Thanks

[RTL69]

I was looking for ideas on a problem I seem to be having. My Turbo is not quite putting out what it should. It will not ever hit the limit on the controller, any more. It does still boost, just not as high, and less in lower gears, and less on flat roads than on hills. Any ideas on how to combat this problem?

[Conicidal]

Yikes - sounds to me like the rotors and/or bearings are going...  I hope I'm wrong, but it could be time for a new turbo.

[WRXRacer111]

What car? Offhand... pre-turbo leak on the exhaust side could cause low boost, but should be LOUD. Charge-side leak is another thought, sounds like a whoosh. Is the wastegate sealing properly? If the spring preload is adjustable on the wastegate arm, you might try checking that to see if it's still getting clamped shut. On my WRX it got loose enough that the wastegate clattered at idle, spooled slowly, and was down around 2psi at peak. Of course, if you overtighten it, boost spikes all over the place and the car pulls timing as it freaks out trying to figure out what the heck is going on.

[prsrcokr]

I'm thinking boost leak (charge side like Chris mentioned) Do you have a vacuum gauge on the car? If not you can check vacuum on the manifold side to make sure you're getting 18-21 in-Hg.

Sounds like a load issue since you're building less pressure in lower gears and flat grade so it could be a wastegate issue (not sealing and allowing full pressure, but more exhaust flow due to higher load allows more psi to build) Like Chris said, see if there's play in the WG arm.

[RTL69]

Everybody seems to be coming to the same conclusion. Wastegate. I hope that is the problem. It is cheaper. Chris, for your answer to what car, it is the Yellow Paseo. I hope I can get it fixed soon. It is funny, the car still drives the same everyday, only pushing it doesn't have as much push. I have been watching it and the more I punch it hard, the more it seems to come up. I reset the ECU and that did nothing. We thought it might have been pulling timing. Next, I suppose is the vacuum lines, wastegate, then the ignition. If all else fails, bigger turbo, right? Then that brings on a whole new load of money I wish I had... Thanks everyone for the help. it is always useful.

[WRXRacer111]

Keep in mind it's probably not going to make the same amount of boost in hot weather... which is not necessarily a bad thing depending on how close you are to detonation. Aggressively tuned WRXs haven't been very happy on the 10% ethanol summer-blend gasoline either. You might want to ice down the intake manifold/intercooler if you have one and do a drive right after to see if that makes any difference. If you have a knock sensor, you might try octane booster to see if it's picking up any light knock and pulling timing.

[Edited on 8-30-2006 by WRXRacer111]

[prsrcokr]

What are the variations in boost pressure you're seeing (1 or 2 psi less than normal or 5-6 psi?) If timing is being pulled it may not make a huge difference as you're not using a factory system. I had a broken knock sensor causing power to be low and intermittantly changing. I was still making max boost but the timing when this occured caused much less power to be made. Does your setup have knock/boost referenced timing control?

[RTL69]

I am not going to lie, I never really payed too much attention to the boost pressure at first. I do know that at .91 bars the ECU cuts off. The car had hit that before, but only in 5th. I never really paid too much attention, but in 5th for sure it made max boost which was about .88 bars. Now, I am lucky to get .8 bars out of 5th gear and I only max out at .5 bars in 1st and it is gradually coming up from there. .6 or so in 2nd, about .70 in 3rd, .74-.76 in 4th and like I said, max out in 5th at .80, even though it should it .85-.88. Timing is not being pulled at all, that I can tell, but I so have a stock ECU and ignition. This motor has ignition problems at higher boosts, maybe it is just happening early now, I do not know. The car still feels the same, just the numbers aren't adding up. Especially on the last track, but maybe it was just my bad driving. I usually do not do that bad though. I do not know about a knock sensor, but I will find out from the shop who did the work, they will know. I do know that the more I punch it and force the boost now, the better it is getting. It is becoming more responsive, so maybe it is just my boost controller learning my daily driving and keeping it low... Smart computers these days... Incase you want to know that, it is the Blitz SBC i-color boost controller. I do not think that is broken....

[prsrcokr]

0.88 bar is 12.9psi , 0.8 is 11.7 so you're talking about just over one psi difference. What Chris mentioned about the temperature making a difference in pressure could account for this difference (less dense air on a hotter day)
Does your controller have settings that are gear dependent? Many of the high tech ones allow varying levels in each gear. Check to see if the peak level is set based on gear, if not it could be a leak and it's taking more and more load (taller gear) to overcome the leak and reach the max pressure.