3UZ Stock Piston Limits

[DZM]

What boost have people reached on stock 3UZ pistons?

Im building a 3UZ with early thick rods and arp head studs, rings gapped for boost and full rotating assembly fully rebalanced.

Will be running a Holset He400 Turbo.

Engine is on Megasquirt MS3.

will be running 99ron pump fuel.

Aiming to push for either 7psi or 10psi of boost using the external wastegates.

What are people’s thoughts?

 

[Zuffen]

There have been plenty of 1UZ;s running in excess of 20psi on stock unopened engines.

I can't see why the 3UZ pistons would be any weaker and if they were it wouldn't be a 50% reduction.

 

[DZM]

There have been plenty of 1UZ;s running in excess of 20psi on stock unopened engines.

I can't see why the 3UZ pistons would be any weaker and if they were it wouldn't be a 50% reduction.

Yeah I'm thinking the same, I have built early thick rod engines for boost but never a 3UZ engine and when comparing 1UZ pistons vs 3UZ pistons there is less material around the ring lands

I will run it on 7psi first and see how the engine reacts and then if it all goes well will try the 10 psi wastegate springs

Will record dyno runs and attach when done for an update

 

[gloverman]

Considerable difference with the ringlands on 3uz. Less meat between the bores but thats not really an issue most of the time.

 

[DZM]

Considerable difference with the ringlands on 3uz. Less meat between the bores but thats not really an issue most of the time.

Yeah exactly, I’ve compared the 2 pistons next to each other and it’s exactly that, someone else told me the pistons are good for 14-16psi as long as the rods are changed

I’m only gonna push 10psi at 1st and see how the engine feels

 

[Dave.pritchard....]

I play on turboing my 98 vvti.
was looking at just fitting rods and new piston rings to the standard piston and gap them for boost.
be interesting to know how much the piston can take. Or is it worth Getting new ones.

 

[Zuffen]

For the cost of a set of pistons you would spend a lot more if an existing one failed.

yes they aren't cheap but add u the cost of parts for a rebuild (assuming the block and crank survive) and you may find the cost is worthwhile.

When I built my Supercharged engine I kept the crank, block and heads. Everything else was replaced.

Not worth spending thoushands twice just to save a few hundred.