My car is a 92 (same as the US 93) FD. The only mods are a HKS BOV, extra cold air inlets on the stock K&N filter equiped air box, apexi avcr boost controller, and a Blitz cat-back system. The turbos were recently replaced with 98 fd turbos due to the orginal turbos having poor seals



I bought the FD stock apart from the HKS bov. I attached a boost gauge to find it is only running 6.5psi, drops a little 4000rpm, and then back to 6.5psi. Also if I floor the car from cruise at any rpm above ~4000rpm I will only get 1-2psi.



I decided to put on an avcr boost controller to eradicate any possible problems with the factory Wastegate and Turbo Pre-Control Solenoids. At the same time I installed a cat-back system. On 42% duty cycle I will make a best of 8.5psi (sometimes), the boost should be higher from what I have heard from others on this forum running the avcr. The problem with lack of boost when flooring it from 4000rpm still remains. This particular problem points to maybe the vacuum chamber leaking, however I have checked both of these and they keep there pressures. Maybe the Turbo Control Actuator??? I have also checked for any splits in the rubber intake hoses.



As for the low boost problem, maybe exhaust restriction (still have standard DP, precat, and main cat), but i would expect this to only effect the boost in the higher rev range.



i disconnected the vacuum hoses from the pre-control and wastegate solenoid and blocked them off. rechecked pressure and vacuum chamber. and checked most of the check valves i could see. i was hoping to pin down a few problem areas before i decided to replace all the vacuum hoses. i wanted to check the turbo control solenoid and vacuum fittings, but could find it. i assume i will need to take the UIM off before hand.



any thoughts on this problem? anyone have similar problems with a solution?



thanks

Felix



i have searched this and the other forums with not much luck

First, take that boost controller out of your car. Trying to force feed boost won't help the root of your problem. Second, how are you coming up with 42% duty cycle? I assume you're talking about your injectors.. So are you getting an additional 1-2 psi above what you're seeing on your gauge(6.5) or are you really on getting 1-2 psi?. Pull your cats and see if the bricks have broken apart.

He means 42% wastegate duty cycle - the wastegate is a solenoid and the AVC-R and ProfecB Spec-II adjust as a matter of percent of mechanical maximum. I.E. 0% is the wastegate's natural spring rate in PSI (7-8) and 100% is the turbo's mechanical limits (~19PSI).



Here's a simple test - what happens when you are at WOT, then rapidly release and reapply the throttle? You may want to lower your AVC-R to 10% before trying this. If the boost comes online after reapplying, then you have a bad check valve.

that's correct Sinful7, 42% duty cycle for the avcr solenoid not injectors https://www.nopistons.com/forums/pub...DIR#>/wink.png



i have the avcr turned off currently and is running aprox 6-7psi (standard WG spring pressure) for the reason 88gt has given; no point pushing the turbos while something is wrong...



i have since checked operation of the 2 solenoids which activate the turbo control actuator. both solenoids should activate above 4500rpm, where 1 should apply boost and the other vacuum to activate the TCA. what i have found from taping a boost gauge into both lines is only the boost solenoid seems to be working. and yes the vacuum chamber holds vacuum.



for any other having similar problems i suggest you do the following test



TCA testing:

1. Pull off strut brace and pressure chamber (can leave hoses attatched)

2. You should see four 4mm metal hard hoses that come up. Two of them go to the solenoids mounted on the front of the UIM, forget them (wastegate and turbo pre-control solenoids). The other pair should have rubber hoses that connect them to the rat's nest. You need to tee into these.

3. One at a time tee into the hoses and connect a boost gauge. The pressure side (forward hose IIRC) should sit at zero until you go past 4500. Then it should kick over to 10psi. The vacuum should kick over to at least 15mmHg.