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overboosting after exhaust install?

So my car appears to be overboosting to 0.95 to 0.99bar after Fri's install of my Rarlyl8 dual outlet exhaust and WG stub pipe. Is this possible?

It's odd as my GReddy Profec B Spec II EBC is set to limit boost to 0.8bar max. How'd this suddenly get over ridden?

I went to double check the settings but now somehow cannot find that setting in its options - it's sort of a complicated unit and I'm not dat smaht. Used to just push option button and max boost would be displayed but not anymore. Have the billion page manual, will have to check I guess.

But why after exhaust install? The sound is *awesome* btw muwahahahahahaaa. But overboost is not 8-). I'll post up pics later, I'm def. psyched.

Oh also, unrelated - with the install, for now my buddy plugged my aux air pump with a large bolt, until I can source the injector dummy plugs. I thought that odd w/o disabling the pump to just plug it but he assured me I'm OK. Thoughts?
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Paul... CT | '87 930 | '07 //S6 v10 JNR | '98 ///M3 vert |
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| '01 ///M5 | '96 993 C2 cab | '05 S600 Sport - biturbo V12@Just Not Right 495rwhp / 612rwtq |
| '58 TR3A | '01 //S8 | '95 //S6 6gang | '88 ///M5 | '87 190E 2.3-16 |
Old 06-22-2008, 05:57 AM
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Your engine's ability to exhale is now maximized and your waste gate is over exited, ha!

I am not familiar with the operation of various boost controllers. What has changed is back pressure. There is now less back pressure on both the turbo and the waste gate valve. This could affect the boost signal.

The drive belt should be removed from the air pump.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 06-22-2008, 07:37 AM
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Yes, cold weather w/ the Zork my car will overboost in all gears, including 4th at around 115-120. this is w/ a .8 spring. In the warm weather (50F+) not an issue. In the cold the car will just cutout as I overboost. I went on a run with the 993 TT guys in March (40F+-) and I was babying the throttle to avoid OB. Since then, 2 trips to the track in warmer weather and not 1 incident of OB.

I think the more mods you have, headers, intercooler, intake, zork the easier it is. The WG just can't keep up.
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1987 930 - K27 7200 / DAS Full Cage / Blownsix Intercooler / BB Headers / Zork Tube / Tial 46mm / Adjustable WUR / RPM Activated Solenoid / Open Element Air Intake / Smart Racing 27mm Sways / 24 and 33mm Torsion Bars / Adj. Spring Plates / Wevo Strut Brace / Monoballs / Tow Hooks / Oil Cooler Scoop / Brey Krauss Harness Truss / Race Seats / XD-16 AFR Guage/ 17" Kodiak Racing Whees and Nitto NT-01 255/315s

Last edited by F350Lawman; 06-22-2008 at 08:03 AM..
Old 06-22-2008, 07:58 AM
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Your turbo is working better now, thanks to the rear muffler. This is likely to be why your overboosting.

I don't know how your ebc works, but when you adjust/set mine it has nothing to do with boost levels at all. It's called gain and ratio. The only thing you set as boost levels is the safety boost retard feature. You enter a figure and if this is reached the gain and ratio changes to what ever you set it at it.
The spring works according to boost pressure and this works better than that.

A snippet...

The Blitz unit offers two levels of adjustment: Gain and Ratio. Gain controls the overall boost response by constantly modifiying the pressure coming from the actuator into the wastegate. Ratio controls the boost curve by adjusting how quickly and when the wastegate is allowed to open. Ratio also affects your maximum boost.

GAIN
To enter Gain Set mode, press and hold the MODE button for at least two seconds. The unit will beep and you will see "1234M" flash on the display. The default gain is 5. Set the value by turning the volume knob. You can adjust the value anywhere from 0 to 100. Be very careful with gain, as setting it too high could cause overboosts leading to engine damage and possibly detonation.
I spoke with Blitz and the gain setting is intended to compensate for the varying spring stiffnesses of external wastegates.
RATIO
You can program four different ratios into the DSBC at one time. This allows you to switch boost curves "on the fly", somewhat useful, in the sense of city and highway modes. To set a ratio, first select a channel by turning the mode knob until you see either 1, 2, 3, or 4 on the display. When you've selected your desired channel, press the mode button once. The channel number will begin to blink and you are in Ratio Set mode. Press the volume button until the words "boost" or "peak" do not appear. A number will appear in the main display area; by default all channels are set to 0. Turn the volume button to adjust the value. The value can be anywhere between 0 and 100.
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg

Last edited by NathanUK; 06-22-2008 at 09:44 AM..
Old 06-22-2008, 09:38 AM
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You guys are great - thanks for the insight. Makes sense, but hearing it from youses always gives me the warm fuzzies 8-).

Yes my EBC has a boost setting as well - you can dial in the exact bar you want as max. What's odd is how that 'feature' has disappeared from my screen scroll suddenly. Like I said I have to dig out the 10000000 page manual.

I'm scared to F with it too much as I don't fully understand all the gain / ratio etc'ness of it all - tho your snippet Nathan was beneficial somewhat to me ignoramus.

When I set the EBC with my mechanic we settled @ 0.8bar as we could def. hear detonation @ 0.9. Now all I hear is... well... MUSIC. Hard to hear anything above the bliss heh heh. Either it's there @ 0.9 still and I just don't hear it - or - the decreased backpressure has allowed it to now run 0.9. Which would kick *ARSE* as the pull is otherworldly.

Thanks for the Batphone convo Fri. night Brian - that was helpful. I spent about 2hrs last night fine tuning the outlet angles, etc. What a PITA heh heh. My passenger outlet looks like it could be 1/2 further right not sure what I can do there. Anyway, it looks awesome - and sounds AMAZING. Now I see what yous alls been talkin about regarding open WG dump sound. Wow!

Tx again all. Pics to follow 8-)...
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Paul... CT | '87 930 | '07 //S6 v10 JNR | '98 ///M3 vert |
past:

| '01 ///M5 | '96 993 C2 cab | '05 S600 Sport - biturbo V12@Just Not Right 495rwhp / 612rwtq |
| '58 TR3A | '01 //S8 | '95 //S6 6gang | '88 ///M5 | '87 190E 2.3-16 |
Old 06-22-2008, 10:41 AM
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Are you sure that max boost setting is not what I called the "safety boost retard feature".

On mine you preset the max boost you want but as an alarm/safety feature.
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg
Old 06-22-2008, 02:10 PM
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Both driver and passenger tailpipes are adjustable in and out. If the passenger's side is maxed out you can pull in the driver's in side to match it. Niether side was designed to stick out past the bumper.
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Old 06-22-2008, 08:42 PM
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Nathan-

Yes, the GReddy unit has both those settings - boost select and max boost warning. The warning's set to coincide with the fuel cutout @ 1.20bar. The shop that did the install for the PO programmed it. I'll likely take it back to them to redial it back in - once I get my rear end lowered it's going to them for an alignment anyways 8-).

With the reduced backpressure I wonder if I'm OK running @ 0.9 to 0.99bar? I forget, isn't every .1bar something like 30hp? I know I heard something to that extent somewheres. Sure does feel good, just don't want to stress it.

Brian-

Thanks. I may have to shift my entire system over then somehow, as the driver side is as far 'in' as I could get it, and the pass side is as far 'out' w/o falling off heh heh. Like I said it's maybe 1/2 inch. It does look good - and sound OMG GOOD heh heh. The poppitty popopop on decel is downright giggle inducing...
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Old 06-23-2008, 06:11 AM
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The back pressure won't make any difference. 1 bar of boost is still 1 bar of boost, okay its also 2 bar absolute
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg
Old 06-23-2008, 12:30 PM
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First of all: I don't think you shouldn't hear detonation at 0.9 bar in otherwise healthy 930, at least not if using quality fuel.

Second: the reason that boost went up after muffler install is that backpressure after turbo is lessened. Exhaust gases will take the path of least resistance. If backpressure going into turbo is high, more gases will try to escape trough wastegate and you'll need harder spring. Is backpressure is lower, bigger portion of gases will go trough turbo and boost will go up unless spring tension on wastegate is lowered. This is the case with simple non-EBC installation where plenum pressure actuates the wastegate directly. As long as spring-pressure in wastegate is preset to give lower boost than you want to acheve with EBC, things are OK. This is called "base boost". EBC will only allow you to get boost higher than base boost. It cannot reduce the boost below basic spring-tension boost.

In your case, I suspect you are using OEM 0.7 bar boost spring with EBC set for 0.8 bar. This worked before and EBC only had to vent enough air from singnal line going to wastegate to achieve extra 0.1 bar.

Once you installed free flowing exhaust, I suspect your base boost went up to 0.9 bar. Thus, your 0.8 bar EBC configuration is overriden by spring tension and EBC is out of the loop and just hanging on for a ride. It cannot control the boost anymore unless you ask it to boost more than (you new) base boost.

To test for this, disconnect EBC completly and run the wastegate directly from plenum. Note the boost. That boost will be your base boost and you EBC will only be able to raise it, not lower it. If your base boost is 0.9 bar, you will need to install softer spring in the wastegate in order to restore EBC authority over boost.

I suggest using base boost that is at least 0.2 bar lower than target EBC boost, otherwise EBC won't be able to control boost in stable manner.

With other words, pick a spring that gives you 0.6 bar of base boost if you want EBC to hold 0.8 bar of boost and higher.

Is my explanation too complicated?

Regards,
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Last edited by beepbeep; 06-23-2008 at 02:49 PM..
Old 06-23-2008, 02:47 PM
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Goran, I thought your post was good.

Just a query. Are all ebc's plumbed the same? Are the majority plumbed in series with the WG or are the majority vented back on to the WG using a tee piece like RUF did with their regulator/diaphragm?
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG.
Fitting - New service kit.
Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head.

1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods.
Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit.

http://www.danasoft.com/sig/Iamnotanumber.jpg
Old 06-23-2008, 03:09 PM
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There are two common ways to controll boost. Usual OEM approach is "bleed" approach where signal line to wastegate is bled off with pulse-width modulated valve and vent hose (if existing) is left as it is. This is stock way and used on all internal-wastegate cars (and I don't believe there are any externally-wastegated cars in production nowadays)

The other "bling" way is to leave signal line as it is (connected to plenum) and then regulate the boost by applying pressure trough wastegate vent hose...controlling the valve by differential pressure (also regulated by PWM bleed valve). This should in theory lessen boost creep. But you still cannot reduce boost below base spring-controlled boost.

It doesn't matter which approach he used. As soon as mechanically controlled spring-tension base boost is higher than EBC-configured boost, EBC is just dangling there without a posibility to do something about it.
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Old 06-23-2008, 03:45 PM
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Goran-

Thanks very much for taking the time to spell that out for me. It was very clear, have heard it before but you hand held me through it greatly. Much appreciated, while I had heard the explanation I was not smaht enough to apply it to my situation. Thick, I am.

Gotchya - need softer spring to bring EBC back online. Where to source? Suggested spring considering my circumstance? I do like the comfort / flexibility afforded by the EBC doing its job.

However - I also do like this power I'm feeling 8-).

Regarding detonation, we only get crap 93 fuel here and I was def. detonating @ 0.9bar. My timing is advanced - don't know to what, just see my dizzy fully clocked. My recent dyno run (pre-exhaust) showed good AFR's and really great curves, so she's running strong and tight:
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| '58 TR3A | '01 //S8 | '95 //S6 6gang | '88 ///M5 | '87 190E 2.3-16 |
Old 06-24-2008, 06:18 AM
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You need to get your timing in line or you will be destroying your engine in no time.
Everything gets effected by boost increase.....if you up the boost you may have to retard timing to prevent detonation. Of course power will drop accordingly but the overall gain should be positive.
Have the dyno guy check your timing with a light. This should be easy to do during a pull to see how much boost retard your getting with your dizzy....perhaps this is not hooked up or working?
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Old 06-24-2008, 08:57 AM
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Paul - the entire system can be shifted horizontally at the muffler outlet to 180 connection. There is about an inch or so of telescopic travel built into that slip joint.
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Old 06-24-2008, 01:52 PM
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Quote:
Originally Posted by RarlyL8 View Post
Paul - the entire system can be shifted horizontally at the muffler outlet to 180 connection. There is about an inch or so of telescopic travel built into that slip joint.
Great thanks Brian - I figured as much and that was going to be the first place I looked. Any tips on getting that sucker to move? Once it's on there, well - it's on there. Do it blazing hot or something?

Appreciate it.

OMG the sound!!! 8-) BOINGoingOINGoingOINGoingOINGoinOING...
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Old 06-25-2008, 06:14 AM
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.95 bar and .99 are virtually the same thing. I would have never noticed it with my gauge. Its not going to hurt anything if you were wondering. If you were getting boost creep where your wastegate cant keep up and you build boost 17- 19 psi, then you have an issue.

My boost can go up a few psi from temp, how many disks I have in the supertrapp etc etc. +/- a few hundreths is nothing.
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Old 06-25-2008, 06:26 AM
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Quote:
Originally Posted by JayG View Post
.95 bar and .99 are virtually the same thing. I would have never noticed it with my gauge. Its not going to hurt anything if you were wondering. If you were getting boost creep where your wastegate cant keep up and you build boost 17- 19 psi, then you have an issue.

My boost can go up a few psi from temp, how many disks I have in the supertrapp etc etc. +/- a few hundreths is nothing.
Appreciate the thought. I was concerned as like I said prior to the exhaust when we tried dialing in 0.9 I could HEAR DETONATION. Can't hear a thing now over the bliss 8-). Hoping it's not.

I can see 0.95 adn 0.99 as my EBC has a digital boost gauge as well - so that's how I know. The OE gauge is a joke certainly.
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Old 06-25-2008, 07:04 AM
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Quote:
Originally Posted by krasuskyp View Post
So my car appears to be overboosting to 0.95 to 0.99bar after Fri's install of my Rarlyl8 dual outlet exhaust and WG stub pipe. Is this possible?

It's odd as my GReddy Profec B Spec II EBC is set to limit boost to 0.8bar max. How'd this suddenly get over ridden?

I went to double check the settings but now somehow cannot find that setting in its options - it's sort of a complicated unit and I'm not dat smaht. Used to just push option button and max boost would be displayed but not anymore. Have the billion page manual, will have to check I guess.

But why after exhaust install? The sound is *awesome* btw muwahahahahahaaa. But overboost is not 8-). I'll post up pics later, I'm def. psyched.

Oh also, unrelated - with the install, for now my buddy plugged my aux air pump with a large bolt, until I can source the injector dummy plugs. I thought that odd w/o disabling the pump to just plug it but he assured me I'm OK. Thoughts?
Hi,
Could you describe what you mean by overboost? Is it making "overboost" while you are "in the throttle" or spiking when you lift off the throttle suddenly?
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Old 06-25-2008, 11:01 AM
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It is best to make all the muffler adjustments before the system is heat cycled. The metal becomes less plyable and much harder with heat history (so do not use a torch).
If you wish to move the entire setup to the right you must loosen the main muffler body clamp as well as the driver's side tailpipe clamp. Remove the driver's side tailpipe and then wiggle the 180 bend back and forth to pull it out where you want it. Once that is done you will have to re-adjust everything as it all has been moved. The spacer that the 2 t-bolt clamps use will scratch up the metal when moved around so be mindful of that.
The sound is awesome on these units. Ben and I worked for many months to get it just right.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 06-25-2008, 11:13 AM
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