The dreaded phrase, boost creep....and I have it.

Heres the background info. I got the inlinpro kit with GT35R upgrade and turbosmart 38mm wastegate with external dump tube. At first I had the 7psi spring installed and prevtec my boost would hold steady at ~50kpa or ~7.5psi but once vtec hit it would creep up to nearly 11psi at redline sometimes. The weird thing is, the car will ONLY do it on the road. I went to finish dyno tuning and it held 7.5psi all the way to redline no issues. I then bring it back out onto the road that day and it was going near 10 again. The dyno room was just as cold as it was outside so thats what confused me. At night the creep is horrible

I now just installed a 5psi spring in hopes of limiting the creep. Unfortunatly, the same thing is still happening, holding (now) steady 40kpa prevtec and once vtec hits, I'm back to creeping up near 10psi again.

The springs are definatly different so it can't be that. I checked my boost gauge to see if maybe the line was cinked, which it wasn't. I'm starting to run out of ideas why this is happening.

Is the GT35R so powerful that it really can't be run at such a low PSI which is why the wastegate can't hold it? I have an invidia dual exhaust but I don't that would be to much of a cause for this spiking.

At least with the warmer weather, the creep should be stopping and a headgasket will be on the way. I don't really feel safe boosting up to 10psi on a stock engine.

 

eh, with my 7psi spring and weather like we've been having i creep up to just under 10lbs but no matter how cold ive never gone past that. Im pretty sure we have an identical set up except for engine managment. I dont know really what to tell you, hopefully someone chimes in id like to know whats going on as well.

 

I had a similar problem. I got a manual boost controller and the boost stop creeping.

 

hm, that could be why mine doesnt creep that high as well? Im running the inlinePRO boost controller.

 

I would guess either your dump tube is too restrictive, or if you're routing it back into the exhaust, something with that setup is too restrictive.

I get about 3lbs of creep myself even with the EMS controlling boost. I think it's because of my ghetto-fabbed dump tube but I havent really looked into it that thoroughly yet.

 

I would get a larger wastegate. 44mm or so. if you have changed springs on the 38 and it didn't help then it is just to small to handle that kind of a flush. A boost controller cannot lower your boost. It only increases it. Unless you cause a leak when you install it.

Here is a recent post.

If you purchase a EXTERNAL WASTEGATE, you can buy different springs to determine what boost you want to run. a 5psi spring is 5psi, a 7psi is 7 psi an sor forth. Now, boost controllers can usually do DOUBLE the wastegate spring. so a 10 psi spring can USUALLY do 20psi.

on a stock motor , sure you could run a 5psi wastegate spring an use a manual or electronic boost controller to turn the boost up to say 8-10psi, no problem with that at all.

Manual boost controllers SUCK. they arent very accurate, and if you make an adjustment, you have to do a pull to see what boost your at. With an electronic boost controller, you can set it to a PSI and with an actuator an pressure sensor it dictates boost level based on your settings for you. much easier.

Manual boost controllers are usually underhood, so youll have to stop, pull over, pop hood, and turn knob. Electronic boost controllers you can make adjustments inside the car.

BOOST CREEP is usually by having too small of a wastegate or vacuum leaks or an improperly hooked up boost controller.

CREEPING usually happens because the wastegate cannot dump enough air fast enough. A turbo spins astronomically, if there were no wastegate it would do 100psi since it would spin faster and faster the more the motor revs or sucks in air.

Imagine putting a BIG turbo (GT42R)with a 38mm wastegate. THe turbo is going to spin and generate positive pressure aka boost. now, imagine how much air that big turbo is moving. you have a small wastegate. lets say you have a 15psi spring. when you get to the 15psi level, the wastegate has got to open an dump enough air out of the manifold to keep boost stable at 15psi. However, as i said before, the turbo keeps spinning faster an faster regardless since there is no way to physically slow the turbo down. Now that big turbo is forcing more air into the motor an overpowering the tiny wastegate, which means you cant dump the excess air, and the turbo free spins generating more boost. you now are going past the 15psi level, and your boost creeping.

make sense?

 

A boost controller most definitely can lower the boost. Not sure where your getting that from...

 

I thought a boost controller can only lower the boost as much as the spring will allow (aka with a 5psi spring, the lowest the boost controller could allow was 5psi).

As far as my dumptube goes, its atmospheric and is pretty much straight out. I doubt the hold up is there.

I just installed the inlinepro boost controller but have it set to run off the spring for now to bad the spring still lets the car overboost in cold weather

For the record, I installed the 5psi spring first (before the boost controller) to see if it helped with the creep (it didn't after vtec)

 

Please explain to me how a boost controller will lower the boost below what the minimum setting of the wastegate is?

 

Ok ok you got me there...I didnt mean to imply you could lower the boost below the min. wastegate spring setting. I misread what he was saying. My bad!