I recently had my tranny, LSD, TC, and some other things done for the 30k service. My car runs good, the tranny shifts good again with the new oil and everything is fine except for one thing. My boost is down a lot. I hit peak boost of 14-15 psi @ 3500 RPM and it starts to tapper to 10 psi @ 4500-5000 RPM. Since I bought my car, nearly 2 years ago, my boost has been going down. I had a friend of mine did a pressure leak test and he said everything is fine, no leaks to speak of.

The car feels like it's making less power to me. I had another friend(evo 8 owner) drive it and he said it's making power. So I'm a little confused now. He's telling me to toss away my current boost gauge and get something that reads more accurate. A couple of local owners told me to get a turbo smart ebc cause it doubles as a boost gauge and reads very accurate. My only mods are a K&N drop in filter and a self modified stock air box cover(I cut a hole on the side). Any idea's on what I should do? Can you guys reccomend a VERY accurate boost gauge for me? What are my options on this boost issue? Thanks in advance for the help!

 

The problem most likely is not your boost gauge. Check for boost leaks. Why did you cut a hole in your intake box? Do you have a boost controller of any type?

 

My friend check for leaks and didn't find any. I don't have any kind of boost controller.

 

My friends just called and told me that I should dyno it to make sure it's making the power a stock IX should and go from there......any other opinions before I do a dyno day?

 

If you are using the stock boost gauge from Mitsubishi, I know sometimes it is not very accurate. Does your car feel slower? or is just your gauge is not reading correctly?

 

I currently have a auto-meter boost gauge. To me my car feels slower but my friend, who has an evo, told me it's making power and does not feel under powered. I'm not sure if the gauge is reading right. When I first got the car I would hit 19 psi but ever since then the boost has been going down slightly to where it is now @ 14 psi peak.
Should I dyno it to make sure it's making power?

 

Is there any possibility that because of your little invention with the airbox cover, you are creating some type of vacumm or problem with the MAF reading correctly and either pulling timing or adding an inefficient mixture of air and fuel? Just a suggestion.

 

but if anything it would be boosting more because the MAF would be trying to compensate for the extra air by spitting more fuel into the block creating more boost. Besides your check engine light would have come on if it was that big of a difference. You should check the shaft play on your turbo and see if it's looser than normal. Also, check the wastegate for cracks and the spring. Plus autometer gauges are always a bad idea...

 

Good question! I'm not to sure though. When I first did the mod 2-3 months ago I actually saw a boost increase of 1 psi. I'll go to the mitsu dealer after work and pick up a new intake box cover and see what happens.

 

How did he check for boost leaks? Something tells me that you have a boost leak. Did he actually pressurize the entire intake track to make sure there were no leaks? Or did he just do a visual inspection?

 

Im gonna guess leak as well. Its also possible his DV is leaking. I cant imagine its the hole on the intake box. I have mine cut as well and dont experience low boost.

I would definately do a leak test first.

 

Well last night I got another stock box(no hole) from a local evo owner and my boost actually went down some more. It was boosting 12 psi max tappering down to 8 psi

I put back my stock box, with the hole on the side, and it was still boosting 12 psi peak. I reset the ecu and the boost went back to 14 psi tappering down to 12 psi. I did a search on boost leaks so I'm going to do a boost leak test when I get off work.

If the boost leak test shows I have no boost leak than what are my options? Should I take it to the dealer? Should I order a new stock bov and see if that changes anything? Right now I'm thinking about going to the local tuner to have my car dyno'd to make sure I'm making the proper power for a stock IX. So besides the boost leak test and dynoing the car what are my option? I guess I'll start with those two and see where that takes me.....

 

Just an idea as well...Did you check all your IC pipes and connections to see if a clamp is just loose? First check the basics that's what i always say.

 

You don't need an airbox. I don't even have one (I have a metal intake pipe with an HKS filter at the end of it) and I hit 23-25 psi. Here are your only three possibilities:

1.) Boost/Vacuum leak
2.) Boost solenoid malfunction
3.) Wastegate malfunction

 

The first thing I did was check the turbo inlet pipe, the intake, UICP, LICP, and everything inbetween. Everything was fine, nothing was loose....didn't have to tighten anything up.