Rover 200 BRM - 1.8 K-Series turbo project
Discussion
Thanks for the comments guys.
It's very frustrating but as they say when life gives you lemons, make lemonade. Giving up is not an option and I don't like the idea of slotting a Honda/Audi/etc unit in - that's not really in the spirit of this project.
I still think this engine has huge potential. And whilst replacing the pistons and liners will be expensive and cause a delay, the rest of the setup is in place and tested. So all I've got to do is rebuild the bottom end and slot the engine back in. The map should even be pretty close.
It's very frustrating but as they say when life gives you lemons, make lemonade. Giving up is not an option and I don't like the idea of slotting a Honda/Audi/etc unit in - that's not really in the spirit of this project.
I still think this engine has huge potential. And whilst replacing the pistons and liners will be expensive and cause a delay, the rest of the setup is in place and tested. So all I've got to do is rebuild the bottom end and slot the engine back in. The map should even be pretty close.
227bhp said:
Classic detonation, was the mapper not wearing det cans?
I wouldn't be going back to him again.
I'm not sure tbh.I wouldn't be going back to him again.
Unusual for the piston edge to bend inwards without showing signs of local det?
I wonder if it's a crown / liner clearance issue? As that's the bit of the crown which will get deformed under thermal stress. Neess pistons out for a closer look and a VERY good look at the bore too. Also are you 100% sure the valves have sufficient clearance to the piston?
Max_Torque said:
227bhp said:
Classic detonation, was the mapper not wearing det cans?
I wouldn't be going back to him again.
I'm not sure tbh.I wouldn't be going back to him again.
Unusual for the piston edge to bend inwards without showing signs of local det?
I wonder if it's a crown / liner clearance issue? As that's the bit of the crown which will get deformed under thermal stress. Neess pistons out for a closer look and a VERY good look at the bore too. Also are you 100% sure the valves have sufficient clearance to the piston?
One odd thing though and that is the piston actually collapsing on the exhaust side, presuming they've been put in the right way around (?) it's a bit strange, but could be down to the architecture of the combustion chamber.
Edit: Having looked at a pic there is some funky s
t going on with the combustion chamber, it looks like some kind of OEMs version of a 'Singh groove' on the inlet side which could account for the piston failure on the exhaust side.Edited by 227bhp on Sunday 17th April 23:59
K series pistons are pretty fragile at the ring land due to the really shallow crown height. I'd suggest this is either an overloaded piston or perhaps more likely ring flutter has set in and high-cycle fatigued the ring land off. Was it being run at high speeds and relatively light loads at all...?
The inwards bend is more likely to be a pre-build handling damage problem.
The inwards bend is more likely to be a pre-build handling damage problem.
AER said:
K series pistons are pretty fragile at the ring land due to the really shallow crown height. I'd suggest this is either an overloaded piston or perhaps more likely ring flutter has set in and high-cycle fatigued the ring land off. Was it being run at high speeds and relatively light loads at all...?
The inwards bend is more likely to be a pre-build handling damage problem.
On a specially designed forged piston with the ring pack lowered?The inwards bend is more likely to be a pre-build handling damage problem.
He's managed to drop all four of them in the same place, bend them, not notice and assemble it as is?
Stuballs said:
I found I had to add more fuel to the map.
actually, it also turned out that my fuel pump had been dying. I upgraded to an in-tank Walbro 255 and that threw everything completely out. Anyway, once the chaps got everything running correctly again we started to engage the electronic boost controller through the Emerald in open loop.
Whilst the other pistons appeared ok, closer inspection reveals that this is happening to all of them.
given the other pistons haven't gone this way, and cyl 1 runs coolest of all, there's obviously something else going on.
Can you confirm those salient points? They seem a bit contradictory.actually, it also turned out that my fuel pump had been dying. I upgraded to an in-tank Walbro 255 and that threw everything completely out. Anyway, once the chaps got everything running correctly again we started to engage the electronic boost controller through the Emerald in open loop.
Whilst the other pistons appeared ok, closer inspection reveals that this is happening to all of them.
given the other pistons haven't gone this way, and cyl 1 runs coolest of all, there's obviously something else going on.
Who mapped the car, him or you?
What did or didn't happen to all of the pistons?
When your fuel pump started to fail that is possibly when the rot set in, the early damage was done which then completely failed under duress later.
Thanks for the suggestions guys. This gives me a few ideas.
I think the bending in may be well details and I'll know when I get the pistons out. I now know of another engine running these pistons that has had det problems with them. It is probably because the thin bit runs way too hot. K-series pistons don't have oil squirters so piston temperature is critical. This is why I'll have ceramic coating on the new Areas I use.
It defintely wasn't a piston/liner clearance issue. If anything there was too much clearance. That said, there is scoring damage to that liner. Maybe an issue with the rings.
Singh groove? Interesting. I'm not sure what the purpose of that cutout is but it seems too shallow have any effect on flow.
I think the bending in may be well details and I'll know when I get the pistons out. I now know of another engine running these pistons that has had det problems with them. It is probably because the thin bit runs way too hot. K-series pistons don't have oil squirters so piston temperature is critical. This is why I'll have ceramic coating on the new Areas I use.
It defintely wasn't a piston/liner clearance issue. If anything there was too much clearance. That said, there is scoring damage to that liner. Maybe an issue with the rings.
Singh groove? Interesting. I'm not sure what the purpose of that cutout is but it seems too shallow have any effect on flow.
227bhp said:
Can you confirm those salient points? They seem a bit contradictory.
Who mapped the car, him or you?
What did or didn't happen to all of the pistons?
When your fuel pump started to fail that is possibly when the rot set in, the early damage was done which then completely failed under duress later.
I added the fuel after it was mapped. It went lean at partial throttle i.e. Not when under load and it got worse the more miles I put in the car. Under load it was fine. Maybe fuel pump was Ok and that issue was just everything bedding in. Or maybe there is an underlying issue with the fuel system (what I suspect). I'm going to revisit that while I wait for the pistons which will include a flow test on my injectors. Actually, I'm trying to think of a way to test my complete fuel system on the car. Probably not possible but would be nice to know that with my pump, fuel rail, fpr and injectors, every injector flows the same. You may be right that the damage was done early on and the mapping with a bit more boost finished it off. Who mapped the car, him or you?
What did or didn't happen to all of the pistons?
When your fuel pump started to fail that is possibly when the rot set in, the early damage was done which then completely failed under duress later.
The bending in at the valve cutout has happened to every piston to varying degrees. It's barely noticeable but it is there. It's more on the inlet side on cyl 2-4. Which is odd because obviously it's the exhaust side on cyl 1 that let go. This further suggests to me that there's something else going on.
I'll hopefully get the engine out and stripped over the next couple of days so I'll know more.
227bhp said:
AER said:
K series pistons are pretty fragile at the ring land due to the really shallow crown height. I'd suggest this is either an overloaded piston or perhaps more likely ring flutter has set in and high-cycle fatigued the ring land off. Was it being run at high speeds and relatively light loads at all...?
The inwards bend is more likely to be a pre-build handling damage problem.
On a specially designed forged piston with the ring pack lowered?The inwards bend is more likely to be a pre-build handling damage problem.
He's managed to drop all four of them in the same place, bend them, not notice and assemble it as is?
AER said:
227bhp said:
AER said:
K series pistons are pretty fragile at the ring land due to the really shallow crown height. I'd suggest this is either an overloaded piston or perhaps more likely ring flutter has set in and high-cycle fatigued the ring land off. Was it being run at high speeds and relatively light loads at all...?
The inwards bend is more likely to be a pre-build handling damage problem.
On a specially designed forged piston with the ring pack lowered?The inwards bend is more likely to be a pre-build handling damage problem.
He's managed to drop all four of them in the same place, bend them, not notice and assemble it as is?
The pistons have accumulator grooves machined in also which prevents ring flutter.
Piston manufacturers aren't daft, they know how to design a piston. It's what comes after where the failure occurs and people will always wrongly point at a component for an explanation.
How many times have I heard "I'm not using those piston again, they're crap!" because they broke or melted, then the next build gets a different make, but other things get done better too, so it must have been them of course.
That was det damage 100% and only the OP has the hard facts on how it happened and he isn't saying much.
An experienced engine builder would have known to file those thin ears down to keep them out of the way, but the OP wasn't to know that and regardless of which a chunk would have been shocked out of the other side of the piston anyhow.
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