3" exhaust=overbooting

[obx tsi]

Would adding a 3" exhaust cause my avcr to overboost? It went from a cosistant 14-16 psi to about 22 psi and bucking at wideopen throttle. As for now I just have my rear o2 just strapped up. I guess I need to readjust my avcr due to the better flowing wxhaust? Any thoughts would be helpful, thanks.

 

[Spln_Hrd]

Welcome to boost creep buddy. Buy an external wastegate period. I pissed around with all of the boost creep "cures" for way to long. My personal advise is an external wastegate, and never think about it again.

 

[Lonnie gandee]

As stated, an external will solve your problem, but will not help your performance as you have a bottleneck in your flow.

Porting will not only give you performance gains, but 99% of the time it solves this problem..

Especially porting out the wg area inside the turbo housing......Possibly even needing a 34mm flapper door upgrade....

 

[obx tsi]

Thanks for the quick responses. An external would solve the issue huh, now just affording to do that. How do I have a bottleneck in my flow? Do you mean the o2 housing?

 

[Spln_Hrd]

I ported the dog shit out of my 16g, added a 34 mm flapper, got an external dump, and removed material so the door could open all the way. Even after that my car never saw south of 19psi which was ok because I had alchy and a decent fuel system.

Not to step on anyones toes but porting for a few hours(of my time) is not worth the 5 horsies it may free up. If you need more poop out of a turbo slap on a 35r it will pull your cheeks right off your face.

 

[Lonnie gandee]

Thanks for the quick responses. An external would solve the issue huh, now just affording to do that. How do I have a bottleneck in my flow? Do you mean the o2 housing?

Yes thats why its creeping. You've opened up the exhaust and now it wants to flow beyond the limits of the stock o2 dumping abilities..Therefore it must be ported...

 

[Mr Peepers]

I strongly agree with porting. There are many how-to's on porting for boost creep, and it is MUCH more cost effective than going external.
If you have a small turbo(no offense ) such as a 16g etc then an external really shouldn't be needed to solve for creep, but instead to hold higher boost pressures.

p.s. if you "upgrade" to a larger flapper you are more likely to have the flapper blow open and not hold as much boost.

 

[turbolover10]

Porting it can help keep the boost down or even cure it from creeping, depending on how much you take out and how good you port the wasgate passage... However, to much porting can lead to cracks. "I know from experience."

So like suggested above the easiest way is to just go external and be done with it, specailly if your trying to run it with stock fuel and nothing to tune with.. If you don't have the money and already have the tools then I would suggest porting it cause it can and has made a huge difference on not only my car but other members aswell. Search the forums, theres a great right up on how to port correctly!

 

[Spln_Hrd]

Yes thats why its creeping. You've opened up the exhaust and now it wants to flow beyond the limits of the stock o2 dumping abilities..Therefore it must be ported...

I am not trying to argue with you on this, please dont think I am an a-hole.

But I went from a stock o2 housing to a rnr 3" tubular o2 housing with a external dump and I saw no gains on controlling my boost. This is my personal expiernce with my car for about 2 years.

I feel that the design flaw is in the wastegate/flapper/turbine housing from my expierences with a MHI small 16g.

 

[Lonnie gandee]

I am not trying to argue with you on this, please dont think I am an a-hole.

But I went from a stock o2 housing to a rnr 3" tubular o2 housing with a external dump and I saw no gains on controlling my boost. This is my personal expiernce with my car for about 2 years.

I feel that the design flaw is in the wastegate/flapper/turbine housing from my expierences with a MHI small 16g.

AAHHHHH..

AS-ole.... j/k

I didnt mean to really pinpoint the 02 housing, I was referring to the wg passage to the 02 housing. The same thing I believe your referring to asswell.

I've never experianced creep with a sm 16g, but I had a full 2.5", though. But my evo3 crept like a sob. I ported everything, and installed a bigger door... Which is the same size as an exhaust valve, oddly enough...

Its all good...

 

[obx tsi]

Ok, thanks for the info. For now I will just not boost so much. jMaybe I can somewhat control it with my avcr for temporary. Porting would be much easier for me right now although if I come across a decent priced external set up I will try to get it.

 

[Mr Peepers]

I am not trying to argue with you on this, please dont think I am an a-hole.

But I went from a stock o2 housing to a rnr 3" tubular o2 housing with a external dump and I saw no gains on controlling my boost. This is my personal expiernce with my car for about 2 years.

I feel that the design flaw is in the wastegate/flapper/turbine housing from my expierences with a MHI small 16g.

There are essentially 3 bottlenecks/flaws in the stock internal WG setup.
1. Turbine housing
2. O2 housing
3. Flapper

There is an abrupt turn in the turbine housing leading to the WG hole, then a flapper that only opens ~30* and finally an poorly flowing o2 housing. Each car/setup is different and one thing won't always fix every car. If the flapper is barely opening then you can try whatever o2 housing you want and see no difference, or vice versa.

Yes, an external setup would cure it 99% of the time, but there are much cheaper things you can do with an internal setup to cure it as well.

 

[turbolover10]

Well said!

I am not trying to argue with you on this, please dont think I am an a-hole.

But I went from a stock o2 housing to a rnr 3" tubular o2 housing with a external dump and I saw no gains on controlling my boost. This is my personal expiernce with my car for about 2 years.

I feel that the design flaw is in the wastegate/flapper/turbine housing from my expierences with a MHI small 16g.

Thats with an external dump o2 with an internal wastegate still right??

 

[obx tsi]

What size external wastgate do you guys suggest? I see 35-50 mm, to many choices if I go this route.

 

[Mr Peepers]

Here is another boost creep "cure" to "piss" around with http://www.dsmtuners.com/forums/turbo-system-tech/267309-evo3-16g-boost-creep-solved.html

At the moment I'm not taking any orders, but it's a good thread to get the idea to do it yourself or even just understand boost control a little better. As long as you do a test for creep with the WGA arm unattached and find out where the bottle neck is first, it will help if not cure boost creep.

Maybe someday I'll get a write-up/how-to on the process... someday.

 

[DSMunknown]

I ported the dog shit out of my 16g, added a 34 mm flapper, got an external dump, and removed material so the door could open all the way.

The flapper valve will never open up "all the way". 45 degrees at the most. Just my three cents, but I hate the option of the 34mm flapper.

 

[cruisintalonawd]

I would say try porting first too. Its a free mod and if it works your not out any money!

 

[Lonnie gandee]

The flapper valve will never open up "all the way". 45 degrees at the most. Just my three cents, but I hate the option of the 34mm flapper.

True, but removing some material form behind the flapper door, on the arm, it keep its from hittin the housing.... And it does help it to open more.

 

[Mr Peepers]

True, but removing some material form behind the flapper door, on the arm, it keep its from hittin the housing.... And it does help it to open more.

I have not seen a stock MHI WGA and flapper setup that hit the housing. Nearly all flappers are limited by the stroke of the WGA from personal experience. Once you extend the range of the WGA then it will become a problem, and can usually be solved by a well placed notch on the flapper arm.

 

[Spln_Hrd]

Well said!



Thats with an external dump o2 with an internal wastegate still right??

Yes, with an external dump on a 34 mm internal gate. I ported the turbine housing, the wastegate passage, then I removed the pin so I could run the lever that holds the flapper back and forth until I got it to open as far as posible.

 

[Spln_Hrd]

What size external wastgate do you guys suggest? I see 35-50 mm, to many choices if I go this route.

A tial 35 or 38 will do the trick. I am using the 38 on a HUGE turbo(garrett dual bb gt3582r)

 

[Lonnie gandee]

Good call! I seen you thread about extending the flapper arm. Did you test it before and after with a compressor to see it move. Cause when it tested my sm 16 actuator, it wouldnt go all the way. But the evo 3 actuator moved farther, and came open more than the sm16.

But it didnt touch. After i bent the the wg braket towards the flapper, it did open all the way.
Easier than welding without a welder...

 

[Mr Peepers]

Good call! I seen you thread about extending the flapper arm. Did you test it before and after with a compressor to see it move. Cause when it tested my sm 16 actuator, it wouldnt go all the way. But the evo 3 actuator moved farther, and came open more than the sm16.

But it didnt touch. After i bent the the wg braket towards the flapper, it did open all the way.
Easier than welding without a welder...

The only problem with that is the flapper will be partly open or have very little preload, making it hard to build boost. The stock MHI WGA for MHI 14b's 16g's etc (all tdo5h compressor housings) all open about 3/8" IIRC. The diaphragm safely allows for ~1" of articulation with some slack at each end of the travel.

All WGA were tested before and after with a compressor, and attached to a spare 16g. I have a video of the modified WGA opening and closing the flapper if you are interested.

 

[kenamond]

I think that Mr Peepers' WGA mod is the "best" solution to the e3b16g creep problem. Too bad you can't buy the modded WGA.

Porting isn't free. The burrs and die grinder cost some money. But it's cheaper than an external WG. A burr is $20+S&H. A pneumatic grinder is $20 if you happen to have an air compressor. An electric grinder is $50. If you're just porting the housing, one burr will suffice. If you're doing the O2 housing and/or ex. mani, you'll probably need two burrs. Then you need a dremmel and flapper wheel to smooth things out.

The other solution is to get supporting mods to run 20psi. But that's even more expensive than the external WG.

 

[Mr Peepers]

I think that Mr Peepers' WGA mod is the "best" solution to the e3b16g creep problem. Too bad you can't buy the modded WGA.

Thanks!

The problem with selling/modding them is that it takes a good 4-5 hours to do one(even after making all the jigs and learning tricks), and a half hour drive to the garage with all the tools. Add that to 58 hours of work a week and you can see why $50 (not to be cocky) wasn't worth the time.