Hey Guys,

I'm not a total turbo newb, but I have a long way to go.

I'm currently piecing together a stock EVO 8 while making plans for the future. I just bought a stock 8 turbo without a WGA. I started looking into picking up a stock or aftermarket WGA.

My first question is with a stock turbo, where does an upgraded (TurboSmart) WGA help someone out over stock? Is it a matter of the spring holding the flapper closed easier? Maybe someone could help clear that up for me. I'll be running stock boost for a while, but like everyone else will crank it up down the road.

That leads me to my next question. Boost control. I was reading the How to Tune your EVO primer. It deals pretty well with logging the boost using an upgraded sensor, but my question is more related to using the stock ecu to control boost versus an MBC or aftermarket EBC. I'd like to do it all with the ecu and a GrimmSpeed. Is that fine? Seems like people are always talking about how great the stock ecu is, but I see everybody saying to buy a Hallman. Is it just a simplicity thing?

Thanks in advance.

Brady

 

Brady,
i would recommend reading the few pages of information that Garrett has on the topic.

http://www.turbobygarrett.com/turbob...rbo_tech_basic

they have basic, intermediate, and advanced pages. Read them and come back here with questions.... we can help explain.

For the wastegate actuator question. Why use an aftermarket wastegate solenoid?

The spring inside the single (lower port on the diaphragm ) port actuators can be different pressures. As the boost pressure pushes on the diaphragm it pushes the rod and opens the wastegate flapper via a pivot on the turbine housing. By using a stiffer spring it will take more boost pressure to open the valve.... which effectively makes you run more boost.

What people are trying to achieve here is keeping the valve closed right up until their target boost is achieved and then open it up. This will allow ALL the exhaust energy to be put into the turbine wheel and not dumped!

People can also adjust the "pre-load" on the wastegate actuator in order to apply a higher than normal clamping pressure to keep the flapper closed and it would require more boost to get the valve to start to move off the seat.

FP makes higher pressure actuators that work well. i would recommend them. The are rated in boost pressures that the internal springs should control to if the wastegate actuator rod is adjusted properly. If the actuator rod does NOT have pre-load and has a "clearance" the flapper in the turbine housing does not actually seal off the exhaust gas and your wastegate exhaust gas too early...or all the time. This makes the turbo respond very slowly.


Now for your question about running an EBC and the ECU based boost control versus say a Hallman MBC. MBC's are simple and easy. They are not more effective than an EBC by any means.

By running an EBC controlled by the ECU based boost control you can keep the wastegate closed just prior to your target boost and then show it the signal when you've achieved your boost target.

The ECU software is a Feed Forward closed loop controller. So you'll have to setup an open loop wastegate duty cycle map and then enable the closed loop afterwards. the gains are (from my experience and what Mychailo (mrFred) have said) are Integrator terms only. So the Integrator term will correct offsets, but won't make large proportional adjustments. I've used it and it works well.

My suggestion from doing all of what you're discussing... I would run the OEM actuator, or the FP 18psi actuator, I would run an AEM "MAC" 3 port valve bought from ebay for about 40 shipped, and then use v7 Tephra mod with EBC controlled Boost (boost by gear)

I hope that helps

-Eric

 

Hey Eric,

Thanks for jumping in so quickly. Love your build, btw.

I understand what a wastegate does. My question is why I would want anything other than a stock wastegate if I'm using boost control? Does the stiffer spring just help me fine tune things?

If I read correctly, the stock 8 actuator is 8psi, correct? I know that if I ran directly to the wastegate, the car would run 8psi. But our cars don't do that. The BCS intercepts it and modifies it. I've searched around and found that people running larger internally gated setups, or even pushing their 8 or 9 turbos run wastegates with stiffer springs. Does this just keep the flapper from leaking a bit while building higher boost, or is there more benefit to it?

Thanks for the Garrett link, I'll check it out. Picking up my EVO tomorrow to start putting it together!

Brady

 

Thanks & your welcome.

Something to take note of (since I don't remember exactly how the stock EBC works) but there are two different methods of changing the signal. One bleeds the boost signal into the intake pipe (which I think the stock unit does) and the other type Blocks the signal from the gate by closing off the vacuum connection.

Of course both of these types use a solenoid and that solenoid is pulsed open and closed at their specified RATE and duty cycle.

I would use a FP actuator or a stock 9 actuator. The 8 turbo is a pretty weak unit all around. You hit the nail on the head. A higher pressure actuator will help prevent the flapper from leaking while running higher boost.

Don't forget to read up on how to plumb the vacuum lines depending upon how your boost control is setup as well as how to set the pre-load correctly on your wastegate actuator.

Best of luck! Enjoy your Evo.