with all this talk about reliability - whens somebody going to organize

"Marauding Miatas 2011"

one-lap-of-america style tour of the best tracks in a region while terrorizing the local v8/subi/evo/etc inhabitants.

some thoughts: select 2 weeks in summer to hit 7 tracks for an easy vacation. or perhaps go crazy and do 5 in one week.

if enough folks participated, could probably ask for own run group.

 

I would be flabbergasted if more than 4 cars on this site could survive 7 track days in 14 days. Mine probably wouldn't.

 

What happened to the stroker that made you swap it out -- the consumption or something worse?

 

Started consuming more oil, again.

Oil wetting down spark plugs, again.

Burnt exhaust valve, again.

Wear and score marks on cylinder walls, again.

Damage to rod and main bearings, again.

I saw no degradation in compression or loss of power along the way just increased oil consumption and increasing oil smoke out the tailpipe over time, especially under load. I think the burnt exaust valve stems from the problems caused by Oil in the combustion chamber.

I cannot say with certainty what exactly is causing the issues but running the same turbo setup at the same boost with a stock un-touched internals in the motor has not produced the same wear degradation over time as the built motor. Lost a bit of torque and power due to less displacement is all.

Bob

 

+1

But they might if driven like a total wus.

I have been a wus this year by doing more autocross and less track. Much less time spent fixing the car that way.

Bob

 

Wow. Consumption during load... maybe oil carryover, did you ever work up the air/oil separator you were talking about?

 

Yes Crank case ventilation was and is excellent now and then. I never had any significant Blow By and there was no PCV system that would allow blow by to get back into the intake. Always had good compression and made good power. Oil consumption was under load not vacuum.

I think a combination of stock oil squirters and pistons with gas ports to the oil control rings positioned so they serve as high pressure oil injectors for the rigs is a major contributor to oil consumption. but it still doesn't explain the rapid wear rate.

When it goes back together the squirters will be plugged. FWIW FM is now plugging all the squirters on theire builds. Bill said he was going to do it to mine but he didnt.

Bob

 

Hmm if you have good (low) crankcase pressures then I would think that high rpm + vac would tend to drive the most oil past the rings. That's when you have the highest delta p across the ring pack & the squirters squirting... or what am I missing?

 

Now that is interesting. I wonder what the implications are for piston cooling?

 

To be fair, One Lap of America isn't like doing a full track day. I think you only get a couple laps and they keep your best lap time.

 

this thread is awesome. thank you guys for shaving so much information!


on a seperate note, do you guys think its better to have a turbo water AND oil cooled? or would you prefer just oil cooled? i think the water cooling is nice but more parts that can physically break...maybe if done properly its not a big deal?

 

i can't speak from personal experience, but a garrett employee stated following on another forum about garrett ball bearing turbos:

he followed up with follow link (half way down has discussion of importance of water cooling): http://www.turbobygarrett.com/turbob...imization.html

ref: http://nissanroadracing.com/showpost...9&postcount=32

 

you are the man! thank you for the info!

 

That is what I thought too. But I could run down a long hill in high rpm vaccume for a long time and not see any oil smoke. Floor it from a steady cruise on flat ground and leave a smoke screen after it came up to full boost. Catch can venting both sides of the valve cover and the lower block to atmosphere wouldn’t collect hardly anything unless I was doing hard cornering on a track and then I think slosh was a big player. I get as much oil in my catch can now but nothing showing up on the plugs like it was.

I suspect others running the **** out of there cars on the track with aftermarket pistons are also having oil control issues. Just haven’t identified it. I suspect the low height Stroker pistons makes it worse.

Bob

 

Heck of a situation. Good troubleshooting btw. Could this be ring flutter?

 

I’m theorizing that it doesn’t make much difference. The only pistons I have seen that were made to take full advantage of those squinters are the pistons Mazda put in the GTR engine. They had an internal oil galley channeling the oil through them and iron ring lands. The stock pistons also don’t have gas vent holes going from the oil control ring area to the inside of the skirt area that is being blasted with oil spray like I think all the aftermarket pistons do.

Bob

 

another tidbit on the water cooling which i didn't see mentioned on the web page sited earlier:

 

I haven't seen it if I am, and I just ran 5-hours over two days and never lost any measurable oil while checking plugs the first day for a spark problem. I have no aero however, so I don't see the lateral g-loading that you do.

 

Rob S (Garrett guy in those links) knows what's up.

Summary: if you want your bb turbo to fail, do not attach water lines to it.

 

This happened to a friend of mine with a turbo setup on his NASA TTC-prepped turbo Miata at ~200rwhp. Fortunately, he noticed the problem before the cable completely froze up and we fixed in in the paddock. Be aware of this failure mode if you're running a turbo on the track.

And to add another data point - he's been using inconel studs on his car for the past several events, and that seems to have eliminated his problems with manifold bolts stretching and resultant warping of the mating surfaces.