All:
Lots has been written about boost creep with a midpipe and un-ported wastegates w/ stock turbos... what i COULDN"T find w/ a search is wether this sort of thing generally occurs only at higher boost levels.

The dilema:
I have a resonated midpipe sitting in my garage, ready to replace my highflow cat. I have time to mail my PFC to SR for a re-phone-tune.... BUT, i'm due to be at Watkins Glen on the 1st and 2nd of september, and don't want massive creepage on the track... and i WOULDN'T have time to un-do the install if i have creepage. I'm only gonna run 10 psi on track as opposed to the 13 i run on the street.

How likely is it i will have a problem? Should i go for it?

 

My understanding is that creep will be worse the lower the boost setting is. The stock wastegate will be overwhelmed sooner than it would if the boost setting were higher.

 

In my experience, it is more controlable at lower levels.

There is less air going into the engine, therefore there is also less exhaust coming out. And hence, a better chance that the wastegate will be able to keep up.

I also have a feeling that it will be the worst at boost levels where the turbocharger efficency is higher. So either really high boost or really low boost should show less creep.

 

I have a Midpipe with a stock wastegate. It spikes 2 to 3 lbs at top end. My boost is set at 10psi. The most it has spiked was 3 lbs but that was when it was about 50 out side.

 

Thanks guys... say, will the fact that my motor is street ported help or hurt the creeping issue.. or not affect it at all?

 

In my experience, at 10psi, the most it will creep is to 13psi (stock wastegate) and it was cold as hell outside when that happened. this is with dp, mp, and catback.

 

You can always get a Pop off valve and set it for 11 psi. Even if the turbo puts out 20psi into the intake tract it will bleed off through the pop off valve before it gets into the intake plenum. Its a good safety measure for overboost and boost creep or other potential wastegate failures etc.

 

I don't want to bandaid it... i just don't have time to do it right (port wastegate) befor WGI... but i'd love to run open exhaust there!

 

I have never received boost creep with either of my stock twins that I have had on my car. My wastgate is stock too. I have problems with spiking, thats about it.

 

Well just wait until you can do it right and port the wastegate as needed after your track event. Either way its a bandaid. Using a pop off valve still bleeds off the extra boost that the wastegate would do on the exhaust side if it could flow and react fast enough. Plus during very cold months it will spike a couple psi no matter what. A POP off valve would still provide a margin of safety. Its just about striving to keep the motor intact regardless of the type of remidy. I may do a pop off valve in case my external wastegate fails. I think MAX COOPER has done this after he blew a motor this way.

 

let say you set your power FC for .80 bar. If you end up with something higher you set your duty cycle lower. When it gets colder outside you generally have to set it lower, thats why the power fc gives two settings.

 

That makes sense. My post above was my own theory. Your makes sense too. I don't know, just guessing really.

 

There was a post about this a long time ago which I think was lost unfortunately. It described the problem with boost creep in fairly good detail. I'll try and remember:

The post said that at the point when the wastegate is overloaded, that's when boost creep occurs (duh!). If that point is as 13 PSI, then whatever target boost you are going for after 13 (say 14 PSI), you'll creep to 17 PSI (or whatever your boost is creeping to). In this case, if you have your boost controller set to anything over 13 PSI, you'll always creep. However, if your boost controller is set to 12 PSI, you won't creep. Basically, whenever you creep, you creep all the way, not half-way.

The problem is knowing at what point the wastegate will be overloaded.

I believe this is why people are able to run midpipes at 10 PSI without any creep (and stock wastegates). However, people that try to run well over stock boost levels with midpipes do experience boost creep.

It's been a while since that post was on here so if I got it wrong, someone pipe up.

 

i never had creep or spike with my 94..i run 15 psi or 10 psi...no creep.

I have had both the N1 dual and the rb dual CB exhaust.

 

Okay, here's my experience. Generally you'll have more creep the lower you try to set your boost level. You'll get more creep in higher gears, too.

You better keep your cat in for the track even or you'll regret it. You might not get creep when driving on the street, but running through 4th gear you might end up creeping FAR beyond a safe level for your car.

Stock turbos and full exhaust, I had creep. It'd go up to about 15 psi. Didn't matter if my boost was set at 7psi or 12 psi, it would end up at 15psi. If I set my boost for 15 psi, it would stay at 15, though.

Later, I ported the wastegate. I still get a small amount of creep in cold weather. But under normal circumstances, I get whatever boost I want by dialing in the pills/valves. Even though I usually run 15 psi, I like having the option of running less.

I know there is always a temptation to try to install more mods before a track event, but it just doesn't make sense to half *** something, or install a part that might give you 10-20 hp, when it turns out you just have to LIFT on the back straight anyway because of boost creep. Additionally, you can't watch boost all the time so you would be risking an accident and risking blowing your engine.

Wade

 

I dont get it. I have been to the track for about 70+ runs. I have never had a problem with boost creep on either of my setups. I must have to do with the catback.

 

i havent got the creep at strip or track

 

The type of intercooler, intake, and exhaust makes a big difference. The less restrictive stuff usually leads to more creep. If you have a front mount IC or a more restrictive cat-back, you might not have the problem even with no cats.

I've also noticed a little variation in the size of the stock wastegates, I'm sure this has an effect. Also, some turbos might be slightly damaged, and some setups might be leaking a little bit of boost.

All these things help account for the differences people see with creep. It's just like anything else, different setups require different amounts of fuel, different cars make different amounts of power, etc.

Wade

 

Creep is caused by the waste gate not being able to release enough air. I'm pretty sure it will happen worse at lower boost settings than at higher.

 

ptrhahn - You might really want to NOT make any changes right now if your car is running fine.

I have ALWAYS regretted any last minute, somewhat rushed changes I've made to my past cars before an event. The old Murphy's Law syndrome. **** happens and it usually happens when you are far away from home.

Watkins Glen is a very nice track though

 

I would start at 7PSI and work ur way up until it creeps to no more than 13psi..........