Another one of those BOOST PROBLEM threads
 

ok so u guys have probably answered this question before. i did some "light searchin" through like 3 pages and didnt really find an answer. any ways let me tell u the problem. i just installed a boost and temp guage and just like any one else after i finished i went to test them out. well my boost readings werent very pleasing. my boost pattern is about 9-5-6.

now i read a few threads and i saw that a few problems could be boost leak, check valves, vacum hoses, y pipe... and so on. i dont think its a boost leak cause my primary is almost at 10 psi. i have a 99 spec y pipe so i dont think it is that either. i am unsure if it is my chech valves or vacum hoses cause its late rite now and i dont really know how to check the check valves. any ways do u guys have any other suggestions and or links to write ups so i can try a few things out? it would be greatly appreciated!!! thanx

also my mods are in my sig and i thought that with these mods i should be around 11-12 psi.

What ECU are you using to control these mods?

Test/check/or replace the check valve between the pressure chamber and y-pipe. A crude test is to blow through them, but a real test involves a vacuum/pressure pump like a Mityvac.

Dave

im still on the stock ecu...

dgeesaman- where is the pressure chamber? do u have a pic to show me maybe? and when i blow thru it what should i be lokin for?
thanx

oh one more thing is 10-12 inhg vacum normal when at idle?

The pressure chamber is just behind the cross-over pipe from the turbos and just in front of the UIM. It is black and ~4-5 in long, 3" wide and has 2 nipples on its left end.

11-12 in Hg is quite low unless you have had the engine ported. 15-16 in Hg is the low side of normal. 18-20 is really good.

hey thanks so i should look for some kind of check valve there? and my engine isnt ported, so what does that mean is that low a a vacum bad???

ok so i found the check valve, its green right? so when i blow tru it what am i looking for? thanx

It should allow pressurized air to flow into the chamber, and prevent it from flowing back out. So if you blow thru it, air would flow toward the pressure chamber, but not in the opposite direction.

ok thanks!!! and about my vacum being so low is that a problem?

^bump^

Yes. IMO, vacuum should be above ~14 in Hg at 750 RPM with stock ports. If it is not, you may have some stuck side seals (see carbon lock, or similar), or other rotor seal problem.

If the seals are stuck, there are methods to unstick them (ingesting water or other decarbonizing agents into the intake manifold) without disassembly. If they are damaged, it will required a bebuild.

well i noticed that once the car is warmed up it is just at 15 in hg. i do have 107k mi and i think it is the stock engine... im gonna check the check valve asap.

ok so i blew trough it and it did what its suppose to, it will allow me to blow air to the pressure chamber but not in the opposite direction... any other suggestions???

Basics: The stock boost-control system is open-loop. That means that the ECU uses a pre-programmed map to control boost. It does not use the actual boost value to adjust the boost. That means weather, engine state of health, etc will affect the boost.

Next: Troubleshooting guide: http://www.fd3s.net/boost_problems.html

Finally: If there is nothing wrong with the turbos or their control system, you may be suffering from a somewhat worn-out engine, which, as I stated above, will result in lower boost levels.

You could possibly use a boost contoller to raise the boost back up to normal levels, but I don't think that is necessarily a good idea considering the age and possible weakened condition of your engine.

ya i see what ur sayin, and im not gonna buy a bc to raise the boost. i aready thought that w/ my current mods i should already be at 11-12 psi. oh and i tryed the link and it doesnt work for me.

ok nvr mind u changed the link lol ;)

Yeah - I found that it didn't work for me, either. :)

so w/ ur experiance what do u believe the problem to be?

this is from the link you gave me and it sounds like exactly wah happens to me! now all i need to know is where are the Wastegate and Turbo Pre-Control Solenoids?

"Wastegate and Turbo Pre-Control Solenoids

If you are getting a solid 6 psi from 4,500 RPM up, Check the electrical connections to these two solenoids, as they can get mixed up while working on the engine. From the front of the car, the right hand solenoid and the electrical connector of the engine electrical harness have a painted white dot, these two go together. Note that over time these painted white dots tend to dissapear."

This is, of course, an only slightly educated guess, since we can't for sure say that something specific is not wrong (that's why going through the troubleshooting procedures would be useful), but...

Since the boost is low all the way through the rpm range, I think that it's possible that the low vacuum at idle (a compression test would be more definitive) is a clue that your engine is fairly worn, and that could be the cause of the somewhat low boost.

Sorry to be so vague, but it's really hard to diagnose without more info.

IIRC, these are the 2 solenoids just in front of and below the UIM on the RH side.

ok so should i try an swich them?

Yes - won't hurt anything to try. Switch the electrical connectors, if that wasn't obvious.

ok ill go do that and on another note while i was lookin at the solenoids and noticed a vacum hard line that wasnt conected to any thing. look at the pics.

https://www.rx7club.com/attachment.p...d=159981&stc=1
https://www.rx7club.com/attachment.p...d=159982&stc=1