8 replies to this topic

[Mattias]

Me for one has been wondering about the boost/power limits of the stock turbo block, RnD Motorsport managed to brake one:

 

https://www.facebook...024180471195410

[tibby]

Think they just got Lucky

 

 

[chickendippers]

Crazy guys up at RnD, always pushing the boundaries of what these engines can take and the only guys we would recommend to map the Z20.

 

 

[Nev]

It's good of them to share the info.

 

I have heard of an ordinary Z20LEH block failing at 350 HP, so I think there is a quite some variability in it.

 

[Mattias]

It's good of them to share the info.

 

I have heard of an ordinary Z20LEH block failing at 350 HP, so I think there is a quite some variability in it.

 

 

That is why they point out that the tune was good and no knock, It's not hard to kill an engine with a bad tune. That is often the problem with google finds on the subject, without all the facts the result is useless.

[Nev]

I doubt it's the power or the torque that directly dictates when the upper cylinder walls crack. It's much more likely to be the dynamic compression at TDC, which in turn is dictated by static CR + added boost, as well as things like ring leakage, valve seal, effective swirl etc.

Edited by Nev, 22 January 2018 - 05:13 PM.

[Mattias]

I doubt it's the power or the torque that directly dictates when the upper cylinder walls crack. It's much more likely to be the dynamic compression at TDC, which in turn is dictated by static CR + added boost, as well as things like ring leakage, valve seal, effective swirl etc.

 

The list that dedicates the cylinder pressure is almost every part along the way from air filter to exhaust tip and engine map.

Swirl is mostly used for diesel combustion and on some petrol engines that have a swirl flap that closes one port on low load/air flow. Our engines has tumble based combustion. 

 

It's peak pressure during combustion that breaks the cylinder wall and that happens after TDC assuming the spark timing is correctly set at MBT or knock limit. And the cylinder pressure is what makes torque. So for a specific engine, torque is a good way to measure the limits since we don't have ICPS (in cylinder pressure sensors) that are used during engine development.

 

But again, bad tuning can kill the engine at less torque at the wheels ie. to advanced ignition timing, detonation etc.

[Nev]

Also, people think every block is the same. They are not, all metal when cast has flaws and voids etc.

 

I had a casting void in a camshaft lobe once, most peculiar, appart from being stupidly expensive to fix it taught me how variable casting can be.

[Mattias]

Yes, what we want is this

 

https://www.youtube....Wyu4to4jws&t=9s