[Brotatochip]

Thanks @Bjorn, appreciate the response.

My only other experience with a turbo car was a friends WRX. He had a larger turbo and a tune. Suffered a similar fate while on track. Still ran but very poorly and smoked a lot. I tore it apart and replaced the block with a build one. I found broken ring lands on all four pistons as well as a piston skirt that had separated. I was thinking ring lands were my issue as well due to the similarities.

The tuner was recommended to me by multiple people claiming they were the best with Honda stuff, but was about $200 cheaper than larger shops. It seemed too good to be true. I had issues with the tune immediately with light throttle input at low RPM being very jerky as well as Ltrim at -17% when cruising at highway speeds (this was supposed to be fixed soon).

My next question is where should I go from here? Not really looking to make more power and would plan on doing more of the same (track days and autocross).
-Find another used, stock K24a2 block and get a better tune. Or maybe rebuild mine with stock parts.
-Rebuild this block with better components. Specifically, lower CR pistons. I always fear having issues with aftermarket internals though.

 

[Brotatochip]

Really appreciate the replies! Below is a Google Drive link that should contain the cal and a log from a few days prior. I was attempting to measure 0-60 time, the log is only ~90 seconds long. Unfortunately, I was not logging while on the track.

Shared - Google Drive

The rings were replaced around 1.5 years ago now. I measured all the end gaps but do not remember what they were exactly. I know they were outside the "New" spec (0.2-0.35 mm for the top ring) but were well within the service limit spec (0.6 mm). Possibly around 0.4-0.45 mm. I can't be the only one taking a basically stock K24 turbo to the track so I figured those specs would suffice.

Another thing to note, I refueled after the second session. This included a 30 mile drive to the track and roughly 45 minutes of on track time. My car took 7.4 gallons while my brother's supercharged K24z7 took over 10 gallons. His makes 12 more hp but mine makes 25 more lb ft. I would think fuel consumption would be roughly the same. So, not enough fuel on the track led to excessive cylinder wall temps, which led to detonation/knock, which led to ring land failure. Possibly?

 

[Brotatochip]

IMHO a must have for DIY forced induction engines on track.

Admittedly, I should have been monitoring AFR. At the same time, I paid someone to tune it so I could drive worry-free but that was not the case.

But I would never go to track with it.

Too late now!

Your wastegate duty cycle aim should be around 60 % ideally when running for constant boost over engine speed. Maybe you can use a lower spring rate?!

It currently has a 5 pound wastegate spring in a 44mm Tial. It has a 1320 sidewinder T3 turbo manifold (see below). The turbo is a 0.82 A/R, it was also offered in 0.63 and 1.06.

Any leakdown/compression test results already available ? I am sooooo curious 😇!

No, I do not. Honestly, I have almost no motivation to work on the car. At this point, I don't think I'll be able to get it fixed before it begins getting cold. Likely, I won't be able to do any more racing which makes me not want to even look at it.

 

[Brotatochip]

I clearly didn't do enough research. I knew the manifold runners were not equal length but thought this would only lower max power a little. I had no idea the back pressure causing such an issue. Looks like I need to get a different turbo manifold. Turbo is not ideal but biggest issue is manifold? I would prefer not to have to replace the turbo.

What were you looking at to determine back pressure?

 

[Brotatochip]

I was not able to find my compression tester and have not tried my leak down tester. I've still been working my way through the stages of grief so I've had no motivation to work on the car I think I've finally gotten to the acceptance stage and was planning on working on it some tonight.

I plan on pulling the engine without running any tests. Something is definitely wrong with cylinder 2, likely a ring land. Engine will get torn down to investigate/rebuild anyways. All I've done so far is get it up on jack stands, drain coolant and A/C, remove splash panels, remove air intake, and begin disconnecting hoses.

Part of me wants to buy a used K24a2 and install just to get the car running quickly. It would be using the same tune but wouldn't be tracked again this year. Over the winter I could then rebuild this engine and get another tune. Also thought about keeping the K24a2, getting an improved manifold/turbo, then a proper tune so I don't have to rebuild a block. I just haven't decided how much I want to spend on this unplanned engine rebuild/replacement.

 

[Brotatochip]

😄. On which stage of grief according the Kübler-Ross-model are you actually?

I would say I'm in the acceptance stage, likely in the experiment section

Recognition based on assumption or a leak down test?

Based on the fact the cylinder 2 spark plug and piston (from what I can see through the tube) are coated in oil. It was also drastically down on power compared to NA form telling me there is certainly low compression somewhere.

Would my favorite way to go .

This is the way I've been leaning, mostly because I could get it up and running much quicker. Initially only costing me the price of a K24a2 with the manifold and turbo coming later. At the same time I worry about having the same issue at a track day next year.

 

[Brotatochip]

Engine (and trans) have been out for nearly two weeks now. Finally had some time the last two days to tear into it. First thing I found, one of the turbo to manifold nuts was completely missing. The remaining three were hardly any more than hand tight. I'm sure I had those tight before the car ever started, clearly they came loose at some point in the engines <2k miles of turbo life. Anyways, pulled the head to find much less damage than I imagined.

Vertical scraping on the cylinder wall and damage near the top (detonation?).

No chuck of ringland missing, but the piston to wall gap seems very large on the intake side. Same side as the scraping.

With piston at TDC. You can see the piston does not look perfectly circular on this side anymore.

One final picture of piston 3. You can tell the difference of a good vs bad piston.

I cannot really feel the vertical scrapes on the cylinder wall but I can definitely feel the marks at the top. The piston doesn't look like it's broken but it's definitely missing some material. Have not pulled the pan/pump yet but hoping to get to that this weekend.

 

[Brotatochip]

I was expecting to find a chunk out of the top. I've only ever seen ringland damage once before on that WRX engine and it was the very top that broke. We'll see if a piece in the middle is broken when I pull the piston, hopefully this weekend.

 

[Brotatochip]

@Lotus thank you for the info. I cannot see the third picture in your post, the first two show up just fine. This isn't the first time I've noticed missing pictures. Not sure if something is wrong with my laptop.

Two for two on ring ends touching eventually causing failure. So, poor turbo manifold caused high exhaust back pressure, which caused extra heat into the cylinder walls while on track, which caused the rings to expand more than they would ever see on the dyno or street, leading to what will likely be a broken ringland between the top rings.

If I were to get another K24a2 or K24a and swap all the turbo stuff onto I would need to open it up first to increase ring gaps. That is assuming a turbo manifold with equal length runners would still require wider ring gaps even with the improvements it would provide.