Notices
Evo Engine / Turbo / Drivetrain Everything from engine management to the best clutch and flywheel.

Why does my boost peak, then taper off?

Thread Tools
 
Search this Thread
 
Old Jul 24, 2008, 09:35 AM
  #16  
Evolved Member
iTrader: (26)
 
Wicked E's Avatar
 
Join Date: Oct 2007
Location: Colorado Springs, CO
Posts: 1,989
Likes: 0
Received 0 Likes on 0 Posts
Autometer does NOT equal "real gauge". That's funny...

-E
Old Jul 24, 2008, 09:58 AM
  #17  
Evolved Member
iTrader: (17)
 
Ludikraut's Avatar
 
Join Date: Apr 2004
Location: 41° 59' N, 87° 54' W
Posts: 6,224
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by garcia10
26 psi is alot.........i would turn it down a bit or something will probably blow if its not tuned for that much boost....also....you arent extremely modded...theres no reason the boost should be up that high.....i noticed you are in flordia....take it to ttp....have them tune you back to something more safe and reliable....in the meantime..turn the boost down to stock...another theory could be maybe a salesman took it home for a weekend and "tinkered" with it...maybe saw the boost controller and turned it up not knowing what he was doing....but than again...its just a theory
Best advice in this thread. Take it to TTP and have them checkout the car and the tune. It's not worth taking a chance on.

Autometer FTL.

l8r)
Old Jul 24, 2008, 10:53 AM
  #18  
Evolved Member
 
crcain's Avatar
 
Join Date: Oct 2002
Posts: 2,788
Likes: 0
Received 1 Like on 1 Post
The boost tapers because exhaust backpressure in the turbine housing forces the internal wastegate flap open. The spring pressure on the actuator is not strong enough to hold it open.

Larger turbos don't really have the problem because they use larger turbine housings therefore less back pressure. Problem with larger turbo is the boost threshold is greater.

I tried getting the stock 9 turbo to taper less by installing an uprated actuator on my friends Evo 6 which runs 11.5. We did datalogs before and after and the uprated actuator could only hold boost just a tiny bit better. Not a big difference at all. It still tapered.

Some say you can do ECU based boost control which I think is closed loop and this helps taper. I'm not so sure this I think would probably help a bit although I'm not sure how much.

As for spiking 1.8 bar, I'd take your car to a reputable shop and have it confirmed the car is indeed mapped to run that boost level safely.
Old Jul 24, 2008, 11:20 AM
  #19  
Evolving Member
Thread Starter
iTrader: (4)
 
rd122481's Avatar
 
Join Date: Jul 2008
Location: Florida
Posts: 122
Received 0 Likes on 0 Posts
Well, I took the car out today to run some errands & had my gf with me & she watched the gauge & it may have spiked to 1.6 bar @ the most. When I check the gauge initially, it was EARLY in the a.m. & therefore alot cooler outside. Apparently this must make a difference (Duh...colder air = more dense air ). As for the car having a tune already...how would I know? Like I said, I'd bet $$$ that the car doesn't have a cat & it's not throwing any codes...does that mean it was probably tuned? It was owned by a Trinidadian fellow by the name of Deryk in Miami/Hollywood area. I was told he used to be on the forum under the name of Dr. Evo or Dr Evo or something like that.
Old Jul 24, 2008, 11:25 AM
  #20  
Evolved Member
iTrader: (17)
 
Ludikraut's Avatar
 
Join Date: Apr 2004
Location: 41° 59' N, 87° 54' W
Posts: 6,224
Likes: 0
Received 0 Likes on 0 Posts
You can either:

a.) go over into the ECUflash section, educate yourself on how to extract the ROM from your ECU and post it for everyone to look at

OR

b.) Take it to TTP, who in about 5 minutes can tell you whether you have a tune on the car and if it's any good.

l8r)
Old Jul 24, 2008, 04:29 PM
  #21  
Evolved Member
iTrader: (4)
 
holler mcdollar's Avatar
 
Join Date: Jun 2007
Location: ne phila
Posts: 522
Likes: 0
Received 0 Likes on 0 Posts
lol @ autometer a "real" boost gauge.

but yes, it's been said. either turn the boost down or verify somewhere that it was tuned for that amount.

the joy of buying a used evo, huh?
Old Jul 24, 2008, 07:50 PM
  #22  
Evolved Member
iTrader: (41)
 
heel2toe's Avatar
 
Join Date: Jul 2007
Location: Massachusetts
Posts: 4,690
Received 126 Likes on 121 Posts
put your car in first gear on a level surface and rev it. I believe the factory 2 step is set to 5000rpm(it is on an 05) so if its anything higher then its been tuned
Old Jul 24, 2008, 08:13 PM
  #23  
Evolving Member
Thread Starter
iTrader: (4)
 
rd122481's Avatar
 
Join Date: Jul 2008
Location: Florida
Posts: 122
Received 0 Likes on 0 Posts
Heeltoe...funny thing you said that! I remembered that the IX had a 2 step built in @ 5k rpm & decided to try it when I took my friend for a ride earlier in the evening. The car must've been tuned! The 2 step is set @ 5500rpm & the car definitely has an offroad pipe bolted in & it's not throwing codes. Why do you guys say Autometer isn't a real boost gauge? I thought they made quality stuff. Am I wrong? Sure hope not...
Old Jul 25, 2008, 06:33 AM
  #24  
Evolved Member
iTrader: (42)
 
neonglh's Avatar
 
Join Date: Jul 2008
Location: East Coast
Posts: 924
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by evoPirate
The stock frame 16g in any flavor, be it stock, tme, grren, white, red, bbk....they all taper. Its just the nature of the beast.
+1 Turbo characteristics make this happen. Many factors do it. Sometimes a stronger WGA can help hold it longer, but what happens often with smaller turbos is the engine starts to out-flow the turbo, and it can no longer hold that much boost. On a neon srt4, rt-ernie welded the WG shut, so it was ALL going through the turbo, and it still only made ~ 30 psi up top.

--mark
Old Jul 25, 2008, 09:19 AM
  #25  
Evolved Member
iTrader: (6)
 
Warrtalon's Avatar
 
Join Date: Jun 2004
Location: Long Island, NY
Posts: 20,790
Likes: 0
Received 2 Likes on 2 Posts
Stop posting these same questions over and over, then go outside, turn your boost down, and make an appointment with a local tuner. The more you keep boosting it at such high boost levels, the more likely you are to damage something.
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
durjana
Evo Engine / Turbo / Drivetrain
15
Aug 30, 2012 08:44 AM
Tractionlimit
Evo X Engine Management / Tuning Forums
8
Sep 16, 2009 07:57 AM
fkw958
Water / Methanol Injection / Nitrous Oxide
6
Nov 25, 2007 07:14 PM
Atlmethevo
ECU Flash
64
Mar 19, 2007 06:02 PM
Warrtalon
Evo Engine / Turbo / Drivetrain
55
Jan 17, 2006 09:28 PM



Quick Reply: Why does my boost peak, then taper off?



All times are GMT -7. The time now is 08:19 AM.