SaabCentral Forums banner
1 - 20 of 24 Posts

·
Registered
Joined
·
469 Posts
Discussion Starter · #1 · (Edited)
I have recently changed the exhaust system to a dual exit 3 inch system from downpipe till the exits at the silencers and all parts are custom made in Turkey except the end tail pipes. Photos waiting for a nice weather and lift :lol:.

Other mods are K&N filter, 3.5 FPR supplied from Nordic together with their stage 3 ECU. So everything is as Nordic has described for a stage 3, if not better due to full 3 inch system. IC is the next mode.

For few days I experienced serious missfire and CEL light warning. Speaking to Dr. Phill, I found out that turbo valve bypass return pipe was loose and no CEL warning so far after 20 km of driving even though cat is cancelled. The only thing we did with the second sensor was fitting into a 5 cm tube and fix it to to the back of the original location of the sensor. Well, now there'd no CEL and rev up is with no problems but rev down still creates backfires. What else should I look at? Would upgrading to NGK8's help? I have an mp4 in car video so I can email to if anyone is interested to listen to give me a diagnostic.

Sound of the custom made exhaust is very sporty but also loud in the car especially around 3000 rpm. So I will include a central silencer as now I only have 2 silencers at the back. And the question is related with pipe radius at silencers. Someone told that we need less radius at pipes in the silencers because we need backpressure for lower rpms. Another guy told that it will be killing such a nice 3 inch system and turbo engines don't need backpressure.

So can you please comment here? And if we need a lower radius, can I just do this at the central silencer that I will apply? Any ideas on what the radius should be?

Finally, what acceleration intervals should I expect from Nordic stage 3 to make sure if I'm there. I'm looking for 50-100, 100-150, 100-200 kind of information. Please send whether it is metric or not, no problem, I can convert myself.
 

·
Registered
Joined
·
3,597 Posts
Turbocharged cars ideally have no backpressure. The turbocharger itself creates as much backpressure as it needs to get boost, and after that it doesn't really matter. If you have any additional backpressure, you will just make it harder for the turbo to achieve it's desired pressure.

If you are having a popping sound from the exhaust, you need a center resonator. These absorb most of the gurgle and pop in an exhaust system.

A drone at 3000rpm doesn't sound ideal, especially considering that's where you will be on the highway. Unfortunately reducing this may require different mufflers or some sort of silencer tips.
 

·
Registered
Joined
·
1,176 Posts
From talking with a couple exhaust experts, every car needs some sort of backpressure. All I know is that I ran my car with no exhaust for awhile, Stage III with an open downpipe. When I put the exhaust back on there was HUGE difference. Felt like 25+ more torque. Car pulled MUCH harder.
 

·
Registered
Joined
·
4,845 Posts
stipud said:
Turbocharged cars ideally have no backpressure. The turbocharger itself creates as much backpressure as it needs to get boost, and after that it doesn't really matter. If you have any additional backpressure, you will just make it harder for the turbo to achieve it's desired pressure.

If you are having a popping sound from the exhaust, you need a center resonator. These absorb most of the gurgle and pop in an exhaust system.

A drone at 3000rpm doesn't sound ideal, especially considering that's where you will be on the highway. Unfortunately reducing this may require different mufflers or some sort of silencer tips.
That actually isn't EXACTLY true, but the idea is correct.

The turbo does create back pressure which helps the engine evacuate exhaust gasses, but you will loose spool performance if there is absolutely 0 backpressure after the turbo. Ideally, you want the air to evacuate the cylinders as fast as possible all the way through the turbo and a little past it.

This is because when air pressure drops the temperature does as well which causes the air to become denser and slower, which in turn slows the entire process behind it down. This isn't as big of a deal later in the exhaust since it has a much less direct effect on the engine.

So picture this, you have very hot, light air flowing out of the manifold at a high rate of speed and then into the turbo, but once it gets out of the turbo and hits that 3" downpipe without any restriction, the air will cool VERY rapidly due to no pressure in the downpipe and the increase in size effectively causing the air to slow dramatically. This happening right after the turbo will cause somewhat of a traffic jam, and can really hinder your performance. Some car companies will actually put a catalytic converter before, and almost immediately after the turbo to keep the air very hot and flowing quickly. You really have to do a lot of tests on a car if your going to go straight pipes, and the reason you see race cars not having any mufflers or cat's and are getting away with it is because a) they size their pipes according to their use and b) their use is strictly racing and very HOT performance which in turn keeps the perfectly sized straight pipes hot, and keeping the flow rate up. Warm up laps are there for many reasons! ;)

This is a very good example of why to try to stick to performance parts that have proven themselves over and over. You really don't want to have your 9-5 be only good when your high in revs.

What kind of downpipe do you have? Does it have a catalytic converter? Having that center silencer (stay 3") may still help quite a bit as it may be close enough to the turbo to keep the air flowing faster.

Cambio said:
From talking with a couple exhaust experts, every car needs some sort of backpressure. All I know is that I ran my car with no exhaust for awhile, Stage III with an open downpipe. When I put the exhaust back on there was HUGE difference. Felt like 25+ more torque. Car pulled MUCH harder.
This happened to a very good buddy of mine with an exhaust leak. Same exact thing happened. It's impressive what the slightest thing can do, really.
 

·
Registered
Joined
·
469 Posts
Discussion Starter · #5 · (Edited)
http://www.youtube.com/watch?v=bId5AKYcPzY


Here is the link to the video. Sound of the backfire is not that clear anymore though after uploading to youtube.

I just had to edit my message as SectorNine50 and I have added a mesaage at the same time. Very interesting comments, thanks all.

I will post how my downpipe looks but it is without cat and the rest is done looking at other examples on the web and there's limited space for making a design change anyway. The only weakness can be where it is connected at the top so I will post a photo soon for experts. I had to go the custom way as it would have cost twice as much to import the system.

SectorNine50, I understand that you advice a central silencer (is it the samething as resonator?) and continue 3 inch. In this case where do I need to have lower radius for backpressure if it is necessary and is it 2 or 2.5 inch that I should be looking at. Even though I have twin exit, most of the smoke still comes from one side and the other starts doing the job at higher revs.

Also please let me know about your views on sparkplug and what I should expect as acceleration figures.
 

·
Registered
Joined
·
809 Posts
Usually the answers are quite simple-the low backpressure issue looks too sophisticated for me to be true in that case.
Throttle body ,CPS,vacuum leak or O2 sensor looks more possible.
Local baby-ricers run Puntos,Hondas and all GSI&GTI junk with custom exhausts,retrofited turbos and without cats with no performance problem in short lives of their cars even with exhausts big enough to walk inside.:cool:
 

·
Registered
Joined
·
277 Posts
Why do I constantly read Missfire's with Nordic Software?

I run a 2.0t Nordic Extreem (340HP) and I have Missfire's............
Chris run's on Nordic and had also Missfire's.............
Now you came in this Topic with Missfire's with Nordic....................
I am a little worried about Nordic or am I wrong? (I sure hope so!)
I still have them and I am not ammused with it I changed about everything
or looked and thightend all tubes hoses etc etc but still Miss........:evil: !

So what do you guys think of it?

Gr EJ
 

·
Registered
Joined
·
22,211 Posts
Trollspeed said:
So what do you guys think of it?

Gr EJ
My missfire was the CPS - nothing to do with Nordic :nono;

Would a stock car see the same conditions, probably yes......

In this thread its the "turbo bypass valve" according to the writer - again a hardware or instal problem :confused:
 

·
Registered
Joined
·
277 Posts
Oke chris I will go tomorrow change my CPS, had no time to get it in yet but I want to know ( my wife will not be pleased with it i think.......;) )
I hope it is the CPS Chris.... I let know..........
Gr EJ
 

·
Registered
Joined
·
469 Posts
Discussion Starter · #10 ·
After some search on relationship between turbo engines and back pressure, I found this article is very interesting.

http://www.northwestnissans.com/board/showthread.php?t=40455http://www.northwestnissans.com/boa...ead.php?t=40455

In short, back pressure is not something to worry for turbo engines. What you have to make sure to have a quality DP with as much as less sharp bends and very smooth connections inside after welding. It is also important to have as much less bend as possible for the rest of the exhaust system. And for size after cat, 300ZX performed better at low and mid range with 2.5" and top end gains were minimal at top end. The theory is that cooling exhaust gas is flowing out more difficult at the back of the exhaust system.

By the way, I'm wondering why no one (except Dr. Phill's PM - thanks) comments on BCR8ES as well as acceleration results with stage III form Nordic.
 

·
Registered
Joined
·
22,211 Posts
Turkish Aerolines said:
comments on BCR8ES as well as acceleration results with stage III form Nordic.
I tried the 8's and the thing kept stalling :roll:

7's have always been fine though......
 

·
Registered
Joined
·
469 Posts
Discussion Starter · #12 ·
Chris 9-5 said:
In this thread its the "turbo bypass valve" according to the writer - again a hardware or instal problem :confused:
After fixing the bypass valve piping, I've got rid of the CEL. But missfire continues, even though not as terrible as previous. But still there.

Next week I will swap it with original ECU as I still have it. Would the original ECU work OK with 3.5 FPR or should I also replace it with original to see if missfire is gone?
 

·
Registered
Joined
·
809 Posts
I also run Nordic as you knows and my hardware is quite different from this required for stage 3.
With T5 cams,3" no cat downpipe,progressive FPR set to base of 3.4 Bar I have no problems for 6-7000 km with that stage/and hope that I wouldn't/.
Sometime new and especially higher stages make obvious problems which will stay hidden longer in "normal"car.
It is always better to stay for couple of dino runs in tuner shop after installing something new and ask for custom software,but it is very-very expensive to be done here , I have to drive to Sweden every 6 month for my new toys.
I'm not the Nordic fanatic,will try Maptun one day for sure,but I don't think that it is possible to appear some kind of common software weakness.
They are old ,famous and respective Saab tuner for long years and I'm sure that they work hard to keep their positions.

PS.But why they make Christmas discount now only if you go to Norrköping Sweden-is it fair?
NO!:evil:
 

·
Registered
Joined
·
22,211 Posts
DoctorPhill said:
PS.But why they make Christmas discount now only if you go to Norrköping Sweden-is it fair?
NO!:evil:
Yes its fair, its their own profits, if they tried to offer this world wide the independent dealers would suffer as the core product has not been discounted to the International dealers.

Regarding some of these hardware failures, well we really should expect that...... Saab will have tested the stock components, but with much lower power levels. Tuning the car will highlight the weaknesses quicker I guess.
 

·
Registered
Joined
·
22,211 Posts
Turkish Aerolines said:
Would the idle be still stable if CPS is faulty? In my case, idle is pretty stable.
My car was perfect.......smooth at idle all the way up to about 4500rpm, then............bam! The misfire (sensor going blind) was so extreme the seat belt would cut into your shoulder :eek:
 

·
Registered
Joined
·
469 Posts
Discussion Starter · #18 ·
Chris, did you have a chance to look at the video at youtube. In my case revving up to redline shows no problems (video is at parking lot so no load but also no problem while driving). I hear the missfires when revving down. It is more noticable at original video compared to what you will hear at youtube though.

My best option is to see the situation with the original ECU but I still need opinion if original ECU is OK to work with 3.5 bar FPR.

Dr. Phill mentioned about progressive FPR. I couldn't find more info on net by search or an internet supplier. Any links?
 

·
Registered
Joined
·
22,211 Posts
Turkish Aerolines said:
. I hear the missfires when revving down. It is more noticable at original video compared to what you will hear at youtube though.
I think you are hearing unburnt fuel popping in the un restricted exhaust :confused:

You can run the original ECU on the 3.5 bar FPR temporarily, but I bet when that exhaust is red hot you get the same sounds :confused:
 
1 - 20 of 24 Posts
Top