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You young blokes have all the fun! I'm closer to the end of my 70s than the start, and still buggerising around with cars, so don't talk to me about the rationality of this pastime .... let alone the wisdom of pouring money into it..
I tell myself that while I can do it, I will do it, after all the kids will only waste it buying food or paying a mortgage if I don't beat them to it. And since I can't take it with me, I'm not left with much choice.
You young blokes have all the fun! I'm closer to the end of my 70s than the start, and still buggerising around with cars, so don't talk to me about the rationality of this pastime .... let alone the wisdom of pouring money into it..
I tell myself that while I can do it, I will do it, after all the kids will only waste it buying food or paying a mortgage if I don't beat them to it. And since I can't take it with me, I'm not left with much choice.
Here, here!
The block has been dropped off at the machine shop this morning. The new Wiseco's are in my possession. I have access to a pressure washer and I'm not afraid to use it! I've got an "alternate head" at my disposal to use with the refreshed block. The flat-top manifold needs a once-over, so that's on the plate for this week. I've ordered some new valves (the old ones are in fair shape except for cylinder 4, so I might as well replace them all). So I guess I'll be doing some head-work until the new block is ready.
I sent the injectors off to be tested (hoping that #4 would be bad in some way and I would have an answer as to why that piston - and ONLY that piston - effectively melted. Here's what I got back;
Roger, We had 4 injectors that showed up to our shop. We did an initial flow test on your injectors, and they tested out well, with no major issues. We cleaned them at your request, they all improved, and they are ready to ship back. The injectors have new filters, top and bottom o rings and are ready to install into the vehicle. The old o rings are being shipped back in the box for spares.
So, now the mystery deepens. I'll be tearing the injector harness apart tomorrow. Maybe I'll find a short or something else that might explain what happened. SOMETHING went wrong in #4 and right now, I don't have a clue and it's making me paranoid!!
My guess would be related to internal cylinder temperature. I've broken a stock piston twice (split in half, not melted).
First time was 28 PSI boost on E85 and too much timing. Around 350whp at the time.
Second time was 22 PSI boost supercharged, E85, with insane amount of water injection and 13:1 AFR (gasoline scale). Pulled like.... It was insane. 350whp no doubt, possibly higher when it broke. Did not detonate in either case.
What boost/fuel/AFR/power level were you running when it failed?
I'd also get some high zoom pics of all the spark plugs, see if 1-3 show anything that can tell you what happened to cyl 4.
My guess would be related to internal cylinder temperature. I've broken a stock piston twice (split in half, not melted).
First time was 28 PSI boost on E85 and too much timing. Around 350whp at the time.
Second time was 22 PSI boost supercharged, E85, with insane amount of water injection and 13:1 AFR (gasoline scale). Pulled like.... It was insane. 350whp no doubt, possibly higher when it broke. Did not detonate in either case.
What boost/fuel/AFR/power level were you running when it failed?
I'd also get some high zoom pics of all the spark plugs, see if 1-3 show anything that can tell you what happened to cyl 4.
I keep my boost limited to 200kpa (I might get spikes to less than 210 (208-9), AFR's were consistently 12.1-11.9 at WOT, with no detonation (that I've been able to detect) - and all of this is on 93 octane pump gas. I have a 6758, but I think I'm no more than 300whp, if that.
When I pulled the other plugs, they looked good; tan insulators, good conductors, no pitting, no deterioration. Number 4 was a mess, of course,
Personally, for a track car I like to run richer, 11.5-6. 11.9 might generate a lot of heat, and risk melting pistons. Oh hey, look. Your afrs are fine for an occasional street pull, generating a lot of heat, but then cooling as you cruise. I know at my local track, a fast miata will hit 100+ 2-3 times in 1.5 minutes, where as a short blast to 100 on the street is about all most will see due to traffic and police. The conditions are just so vastly different. Plus if your wideband is aged, calibration is off, tune is slightly off, instead of 11.9-12.1, you might actually be running 12-12.2 occasionally. Go a couple tenths of a point lean with a 11.5 target, and you're still pretty safe.
Whats your AITs like? Are you pulling timing with AITs over 100?
Personally, for a track car I like to run richer, 11.5-6. 11.9 might generate a lot of heat, and risk melting pistons. Oh hey, look. Your afrs are fine for an occasional street pull, generating a lot of heat, but then cooling as you cruise. I know at my local track, a fast miata will hit 100+ 2-3 times in 1.5 minutes, where as a short blast to 100 on the street is about all most will see due to traffic and police. The conditions are just so vastly different. Plus if your wideband is aged, calibration is off, tune is slightly off, instead of 11.9-12.1, you might actually be running 12-12.2 occasionally. Go a couple tenths of a point lean with a 11.5 target, and you're still pretty safe.
What's your AITs like? Are you pulling timing with AITs over 100?
Mental note for AFR's; Go richer. My wideband conditioner is indeed long in the tooth (it's a Ballenger AFR500) and I'm using a Bosch WBO2 sensor that is about 2 years old. The AFR500 has the capacity to be "calibrated, but I haven't done that since the sensor was new.
This all happened at Road Atlanta and I was regularly hitting 100+ on the back and main straights (yes, I could have been faster but RA intimidates me so I'm not WOT at either section).
Ambient temps that day were outrageous - 95+ with matching humidity. BUT my intake temps (measured by a GM sensor bunged into the outlet side of the IC) were well-behaved - no higher that 137F. This was my first foray on-track with my new-to-me MS3, so I had no adjustment to spark for AIT in place.
One data point that I haven't mentioned is that about 3 years ago(?) the plug in cylinder #4 blew out. The threads were stripped and I did a Helicoil-fix on that cylinder and didn't look back. That Helicoil has been in there through at least 5-6 track days, including another one at RA, without issues. I don't know if that is relevant to this failure, but I thought I'd mention it just to be thorough.
BTW, that head is going to be "retired" from duty. I have another head that has been collecting dust in the garage. I'm going to press it into active duty with a trip to the machine shop with new valves and a little "freshen up".
I keep my boost limited to 200kpa (I might get spikes to less than 210 (208-9), AFR's were consistently 12.1-11.9 at WOT, with no detonation (that I've been able to detect) - and all of this is on 93 octane pump gas. I have a 6758, but I think I'm no more than 300whp, if that.
When I pulled the other plugs, they looked good; tan insulators, good conductors, no pitting, no deterioration. Number 4 was a mess, of course,
That could be too aggressive on pump, given it's on a track. I always targeted 11.0-11.5 AFR on pump gas when I was running stock pistons and soft timing. Even on E85, I still went for 11.3-11.5 in the midrange and 11.5-11.8 up top and and kept the timing soft for racing. I'd still recommend checking the plug insulators with 10x magnification, I bet you'll see metal on cylinder 3 if you look closely.
Also, that's a good wideband (I just bought one for my new setup running methanol) but sensors need to be checked/calibrated and replaced sometimes. I've had a bad O2 cause problems in the past.
Here's another data point that might be salient; About a 2+ months before going to RA, I was at Atlanta Motorsports Park for another track day. This was before I installed the MS3 and was running with my trusty old MS2. I thought I had my AFR's all dialed in from street tuning, but that was without any sustained WOT in upper gears (as curly pointed out). When I looked those datalogs I was SHOCKED to find out that I was getting mid to upper 12's on the one long(ish) straight there. Of course, I thought I had dodged a bullet then - but I guess I had only primed the pump for this catastrophic failure.
Silly me.
I'll get some pics of the plugs from the other cylinders tonight...
PS - I haven't looked at the impeller wheel of the turbo yet. But there's a good chance that the impeller wheel (and maybe housing) are damaged. Anybody know of a good rebuilder?
Needless to say, I've been busy (but not as busy as I could/should have been). This is essentially a new (re-built) engine. New 0.5mm bored-out block, new rods, new pistons, different head, new valves, new (to me) flat-top IM, new wiring. Everything else was ported over from the old engine. The re-buld is 80% complete as of today. I'd like to get the engine finished and back in the car this weekend, but that is just wishful thinking; there are a LOT of nit-picky things that need to be done.
Two new "adds" to the build that I'm kinda proud of;
Adding thermocouples for EGT readings and an EGT-CANbus module to get the readings into the MS3. Maybe I can catch a future meltdown before it starts, or at least before it gets too far along.
Adding a Bosch temperature/pressure sensor into the oiling system. Previously, I have separate temp and pressure sensors that fed gauges (those will remain), but signals from the the combined senor will go into the MS3 so that I can log them.
I've also painted the block, upper IM and VC a bright orange (just because) and I've named my new engine "Pumpkinhead" (because it's orange...and the VC is on top of the head...oh, never mind)! So I will soon be introducing the world to "FrankenMiata, powered by Pumpkinhead"!!
Okay. I am TOTALLY pissed (and a little bit baffled)!!
I was in the process of buttoning up the new engine and got the timing belt on in preparation for checking the valve lash. I was expecting the gaps to be a little large, since my old valves were a bit tall and the shims I was using were on the thin side. What I saw was HORRIFYING!! With the existing shims in place, there is STILL a 4mm gap between the base of the lobe circle and the top of the shim! The Manley Valve spec sheet says that they have a total valve heigh of 101.5.. and the stock valves are 102mm. So how in the hell are these clearances so stupid!
No one on earth makes shims this thick and even if they did, they probably wouldn't stay in place. I don't think there's enough of a valve seat to sink the valves that much.
I have never heard of that, what a bummer. I guess the valves were machined short? Or you got the wrong ones? That is something I would never have thought to check. Dang.
I have never heard of that, what a bummer. I guess the valves were machined short? Or you got the wrong ones? That is something I would never have thought to check. Dang.
No machining was done on the valves - they're "virgin".
This is what I ordered;
By all rights, I should NOT be having this problem.
I've used shim-under-bucket shims with shim-over-buckets before. Not ideal, but it works.
I've been scouring the interwebs for someone, anyone with a similar problem and a solution. Considering the gap I have to fill, is your solution feasible?
I've looked at valve lash caps, but the thickest I've seen of those was .080" for a 6mm stem. I don't know if I can use that and make up the remaining gap with a thicker SOB shim. But is seems that all of the places that I've used in the past for shims no longer offer them...but I've got to do something (or else revert back to the stock valves).
I took some measurements this morning and here's what I have...the actual gap between the base circle of the cams averages around 1.86mm (or.073"). Crower Cams makes a "valve lash cap" for a 6mm valve stem with an .085" thickness (larger than my gap).
Considering the scarcity of SOB shims these days, I figure that I can custom-grind these to a (semi-)exact fit with a surface grinder. Since they are "through hardened" I shouldn't have a problem with grinding off a hardened surface, but that will make grinding 16 of these little guys a real chore. Just another PITA "gotcha" compliments of Manley.
08-02-2023, 10:23 AM
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