Spooling up Slower in Low Gears

[CowPimp]

My turbo (FP Big28, check my profile for more info) is hitting full boost at much higher RPMs in lower gears. First gear it comes on about 4000+, 2nd gear is about 3600, 3rd gear is about 3300, 4th gear is about 3000, and 5th gear is 2800. I don't understand the discrepancy between gears.

I had a similar problem a while ago. However, I discovered that 3/4 of my exhaust manifold bolts were coming loose (The 4 on top of it). Tightening them solved the problem temporarily, but apparently I also had a blown gasket on the turbo side of the exhaust manifold. I replaced that gasket, as well as the one on the engine side, tightened the 4 bolts once again, and all was well. Full boost at 2800-3000 in all gears. This was many months (Maybe 6-9?) ago.

One of the bolts came loose again about a month ago. Prior to this, to my knowledge, all was running perfectly fine. I popped the hood to tighten it and snapped the bolt. Thankfully it was loose enough that I just snagged the bottom of it and hand screwed it out. I eventually replaced the 3 that kept coming loose and they have stayed tight as can be, but since then I haven't been getting the proper response from my turbo that I expect.

Any ideas? Should I consider getting studs instead of bolts for the exhaust manifold? Think it might be a boost leak? What about a wastegate issue (I tried manipulating my wastegate but couldn't get it to move at all, but I don't really know what I'm doing honestly)?

Thanks in advance.

 

[CowPimp]

Just a small update, I was able to move the wastegate actuator arm; I didn't realize you had to apply so much force. I don't really have a lift or anything that lets me get under the car. Is there some way I can test to see if the flapper is closing all the way?

 

[CowPimp]

Another update: After looking around for information about potential causes for this problem and such, I realized that I am using 4 bolts in my manifold as opposed to 3 bolts and a stud. Now, I had my car running fine without a stud before, so I tend to think this wouldn't be an issue, but I just thought I would add that information.

 

[Korndogg]

you should deffinitely check for boost leaks. doesn't take long.
did you make sure that the gasket between exhaust mani and turbo is still find with all of the bolts changing again?

studs wouldn't help you, and they're a pain in the ass when it comes time to pull the turbo again

let us know about the boost leak test and make sure nothing is leaking at 20PSI (it's very noticeable)

 

[CowPimp]

I didn't look at the gasket, but before I could feel air streaming out from that connection point. I guess checking for boost leaks is my best bet. Is there any way I can test to see if my wastegate actuator is starting in a fully closed position?

 

[CowPimp]

I had a mechanic friend of mine give the car a run and such. He claims that the cat is clogged. What do you think about this possibility?

 

[CowPimp]

Well, I picked up a test pipe at a local shop and slapped that on in it's place. It did make a difference, but the problem is not totally resolved. My idle is smoothed out, and the exhaust note is actually a little quieter during certain times. That leads me to believe my cat was clogged to some degree. Basically, every gear spools up a few hundred RPM less. 1st gear still seems ridiculous at like 4K, but I admit it is really hard to tell when I hit full boost in 1st because it runs through the gear so fat.

My check engine light didn't come on. I have no idea why not, but it didn't. Should I reset my ECU? Not that I want my CEL to come on, but I mean is there any other good reason to have the ECU reset?

Still haven't tested for boost leaks. I promise I'll do that soon.

 

[Defiant]

My turbo (FP Big28, check my profile for more info) is hitting full boost at much higher RPMs in lower gears.

Yeah. There's not as much load on the engine, so the turbo output just feeds the engine instead of backing up in the plenum.

 

[CowPimp]

Yeah. There's not as much load on the engine, so the turbo output just feeds the engine instead of backing up in the plenum.

There has always been a slight difference, but the disparity is too great. Right now it hits full boost at 2800 in 5th, but it's more like 4K in 1st. It definitely used to hit full boost right around 3K in 1st gear.

Like I said, I will boost leak test in the near future, but I have to focus on finishing up my timing belt purchases at the moment and worry about the slight additional lag later. I have to make sure my car survives before I blow it up. Heh.

 

[CanadianTSi]

It's all about load on the Engine, good luck even getting full boost in 1st with a big turbo...