Aristo

iTrader: (8)

Since my turbo rebuild I have been seeing a boost pattern of 12-5-12 (before with the same setup I had 12-12-12). The 5psi comes on for just about an eye blink at transition, and quickly builds up to the final 12 psi. I am convinced this is not a turbo control problem, since I checked the vacuum and pressure sides of the TCA and found normal values of -15 mm Hg vacuum and 9 psi pressure. I am also certain it's not the prespool actuator (I pumped this with a hand pump), and made sure the prespool door was adjusted properly. So, I did the following experiment:


1. Took out the pills from the prespool (so it should open very early). This gave me a pattern of 7-5-12.

2. Vented the line leaving the prespool actuator, so that it never opens: This gives me a 13-5-12 pattern.

So from these 2 extreme cases, I can see that the secondary is getting the equivalent of the energy difference between 13 and 7 psi prior to transition. I should think this would be enough to prespool it. Im beginning to worry about the only things I havent looked at, the CRV and CCV.

Does anybody have any idea what might be going on? Please throw me a bone on this one, as I'm ready to start pulling my hair out.

spooledUP7

I wish I could help. I had the very same issue (minus the rebuilt turbos) and I tried to fix it with months of manual boost settings.
The first thing I noticed, as you did too, the precontrol affects the primary significantly.
I finally pulled my turbos out and noticed that my secondary turbo manifold was very cracked, especially at the wall separating the precontrol door. It had about 1/8 gap at its widest point, and I think that this played a big roll in the low transition. I figure it caused irregular flow which may have slowed the turbine. I also had what I thought was the worst looking primary turbo in the history of turbos. There wasn't much left of it. I figure this also had something to do with low transition.

I doubt your manifolds are as bad as mine, but there is a chance.

I also thought that I might have had a slow TCA, but I'm not sure about that anymore. I'm going non sequential.

Aristo

iTrader: (8)

Thanks Spooledup. I have been working on this problem for a month now, and am nearly on the verge of just living with it. My turbo manifolds were supposedly in very good condition..they have 70k miles on them. There is one very odd twist in all of this: When I take the pill out of the precontrol, and get 7-5-12, I get a boost spike to 13-14 psi AFTER he drop to 5! That is, it drops to five, shoots up to 13-14 then goes back to 12...almost like I am 'overspooling' in a way. I get the worst of both worlds, a low transition and a boost spike!