Begi-s boost creep issues - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


DIY Turbo Discussion greddy on a 1.8? homebrew kit?

Reply
 
 
 
LinkBack Thread Tools
Old 02-22-2008, 12:04 AM   #21
Elite Member
iTrader: (15)
 
Join Date: Dec 2007
Location: San Antonio, Texas
Posts: 4,889
Total Cats: 28
Default

Quote:
Originally Posted by cjernigan View Post
Zx-tex. I strongly suggest you take your turbine housing off and take the time to port it. As hard as you plan to drive your car, it will be more than worth while to you.
Should be ported already by Corky when I pick it up
ZX-Tex is offline   Reply With Quote
Old 02-25-2008, 03:24 PM   #22
Elite Member
iTrader: (15)
 
Join Date: Dec 2007
Location: San Antonio, Texas
Posts: 4,889
Total Cats: 28
Default

OK I picked up the kit on Friday and it was indeed ported. Corky showed me where the modifications were done. Most of the material was removed (ported) in the area between the exhaust manifold flange and the wastegate area. The wastegate hole was opened up a bit as well.

Yes I know... TTIUWP... pictures coming soon...
ZX-Tex is offline   Reply With Quote
Old 02-25-2008, 03:27 PM   #23
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,809
Total Cats: 1,780
Default

yep

Braineack is offline   Reply With Quote
Old 02-26-2008, 03:43 PM   #24
Former Vendor
 
Join Date: Jun 2006
Location: Bell Tuning & Performance
Posts: 1,338
Total Cats: -78
Default

I was unable to photograph some of the mods. But here is one. I would not recommend that you do this at home though.
Stephanie
Attached Thumbnails
Begi-s boost creep issues-p2213271.jpg  
Stephanie Turner is offline   Reply With Quote
Old 02-26-2008, 04:10 PM   #25
Elite Member
iTrader: (15)
 
Join Date: Dec 2007
Location: San Antonio, Texas
Posts: 4,889
Total Cats: 28
Default

My turbine housing looks EXACTLY like that one... because it is that one
Some more pictures. I processed these so the sharpness is much higher to exaggerate the details. The flange surface for example is smoother than how it looks here.
Attached Thumbnails
Begi-s boost creep issues-turbine-1.jpg   Begi-s boost creep issues-turbine-2.jpg  
ZX-Tex is offline   Reply With Quote
Old 02-26-2008, 04:17 PM   #26
Elite Member
iTrader: (9)
 
Saml01's Avatar
 
Join Date: Jul 2007
Location: NYC
Posts: 5,730
Total Cats: 2
Default

So thats whats meant by porting the wastegate. I thought it was opening the hole more.
Saml01 is offline   Reply With Quote
Old 02-26-2008, 04:36 PM   #27
Elite Member
iTrader: (15)
 
Join Date: Dec 2007
Location: San Antonio, Texas
Posts: 4,889
Total Cats: 28
Default

This image was taken looking through the exit side of the wastegate, back towards the exhaust flange (looking upstream). The arrow points at the area where the material was removed. You can see the resulting arc shape in the casting.
Attached Thumbnails
Begi-s boost creep issues-turbine-3.jpg  
ZX-Tex is offline   Reply With Quote
Old 02-26-2008, 04:42 PM   #28
Elite Member
iTrader: (15)
 
Join Date: Dec 2007
Location: San Antonio, Texas
Posts: 4,889
Total Cats: 28
Default

The idea as explained to me by Corky is that the gases have a more direct path to the waste gate area. Loosely speaking, they do not have to change direction as quickly. The porting makes the change in direction of flow more gradual, thus resulting in better flow into the wastegate pocket.
ZX-Tex is offline   Reply With Quote
Old 02-26-2008, 04:46 PM   #29
Elite Member
iTrader: (9)
 
Saml01's Avatar
 
Join Date: Jul 2007
Location: NYC
Posts: 5,730
Total Cats: 2
Default

^ Very interesting. I wouldnt have thought that would ever make a difference. I was constantly under the impression it was making the wastegate opening bigger. Seems to me there is some room to gain, how come they arent opened more?
Saml01 is offline   Reply With Quote
Old 02-26-2008, 04:52 PM   #30
Elite Member
iTrader: (15)
 
Join Date: Dec 2007
Location: San Antonio, Texas
Posts: 4,889
Total Cats: 28
Default

Well I am guessing here, but based on the general understanding I have of flow (I am a Mech Engineer) as far as waste gate size goes
- There needs to be a certain amount of overlap between the waste gate valve face and the waste gate opening in order for it to seal properly. Leakage at low boost levels would mean slower spool times. The valve can only be so big in the housing due to space limitations, thus indirectly limiting the size of the port.
- If the opening is a lot larger, then the flow transition as the wastegate valve opens would be much more abrupt, possibly leading to instability in boost control. That is a guess though.
ZX-Tex is offline   Reply With Quote
Old 02-26-2008, 04:55 PM   #31
Senior Member
 
Join Date: Nov 2007
Location: somewhere in NoVA
Posts: 550
Total Cats: -1
Default

I'd be willing to say it is because there is more cost to do the extra work by the people making the cast pieces.

We manufacture cast products for our equipment and the more finishing that is done to the device at the end all costs us more $$$ overall. So there is a fine line between functional and works as specified vs. optimal and high performance.

Cheers,
Prospero

Quote:
Originally Posted by Saml01 View Post
^ Very interesting. I wouldnt have thought that would ever make a difference. I was constantly under the impression it was making the wastegate opening bigger. Seems to me there is some room to gain, how come they arent opened more?
Prospero is offline   Reply With Quote
Old 02-26-2008, 05:00 PM   #32
Elite Member
iTrader: (15)
 
Join Date: Dec 2007
Location: San Antonio, Texas
Posts: 4,889
Total Cats: 28
Default

Quote:
Originally Posted by Prospero View Post
I'd be willing to say it is because there is more cost to do the extra work by the people making the cast pieces.

Yes, that too, good point. I did a little casting design work in my earlier days so I know enough to be dangerous. If you look at it, it would be hard to pull the core out of the casting with it tapered the way it is in the modified version, assuming it was sand cast, which it probably was. Of course there is always investment casting, which allows for flexibility in design, but that is more expensive for production pieces.
ZX-Tex is offline   Reply With Quote
Old 02-26-2008, 05:10 PM   #33
Senior Member
 
Join Date: Nov 2007
Location: somewhere in NoVA
Posts: 550
Total Cats: -1
Default

Quote:
Originally Posted by ZX-Tex View Post
Yes, that too, good point. I did a little casting design work in my earlier days so I know enough to be dangerous. If you look at it, it would be hard to pull the core out of the casting with it tapered the way it is in the modified version, assuming it was sand cast, which it probably was. Of course there is always investment casting, which allows for flexibility in design, but that is more expensive for production pieces.
No doubt that it's a sand cast piece... and you're right about investment casting being the way to fly; just getting my engineers to keep from designing outside of what we built into the cast is the hard part. We cast a square today and they'll make an oval tomorrow.

Cheers,
Prospero
Prospero is offline   Reply With Quote
Old 02-26-2008, 05:29 PM   #34
Elite Member
iTrader: (15)
 
Join Date: Dec 2007
Location: San Antonio, Texas
Posts: 4,889
Total Cats: 28
Default

Here is a good article on high-end, racing application turbos compared to production turbos. There is some discussion in there on turbine housing design.
http://www.mazdausa.com/MusaWeb/disp...ession4&bhcp=1

5-axis CNC machined compressor wheels... CHA-CHIIING!
ZX-Tex is offline   Reply With Quote
Old 02-26-2008, 06:11 PM   #35
Elite Member
iTrader: (13)
 
cjernigan's Avatar
 
Join Date: Oct 2006
Location: Atlanta, GA
Posts: 8,147
Total Cats: 6
Default

Quote:
Originally Posted by ZX-Tex View Post
5-axis CNC machined compressor wheels... CHA-CHIIING!
When going through my recent manufacturing magazine from SME I was suprised to see between 7 and 10 ads showing some kind of turbine/compressor wheel being machined by 5 axis mills. Very impressive to see the kind of work they can do. Thats also when you get into the realm of composite turbine housings and titanium internals.

Edit: That's funny, seen that article before, hadn't looked at it until after i typed this. I got to see one of those "elite" turbos, they were using it on a particular MSMS car at the time.
cjernigan is offline   Reply With Quote
Old 02-26-2008, 07:13 PM   #36
Elite Member
iTrader: (15)
 
Join Date: Dec 2007
Location: San Antonio, Texas
Posts: 4,889
Total Cats: 28
Default

Yeah that makes a good ad for a mil considering that is a pretty complex profile to machine!
ZX-Tex is offline   Reply With Quote
Old 02-26-2008, 07:44 PM   #37
Junior Member
Thread Starter
 
Join Date: Jan 2008
Posts: 208
Total Cats: 0
Default

damn now I need to find some time to pull my turbo and send the exhaust housing back to bell
driftbandito is offline   Reply With Quote
Old 02-26-2008, 10:17 PM   #38
Newb
 
Join Date: Apr 2007
Posts: 1
Total Cats: 0
Default

The porting shown in post #28 above is IDENTICAL to the porting recommended (required?) when installing catless downpipes/free flow exhausts on VF39-equipped Subaru's. The reason? To avoid/cure boost creep. Many have opened up the diameter of the port excessively with disastrous results. The technique shown and described above is how it should be done.

Scott
e28fixer is offline   Reply With Quote
Old 02-26-2008, 10:52 PM   #39
Elite Member
iTrader: (21)
 
paul's Avatar
 
Join Date: Jun 2006
Location: Point Pleasant, NJ
Posts: 2,957
Total Cats: 2
Default

when Tim did mine he did both the path to the wastegate and the opening itself. i have no boost leak issues.
paul is offline   Reply With Quote
Old 02-26-2008, 11:24 PM   #40
Junior Member
 
Join Date: Dec 2007
Location: Indianapolis
Posts: 167
Total Cats: 0
Default

Quote:
Originally Posted by driftbendito View Post
I exchanged e-mails with Corky a couple of times and he said the correct way to remedy the problem would be to port the wastegate, re-install the cat, or place a restrictor in the exhaust system somewhere. Installing the stock cat or placing a restrictor in my exhaust would be taking a step back so my only option is to port the wastegate. My boost creep issues are most likely linked to my test pipe and exhaust system. I know a few people running the kit with stock exhaust and the kit runs 6psi all day.
That does not make sense at all. A free flowing exhaust system should let the exhaust gases exit more quickly = less boost creep.
I had the same problem with the Begi S. Corky tried to help me and said that he would check one of his own gt2554 and call me back. He never did, I ended up porting the turbo myself as I cant afford to not having a running car for a month waiting for them to port it.
Now that it's ported it wont boost creep as much, only when it's cold weather
90turboMX5 is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Project Gemini - Turbo Civic on the Cheap Full_Tilt_Boogie Build Threads 57 07-19-2017 05:11 PM
LucaCarMods's Boosted Dutch Miata Build! LucaCarMods Build Threads 11 02-14-2016 07:13 AM
Going back to stock. Need some 1.6 parts. Trent WTB 2 10-01-2015 01:15 PM
Bad head gasket or ? shooterschmidty Engine Performance 8 09-30-2015 11:28 PM


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 05:39 AM.