Can't pass 10spi - No boost leak
 

Well, I seem to be experiencing a series of issues with my car now.
Ever since I posted in that "who never has to work on their evo?" thread lol

I installed a Forge WGA and I was adjusting the preload. It held 17-18psi to redline, then when I hit 4th gear, the boost dropped to about 15psi. Shortly after, it dropped to 10psi maximum.

Naturally, I thought that it was a huge boost leak, especially since I had just switched to all t-clamps the day before. The system was pressurized to 25psi and experienced minimal drop.

So far I have:
1) Boost leak tested
2) Reinstalled and re-preloaded the WGA
3) Checked for/replaced broken vacuum lines

I am absolutely lost as to how to proceed. Take note there is no MBC on the car at the moment, this is with a 4mm line running from the WGA to the turbo nipple.

May be stupid question but any way you accidentally completely unloaded the wg? I think wastegate pressure is like 10-12 psi or so. I'm sure you didn't but just a thought man good luck.

I don't think so, at least! The part that confuses me the most is the fact that it went from 18psi steady to 10psi mid-drive. With no modification to the WGA or anything.

Well, that and the fact that there are absolutely no boost leaks :confused:

A friend of mine just went through the same thing with his Forge. The problem was it was leaking air around the seal where the wastegate arm exits the body. You can check the easily, by using a vacuum pump (or blowing) on the vacuum line that runs to the wastegate.

He contacted Forge, and they sent him a rebuild kit free of charge. Took about 20 minutes to replace all the seals in it. If this is the route you go, make sure you use AMPLE lube on the 2 o-rings inside the body.

That's what i suspected as well. I used a regulated air compressor at 25psi to actuate the arm and test for internal leaks. That's how i found the cracked vacuum line off the WGA nipple

So lost.

Just nOticed that when I park the idle stepper and set the biss, my car idles at 1500rpm. I left t for 10 minutes and it doesn't come down at all

Is it even possible to have massive vacuum leak and pass a boost leak test?

Is your boost controller reversed? Could be a nasty vacuum leak, do you have a boost gauge? What's it reading at idle?

I am tracking down a similar issue. Keep me posted and I will do the same for you.

GL

I'm thinking its a pretty awful vacuum leak. The boost controller isn't in right now. The car's running with the WGA tee'd off of the turbo. It's a forge adjustable unit with a 18psi spring and a ton of preload.

What issues are you having? Do you have a thread up?

No thread,

Issues - same biss high idle issue, huge power loss, lack of boost.

Have tested everything I can think. All vac lines are hooked up properly. Can't find a boost leak other than at throttle body shaft seals which, imo, no biggie. WGA has been tested, no exhaust leaks, no rags in intercooler piping, no splits or cuts in vacuum lines, etc, etc, etc, etc, etc

Have you checked the turbo for shaft play?

Yep. No shaft play, no marks in the compressor housing, spins freely as well

I have the idle adjusted down to 900 via the biss because it's y daily driver. But at 900rpm my vacuum is ~19inHg if that helps paint a better picture

Edit: take that back. Definitely SOME shaft play since i checked last, although I don't think its more than what's considered "okay"

I figure that you already know but, if the shaft play is in/out none is acceptable. A few millimeters side/side is ok. Be gentle while checking for shaft play. (noobs not op)

This is definitely a strange one...

Well, I went over the car tonight and checked all of the ICP couplings. I kinda went out on a limb and guessed, maybe thermal expansion from a hotter intake charge was the reason i saw no pressure drop with a boost leak test.

Cranked down all of the t-clamps. Same problem

Disconnected the vacuum line from the turbine to the WGA, rolled on the throttle. Still hit a max of 10psi at WOT. It is important to note that the wastegate is preloaded TIGHT. The turbo begins spooling quickly without much effort

So far we can assume the following:
1) There are no significant boost leaks
2) The Forge WGA is preloaded correctly and the wastegate is not opening

I was wondering, would doing an evoscan datalog and measuring the 2byte load/MAF readings be an accurate measurement of turbo activity? My logic was, if it is a leak, load/maf would show normal/higher than normal numbers. If the turbo was on its way out and unable to provide a significant spool, these two values would be noticeably lower than normal.

Can someone chime in on whether this will just be a waste of time or not?

How can you just assume that the WGA is preloaded correctly? Don't assume anything. If you are only reaching 10 PSI something is not right or you are not taking something into account in your checklist. But, don't just assume proper preload. Don't jump to faulty conclusions.