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Boost VS RPM

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Hi to everyone. I was wondering which is more stressful for the engine.

Let's assume that we have a 4 cylinder N/A inline engine that has a rev limit of 7k rpm.

Adding a turbo (10psi of boost stock rev limit ) or raising the rev limit to 8500 rpm (let's assume that power is being produced) is more stressful?

Everything else being equal, stock block,both have a safe and good tune.

The power/torque output of the turbo engine will be higher for sure. What causes more stress on rods, bolts, pistons etc...

hard question but i would be going with rpm would be mr stressful if all thing where concidered and the tune was good

maybe some one else would like to jump on this

Hi Lewis, the two factors you need to consider are the cylinder pressure and the forces imparted as the rpm increases. Either can damage your engine components so you need to account for both. Adding boost will increase the cylinder pressure compared to N/A and this adds significant compressive load on the conrod which can fail if the conrod can't support this. On the other hand increasing rpm has the most impact on the tensile forces applied to the conrod big end bolts (in particular) as the piston goes past TDC as it transitions from the exhaust to intake stroke. So both situations apply stress to the conrod and the piston, but in different ways.

Which is better/less stressful is impossible to say without a lot more information. In reality if you're using quality components neither situation should be probelmatic.

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