BTW, not that I'm doing it, but I think a hole saw set fits the bill. It can take the heat, its has the gapping and its sprung so it should maybe stay in place. Maybe

 

I've noticed that most of the STU folks have the Megan/eBay O2 housing. And I've also noticed that people on the rest of the forums say that they get boost creep from that housing, whereas they don't get it with the bigger O2 housings like the Invidia.

My inference from that was that the smaller the hole between the wastegate outlet area and the rest of the O2 housing, the more creep you'd get. So I would think you would want kind of an eBay housing, but with an even smaller hole. But this is complete speculation on my part. I am not a flow analysis thermo-mathingy.

 

Even easier than a new O2 housing is crank the preload on the wastegate actuator. Changes to the boost cut (not boost map) will need to be made to make it legal. We have done some 330+whp STU cars, if I remember my classes right. I know we couldnt touch the boost map but could tune everything else in the ECU.

 

330 whp on which dyno, out of curiosity?

I am not sure that changing the boost cut is legal:
14.10.F
Boost cut sounds like a "boost or turbo control" to me...

 

330whp sounds more like Street Prepared, doesn't it? If I understand correctly, you can run a BSP Evo on race gas and advance the heck out of the ignition.

And, Street Prepared cars are allowed to change the intercooler and related pipes.

They lost the "Street" out of Street Prepared decades ago. I hope that doesn't happen to Street Touring.

 

Last time I looked into this, I thought the conclusion was that adjusting the WGA was illegal. Perhaps difficult to detect, but not in line with the rules. Specifically, I think it falls under the category of altering the "boost controls".

Anyone have any other interpretation here?

 

Last time I checked, you could run any street-legal fuel in STU. That includes E85 and Sunoco GT100 (100 octane). Of course, you won't get all that far with E85 on stock injectors, but I remember reading about one member here who did it. Must have had awesome low-end torque. GT100 is good for some extra power, but I'd probably cry while driving to and from the event with gas that expensive in the tank.

 

I have the eBay O2 housing for my IX sitting in my garage for exactly this reason. The hole between the wastegate side and the turbo outlet side is terrifyingly small due to the poor workmanship. I'm sure it would work, but I'm actually afraid it would be too restrictive as it sits. One of these days I'll put it on, set my boost cut very conservatively, and give it a shot.

But the OP has an Evo X. I don't know if anyone makes a poorly-constructed O2 housing for it yet.

 

When you say "O2 housing", are you talking about something like this?



I have one of these:


...Which is why, in theory, I can restrict the wastegate outlet without affecting the main exhaust flow.

Heck, I'm a mechanical engineer with a great interest in flow analysis, and I never caught on to the thermo-mathingy.

Sounds like I'd need a 4-wheel dyno again, AND I'd risk engine damage.
"Serious boost creep" = "engine go boom"?
It seems like it would be SO easy to insert a washer in the wastegate pipe, but I can't afford to damage my engine.

 

I bet E85 is expensive, too. Gallon for gallon, it would have about 60% of the chemical energy of straight gasoline, so you'd get 60% of the fuel mileage. If the cost was more than 60% of gasoline, it would be more expensive to drive on E85.

Oh, well... It doesn't matter in my case, since there isn't a Sunoco or anyone with E85 in this part of Florida.

EDIT: One web site says there's E85 available 68 miles away in Enterprise, AL. I can't find their price, though.

 

Sorry just noticed you asking about setting the outlet size on the wastegate. Once again changing the preload is illegal but very hard to prove.

When i mentioned changing the size of the outlet hole i believe most of the competitive guys are closing the hole down to 1/2 inch or less but most are running E85 as well to compensate for the crazy boost spike they are seeing.

To make this work on your car will cost you considerable trial and error, as someone already mentioned it will take a lot of testing to find the ''sweet spot'' on your setup and custom fab work as well to make it optimal, this is not the best setup for a DD. But if you spend the time on it makes for a sick power curve for an STU car.

 

That's what I was worried about.
So, to get any more gains out of engine tuning, it sounds like I should focus on the software. I think the shop might have left 10hp or so on the table.

 

I inserted a holesaw into my IX megan 02 sensor and it covered 2/5 of the o2 path already without any adjustment. Unfortunately its going to be a while before I can test.

 

Let us know how that goes.

 

Are there that many STU guys running e85? There was only one car that I knew of.

Back when I was setting up for STU in early 2010, my tuner (Bryan, then @ GST) joked with the idea of doing e85 on a stock fuel setup, but then didn't want to run the risk of running out of fuel and harming the motor.

I'm running e85 now, but now it's an SM car.