And as a final tribute, I present to you the many faces of the Wreck Racing Miata.
As purchased
$2007 Challenge
$2008 Challenge
$2009 Challenge
$2010 Challenge
2011 Ultimate Track Car Challenge
2013 Ultimate Track Car Challenge
Oh man, that's a lot of engine trouble! Good job making it to the UTCC in the first place, though.
Yeah, the worst part is we're still unsure of why some of the failures happened. It seemed like it was a different cause each time. We've heard these bottom ends are supposed to be good for upwards of 800 hp with no modifications, so oil starvation seems a likely cause, but then why did the bearings go out on the dyno? More questions than answers unfortunately.
Thanks for the kind words
You could be detonating. Detonation is a killer on rods and rod bearings.
Pat wrote: You could be detonating. Detonation is a killer on rods and rod bearings.
That was kinda my thought at first...
Any idea what your IATs are like with that setup?
Bowenaero wrote: Yeah, the worst part is we're still unsure of why some of the failures happened. It seemed like it was a different cause each time. We've heard these bottom ends are supposed to be good for upwards of 800 hp with no modifications, so oil starvation seems a likely cause, but then why did the bearings go out on the dyno? More questions than answers unfortunately. Thanks for the kind words
This 800hp threshold may hold up on the street but the track is a completely different environment. The anecdotal evidence of the 800 hp possibility maybe from street racers who aren't running a motor as hard as you are on the track.
My Chump team was racing a 1991 Supra with the stock I6 motor. The motor designation is a 7m-GE. This is the naturally aspirated motor. Supposedly the motor is rock solid with the only issue being a head gasket that is not properly torqued from the factory. The problem they had with it was the bottom end kept grenading. They went through 3 motors in that car. It could only maintain a race pace for about 20 minutes before it would blow chunks out the bottom end. The ultimate fix was replacing the motor with an LS3.
Maybe it's time for a Ford 5.0 swap?
Swank Force One wrote:Pat wrote: You could be detonating. Detonation is a killer on rods and rod bearings.That was kinda my thought at first... Any idea what your IATs are like with that setup?
Well, the pistons all looked really good, so I didn't suspect that. I guess there could be detonation elsewhere in the combustion chamber. I doubt that's it though, since we were running pretty low boost, E85, and super-conservative fuel and ignition maps. I'll have to check the datalogs for IATs.
Thanks for the suggestions.
Xceler8x wrote: This 800hp threshold may hold up on the street but the track is a completely different environment. The anecdotal evidence of the 800 hp possibility maybe from street racers who aren't running a motor as hard as you are on the track.
Yeah, definitely. I would still expect more than 300 whp though.
This car is turbo and supercharged 1uz powered, sees lots of track time. Holds together just fine. It's a "built" motor now, but still made lots of power for years under lots of abuse when unopened.
There's a bunch of videos up on youtube of a turbo 1uz powered "ute" of some sort hooning around a track really damn hard as well.
In reply to Swank Force One:
HHHHHHHHHHHHHHNNNNNNNNNNNNNNGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGHHHHHHHH
God I love that car.
Supercharged, twin turbo, 1uz.
RWD.
Was a Celica GT4 Grp A, which pisses some people off, but meh. It's awesome.
I'm sticking with an oiling problem. I don't think it's cornering G's, I think you're loading up on oil in the top end of the motor, which is starving the bearings. Are these motors priority valvetrain oiling? I'd ream out the drainbacks, maybe add some outside lines from the back rear of the cam covers to the oil pan, or build a DIY dry-sump. Issues like these are why a lot of road-race engines are "priority main" oiling systems.
Were you able to determine which bearing lost it first in each scenario?
blown 1uz miata! madness! love it.
I so badly wanted this driveline in my 77 celica liftback. Maybe the next one. I bet turbos would be more gentle on the lower end?
Javelin wrote: I'm sticking with an oiling problem. I don't think it's cornering G's, I think you're loading up on oil in the top end of the motor, which is starving the bearings. Are these motors priority valvetrain oiling? I'd ream out the drainbacks, maybe add some outside lines from the back rear of the cam covers to the oil pan, or build a DIY dry-sump. Issues like these are why a lot of road-race engines are "priority main" oiling systems.
Swank Force One wrote: Were you able to determine which bearing lost it first in each scenario?
It was a different one each time. The first engine spun #5/6 on the dyno. The third engine spun #4 on track. I'll have to check the second engine tonight to see which one lost it first. EDIT: looks like the second engine ate rod bearing 3 first.
Swank Force One wrote: Any idea what your IATs are like with that setup?
This is the datalog when the rods let go on the dyno.
is the oil pan baffled?
Autolex wrote: is the oil pan baffled?
Based on an earlier picture, I believe it is a baffled/modified pan.
Couple of other ideas to check out.
-Make sure that the pick up is not too close to the pan floor.
-Make sure that oil is able to return to the pick up area through the baffles fast enough.
-How is the bottom end vented to the top end on that motor? If it's vented through the oil returns, and you have just a bit of blowby as you introduce boost, you could be blocking oil return to the pan with blow by vapors rising up to the valve cover, which I'm assuming is where the pcv venting is on that motor. An separate block vent bent would help with this some.
And a question: are all these popped motors dying at high rpm? Based on what I see on that dyno plot, I'm not sure why you'd spin it past 6k anyway.
Pan is baffled.
Pat wrote: Couple of other ideas to check out. -Make sure that the pick up is not too close to the pan floor. -How is the bottom end vented to the top end on that motor? If it's vented through the oil returns, and you have just a bit of blowby as you introduce boost, you could be blocking oil return to the pan with blow by vapors rising up to the valve cover, which I'm assuming is where the pcv venting is on that motor. An separate block vent bent would help with this some.
These are both good suggestions . Javenlin mentioned that second one as well. I think we need to double check the 1st one and address the second one before the car sees the track again.
Thanks for the tips, guys!
Pat wrote: Couple of other ideas to check out. -Make sure that the pick up is not too close to the pan floor.
The oil pickup is in fact quite close to the pan floor. Why is that bad? Flow restriction?
Pat wrote: -Make sure that oil is able to return to the pick up area through the baffles fast enough.
The baffling is pretty minimal so I doubt this is the issue, but good thought.
Pat wrote: -How is the bottom end vented to the top end on that motor? If it's vented through the oil returns, and you have just a bit of blowby as you introduce boost, you could be blocking oil return to the pan with blow by vapors rising up to the valve cover, which I'm assuming is where the pcv venting is on that motor. An separate block vent bent would help with this some.
This idea sounds very promising!
We've actually had a lot of issues with crankcase pressurization, which confused us since we're running pretty low boost (see datalog - ~6psi) and have two big crankcase vent hoses and a big, open catchcan. The PCV goes through the valve covers, as you suggested. In the past, we've popped out several seals from excessive blowby, including a RMS and the valve cover plug thing that's missing here:
In addition, the crankcase pressure causes oil to shoot out of the dipstick tube unless it's capped/plugged.
I believe the PCV sharing a path with the oil return (and the two not sharing well) would explain both phenomena (oil starvation and excessive crankcase pressure).
Pat wrote: And a question: are all these popped motors dying at high rpm? Based on what I see on that dyno plot, I'm not sure why you'd spin it past 6k anyway.
No. I know the last two failures occurred at <6k RPM. It's hard to tell what speed exactly though, since the bearings went out slowly every time except on the dyno.
And that dyno plot was generated before much of the upper speed range was tuned, so I'm sure the final curve looked somewhat different. Even so, I'm sure the S/C and heads are still becoming restrictions up there.
And I updated the post above with which bearing went out first on the second engine (#3).
If the pick up is too close, at higher rpm/demand, the oil may not fill back into the small space between the pan and the pick up without causing too much of a flow restriction. You want enough space to allow for a steady, low restriction supply but not too much space where the pick up can become uncovered. I don't recall off the top of my head what I set mine at (it's written down at home), but on pans that I've baffled, I've actually raised the pick up from the floor of the pan by 1/4-3/8" more than stock. My thought was that with the baffles controlling oil slosh, I had more wiggle room to increase the oil supply under the pick up.
On the drainback/blow by issue, that huge. If you're creating enough crankcase pressure to blow out seals and push oil out of the dipstick, you have an issue there. That tells me that your ventilation is not nearly enough for how loose these used motors are, but you're also likely pushing oil back up the drainbacks. What I've done on my motors (Dodge 2.2's) is drill/tap the block high enough to be well out of the oil and do the same on the valve cover. I then run a 3/4" hose directly from the block to the valve cover. In doing this, it creates a pathway for unwanted crank case pressures to escape to the top of the motor, which then get pulled out through the pcv system or pushed out through the secondary vent I typically install. Doing this allows the drainbacks to actually drain oil back to the pan.
You could vent the block to atmosphere, but you may have some issues with oil misting unless you go through a catch can. The reason I've gone to the valve cover is that it runs to the highest part of the motor which helps contain the mess and I can do it without having to run multiple catch cans. Plus, under manifold vacuum conditions, the stock pcv system is still operational and pulling from the crankcase instead of waiting for pressure to push it out.
pat knows boost. much good info in that post up there.
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