Boost Creep (not a usual BS thread)
Oct 9, 2009, 09:59 PM
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Boost Creep (not a usual BS thread)
Ok, I'm no newb to the evo or to the world of turbos etc...
I've searched, and there are 2 full pages of titles with "boost creep" in them. 99% of these threads are full of misinformation, people who don't know what they're talking about, or made up solutions of trial and error that result with either no change, a possible change, or a waste of time and money.
I'm sure others are experiencing this, and I'm curious, what has been done SUCCESSFULLY to rid of this issue.
First off, I've seen most people begin to notice creep issues when they upgrade their o2 housing, mine is stock.
Boost creep happens when the wastegate hole isn't large enough to support the increased flow of the exhaust, so the gasses you want to bypass the turbine, are actually forced through the turbine, therefore, resulting in higher than desired boost. Some definitions will differ slightly, but that's basically it.
Now, some tuners believe that tuning around this by adding fuel as protection of the unstable high-boost is a solution, but that is a mere band-aid. Others say that porting the wastegate hole bigger, to about 1.5" is a good idea, but I have yet to read a real success story on this, and I'd rather not take my turbo off, get the hole bored out, and risk the flapper not sealing and/or wasting my time and money.
Mods: Perrin Intake with filter and inlet pipe, Hallman MBC, DC Catless Downpipe, Greddy Evo2 Catback, walrbo fp and an Ivey tune.
I'd like to tune my setup to hit 25psi, hold there and then taper down as a turbo of this size should. Instead, I have to tune my mbc to hit at 21psi, where it then gradually increases to 25psi in gears 1-3, and 4-6 it will reach as high as 28 psi due to the increased load and constant boost creep --- I avoid situations of going WOT in 4th-6th gear at a low rpm for this reason exactly.
So, solutions. I shortened up the lines going to my boost controller, knowing that generally, the shorter the path, the more controlled your boost will be. This theory was somewhat relative, but didn't really cure anything. Tomorrow, I will disconnect the boost controller and see where I'm at, in all gear, at wide open throttle from low rpm to redline. Theoretically, the problem should still persist if it is in fact a flow problem of the wastegate outlet diameter, if not, then is it a boost control problem? or is it the higher boost levels that then make the diameter of the wastegate hole too small to handle boost above XXpsi?
I hope this thread becomes a one-stop-shop for those inquiring or experiencing this issue on a stock turbo setup. Please don't chime in if you have no valid input, and if you do have a solution that has worked for you, provide details of the situation and the method you used.
I've searched, and there are 2 full pages of titles with "boost creep" in them. 99% of these threads are full of misinformation, people who don't know what they're talking about, or made up solutions of trial and error that result with either no change, a possible change, or a waste of time and money.
I'm sure others are experiencing this, and I'm curious, what has been done SUCCESSFULLY to rid of this issue.
First off, I've seen most people begin to notice creep issues when they upgrade their o2 housing, mine is stock.
Boost creep happens when the wastegate hole isn't large enough to support the increased flow of the exhaust, so the gasses you want to bypass the turbine, are actually forced through the turbine, therefore, resulting in higher than desired boost. Some definitions will differ slightly, but that's basically it.
Now, some tuners believe that tuning around this by adding fuel as protection of the unstable high-boost is a solution, but that is a mere band-aid. Others say that porting the wastegate hole bigger, to about 1.5" is a good idea, but I have yet to read a real success story on this, and I'd rather not take my turbo off, get the hole bored out, and risk the flapper not sealing and/or wasting my time and money.
Mods: Perrin Intake with filter and inlet pipe, Hallman MBC, DC Catless Downpipe, Greddy Evo2 Catback, walrbo fp and an Ivey tune.
I'd like to tune my setup to hit 25psi, hold there and then taper down as a turbo of this size should. Instead, I have to tune my mbc to hit at 21psi, where it then gradually increases to 25psi in gears 1-3, and 4-6 it will reach as high as 28 psi due to the increased load and constant boost creep --- I avoid situations of going WOT in 4th-6th gear at a low rpm for this reason exactly.
So, solutions. I shortened up the lines going to my boost controller, knowing that generally, the shorter the path, the more controlled your boost will be. This theory was somewhat relative, but didn't really cure anything. Tomorrow, I will disconnect the boost controller and see where I'm at, in all gear, at wide open throttle from low rpm to redline. Theoretically, the problem should still persist if it is in fact a flow problem of the wastegate outlet diameter, if not, then is it a boost control problem? or is it the higher boost levels that then make the diameter of the wastegate hole too small to handle boost above XXpsi?
I hope this thread becomes a one-stop-shop for those inquiring or experiencing this issue on a stock turbo setup. Please don't chime in if you have no valid input, and if you do have a solution that has worked for you, provide details of the situation and the method you used.
Oct 9, 2009, 10:05 PM
#2
I had boost creep as well. The wastegate hole was too small for my o2 housing. The first time my friend ported the hole to fix the issue, he didnt open it enough. The boost creep was less agressive but still present. The second attempt he ported as much as he can probably a golf ball size or larger, and it is completely gone.
Using Hallman in-cabin manual boost controller I boost consistantly in all the gears 1 through 5. Spiking 25 and slowly tapering to 18 at redline. But the higher the gear the slighly more psi (only 1 psi difference) it will hold due to load.
Using Hallman in-cabin manual boost controller I boost consistantly in all the gears 1 through 5. Spiking 25 and slowly tapering to 18 at redline. But the higher the gear the slighly more psi (only 1 psi difference) it will hold due to load.
Oct 9, 2009, 10:10 PM
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I had boost creep as well. The wastegate hole was too small for my o2 housing. The first time my friend ported the hole to fix the issue, he didnt open it enough. The boost creep was less agressive but still present. The second attempt he ported as much as he can probably a golf ball size or larger, and it is completely gone.
Using Hallman in-cabin manual boost controller I boost consistantly in all the gears 1 through 5. Spiking 25 and slowly tapering to 18 at redline. But the higher the gear the slighly more psi (only 1 psi difference) it will hold due to load.
Using Hallman in-cabin manual boost controller I boost consistantly in all the gears 1 through 5. Spiking 25 and slowly tapering to 18 at redline. But the higher the gear the slighly more psi (only 1 psi difference) it will hold due to load.
Oct 9, 2009, 10:14 PM
#4
It was only because of the wastegate hole in the o2 housing. I didnt make any changes other than porting open that hole. Just make sure you port it really good. The first attempt we didnt port enough and it still had boost creep. I guess the bigger the better for the o2 housing.
This is the solution. Good luck.
Oct 9, 2009, 10:20 PM
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so you didn't touch the turbo, you're saying it's the o2 housing due to the size of the outlet in the divorced section. The thing is, I guess these upgraded o2's are actually worse than stock. I don't read of many people having issues with the stock o2 housing, which is why I'm so curious.
Oct 9, 2009, 10:43 PM
#7
so you didn't touch the turbo, you're saying it's the o2 housing due to the size of the outlet in the divorced section. The thing is, I guess these upgraded o2's are actually worse than stock. I don't read of many people having issues with the stock o2 housing, which is why I'm so curious.
The boost creep we all get from many of the upgraded o2 housings is because of how you mentioned it in your first post. The wastegate port is too small and the back up pressure causes the turbo to spool more.
As for stock o2 housing:
The OEM o2 housing are carefully designed and all are pretty much created equally. The after market are exactly what they are after market. Most are made from outsourced locations. So they are not all created equally. Some have small wastegate hole and some have "ok" sized.
In my opinion the proportionate sizes matter as well. Example. The stock turbine side of the o2 housing has smaller X volume compared to aftermarket, so the wategate on stock can be smaller as well compared to aftermarket. So if the exhaust gasses passing through cant squeeze through the wastegate hole, well guess what, the turbine side is small to so you just get back pressure. If the difference is great enough then the exhaust follows through least resistance, in this case the turbine side and causes boost creep.
Also other factors could contribute with the angle of the exhaust flow going out. If there is a wall around the divorces section then exhaust pressure hitting it can cause bottle neck type issues and boost creep etc...
Hope this makes sense, sorry its late going to go to bed now.
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Oct 10, 2009, 10:54 AM
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so, just back from some testing.
I turned the hallman mbc all the way down, which basically makes the car run off the wastegate spring. The car was holding 13ish psi without a problem in gears 1,2 and in 3rd, it was climbing to around 15psi, and staying around there in the rest of the gears.
I then began to turn the boost up in small incriments. When hitting 15psi in 3rd gear, boost would stay moderately controlled, maybe feather up to 16psi at most. now in 4th-6th gear, boost was reaching as high as 20psi already. I full understand load vs. pressure, but there has to be a way around this. I've never had issues like this on any of my previous cars (gt30r audi, 50 trim Gti) Obviously, those turbos are bigger and I was using a 38mm External gate, paired with an mbc or a greddy profec.
Finally, I turned the boost back where it was originally. The car hits at 20psi and rises slowly to 25, then to 26-28 in the higher gears where I obviously let off. I'm pretty sick of this.
I turned the hallman mbc all the way down, which basically makes the car run off the wastegate spring. The car was holding 13ish psi without a problem in gears 1,2 and in 3rd, it was climbing to around 15psi, and staying around there in the rest of the gears.
I then began to turn the boost up in small incriments. When hitting 15psi in 3rd gear, boost would stay moderately controlled, maybe feather up to 16psi at most. now in 4th-6th gear, boost was reaching as high as 20psi already. I full understand load vs. pressure, but there has to be a way around this. I've never had issues like this on any of my previous cars (gt30r audi, 50 trim Gti) Obviously, those turbos are bigger and I was using a 38mm External gate, paired with an mbc or a greddy profec.
Finally, I turned the boost back where it was originally. The car hits at 20psi and rises slowly to 25, then to 26-28 in the higher gears where I obviously let off. I'm pretty sick of this.
Oct 10, 2009, 09:10 PM
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Probably you just need to port the turn-in radius on the entrance to the wastegate bypass port located in the inlet area of the turbine housing. Actually, as you know, it is a twin scroll design (one bypass port from each chamber of the turbine inlet area). But, I've found that by porting just the short-side(the one closest to the WG flapper valve), you can eliminatte boost creep.
You don't wan't to mess with the entire length of the port. Just do the turn-in radius. Don't try to enlarge the exit of the port at the flapper valve seat area either as there is very little room for error at the flapper valve seat.
You don't wan't to mess with the entire length of the port. Just do the turn-in radius. Don't try to enlarge the exit of the port at the flapper valve seat area either as there is very little room for error at the flapper valve seat.
Last edited by sparky; Oct 10, 2009 at 09:55 PM.
Oct 10, 2009, 11:33 PM
#12
so, just back from some testing.
I turned the hallman mbc all the way down, which basically makes the car run off the wastegate spring. The car was holding 13ish psi without a problem in gears 1,2 and in 3rd, it was climbing to around 15psi, and staying around there in the rest of the gears.
I then began to turn the boost up in small incriments. When hitting 15psi in 3rd gear, boost would stay moderately controlled, maybe feather up to 16psi at most. now in 4th-6th gear, boost was reaching as high as 20psi already. I full understand load vs. pressure, but there has to be a way around this. I've never had issues like this on any of my previous cars (gt30r audi, 50 trim Gti) Obviously, those turbos are bigger and I was using a 38mm External gate, paired with an mbc or a greddy profec.
Finally, I turned the boost back where it was originally. The car hits at 20psi and rises slowly to 25, then to 26-28 in the higher gears where I obviously let off. I'm pretty sick of this.
I turned the hallman mbc all the way down, which basically makes the car run off the wastegate spring. The car was holding 13ish psi without a problem in gears 1,2 and in 3rd, it was climbing to around 15psi, and staying around there in the rest of the gears.
I then began to turn the boost up in small incriments. When hitting 15psi in 3rd gear, boost would stay moderately controlled, maybe feather up to 16psi at most. now in 4th-6th gear, boost was reaching as high as 20psi already. I full understand load vs. pressure, but there has to be a way around this. I've never had issues like this on any of my previous cars (gt30r audi, 50 trim Gti) Obviously, those turbos are bigger and I was using a 38mm External gate, paired with an mbc or a greddy profec.
Finally, I turned the boost back where it was originally. The car hits at 20psi and rises slowly to 25, then to 26-28 in the higher gears where I obviously let off. I'm pretty sick of this.
Oct 11, 2009, 07:05 AM
#13
THat eliminates the WG hole, I think it's your MBC.
If the hole was too small it wouldnt hold boost that low, it would start climbing.
Swap out the boost controller, I have seen 1 boost controller do that out of a ton I have used.
Just try another one.
Sean
If the hole was too small it wouldnt hold boost that low, it would start climbing.
Swap out the boost controller, I have seen 1 boost controller do that out of a ton I have used.
Just try another one.
Sean
so, just back from some testing.
I turned the hallman mbc all the way down, which basically makes the car run off the wastegate spring. The car was holding 13ish psi without a problem in gears 1,2 and in 3rd, it was climbing to around 15psi, and staying around there in the rest of the gears.
I then began to turn the boost up in small incriments. When hitting 15psi in 3rd gear, boost would stay moderately controlled, maybe feather up to 16psi at most. now in 4th-6th gear, boost was reaching as high as 20psi already. I full understand load vs. pressure, but there has to be a way around this. I've never had issues like this on any of my previous cars (gt30r audi, 50 trim Gti) Obviously, those turbos are bigger and I was using a 38mm External gate, paired with an mbc or a greddy profec.
Finally, I turned the boost back where it was originally. The car hits at 20psi and rises slowly to 25, then to 26-28 in the higher gears where I obviously let off. I'm pretty sick of this.
I turned the hallman mbc all the way down, which basically makes the car run off the wastegate spring. The car was holding 13ish psi without a problem in gears 1,2 and in 3rd, it was climbing to around 15psi, and staying around there in the rest of the gears.
I then began to turn the boost up in small incriments. When hitting 15psi in 3rd gear, boost would stay moderately controlled, maybe feather up to 16psi at most. now in 4th-6th gear, boost was reaching as high as 20psi already. I full understand load vs. pressure, but there has to be a way around this. I've never had issues like this on any of my previous cars (gt30r audi, 50 trim Gti) Obviously, those turbos are bigger and I was using a 38mm External gate, paired with an mbc or a greddy profec.
Finally, I turned the boost back where it was originally. The car hits at 20psi and rises slowly to 25, then to 26-28 in the higher gears where I obviously let off. I'm pretty sick of this.
Oct 11, 2009, 07:24 AM
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anyone have a spare mbc they want to send me? i'll send it right back 
the mbc is hooked up correctly. sourced directly from the turbo and then going directly to the wastegate with absolutely no interruptions.
the mbc is hooked up correctly. sourced directly from the turbo and then going directly to the wastegate with absolutely no interruptions.
