Mis-aligned Rings

[david-b]

Couple weeks ago I was on the expressway with the boost turned up and it ended up dying when I popped it to neutral. Car would start no problem and idle, but when I revved it would be fine, but then die when the rpms dropped down. Compression test came up low compression in the middle 2 cylinders. I did not do a compression test prior to the problem.

Pulled the out and seen that my rings were not aligned to where they should have been. On the middle 2, couple of the rings were on the same side like this

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I built this motor myself, so I obviously made a mistake somewhere.

I've got the pistons pulled, have new rings and going to installed them and make sure the gaps are where they should be. Cylinder walls are perfect (will re-hone) and everything is looking great. Head was checked for flatness as well and came back perfect.

My question is, the car idled and ran fine with up to ~7psi with the rings like that. I was tuning up to about 12psi at the time and was pretty constant with the boost (on expressway). Why would it cause idling problems AFTER that, and not before? Is there something else I should look for?

 

[2qik4u]

what did you change in your tuning just before it happened???? think of the last thing you changed. that might have something to do with it. your rings sometimes move and spin around your pistons so i dont think that has anything to do with anything except maybe low compression if you did a compression check when your engine was cold. did you do a compression test when your engine was at full operating temp????? this makes a big difference!! when old your pistons arent expanded andzou will get lower compression readings. especially when you have aftermarket forged pistons!!!

 

[david-b]

All I was doing at the time was logging via MegaSquirt. No changes were made. Literally put about 20 miles on the car earlier that morning with normal driving. No problems there at all. Car ran great.

It was cold when I did the test. I understand that will cause a lower reading. It was something like 195-140-155-185 IIRC. The middle two still should not have been that low.

EDIT: Oh and I went over all of MS settings, reflashed the ECU and restored my previous settings, and still was doing the same thing.

 

[siccboostsi]

be sure that the rings are for your bore, maybe you can try file to fit rings. just be sure everything is machine surface. also be sure you turn the wrings opposite of each other. i have seen some builders move the rings just out of alignment like you show on the pic.

 

[brian9397gsx]

the ring gaps should be staggered you should never have your ring gaps lined up.

i re read your first post sounds like you did have them staggered to begin with. thats strange that they would end up aligning themselves like that. are you using a feeler guage when your filing them? also how tight are your gaps

 

[BogusSVO]

the rings move so its not uncommon to find them like that.. another 2miles and the gaps would be some where else.

sice you have the engine down... fluid test the valves to make sure you have proper seat og the valve...

 

[david-b]

It may have been my error when putting them in. Maybe when I was putting them in the ring compressor they may have gotten moved around there. I don't know. I was fine to the best of my knowledge when I gapped/installed the rings though.

I heard the rings are not supposed to move. They're going up and down, not any other direction. Original rings on original pistons (120,000 miles) were in the right place when I took them out.

I honestly don't remember what they were gapped to off hand. I'm 99% sure that the gapping was correct. That was the easy part. Feeler gauge was used in the process, edges filed good, gaps closed totally flat with one another.

Rings are correct bore size.

I will fluid check the valves tonight. I'm pretty sure my machinist would have checked them out as well, but double checking never hurts. Head was machined ~15,000 miles ago including a 3-angle valve job. All new hardware. No problems ever with it (yet)

 

[haswesley]

Sometimes the middle of the block can sag between cylinders 2 and 3. Did you have the block resurfaced? I had to have mine resurfaced. Its also nice to find someone else running MegaSquirt. I don't think many DSMers run MegaSquirt.

 

[david-b]

Block was resurfaced and machine mid last year. Never heard of a block sagging. Straight looks good when I did it the other day.

Many 420a owners run MS. Doesn't seem like too many people on here run it, but other forums have a pretty large following for us.

I guess I'll just re-ring it and see what happens after it's all back together. Everything seems to be good except where the rings were sitting and I know they're not supposed to move. We'll see what happens. Hopefully can get all back together this weekend. I'll get back with progress.

 

[2GRick]

Block was resurfaced and machine mid last year. Never heard of a block sagging. Straight looks good when I did it the other day.

Many 420a owners run MS. Doesn't seem like too many people on here run it, but other forums have a pretty large following for us.

I guess I'll just re-ring it and see what happens after it's all back together. Everything seems to be good except where the rings were sitting and I know they're not supposed to move. We'll see what happens. Hopefully can get all back together this weekend. I'll get back with progress.

I could be wrong but the ring gap looks awfully big, and also rings will move around. Did u check the gap size?

 

[david-b]

I could be wrong but the ring gap looks awfully big, and also rings will move around. Did u check the gap size?

I honestly don't remember what they were gapped to off hand. I'm 99% sure that the gapping was correct. That was the easy part. Feeler gauge was used in the process, edges filed good, gaps closed totally flat with one another.

Rings are correct bore size.

Rings only had 270 miles on them, so not really 'squeezed' much

 

[david-b]

Took all the rings off the pistons this weekend and the oil rings were even in the wrong spots. Was def my fault. Rings don't move like that. Put new rings on and triple checked it all and honed out the cylinders. It's about 80% back together, just have to do the timing and exhaust mani/turbo. 100% confident that it will be perfect this time around.