Whilst installing the SS/Ebay O2 housing, I tightened the actuator 2.5 turns. It boost creeps with the AVC-R turned off as the graph.

The boost is higher than sensible on 93 octane with no meth in 4th gear:

RPM Timing Knocksum
4500 6 0
5000 4 4
5500 6 3
6000 8 1
6500 11 0

Of course I only did this once.

Now I've loosened the actuator to stock+1 turn and it still creeps but not so bad, so back to stock and will test again tomorrow and I expect it will be running less than I want to run with the AVC-R off. Even as stock with an exhaust and airbox lid mod it used to creep from 0.8 to 1.2 bar, but this was always lower than I wanted to run.

How typical is the boost curve I showed for people that run meth on the stock turbo with O2 housing, 3" catless exhaust, airbox mod?

 

Tightening WGA preload will require more psi on diaghram to get it to open, a ball- spring pressure regulating device (MBC) would make an easier fix but once you make one change to the system, you have about ten more adjustments down the road

Is it common to require greater WGA preload with O2 housing upgrade?

 

I just happened to do the WGA at the same time because of access whilst fitting the O2 housing. Obviously I overdid the WGA and the arm didn't have enough movement because of the pre-load.

I could previously hold almost the same to 6000, but only 20 PSI at 7000 RPM with the AVC-R duty at 90%. However, I was usually using methanol 10% in tank to do it which was effective.

My interest in what top end boost was available was provoked by some secondhand advice from a Evo tuner who suggested that the stock turbo could run 1.8 bar to red line and make 450 BHP on our pump fuel, if the story I have is correct. Everything I know/believe tells me that this is far more than the turbo is efficient at, and it was in reference to an engine with uprated conrods FWIW. So normally I would dismiss this idea, but the tuner is hugely successful and I have learned to not dismiss ideas that seem out of the box.

One way is to test a variety of boost levels, but the difference between taper and creep on the stock WGA is only a few turns of the turnbuckle it seems.

So I wonder if there would be a gain with meth on an aftermarket actuator to easily run the sort of top end I show here with good control midrange?

 

What whp are you trying to achieve?

 

I want to get the maximum possible or near to it with 20% methanol, 80% 99 RON, although not to be run like this all the time.


I know you ran about 32 PSI midrange and we previously discussed your large proportion of meth, but are you willing to say what boost you ran at 6000 RPM?

 

If you can figure a way to alltogether cut the pneumatic signal to WGA beyond 6000RPM then your there

 

You could do that with the zeitronix wideband, audio/visual trigger, relay and our boost solenoid.

 

Actuator is now stock and it still creeps. I'll keep loosening or even run the flapper disconnected to see if the O2 housing can actually flow enough. Presently I'd need about 50% midrange duty and 0% at the top end to run what I want, not ideal at all.

 

excuse my ignorance but its the AVC-R meant to take care of boost control?

 

Yes but nothing can control boost creep except actuator adjustments or heaven forbid (because there were so many issues fitting it) porting the O2 housing.

 

Loosening the actuator (quite a lot) has reduced the creep to just a little more than it did before the O2 housing, so I do have a reasonable range of adjustment to bring up the top end.

So my question remaining is:

What sort of boost pressure at 6000-7000 have people found to give maximum output on 93 with 20% methanol on the stock IX turbo with the bolt ons I describe? This will help me set my actuator accordingly, which is just a bit of a hassle compared with tweaking a boost controller once I know the range to aim for. I appreciate any help as it will save me a lot of time.

Also on clarifying the story about 1.8 bar to the red line, it sounds like that was a flat boost controller setting and to let it taper as it wanted to after about 6000, although 1.8 bar at 6000 RPM is still quite a lot I feel! The problem (or the opportunity if you like) is that we can control that taper to some degree with actuator adjustment or stronger actuators, so I want to know what to shoot for

 

JCS I too played with the WGA arm only to find what you did a few months ago. Basically you want it fully extended so that the WG opens completely. If you are still getting creep then you probably need to open the port up a bit (fairly easy). I am running 24.5 psi (peak) now on 93, but am in the process of having the car shipped to Ca. and preparing the car for 91 + Meth ....I will have the car setup for ~28psi peak on 91 + Meth. Good Luck!

 

Aim at 1.8bar held to 6500 rpm then taper. Aim at a flat boost curve. I would think if the boost does not creep/rise higher than 1.8 mid it should hold flat to 6k rpm with obviously more duty there.

Sidenote, we can see why the O2 housing would give more power because of the boost increase.

Any tuners out there please feel free to advise of your experince!

 

The O2 housing may increase the boost creep because:

1. The outlet for the turbine is so much larger/smoother than the stock item

and/or

2. The wastegate outlet is restrictive

I can't tell which, and even on the stock actuator with just basic breathing mods I was creeping 0.8 to 1.2.

I've read a few threads about people running 22 PSI (about 1.5 bar) at 7000 RPM with alcohol, I'm quite interested in what people have found works nice at 6000. I do think 1.8 bar at 6500 RPM is going to be very inefficient and risky to any motor forged or not?

I can make compressor map spreadsheets and make VE asssumptions like the best of them, but we don't have the turbine maps, and I'm not even sure we have the compressor map for the IX compressor wheel/housing combination.

So I'm looking for a few tips to get me on the right track quickly without unneccessarily frying my engine with excessive top end boost when we know it may not work?

 

So is upgrading to an aftermarket O2 even worth the hassle w/ boost creep vs. the stock O2 housing, in spool up characteristics, or is this just in certain cases? This isnt neccesarily related, but sounding like part of the prob...? No?