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Performance Modifications for the NG900 / Old 9-3 This forum contains PERFORMANCE related Q&A's for the NG900 and 9-3. This may also include suspension.

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Old 10-29-2007, 02:16 PM   #1
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T7 Atmospheric BOV FTW

So I had a long talk with my next door neighbor who has a Nissan with a Skyline engine that he just installed. He's got a MAF sensor as well and runs an atmospheric blow-off valve, no problem. If you give the car a little throttle after a pull, while in neutral, or let it simply rev down you can avoid fuel cut. Apparently it takes a bit of time to get accustomed to, but if you really wanted that blow-off sound I suppose this could be a viable option for us T7 owners...
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Old 10-29-2007, 02:23 PM   #2
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Completely different engine management. Just because he also has a MAF, it doesn't mean the engine management is the same.
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Old 10-29-2007, 02:23 PM   #3
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This was tested over at genuinesaab with a dual piston valve, no dice.

also people have tired using those hybriod valves that you can adjust to only dump SOME air and return the rest. NO DICE.

If you actually successfully test this theory on a Saab running t7, then it could become an option... for now I have to say all other attempts at this have failed, sadly.
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Old 10-29-2007, 02:24 PM   #4
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Originally Posted by slspf2 View Post
So I had a long talk with my next door neighbor who has a Nissan with a Skyline engine that he just installed. He's got a MAF sensor as well and runs an atmospheric blow-off valve, no problem. If you give the car a little throttle after a pull, while in neutral, or let it simply rev down you can avoid fuel cut. Apparently it takes a bit of time to get accustomed to, but if you really wanted that blow-off sound I suppose this could be a viable option for us T7 owners...
Not worth $200 for a sound IMHO. Sounds like a lot of work...And that's assuming that the car actually runs right.
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Old 10-29-2007, 02:32 PM   #5
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Not worth $200 for a sound IMHO. Sounds like a lot of work...And that's assuming that the car actually runs right.
Well like I said if you really want that sound then it might be an option. But what exactly has failed when this has been tested at GS? Did it just throw codes?... Or did fuel cut get reached every time?
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Old 10-29-2007, 04:09 PM   #6
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Fuel cut?!?! Uhh, a BOV won't make you hit the boost pressure related fuel cut. What it will do is make the car stall out and throw check engine lights.

My guess is that the skyline has an engine managment system closer to LH2.2 than Trionic 7 or 8.

Its pretty silly to adapt you driving style just to keep a car from dieing when you lift the throttle...just for a whoosh noise.

LOLZ.
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Old 10-29-2007, 04:10 PM   #7
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you can search and find the thread. I don't recall the details, but do know there has been MANY attempts at running a bov on t7 Saabs and they all have failed.
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Old 10-29-2007, 04:43 PM   #8
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OK is it bad that I bring up a question related to this instead of diggin up an old thread?

So my question is, If the maf measures the air, and then you dump some of it to the atmosphere, what is measuring the missing air? ie where is it un accounted for? Is something else checking up?


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Old 10-29-2007, 04:51 PM   #9
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my car is T7 and i went from zero whoosh to decent whoosh just from the GS open intake. is the added sounded really that cool? it's a matter of preference of course, but i find my current setup loud enough.
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Old 10-29-2007, 04:53 PM   #10
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The air was already "counted" by the maf. The machine knows its in the system. When the oxygen sensors read the fuel mix is too rich, it fires the cel.

My understanding of T7 in a nutshell.
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Old 10-29-2007, 04:58 PM   #11
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Originally Posted by Tweek's Turbos View Post
The air was already "counted" by the maf. The machine knows its in the system. When the oxygen sensors read the fuel mix is too rich, it fires the cel.

My understanding of T7 in a nutshell.
thats the basic idea, but also T7 has a MAP sensor and an air temp sensor, so basically it can allready figure out how much airmass its supposed to be getting from those. when it looks at the MAF value and sees that it differs greatly from what it "thinks" it should be, then i would imagine it freaks and throws a CEL. T7 is smart.

Paul
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Old 10-29-2007, 05:54 PM   #12
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http://en.wikipedia.org/wiki/Mass_flow_sensor

quick explanation of airmass above.
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Old 10-29-2007, 06:59 PM   #13
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The air was already "counted" by the maf. The machine knows its in the system. When the oxygen sensors read the fuel mix is too rich, it fires the cel.

My understanding of T7 in a nutshell.
But the BOV would pop when the throttle is shut right? So would the engine go lean when the throttle was opened up again? Where does the air go in the factory set up, it goes back before the compressor right?


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thats the basic idea, but also T7 has a MAP sensor and an air temp sensor, so basically it can allready figure out how much airmass its supposed to be getting from those. when it looks at the MAF value and sees that it differs greatly from what it "thinks" it should be, then i would imagine it freaks and throws a CEL. T7 is smart.

Paul
If this is the case I can see why there is no way around this. The ECU is comparing the two, and flagging if they are different. I just wonder if there is a way to re-introduce the same volume that was vented somehow.

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Old 10-29-2007, 07:09 PM   #14
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Quote:
Originally Posted by Tboy View Post
OK is it bad that I bring up a question related to this instead of diggin up an old thread?

So my question is, If the maf measures the air, and then you dump some of it to the atmosphere, what is measuring the missing air? ie where is it un accounted for? Is something else checking up?


Tboy
No not bad at all to ask. I wish people were not being told constantly to search as asking brings new discussion and ideas even if a question has been beaten to death.

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Originally Posted by Tweek's Turbos View Post
The air was already "counted" by the maf. The machine knows its in the system. When the oxygen sensors read the fuel mix is too rich, it fires the cel.

My understanding of T7 in a nutshell.
T7 is more picky about the a/f ratio it sees from the narrowbands but this isn't the huge factor that says no.

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thats the basic idea, but also T7 has a MAP sensor and an air temp sensor, so basically it can allready figure out how much airmass its supposed to be getting from those. when it looks at the MAF value and sees that it differs greatly from what it "thinks" it should be, then i would imagine it freaks and throws a CEL. T7 is smart.

Paul
DING DING DING. T7 has a "T5" function built into it and its purpose is to perform a.) Final fuel mixture adjustments due to density changes from the air being compressed by the turbo and then cooled through the intercooler b.) To confirm that there isn't a significant amount of air missing that has been metered (don't know what the acceptable % of loss is though).

So when you run a BOV on T7 what it sees is missing air and throws up a red flag and multiple cel codes.

I have written up a couple of short sections on T7 operation theory that range from the guy who had a butchered viggen to regular question of how T7 works. If you search around they will eventually come up.



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Old 10-29-2007, 07:20 PM   #15
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http://en.wikipedia.org/wiki/Mass_flow_sensor

quick explanation of airmass above.
I love wikipedia, it has everything!

...and T5 ftw
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Old 10-29-2007, 07:22 PM   #16
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I really fail to see how all this time, money, and effort is truly worth a little noise. If it is that much of a priority to your modding, you need to turn your attentions toward another platform that can provide you adequate noises to accompany your speed/not-speed. I am quite happy with the noises my GS intake provides me.
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Old 10-29-2007, 08:25 PM   #17
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I really fail to see how all this time, money, and effort is truly worth a little noise. If it is that much of a priority to your modding, you need to turn your attentions toward another platform that can provide you adequate noises to accompany your speed/not-speed. I am quite happy with the noises my GS intake provides me.
Your intake sounds HOT!
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Old 10-29-2007, 08:29 PM   #18
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Yes, I loved my GS intake.

You can "play" it with the gas pedal.
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Old 10-30-2007, 05:12 AM   #19
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I tried both a pure 2 piston dump, the 004 that stays closed at idle and a new style partial dump / recirculate. Both of them worked marginally ok on a stock 9-5 Aero auto.. On a 5 speed with stock power it might be half ok but with any tuned soft or in the summer heat when pressure is higher it was a Fail.. Basically NO! Run a recirc valve.
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2.0 GOOSE 500whp + 8500rpm = 11.06 @125 E85
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Old 10-30-2007, 05:20 AM   #20
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The Forge Motorsport DV offers a different sound than the stocker than and a GS intake is about the extent of what is safe and still "cool" sounding.
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