| :VE and peak achievable boost are not related at all. I don't agree with this at all. Boost doesn't necessarily mean power. Simply put, boost is caused by system restriction. A higher VE engine will be less restrictive, and will therefore see less boost, all else remaining the same. A high VE engine will produce the same power as a lower VE engine at higher boost. The higher VE engine will have a higher mass flow per psi because the volumetric flow rate is greater than that of a more restrictive engine. Because compressors can only flow a finite amount of air, the higher VE engine will exceed the capacity of the compressor sooner than a lower VE engine would. Mass flow rate is more important than boost when it comes to power production. Given identical displacement, an engine with a higher VE will have a higher mass flow rate than an engine with a lesser VE. A higher VE engine will have the same mass flow rate as a larger engine will a lower VE. Larger engines require bigger turbos to attain the same boost. :If this were the case, as other breather mods are performed on the same vehicle (short of turbochargers), the peak boost achievable will continue to lessen. This is not the case, and if anything, it can actually increase the peak boost pressure achievable by the system.
:I think your statement regarding VE and boost goes back to a statement of misconception by Greg Dupree about the GT2860RS compressor flow maps and why they weren't able to achieve over ~24psi on the vehicles they have put those turbos on.
:Improving the volumetric efficiency before the turbocharger, as in switching from a single intake to a dual intake, will improve the peak boost the system can achieve. This comes down to the fact that a turbo compressor is only a pressure multiplier: a restrictive filter/piping set feeding the compressor will lower the ambient pressure at the compressor inlet and reduce the peak boost observed at the gauge. True, a compressor is a multiplier, but ony to the point that mass flow requirements don't exceed the capacity of the compressor :Improving VE after the turbo, such as in a camshaft upgrade, will simply mean that you are going to move more air mass per revolution of the motor - this does not have any effect on how much boost a turbo will be able to produce. Eh...I think you're wong on this. The compressor must be capable of supplying the increased mass flow of the higher VE engine, otherwise boost will drop (which is irrelevant, since mass flow is what makes power) :Say the exhaust manifolds are upgraded - this will improve airflow through the engine (VE), and it will also improve spoolup response of the turbocharger. The turbos will get spooled up quicker than if they were using a stock exhaust manifold.....
:and this brings me to my final point... :)
:The major component that depicts how much peak boost you will be able to achieve with any of these turbochargers that are suited for our engines is the turbine and housing selection. The wastegate and its actuation system can play a part, but only if they are not properly chosen. You need an actuator that will provide ample wastegate closing pressure to prohibit exhaust gas bypass inadvertently.
:There are components you can upgrade in the system that will have an effect on at what RPM you achieve that peak boost, but will not affect the peak boost level itself.
:There are other elements in the system, like the intake example I gave, that can have an effect on the peak boost observed in a given application, however, the maximum boost that a compressor can produce has nothing to do with the volumetric efficiency of the engine. Here is another example: If you blow the same mass flow rate through 2 straws, yet one is 10mm in diameter, and the other is 15mm, guess which one will require more pressure? Simply put, higher VE = bigger straw :The compressor does only what the turbine tells it to. If your engine has higher VE than another engine with the same turbo, you will move more air through the turbine which spools the compressor quicker and the effect is only on the rate at which the rotating group accelerates.
:Variations in turbine selection also play a role in the boost response and can also indirectly affect the peak boost one can achieve. A prime example of that is: look at the dynochart for my Z32. I am using the same compressor wheel and housing as that of the GT2860RS. I am making 1bar of boost by around 3400RPM and I have seen some ~31.5psi of peak boost. My turbine is different from the GT2860RS by a difference of only 1 blade added to mine, same trim, same geometry - just an extra blade. This extra blade is harnessing a bit more energy from the exhaust and causing the rotating group to accelerate in rotation faster, causing the noted improvement in spoolup as compared to the native GT2860RS .64TH. But your manifolds are better than anything short of Pentroof. Don't you think that might have a noted effect on spoolup?
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