Would like to compile some info on why engines have failed.

Preferable 20vt engines under tune.

What power was it running? What let go? Why did it let go?

Ross

you probably already know mine

There was a thread like this a while ago - think it was started by Bockers

I dont know the final reason. I remember u said 3 pistons were down on compression. What was the final diagnosis?

Ross

Oo oo. That would be good.

Ross

the pistons cracked around the ringlands, think it was down to too much heat, thats what Accralite said anyway!

are you getting worried already Ross

Well.... Im just wondering.

Supposedly running a turbo outside its efficiency creates LOTS of heat. So technically running a bigger turbo within its efficiencies is gonna produce less heat and hence more power for safer.

But i know that the engine might still let go.

If it does, its off the road and forged. But just wanna see what else i need to watch for.

Ross

If your worried about that then check your inlet temps, if your cooler is good enough it will bring them down enough for the engine to be happy.

What should i hope for them to be at?

I have fitted Aquamist to combat the heat aswell. As far as i know this will buy me some needed safety.

Ross

Did you break down the other day? Somebody said they seen a yellow coupe at the side of the road which was stripped out inside.

Unless you look at the EGTs it will tell you nothing, inlet temp can be super but the engine is pinking and the exhaust gas temps are at 980C or whatever.

You know the std problems
350-360BHP - pistons are starting to get marginal, ring lands are brittle and will break. Ring land damage may have started 5 years ago and compression might be fine but they will go eventually unless your car has never pinked or somehow yours are stronger than everyone elses
350lbs/ft - rods are extremely marginal and over time will probably bend like I saw, like Nigel saw on std rods.
@Ross -
No amount of banter on here about anyone running 380BHP on std pistons and rods will make any difference; with your mods you are pushing your luck with an RSR at full pelt and something will go, just a question of when.
There are plenty of cases of blocks or cylinder heads getting damaged when engines go so don't try it. Run 350BHP absolute max and no more than 340lbs/ft torque unless you fit forged internals.

I totally agree with John. My car was running 350bhp with standard internals. When Eldhino's engine went, I realised that I then had the most powerfull coupe with standard internals, so I had it all checked.

Guess what I found? The ringlands had gone on one of the pistons. So, I bought forged internals and had the engine rebuilt. I was running with a pro alloy intercooler and Aquamist with 50/50 water methanol, and my inlet temps were good.

I had been running with that power for little over a year, but had only done 8k miles. So, anyone running over 300bhp should start saving for forged internals, because IMO it WILL go bang eventually.

Well i've been running over 300bhp for 15k miles. 310-320 for the first 8-9k and 330bhp+ since then.

But what turbo were u running squid?

Ross

GT28RS - 325bhp at the wheels, which is over 350bhp at the fly on most dynos and 320lbs of torque.

What boost were u running?

Ross

Here it is. Probably needs expanding a little concerning tolerances of standard internals etc...

Agreed. Maybe an idea for JohnS to add a section?


Ross

hello squid you told me you had done under 3k on the turbo that i bought off of you well if not that will explain why

my seals are going already and mine as only just been mapped 4 weeks ago

There has been an open discussion about stock pistons vs. forged pistons on a Danish tuning forum, but the conclussion was that stock pistons from a turbo engine should hold up to the same power as forged pistons - only thing forged pistons can do is take alot more detonation and lean mixture, because of the heat tolerance.
I know there is an issue with the 20vt pistons cracking at the ring lands, but i believe it's a matter of correct tuning. Monitoring EGT, AFR and listening for detonation, backpressure etc.
Jari has been making ALOT of hp on stock internals for quite some time now - so has some other of his mates. Vas has told a couple of stories to...

We have danish guys running +400hp on stock 16vt, and +500hp on stock corolla 4agze.
But we lack people with 20vt's, but some have tried and most of them have failed over 330hp on stock internals (although most of them has just plugged in a chip and cranked the boost). I am gonna try and push it a bit over 350hp, but with EGT and wideband AFR. Heard to many good stories from Jari and Vas to just let the opportunity pass by :-)

Mine went at 330bhp and it was live mapped, ringlands cracked, running forged pistons now and all seems well.

You cannot compare different engines stock pistons, there are a bunch of different designs, manufacturing techniques and different processes as well as different size of ring land and proximity to the squish band etc. etc.
This is a well known problem with 20VT pistons that doesn't mean no stock piston can take that power. There may be a pinking or det relation to all the failures yes, but it is probably more symptomatic of how the knock circuit works in the first place. At 350BHP the amount of knock detected before the advance is backed off may be wholly inappropriate for that amount of power.

Yes Jari is running more power, but it still is a question of when not if his pistons or rods will fail.

I'm sure you'd like to think that for you it will be fine, but there are so many people on here who it wasn't fine for, and it is better to either not run the power or switch pistons and rods then it is to see a failure that takes out your crankcase/block and cylinder head

really you can say I was lucky my engine went the way it did, as in nothing else got damaged!

I would also suggest that people who get their cars mapped should ask for a less aggressive ignition map. Sure you may loose 5-10bhp but it will make a significant difference to your chances.

Some mappers are very aggressive with their ignition timing, to what end I don't really know. All things being equal i.e. mechanical setup etc, when one mappper claims they can get X amount more power than Y mapper you have to take a step back. The only way to get more power from the same setup is to run closer to the ragged edge... air, fuel and spark timing that's all there is.

Not forgetting boost too ^^^

Also remember that the stock ECU can only back off 2 degrees, which is not always enough.

If the car has been mapped properly, i can't see why the knock sensors should have to retard timing - detonation should not occur!
And why would the maximum hp number be 330-340hp? It should be a matter of combustion heat, not hp. So if the timing is less aggressive, and the engine is getting enough fuel, it should be cooler with 350hp than a badly tuned engine with 300hp... But we'll see how it goes - i'm not saying all of you are wrong. I'm just an ignorant man who needs to learn from my own mistakes. If i trash the pistons i have en excuse to buy forged pistons
I have faith in my tuners expertise, so if the thing goes pop, i know it's because we have gone beyond the limits of 20vt stock capability.

Does any of you know if there has been made a new revision of 20vt pistons at some point? I saw replacement numbers in ePer awhile ago, and i just installed new, stock Fiat 20vt pistons. They were black on the skirts with some kind of coating...

Have you ever thought about the pressures that happen within the cylinder as well? If you increase the power, you're going to increase the pressure in the chambers. We ar talking around 18,000psi here, and with has been said with the ringlands, they will break.

I see what you mean about pressure - i'll look a bit more in to it, but it's a good point! But there must be product tolerances - meaning that some pistons may be able to withstand 350hp and others more or less. They cant all be 100% alike... But i guess that a safe number is around 340-350! I will think about it more, but right now i'm running 1,18 bar and will probably turn it up to 1,3 and make a bigger exhaust. So should end up at around 350-360hp...

You’re asking for trouble especially if you miss shift a gear. Squids engine had broken ringlands at 320WBHP.

http://jayman.bulldoghome.com/photos/bdres/jayman_bulldoghome_com/DSC00524.JPG
(Hope you don't mind me posting this one Squid)

That piston doesn't have the same coating, as mine do... Just worn off, or do i have a never revision?