Boost droping at high RPM, greddy - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Prefabbed Turbo Kits A place to discuss prefabricated turbo kits on the market
Sponsored by:
Sponsored by:

Reply
 
 
 
LinkBack Thread Tools
Old 09-27-2008, 05:31 AM   #1
Junior Member
Thread Starter
 
Join Date: Jul 2008
Location: San Antonio, TX
Posts: 65
Total Cats: 0
Default Boost droping at high RPM, greddy

some specs,
1990 1.6
new act hd clutch
greddy kit running an fmu with the following additons and upgrades

turbo clocked down
FMIC and 2.5in piping
Ebay purple BOV recirculated to intake
ball&spring manual boost controler
Boost set to about 6-7psi
No ac or power steering

Car will reach full boost with out a problem at about 4k( stock exhaust) as i start to go over 5k the psi steadily drops. will drop to 2psi sometimes less sometimes more.

what are some ways to diagonosis this problem, its a real burden as this is the autox car and boos starts to fade right when it motor starts to make power.

Last edited by climb_on; 09-27-2008 at 04:55 PM.
climb_on is offline   Reply With Quote
Old 09-27-2008, 05:50 AM   #2
Senior Member
iTrader: (8)
 
turbobluemiata's Avatar
 
Join Date: Aug 2006
Location: Springfield, IL
Posts: 1,019
Total Cats: 0
Default

search "helper spring" or greddy wastegate their know to suck and need a helper spring to hold boost to redline
turbobluemiata is offline   Reply With Quote
Old 09-27-2008, 08:50 AM   #3
:(
iTrader: (7)
 
Join Date: Jul 2006
Location: nowhere
Posts: 8,281
Total Cats: 2
Default

ive seen this on mycar when the compressor was leaking.
magnamx-5 is offline   Reply With Quote
Old 09-27-2008, 04:54 PM   #4
Junior Member
Thread Starter
 
Join Date: Jul 2008
Location: San Antonio, TX
Posts: 65
Total Cats: 0
Default

Quote:
Originally Posted by turbobluemiata View Post
search "helper spring" or greddy wastegate their know to suck and need a helper spring to hold boost to redline
i'll look into that...

magna where was your compressor leaking at?
climb_on is offline   Reply With Quote
Old 09-27-2008, 06:08 PM   #5
Junior Member
iTrader: (1)
 
Join Date: Oct 2004
Location: Haarlem ,the Netherlands
Posts: 453
Total Cats: 0
Default

Check for a boost leak. Or a non closing bov... It can appear to be sealed and leak on pressure. Check all ic conections.

A stock greddy set should be able to make 6 psi with oem exhaust all the way to redline.
greddymx5 is offline   Reply With Quote
Old 09-28-2008, 12:52 PM   #6
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,317
Total Cats: 1,914
Default

Remove the rubber hose connecting the wastegate can to the compressor. Block the compressor outlet with a plug. Install a nipple in the pipe between the intercooler and the throttle body, and run a new hose from this nipple to the WG can.
Joe Perez is offline   Reply With Quote
Old 09-28-2008, 05:05 PM   #7
Senior Member
iTrader: (5)
 
Join Date: Dec 2007
Location: worcester ma
Posts: 1,124
Total Cats: 0
Default

the ebay bov;s leak,, buy a real one
urgaynknowit is offline   Reply With Quote
Old 09-28-2008, 05:54 PM   #8
Junior Member
 
Join Date: Aug 2007
Location: England
Posts: 124
Total Cats: 0
Default

you have a manual boost controller? tried running without the MBC fitted?
jim-NA is offline   Reply With Quote
Old 09-28-2008, 07:00 PM   #9
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,317
Total Cats: 1,914
Default

Quote:
Originally Posted by urgaynknowit View Post
the ebay bov;s leak,, buy a real one
I disagree.

All BOVs purchased from any eBay vendor are completely reliable and trouble-free. I base this upon my experience of having purchased one BOV from one vendor, said BOV now being two years old and still working perfectly.
Joe Perez is offline   Reply With Quote
Old 09-28-2008, 09:01 PM   #10
Junior Member
Thread Starter
 
Join Date: Jul 2008
Location: San Antonio, TX
Posts: 65
Total Cats: 0
Default

could this just be the common case of the greddy wg
(helper spring)
climb_on is offline   Reply With Quote
Old 09-28-2008, 10:16 PM   #11
Elite Member
iTrader: (9)
 
Join Date: Aug 2006
Location: Concord, North Carolina
Posts: 4,173
Total Cats: 5
Default

Quote:
Originally Posted by Joe Perez View Post
Remove the rubber hose connecting the wastegate can to the compressor. Block the compressor outlet with a plug. Install a nipple in the pipe between the intercooler and the throttle body, and run a new hose from this nipple to the WG can.
Why do you do this Joe?
miatamania 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
My solution for Oiltemp and Oilpressure input into Megasuirt (MS3) Zaphod MEGAsquirt 41 01-24-2016 01:25 PM
Going back to stock. Need some 1.6 parts. Trent WTB 2 10-01-2015 01:15 PM
01-05 Fab9 PNP COPs (used) FrankB Miata parts for sale/trade 6 09-30-2015 12:48 PM
Are my coils failing? viriiguy General Miata Chat 5 09-28-2015 08:39 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 09:16 AM.