bottom end I feel much better about the switch.

Do they make VR1 in anything other than 20w-50? That's what i run in the MX6 because dem tolerances and it was the only way to keep oil pressure above like.... 30psi at redline when hot. Seemed to hold up really well to that car, wouldn't mind running it in Miata.

I have 10w30. In your area they will probably actually stock it and sell you individual quarts. Where I'm at I have to order it, so I have to buy a case of 6.

Hey Pat. How much water are/were you running? And how much of an effect does it have with allowing you to run more timing?

All of it.

Varied from .3-.5 water/fuel ratio by volume. AKA A TON of water.... Regarding detonation, none, nota, can't happen too much water.

From what I remember reading around, I thought if you injected too much water (like more than 15% I think), you could contaminate the oil and loose lubrication. You are not having this issue, right?

No I'm not, and I'm running wayyyy more than 15%. Be careful what you read on the internet. :) Especially regarding WI, there is a ton of BS out there about water injection.

What valve springs are you using for that RPM?

Heavy doubles from 949, Supertech brand, and forgot to install factory shims under the Supertech shims.

True. Your bearing surfaces are looking good, so the oil can't be contaminated. Unless the walls are being washed, but obviously you don't have any signs. On the other hand I know people that are running 50% and diesel guys are sometimes even close to 1:1...