fstfwd

iTrader: (1)

Boost issue you say? well... I'm sure I'm not the first to have one of those problems. I know, because I searched on hear and got 1400 posts. Unfortunately... I don't have enough time to sort through all of them... I'm hoping that someone out there was unlucky enough to experience the same problem I am.

THE PROBLEM:

Push gas to floor...car builds boost nicely up to 4300rpms... second turbo kicks in... continues building boost... this is good.

Take foot off gas. BOV engages... this is good too.

Press gas peddle down again... NO BOOST AT ALL... this is NOT good. Pitch of motor even sounds a little different as if it were straining. Hard to hear turbos spooling (though it sounds like something is happening)... Boost gauge doesn't go past 0psi.

This ONLY happens when you go past around 4k which causes second turbo to kick in... You can boost and release all day with the primary... get fool boost... just don't pass that 4k mark... cuz once you release the gas - your screwed for about 5-10 seconds.

After about 5-10seconds, generally faster if you keep your foot off the gas, you can start to build boost again, and everything returns to normal... but - you can repeat this problem every time.

THE HISTORY/KNOWN FACTS:

This problem has persisted through and engine rebuild, a turbo rebuild... which in both cases NEW vacuum hoses were put on.

KDR has been working on my car... and I spent several afternoons down there where Dave just checked all my solenoids (assuming those were voltage tests)... and pressure tested my hoses. Thought it might be my Apexi BOV leaking or not closing off. Put a known good stock BOV back on... problem still persisted. After some more testing decided to replace my rebuilt turbos with a pair of new 99Jpec twins (which I might add kick ***...when they kick IN). Just drove the car home yesterday... after a break in period... put it to the test... SAME FREAKING PROBLEM!!!! ARRRRG!!!

POSSIBLE THOUGHTS ON THE ISSUE:

From a non-mechanics point of view and my limited knowledge of the car I have thought about a few things that might be the issue... but I am REALLY hoping someone out there has gone through this and can give me an answer straight up. I honestly think KDR is going through the logical steps to try to trouble shoot this... and there are just SO many parts that could be the cause... but I was thinking:

Something has got to be not fully closing off, or sealing... or springing back or open.... until after a few seconds when either it cools down or settles back to where it is supposed to be. Would a wastegate do this or maybe it's that second BOV no one ever touches, or a solenoid that tests out fine... but ceases to work in conjunction with another part. Hell.. I just don't really know. All I know is it makes the car less fun to drive... and impossible to do anything like drag race.

Well... if you got this far... maybe you are as intriqued, or confused as I am. ANYONE HAVE ANY THOUGHTS??

Let's put our heads together on this one. It's going to be some stupid little solution in the end, I know it.

Thanks,
Stephen

Dougie_fresh_007

how bad does the change in engine sound appear, do u have ne exhuast upgrades so the exhaust it louder and it gets noticably quieter?

fstfwd

iTrader: (1)

I have a Tanabi exhaust... a downpipe... and only a precat. The pitch is pretty low to begin with... but it gets even lower... almost like the sound it would make normally if my rpms were too low for the gear I am in.

As I push the gas further in... as if to "force" the turbos to start spooling up... the sound just gets little louder... the rpms don't get much higher, so I am forced to down shift... its just completely unresponsive - i can basically only maintain my speed until "whatever" does what it is supposed to and I get my turbos back. It would almost seem that as a result of what ever is happening I am getting NO forced induction... and relying completely on the engine at that point.

Dougie_fresh_007

hmm sounds like this problem i was having,.... and i still havent figured it out, im guessin its a vaccum tube but i cant be for sure.... tell me if ya have any luck

saxyman990

Part of it is completely normal. The system switches over from the primary to secondary at around 4500 RPM. Once it transitions, it will not switch back to primary until you drop the rpms below 3000. Even then it usually requires you to stay off the gas for a bit before it switches back to primary.

This is what you are experiencing. Once you hit the transition point (4300 RPM), the system switches to secondary boost. If you let off gas, or upshift, then the system will stay in secondary mode. If you are below 4500 RPM when you get back on the gas, then the turbos don't spool too well, cause its like you are running them non-sequentially.

I had a similar problem for a little while, but I knew it wasn't quite right, because sometimes it wouldn't switch back to primary even if I brought the car to a complete stop. Many times, once I transitioned, it took a good 5 or 10 minutes before it was able to switch back. For me, this was because of two reasons: the first was a sticky Charge Contol Actuator, which didn't want to close after it opened (fixed that problem with a little lubrication). The second was a sticky Charge Control Solenoid (fixed it by replacing it).


The next time this happens to you, see if you can upshift or slow it down so that the RPMs drop below 3000. That should bring the car back to primary mode. But from what you describe, it seems that your system is operating normally.

turbobig

thats true thats true man thats the first real advice ive see n in this place good job.

Narfle

iTrader: (16)

BOV?
wastegate?
gone bad?
i have no clue
wish i could help
sorry

rx7speed811

downpipe AND precat??? damn you must have a crazy *** setup!

r71

iTrader: (3)

I had the same problem. I went around in circles trying to fix it and gave up. You'll have to check all your solenoids and check valves. I found that my turbo control solenoid would work when cold, but open when got hot. I replaced all the bad solenoids and check valves. Still didn't fix the prob. I said **** it and went non seq. I will stay non seq. Here's the kicker.

For some reason, I replaced all the check valves but one. That metal one coming out of the purge control solenoid. As I was ripping out my rats nest, I decided to blow on the metal piece of ****. What da you know. It was bad. I was soooo pissed.

If you want to perminatly fix your problem, go non seq. If not, check all your solenoide, hot and cold, and all check valves.

saxyman990

r71 brought up a few good points that I forgot to mention. Sometimes the solenoids will only malfunction at high temperatures. For this reason, when you test them, make sure to test them both at room temperature and hot. This was the problem that I had with mine. At room temp, it worked fine, but once it got hot, it did not want to switch.

I threw mine in a pot of boiling water to heat it up. Once it was hot, I took it out, dried it off, and tested it. An oven works well too. If in doubt, then replace it with one you know works, and see what happens

Just another point to consider.