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Turbo maximum hp question

Cool Hand Luke

By Cool Hand Luke,
in Engines & Forced Induction

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Cool Hand Luke Community Regular

Cool Hand Luke

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If a car is developing the maximum hp that a turbo can develop, and you do other modifications to the car such as head, cams etc will you get a hp increase? The reason why im asking as the turbo i currently have cant develop any more hp on the car, no matter how much more boost i run. Im rebuilding the engine (sr20) with solid lifters, cams, rods and head modifications and are curious if the turbo will hold the engine back.

Im running an external hks wastegate but its quite small, what would the effects be if the wastegate is too small? Or what advantages are there going to a larger one?

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Cubes Grand Master

Cubes

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Posted

Once you run off the efficiency envelope the turbo will heat the air. At some point superheating which is why you don't see any power Increase when increasing boost, sure slightly more air will enter the motor with the higher boost but the draw back will be that it is hotter and less dense.

Headwork, cams etc improves VE (cylinder filling) which allows you to cram air in to the pots with less resistance.

More air = more power.

Less boost = denser air = more oxygen = more power.

Smaller wastegates will allow you to hold higher boost levels without boost tapering off. The only problem with them is if you select a wastegate to small it could cause boost creep where boost keeps heading north as you increase the rev's.

I'm sure you have heard of this happeneing on some bad T3/4 highflows when their internal gate hasn't been enlarged.

A wastegate that is too large, will increase spool time slightly in turn reducing the power under the curve slightly.

It may even be so extreme as boost has trouble being held constant as when the large wastegate opens it bypasses soo much exhaust gas boost will drop below its set level, the wastegate will then close and may cause a wavering boost level.

Run the turbo with the new motor and if you want more power upgrade then. :D

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