jeffrored92

Seems not many people were actually viewing my last post, I must have used a non-appealing title.

I am still troubleshooting my boost problem.

ANYway I was testing my air bypass valve (or blow off valve) and it seemed to be leaking. According to http://www.autosportracetech.com/RX-...leshooting.htm the air bypass valve should hold 15psi on the turbo side with NO connection to the vacuum hose nipple. According to https://www.rx7club.com/showthread.p...light=ABV+leak it is normal for the air bypass valve to leak some boost with no connection to the vacuum hose nipple.

Can someome please clarify this information for me? I looked in the FSM but it doesn't say anything other than to verify that the valve will pass air with vacuum applied to the vac hose nipple.

In my long quest for the holy grail of 10psi boost, I must leave no stone unturned............

Speed of light

iTrader: (8)

I noticed this characteristic on the stock BOV's too. I ran a few bench tests using about 10 - 20 PSI on the bov inlets while I modulated the diaphrams with Negative and Positive pressure, thus simulating operating conditions. What I found is that it is normal for the bov's to leak slightly until a positive (boost) pressure of a few pounds (about 2 to 4# if I remember correctly) is applied to the control port, at which point there is no leakage. The small amount of leakage present with no connection to the control port seems to be inconsequential, so I consider this to be normal operation.

Hope this helps.

jeffrored92

Thanks!!

Now I can get back to searching for a leak, or faulty solenoid, actuator or check valve. I'm taking everybody's word that finding the problem is worth it when the turbos are back up and running properly!

Larz

Change the vaccum lines and replace the check valves while you do it. Less headaches later.

alberto_mg

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/abv-operation-will-vent-if-386556/ haha, I think you sucked on the nipple too hard

What exactly is your boost pattern and the problem you are trying to resolve? Post a link to that post if you can find it. I couldn't figure out which one it was...

DaleClark

iTrader: (55)

Took me a second - you have to think about it.

The blowoff valve is designed to release pressure when there's a vacuum on the nipple and pressure on the body of the valve. So, when you're on throttle and producing boost, there will be boost on both the nipple and on the valve body. When the throttle snaps shut, there's vacuum in the intake manifold and pressure on the valve body, and the valve opens and vents boost.

So, a proper test as to whether or not it leaks would be putting pressure on both the nipple and the valve body.

The stock BOV is pretty hardy, BTW. You'll have to keep diggin' - be patient and keep turning those stones over!

Dale

jeffrored92

Oh I see...............well I won't do that again then

Boost pattern is still about 7.5 - 5 - 5 maybe dropping off towards 4 as I approach redline. Dumping the accelerator my boost jumps up to 7.5psi real quick, and the drop to 5psi quite sharp around 4500 rpm. Older thread where I was talking about it is https://www.rx7club.com/showthread.p...6&page=1&pp=15

I've replaced the 1" hose to the ABV, checked for pills (they are there and the right size in the right line) and inspected the IC piping & couplers. So far no obvious leaks. I still need to completely remove the y-pipe coupler, I'm having trouble getting at the lower clamp.

Secondary throttle valve moves smoothly with the car off, so I don't think it's getting stuck. I need to learn more about how that works though.

The 1" hose from y-pipe to CRV is baked hard and loose (it rotates easily) at the y-pipe. Will replace that soon but it's not related to my primary loss of boost seeing as the CRV itself is open anyway during Primary Only Boost.

I think that's all so far. Plenty of testing still to be done. I'd like to find the problem first rather than just jump and just begin a vac hose job - I want to know what's causing the problem

Hypothetically speaking, if I was getting 7.5psi boost on primary, with no boost leaks, and the pills are in the lines to the pre-control & wastegate actuators, I'd begin to think something's not right with the pre-control / wastegate solenoids, or their electrical connections. That's where I'm going to focus next

jeffrored92

And Alberto_MG

Have recently bought some new jackstands, planning a tranny oil change in the near future so I'll pop the exhaust and check the cat at the same time.

(I remember you were telling me to check to see if it's clogged, I liked your shower drain analogy champ )

alberto_mg

that link was informative. i suspect it might not be the cat, but give it a look. when my cat was clogged, i was able to build 10psi on the primary and it decreased as more air was trying to be pumped through at higher rpms.

have you checked the 4 vac lines under the Y pipe? those control pre-spool and the transition to the 2nd turbo. you might also try and swap the electrical connectors to those 2 solenoids and see if does anything. someone more knowledgable than I once mentioned that if you swap those two connections accidentally your boost will be around 7psi and inconsistent betw the primary and secondary. sorry but i'm forgetting the exact details, but try it if you like.

Speed of light

iTrader: (8)

Hey, I had an exhaust leak at the turbo that produced the kind boost pattern you describe and also produced a weird flapping noise as the prespool valve opened.

It's easy to check--you can do it from under the car very easily without taking anything off or apart. First remove the small heat shield around the bottom portion of the turbos, (2) 10mm nuts if if recall correctly, and then check the 4 large bolts that go through the side cover (where the prospool valve is) to see that they are tight. An exhaust leak at this cover will allow the primary to spool normally, but the secondary will not transition or function correctly. It limited my sec boost to about 6 psi once a couple of those bolts started backing out!!!

jeffrored92

I've checked the vac line from the primary compressor to the pre-control actuator, it's fine and has the pill inside it. Haven't checked any of the vac hoses for the turbo control actuator yet, I need to get under the car I think to get to that one?

I've read that swapping the electrical connections for the pre-control / wastegate solenoids can cause issues so I'll definately be looking at that when I'm checking those two solenoids out.

I don't think it's the cat either but I'm going to check anyway, just because I'm interested

jeffrored92

[QUOTE=Speed of light]
It's easy to check--you can do it from under the car very easily without taking anything off or apart. First remove the small heat shield [QUOTE]

Without taking anything off, except the heat shield, I see

Haha sorry mate couldn't resist!

Cheers Speedy I'll be checkin that one out as well