I installed an HKS gauge to that nipple on the UIM. WOT in 1st, 2nd and 3rd gear give me 5psi of boost. If Im cruising it and suddenly floor it, the boost rises for a second to 12psi and goes back down to 5psi. It stays like that all the way to redline. The rats nest vacuum hoses were replaced with silicone ones but the hoses with the pills on the turbos are still the stock lines.

Info on my car:
- less than 20k on Mazda reman
- HKS downpipe
- Blitz catback
- silicone hoses in RATS nest.
- HKS electronic boost gauge
- new stock air filter

Overall the car feels very strong but then again, Ive only driven this FD. For all I know, it could be running crappy. Any help is appreciated. Thanks

 

alright, I went out on some backroad and found out that my primary turbo is putting out 12psi. I think the transition is around 8psi. After 4,500 rpms the secondary goes down to a solid 5-6psi all the way to the buzzer.

Could it be a solenoid? Vacuum line? turbo itself?

 

mine was exactly like that too..
does this happen only when your engine is heat soaked. Or everytime you wot and you suspect no boost. If it's because of heat. then selnoid. (sticky valve)

 

It does it all the time. The first time I tried it, I left the car on to let it warm up to normal operating temp. Once it was fully warmed up, I took it for a spin and noticed the 5psi of boost. Last night it was nice and cold outside when I was on that backroad and I couldnt get anything above 5-6 psi after 4,500 rpms.

 

Try switching the Electrical plugs on the Wastegate/Pre-Turbo Control solenoid. It's the solenoid that has two elec. plugs and 4 vacuum hoses coming out, and is located in the front bottom, more to the passenger side, portion of the UIM.

I had the exact problem with low boost after transition, when I bought my FD. The problem was solved after the elec. connections on the solenoid were switched. Good luck.

 

lets say these solenoids are plugged in correctly, will they get messed up if I switch the connectors like areXseven says?

 

do you have a boost leak? have you tightened up the clamps? have you replaced the couplers with silicon couplers? Have you checked the solenoid status on the PowerFC?

I'm struggling with something similar. I'm starting to think it might be the wiring harness that is old and brittle and there is not enough voltage or impedance going through a wire to one of the solenoids. Everything else has checked out - solenoids, TCA, etc etc

How did this start? Did you do some work to the motor and then suddenly this happened? My problem started when I replaced the Fuel Pulsation Dampener. I think a wire on my 11 year old 120k mile brittle as glass wiring harness might have been squished in the process and is causing this.

 

I am going through the same problem right now - except my secondary boost is intermittent - indicating a sticky solenoid in my case.

Essentially it sounds like the second turbo is not coming on line - the primary turbo is not large enough to maintain boost at the upper RPMs and that's why you are only getting about 5 psi (and it probably drops to 3 by redline).

I dont think you have the precontrol/wastegate solenoids backwards - if this were the case then you would see about 7lbs. everywhere (if the wastegate got held open), but check it anyway - there are also white dots on one of the solenoids and the corresponding connector to help.

Beyond that, it's the standard debugging proceedure - check for crimped or loose hoses underneith the UIM (there is one hose that has a tendancy to get pinched when you reinstall the UIM.

Check to make sure that the actuator arms that actually move the valves on the turbo are still connected. I have seen them fall off before due to a failed retaining clip.

If all that looks good then get a spare boost gauge, some hose and some T fittings and begin tapping the appropriate lines that control the secondary turbo. have a friend sit in the car and watch the gauge while you take it out and make some runs. You may well have a sticky or failed solenoid.

Good luck,

-bill

 

I have a silicone coupler at the Y pipe. My clamps are tight and unfortunately, I dont have a PFC yet.

I dont know how this problem started since I just installed the boost gauge and I've had the car since december. I get a rock solid 5psi all the way till redline. No more, no less. My vacuum at idle is 18.5 in/HG.

My boost pattern looks like this: 12-8-5

Im leaning more towards the bad solenoid right now.

 

The connections cant really be backwards, The solenoid on the right should have a white dot on it and the plug that goes to it, This is a dumb question but do you have 2 boost setting on your boost controller?

 

I dont have a boost controller. When you say "the solenoid on the right" do you mean the passenger side one OR the right one looking at it from the front of the car (drivers side)?

 

time for a pic...

 

The right as in the drivers side, oops I thought I read boost controller in your mods list, sorry...

 

Just to clear things up a bit. The drivers side (letter I) one is supposed to have the connector with the white dot?

 

up we go

 

Yea drivers side letter I should have a white dot on the solenoid and the plug that goes to it should have a white dot also. Personally tho I dont think its that, I think you have a vacuum leak, But by all means check it out

 

I'll check the plugs tomorrow and post what I find. Thanks

 

I checked the solenoids and it turns out the plugs were switched! Talk about an easy fix. The car feels way better now. Now I have a small problem. When im at WOT, the boos starts dropping very close to redline. It would be at 12psi then drop down to about 7psi. What does this mean? Right now Im not really concerned about that too much since the power is there until just before I shift.

ps.
Thanks for the heads up on the solenoids.

 

Ok how about this , go non-sequantial .

Ok sorry for being a d*ck, its just a really nice feeling.

 

 

I'll give you a quick note on non-seq thought.

GTI 2003
Chip, intake, staright pipe exhaust. etc

me =P 93FD of DOOM
Non-seq 9psi of boost (still fooling with the manual boost controller)

spanked him good, and ive been in his car when he beats on G 35s and even an S4 once (stock) so I laughed my way back home =P.

Good LucK!

 

Glad to hear it worked.

 

check the couplers now. its weird that its bleeding off at high rpm.

 

I've read some posts caliming that its normal for boost to start declining towards redline.

I wouldnt have such problems, as Euro FDs come with 7k RPM redline

 

I've beat a G35 with my car before I fixed the boost problem on a cold night. Wasnt too hard. Im sure my car is atleast a high 13sec car since I was pulling a bit on my friends 14.0 second 1st gen before the boost problem was fixed. I personally dont see the point of going non-sequential at this time since the sequential system is doing what its supposed to. I'd rather wait and go single.