I just finished a vacuum hose/fuel line replacement, got everything back on the car, started it up. Ran fine, idled a little high at first, but after i drove it some it settled back down.

My problem is, the small turbo isnt making boost. Im not getting any real power until ~3500 rpm, thats when the big turbo kicks in i hear.

I tried switching the turbo control solenoid plugs, because i read that that is often the problem, but no dice. Anyone have any quick ideas? I really dont wanna rip it all apart again... Anyway, thanks guys. Youve all been a big help.

 

bump cause im lost as hell....

 

The small turbo needs to spool up before the secondary turbo comes on line. If the first one doesn't work, the second won't either. I'm sure you forgot a hose or something especially if it worked before.

Work case senerio go poor man's non seq till you have some real time to figure it all out.

x...

 

What would cause them to start bilding boost at 3500rpm instead of the usual ~2k?

 

That's not entirely true.

If the Charge Control is open, it will let the primary join the secondary while the secondary is venting through the CRV. Thus, there will be little to no primary boost and then you'll have boost about 3800-4000 rpms when the CRV closes.

 

That would mean it would make a hissing sound of released boost while i was under 3500rpm or so...the vented boost from the primary turbo. I dont hear that sound...unless its real quiet (bov/crv is open to atmosphere).


EDIT: nevermind...if the primary joined the secondary and vented through crv until crv closed, then it would sound almost the same as normal operation...maybe just slightly louder due to more being vented out the crv....so charge control is a possiblity.

Guess that means Ill have to rip it all apart again lol. Damn. But before I do that...is there a common point of failure in that part of the system? Or is it just a tossup (could be anything).

 

There is a test you can do:

http://www.autosportracetech.com/RX-...leshooting.htm

A simple test for the Charge Control Actuator is to start the engine and let it idle, the actuator rod will be pulled in. Stop the engine and remove the hose from Chamber A and the actuator rod will be out.

Also:

Check vacuum chamber's storage ability with engine off

* Pull off vacuum hose at Charge Relief Actuator
* Should hear air entering hose vacuum, re-attach hose
* Start engine - briefly accelerate engine to WOT in neutral again
* Turn engine off - KOKO 6 TIMES
* Watch Charge Control Actuator work each time
* Watch Turbo Control Actuator work each time, (need to crawl under the car to see this one)

This is just stuff copied from the troubleshooting link above.

 

Thanks Mahjik, Ill try that out when its light tomorrow....too dark to do it at this point in time.

 

i had the same problem, what happened is that i did not put the boost pills back in when i changed my vacum hoses.

 

The transition point for the secondary turbo is ~4,500RPM. Both turbos are the same size; they are both Hitachi HT12 turbos with 51mm turbines and 57mm compressors. Please describe your boost pattern to us. What boost do you get at 3,000RPM? What boost do you get at 3,500RPM?

 

Yes, the transition is at 4500 rpms. However, the CRV closes before that to build boost (between 3800-4000 rpms).

 

I dont believe its the boost pills.... Ive only changed the vacuum hoses on the rats nest and all the areas around it so far. I havent changed any on the turbos themselves yet.

 

Mahjik Im building boost at around 3200rpm....it changes sometimes though. At times like if Im going down the freeway, it wont have any real power when I hit the throttle running at 2500-3500rpm, other times it will start building boost when I do. From a stop it doesnt build any at all until, as I said, 3200-3500rpm.

And I have no boost gauge yet. Just got the car a month ago, and took it all apart for the fuel line/vacuum hoses in the first week. Gauges are next.

 

Well, you need to get a boost gauge. You may be building boost earlier, but just not enough to feel it on "the butt dyno" as compared to when both the primary and secondary turbos are online after 4500 rpms.

 

An easy way I figured out to see if you have a vacuum leak is to unplug the blow off valve from the air box and if its venting a lot of air, like a blow dryer than one of your vacuum hoses is off.

 

I agree. Although you are building boost at low rpms, you will *not* feel it. The only way to truly tell if you have an odd boost problem is to diagnose it with a boost gauge. Don't even bother trying to diagnose something like this until you do get a boost gauge.