boost vs compression ratio

[powered by wattard]

What compression ratio's and boost are other teams running. We have seen 20psi boost with a static compression ratio of 13:1, however, piston meltdown occured quick.

For those who have experienced piston meltdown, did the inlet or exhaust side top lands break off.

William Attard
MUR Motorsports, 00-04

[Frank]

ummm...

how expensive is this getting william?

[The guru of guru's]

Howdy Willy.
We ran 6psi with standard comression ratio of kawasaki had no troubles at all.
Cheers

[jack]

william, you running gas or e-85?

[powered by wattard]

Jack, were running 98 Octane pump fuel

[Silsport]

William,

What kind of turbo were you using?

Silsport

[SimonUK]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> We have seen 20psi boost with a static compression ratio of 13:1, however, piston meltdown occured quick. <HR></BLOCKQUOTE>

What did you expect.

I cant imagine how high the cylinder pressure would of been.

[powered by wattard]

High cylinder pressure does not break pistons. From our cylinder pressure transducer trace, we had peak pressures of 120Bar, which from what I have seen is high, but workable.

What breaks pistons is knock in the end gas region, which when speeds increase over 6OOORPM, the burn rates are so fast, that it basiclly doesn't have time to knock. In the old F1 turbo days, Honda ran 4Bar boost with a high compression ratio, and detonation wansn't an issue due to the high speeds.

Our failure was due to poor mixture tuning as one cylinder ran leaner than the other, and we were sampling in the richer cylinder.

[SimonUK]

Surely though at that inlet pressure the increase in cylinder (and piston) temps due to the high compression are going to be extremely high.

Probably why you melted the piston rather than detted it to death.

Certainly would be nice to run 20psi though, only problem is that your restrictor chokes a lot earlier in the rev range.

[pengulns2001]

even thuogh this is an old post its probably worth mentioning knock did not melt your pistons pre ignition did