Hey guys,
So the ghetto restrictor fitting that the previous owner had between the wastegate and compressor blew off on track yesterday and I detonated a few times due to completely uncontrolled boost.

At first i had no idea what it was so I tried it 2 times more after the first time that something felt wrong. I didn't see that the fitting was blown off, but I just found it so I'm 99% sure that it was boosting some ridiculous pressure resulting in detonation.

I'd say it detonated right after the fitting blew off, another time shortly after when I tried to boost again, and probably a 3rd time. Couldn't figure out what was happening so I stayed out of boost the rest of the day and for the whole drive home.

A few minutes ago I hooked up a proper boost control solenoid and set the boost target to 100kpa so it's basically running wastegate boost. I went out and did a datalog and it's boosting like it was before again.

What do I need to check to figure out if I did any damage to the engine? I can't feel anything obviously wrong with it at the moment. Thanks!

 

Do a leakdown and compression test. Also a boroscope could be useful.

How severe (loud) was the detonation? Was it accompanied with a loss of power?

 

I didn't really hear much but that might be because of all the other noises around me. If I remember, it felt like power was cutting in and out. But each time I let off immediately when it started. Not sure if that helps though.

 

I was reading about the link ecu, and it's possible I could have hit the map limit and got a fuel cut. Looks like my map limit was set at 220kpa.

 

I suspect you're probably right. The timing map should be extremely conservative in the "out of bounds" zone, and an overboost cutoff of 220kPa sounds reasonable.

The motor is probably just fine.

 

Set your map limit to something substantially lower, say 110kpa, then go for a drive. If you get the same feeling when hitting that pressure, then as Joe says, your motor is fine.

 

I set it at 100kpa and ran it off of wastegate boost basically. The car pulls fine and boosts to 150kpa (8psi wastegate spring pressure) and holds. So that seems fine. It seems to idle fine. It might be that I'm being super paranoid but it seems like there's more vibration at idle? Maybe not. I don't know if that would be a symptom or not.

There wasn't any oil being consumed on my 200 mile drive home and no apparent coolant leaks yet.

I guess I'll take it in for a leakdown test just in case. SIGH...

What usually breaks if you detonate?

Oh and in case it matters, the engine is a GT-X bottom with 99 head. So it has the 8.2:1 compression ratio I think.

 

Things that break:
Bent rods
Broken piston crowns / Holes in your pistons
Shattered piston rings
Blown out headgasket
Destroyed rod bearings
'Pockmarks' on your piston and or combustion chamber surface


Not in any particular order

 

Easiest way to at least check for something is to pull your sparkplugs and look for bits of metal on them.

 

Leakdown test tomorrow. I will keep you guys posted. Fingers crossed!

 

Compression and leakdown, as well as inspect plugs for pitting or damage. If you hit boost cut then you should not have hurt anything. Its why its there

 

You can't "feel detonation", you can only hear it. Well, some of us can feel it but only if the car is driven frequently and we feel the loss in power.

Overboost protection will save you thousands, it did when I had the earlier turbo parts.

 

Boroscope is total overkill. Run a compression test if you must and be done. In general, if you don't have a hole in the block you're probably ok. For now.



For light det, you can't reallly feel it. Actually, usually the car is feeling pretty fast when you have light det. For big heavy det though, yes you can feel it. It feels like misfires and even if you can't hear pinging noises the engine won't be running smoothly.

Overboost protection AND closed loop knock detection/trim will save you thousands.

 

Alright I have numbers to report back from the shop! They're ordered from #1-#4.

Compression numbers: (for reference this is GT-X pistons, I think 8.2:1??)
162, 160, 160, 160

Leakdown numbers:
5%, 17%, 16%, 7%

He said for #2 and 3 the air was leaking out of exhaust valves probably. He said probably don't need to do anything with them for now.

What do you guys think?

 

I think those are some of the most uniform compression numbers I have ever seen. Turn up the boost.

 

I remember hitting MAP limit with my Link... It sounded exactly as described.

 

Burnt/leaking valves won't make your motor blow. I've seen quite a few motors with burnt valves that still made power and were ok. Run that shi and don't look back.


Best advice ever.

 

Okay then. With you guys' blessings I'll get a new downpipe, patch up my exhaust, and turn up the boost!!