So the weather is really chilly here in Chicago. I know with colder weather boost goes up. But is it normal to spike 26 PSI?

It happens when I'm cruising in 5th gear flooring the pedal. It slowly rises to 26 PSI.

But when I go through the gears it sticks at a solid 20 PSI.

Can it be that my boost gauge isn't reading properly? I'm kind of scared because I'm on a conservative tune for 20 PSI. Seeing spike of 26 PSI on my boost gauge scares me.

I don't have anything to log my car with. Plus I don't have a A/F reader so I'm not certain how healthy my car is running at the moment.

BTW I run the AMS MBC with the soft spring. Its turned almost all the way to which it reads like 20 PSI on my boost gauge.

LMK guys thanks.

 

so u turned it all the way down? possibly the spring could be stuck....I do know that at higher gears boost spike can be higher.

 

higher gears = more load

cold air = denser air

flooring it from low rpm in a high gear = even more load

more load + even more load + denser air = you guessed it...spike!!!!!

 

+1.

The MBC will be more affected than an EBC. In addition to spiking 26psi, I was also running very lean compared to my summer tune.

I make it a point never to floor it in 5th unless I'm past 4500RPM anyway... 3000RPM + fifth gear + WOT = bad for your engine

 

No its turned almost all the way up which isn't a whole lot. Like the its 20 PSI in the warmer weather. Now it spikes to 26 PSI when flooring it in a low RPM in 5th gear.

Thanks for the info guys.

 

Get a EBC for consistency...I miss my greddy Profec II. Hot or cold...it did the boost I asked for.

 

Just stop flooring it in fifth gear at low RPMs... What kind of race is that anyway, or are you just doing it, just to be doing it?

 

He can floor it where ever he wants...who said he was racing?

 

Who races from a 5th gear roll? What kind of a question is that?

When your cruising on the highway you just floor the gas and watch your boost gauge. I was checking to see if the boost would go a little higher due to cooler temps. It did go higher all the way to 26 PSI.

 

You're supposed to adjust your boost by testing 5th gear WOT. If you adjusted in a lower gear, the colder air coupled with the 5th gear load will spike much higher than desired.

 

Might wanna check your MBC spring,mine got stuck and it was hitting 27 all the time,so i took my MBC apart and checked the springs.

 

Will do!

 

might be a wasegate problem

 

What happens when you keep it floored in 4th gear? Try it going uphill in 4th. You should be able to get close to 26# in 4th, if your seeing that much boost in 5th.

It could be that your actuator rod is adjusted too long and the turbo is spooling too slow. If this is the case then the engine is pulling through the turbo in the lower gears.

Try turning the MBC out countrclockwise all the way to its full soft(lowest boost setting). Then by shortening the wastegate´s actuator rod rou can raise preload up to about 17 PSI. Then raise boost the last couple PSI with your MBC.

 

What you describe, the slow rise of boost past your preset level in top gear is boost creep, not a spike. In part, it´s due to the colder weather. Anywhere between 1.5-2.0# of creep in 5th can be attributed to your colder Chicago air.