Is this detonation damage?
Discussion
The geometry is the result of a stretched base engine who's footprint was already compact. Increasing the stroke has lead to the compromises in rod length and angle, under counterweighted crank and under engineered pistons. The bore increase has lead to the relatively poorly located and fragile liners.
Dave
Dave
My take is that for whatever reason there was massive cylinder pressure in that cylinder which may have been the cause of the det or resulted from the det. I would look for a fault that effected the ignition or fueling on that cylinder before I blamed the mapper. Otherwise the fault may happen again, assuming there is one.
Boosted LS1 said:
My take is that for whatever reason there was massive cylinder pressure in that cylinder which may have been the cause of the det or resulted from the det. I would look for a fault that effected the ignition or fueling on that cylinder before I blamed the mapper. Otherwise the fault may happen again, assuming there is one.
In the other thread the OP mentions fuel pump failure IIRC and also the mapper not listening for det.This engine story reminds me of a Mexican standoff, sadly not a rare occurence. If at all possible put all your eggs in one basket, if one gets broken you know where to point the finger.
Would have to agree with the last point.
Having multiple parties involved in builds can easily turn into a nightmare if there is a problem....and without detailed info, logs, whatever harder to argue one way or another who may be at fault.
Havent read the other thread, too many pages to be bothered. If there is any relevant info in it, it should be posted here.
But yes those pistons do look like a very bad design with such huge cutouts, that's for sure. You would think though if running correctly, ring gaps not too tight etc then a failure where the top almost gets ripped off the piston, still shouldnt happen.
Having multiple parties involved in builds can easily turn into a nightmare if there is a problem....and without detailed info, logs, whatever harder to argue one way or another who may be at fault.
Havent read the other thread, too many pages to be bothered. If there is any relevant info in it, it should be posted here.
But yes those pistons do look like a very bad design with such huge cutouts, that's for sure. You would think though if running correctly, ring gaps not too tight etc then a failure where the top almost gets ripped off the piston, still shouldnt happen.
stevieturbo said:
It almost looks like the valve cutout is cut right through to the top ring land ! Or very very very close to it.
And what were ring gaps like ?
Bang on with the excessive valve cutouts slicing almost into the top ring groove - several people have said the same thing including Scholar Engines. And what were ring gaps like ?
Ring gaps were at the wider end of what wossner recommended. I always worried I'd made them too wide as I had a fair bit of blow-by (breathed a lot of vapor though the catch can under boost). That said, cyl 1 had a lot of scoring. Maybe my feeler gauges are wrong?!
Boosted LS1 said:
OP, have you any pictures of the plugs, earth electrode?
Only picture I have is the smashed in one from cyl 1 which doesn't show much. 
FordPrefect56 said:
It's very simple. If the cylinder head has det marks on the other three chambers where the piston didn't blow up then it's bad mapping that caused the det. If only the chamber where the piston blew up has det marks then the piston probably broke first from the valve cutouts failing.
All 4 cylinders have the same det marks. Not any worse on any one in particular. FordPrefect56 said:
It's what you don't know you don't know
Love that! Exactly the problem I've had coming at this as a novice. It's how you learn I suppose. But it's been an expensive lesson! Evoluzione said:
Creating a squish clearance as excessive as that ^^ would only make make the engine even more prone to det and that's on top of the fact that these newer items have lost the squish pads the old ones had.
And this is another piece of the puzzle - something I didn't know I didn't know. I used standard length nasp rods but used an n-series gasket which has 5 layers and compresses to 2mm. I did this partially to help lower compression. But in doing so I probably compromised the squish. Evoluzione said:
In the other thread the OP mentions fuel pump failure IIRC and also the mapper not listening for det.
Yes I still think the walbro in tank pump was part of the problem. Thanks everyone for taking the time to comment. It's been really helpful.
My belief is that this was a combination of one or more factors causing det (weak fuel system, bad squish, reversion from short exhaust runners, ring gap/clearance issue) and the fragile pistons dying at the first sign of a problem.
OP, can you post up pics of the other plugs? A pic showing a close up of the earth electrode from a side view, any side will do. Another pic looking down into the plug, preferably under decent lighting. It's the porcelain I want to see, deep down if possible.
ETA, have you a pic of the damaged plug, looking down on it?
ETA, have you a pic of the damaged plug, looking down on it?
So what were the ring gaps ?
And no, lots of blowby will not be because of ring gaps...I doubt anyone could make them that big. But poor bore prep and ring sealing would cause a lot of blowby
In what way did the fuel pump fail ? Walbros are usually very reliable and I doubt most K-series would ever trouble the typical in tank Walbro pump in terms of fuel supply ability.
Was fueling not being monitored ? fuel pressure ?
People rant about squish and other stuff, ffs years ago I just chopped the tops of pistons for a free turbo build and never had an issue. I've ran some 6-7mm down the bore !
If those huge valve cutouts really are needed, I'd sooner move the ring pack down the bore and run a piston with a more solid top than those pistons, even if it meant less of any shape to the crown.
As for reversion from short exhaust runners ??? WTF
And no, lots of blowby will not be because of ring gaps...I doubt anyone could make them that big. But poor bore prep and ring sealing would cause a lot of blowby
In what way did the fuel pump fail ? Walbros are usually very reliable and I doubt most K-series would ever trouble the typical in tank Walbro pump in terms of fuel supply ability.
Was fueling not being monitored ? fuel pressure ?
People rant about squish and other stuff, ffs years ago I just chopped the tops of pistons for a free turbo build and never had an issue. I've ran some 6-7mm down the bore !
If those huge valve cutouts really are needed, I'd sooner move the ring pack down the bore and run a piston with a more solid top than those pistons, even if it meant less of any shape to the crown.
As for reversion from short exhaust runners ??? WTF
Boosted LS1 said:
OP, can you post up pics of the other plugs? A pic showing a close up of the earth electrode from a side view, any side will do. Another pic looking down into the plug, preferably under decent lighting. It's the porcelain I want to see, deep down if possible.
ETA, have you a pic of the damaged plug, looking down on it?
Couldn't really get side-on pic as the insulator is recessed ETA, have you a pic of the damaged plug, looking down on it?
Plug from failed cylinder:
Cylinder 2:
stevieturbo said:
So what were the ring gaps ?
And no, lots of blowby will not be because of ring gaps...I doubt anyone could make them that big. But poor bore prep and ring sealing would cause a lot of blowby.
In what way did the fuel pump fail ? Walbros are usually very reliable and I doubt most K-series would ever trouble the typical in tank Walbro pump in terms of fuel supply ability.
Was fueling not being monitored ? fuel pressure ?
People rant about squish and other stuff, ffs years ago I just chopped the tops of pistons for a free turbo build and never had an issue. I've ran some 6-7mm down the bore !
If those huge valve cutouts really are needed, I'd sooner move the ring pack down the bore and run a piston with a more solid top than those pistons, even if it meant less of any shape to the crown.
As for reversion from short exhaust runners ??? WTF
Ring gaps 19 thou top. 17 thou middle.And no, lots of blowby will not be because of ring gaps...I doubt anyone could make them that big. But poor bore prep and ring sealing would cause a lot of blowby.
In what way did the fuel pump fail ? Walbros are usually very reliable and I doubt most K-series would ever trouble the typical in tank Walbro pump in terms of fuel supply ability.
Was fueling not being monitored ? fuel pressure ?
People rant about squish and other stuff, ffs years ago I just chopped the tops of pistons for a free turbo build and never had an issue. I've ran some 6-7mm down the bore !
If those huge valve cutouts really are needed, I'd sooner move the ring pack down the bore and run a piston with a more solid top than those pistons, even if it meant less of any shape to the crown.
As for reversion from short exhaust runners ??? WTF
Liners are from wossner. Ductile iron. I didn't do anything with them by way of prep.
Fuel pressure was being monitored. I can't put my finger on a particular issue otherwise I found happily say "yes it was the fuel". But it was not a straight swap for the standard pump and required fettling to get it to fit. Although it did eventually for and pesticide fuel. But the resultant fuel flow had a pulse to it that the stock pump didn't have. After the pump upgrade the fuel pressure had a slight flutter to it at idle, which the mapper said was normal.
Yikes. That plug in No 2 was getting hot. Not a trace of deposits on the insulator. Excessive ignition timing and det city. Same old story I'm afraid with turbo engines. Mappers never give them enough boost retard on the ignition timing to start with and then build it up carefully from there. For reasons that are beyond me they invariably start with too much advance and knock a bit off if it dets. But you can't always hear that before the engine goes pop. We've seen so many threads on here where a meticulous turbo engine build goes pop on the dyno and there's only ever one reason. Too much advance. End of.
The pistons were crap but they only failed because of det like I said in the first place.
The pistons were crap but they only failed because of det like I said in the first place.
Evoluzione said:
Are you still using these sound engineering principles today?
I bet you aren't.
If I was building on a zero budget like back then...I would be ! It may not sound nice but it worked and the pistons never broke ( I did melt a few though, but that was not a fault of the piston...turbo tuning wasnt as easy before lambda sensors, fuel injection and the like. )I bet you aren't.
IMO people often fixate on silly things..and ignore important things.
ie design pistons to meet some bizarre squish goal, but make them weak as f
k so they'll break at the first sign of a problem lol. I've no idea on K-series etc...but these liners come fully prepped to just drop in and work with new pistons and rings ? No honing required or anything like that ?
stevieturbo said:
I've no idea on K-series etc...but these liners come fully prepped to just drop in and work with new pistons and rings ? No honing required or anything like that ?
They drop in with a bead of hylomar around the seat. They are held in place by the head (if you even then the crank with the head removed the liner can unseat. They come pre-honed, ready to go. That said, the guy at Scholar who looked at the pistons said he doesn't like the drop fit liners as they move and distort with heat. Theirs are pressed into the block after its been heated. So hopefully I never need to get them out!
Liners that just sit on a seat are not a problem. Think Peugeot XU engine. Sure they distort a bit under load because they're just held at top and bottom but it makes not a scrap of difference to power or ring sealing. I've seen them come out at about 4 thou oval but if you leave them on a shelf for a while the stresses come back out and they go round again.
FordPrefect56 said:
Yikes. That plug in No 2 was getting hot. Not a trace of deposits on the insulator. Excessive ignition timing and det city. Same old story I'm afraid with turbo engines. Mappers never give them enough boost retard on the ignition timing to start with and then build it up carefully from there. For reasons that are beyond me they invariably start with too much advance and knock a bit off if it dets. But you can't always hear that before the engine goes pop. We've seen so many threads on here where a meticulous turbo engine build goes pop on the dyno and there's only ever one reason. Too much advance. End of.
How so? We can't see the fueling ring from that pic or the heat temp from the plug electrode. The plug shows no signs of detonation deposits. You are making assumptions imo. I want to see more information.Boosted LS1 said:
How so? We can't see the fueling ring from that pic or the heat temp from the plug electrode. The plug shows no signs of detonation deposits. You are making assumptions imo. I want to see more information.
Assumptions? Moi? I don't think I've ever done that, at least I assume not. I'm not sure why you want to see deep inside the insulator or what you mean by "fueling ring". The base ring of the plug (bit the earth electrode is welded to) has a decent colour, bit of fluffy black which is not unusual from a rich fueled turbo engine. Porcelain is bone white, bleached, I'd expect a little colour on there by now although unleaded petrol behaves differently from how leaded used to in terms of plug colour. There seem to be a couple of splashes of aluminium from the det.Edited by FordPrefect56 on Monday 13th June 08:07
You should see a circle called the fueling ring at the base of the insulator. Usually you need a bright light to see right down inside and a magnifier. The colour of that ring indicates if the fuelling is correct or not. The earth electrode gets hot and should have an anealling band on it. the position of the band indicates if the plug is to hot or cold etc.
I can't see what I'm looking for in the picture.
ETA, there may be some colour inside that plug or it could be shadow. Hard to see it properly.
See here:
http://www.crankshaftcoalition.com/wiki/images/6/6...
http://www.wallaceracing.com/Spark_Plug_Readings_C...
I can't see what I'm looking for in the picture.
ETA, there may be some colour inside that plug or it could be shadow. Hard to see it properly.
Edited by Boosted LS1 on Monday 13th June 09:18
See here:
http://www.crankshaftcoalition.com/wiki/images/6/6...
http://www.wallaceracing.com/Spark_Plug_Readings_C...
Edited by Boosted LS1 on Monday 13th June 09:28
I think there's a rather large amount of hooey (is that a word?) talked about reading spark plugs. Mainly from the States of course. Unless the engine has been cut right at full throttle, high rpm you'll never read the WOT fueling because the plug colour will change at idle or cruise. On an engine running as rich as this (per the OP) as most turbos are set up for to generate a bit of chamber cooling I'd expect some colour on the insulator.
Anyway it's a pretty safe bet what went wrong without seeing the plugs or anything else. 99% of engines that go pop on the rollers are because there's too much ignition advance. Maybe the OP can post his ignition maps including most importantly the boost retard values.
Anyway it's a pretty safe bet what went wrong without seeing the plugs or anything else. 99% of engines that go pop on the rollers are because there's too much ignition advance. Maybe the OP can post his ignition maps including most importantly the boost retard values.
I don't see any det/knock damage in any of the photos posted so far. Only thing I can see is casting porosity on the head face for which the K-series is infamous.
edit to add: if this was det/knock damage, the edge of the squish feature shown here would have been eroded away. As it is, it looks pretty much like it was post head skimming.
edit to add: if this was det/knock damage, the edge of the squish feature shown here would have been eroded away. As it is, it looks pretty much like it was post head skimming.
Edited by AER on Saturday 18th June 08:14
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