20 replies to this topic

[colinlucas]

Hey everyone!

 

Looking for some advice as to what went wrong and steps to correct:

99 Miata

 

Last weekend we ran the 3 hour enduro and the next day ran a 30 min sprint race.

After the enduro we did a dyno and came out with 108hp with the restrictor in place (120 without). This is an engine that had done 120hp in a previous build. Car was rebuilt about 4 race hours ago with new rods / pistons after suffering failure from broken water hose.

 

3/4 of the way through the sprint race we heard what sounded like bearing noise and retired.

 

Pulled the engine and found:

- Metal shavings in oil pan

- Bent connecting rod

- Bearings on same rod turned into splinters

- All other bearings / rods / pistons looked fine

- 1.5 quarts of oil left in the pan.

- No obvious oil leaks anywhere on the engine

- Valves looked OK visually, left it with the machine shop to verify

- Cylinder walls looked fine

- Crankshaft took enough damage to be put out to pasture

 

Just ordered the oil pressure / water temp gauge kit from advanced-auto. Trying to figure out where the oil went (bad rings?) and any additional next steps to take (Fuel / Air gauge?)

 

Colin

[callumhay]

Hi Colin

Mazda had an issue with the seat in the block for the thrust bearings. For sure it was in the 99 miatas and there is info on it on the internet. I'm wondering if that was a possibility in your motor. Checking endplay on the crankshaft before rebuilding is a way to check for this issue. The problem I think was caused by incorrect machining of the thrust washer seats on the block. I had a friend who bought a used Miata only to find tons of metal flings in the oil which is a sign of the problem. Based on what you said it sounds like you are going to need a new motor. If you are going to re use the block, it might be wise to consider the thrust bearing as an issue and start with another motor.

Hope this helps

Cal

[davew]

I am not an engine builder!!!!

 

99% of the time when a fresh Miata engine (really any fresh engine) fails, it is an error in assembly. Bearing clearance, out of round rod, dirt, wrong torque, etc.

 

Anyone can assemble a motor in 4-5 hours. There is a reason any professional engine builder takes 25-30 hours to build a motor. The work is all in the details.

 

Again, I don't build engines. When I see a piston, it is a BAD DAY.

 

Dave

[Ron Alan]

^^^^Zero claim of any expertise but I will disagree with you Dave...at least on the 99% fault claim. I do agree there has to be a percentage of "assembly" failures but I think there are other reasons for failures that have nothing to do with the engine builder but everything to do with what happens after that motor has been Installed! OR.....original design??

 

The most common reason we end up with donor cars is an OEM rod knock or complete failure...always #3 or #4 cylinder! The last 5 NB cars I picked up had this problem and mileage was from 70 k to 200k. Lack of maintenance? Maybe but I'm convinced there is some weak point in the design that helps this. Though I can speculate with my limited knowledge that's all it would be...just speculation. My 65k OEM bottom end #4 rod bearing/rod/piston failed catastrophically after 5 years of racing! This I accepted!

 

Break in procedure, break in oil, oil, fuel mixture(lean), water temp, over rev, fuel(low octane)...combinations of these and a lack of knowledge or paying attention to these are reasons it is difficult in my mind to lay it back on the builder...even if that is the easiest thing to do!!

 

I dont think there is a motor builder out there that hasnt had this specific failure that started this thread. For a period of time many were blaming the quality of the rod bearings that Mazda was supplying...no idea if that was ever proven or changed?

 

It would be an incredible public service if someone wants to share any info they have on why we see so many #4 hole failures(#3 also but less) and possible procedures to avoid this?????

[Jim Drago]

I am not an engine builder!!!!

 

99% of the time when a fresh Miata engine (really any fresh engine) fails, it is an error in assembly. Bearing clearance, out of round rod, dirt, wrong torque, etc.

 

Anyone can assemble a motor in 4-5 hours. There is a reason any professional engine builder takes 25-30 hours to build a motor. The work is all in the details.

 

Again, I don't build engines. When I see a piston, it is a BAD DAY.

 

Dave

On weekend one.. if not obvious install issue which is abundant as well ... I would knock the number down to 90-95% and agree

 

Jim

[davew]

Ron, I am not talking about 70k mile street motors or 5 year old race motors. My statement is simply about 3 hour old race motors.

 

In the past 15 years of experience with SM motors, I have had a single, fresh motor failure from a pro builder. This includes X-Factor, ESR, Stewart and Rossini. Yet I have seen multiple fresh motor failures from individual builders. Some of whom have been professional engine builders (of the V8 kind).

 

Could it have been abuse (over rev) lack of oil (I call that abuse also) poor break in procedure (I blame that on the engine builder not specifying or the installer not completing his job), or poor quality of parts (engine builders choice)

 

I will stand by my statement that when a fresh engine goes bad, it almost always a builder issue

[Bench Racer]

Public Service Announcement for Salvage Yard Miata Engines:

 

My clutch interlock switch will have a bypass. Start engine without pushing pedal to floor. Yes, I understand Pro motors shouldn't be an issue, this'll be a bit of thrust bearing longevity.

 

Life is a continuous learning lesson.

 

 http://www.solomiata...ingfailure.html

[Ron Alan]

Ron, I am not talking about 70k mile street motors or 5 year old race motors. My statement is simply about 3 hour old race motors.

 

In the past 15 years of experience with SM motors, I have had a single, fresh motor failure from a pro builder. This includes X-Factor, ESR, Stewart and Rossini. Yet I have seen multiple fresh motor failures from individual builders. Some of whom have been professional engine builders (of the V8 kind).

 

Could it have been abuse (over rev) lack of oil (I call that abuse also) poor break in procedure (I blame that on the engine builder not specifying or the installer not completing his job), or poor quality of parts (engine builders choice)

 

I will stand by my statement that when a fresh engine goes bad, it almost always a builder issue

Better said and understood!  And I will agree first day on dyno, first day on track I to would look to the builder! But at some point early on the potential for things outside a builders control become more and more of a potential.

 

Maybe the very common bearing failure(be it 500 or 200k miles) is for a different thread...but is there in fact is an inherent weak point? 

[OctaneNation]

Any crap left in the oiling system from the previous engine trauma?

[colinlucas]

Any crap left in the oiling system from the previous engine trauma?

 

Thank you all for the suggestions thus far. The engine is with the machine shop and I should know if any of the "something stuck open / clearances" opinions are correct by this weekend. 

 

This build was with a new oil pump / strainer direct from Mazda. We were extremely careful with the build using only Mazda supplied parts / gaskets. 

 

Break in was to run it at 2500 rpm for 10 min with non synthetic, replace oil/filter, repeat. Then use mazda filter / RP oil. Ill be switching to Schaeffer 20/50 for the final oil this time around.

[davew]

Again, I am not an engine builder, but here is my break in procedure

 

Start engine, warm to operating temp. Non synthetic oil, I like Rotella diesal oil

change oil and filter, cut filter to inspect. Rotella again

break in on dyno for at least 1 hour, varying speeds.

Cool to room temp, run for 20 minutes on dyno

Do baseline tuning, light timing and a little rich

Run one day, 2-4 sessions on track. low revs first session. Carefull of no over revs.

Change oil to your favorite synthetic race oil

Dyno for "final" tune.

 

If you only ran 20 minutes on break in oil then went to RP (Royal Purple???) you would have never gotten the rings to seal. Remeber these rings are street car rings. They do not seat in a few minites. They are designed for 200,000 miles.

 

Maybe one of the engine builders will give their procedures

Dave

[Ron Alan]

^^^ Just a note on using a heavier oil at start up on the 1st gen motors...it may take awhile and some temp to get the HLA's to pump up!

 

Dave...on your first step are you just letting it idle up to temp or are you taking the rpm's up and down a little?

[colinlucas]

Again, I am not an engine builder, but here is my break in procedure

 

Start engine, warm to operating temp. Non synthetic oil, I like Rotella diesal oil

change oil and filter, cut filter to inspect. Rotella again

break in on dyno for at least 1 hour, varying speeds.

Cool to room temp, run for 20 minutes on dyno

Do baseline tuning, light timing and a little rich

Run one day, 2-4 sessions on track. low revs first session. Carefull of no over revs.

Change oil to your favorite synthetic race oil

Dyno for "final" tune.

 

If you only ran 20 minutes on break in oil then went to RP (Royal Purple???) you would have never gotten the rings to seal. Remeber these rings are street car rings. They do not seat in a few minites. They are designed for 200,000 miles.

 

Maybe one of the engine builders will give their procedures

Dave

 

Sorry, not 10 min each. 10 min first run and 1 hour second run with varying RPMs. RP = Royal Purple. But I completely agree with you looking back that this was not enough time with non synthetic oil. Any recommendations for Dynos near the Pasadena, CA area? 

[davew]

up-down, no load 3000 rpm max

[colinlucas]

up-down, no load 3000 rpm max

Dave, to interpret, that would be for the "varying RPMs" after the first oil change?

[davew]

^^^ Just a note on using a heavier oil at start up on the 1st gen motors...it may take awhile and some temp to get the HLA's to pump up!

 

Dave...on your first step are you just letting it idle up to temp or are you taking the rpm's up and down a little?

 

Answering this question ^^^^^^

 

 

up-down, no load 3000 rpm max

[luvin_the_rings]

Sorry, not 10 min each. 10 min first run and 1 hour second run with varying RPMs. RP = Royal Purple. But I completely agree with you looking back that this was not enough time with non synthetic oil. Any recommendations for Dynos near the Pasadena, CA area? 

 

 

BISIMOTO in Ontario does really good work and has a degree in chemical engineering.  We have lots of hours on his Dynapacks. 

 

http://bisimoto.com/2015/

[Steve Scheifler]

How long and under what conditions it takes to seat rings depends in large part on the cylinder hone and ring tension, (and ring material and design though we should all be the same there). That said, I disagree with the break in procedures stated above. I did a lengthy post on this years ago and it received an endorsement from someone from Mazda Comp. The short description is Tough Love, and You get only 1 chance to make a good first impression. The good news is that it doesn't impact the probability of infant mortality so look elsewhere for the cause of catastrophic failures.

[steveracer]

Warm it up and check for leaks, then go twist it's tail HARD. WOT 3rd & 4th gear-lots of load and let it coast down to 2k-3k rpm in 3rd then do it again 8-10 times.

 

Pressure and vacuum sets rings...IMHO.

 

Haven't had a dog or a smoker doing it this way and longevity is good also. Worth what you paid for it...

[Ron Alan]

How long and under what conditions it takes to seat rings depends in large part on the cylinder hone and ring tension, (and ring material and design though we should all be the same there). That said, I disagree with the break in procedures stated above. I did a lengthy post on this years ago and it received an endorsement from someone from Mazda Comp. The short description is Tough Love, and You get only 1 chance to make a good first impression. The good news is that it doesn't impact the probability of infant mortality so look elsewhere for the cause of catastrophic failures.

Re-post the endorsed version!