Inconsistent boost, trouble hitting targets

drfrink24 · 09-26-2005, 09:16 PM

I've been trying to hit 18.5 (or more) PSI in the midrange. After logging over the past few weeks, bumping up low/high WDGC, I've seen nothing consistent but the actual reported WGDC, the relative boost will be different on different runs.

For example, at 4000 RPM, I'll see maybe 16.5 PSI on one run, and 18.42 on the next. Its so inconsistent, that my butt dyno actually detects when I'm not hitting targets. What more confusing is that some of my strongest runs (boost wise), had a WGDC that was 10% lower than what I was logging tonite.

Not like its warm out here either, it was 51 degrees out tonite, probably the coolest I've been in before.

85% WGDC at 4000 RPM is netting me only 17.55...

What I'm wondering is how much WGDC is reasonable, is it pretty much 95% or less?

In addition, if I've hit 18.42 (could be higher) at 4000 RPM in the past, with only 75% WGDC (warmer conditions even), am I all of a sudden going to spike to 21 PSI at some unpredictable point in time?

Anyone have any advice here?

jays05 · 09-27-2005, 03:51 AM

Boost leak? Mine was leaking on the connection between the IC and throttle body (on the TB side). I slapped some huge t-bolt clamps on there and the leak went away... I had to retune boost and fuel all over again!

**Siegel Racing** · 09-27-2005, 05:44 AM

Yep, check for boost leaks...

SS

drfrink24 · 09-27-2005, 08:04 AM

Its never been strong boost wise, I've never creeped at AP Stg 2, even in -20 degree weather. In fact, even at stg 1 and 2 AP (w/o headers), I rarely was seeing 16lbs on my stock boost gauge.

When I installed my Borla headers, I was unable to get a new up-pipe gasket from the dealership. I used steel wool to cleanup the old one, but I did use new ones for the block side. Its an easy install, maybe I'll recheck that one...

Wouldn't a boost leak just have less boost overall? How would I be able to hit 18.42 on one run, and then not on another? Maybe that is the pure definition of a leak?

Xman · 09-27-2005, 08:14 AM

check the IC hoses, especially to the TB. These tend to hold up to a certain level and then release pressure without making a whole lot of noise like an up pipe leak. You would most likely hear an up pipe leak since it tends to make a loud whisting sound.

If you have't changed over the IC to TB hose to a longer silicone piece, now might be a good time. Some better quality clamps couldn't hurt either.

jays05 · 09-27-2005, 08:23 AM

Here's a pic of the T-Bolt clamps I added to fix my boost leak... They are 3.15" I believe, and I paid about $3 each at NAPA for them. They look pretty cool too, and there is no way that hose is going anywhere now.

drfrink24 · 09-27-2005, 09:17 AM

Quote:

Originally Posted by Xman

check the IC hoses, especially to the TB. These tend to hold up to a certain level and then release pressure without making a whole lot of noise like an up pipe leak. You would most likely hear an up pipe leak since it tends to make a loud whisting sound.

If you have't changed over the IC to TB hose to a longer silicone piece, now might be a good time. Some better quality clamps couldn't hurt either.

Is there a common part number or something to look for on this longer silicone piece? Whats the ID and OD of the pipe? 3" basically?

Xman · 09-27-2005, 09:40 AM

They are approx 3" inside diameter (the TB is about 2/75"OC) and 2" long. Most online shops carry them from Samco or Perrin but you can also find them at local shops that sell silicone hose for much less.

**WolfPlayer** · 09-27-2005, 05:09 PM

Everything you need to know about getting a better Throttle Body hose

http://www.bescaredracing.com/sti/in...tlebody/samco/

... I have too many pictures on my site - lol.

t

STirish · 09-27-2005, 06:40 PM

Does you TBB still fit this close to the TB as shown in this picture? The stocker seems to pull back slightly.

Rob

drfrink24 · 09-27-2005, 07:43 PM

Quote:

Originally Posted by STirish

Does you TBB still fit this close to the TB as shown in this picture? The stocker seems to pull back slightly.

Rob

No, mine is slightly away from the tab on the non intercooler side. I've also notice quite a bit of crud collecting by that denso plug, in the recess of the TB area, see leakTB.jpg below. I suppose that might indicate something is amiss...

In addition, could anyone tell me if this also appears to be a slight leak in the crotch of the header flange to block? You can see where its become black, and there is exhaust residue on the block itself which wipes off (as you can see my finger mark).

Xman · 09-27-2005, 08:36 PM

yeah, that looks like a small exhaust leak. When you get a chance you should replace that gasket and properly torque it.

The IC hose looks like it might be leaking a bit. When you tighten those clamps use an 8mm socket on an extension rather than a screwdriver. You'll get it much tighter without slipping.

drfrink24 · 09-28-2005, 08:28 AM

This is so confusing though. I have over 85 logs that I reviewed last night, just looking at WDGC and relative boost pressure reported. I had problems in the past, and an ECU reset fixed it, but, not this time.

Looking over the logs, I can see when I was having really low boost, as in, barely hitting 15.5 PSI in 4th/5th. The very next day of logging, after resetting my ECU, Boost was back up to 18.5 in range with WGDC being as low as 70%. It seems that I've got the same pattern happening again.. Good boost that tapers lower and lower until I reset the ECU. What bugs me is that as boost goes down, my WDGC being reported is going up.

I'm going to re-tighten the clamps, and do a hard reset of the ECU, and then monitor the situation.

Oh, one more thing.. I'm doing all my tuning to realtime maps. Now that I'm comfortable with my ignition and fuel, maybe I should change the basemap to my realtime. I'm currently running stage2v1.04 as my basemap...

Xman · 09-28-2005, 11:33 AM

the relationship of WGDC and lower boost makes total sense. As the WGDC increases that means the WG is open more.

Keep digging into your tuning as it seems something is working against you there.

drfrink24 · 09-28-2005, 12:52 PM

Quote:

Originally Posted by Xman

the relationship of WGDC and lower boost makes total sense. As the WGDC increases that means the WG is open more.

Keep digging into your tuning as it seems something is working against you there.

My understanding is just the opposite. WDGC is the percentage of pressure being blead (sp?) off from the wastegate actuator, thus, keeping the acuator closed, and, producing more boost. 0% WDGC would mean the wastegate actuator sees full pressure, and is 100% open. 100% WDGC would mean the wastegate actuator is not getting any pressure, thus, it cannot actuate, and is 100% closed.

Thats why an increase in WDGC and a decrease in relative boost is not making sense.

09-26-2005, 09:16 PM	#1
drfrink24 Junior STI Driver Car: JBP 04 WRX STi Posts: 197 IWSTI Addict since: May 2004 Trader Rating: (0)	Inconsistent boost, trouble hitting targets I've been trying to hit 18.5 (or more) PSI in the midrange. After logging over the past few weeks, bumping up low/high WDGC, I've seen nothing consistent but the actual reported WGDC, the relative boost will be different on different runs. For example, at 4000 RPM, I'll see maybe 16.5 PSI on one run, and 18.42 on the next. Its so inconsistent, that my butt dyno actually detects when I'm not hitting targets. What more confusing is that some of my strongest runs (boost wise), had a WGDC that was 10% lower than what I was logging tonite. Not like its warm out here either, it was 51 degrees out tonite, probably the coolest I've been in before. 85% WGDC at 4000 RPM is netting me only 17.55... What I'm wondering is how much WGDC is reasonable, is it pretty much 95% or less? In addition, if I've hit 18.42 (could be higher) at 4000 RPM in the past, with only 75% WGDC (warmer conditions even), am I all of a sudden going to spike to 21 PSI at some unpredictable point in time? Anyone have any advice here? This ad is not endorsed by this member. Please register or login to hide this ad.

09-28-2005, 08:28 AM	#13
drfrink24 Junior STI Driver Car: JBP 04 WRX STi Posts: 197 IWSTI Addict since: May 2004 Trader Rating: (0)	This is so confusing though. I have over 85 logs that I reviewed last night, just looking at WDGC and relative boost pressure reported. I had problems in the past, and an ECU reset fixed it, but, not this time. Looking over the logs, I can see when I was having really low boost, as in, barely hitting 15.5 PSI in 4th/5th. The very next day of logging, after resetting my ECU, Boost was back up to 18.5 in range with WGDC being as low as 70%. It seems that I've got the same pattern happening again.. Good boost that tapers lower and lower until I reset the ECU. What bugs me is that as boost goes down, my WDGC being reported is going up. I'm going to re-tighten the clamps, and do a hard reset of the ECU, and then monitor the situation. Oh, one more thing.. I'm doing all my tuning to realtime maps. Now that I'm comfortable with my ignition and fuel, maybe I should change the basemap to my realtime. I'm currently running stage2v1.04 as my basemap... Last edited by drfrink24; 09-28-2005 at 08:34 AM.

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09-27-2005, 03:51 AM	#2
jays05 Spec C Club Car: Blue 05 STI Fav Mod: 4th gear wheelspin Location: Upstate NY Posts: 2,095 IWSTI Addict since: Nov 2004 Trader Rating: (0)	Boost leak? Mine was leaking on the connection between the IC and throttle body (on the TB side). I slapped some huge t-bolt clamps on there and the leak went away... I had to retune boost and fuel all over again!

09-27-2005, 05:44 AM	#3
Siegel Racing Authorized Vendor Car: Your STi ;) Fav Mod: Everything Location: Atlanta Posts: 1,330 IWSTI Addict since: Mar 2005 Trader Rating: (2)	Yep, check for boost leaks... SS

09-27-2005, 08:04 AM	#4
drfrink24 Junior STI Driver Car: JBP 04 WRX STi Posts: 197 IWSTI Addict since: May 2004 Trader Rating: (0)	Its never been strong boost wise, I've never creeped at AP Stg 2, even in -20 degree weather. In fact, even at stg 1 and 2 AP (w/o headers), I rarely was seeing 16lbs on my stock boost gauge. When I installed my Borla headers, I was unable to get a new up-pipe gasket from the dealership. I used steel wool to cleanup the old one, but I did use new ones for the block side. Its an easy install, maybe I'll recheck that one... Wouldn't a boost leak just have less boost overall? How would I be able to hit 18.42 on one run, and then not on another? Maybe that is the pure definition of a leak?

09-27-2005, 08:14 AM	#5
Xman S204 Racer Car: Blue 2004 STi Fav Mod: 2001 2.5RS Rally car... Location: Rancho Santa Margarita, C Posts: 2,822 IWSTI Addict since: Apr 2003 Trader Rating: (3)	check the IC hoses, especially to the TB. These tend to hold up to a certain level and then release pressure without making a whole lot of noise like an up pipe leak. You would most likely hear an up pipe leak since it tends to make a loud whisting sound. If you have't changed over the IC to TB hose to a longer silicone piece, now might be a good time. Some better quality clamps couldn't hurt either.

09-27-2005, 08:23 AM	#6
jays05 Spec C Club Car: Blue 05 STI Fav Mod: 4th gear wheelspin Location: Upstate NY Posts: 2,095 IWSTI Addict since: Nov 2004 Trader Rating: (0)	Here's a pic of the T-Bolt clamps I added to fix my boost leak... They are 3.15" I believe, and I paid about $3 each at NAPA for them. They look pretty cool too, and there is no way that hose is going anywhere now.

09-27-2005, 09:40 AM	#8
Xman S204 Racer Car: Blue 2004 STi Fav Mod: 2001 2.5RS Rally car... Location: Rancho Santa Margarita, C Posts: 2,822 IWSTI Addict since: Apr 2003 Trader Rating: (3)	They are approx 3" inside diameter (the TB is about 2/75"OC) and 2" long. Most online shops carry them from Samco or Perrin but you can also find them at local shops that sell silicone hose for much less.

09-27-2005, 05:09 PM	#9
WolfPlayer Moderator & ECU Tech Car: 05 CGM STI Fav Mod: mo boostaz Location: Fredneck, MD Posts: 3,759 IWSTI Addict since: Jun 2004 Trader Rating: (6)	Everything you need to know about getting a better Throttle Body hose http://www.bescaredracing.com/sti/in...tlebody/samco/ ... I have too many pictures on my site - lol. t

09-27-2005, 06:40 PM	#10
STirish Spec C Club Car: '99 M3/'03 WRX Avant Fav Mod: Modification is wrong! Location: SLC, UT Posts: 1,026 IWSTI Addict since: Sep 2004 Trader Rating: (6)	Does you TBB still fit this close to the TB as shown in this picture? The stocker seems to pull back slightly. Rob

09-27-2005, 08:36 PM	#12
Xman S204 Racer Car: Blue 2004 STi Fav Mod: 2001 2.5RS Rally car... Location: Rancho Santa Margarita, C Posts: 2,822 IWSTI Addict since: Apr 2003 Trader Rating: (3)	yeah, that looks like a small exhaust leak. When you get a chance you should replace that gasket and properly torque it. The IC hose looks like it might be leaking a bit. When you tighten those clamps use an 8mm socket on an extension rather than a screwdriver. You'll get it much tighter without slipping.

09-28-2005, 11:33 AM	#14
Xman S204 Racer Car: Blue 2004 STi Fav Mod: 2001 2.5RS Rally car... Location: Rancho Santa Margarita, C Posts: 2,822 IWSTI Addict since: Apr 2003 Trader Rating: (3)	the relationship of WGDC and lower boost makes total sense. As the WGDC increases that means the WG is open more. Keep digging into your tuning as it seems something is working against you there.