MSR Tuning - 2007 GT Auto

[peadya100]

Ive just read a few articles about them. Seems they just hold the boost slightly better... does that sound right?
Most people are also saying not to bother until a turbo upgrade. Mind you most things I read were about wrxs so may be different. I asked MSR anyway so ill see what he says.

[alexeiwoody]

posted from http://legacygt.com/forums/showthread.p ... ost1020449

"I posted this a while ago but the original thread seems to have been nuked as it was in the TDC forum...


+1. Nice to have the safety margin and it is also possible (in theory) to achieve faster boost response without overshoot. If you consider the way the boost control loop works you will see that there are two dominant sources of delays in the loop. The big one is the actual response of the turbo. The second one is the delay between waste-gate action and the onset of boost at the compressor outlet. With bigger delays the trade-off between overshoot, boost response and controller complexity becomes tighter. Since we have little control over controller complexity (we can change the calibration but not the algorithm) we are forced to trade off boost response and overshoot.

The 3 port solenoid allows us to decrease the waste-gate actuation delay whereas the stiffer actuator doesn’t really unless the air chamber volume has been decreased (unlikely as the diaphragm needs to overcome a bigger spring now). The stiffer actuator does have an advantage, but I’ll get to that later.

Most claim that the 3 port solenoid speeds boost response by being a blocker type solenoid. This isn’t entirely true with the WGDC we tend to run. There is actually a secondary mechanism that causes the faster boost response. If our boost controller were to hold the WGDC at 100% during spool-up the blocking mechanism would be the explanation. During spool-up one probably sees 50-60% duty cycle and the boost is alternately fed and bleed from the actuator. Under these conditions it is a decrease in effective pressure source restriction to the actuator that allows faster spool-up. This is counter-intuitive so a little explanation is needed.

Consider the case where the stock bleed valve is closed completely and pressure is stepped above the WG setting. The actuator wouldn’t do anything at first as the chamber volume needs to be filled with air before the diaphragm is pushed. The stock restrictor pill slows down this response. The smaller the restrictor orifice, the longer the delay before the WG opens. If the turbine is spooling rather than holding a constant speed there will be a boost spike above the target pressure while pressure is building in the actuator. As one reduces the orifice, the delay gets bigger and the spike gets bigger (everything else being equal). So why not use a larger orifice? A larger orifice works contrary to our goal of more boost/fun. With a larger orifice, we are unable to bleed away enough air from the actuator to delay the opening of the WG till higher compressor outlet pressures. With the stock boost control system we are forced to make a trade off between max boost/ boost response. If we want more boost and we use a smaller orifice, the WGDC must now be programmed to bleed less just prior to target boost so we don’t get a spike due to the increased WG actuation delay. This softens the boost response. Here is where yet another effect, which control engineers really hate, comes into play. The effective delay one sees will vary with WGDC. If the WGDC is 0, the orifice area and chamber volume sets the actuator’s delay. If WGDC is 100% the delay is set by chamber volume (as expected) and the sum of the orifice area and the smallest internal area of the bleed valve. At settings in between, the effective orifice size is a weighted average based on WGDC. The change in actuator response forces the tuner to compromise low boost response to avoid spiking at max boost. This is where the 3 port solenoid becomes very handy.

The 3 port solenoid works like the stock bleed system except 1) the feed restriction and bleed restriction are balanced 2) 100% duty cycle causes complete blockage of boost. Point number 1 helps by allowing us to have similar actuator response times irrespective of target boost. No compromise needs to be made between boost spiking at max boost and response and lower boost. We are able to get good transient response by virtue of the large effective orifice diameter AND good control of the ratio of actuator pressure and compressor outlet pressure. Point number 2 helps too if one is willing to allow very high WGDC during spool-up.

While a 3-port solenoid does have many advantages over a bigger actuator, a larger actuator does have its uses. Most WG + actuator systems (non butterfly valve types) have 3 forces balanced against each other: 1) The spring tension holding the flapper valve shut 2) the boost pressure pushing the diaphragm * diaphragm area 3) the turbine differential pressure * WG flapper area. As engine speed increases, turbine differential pressure increases for the same boost level. This means that the WGDC needs to increase to maintain boost as #3 is increasing and #1 is constant. With a larger actuator, this effect is decreased.

Personally, I’d want a 3 port solenoid + a butterfly type WG valve."

[peadya100]

Geez thats a light read for someone like me that knows only the basics

Mick told me that the 3 port isnt necessary for me with the stock turbo. Ill ask him to explain it to me in an idiot proof way when i see him in a week

Thanks for all your help!!

[shav]

Nice information you quoted Alexei. I have a 3 port Pierburg unit and I noticed the difference after it was fitted and tuned.

[PoidaGT]

MSR said I didn't need one with my bigger turbo either. Said they were a waste of money and not required. They sound sound good in theory.

[alexeiwoody]

Msr knows his stuff

Having said that - it does give you more control over tuning the wastegate/compressor than the std 2 port. And a touch steadier boost too. You probably won't even notice the difference though, but a little safety measure for $100 definitely worth it IMO

[<GB>]

My car was running the factory solenoid at around 200-250awkw didn't seem to harm it

[alexeiwoody]

Nice information you quoted Alexei. I have a 3 port Pierburg unit and I noticed the difference after it was fitted and tuned.

What sort of difference did you notice shav?

My tuner is in the states, so the 3 port seems to have really helped eliminate boost spikes and smooth things out abit. With a dyno though, a good tuner might not need the extra control the 3 port allows for. As things are much more transparent on a dyno than through a bunch of numbers that logs are

[shav]

I noticed the boost coming on sooner. It felt like I had more torque down low. Also felt the boost was delivered smoother as it hit redline.

[peadya100]

Hey Shav,
did you get your car tuned at the same time as you put the 3 port on? Is it possible that the gains you felt were just due to the tune?

[shav]

Hey Shav,
did you get your car tuned at the same time as you put the 3 port on? Is it possible that the gains you felt were just due to the tune?

Yes I did get the car retuned at the same time. Its recommended you do. The retune in conjunction with the 3 port helped make the boost more efficient and stable. As well as reducing the wgdc and allowing the tuner to bring the boost on sooner.

[KiDo_Tuning]

Hey Shav,
did you get your car tuned at the same time as you put the 3 port on? Is it possible that the gains you felt were just due to the tune?

Yes I did get the car retuned at the same time. Its recommended you do. The retune in conjunction with the 3 port helped make the boost more efficient and stable. As well as reducing the wgdc and allowing the tuner to bring the boost on sooner.

It was tuned before the 3 port then retuned with the 3 port on 4 months later though. Gains on the 3 port are noticeable

[peadya100]

Thanks Matt.. that was the answer I was looking for.. whether or not the gains were from the initial tune or the 3 port. However MSR recommends I dont get a 3 port so I have to trust my tuner and do what he wants.

[shav]

Thanks Matt.. that was the answer I was looking for.. whether or not the gains were from the initial tune or the 3 port. However MSR recommends I dont get a 3 port so I have to trust my tuner and do what he wants.

Let us know how you go. Id be keen to find out what he can get sans 3 port.

[peadya100]

Thanks Matt.. that was the answer I was looking for.. whether or not the gains were from the initial tune or the 3 port. However MSR recommends I dont get a 3 port so I have to trust my tuner and do what he wants.

Let us know how you go. Id be keen to find out what he can get sans 3 port.

We'll find out in a few days i guess. What did your car make with the tune and 3 port?