Barwick

Ok I think I'll do that.. only I think I'll wait till I get a Manual Boost Controller.

KenA

Does your factory Boost gauge read 0 when you click the key on? FC3S Pro says that this is the BPS Self Check..

I am stuck at 4.5 psi and I have already tried replacing the BPS (with another one that might be bad) with no luck...

I am putting on a full 3 Inch (DP, No Cat, 2 Mufflers) this weekend and am awaiting to see the results..

Barwick

no.. it reads at like -20 when I click it to on. I think I need to rewire it.

KenA

That means either the BPS or the wiring is bad...Grrr

I'll probably do the same thing this weekend..

NZConvertible

You should have told us this ages ago! With power to the gauge (ignition on), it should read zero because there's only atmospheric pressure in the manifold. It's not a self-check as such, it's just what it should read with the engine not running, just like a mechanical gauge does. You need to replace that sensor ASAP.
Like I said above, it's much more likely it's the sensor, not the wiring!

Piranha

I have a question... mine goes a little less than 0. I just figured it was because I am above sea level. but... I do hit fuel cut right before 9 Psi, so I assume my sensor is right.

Barwick

I've checked the readouts AT the sensor already. They're ok. Actually just about perfect.

I still have to check them at the ECU though.

KenA

Swapped in yet another BPS with not much difference in boost...

Each one I have swapped in and clicked the Key on and gotten different readings on the factory boost guage...The first one was -20, the second was-15 or so and the third was -10...Maybe If I keep going I can get to 0

This leads me to believe that the wiring is ok if I keep getting different readings...

Anyone price a Boost pressure sensor from a Mazda Dealership?..I think I keep buying bad ones..

This weekend I went to a full 3 Inch exhaust (Downpipe, Resonator, muffler) and still am at only about 5 lbs...


And yes, 5 psi on a full 3 inch exhaust does really SUCK...

vosko

iTrader: (4)

i'm hitting 7psi on my TII. it freaking MOVES!!! i'm happy i fixed mine but i'm gonna install my greddy TVVC and see if i can get it to run 11psi

KenA

How did you fix it?..Did you have the same problem I am having??

vosko

iTrader: (4)

here is what happened to me. i had a first jspec that was blown coolant seal that one hit 14-15 psi. this new one hits low boost but maybe i put the boost solenoid on backwards. it doesn't matter i'm gonna run the manual boost controller anyway its more reliable

hypntyz7

low boost = bad turbo gaskets. IM telling you all...

KenA

How does that explain my Factory boost gauge reading below 0 with the ignition hot??

Huh??

My problem is electrical..Just gotta figgur it out

hypntyz7

mine reads a bit below 0 with the switch on too. keep in mind that gage can be a bit off calibration, just like teh temp, gas or whatever. my gas gage doesnt go all teh way to F when I fill it up, but it will drop below E before it runs out.

**** that gage, check voltages. Even then, a bit of voltage variance isnt out of the ordinary, adn that's not to say its what's causing your car not to boost.

Think about it...the turbo is purely mechanical. IF the throttle is open, it should spool to full boost. IF it doesnt, there is a physical reason that it doesnt. This is provided your engine runs fine otherwise.

I just fixed a car that did the same thing...full exhaust and only hit 5-6psi. Put in new turbo gaskets(half of one was gone) and he hits 8 regularly, or more. IF air is leaking out before it can drive the turbo, do you think it will make it less efficient?

vosko

iTrader: (4)

i'm not taking this turbo off unless its blown just to check the gaskets

hypntyz7

you dont have to...use some atf and observe the smoke leakage(remove stock fan first).

vosko

iTrader: (4)

i get no smoke anywhere now that i fixed my little issue i caused. it helps when your car isn't a smoke machine

KenA

Hyp,
Now that you mention it, I have been looking at this pretty narrow mindedly...Which gaskets fail typically?...Manifold to turbo?...

I have been going off of what others have said "If your gauge is not at 0, your bps is putting the ecu in limp mode"

But the ECU cannot limit boost pressure...It is mechanical..

I just dont want to tear into the turbo assembly and find out that I had a bad damn wire...you know

How difficult is the R&R for the turbo gaskets anyway??

hypntyz7

lol...

hypntyz7

yes, it is fairly thin adn always fails. the other one is thicker, the block to manifold, and rarely leaks. Another common thing is for the fasteners to have broken or come loose or off totally; the last one I did was missing 2 bolts entirely, and 6 were loose, out of 8. THis has the same effect as a bad gaskets if air leaks out.



technically, no. But, also, if you have a bad enough engine problem, boost can be limited too...if the engine doesnt run right for whatever reason, it cane move air efficiently enough to drive the turbo consistently. if you have no running problems though, and are just not hitting full boost, I would lean towards an intake/exhaust restriction(not your case I guess) or a bad gaskets decreasing teh turbo's efficiency.

youll need a couple of universal elbows and plenty of ratchet extensions, but it could be done in 3 hours if you applied yourself and had proper work area. Otherwise, allow about 6, especially if the engine is still stock. You have to remove the acv, exhaust sheilding, and precat/downpipe to get it off.

KenA

Looks like I found my weekend project...

Should I go to Mazda for the Gaskets?...Or would Pep Boys have the Fel-Pro's I need?

My car is a pretty low milage T2 (72k), but runs VERY strong..Compression is even on both rotors and it idles like a Caddillac..I bought the car with this problem...

Maybe that is what has helped it last so long...A built in boost controller, so to speak...

Gecko_7

I dunno if this will help but, My car use to do the same thing but I had a apexi intake and as soon as i built my cold air box it went past 5psi of boost.

It use to only boost to 5 and now it boost to 7-8psi

hypntyz7

Theyre not paper or cork gaskets...theyre metal gaskets like a headgasket. Still, the exhaust pushed through them. Definitely a mazda or aftermarket supplier part; pepboys or the like will have never heard of this gasket.

Wargasm

Ken,
While you're in there, check the turbo to be sure that nobody did something lame like clipping the exhaust fan. Once you've got the turbo off, it's not hard to port the wastegate too, which is something that I highly recommend if you haven't done it yet.

Brian

The Ace

As I have recently discovered (to both my dismay and huge enjoyment ) loss of boost can be attributed to various facts/problems:

1) Clogged exhaust
2) Crappy intake/malfuctioning AFM
3) Leaking gaskets on manifold and turbo
4) Cracked manifold and/or turbo housing
5) More than enough play on the axle
6) Partially clipped turbines wheels

However, if your boost gauge does not move to '0' (or close), then you have a) bad sensor, or b) bad wiring, or c) bad gauge. Get a mechanical aftermarket and make sure