Every post is like a Vitamin B shot of motivation
OK here's the story on my season ender. I think there is a 3.0 iteration of this thing coming...
I actually could really use some good input and thoughts on diagnostics here, so please bounce ideas around! Sorry it's so wordy.
Relevant Reference data:
- RSI stage 2 head, stage 3 cam timed 'straight up'
- 48/40mm stainless valves
- Bugpack springs with seats plunged .060" to achieve 95lbs on the seat and 205lbs over the nose
- titanium retainers
- shim-under-bucket conversion. I do not have good information on where these shims or buckets come from and would greatly appreciate any insight out there.
- Stock HX35 that has gotten tired
- Tial 38mm MVS
- simple but quality Hallmann MBC
- I checked valve clearance last year and it was within tolerance bands
History: at one point in 2017 I was leaving a car show and hit the rev limiter, then immediately lost a cylinder and had to limp it into a parking lot on 3. The limiter is a 6850 rpm spark cut. I figured at the time that I had a spark issue. I wiggled wires and re-seated connectors. After some time sitting and a few attempts the car started up on all 4 and ran normal again so I went home. I went through externals, swapped coils just-in-case, and waited for it to present again. It did not that season.
October '18: I was driving the car home from work and noticed it was down on power. I did a few pulls and saw that I was spooling up to my set boost limit (~22psi) but then quickly bleeding off boost and leveling out around 15psi, which is pretty much my wastegate spring. AFR and everything else looked fine as this occurred, it would just spool up then bleed the boost off then hold solid at 15psi. It did sound off, like maybe it was getting choked off. I drove the car back and forth to work (30 miles) one more day with the condition staying consistent and taking logs/playing around. Things seemed status quo on the laptop. I could crank the boost controller all the way in and I still couldn't make more than 15psi of boost. I did a boost leak test from the compressor inlet to the tailpipe and it was tight as a drum.
Halloween: We had a really nice day so I took the car out again despite the boost issue. On the way home I decided to log a 3rd gear pull all the way out. The car settled into it's 15psi boost wall but this time I held it and kissed the limiter. I immediately lost a cylinder and limped into a parking lot. I of course remembered the last time and wiggled and unplugged but numerous restarts weren't getting the job done.
I got the car home and pushed air through it, the air was pouring right out of #1. So at this point I now realize I do not have an electrical issue, I have a mechanical failure and figured I might have burnt the exhaust valve. I spent the next day "working from home"; taking calls and emails while I pulled the head off
I was thrilled to find no piston damage and no evidence of contact
The exhaust valve was intact, not burnt as suspected. It was instead standing off the seat a few mm, hung open. OK explains things. Flipped it over and pulled the cam. Picture here is really just to show the bucket setup
Here's my smoking gun. As you can see from the witness marks on the tip of the valve, the lash cap had unseated itself and lodged between the valve and the bottom of the bucket, preventing the valve from fully closing.
The positive here is that there's really no DAMAGE. I could pop the lash cap back in place and it'd run. I am now under the assumption that in 2017 the same thing happened, except I had a (un)lucky break and the lash cap had probably just popped back into place and allowed me to continue on.
The problem is the question of WHY. In order for the lash cap to have dislodged I have to assume the valve was floating. Why was I floating the valve with this valve train at 6800rpm? Was it just #1 exhaust? I have not felt real signs of valve float generally when driving the car. I checked valve clearance before I pulled the cam and #3 had loosened up, others moved enough to need shimming but were not far out of spec. Of course #1 was jammed so didn't get a measurement there.
So here's the big question - can we correlate the boost issue and the valve train issue? I spoke with Josh and he did offer that a failed/ing turbo could create backpressure in the cylinder and effectively "overpower" the valve spring, creating the float situation.
I disassembled the Tial MVS gate and it looks fine, no obvious damage, diaphragm intact. No smoking gun there. I will reassemble it and do a pressure test.
I took apart the Holset. It was starting to blow some oil and feeling loose. Senior and I agreed that the turbo is in "needed to be rebuilt" condition. However, there was nothing screaming big failure. The notable finding was a cracked hotside between two scrolls, which shouldn't really matter. We also felt the pitted exhaust housing was pretty unacceptable from an airflow perspective. Maybe we're being overly scrutinizing aerospace guys there.. I do not see major signs of contact, but the vanes on the hot side are a bit rolled over, I can catch a nail on a rolled over lip.
My plans are..
For the head: my current plan is to bring the head to the machine shop that built my bottom end (
http://larryspower.com/). My goal is to get them thinking with me on the condition, and then to completely validate the setup. I would like them to get a real profile of the RSI cam, then go down the line and confirm basics like cam timing, spring pressure, spring height, pressure with valve weight considered etc. Honestly I'd be happy to lay the money out for the future peace of mind. I'm more concerned with them NOT finding anything than the cost..
for the turbo... this is where I think I might tip a domino over. I am disinclined to spend any time or money on the Holset. I had already been wanting for an upgrade and I'm of the mind to take this good excuse to jump for it. I would still like to prove out the Holset, but at this point I don't plan on putting it back in the car.
SO it looks like I'll be redoing the hot side here. I had to fix the wastegate tube anyways, so not a bad time to be tweaking the downpipe. I'll have to deal with water lines now, and probably redo some IC piping but hopefully it's not a massive ordeal. I have open ears on turbo suggestions. I am very excited to get something a little more modern and responsive. My goals are the most responsive 350whp street set up I can achieve. Tate says get the efr 7670 he has, I'm open to influence (Duder bad signal). God damn these things are expensive
. I wanted to put some cash aside to do a brake project, but looks like I'll prioritize this first (someday I would like to see the car have the modern turbo, a significant brake system upgrade, and then a 'final solution' ECU and wiring configuration).
So right now the car is stored and I've got expensive junk in the trunk
for additional reference this what the lash cap looks like:
interested to hear what some of you guys might think of it. I feel very lucky in that there was no bottom end damage, or damage to the head. I do need a much better standing of root cause though, so I can feel confident I'm taking the right corrective actions.
Nothing left to view, except those fool 7/9 Grandpa guys.... 
