Low Boost Pressures

[Speeding]

I've had my MSP for about a year, just starting to put work into it. Car has no stutter, idle, or other issues.

Installed an Autometer Autolite II boost gauge. I installed the vacuum T inline between the IM and the brake booster, before the one way check valve.

Car holds a steady 22-24 pounds of vacuum.


NOW the issue I am having is the car only boosts to about 4-4.5 lbs when under load.

I was under the assumption the car should push slightly higher numbers than that with a factory set-up.


I am about to install my FMIC, hard pipes, and BOV so I want to make sure everything is running correctly before I do everything.

 

[destineal]

Boost leak?

 

[BRIAN_MP5T]

No I believe it's easier than that.

the car should read a dead 20 vac, because its lower, I am leaning towards saying that the autometer gague might not be calibrated that well or was damaged somehow.

 

[destineal]

definitely possible.

 

[BOOSTR]

It all depends on your altitude and the weather at the time as to what your idle vac pressure will be. Some gauges do read differently. 20-22 is normal but those SW gauges read lower. Not all MSP's came from the factory/dealer with a uniform boost pressure. The original WGA is adjustable and the stock range reported back in the day from MSP owners was as low as 4 and as high as 8. The later being more rare and lower being more common. Mine is 6.9.

What's the bost reading when you punch it in 3rd gear and where does it hold at and how many miles on your engine?

 

[Speeding]

Destineal: I originally though I might have a boost leak but everywhere I can check is tight and sealed well. I haven't smoked it or done a water test on any of the fittings though.

Brian: I also thought that because I have seen a lot of people get junk gauges that don't read accurately or are out of cali. It reads perfect 0 when the car is off, and a steady 22 when sitting at idle. It holds very consistent vacuum and boost so I thought that would rule out any vacuum or boost leaks.

Boostr: The car has 90K miles on it. I have been running around with the gauge on for the last couple days, the weather has changed a good deal, boost pressure hasn't. Third gear pull shows 4.5 pounds of boost. And it is very consistent, it doesn't waver off or fluctuate. Which I figured rules out any issue with the BPV.

You mentioned being able to adjust the factory WG? Is that something that can be done easily?

Let me know anything else I might be able to tell you guys to help.

 

[speedpx]

I say turbo wastegate stucked open. That happend to me twice. First time I replaced the turbo second time I replaced the turbine housing. Check this out

http://www.mazdas247.com/forum/show...ound-problem&highlight=no+boost+found+problem

 

[Speeding]

I say turbo wastegate stucked open. That happend to me twice. First time I replaced the turbo second time I replaced the turbine housing. Check this out

http://www.mazdas247.com/forum/show...ound-problem&highlight=no+boost+found+problem

Yeah I read through that thread and kind of ruled it out, or at least I wanted to rule it out because I don't want that to be the problem...

The thing is the car makes boost and holds it very consistently, it just doesn't make a lot of boost. Or at least not as much as I was expecting when I got a gauge on it.

 

[Spiced MSP]

I can vouch for the different gauges having different readings as well. My first boost gauge showed a constant 20inHg when idling and like 23 when coasting to a stop in gear. Then, when I switched to an AEM digital boost gauge, my idle was a constant 22inHg and 26 when coasting in gear. Even after swapping in a bigger turbo, numbers are still the same. Double check your couplers and clamps. What may seem tight could show a leak with a proper test

 

[jeffmsp]

for all you know the previous owner spent 10 minutes adjusting the stock wastegate by extending the arm so that it opens earlier after reading about people blowing their motor, or even if they only had 89 gas available locally and wanted to keep boost pressure well on the safe side of things.

and btw 22-23 vac is the same as the readings i had back when I had a stock motor. Had many different gauges over the years as i have had the car since new and all read the same.

Maybe Brians 20vac numbers are due to his built motor? Either way it seems lower than I ever had on the FS-DE. using autometer/blitz ebc/sunpro gauges both analog and digital all read 22-23vac at idle when fully warmed.

 

[Speeding]

for all you know the previous owner spent 10 minutes adjusting the stock wastegate by extending the arm so that it opens earlier after reading about people blowing their motor, or even if they only had 89 gas available locally and wanted to keep boost pressure well on the safe side of things.

and btw 22-23 vac is the same as the readings i had back when I had a stock motor. Had many different gauges over the years as i have had the car since new and all read the same.

Maybe Brians 20vac numbers are due to his built motor? Either way it seems lower than I ever had on the FS-DE. using autometer/blitz ebc/sunpro gauges both analog and digital all read 22-23vac at idle when fully warmed.

Okay assuming there are no other underlying issues, what are the steps I need to take to reverse the change to my WG arm, and adjust it to build more boost?