How much boost with these mods?
 

How much boost should I be seeing with type of mods I have?

Is your boost gauge not hooked up or are you getting a different amount of boost than you think you should?

I'm seeing 12 psi in second and 15 psi in third from my boost guage. Stock I'm supposed to see around 5-5.5 psi right? With the DP and silencer according to RB website I should see an additional 1-2 psi. That should be around 7.5-8 psi. right? I have a POS autometer guage but I never heard of them being off by 7 psi. I also stripped one of the nuts that hold the DP to the turbo. Anyone happen to know what diameter and pitch those nuts are?

So you have the stock catback then? As I understand it you should see around 9-10psi with Intake/DP/MP.

Yeah I'm still running the stock catback system for the time being.

Anyone have any ideas?

You're asking us what boost you should be running or what is the max you can run?&nbsp The Walbro will keep the engine happy up to 15psi as long as it gets full voltage!



-Ted

my TII without upgraded ecu with 3" dp and 3" mp hit 7.5psi spiked to 10psi a few times but this is on a 89 TII. 12-15psi sounds normal for a 87 TII

I've got a 87TurboII with the 2.5 down pipe and presilencer from Mazdatrix and everything stock from there back. I hit fuel cut on cool days (my guess is 60 degrees and below) which should be 8.6 psi. Today I can't hit fuel cut if I tried.Its in the 80's. I have a Autometer boost gauge. At one time it was showing me hitting 10psi and I was pleased as punch til I started wondering why I had not hit fuel cut. Determined the Auto meter was off 2 to 2and one half. When I hit fuel cut I peg the factory gauge, but then again, with the key to ON, it isn't hitting the zero mark. Its three quarters of the way b/t -20 and zero. The volt meter that is picking the voltage off the pressure sensor says 3.6 something volts when I hit fuel cut on cold days. So the real reason you wrote is to find out what the nut size is on the back of the turbo???? I measure the nut being a M10...1.5. Pepboys should have one or two. Or did you mean the stud that screws in the manifold???? One of three?

that seems pretty high with a stock cat back and stock TID... you might have some wastegate problems. try running a new vac line from the turbo to the wastegate.

I wrote because I was under the impression that with the mods I have I should be around 8-10 psi. But I'm at 15 psi. I don't want to blow my engine. The nut I'm talking about are the 3 that hold the DP to the back of the turbo.


Scott: I'll take a look at the wastegate tomorrow. I'll let you know if I find anything.

Ted: 15 psi with the stock ecu and walbro pump is ok? I thought a SAFC or an upgraded ecu and a walbro was needed if you wanted to push 15 psi safely.

I believe the reason youre seeing such high boost is from running a better flowing exhaust and a stock wastegate with no fuel mods other than your walbro. In order to stop this youll need some form of fuel controller or a bigger wastegate...if im wrong, someone tell me.

I have a 3" open exhaust +intake+2.5" custom TID,
my max boost is only 0.35 bar, what happen to my car???:confused:
with the boost contoller on , I can run 0.6 or higher...

I have racing beat turbo back exhaust and a bonez intake and a walbro and I am hitting 11-12psi in third I have 91'

Camel Joe.....I seem to have the same downpipe that you do and the presilencer. The only difference is the K AND N filter. Plus I had the turbo rebuilt by MAJESTIC in Waco, Texas...When they did the rebuild he did say something about some upgrade, but that went in one ear and out the other. Possibly they opened the wastegate hole. Anyway I get what Mazdatrix advertized, about 8 to 9 psi on a cold day but no more than about 8 on a eighty degree day. Autometer gauge is not a bit accurate. I must have bought the only one that they ever made defective. The nut is as described in my above post. Pepboys.

that's normal :)

Cameljoe....... I am confused...again. On another post I see where you talk about how the downpipe flange is busted and the way I understand it, the downpipe isn't connected to the rest of your exaust system. Is this a right assumption?????? If so, I can understand how you are managing to boost so much higher than my car. Surely I misread the other post.

The stock DP (precat) has a flange on both ends. Well the rear flange that you screw 2 bolt through to attach it to the flange of that straight pipe that bolts to the main cat? Well the welds on the flange broke off from the DP (precat). So basically i was driving with an open exhaust. With the exhaust like that I would boost to 8 psi in all gears. This was during this last winter. Just last month my boost has gone up to 15 psi with the same broken/open exhaust. Now I have the RB 2.5" cat replacement pipe I'm still boosting 15 psi. I think my I have a problem with my wastegate. The wastegate has a spring that is rated at a certain psi and also has a vacuum line that helps compress the spring. Am I right on this? Maybe I'm not getting vacuum to the wastegate and I'm just using the spring which is why I'm boosting so much higher?

the wastegate doesn't have a spring because its internal on stock turbos. external wastegates you can change the spring for different boost pressure.

Right and wrong...
The spring is not built *into* the turbo itself, but the wastegate actuator *attached* to the turbo has a spring.



-Ted

ooops ;) my wastegater actuator is adjustable..... i need to get the garrett turbo rebuilt cheap ;)

you might want to be careful. I have bascially the same mods but if you don't have upgraded injectors (720cc), then you could be leaning out the engine when you boost too high. I'm sure I don't have to tell you when you lean it out. But somewhere between 9-13psi sounds right. You may want to get a boost controller.