That depends what you plan on running with the TD04. I have used TD04H on 1.8 all the way to 7000 rpm holding 1.2 bar. My current setup runs at 1.0 all way to 7k rpm on 2.0 engine without dropping boost. I have tested the TD04 running out of breath at 1.4 bar at max rpm when my vacuum hose to the actuator valve popped out on my old 1.8 GSR. Good thing it ran out of breath there otherwise I might not have an engine left.

The only thing regulates the boost pressure and that is the wastegate/actuator valve together with the solenoid connected to the ECU. The pressure is always measured after the throttle body. The BOV plays no part in the regulation of pressure as it is there to play the role of a release valve when the throttle body shuts to prevent pressure building up in the intake pipe. It does not ever play the role of pressure regulation. It's more of a safety valve than a regulator valve. The throttle body does not regulate turbo pressure either.

The throttle body does not directly regulate boost pressure. Meaning you can keep your foot at 50% throttle, the boost will climb and then once you reach a fixed speed, the boost will drop. So the throttle body is no longer considered as the component incharge of regulating the boost. Taking your foot off the gas is not considered as regulating the boost pressure. That's more like regulating the whole engine operation and not just the boost pressure alone.

Most OEM turbine with actuators valves run with solenoid, even on my old 1994 GSR. That's an 18 year old car. The manufacturers use the solenoid setup to activate limp home mode to cut the boost by allowing the full pressure of the boost to reach the actuator which is set to open at a lower level (usually half of full boost). The solenoid then acts like a boost controller in normal running mode to bleed the pressure away so that the turbine will maintain the OEM boost pressure. Think of it as a poor man's boost controller but you can't change the settings unless you mess around with the ECU. On most OEM cars, if you remove the solenoid and pipe the hose direct from intake manifold to actuator, you will only get half boost since the spring settings are made to open at a lower pressure.

Majority of the owners then remove the solenoid and replace with an aftermarket boost controller. That is why you don't see much solenoid/actuator setup because most have been replaced with aftermarket boost controllers. You want to easily see an OEM solenoid/actuator setup? Just pop the hood of Preve CFE and you can see it right next to the actuator valve. Most manufacturers put the solenoid as far from the turbine as possible so that it does not get cooked but not Proton. You will also find it on almost all OEM turbo engines but you will have to trace the vacuum hose since the solenoid place quite far from the turbine actuator.

This post has been edited by sleepwalker: Jul 17 2012, 12:50 AM

It's not about the debate. We are talking about your understanding of the word regulation and not about the workings of the engine. You regulate engine function with the throttle body and regulate the turbine pressure with the acutator/wastegate. You do not control the pressure of the turbine by using the throttle body.

20% throttle on 4th/5th gear I can bring my boost to almost maximum on load while at the same time 20% throttle on 1st gear hardly gets the boost to 50%. That is what I meant by turbine boost regulation is controlled by actuator/solenoid which is electronically controlled from the ECU taking engine load as a factor. Here the opening of the throttle body no longer controls the boost. The more load I put into my engine, the more boost I get from the same throttle body opening. That is why I kept saying that you can't consider the throttle body as part of the turbine boost regulation. The throttle body is more on controlling the engine as a whole.

Yes, once you take the foot of the gas, throttle body shuts and boost drops but we don't consider that as boost regulation. There is no DIRECT correlation between boost and throttle body except when the throttle body is shut. That just shuts down engine operation to 'idling' mode or deceleration mode. Hardly considered as boost regulation.